mm: memcontrol: remove trailing semicolon in macros

Macros should not use a trailing semicolon.

Link: https://lkml.kernel.org/r/20210614091530.22117-1-denghuilong@cdjrlc.com
Signed-off-by: Huilong Deng <denghuilong@cdjrlc.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

loop: charge i/o to mem and blk cg

The current code only associates with the existing blkcg when aio is used
to access the backing file.  This patch covers all types of i/o to the
backing file and also associates the memcg so if the backing file is on
tmpfs, memory is charged appropriately.

This patch also exports cgroup_get_e_css and int_active_memcg so it can be
used by the loop module.

Link: https://lkml.kernel.org/r/20210610173944.1203706-4-schatzberg.dan@gmail.com
Signed-off-by: Dan Schatzberg <schatzberg.dan@gmail.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Jens Axboe <axboe@kernel.dk>
Cc: Chris Down <chris@chrisdown.name>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: charge active memcg when no mm is set

set_active_memcg() worked for kernel allocations but was silently ignored
for user pages.

This patch establishes a precedence order for who gets charged:

1. If there is a memcg associated with the page already, that memcg is
   charged. This happens during swapin.

2. If an explicit mm is passed, mm->memcg is charged. This happens
   during page faults, which can be triggered in remote VMs (eg gup).

3. Otherwise consult the current process context. If there is an
   active_memcg, use that. Otherwise, current->mm->memcg.

Previously, if a NULL mm was passed to mem_cgroup_charge (case 3) it would
always charge the root cgroup.  Now it looks up the active_memcg first
(falling back to charging the root cgroup if not set).

Link: https://lkml.kernel.org/r/20210610173944.1203706-3-schatzberg.dan@gmail.com
Signed-off-by: Dan Schatzberg <schatzberg.dan@gmail.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: Chris Down <chris@chrisdown.name>
Acked-by: Jens Axboe <axboe@kernel.dk>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Reviewed-by: Michal Koutný <mkoutny@suse.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

loop: use worker per cgroup instead of kworker

Patch series "Charge loop device i/o to issuing cgroup", v14.

The loop device runs all i/o to the backing file on a separate kworker
thread which results in all i/o being charged to the root cgroup.  This
allows a loop device to be used to trivially bypass resource limits and
other policy.  This patch series fixes this gap in accounting.

A simple script to demonstrate this behavior on cgroupv2 machine:

'''
#!/bin/bash
set -e

CGROUP=/sys/fs/cgroup/test.slice
LOOP_DEV=/dev/loop0

if [[ ! -d $CGROUP ]]
then
    sudo mkdir $CGROUP
fi

grep oom_kill $CGROUP/memory.events

# Set a memory limit, write more than that limit to tmpfs -> OOM kill
sudo unshare -m bash -c "
echo \$\$ > $CGROUP/cgroup.procs;
echo 0 > $CGROUP/memory.swap.max;
echo 64M > $CGROUP/memory.max;
mount -t tmpfs -o size=512m tmpfs /tmp;
dd if=/dev/zero of=/tmp/file bs=1M count=256" || true

grep oom_kill $CGROUP/memory.events

# Set a memory limit, write more than that limit through loopback
# device -> no OOM kill
sudo unshare -m bash -c "
echo \$\$ > $CGROUP/cgroup.procs;
echo 0 > $CGROUP/memory.swap.max;
echo 64M > $CGROUP/memory.max;
mount -t tmpfs -o size=512m tmpfs /tmp;
truncate -s 512m /tmp/backing_file
losetup $LOOP_DEV /tmp/backing_file
dd if=/dev/zero of=$LOOP_DEV bs=1M count=256;
losetup -D $LOOP_DEV" || true

grep oom_kill $CGROUP/memory.events
'''

Naively charging cgroups could result in priority inversions through the
single kworker thread in the case where multiple cgroups are
reading/writing to the same loop device.  This patch series does some
minor modification to the loop driver so that each cgroup can make forward
progress independently to avoid this inversion.

With this patch series applied, the above script triggers OOM kills when
writing through the loop device as expected.

This patch (of 3):

Existing uses of loop device may have multiple cgroups reading/writing to
the same device.  Simply charging resources for I/O to the backing file
could result in priority inversion where one cgroup gets synchronously
blocked, holding up all other I/O to the loop device.

In order to avoid this priority inversion, we use a single workqueue where
each work item is a "struct loop_worker" which contains a queue of struct
loop_cmds to issue.  The loop device maintains a tree mapping blk css_id
-> loop_worker.  This allows each cgroup to independently make forward
progress issuing I/O to the backing file.

There is also a single queue for I/O associated with the rootcg which can
be used in cases of extreme memory shortage where we cannot allocate a
loop_worker.

The locking for the tree and queues is fairly heavy handed - we acquire a
per-loop-device spinlock any time either is accessed.  The existing
implementation serializes all I/O through a single thread anyways, so I
don't believe this is any worse.

[colin.king@canonical.com: fixes]

Link: https://lkml.kernel.org/r/20210610173944.1203706-1-schatzberg.dan@gmail.com
Link: https://lkml.kernel.org/r/20210610173944.1203706-2-schatzberg.dan@gmail.com
Signed-off-by: Dan Schatzberg <schatzberg.dan@gmail.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Acked-by: Jens Axboe <axboe@kernel.dk>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Chris Down <chris@chrisdown.name>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

memcontrol: use flexible-array member

Change deprecated zero-length-and-one-element-arrays into flexible array
member.Zero-length and one-element arrays detected by Lukas's CodeChecker.
Zero/one element arrays cause undefined behaviours if sizeof() used.

Link: https://lkml.kernel.org/r/20210518200910.29912-1-wenhui@gwmail.gwu.edu
Signed-off-by: wenhuizhang <wenhui@gwmail.gwu.edu>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Roman Gushchin <guro@fb.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Alex Shi <alexs@kernel.org>
Cc: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Cc: Wei Yang <richard.weiyang@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: vmscan: remove noinline_for_stack

The noinline_for_stack is introduced by commit 666356297ec4 ("vmscan: set
up pagevec as late as possible in shrink_inactive_list()"), its purpose is
to delay the allocation of pagevec as late as possible to save stack
memory.  But the commit 2bcf88796381 ("mm: take pagevecs off reclaim
stack") replace pagevecs by lists of pages_to_free.  So we do not need
noinline_for_stack, just remove it (let the compiler decide whether to
inline).

Link: https://lkml.kernel.org/r/20210417043538.9793-9-songmuchun@bytedance.com
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Roman Gushchin <guro@fb.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Xiongchun Duan <duanxiongchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: memcontrol: move obj_cgroup_uncharge_pages() out of css_set_lock

The css_set_lock is used to guard the list of inherited objcgs.  So there
is no need to uncharge kernel memory under css_set_lock.  Just move it out
of the lock.

Link: https://lkml.kernel.org/r/20210417043538.9793-8-songmuchun@bytedance.com
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Roman Gushchin <guro@fb.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Xiongchun Duan <duanxiongchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: memcontrol: simplify the logic of objcg pinning memcg

The obj_cgroup_release() and memcg_reparent_objcgs() are serialized by the
css_set_lock.  We do not need to care about objcg->memcg being released in
the process of obj_cgroup_release().  So there is no need to pin memcg
before releasing objcg.  Remove those pinning logic to simplfy the code.

There are only two places that modifies the objcg->memcg.  One is the
initialization to objcg->memcg in the memcg_online_kmem(), another is
objcgs reparenting in the memcg_reparent_objcgs().  It is also impossible
for the two to run in parallel.  So xchg() is unnecessary and it is enough
to use WRITE_ONCE().

Link: https://lkml.kernel.org/r/20210417043538.9793-7-songmuchun@bytedance.com
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Roman Gushchin <guro@fb.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Xiongchun Duan <duanxiongchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: memcontrol: rename lruvec_holds_page_lru_lock to page_matches_lruvec

lruvec_holds_page_lru_lock() doesn't check anything about locking and is
used to check whether the page belongs to the lruvec.  So rename it to
page_matches_lruvec().

Link: https://lkml.kernel.org/r/20210417043538.9793-6-songmuchun@bytedance.com
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Xiongchun Duan <duanxiongchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: memcontrol: simplify lruvec_holds_page_lru_lock

We already have a helper lruvec_memcg() to get the memcg from lruvec, we
do not need to do it ourselves in the lruvec_holds_page_lru_lock().  So
use lruvec_memcg() instead.  And if mem_cgroup_disabled() returns false,
the page_memcg(page) (the LRU pages) cannot be NULL.  So remove the odd
logic of "memcg = page_memcg(page) ?  : root_mem_cgroup".  And use
lruvec_pgdat to simplify the code.  We can have a single definition for
this function that works for !CONFIG_MEMCG, CONFIG_MEMCG +
mem_cgroup_disabled() and CONFIG_MEMCG.

Link: https://lkml.kernel.org/r/20210417043538.9793-5-songmuchun@bytedance.com
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Roman Gushchin <guro@fb.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Xiongchun Duan <duanxiongchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: memcontrol: remove the pgdata parameter of mem_cgroup_page_lruvec

All the callers of mem_cgroup_page_lruvec() just pass page_pgdat(page) as
the 2nd parameter to it (except isolate_migratepages_block()).  But for
isolate_migratepages_block(), the page_pgdat(page) is also equal to the
local variable of @pgdat.  So mem_cgroup_page_lruvec() do not need the
pgdat parameter.  Just remove it to simplify the code.

Link: https://lkml.kernel.org/r/20210417043538.9793-4-songmuchun@bytedance.com
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Roman Gushchin <guro@fb.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Xiongchun Duan <duanxiongchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: memcontrol: bail out early when !mm in get_mem_cgroup_from_mm

When mm is NULL, we do not need to hold rcu lock and call css_tryget for
the root memcg.  And we also do not need to check !mm in every loop of
while.  So bail out early when !mm.

Link: https://lkml.kernel.org/r/20210417043538.9793-3-songmuchun@bytedance.com
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Roman Gushchin <guro@fb.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Xiongchun Duan <duanxiongchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: memcontrol: fix page charging in page replacement

Patch series "memcontrol code cleanup and simplification", v3.

This patch (of 8):

The pages aren't accounted at the root level, so do not charge the page to
the root memcg in page replacement.  Although we do not display the value
(mem_cgroup_usage) so there shouldn't be any actual problem, but there is
a WARN_ON_ONCE in the page_counter_cancel().  Who knows if it will
trigger?  So it is better to fix it.

Link: https://lkml.kernel.org/r/20210417043538.9793-1-songmuchun@bytedance.com
Link: https://lkml.kernel.org/r/20210417043538.9793-2-songmuchun@bytedance.com
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Roman Gushchin <guro@fb.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Xiongchun Duan <duanxiongchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: memcontrol: fix root_mem_cgroup charging

The below scenario can cause the page counters of the root_mem_cgroup to
be out of balance.

CPU0:                                   CPU1:

objcg = get_obj_cgroup_from_current()
obj_cgroup_charge_pages(objcg)
                                        memcg_reparent_objcgs()
                                            // reparent to root_mem_cgroup
                                            WRITE_ONCE(iter->memcg, parent)
    // memcg == root_mem_cgroup
    memcg = get_mem_cgroup_from_objcg(objcg)
    // do not charge to the root_mem_cgroup
    try_charge(memcg)

obj_cgroup_uncharge_pages(objcg)
    memcg = get_mem_cgroup_from_objcg(objcg)
    // uncharge from the root_mem_cgroup
    refill_stock(memcg)
        drain_stock(memcg)
            page_counter_uncharge(&memcg->memory)

get_obj_cgroup_from_current() never returns a root_mem_cgroup's objcg, so
we never explicitly charge the root_mem_cgroup.  And it's not going to
change.  It's all about a race when we got an obj_cgroup pointing at some
non-root memcg, but before we were able to charge it, the cgroup was gone,
objcg was reparented to the root and so we're skipping the charging.  Then
we store the objcg pointer and later use to uncharge the root_mem_cgroup.

This can cause the page counter to be less than the actual value.
Although we do not display the value (mem_cgroup_usage) so there shouldn't
be any actual problem, but there is a WARN_ON_ONCE in the
page_counter_cancel().  Who knows if it will trigger?  So it is better to
fix it.

Link: https://lkml.kernel.org/r/20210425075410.19255-1-songmuchun@bytedance.com
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: Roman Gushchin <guro@fb.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Cc: Xiongchun Duan <duanxiongchun@bytedance.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: memcg/slab: disable cache merging for KMALLOC_NORMAL caches

The KMALLOC_NORMAL (kmalloc-<n>) caches are for unaccounted objects only
when CONFIG_MEMCG_KMEM is enabled.  To make sure that this condition
remains true, we will have to prevent KMALOC_NORMAL caches to merge with
other kmem caches.  This is now done by setting its refcount to -1 right
after its creation.

Link: https://lkml.kernel.org/r/20210505200610.13943-4-longman@redhat.com
Signed-off-by: Waiman Long <longman@redhat.com>
Suggested-by: Roman Gushchin <guro@fb.com>
Acked-by: Roman Gushchin <guro@fb.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: memcg/slab: create a new set of kmalloc-cg-<n> caches

There are currently two problems in the way the objcg pointer array
(memcg_data) in the page structure is being allocated and freed.

On its allocation, it is possible that the allocated objcg pointer
array comes from the same slab that requires memory accounting. If this
happens, the slab will never become empty again as there is at least
one object left (the obj_cgroup array) in the slab.

When it is freed, the objcg pointer array object may be the last one
in its slab and hence causes kfree() to be called again. With the
right workload, the slab cache may be set up in a way that allows the
recursive kfree() calling loop to nest deep enough to cause a kernel
stack overflow and panic the system.

One way to solve this problem is to split the kmalloc-<n> caches
(KMALLOC_NORMAL) into two separate sets - a new set of kmalloc-<n>
(KMALLOC_NORMAL) caches for unaccounted objects only and a new set of
kmalloc-cg-<n> (KMALLOC_CGROUP) caches for accounted objects only. All
the other caches can still allow a mix of accounted and unaccounted
objects.

With this change, all the objcg pointer array objects will come from
KMALLOC_NORMAL caches which won't have their objcg pointer arrays. So
both the recursive kfree() problem and non-freeable slab problem are
gone.

Since both the KMALLOC_NORMAL and KMALLOC_CGROUP caches no longer have
mixed accounted and unaccounted objects, this will slightly reduce the
number of objcg pointer arrays that need to be allocated and save a bit
of memory. On the other hand, creating a new set of kmalloc caches does
have the effect of reducing cache utilization. So it is properly a wash.

The new KMALLOC_CGROUP is added between KMALLOC_NORMAL and
KMALLOC_RECLAIM so that the first for loop in create_kmalloc_caches()
will include the newly added caches without change.

[vbabka@suse.cz: don't create kmalloc-cg caches with cgroup.memory=nokmem]
Link: https://lkml.kernel.org/r/20210512145107.6208-1-longman@redhat.com
[akpm@linux-foundation.org: un-fat-finger v5 delta creation]
[longman@redhat.com: disable cache merging for KMALLOC_NORMAL caches]
Link: https://lkml.kernel.org/r/20210505200610.13943-4-longman@redhat.com
Link: https://lkml.kernel.org/r/20210512145107.6208-1-longman@redhat.com
Link: https://lkml.kernel.org/r/20210505200610.13943-3-longman@redhat.com
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Suggested-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Roman Gushchin <guro@fb.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
[longman@redhat.com: fix for CONFIG_ZONE_DMA=n]
Suggested-by: Roman Gushchin <guro@fb.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: memcg/slab: properly set up gfp flags for objcg pointer array

Patch series "mm: memcg/slab: Fix objcg pointer array handling problem", v4.

Since the merging of the new slab memory controller in v5.9, the page
structure stores a pointer to objcg pointer array for slab pages.  When
the slab has no used objects, it can be freed in free_slab() which will
call kfree() to free the objcg pointer array in
memcg_alloc_page_obj_cgroups().  If it happens that the objcg pointer
array is the last used object in its slab, that slab may then be freed
which may caused kfree() to be called again.

With the right workload, the slab cache may be set up in a way that allows
the recursive kfree() calling loop to nest deep enough to cause a kernel
stack overflow and panic the system.  In fact, we have a reproducer that
can cause kernel stack overflow on a s390 system involving kmalloc-rcl-256
and kmalloc-rcl-128 slabs with the following kfree() loop recursively
called 74 times:

  [ 285.520739] [<000000000ec432fc>] kfree+0x4bc/0x560 [ 285.520740]
[<000000000ec43466>] __free_slab+0xc6/0x228 [ 285.520741]
[<000000000ec41fc2>] __slab_free+0x3c2/0x3e0 [ 285.520742]
[<000000000ec432fc>] kfree+0x4bc/0x560 : While investigating this issue, I
also found an issue on the allocation side.  If the objcg pointer array
happen to come from the same slab or a circular dependency linkage is
formed with multiple slabs, those affected slabs can never be freed again.

This patch series addresses these two issues by introducing a new set of
kmalloc-cg-<n> caches split from kmalloc-<n> caches.  The new set will
only contain non-reclaimable and non-dma objects that are accounted in
memory cgroups whereas the old set are now for unaccounted objects only.
By making this split, all the objcg pointer arrays will come from the
kmalloc-<n> caches, but those caches will never hold any objcg pointer
array.  As a result, deeply nested kfree() call and the unfreeable slab
problems are now gone.

This patch (of 4):

Since the merging of the new slab memory controller in v5.9, the page
structure may store a pointer to obj_cgroup pointer array for slab pages.
Currently, only the __GFP_ACCOUNT bit is masked off.  However, the array
is not readily reclaimable and doesn't need to come from the DMA buffer.
So those GFP bits should be masked off as well.

Do the flag bit clearing at memcg_alloc_page_obj_cgroups() to make sure
that it is consistently applied no matter where it is called.

Link: https://lkml.kernel.org/r/20210505200610.13943-1-longman@redhat.com
Link: https://lkml.kernel.org/r/20210505200610.13943-2-longman@redhat.com
Fixes: 286e04b8ed7a ("mm: memcg/slab: allocate obj_cgroups for non-root slab pages")
Signed-off-by: Waiman Long <longman@redhat.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Roman Gushchin <guro@fb.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/memcg: optimize user context object stock access

Most kmem_cache_alloc() calls are from user context.  With instrumentation
enabled, the measured amount of kmem_cache_alloc() calls from non-task
context was about 0.01% of the total.

The irq disable/enable sequence used in this case to access content from
object stock is slow.  To optimize for user context access, there are now
two sets of object stocks (in the new obj_stock structure) for task
context and interrupt context access respectively.

The task context object stock can be accessed after disabling preemption
which is cheap in non-preempt kernel.  The interrupt context object stock
can only be accessed after disabling interrupt.  User context code can
access interrupt object stock, but not vice versa.

The downside of this change is that there are more data stored in local
object stocks and not reflected in the charge counter and the vmstat
arrays.  However, this is a small price to pay for better performance.

[longman@redhat.com: fix potential uninitialized variable warning]
Link: https://lkml.kernel.org/r/20210526193602.8742-1-longman@redhat.com
[akpm@linux-foundation.org: coding style fixes]

Link: https://lkml.kernel.org/r/20210506150007.16288-5-longman@redhat.com
Signed-off-by: Waiman Long <longman@redhat.com>
Acked-by: Roman Gushchin <guro@fb.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Roman Gushchin <guro@fb.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Alex Shi <alex.shi@linux.alibaba.com>
Cc: Chris Down <chris@chrisdown.name>
Cc: Yafang Shao <laoar.shao@gmail.com>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Masayoshi Mizuma <msys.mizuma@gmail.com>
Cc: Xing Zhengjun <zhengjun.xing@linux.intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/memcg: improve refill_obj_stock() performance

There are two issues with the current refill_obj_stock() code.  First of
all, when nr_bytes reaches over PAGE_SIZE, it calls drain_obj_stock() to
atomically flush out remaining bytes to obj_cgroup, clear cached_objcg and
do a obj_cgroup_put().  It is likely that the same obj_cgroup will be used
again which leads to another call to drain_obj_stock() and
obj_cgroup_get() as well as atomically retrieve the available byte from
obj_cgroup.  That is costly.  Instead, we should just uncharge the excess
pages, reduce the stock bytes and be done with it.  The drain_obj_stock()
function should only be called when obj_cgroup changes.

Secondly, when charging an object of size not less than a page in
obj_cgroup_charge(), it is possible that the remaining bytes to be
refilled to the stock will overflow a page and cause refill_obj_stock() to
uncharge 1 page.  To avoid the additional uncharge in this case, a new
allow_uncharge flag is added to refill_obj_stock() which will be set to
false when called from obj_cgroup_charge() so that an uncharge_pages()
call won't be issued right after a charge_pages() call unless the objcg
changes.

A multithreaded kmalloc+kfree microbenchmark on a 2-socket 48-core
96-thread x86-64 system with 96 testing threads were run.  Before this
patch, the total number of kilo kmalloc+kfree operations done for a 4k
large object by all the testing threads per second were 4,304 kops/s
(cgroup v1) and 8,478 kops/s (cgroup v2).  After applying this patch, the
number were 4,731 (cgroup v1) and 418,142 (cgroup v2) respectively.  This
represents a performance improvement of 1.10X (cgroup v1) and 49.3X
(cgroup v2).

Link: https://lkml.kernel.org/r/20210506150007.16288-4-longman@redhat.com
Signed-off-by: Waiman Long <longman@redhat.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Cc: Alex Shi <alex.shi@linux.alibaba.com>
Cc: Chris Down <chris@chrisdown.name>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Masayoshi Mizuma <msys.mizuma@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Roman Gushchin <guro@fb.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Xing Zhengjun <zhengjun.xing@linux.intel.com>
Cc: Yafang Shao <laoar.shao@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/memcg: cache vmstat data in percpu memcg_stock_pcp

Before the new slab memory controller with per object byte charging,
charging and vmstat data update happen only when new slab pages are
allocated or freed.  Now they are done with every kmem_cache_alloc() and
kmem_cache_free().  This causes additional overhead for workloads that
generate a lot of alloc and free calls.

The memcg_stock_pcp is used to cache byte charge for a specific obj_cgroup
to reduce that overhead.  To further reducing it, this patch makes the
vmstat data cached in the memcg_stock_pcp structure as well until it
accumulates a page size worth of update or when other cached data change.
Caching the vmstat data in the per-cpu stock eliminates two writes to
non-hot cachelines for memcg specific as well as memcg-lruvecs specific
vmstat data by a write to a hot local stock cacheline.

On a 2-socket Cascade Lake server with instrumentation enabled and this
patch applied, it was found that about 20% (634400 out of 3243830) of the
time when mod_objcg_state() is called leads to an actual call to
__mod_objcg_state() after initial boot.  When doing parallel kernel build,
the figure was about 17% (24329265 out of 142512465).  So caching the
vmstat data reduces the number of calls to __mod_objcg_state() by more
than 80%.

Link: https://lkml.kernel.org/r/20210506150007.16288-3-longman@redhat.com
Signed-off-by: Waiman Long <longman@redhat.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Cc: Alex Shi <alex.shi@linux.alibaba.com>
Cc: Chris Down <chris@chrisdown.name>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Masayoshi Mizuma <msys.mizuma@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Roman Gushchin <guro@fb.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Xing Zhengjun <zhengjun.xing@linux.intel.com>
Cc: Yafang Shao <laoar.shao@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/memcg: move mod_objcg_state() to memcontrol.c

Patch series "mm/memcg: Reduce kmemcache memory accounting overhead", v6.

With the recent introduction of the new slab memory controller, we
eliminate the need for having separate kmemcaches for each memory cgroup
and reduce overall kernel memory usage.  However, we also add additional
memory accounting overhead to each call of kmem_cache_alloc() and
kmem_cache_free().

For workloads that require a lot of kmemcache allocations and
de-allocations, they may experience performance regression as illustrated
in [1] and [2].

A simple kernel module that performs repeated loop of 100,000,000
kmem_cache_alloc() and kmem_cache_free() of either a small 32-byte object
or a big 4k object at module init time with a batch size of 4 (4 kmalloc's
followed by 4 kfree's) is used for benchmarking.  The benchmarking tool
was run on a kernel based on linux-next-20210419.  The test was run on a
CascadeLake server with turbo-boosting disable to reduce run-to-run
variation.

The small object test exercises mainly the object stock charging and
vmstat update code paths.  The large object test also exercises the
refill_obj_stock() and __memcg_kmem_charge()/__memcg_kmem_uncharge() code
paths.

With memory accounting disabled, the run time was 3.130s with both small
object big object tests.

With memory accounting enabled, both cgroup v1 and v2 showed similar
results in the small object test.  The performance results of the large
object test, however, differed between cgroup v1 and v2.

The execution times with the application of various patches in the
patchset were:

  Applied patches   Run time   Accounting overhead   %age 1   %age 2
  ---------------   --------   -------------------   ------   ------

  Small 32-byte object:
       None          11.634s         8.504s          100.0%   271.7%
        1-2           9.425s         6.295s           74.0%   201.1%
        1-3           9.708s         6.578s           77.4%   210.2%
        1-4           8.062s         4.932s           58.0%   157.6%

  Large 4k object (v2):
       None          22.107s        18.977s          100.0%   606.3%
        1-2          20.960s        17.830s           94.0%   569.6%
        1-3          14.238s        11.108s           58.5%   354.9%
        1-4          11.329s         8.199s           43.2%   261.9%

  Large 4k object (v1):
       None          36.807s        33.677s          100.0%  1075.9%
        1-2          36.648s        33.518s           99.5%  1070.9%
        1-3          22.345s        19.215s           57.1%   613.9%
        1-4          18.662s        15.532s           46.1%   496.2%

  N.B. %age 1 = overhead/unpatched overhead
       %age 2 = overhead/accounting disabled time

Patch 2 (vmstat data stock caching) helps in both the small object test
and the large v2 object test. It doesn't help much in v1 big object test.

Patch 3 (refill_obj_stock improvement) does help the small object test
but offer significant performance improvement for the large object test
(both v1 and v2).

Patch 4 (eliminating irq disable/enable) helps in all test cases.

To test for the extreme case, a multi-threaded kmalloc/kfree
microbenchmark was run on the 2-socket 48-core 96-thread system with
96 testing threads in the same memcg doing kmalloc+kfree of a 4k object
with accounting enabled for 10s. The total number of kmalloc+kfree done
in kilo operations per second (kops/s) were as follows:

  Applied patches   v1 kops/s   v1 change   v2 kops/s   v2 change
  ---------------   ---------   ---------   ---------   ---------
       None           3,520        1.00X      6,242        1.00X
        1-2           4,304        1.22X      8,478        1.36X
        1-3           4,731        1.34X    418,142       66.99X
        1-4           4,587        1.30X    438,838       70.30X

With memory accounting disabled, the kmalloc/kfree rate was 1,481,291
kop/s. This test shows how significant the memory accouting overhead
can be in some extreme situations.

For this multithreaded test, the improvement from patch 2 mainly
comes from the conditional atomic xchg of objcg->nr_charged_bytes in
mod_objcg_state(). By using an unconditional xchg, the operation rates
were similar to the unpatched kernel.

Patch 3 elminates the single highly contended cacheline of
objcg->nr_charged_bytes for cgroup v2 leading to a huge performance
improvement. Cgroup v1, however, still has another highly contended
cacheline in the shared page counter &memcg->kmem. So the improvement
is only modest.

Patch 4 helps in cgroup v2, but performs worse in cgroup v1 as
eliminating the irq_disable/irq_enable overhead seems to aggravate the
cacheline contention.

[1] https://lore.kernel.org/linux-mm/20210408193948.vfktg3azh2wrt56t@gabell/T/#u
[2] https://lore.kernel.org/lkml/20210114025151.GA22932@xsang-OptiPlex-9020/

This patch (of 4):

mod_objcg_state() is moved from mm/slab.h to mm/memcontrol.c so that
further optimization can be done to it in later patches without exposing
unnecessary details to other mm components.

Link: https://lkml.kernel.org/r/20210506150007.16288-1-longman@redhat.com
Link: https://lkml.kernel.org/r/20210506150007.16288-2-longman@redhat.com
Signed-off-by: Waiman Long <longman@redhat.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Roman Gushchin <guro@fb.com>
Cc: Alex Shi <alex.shi@linux.alibaba.com>
Cc: Chris Down <chris@chrisdown.name>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Masayoshi Mizuma <msys.mizuma@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Xing Zhengjun <zhengjun.xing@linux.intel.com>
Cc: Yafang Shao <laoar.shao@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

swap: check mapping_empty() for swap cache before being freed

To check whether all pages and shadow entries in swap cache has been
removed before swap cache is freed.

Link: https://lkml.kernel.org/r/20210608005121.511140-1-ying.huang@intel.com
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Hugh Dickins <hughd@google.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: free idle swap cache page after COW

With commit 09854ba94c6a ("mm: do_wp_page() simplification"), after COW,
the idle swap cache page (neither the page nor the corresponding swap
entry is mapped by any process) will be left in the LRU list, even if it's
in the active list or the head of the inactive list.  So, the page
reclaimer may take quite some overhead to reclaim these actually unused
pages.

To help the page reclaiming, in this patch, after COW, the idle swap cache
page will be tried to be freed.  To avoid to introduce much overhead to
the hot COW code path,

a) there's almost zero overhead for non-swap case via checking
   PageSwapCache() firstly.

b) the page lock is acquired via trylock only.

To test the patch, we used pmbench memory accessing benchmark with
working-set larger than available memory on a 2-socket Intel server with a
NVMe SSD as swap device.  Test results shows that the pmbench score
increases up to 23.8% with the decreased size of swap cache and swapin
throughput.

Link: https://lkml.kernel.org/r/20210601053143.1380078-1-ying.huang@intel.com
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Suggested-by: Johannes Weiner <hannes@cmpxchg.org> [use free_swap_cache()]
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@surriel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Tim Chen <tim.c.chen@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm, swap: remove unnecessary smp_rmb() in swap_type_to_swap_info()

Before commit c10d38cc8d3e ("mm, swap: bounds check swap_info array
accesses to avoid NULL derefs"), the typical code to reference the
swap_info[] is as follows,

  type = swp_type(swp_entry);
  if (type >= nr_swapfiles)
          /* handle invalid swp_entry */;
  p = swap_info[type];
  /* access fields of *p.  OOPS! p may be NULL! */

Because the ordering isn't guaranteed, it's possible that swap_info[type]
is read before "nr_swapfiles".  And that may result in NULL pointer
dereference.

So after commit c10d38cc8d3e, the code becomes,

  struct swap_info_struct *swap_type_to_swap_info(int type)
  {
  if (type >= READ_ONCE(nr_swapfiles))
  return NULL;
  smp_rmb();
  return READ_ONCE(swap_info[type]);
  }

  /* users */
  type = swp_type(swp_entry);
  p = swap_type_to_swap_info(type);
  if (!p)
  /* handle invalid swp_entry */;
  /* dereference p */

Where the value of swap_info[type] (that is, "p") is checked to be
non-zero before being dereferenced.  So, the NULL deferencing becomes
impossible even if "nr_swapfiles" is read after swap_info[type].
Therefore, the "smp_rmb()" becomes unnecessary.

And, we don't even need to read "nr_swapfiles" here.  Because the non-zero
checking for "p" is sufficient.  We just need to make sure we will not
access out of the boundary of the array.  With the change, nr_swapfiles
will only be accessed with swap_lock held, except in
swapcache_free_entries().  Where the absolute correctness of the value
isn't needed, as described in the comments.

We still need to guarantee swap_info[type] is read before being
dereferenced.  That can be satisfied via the data dependency ordering
enforced by READ_ONCE(swap_info[type]).  This needs to be paired with
proper write barriers.  So smp_store_release() is used in
alloc_swap_info() to guarantee the fields of *swap_info[type] is
initialized before swap_info[type] itself being written.  Note that the
fields of *swap_info[type] is initialized to be 0 via kvzalloc() firstly.
The assignment and deferencing of swap_info[type] is like
rcu_assign_pointer() and rcu_dereference().

Link: https://lkml.kernel.org/r/20210520073301.1676294-1-ying.huang@intel.com
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Cc: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Andrea Parri <andrea.parri@amarulasolutions.com>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Omar Sandoval <osandov@fb.com>
Cc: Paul McKenney <paulmck@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/swap_slots.c: delete meaningless forward declarations

deactivate_swap_slots_cache() and reactivate_swap_slots_cache() are only
called below their implementations.  So these forward declarations are
meaningless and should be removed.

Link: https://lkml.kernel.org/r/20210520134022.1370406-4-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/swap: remove unused local variable nr_shadows

Since commit 55c653b71e8c ("mm: stop accounting shadow entries"),
nr_shadows is not used anymore.

Link: https://lkml.kernel.org/r/20210520134022.1370406-3-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/swapfile: move get_swap_page_of_type() under CONFIG_HIBERNATION

Patch series "Cleanups for swap", v2.

This series contains just cleanups to remove some unused variables, delete
meaningless forward declarations and so on.  More details can be found in
the respective changelogs.

This patch (of 4):

We should move get_swap_page_of_type() under CONFIG_HIBERNATION since the
only caller of this function is now suspend routine.

[linmiaohe@huawei.com: move scan_swap_map() under CONFIG_HIBERNATION]
Link: https://lkml.kernel.org/r/20210521070855.2015094-1-linmiaohe@huawei.com
[linmiaohe@huawei.com: fold scan_swap_map() into the only caller get_swap_page_of_type()]
Link: https://lkml.kernel.org/r/20210527120328.3935132-1-linmiaohe@huawei.com
Link: https://lkml.kernel.org/r/20210520134022.1370406-1-linmiaohe@huawei.com
Link: https://lkml.kernel.org/r/20210520134022.1370406-2-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/shmem: fix shmem_swapin() race with swapoff

When I was investigating the swap code, I found the below possible race
window:

CPU 1                                         CPU 2
-----                                         -----
shmem_swapin
  swap_cluster_readahead
    if (likely(si->flags & (SWP_BLKDEV | SWP_FS_OPS))) {
                                              swapoff
                                                ..
                                                si->swap_file = NULL;
                                                ..
    struct inode *inode = si->swap_file->f_mapping->host;[oops!]

Close this race window by using get/put_swap_device() to guard against
concurrent swapoff.

Link: https://lkml.kernel.org/r/20210426123316.806267-5-linmiaohe@huawei.com
Fixes: 8fd2e0b505d1 ("mm: swap: check if swap backing device is congested or not")
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
Cc: Dennis Zhou <dennis@kernel.org>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Alex Shi <alexs@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/swap: remove confusing checking for non_swap_entry() in swap_ra_info()

The non_swap_entry() was used for working with VMA based swap readahead
via commit ec560175c0b6 ("mm, swap: VMA based swap readahead").  At that
time, the non_swap_entry() checking is necessary because the function is
called before checking that in do_swap_page().  Then it's moved to
swap_ra_info() since commit eaf649ebc3ac ("mm: swap: clean up swap
readahead").  After that, the non_swap_entry() checking is unnecessary,
because swap_ra_info() is called after non_swap_entry() has been checked
already.  The resulting code is confusing as the non_swap_entry() check
looks racy now because while we released the pte lock, somebody else might
have faulted in this pte.  So we should check whether it's swap pte first
to guard against such race or swap_type will be unexpected.  But the race
isn't important because it will not cause problem.  We would have enough
checking when we really operate the PTE entries later.  So we remove the
non_swap_entry() check here to avoid confusion.

Link: https://lkml.kernel.org/r/20210426123316.806267-4-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
Cc: Alex Shi <alexs@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Dennis Zhou <dennis@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

swap: fix do_swap_page() race with swapoff

When I was investigating the swap code, I found the below possible race
window:

CPU 1                                    CPU 2
-----                                    -----
do_swap_page
  if (data_race(si->flags & SWP_SYNCHRONOUS_IO)
  swap_readpage
    if (data_race(sis->flags & SWP_FS_OPS)) {
                                         swapoff
     ..
     p->swap_file = NULL;
     ..
    struct file *swap_file = sis->swap_file;
    struct address_space *mapping = swap_file->f_mapping;[oops!]

Note that for the pages that are swapped in through swap cache, this isn't
an issue. Because the page is locked, and the swap entry will be marked
with SWAP_HAS_CACHE, so swapoff() can not proceed until the page has been
unlocked.

Fix this race by using get/put_swap_device() to guard against concurrent
swapoff.

Link: https://lkml.kernel.org/r/20210426123316.806267-3-linmiaohe@huawei.com
Fixes: 0bcac06f27d7 ("mm,swap: skip swapcache for swapin of synchronous device")
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
Cc: Alex Shi <alexs@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Dennis Zhou <dennis@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/swapfile: use percpu_ref to serialize against concurrent swapoff

Patch series "close various race windows for swap", v6.

When I was investigating the swap code, I found some possible race
windows.  This series aims to fix all these races.  But using current
get/put_swap_device() to guard against concurrent swapoff for
swap_readpage() looks terrible because swap_readpage() may take really
long time.  And to reduce the performance overhead on the hot-path as much
as possible, it appears we can use the percpu_ref to close this race
window(as suggested by Huang, Ying).  The patch 1 adds percpu_ref support
for swap and most of the remaining patches try to use this to close
various race windows.  More details can be found in the respective
changelogs.

This patch (of 4):

Using current get/put_swap_device() to guard against concurrent swapoff
for some swap ops, e.g.  swap_readpage(), looks terrible because they
might take really long time.  This patch adds the percpu_ref support to
serialize against concurrent swapoff(as suggested by Huang, Ying).  Also
we remove the SWP_VALID flag because it's used together with RCU solution.

Link: https://lkml.kernel.org/r/20210426123316.806267-1-linmiaohe@huawei.com
Link: https://lkml.kernel.org/r/20210426123316.806267-2-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
Cc: Alex Shi <alexs@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Dennis Zhou <dennis@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: pagewalk: fix walk for hugepage tables

Pagewalk ignores hugepd entries and walk down the tables as if it was
traditionnal entries, leading to crazy result.

Add walk_hugepd_range() and use it to walk hugepage tables.

Link: https://lkml.kernel.org/r/38d04410700c8d02f28ba37e020b62c55d6f3d2c.1624597695.git.christophe.leroy@csgroup.eu
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Reviewed-by: Steven Price <steven.price@arm.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Daniel Axtens <dja@axtens.net>
Cc: "Oliver O'Halloran" <oohall@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: gup: pack has_pinned in MMF_HAS_PINNED

has_pinned 32bit can be packed in the MMF_HAS_PINNED bit as a noop
cleanup.

Any atomic_inc/dec to the mm cacheline shared by all threads in pin-fast
would reintroduce a loss of SMP scalability to pin-fast, so there's no
future potential usefulness to keep an atomic in the mm for this.

set_bit(MMF_HAS_PINNED) will be theoretically a bit slower than WRITE_ONCE
(atomic_set is equivalent to WRITE_ONCE), but the set_bit (just like
atomic_set after this commit) has to be still issued only once per "mm",
so the difference between the two will be lost in the noise.

will-it-scale "mmap2" shows no change in performance with enterprise
config as expected.

will-it-scale "pin_fast" retains the > 4000% SMP scalability performance
improvement against upstream as expected.

This is a noop as far as overall performance and SMP scalability are
concerned.

[peterx@redhat.com: pack has_pinned in MMF_HAS_PINNED]
Link: https://lkml.kernel.org/r/YJqWESqyxa8OZA+2@t490s
[akpm@linux-foundation.org: coding style fixes]
[peterx@redhat.com: fix build for task_mmu.c, introduce mm_set_has_pinned_flag, fix comments]

Link: https://lkml.kernel.org/r/20210507150553.208763-4-peterx@redhat.com
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Kirill Shutemov <kirill@shutemov.name>
Cc: Kirill Tkhai <ktkhai@virtuozzo.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: gup: allow FOLL_PIN to scale in SMP

has_pinned cannot be written by each pin-fast or it won't scale in SMP.
This isn't "false sharing" strictly speaking (it's more like "true
non-sharing"), but it creates the same SMP scalability bottleneck of
"false sharing".

To verify the improvement, below test is done on 40 cpus host with
Intel(R) Xeon(R) CPU E5-2630 v4 @ 2.20GHz (must be with
CONFIG_GUP_TEST=y):

  $ sudo chrt -f 1 ./gup_test -a  -m 512 -j 40

Where we can get (average value for 40 threads):

  Old kernel: 477729.97 (+- 3.79%)
  New kernel:  89144.65 (+-11.76%)

On a similar condition with 256 cpus, this commits increases the SMP
scalability of pin_user_pages_fast() executed by different threads of the
same process by more than 4000%.

[peterx@redhat.com: rewrite commit message, add parentheses against "(A & B)"]

Link: https://lkml.kernel.org/r/20210507150553.208763-3-peterx@redhat.com
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Kirill Shutemov <kirill@shutemov.name>
Cc: Kirill Tkhai <ktkhai@virtuozzo.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/gup_benchmark: support threading

Patch series "mm/gup: Fix pin page write cache bouncing on has_pinned", v2.

This series contains 3 patches, the 1st one enables threading for
gup_benchmark in the kselftest.  The latter two patches are collected from
Andrea's local branch which can fix write cache bouncing issue with
pinning fast-gup.

To be explicit on the latter two patches:

  - the 2nd patch fixes the perf degrade when introducing has_pinned, then

  - the last patch tries to remove the has_pinned with a bit in mm->flags

For patch 3: originally I think we had a plan to reuse has_pinned into a
counter very soon, however that's not happening at least until today, so
maybe it proves that we can remove it until we really want such a counter
for whatever reason.  As the commit message stated, it saves 4 bytes for
each mm without observable regressions.

Regarding testing: we can reference to the commit message of patch 2 for
some detailed testing with will-is-scale.  Meanwhile I did patch 1 just
because then we can even easily verify the patchset using the existing
kselftest facilities or even regress test it in the future with the repo
if we want.

Below numbers are extra verification tests that I did besides commit
message of patch 2 using the new gup_benchmark and 256 cpus.  Below test
is done on 40 cpus host with Intel(R) Xeon(R) CPU E5-2630 v4 @ 2.20GHz,
and I can get similar result (of course the write cache bouncing get
severe with even more cores).

After patch 1 applied (only test patch, so using old kernel):

  $ sudo chrt -f 1 ./gup_test -a  -m 512 -j 40
  PIN_FAST_BENCHMARK: Time: get:459632 put:5990 us
  PIN_FAST_BENCHMARK: Time: get:461967 put:5840 us
  PIN_FAST_BENCHMARK: Time: get:464521 put:6140 us
  PIN_FAST_BENCHMARK: Time: get:465176 put:7100 us
  PIN_FAST_BENCHMARK: Time: get:465960 put:6733 us
  PIN_FAST_BENCHMARK: Time: get:465324 put:6781 us
  PIN_FAST_BENCHMARK: Time: get:466018 put:7130 us
  PIN_FAST_BENCHMARK: Time: get:466362 put:7118 us
  PIN_FAST_BENCHMARK: Time: get:465118 put:6975 us
  PIN_FAST_BENCHMARK: Time: get:466422 put:6602 us
  PIN_FAST_BENCHMARK: Time: get:465791 put:6818 us
  PIN_FAST_BENCHMARK: Time: get:467091 put:6298 us
  PIN_FAST_BENCHMARK: Time: get:467694 put:5432 us
  PIN_FAST_BENCHMARK: Time: get:469575 put:5581 us
  PIN_FAST_BENCHMARK: Time: get:468124 put:6055 us
  PIN_FAST_BENCHMARK: Time: get:468877 put:6720 us
  PIN_FAST_BENCHMARK: Time: get:467212 put:4961 us
  PIN_FAST_BENCHMARK: Time: get:467834 put:6697 us
  PIN_FAST_BENCHMARK: Time: get:470778 put:6398 us
  PIN_FAST_BENCHMARK: Time: get:469788 put:6310 us
  PIN_FAST_BENCHMARK: Time: get:488277 put:7113 us
  PIN_FAST_BENCHMARK: Time: get:486613 put:7085 us
  PIN_FAST_BENCHMARK: Time: get:486940 put:7202 us
  PIN_FAST_BENCHMARK: Time: get:488728 put:7101 us
  PIN_FAST_BENCHMARK: Time: get:487570 put:7327 us
  PIN_FAST_BENCHMARK: Time: get:489260 put:7027 us
  PIN_FAST_BENCHMARK: Time: get:488846 put:6866 us
  PIN_FAST_BENCHMARK: Time: get:488521 put:6745 us
  PIN_FAST_BENCHMARK: Time: get:489950 put:6459 us
  PIN_FAST_BENCHMARK: Time: get:489777 put:6617 us
  PIN_FAST_BENCHMARK: Time: get:488224 put:6591 us
  PIN_FAST_BENCHMARK: Time: get:488644 put:6477 us
  PIN_FAST_BENCHMARK: Time: get:488754 put:6711 us
  PIN_FAST_BENCHMARK: Time: get:488875 put:6743 us
  PIN_FAST_BENCHMARK: Time: get:489290 put:6657 us
  PIN_FAST_BENCHMARK: Time: get:490264 put:6684 us
  PIN_FAST_BENCHMARK: Time: get:489631 put:6737 us
  PIN_FAST_BENCHMARK: Time: get:488434 put:6655 us
  PIN_FAST_BENCHMARK: Time: get:492213 put:6297 us
  PIN_FAST_BENCHMARK: Time: get:491124 put:6173 us

After the whole series applied (new fixed kernel):

  $ sudo chrt -f 1 ./gup_test -a  -m 512 -j 40
  PIN_FAST_BENCHMARK: Time: get:82038 put:7041 us
  PIN_FAST_BENCHMARK: Time: get:82144 put:6817 us
  PIN_FAST_BENCHMARK: Time: get:83417 put:6674 us
  PIN_FAST_BENCHMARK: Time: get:82540 put:6594 us
  PIN_FAST_BENCHMARK: Time: get:83214 put:6681 us
  PIN_FAST_BENCHMARK: Time: get:83444 put:6889 us
  PIN_FAST_BENCHMARK: Time: get:83194 put:7499 us
  PIN_FAST_BENCHMARK: Time: get:84876 put:7369 us
  PIN_FAST_BENCHMARK: Time: get:86092 put:10289 us
  PIN_FAST_BENCHMARK: Time: get:86153 put:10415 us
  PIN_FAST_BENCHMARK: Time: get:85026 put:7751 us
  PIN_FAST_BENCHMARK: Time: get:85458 put:7944 us
  PIN_FAST_BENCHMARK: Time: get:85735 put:8154 us
  PIN_FAST_BENCHMARK: Time: get:85851 put:8299 us
  PIN_FAST_BENCHMARK: Time: get:86323 put:9617 us
  PIN_FAST_BENCHMARK: Time: get:86288 put:10496 us
  PIN_FAST_BENCHMARK: Time: get:87697 put:9346 us
  PIN_FAST_BENCHMARK: Time: get:87980 put:8382 us
  PIN_FAST_BENCHMARK: Time: get:88719 put:8400 us
  PIN_FAST_BENCHMARK: Time: get:87616 put:8588 us
  PIN_FAST_BENCHMARK: Time: get:86730 put:9563 us
  PIN_FAST_BENCHMARK: Time: get:88167 put:8673 us
  PIN_FAST_BENCHMARK: Time: get:86844 put:9777 us
  PIN_FAST_BENCHMARK: Time: get:88068 put:11774 us
  PIN_FAST_BENCHMARK: Time: get:86170 put:15676 us
  PIN_FAST_BENCHMARK: Time: get:87967 put:12827 us
  PIN_FAST_BENCHMARK: Time: get:95773 put:7652 us
  PIN_FAST_BENCHMARK: Time: get:87734 put:13650 us
  PIN_FAST_BENCHMARK: Time: get:89833 put:14237 us
  PIN_FAST_BENCHMARK: Time: get:96186 put:8029 us
  PIN_FAST_BENCHMARK: Time: get:95532 put:8886 us
  PIN_FAST_BENCHMARK: Time: get:95351 put:5826 us
  PIN_FAST_BENCHMARK: Time: get:96401 put:8407 us
  PIN_FAST_BENCHMARK: Time: get:96473 put:8287 us
  PIN_FAST_BENCHMARK: Time: get:97177 put:8430 us
  PIN_FAST_BENCHMARK: Time: get:98120 put:5263 us
  PIN_FAST_BENCHMARK: Time: get:96271 put:7757 us
  PIN_FAST_BENCHMARK: Time: get:99628 put:10467 us
  PIN_FAST_BENCHMARK: Time: get:99344 put:10045 us
  PIN_FAST_BENCHMARK: Time: get:94212 put:15485 us

Summary:

  Old kernel: 477729.97 (+-3.79%)
  New kernel:  89144.65 (+-11.76%)

This patch (of 3):

Add a new parameter "-j N" to support concurrent gup test.

Link: https://lkml.kernel.org/r/20210507150553.208763-1-peterx@redhat.com
Link: https://lkml.kernel.org/r/20210507150553.208763-2-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Kirill Tkhai <ktkhai@virtuozzo.com>
Cc: Kirill Shutemov <kirill@shutemov.name>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: move page dirtying prototypes from mm.h

These functions implement the address_space ->set_page_dirty operation and
should live in pagemap.h, not mm.h so that the rest of the kernel doesn't
get funny ideas about calling them directly.

Link: https://lkml.kernel.org/r/20210615162342.1669332-7-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs: remove noop_set_page_dirty()

Use __set_page_dirty_no_writeback() instead.  This will set the dirty bit
on the page, which will be used to avoid calling set_page_dirty() in the
future.  It will have no effect on actually writing the page back, as the
pages are not on any LRU lists.

[akpm@linux-foundation.org: export __set_page_dirty_no_writeback() to modules]

Link: https://lkml.kernel.org/r/20210615162342.1669332-6-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs: remove anon_set_page_dirty()

Use __set_page_dirty_no_writeback() instead.  This will set the dirty bit
on the page, which will be used to avoid calling set_page_dirty() in the
future.  It will have no effect on actually writing the page back, as the
pages are not on any LRU lists.

Link: https://lkml.kernel.org/r/20210615162342.1669332-5-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

iomap: use __set_page_dirty_nobuffers

The only difference between iomap_set_page_dirty() and
__set_page_dirty_nobuffers() is that the latter includes a debugging check
that a !Uptodate page has private data.

Link: https://lkml.kernel.org/r/20210615162342.1669332-4-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/writeback: use __set_page_dirty in __set_page_dirty_nobuffers

This is fundamentally the same code, so just call it instead of
duplicating it.

Link: https://lkml.kernel.org/r/20210615162342.1669332-3-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/writeback: move __set_page_dirty() to core mm

Patch series "Further set_page_dirty cleanups".

Prompted by Christoph's recent patches, here are some more patches to
improve the state of set_page_dirty().  They're all from the folio tree,
so they've been tested to a certain extent.

This patch (of 6):

Nothing in __set_page_dirty() is specific to buffer_head, so move it to
mm/page-writeback.c.  That removes the only caller of
account_page_dirtied() outside of page-writeback.c, so make it static.

Link: https://lkml.kernel.org/r/20210615162342.1669332-1-willy@infradead.org
Link: https://lkml.kernel.org/r/20210615162342.1669332-2-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: require ->set_page_dirty to be explicitly wired up

Remove the CONFIG_BLOCK default to __set_page_dirty_buffers and just wire
that method up for the missing instances.

[hch@lst.de: ecryptfs: add a ->set_page_dirty cludge]
Link: https://lkml.kernel.org/r/20210624125250.536369-1-hch@lst.de
Link: https://lkml.kernel.org/r/20210614061512.3966143-4-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Tyler Hicks <code@tyhicks.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs: move ramfs_aops to libfs

Move the ramfs aops to libfs and reuse them for kernfs and configfs.
Thosw two did not wire up ->set_page_dirty before and now get
__set_page_dirty_no_writeback, which is the right one for no-writeback
address_space usage.

Drop the now unused exports of the libfs helpers only used for ramfs-style
pagecache usage.

Link: https://lkml.kernel.org/r/20210614061512.3966143-3-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs: unexport __set_page_dirty

Patch series "remove the implicit .set_page_dirty default".

This series cleans up a few lose ends around ->set_page_dirty, most
importantly removes the default to the buffer head based on if no method
is wired up.

This patch (of 3):

__set_page_dirty is only used by built-in code.

Link: https://lkml.kernel.org/r/20210614061512.3966143-1-hch@lst.de
Link: https://lkml.kernel.org/r/20210614061512.3966143-2-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

writeback, cgroup: release dying cgwbs by switching attached inodes

Asynchronously try to release dying cgwbs by switching attached inodes to
the nearest living ancestor wb.  It helps to get rid of per-cgroup
writeback structures themselves and of pinned memory and block cgroups,
which are significantly larger structures (mostly due to large per-cpu
statistics data).  This prevents memory waste and helps to avoid different
scalability problems caused by large piles of dying cgroups.

Reuse the existing mechanism of inode switching used for foreign inode
detection.  To speed things up batch up to 115 inode switching in a single
operation (the maximum number is selected so that the resulting struct
inode_switch_wbs_context can fit into 1024 bytes).  Because every
switching consists of two steps divided by an RCU grace period, it would
be too slow without batching.  Please note that the whole batch counts as
a single operation (when increasing/decreasing isw_nr_in_flight).  This
allows to keep umounting working (flush the switching queue), however
prevents cleanups from consuming the whole switching quota and effectively
blocking the frn switching.

A cgwb cleanup operation can fail due to different reasons (e.g.  not
enough memory, the cgwb has an in-flight/pending io, an attached inode in
a wrong state, etc).  In this case the next scheduled cleanup will make a
new attempt.  An attempt is made each time a new cgwb is offlined (in
other words a memcg and/or a blkcg is deleted by a user).  In the future
an additional attempt scheduled by a timer can be implemented.

[guro@fb.com: replace open-coded "115" with arithmetic]
Link: https://lkml.kernel.org/r/YMEcSBcq/VXMiPPO@carbon.dhcp.thefacebook.com
[guro@fb.com: add smp_mb() to inode_prepare_wbs_switch()]
Link: https://lkml.kernel.org/r/YMFa+guFw7OFjf3X@carbon.dhcp.thefacebook.com
[willy@infradead.org: fix documentation]
Link: https://lkml.kernel.org/r/20210615200242.1716568-2-willy@infradead.org
Link: https://lkml.kernel.org/r/20210608230225.2078447-9-guro@fb.com
Signed-off-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: Jan Kara <jack@suse.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

writeback, cgroup: support switching multiple inodes at once

Currently only a single inode can be switched to another writeback
structure at once.  That means to switch an inode a separate
inode_switch_wbs_context structure must be allocated, and a separate rcu
callback and work must be scheduled.

It's fine for the existing ad-hoc switching, which is not happening that
often, but sub-optimal for massive switching required in order to release
a writeback structure.  To prepare for it, let's add a support for
switching multiple inodes at once.

Instead of containing a single inode pointer, inode_switch_wbs_context
will contain a NULL-terminated array of inode pointers.
inode_do_switch_wbs() will be called for each inode.

To optimize the locking bdi->wb_switch_rwsem, old_wb's and new_wb's
list_locks will be acquired and released only once altogether for all
inodes.  wb_wakeup() will be also be called only once.  Instead of calling
wb_put(old_wb) after each successful switch, wb_put_many() is introduced
and used.

Link: https://lkml.kernel.org/r/20210608230225.2078447-8-guro@fb.com
Signed-off-by: Roman Gushchin <guro@fb.com>
Acked-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Dennis Zhou <dennis@kernel.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: Jan Kara <jack@suse.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

writeback, cgroup: split out the functional part of inode_switch_wbs_work_fn()

Split out the functional part of the inode_switch_wbs_work_fn() function
as inode_do switch_wbs() to reuse it later for switching inodes attached
to dying cgwbs.

This commit doesn't bring any functional changes.

Link: https://lkml.kernel.org/r/20210608230225.2078447-7-guro@fb.com
Signed-off-by: Roman Gushchin <guro@fb.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: Dennis Zhou <dennis@kernel.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: Jan Kara <jack@suse.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

writeback, cgroup: keep list of inodes attached to bdi_writeback

Currently there is no way to iterate over inodes attached to a specific
cgwb structure.  It limits the ability to efficiently reclaim the
writeback structure itself and associated memory and block cgroup
structures without scanning all inodes belonging to a sb, which can be
prohibitively expensive.

While dirty/in-active-writeback an inode belongs to one of the
bdi_writeback's io lists: b_dirty, b_io, b_more_io and b_dirty_time.  Once
cleaned up, it's removed from all io lists.  So the inode->i_io_list can
be reused to maintain the list of inodes, attached to a bdi_writeback
structure.

This patch introduces a new wb->b_attached list, which contains all inodes
which were dirty at least once and are attached to the given cgwb.  Inodes
attached to the root bdi_writeback structures are never placed on such
list.  The following patch will use this list to try to release cgwbs
structures more efficiently.

Link: https://lkml.kernel.org/r/20210608230225.2078447-6-guro@fb.com
Signed-off-by: Roman Gushchin <guro@fb.com>
Suggested-by: Jan Kara <jack@suse.cz>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: Dennis Zhou <dennis@kernel.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: Jan Kara <jack@suse.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

writeback, cgroup: switch to rcu_work API in inode_switch_wbs()

Inode's wb switching requires two steps divided by an RCU grace period.
It's currently implemented as an RCU callback inode_switch_wbs_rcu_fn(),
which schedules inode_switch_wbs_work_fn() as a work.

Switching to the rcu_work API allows to do the same in a cleaner and
slightly shorter form.

Link: https://lkml.kernel.org/r/20210608230225.2078447-5-guro@fb.com
Signed-off-by: Roman Gushchin <guro@fb.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: Dennis Zhou <dennis@kernel.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: Jan Kara <jack@suse.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

writeback, cgroup: increment isw_nr_in_flight before grabbing an inode

isw_nr_in_flight is used to determine whether the inode switch queue
should be flushed from the umount path.  Currently it's increased after
grabbing an inode and even scheduling the switch work.  It means the
umount path can walk past cleanup_offline_cgwb() with active inode
references, which can result in a "Busy inodes after unmount." message and
use-after-free issues (with inode->i_sb which gets freed).

Fix it by incrementing isw_nr_in_flight before doing anything with the
inode and decrementing in the case when switching wasn't scheduled.

The problem hasn't yet been seen in the real life and was discovered by
Jan Kara by looking into the code.

Link: https://lkml.kernel.org/r/20210608230225.2078447-4-guro@fb.com
Signed-off-by: Roman Gushchin <guro@fb.com>
Suggested-by: Jan Kara <jack@suse.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: Dennis Zhou <dennis@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

writeback, cgroup: add smp_mb() to cgroup_writeback_umount()

A full memory barrier is required between clearing SB_ACTIVE flag in
generic_shutdown_super() and checking isw_nr_in_flight in
cgroup_writeback_umount(), otherwise a new switch operation might be
scheduled after atomic_read(&isw_nr_in_flight) returned 0.  This would
result in a non-flushed isw_wq, and a potential crash.

The problem hasn't yet been seen in the real life and was discovered by
Jan Kara by looking into the code.

Link: https://lkml.kernel.org/r/20210608230225.2078447-3-guro@fb.com
Signed-off-by: Roman Gushchin <guro@fb.com>
Suggested-by: Jan Kara <jack@suse.cz>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: Dennis Zhou <dennis@kernel.org>
Cc: Jan Kara <jack@suse.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

writeback, cgroup: do not switch inodes with I_WILL_FREE flag

Patch series "cgroup, blkcg: prevent dirty inodes to pin dying memory cgroups", v9.

When an inode is getting dirty for the first time it's associated with a
wb structure (see __inode_attach_wb()).  It can later be switched to
another wb (if e.g.  some other cgroup is writing a lot of data to the
same inode), but otherwise stays attached to the original wb until being
reclaimed.

The problem is that the wb structure holds a reference to the original
memory and blkcg cgroups.  So if an inode has been dirty once and later is
actively used in read-only mode, it has a good chance to pin down the
original memory and blkcg cgroups forever.  This is often the case with
services bringing data for other services, e.g.  updating some rpm
packages.

In the real life it becomes a problem due to a large size of the memcg
structure, which can easily be 1000x larger than an inode.  Also a really
large number of dying cgroups can raise different scalability issues, e.g.
making the memory reclaim costly and less effective.

To solve the problem inodes should be eventually detached from the
corresponding writeback structure.  It's inefficient to do it after every
writeback completion.  Instead it can be done whenever the original memory
cgroup is offlined and writeback structure is getting killed.  Scanning
over a (potentially long) list of inodes and detach them from the
writeback structure can take quite some time.  To avoid scanning all
inodes, attached inodes are kept on a new list (b_attached).  To make it
less noticeable to a user, the scanning and switching is performed from a
work context.

Big thanks to Jan Kara, Dennis Zhou, Hillf Danton and Tejun Heo for their
ideas and contribution to this patchset.

This patch (of 8):

If an inode's state has I_WILL_FREE flag set, the inode will be freed
soon, so there is no point in trying to switch the inode to a different
cgwb.

I_WILL_FREE was ignored since the introduction of the inode switching, so
it looks like it doesn't lead to any noticeable issues for a user.  This
is why the patch is not intended for a stable backport.

Link: https://lkml.kernel.org/r/20210608230225.2078447-1-guro@fb.com
Link: https://lkml.kernel.org/r/20210608230225.2078447-2-guro@fb.com
Signed-off-by: Roman Gushchin <guro@fb.com>
Suggested-by: Jan Kara <jack@suse.cz>
Acked-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Dennis Zhou <dennis@kernel.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: Jan Kara <jack@suse.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/page-writeback: use __this_cpu_inc() in account_page_dirtied()

As account_page_dirtied() was always protected by xa_lock_irqsave(), so
using __this_cpu_inc() is better.

Link: https://lkml.kernel.org/r/20210512144742.4764-1-wuchi.zero@gmail.com
Signed-off-by: Chi Wu <wuchi.zero@gmail.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Howard Cochran <hcochran@kernelspring.com>
Cc: Miklos Szeredi <mszeredi@redhat.com>
Cc: Sedat Dilek <sedat.dilek@gmail.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/page-writeback: update the comment of Dirty position control

As the value of pos_ratio_polynom() clamp between 0 and 2LL <<
RATELIMIT_CALC_SHIFT, the global control line should be consistent with
it.

Link: https://lkml.kernel.org/r/20210511103606.3732-1-wuchi.zero@gmail.com
Signed-off-by: Chi Wu <wuchi.zero@gmail.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Jens Axboe <axboe@fb.com>
Cc: Howard Cochran <hcochran@kernelspring.com>
Cc: Miklos Szeredi <mszeredi@redhat.com>
Cc: Sedat Dilek <sedat.dilek@gmail.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/page-writeback: Fix performance when BDI's share of ratio is 0.

Fix performance when BDI's share of ratio is 0.

The issue is similar to commit 74d369443325 ("writeback: Fix
performance regression in wb_over_bg_thresh()").

Balance_dirty_pages and the writeback worker will also disagree on
whether writeback when a BDI uses BDI_CAP_STRICTLIMIT and BDI's share
of the thresh ratio is zero.

For example, A thread on cpu0 writes 32 pages and then
balance_dirty_pages, it will wake up background writeback and pauses
because wb_dirty > wb->wb_thresh = 0 (share of thresh ratio is zero).
A thread may runs on cpu0 again because scheduler prefers pre_cpu.
Then writeback worker may runs on other cpus(1,2..) which causes the
value of wb_stat(wb, WB_RECLAIMABLE) in wb_over_bg_thresh is 0 and does
not writeback and returns.

Thus, balance_dirty_pages keeps looping, sleeping and then waking up the
worker who will do nothing. It remains stuck in this state until the
writeback worker hit the right dirty cpu or the dirty pages expire.

The fix that we should get the wb_stat_sum radically when thresh is low.

Link: https://lkml.kernel.org/r/20210428225046.16301-1-wuchi.zero@gmail.com
Signed-off-by: Chi Wu <wuchi.zero@gmail.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Tejun Heo <tj@kernel.org>
Cc: Miklos Szeredi <mszeredi@redhat.com>
Cc: Sedat Dilek <sedat.dilek@gmail.com>
Cc: Jens Axboe <axboe@fb.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: page-writeback: kill get_writeback_state() comments

The get_writeback_state() has gone since 2006, kill related comments.

Link: https://lkml.kernel.org/r/20210508125026.56600-1-wangkefeng.wang@huawei.com
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

virtio_balloon: specify page reporting order if needed

The page reporting won't be triggered if the freeing page can't come up
with a free area, whose size is equal or bigger than the threshold (page
reporting order).  The default page reporting order, equal to
@pageblock_order, is too huge on some architectures to trigger page
reporting.  One example is ARM64 when 64KB base page size is used.

      PAGE_SIZE:          64KB
      pageblock_order:    13       (512MB)
      MAX_ORDER:          14

This specifies the page reporting order to 5 (2MB) for this specific case
so that page reporting can be triggered.

Link: https://lkml.kernel.org/r/20210625014710.42954-5-gshan@redhat.com
Signed-off-by: Gavin Shan <gshan@redhat.com>
Reviewed-by: Alexander Duyck <alexanderduyck@fb.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/page_reporting: allow driver to specify reporting order

The page reporting order (threshold) is sticky to @pageblock_order by
default.  The page reporting can never be triggered because the freeing
page can't come up with a free area like that huge.  The situation becomes
worse when the system memory becomes heavily fragmented.

For example, the following configurations are used on ARM64 when 64KB base
page size is enabled.  In this specific case, the page reporting won't be
triggered until the freeing page comes up with a 512MB free area.  That's
hard to be met, especially when the system memory becomes heavily
fragmented.

   PAGE_SIZE:          64KB
   HPAGE_SIZE:         512MB
   pageblock_order:    13       (512MB)
   MAX_ORDER:          14

This allows the drivers to specify the page reporting order when the page
reporting device is registered.  It falls back to @pageblock_order if it's
not specified by the driver.  The existing users (hv_balloon and
virtio_balloon) don't specify it and @pageblock_order is still taken as
their page reporting order.  So this shouldn't introduce any functional
changes.

Link: https://lkml.kernel.org/r/20210625014710.42954-4-gshan@redhat.com
Signed-off-by: Gavin Shan <gshan@redhat.com>
Reviewed-by: Alexander Duyck <alexanderduyck@fb.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/page_reporting: export reporting order as module parameter

The macro PAGE_REPORTING_MIN_ORDER is defined as the page reporting
threshold.  It can't be adjusted at runtime.

This introduces a variable (@page_reporting_order) to replace the marcro
(PAGE_REPORTING_MIN_ORDER).  MAX_ORDER is assigned to it initially,
meaning the page reporting is disabled.  It will be specified by driver if
valid one is provided.  Otherwise, it will fall back to @pageblock_order.
It's also exported so that the page reporting order can be adjusted at
runtime.

Link: https://lkml.kernel.org/r/20210625014710.42954-3-gshan@redhat.com
Signed-off-by: Gavin Shan <gshan@redhat.com>
Suggested-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Alexander Duyck <alexanderduyck@fb.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/page_reporting: fix code style in __page_reporting_request()

Patch series "mm/page_reporting: Make page reporting work on arm64 with 64KB page size", v4.

The page reporting threshold is currently equal to @pageblock_order, which
is 13 and 512MB on arm64 with 64KB base page size selected.  The page
reporting won't be triggered if the freeing page can't come up with a free
area like that huge.  The condition is hard to be met, especially when the
system memory becomes fragmented.

This series intends to solve the issue by having page reporting threshold
as 5 (2MB) on arm64 with 64KB base page size.  The patches are organized
as:

   PATCH[1/4] Fix some coding style in __page_reporting_request().
   PATCH[2/4] Represents page reporting order with variable so that it can
              be exported as module parameter.
   PATCH[3/4] Allows the device driver (e.g. virtio_balloon) to specify
              the page reporting order when the device info is registered.
   PATCH[4/4] Specifies the page reporting order to 5, corresponding to
              2MB in size on ARM64 when 64KB base page size is used.

This patch (of 4):

The lines of comments would be starting with one, instead two space.  This
corrects the style.

Link: https://lkml.kernel.org/r/20210625014710.42954-1-gshan@redhat.com
Link: https://lkml.kernel.org/r/20210625014710.42954-2-gshan@redhat.com
Signed-off-by: Gavin Shan <gshan@redhat.com>
Reviewed-by: Alexander Duyck <alexanderduyck@fb.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: mmap_lock: use local locks instead of disabling preemption

mmap_lock will explicitly disable/enable preemption upon manipulating its
local CPU variables.  This is to be expected, but in this case, it doesn't
play well with PREEMPT_RT.  The preemption disabled code section also
takes a spin-lock.  Spin-locks in RT systems will try to schedule, which
is exactly what we're trying to avoid.

To mitigate this, convert the explicit preemption handling to local_locks.
Which are RT aware, and will disable migration instead of preemption when
PREEMPT_RT=y.

The faulty call trace looks like the following:
    __mmap_lock_do_trace_*()
      preempt_disable()
      get_mm_memcg_path()
        cgroup_path()
          kernfs_path_from_node()
            spin_lock_irqsave() /* Scheduling while atomic! */

Link: https://lkml.kernel.org/r/20210604163506.2103900-1-nsaenzju@redhat.com
Fixes: 2b5067a8143e3 ("mm: mmap_lock: add tracepoints around lock acquisition ")
Signed-off-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
Tested-by: Axel Rasmussen <axelrasmussen@google.com>
Reviewed-by: Axel Rasmussen <axelrasmussen@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/debug_vm_pgtable: ensure THP availability via has_transparent_hugepage()

On certain platforms, THP support could not just be validated via the
build option CONFIG_TRANSPARENT_HUGEPAGE.  Instead
has_transparent_hugepage() also needs to be called upon to verify THP
runtime support.  Otherwise the debug test will just run into unusable THP
helpers like in the case of a 4K hash config on powerpc platform [1].
This just moves all pfn_pmd() and pfn_pud() after THP runtime validation
with has_transparent_hugepage() which prevents the mentioned problem.

[1] https://bugzilla.kernel.org/show_bug.cgi?id=213069

Link: https://lkml.kernel.org/r/1621397588-19211-1-git-send-email-anshuman.khandual@arm.com
Fixes: 787d563b8642 ("mm/debug_vm_pgtable: fix kernel crash by checking for THP support")
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

tools/vm/page_owner_sort.c: check malloc() return

Link: https://lkml.kernel.org/r/20210506131402.10416-1-tangbin@cmss.chinamobile.com
Signed-off-by: Zhang Shengju <zhangshengju@cmss.chinamobile.com>
Signed-off-by: Tang Bin <tangbin@cmss.chinamobile.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

dax: fix ENOMEM handling in grab_mapping_entry()

grab_mapping_entry() has a bug in handling of ENOMEM condition.  Suppose
we have a PMD entry at index i which we are downgrading to a PTE entry.
grab_mapping_entry() will set pmd_downgrade to true, lock the entry, clear
the entry in xarray, and decrement mapping->nrpages.  The it will call:

entry = dax_make_entry(pfn_to_pfn_t(0), flags);
dax_lock_entry(xas, entry);

which inserts new PTE entry into xarray.  However this may fail allocating
the new node.  We handle this by:

if (xas_nomem(xas, mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM))
goto retry;

however pmd_downgrade stays set to true even though 'entry' returned from
get_unlocked_entry() will be NULL now.  And we will go again through the
downgrade branch.  This is mostly harmless except that mapping->nrpages is
decremented again and we temporarily have an invalid entry stored in
xarray.  Fix the problem by setting pmd_downgrade to false each time we
lookup the entry we work with so that it matches the entry we found.

Link: https://lkml.kernel.org/r/20210622160015.18004-1-jack@suse.cz
Fixes: b15cd800682f ("dax: Convert page fault handlers to XArray")
Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/kmemleak: fix possible wrong memory scanning period

This commit contains 3 modifications:

1. Convert the type of jiffies_scan_wait to "unsigned long".

2. Use READ/WRITE_ONCE() for accessing "jiffies_scan_wait".

3. Fix the possible wrong memory scanning period.  If you set a large
   memory scanning period like blow, then the "secs" variable will be
   non-zero, however the value of "jiffies_scan_wait" will be zero.

    echo "scan=0x10000000" > /sys/kernel/debug/kmemleak

It is because the type of the msecs_to_jiffies()'s parameter is "unsigned
int", and the "secs * 1000" is larger than its max value.  This in turn
leads a unexpected jiffies_scan_wait, maybe zero.  We corret it by
replacing kstrtoul() with kstrtouint(), and check the msecs to prevent it
larger than UINT_MAX.

Link: https://lkml.kernel.org/r/20210613174022.23044-1-yanfei.xu@windriver.com
Signed-off-by: Yanfei Xu <yanfei.xu@windriver.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/slub: add taint after the errors are printed

When running the kernel with panic_on_taint, the usual slub debug error
messages are not being printed when object corruption happens.  That's
because we panic in add_taint(), which is called before printing the
additional information.  This is a bit unfortunate as the error messages
are actually very useful, especially before a panic.  Let's fix this by
moving add_taint() after the errors are printed on the console.

Link: https://lkml.kernel.org/r/1623860738-146761-1-git-send-email-quic_c_gdjako@quicinc.com
Signed-off-by: Georgi Djakov <quic_c_gdjako@quicinc.com>
Acked-by: Rafael Aquini <aquini@redhat.com>
Acked-by: David Rientjes <rientjes@google.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Aaron Tomlin <atomlin@redhat.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: slub: move sysfs slab alloc/free interfaces to debugfs

alloc_calls and free_calls implementation in sysfs have two issues, one is
PAGE_SIZE limitation of sysfs and other is it does not adhere to "one
value per file" rule.

To overcome this issues, move the alloc_calls and free_calls
implementation to debugfs.

Debugfs cache will be created if SLAB_STORE_USER flag is set.

Rename the alloc_calls/free_calls to alloc_traces/free_traces, to be
inline with what it does.

[faiyazm@codeaurora.org: fix the leak of alloc/free traces debugfs interface]
Link: https://lkml.kernel.org/r/1624248060-30286-1-git-send-email-faiyazm@codeaurora.org
Link: https://lkml.kernel.org/r/1623438200-19361-1-git-send-email-faiyazm@codeaurora.org
Signed-off-by: Faiyaz Mohammed <faiyazm@codeaurora.org>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

slub: force on no_hash_pointers when slub_debug is enabled

Obscuring the pointers that slub shows when debugging makes for some
confusing slub debug messages:

 Padding overwritten. 0x0000000079f0674a-0x000000000d4dce17

Those addresses are hashed for kernel security reasons.  If we're trying
to be secure with slub_debug on the commandline we have some big problems
given that we dump whole chunks of kernel memory to the kernel logs.
Let's force on the no_hash_pointers commandline flag when slub_debug is on
the commandline.  This makes slub debug messages more meaningful and if by
chance a kernel address is in some slub debug object dump we will have a
better chance of figuring out what went wrong.

Note that we don't use %px in the slub code because we want to reduce the
number of places that %px is used in the kernel.  This also nicely prints
a big fat warning at kernel boot if slub_debug is on the commandline so
that we know that this kernel shouldn't be used on production systems.

[akpm@linux-foundation.org: fix build with CONFIG_SLUB_DEBUG=n]

Link: https://lkml.kernel.org/r/20210601182202.3011020-5-swboyd@chromium.org
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Petr Mladek <pmladek@suse.com>
Cc: Joe Perches <joe@perches.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

slub: indicate slab_fix() uses printf formats

Ideally, slab_fix() would be marked with __printf and the format here
would not use \n as that's emitted by the slab_fix().  Make these changes.

Link: https://lkml.kernel.org/r/20210601182202.3011020-4-swboyd@chromium.org
Signed-off-by: Joe Perches <joe@perches.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Petr Mladek <pmladek@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

slub: actually use 'message' in restore_bytes()

The message argument isn't used here.  Let's pass the string to the printk
message so that the developer can figure out what's happening, instead of
guessing that a redzone is being restored, etc.

Link: https://lkml.kernel.org/r/20210601182202.3011020-3-swboyd@chromium.org
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: David Rientjes <rientjes@google.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Joe Perches <joe@perches.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Petr Mladek <pmladek@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

slub: restore slub_debug=- behavior

Petch series "slub: Print non-hashed pointers in slub debugging", v3.

I was doing some debugging recently and noticed that my pointers were
being hashed while slub_debug was on the kernel commandline.  Let's force
on the no hash pointer option when slub_debug is on the kernel commandline
so that the prints are more meaningful.

The first two patches are something else I noticed while looking at the
code.  The message argument is never used so the debugging messages are
not as clear as they could be and the slub_debug=- behavior seems to be
busted.  Then there's a printf fixup from Joe and the final patch is the
one that force disables pointer hashing.

This patch (of 4):

Passing slub_debug=- on the kernel commandline is supposed to disable slub
debugging.  This is especially useful with CONFIG_SLUB_DEBUG_ON where the
default is to have slub debugging enabled in the build.  Due to some code
reorganization this behavior was dropped, but the code to make it work
mostly stuck around.  Restore the previous behavior by disabling the
static key when we parse the commandline and see that we're trying to
disable slub debugging.

Link: https://lkml.kernel.org/r/20210601182202.3011020-1-swboyd@chromium.org
Link: https://lkml.kernel.org/r/20210601182202.3011020-2-swboyd@chromium.org
Fixes: ca0cab65ea2b ("mm, slub: introduce static key for slub_debug()")
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Joe Perches <joe@perches.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Petr Mladek <pmladek@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm, slub: change run-time assertion in kmalloc_index() to compile-time

Currently when size is not supported by kmalloc_index, compiler will
generate a run-time BUG() while compile-time error is also possible, and
better.  So change BUG to BUILD_BUG_ON_MSG to make compile-time check
possible.

Also remove code that allocates more than 32MB because current
implementation supports only up to 32MB.

[42.hyeyoo@gmail.com: fix support for clang 10]
Link: https://lkml.kernel.org/r/20210518181247.GA10062@hyeyoo
[vbabka@suse.cz: fix false-positive assert in kernel/bpf/local_storage.c]
Link: https://lkml.kernel.org/r/bea97388-01df-8eac-091b-a3c89b4a4a09@suse.czLink:
[elver@google.com: kfence fix]
Link: https://lkml.kernel.org/r/20210512195227.245000695c9014242e9a00e5@linux-foundation.org
Signed-off-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Marco Elver <elver@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Marco Elver <elver@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

slub: remove resiliency_test() function

Function resiliency_test() is hidden behind #ifdef SLUB_RESILIENCY_TEST
that is not part of Kconfig, so nobody runs it.

This function is replaced with KUnit test for SLUB added by the previous
patch "selftests: add a KUnit test for SLUB debugging functionality".

Link: https://lkml.kernel.org/r/20210511150734.3492-3-glittao@gmail.com
Signed-off-by: Oliver Glitta <glittao@gmail.com>
Reviewed-by: Marco Elver <elver@google.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Oliver Glitta <glittao@gmail.com>
Cc: Brendan Higgins <brendanhiggins@google.com>
Cc: Daniel Latypov <dlatypov@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/slub, kunit: add a KUnit test for SLUB debugging functionality

SLUB has resiliency_test() function which is hidden behind #ifdef
SLUB_RESILIENCY_TEST that is not part of Kconfig, so nobody runs it.
KUnit should be a proper replacement for it.

Try changing byte in redzone after allocation and changing pointer to next
free node, first byte, 50th byte and redzone byte.  Check if validation
finds errors.

There are several differences from the original resiliency test: Tests
create own caches with known state instead of corrupting shared kmalloc
caches.

The corruption of freepointer uses correct offset, the original resiliency
test got broken with freepointer changes.

Scratch changing random byte test, because it does not have meaning in
this form where we need deterministic results.

Add new option CONFIG_SLUB_KUNIT_TEST in Kconfig.  Tests next_pointer,
first_word and clobber_50th_byte do not run with KASAN option on.  Because
the test deliberately modifies non-allocated objects.

Use kunit_resource to count errors in cache and silence bug reports.
Count error whenever slab_bug() or slab_fix() is called or when the count
of pages is wrong.

[glittao@gmail.com: remove unused function test_exit(), from SLUB KUnit test]
Link: https://lkml.kernel.org/r/20210512140656.12083-1-glittao@gmail.com
[akpm@linux-foundation.org: export kasan_enable/disable_current to modules]

Link: https://lkml.kernel.org/r/20210511150734.3492-2-glittao@gmail.com
Signed-off-by: Oliver Glitta <glittao@gmail.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Daniel Latypov <dlatypov@google.com>
Acked-by: Marco Elver <elver@google.com>
Cc: Brendan Higgins <brendanhiggins@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kunit: make test->lock irq safe

The upcoming SLUB kunit test will be calling kunit_find_named_resource()
from a context with disabled interrupts.  That means kunit's test->lock
needs to be IRQ safe to avoid potential deadlocks and lockdep splats.

This patch therefore changes the test->lock usage to spin_lock_irqsave()
and spin_unlock_irqrestore().

Link: https://lkml.kernel.org/r/20210511150734.3492-1-glittao@gmail.com
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Oliver Glitta <glittao@gmail.com>
Reviewed-by: Brendan Higgins <brendanhiggins@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Daniel Latypov <dlatypov@google.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Marco Elver <elver@google.com>
Cc: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

slab: use __func__ to trace function name

It is better to use __func__ to trace function name.

Link: https://lkml.kernel.org/r/31fdbad5c45cd1e26be9ff37be321b8586b80fee.1624355507.git.gumingtao@xiaomi.com
Signed-off-by: gumingtao <gumingtao@xiaomi.com>
Acked-by: Christoph Lameter <cl@linux.com>
Acked-by: David Rientjes <rientjes@google.com>
Reviewed-by: Aaron Tomlin <atomlin@redhat.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

doc: watchdog: modify the doc related to "watchdog/%u"

"watchdog/%u" threads has be replaced by cpu_stop_work.  The current
description is extremely misleading.

Link: https://lkml.kernel.org/r/1619687073-24686-5-git-send-email-wangqing@vivo.com
Signed-off-by: Wang Qing <wangqing@vivo.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Cc: "Guilherme G. Piccoli" <gpiccoli@canonical.com>
Cc: Joe Perches <joe@perches.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kees Cook <keescook@chromium.org>
Cc: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Cc: Qais Yousef <qais.yousef@arm.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Santosh Sivaraj <santosh@fossix.org>
Cc: Stephen Kitt <steve@sk2.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

doc: watchdog: modify the explanation related to watchdog thread

"watchdog/%u" threads has be replaced by cpu_stop_work.  The current
description is extremely misleading.

Link: https://lkml.kernel.org/r/1619687073-24686-4-git-send-email-wangqing@vivo.com
Signed-off-by: Wang Qing <wangqing@vivo.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Cc: "Guilherme G. Piccoli" <gpiccoli@canonical.com>
Cc: Joe Perches <joe@perches.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kees Cook <keescook@chromium.org>
Cc: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Cc: Qais Yousef <qais.yousef@arm.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Santosh Sivaraj <santosh@fossix.org>
Cc: Stephen Kitt <steve@sk2.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel: watchdog: modify the explanation related to watchdog thread

The watchdog thread has been replaced by cpu_stop_work, modify the
explanation related.

Link: https://lkml.kernel.org/r/1619687073-24686-2-git-send-email-wangqing@vivo.com
Signed-off-by: Wang Qing <wangqing@vivo.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Cc: Joe Perches <joe@perches.com>
Cc: Stephen Kitt <steve@sk2.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: "Guilherme G. Piccoli" <gpiccoli@canonical.com>
Cc: Qais Yousef <qais.yousef@arm.com>
Cc: Santosh Sivaraj <santosh@fossix.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

ocfs2: remove redundant initialization of variable ret

The variable ret is being initialized with a value that is never read, the
assignment is redundant and can be removed.

Addresses-Coverity: ("Unused value")
Link: https://lkml.kernel.org/r/20210613135148.74658-1-colin.king@canonical.com
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Acked-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Changwei Ge <gechangwei@live.cn>
Cc: Gang He <ghe@suse.com>
Cc: Jun Piao <piaojun@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

ocfs2: replace simple_strtoull() with kstrtoull()

simple_strtoull() is deprecated in some situation since it does not check
for the range overflow, use kstrtoull() instead.

Link: https://lkml.kernel.org/r/20210526092020.554341-3-chenhuang5@huawei.com
Signed-off-by: Chen Huang <chenhuang5@huawei.com>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Joseph Qi <jiangqi903@gmail.com>
Cc: Changwei Ge <gechangwei@live.cn>
Cc: Gang He <ghe@suse.com>
Cc: Jun Piao <piaojun@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

ocfs2: remove repeated uptodate check for buffer

In commit 60f91826ca62 ("buffer: Avoid setting buffer bits that are
already set"), function set_buffer_##name was added a test_bit() to check
buffer, which is the same as function buffer_##name.  The
!buffer_uptodate(bh) here is a repeated check.  Remove it.

Link: https://lkml.kernel.org/r/20210425025702.13628-1-wanjiabing@vivo.com
Signed-off-by: Wan Jiabing <wanjiabing@vivo.com>
Reviewed-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Changwei Ge <gechangwei@live.cn>
Cc: Gang He <ghe@suse.com>
Cc: Jun Piao <piaojun@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

ocfs2: remove redundant assignment to pointer queue

The pointer queue is being initialized with a value that is never read and
it is being updated later with a new value.  The initialization is
redundant and can be removed.

Addresses-Coverity: ("Unused value")
Link: https://lkml.kernel.org/r/20210513113957.57539-1-colin.king@canonical.com
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Acked-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Changwei Ge <gechangwei@live.cn>
Cc: Gang He <ghe@suse.com>
Cc: Jun Piao <piaojun@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

ocfs2: fix snprintf() checking

The snprintf() function returns the number of bytes which would have been
printed if the buffer was large enough.  In other words it can return ">=
remain" but this code assumes it returns "== remain".

The run time impact of this bug is not very severe.  The next iteration
through the loop would trigger a WARN() when we pass a negative limit to
snprintf().  We would then return success instead of -E2BIG.

The kernel implementation of snprintf() will never return negatives so
there is no need to check and I have deleted that dead code.

Link: https://lkml.kernel.org/r/20210511135350.GV1955@kadam
Fixes: a860f6eb4c6a ("ocfs2: sysfile interfaces for online file check")
Fixes: 74ae4e104dfc ("ocfs2: Create stack glue sysfs files.")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Changwei Ge <gechangwei@live.cn>
Cc: Gang He <ghe@suse.com>
Cc: Jun Piao <piaojun@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

ocfs2: remove unnecessary INIT_LIST_HEAD()

The list_head o2hb_node_events is initialized statically.  It is
unnecessary to initialize by INIT_LIST_HEAD().

Link: https://lkml.kernel.org/r/20210511115847.3817395-1-yangyingliang@huawei.com
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Reported-by: Hulk Robot <hulkci@huawei.com>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Joseph Qi <jiangqi903@gmail.com>
Cc: Changwei Ge <gechangwei@live.cn>
Cc: Gang He <ghe@suse.com>
Cc: Jun Piao <piaojun@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

squashfs: add option to panic on errors

Add an errors=panic mount option to make squashfs trigger a panic when
errors are encountered, similar to several other filesystems.  This allows
a kernel dump to be saved using which the corruption can be analysed and
debugged.

Inspired by a pre-fs_context patch by Anton Eliasson.

Link: https://lkml.kernel.org/r/20210527125019.14511-1-vincent.whitchurch@axis.com
Signed-off-by: Vincent Whitchurch <vincent.whitchurch@axis.com>
Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

ntfs: fix validity check for file name attribute

When checking the file name attribute, we want to ensure that it fits
within the bounds of ATTR_RECORD.  To do this, we should check that (attr
record + file name offset + file name length) < (attr record + attr record
length).

However, the original check did not include the file name offset in the
calculation.  This means that corrupted on-disk metadata might not caught
by the incorrect file name check, and lead to an invalid memory access.

An example can be seen in the crash report of a memory corruption error
found by Syzbot:
https://syzkaller.appspot.com/bug?id=a1a1e379b225812688566745c3e2f7242bffc246

Adding the file name offset to the validity check fixes this error and
passes the Syzbot reproducer test.

Link: https://lkml.kernel.org/r/20210614050540.289494-1-desmondcheongzx@gmail.com
Signed-off-by: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com>
Reported-by: syzbot+213ac8bb98f7f4420840@syzkaller.appspotmail.com
Tested-by: syzbot+213ac8bb98f7f4420840@syzkaller.appspotmail.com
Acked-by: Anton Altaparmakov <anton@tuxera.com>
Cc: Shuah Khan <skhan@linuxfoundation.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/spelling.txt: add more spellings to spelling.txt

Here are some of the more common spelling mistakes and typos that I've
found while fixing up spelling mistakes in the kernel in the past few
months.

Link: https://lkml.kernel.org/r/20210514093655.8829-1-colin.king@canonical.com
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

streamline_config.pl: add softtabstop=4 for vim users

The tab stop for Perl files is by default (at least in emacs) to be 4
spaces, where a tab is used for all 8 spaces.  Add a local variable
comment to make vim do the same by default, and this will help keep the
file consistent in the future when others edit it via vim and not emacs.

Link: https://lkml.kernel.org/r/20210322214032.293992979@goodmis.org
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: "John (Warthog9) Hawley" <warthog9@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

streamline_config.pl: make spacing consistent

Patch series "streamline_config.pl: Fix Perl spacing".

Talking with John Hawley about how vim and emacs deal with Perl files with
respect to tabs and spaces, I found that some of my Perl code in the
kernel had inconsistent spacing.  The way emacs handles Perl by default is
to use 4 spaces per indent, but make all 8 spaces into a single tab.  Vim
does not do this by default.  But if you add the vim variable control:

 # vim: softtabstop=4

to a perl file, it makes vim behave the same way as emacs.

The first patch is to change all 8 spaces into a single tab (mostly from
people editing the file with vim).  The next patch adds the softtabstop
variable to make vim act like emacs by default.

This patch (of 2):

As Perl code tends to have 4 space indentation, but uses tabs for every 8
spaces, make that consistent in the streamline_config.pl code.  Replace
all 8 spaces with a single tab.

Link: https://lkml.kernel.org/r/20210322214032.133596267@goodmis.org
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: "John (Warthog9) Hawley" <warthog9@kernel.org>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

ia64: mca_drv: fix incorrect array size calculation

gcc points out a mistake in the mca driver that goes back to before the
git history:

arch/ia64/kernel/mca_drv.c: In function 'init_record_index_pools':
arch/ia64/kernel/mca_drv.c:346:54: error: expression does not compute the number of elements in this array; element typ
e is 'int', not 'size_t' {aka 'long unsigned int'} [-Werror=sizeof-array-div]
  346 |         for (i = 1; i < sizeof sal_log_sect_min_sizes/sizeof(size_t); i++)
      |                                                      ^

This is the same as sizeof(size_t), which is two shorter than the actual
array.  Use the ARRAY_SIZE() macro to get the correct calculation instead.

Link: https://lkml.kernel.org/r/20210514214123.875971-1-arnd@kernel.org
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

ia64: headers: drop duplicated words

Delete the repeated words "to" and "the".

Link: https://lkml.kernel.org/r/20210507184837.10754-1-rdunlap@infradead.org
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kthread_worker: fix return value when kthread_mod_delayed_work() races with kthread_cancel_delayed_work_sync()

kthread_mod_delayed_work() might race with
kthread_cancel_delayed_work_sync() or another kthread_mod_delayed_work()
call.  The function lets the other operation win when it sees
work->canceling counter set.  And it returns @false.

But it should return @true as it is done by the related workqueue API, see
mod_delayed_work_on().

The reason is that the return value might be used for reference counting.
It has to distinguish the case when the number of queued works has changed
or stayed the same.

The change is safe.  kthread_mod_delayed_work() return value is not
checked anywhere at the moment.

Link: https://lore.kernel.org/r/20210521163526.GA17916@redhat.com
Link: https://lkml.kernel.org/r/20210610133051.15337-4-pmladek@suse.com
Signed-off-by: Petr Mladek <pmladek@suse.com>
Reported-by: Oleg Nesterov <oleg@redhat.com>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Minchan Kim <minchan@google.com>
Cc: <jenhaochen@google.com>
Cc: Martin Liu <liumartin@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kthread: switch to new kerneldoc syntax for named variable macro argument

The syntax without dots is available since commit 43756e347f21
("scripts/kernel-doc: Add support for named variable macro arguments").

The same HTML output is produced with and without this patch.

Link: https://lkml.kernel.org/r/20210513161702.1721039-1-j.neuschaefer@gmx.net
Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Felix Kuehling <Felix.Kuehling@amd.com>
Cc: Valentin Schneider <valentin.schneider@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/page_alloc: correct return value of populated elements if bulk array is populated

Dave Jones reported the following

This made it into 5.13 final, and completely breaks NFSD for me
(Serving tcp v3 mounts).  Existing mounts on clients hang, as do
new mounts from new clients.  Rebooting the server back to rc7
everything recovers.

The commit b3b64ebd3822 ("mm/page_alloc: do bulk array bounds check after
checking populated elements") returns the wrong value if the array is
already populated which is interpreted as an allocation failure.  Dave
reported this fixes his problem and it also passed a test running dbench
over NFS.

Link: https://lkml.kernel.org/r/20210628150219.GC3840@techsingularity.net
Fixes: b3b64ebd3822 ("mm/page_alloc: do bulk array bounds check after checking populated elements")
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Reported-by: Dave Jones <davej@codemonkey.org.uk>
Tested-by: Dave Jones <davej@codemonkey.org.uk>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: <stable@vger.kernel.org> [5.13+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/page_alloc: fix memory map initialization for descending nodes

On systems with memory nodes sorted in descending order, for instance Dell
Precision WorkStation T5500, the struct pages for higher PFNs and
respectively lower nodes, could be overwritten by the initialization of
struct pages corresponding to the holes in the memory sections.

For example for the below memory layout

[    0.245624] Early memory node ranges
[    0.248496]   node   1: [mem 0x0000000000001000-0x0000000000090fff]
[    0.251376]   node   1: [mem 0x0000000000100000-0x00000000dbdf8fff]
[    0.254256]   node   1: [mem 0x0000000100000000-0x0000001423ffffff]
[    0.257144]   node   0: [mem 0x0000001424000000-0x0000002023ffffff]

the range 0x1424000000 - 0x1428000000 in the beginning of node 0 starts in
the middle of a section and will be considered as a hole during the
initialization of the last section in node 1.

The wrong initialization of the memory map causes panic on boot when
CONFIG_DEBUG_VM is enabled.

Reorder loop order of the memory map initialization so that the outer loop
will always iterate over populated memory regions in the ascending order
and the inner loop will select the zone corresponding to the PFN range.

This way initialization of the struct pages for the memory holes will be
always done for the ranges that are actually not populated.

[akpm@linux-foundation.org: coding style fixes]

Link: https://lkml.kernel.org/r/YNXlMqBbL+tBG7yq@kernel.org
Link: https://bugzilla.kernel.org/show_bug.cgi?id=213073
Link: https://lkml.kernel.org/r/20210624062305.10940-1-rppt@kernel.org
Fixes: 0740a50b9baa ("mm/page_alloc.c: refactor initialization of struct page for holes in memory layout")
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Cc: Boris Petkov <bp@alien8.de>
Cc: Robert Shteynfeld <robert.shteynfeld@gmail.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: David Hildenbrand <david@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/gup: fix try_grab_compound_head() race with split_huge_page()

try_grab_compound_head() is used to grab a reference to a page from
get_user_pages_fast(), which is only protected against concurrent freeing
of page tables (via local_irq_save()), but not against concurrent TLB
flushes, freeing of data pages, or splitting of compound pages.

Because no reference is held to the page when try_grab_compound_head() is
called, the page may have been freed and reallocated by the time its
refcount has been elevated; therefore, once we're holding a stable
reference to the page, the caller re-checks whether the PTE still points
to the same page (with the same access rights).

The problem is that try_grab_compound_head() has to grab a reference on
the head page; but between the time we look up what the head page is and
the time we actually grab a reference on the head page, the compound page
may have been split up (either explicitly through split_huge_page() or by
freeing the compound page to the buddy allocator and then allocating its
individual order-0 pages).  If that happens, get_user_pages_fast() may end
up returning the right page but lifting the refcount on a now-unrelated
page, leading to use-after-free of pages.

To fix it: Re-check whether the pages still belong together after lifting
the refcount on the head page.  Move anything else that checks
compound_head(page) below the refcount increment.

This can't actually happen on bare-metal x86 (because there, disabling
IRQs locks out remote TLB flushes), but it can happen on virtualized x86
(e.g.  under KVM) and probably also on arm64.  The race window is pretty
narrow, and constantly allocating and shattering hugepages isn't exactly
fast; for now I've only managed to reproduce this in an x86 KVM guest with
an artificially widened timing window (by adding a loop that repeatedly
calls `inl(0x3f8 + 5)` in `try_get_compound_head()` to force VM exits, so
that PV TLB flushes are used instead of IPIs).

As requested on the list, also replace the existing VM_BUG_ON_PAGE() with
a warning and bailout.  Since the existing code only performed the BUG_ON
check on DEBUG_VM kernels, ensure that the new code also only performs the
check under that configuration - I don't want to mix two logically
separate changes together too much.  The macro VM_WARN_ON_ONCE_PAGE()
doesn't return a value on !DEBUG_VM, so wrap the whole check in an #ifdef
block.  An alternative would be to change the VM_WARN_ON_ONCE_PAGE()
definition for !DEBUG_VM such that it always returns false, but since that
would differ from the behavior of the normal WARN macros, it might be too
confusing for readers.

Link: https://lkml.kernel.org/r/20210615012014.1100672-1-jannh@google.com
Fixes: 7aef4172c795 ("mm: handle PTE-mapped tail pages in gerneric fast gup implementaiton")
Signed-off-by: Jann Horn <jannh@google.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Jan Kara <jack@suse.cz>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Linux 5.13

Revert "signal: Allow tasks to cache one sigqueue struct"

This reverts commits 4bad58ebc8bc4f20d89cff95417c9b4674769709 (and
399f8dd9a866e107639eabd3c1979cd526ca3a98, which tried to fix it).

I do not believe these are correct, and I'm about to release 5.13, so am
reverting them out of an abundance of caution.

The locking is odd, and appears broken.

On the allocation side (in __sigqueue_alloc()), the locking is somewhat
straightforward: it depends on sighand->siglock.  Since one caller
doesn't hold that lock, it further then tests 'sigqueue_flags' to avoid
the case with no locks held.

On the freeing side (in sigqueue_cache_or_free()), there is no locking
at all, and the logic instead depends on 'current' being a single
thread, and not able to race with itself.

To make things more exciting, there's also the data race between freeing
a signal and allocating one, which is handled by using WRITE_ONCE() and
READ_ONCE(), and being mutually exclusive wrt the initial state (ie
freeing will only free if the old state was NULL, while allocating will
obviously only use the value if it was non-NULL, so only one or the
other will actually act on the value).

However, while the free->alloc paths do seem mutually exclusive thanks
to just the data value dependency, it's not clear what the memory
ordering constraints are on it.  Could writes from the previous
allocation possibly be delayed and seen by the new allocation later,
causing logical inconsistencies?

So it's all very exciting and unusual.

And in particular, it seems that the freeing side is incorrect in
depending on "current" being single-threaded.  Yes, 'current' is a
single thread, but in the presense of asynchronous events even a single
thread can have data races.

And such asynchronous events can and do happen, with interrupts causing
signals to be flushed and thus free'd (for example - sending a
SIGCONT/SIGSTOP can happen from interrupt context, and can flush
previously queued process control signals).

So regardless of all the other questions about the memory ordering and
locking for this new cached allocation, the sigqueue_cache_or_free()
assumptions seem to be fundamentally incorrect.

It may be that people will show me the errors of my ways, and tell me
why this is all safe after all.  We can reinstate it if so.  But my
current belief is that the WRITE_ONCE() that sets the cached entry needs
to be a smp_store_release(), and the READ_ONCE() that finds a cached
entry needs to be a smp_load_acquire() to handle memory ordering
correctly.

And the sequence in sigqueue_cache_or_free() would need to either use a
lock or at least be interrupt-safe some way (perhaps by using something
like the percpu 'cmpxchg': it doesn't need to be SMP-safe, but like the
percpu operations it needs to be interrupt-safe).

Fixes: 399f8dd9a866 ("signal: Prevent sigqueue caching after task got released")
Fixes: 4bad58ebc8bc ("signal: Allow tasks to cache one sigqueue struct")
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Merge tag 's390-5.13-5' of git://git./linux/kernel/git/s390/linux

Pull s390 fixes from Vasily Gorbik:

 - Fix a couple of late pt_regs flags handling findings of conversion to
   generic entry.

 - Fix potential register clobbering in stack switch helper.

 - Fix thread/group masks for offline cpus.

 - Fix cleanup of mdev resources when remove callback is invoked in
   vfio-ap code.

* tag 's390-5.13-5' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux:
  s390/stack: fix possible register corruption with stack switch helper
  s390/topology: clear thread/group maps for offline cpus
  s390/vfio-ap: clean up mdev resources when remove callback invoked
  s390: clear pt_regs::flags on irq entry
  s390: fix system call restart with multiple signals