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>

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 54ed3eb..452c743 100644 (file)
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -78,6 +78,7 @@
 #include <linux/uio.h>
 #include <linux/ioprio.h>
 #include <linux/blk-cgroup.h>
+#include <linux/sched/mm.h>
 
 #include "loop.h"
 
@@ -516,8 +517,6 @@ static void lo_rw_aio_complete(struct kiocb *iocb, long ret, long ret2)
 {
        struct loop_cmd *cmd = container_of(iocb, struct loop_cmd, iocb);
 
-       if (cmd->css)
-               css_put(cmd->css);
        cmd->ret = ret;
        lo_rw_aio_do_completion(cmd);
 }
@@ -578,8 +577,6 @@ static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd,
        cmd->iocb.ki_complete = lo_rw_aio_complete;
        cmd->iocb.ki_flags = IOCB_DIRECT;
        cmd->iocb.ki_ioprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, 0);
-       if (cmd->css)
-               kthread_associate_blkcg(cmd->css);
 
        if (rw == WRITE)
                ret = call_write_iter(file, &cmd->iocb, &iter);
@@ -587,7 +584,6 @@ static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd,
                ret = call_read_iter(file, &cmd->iocb, &iter);
 
        lo_rw_aio_do_completion(cmd);
-       kthread_associate_blkcg(NULL);
 
        if (ret != -EIOCBQUEUED)
                cmd->iocb.ki_complete(&cmd->iocb, ret, 0);
@@ -928,7 +924,7 @@ struct loop_worker {
        struct list_head cmd_list;
        struct list_head idle_list;
        struct loop_device *lo;
-       struct cgroup_subsys_state *css;
+       struct cgroup_subsys_state *blkcg_css;
        unsigned long last_ran_at;
 };
 
@@ -957,7 +953,7 @@ static void loop_queue_work(struct loop_device *lo, struct loop_cmd *cmd)
 
        spin_lock_irq(&lo->lo_work_lock);
 
-       if (queue_on_root_worker(cmd->css))
+       if (queue_on_root_worker(cmd->blkcg_css))
                goto queue_work;
 
        node = &lo->worker_tree.rb_node;
@@ -965,10 +961,10 @@ static void loop_queue_work(struct loop_device *lo, struct loop_cmd *cmd)
        while (*node) {
                parent = *node;
                cur_worker = container_of(*node, struct loop_worker, rb_node);
-               if (cur_worker->css == cmd->css) {
+               if (cur_worker->blkcg_css == cmd->blkcg_css) {
                        worker = cur_worker;
                        break;
-               } else if ((long)cur_worker->css < (long)cmd->css) {
+               } else if ((long)cur_worker->blkcg_css < (long)cmd->blkcg_css) {
                        node = &(*node)->rb_left;
                } else {
                        node = &(*node)->rb_right;
@@ -980,13 +976,18 @@ static void loop_queue_work(struct loop_device *lo, struct loop_cmd *cmd)
        worker = kzalloc(sizeof(struct loop_worker), GFP_NOWAIT | __GFP_NOWARN);
        /*
         * In the event we cannot allocate a worker, just queue on the
-        * rootcg worker
+        * rootcg worker and issue the I/O as the rootcg
         */
-       if (!worker)
+       if (!worker) {
+               cmd->blkcg_css = NULL;
+               if (cmd->memcg_css)
+                       css_put(cmd->memcg_css);
+               cmd->memcg_css = NULL;
                goto queue_work;
+       }
 
-       worker->css = cmd->css;
-       css_get(worker->css);
+       worker->blkcg_css = cmd->blkcg_css;
+       css_get(worker->blkcg_css);
        INIT_WORK(&worker->work, loop_workfn);
        INIT_LIST_HEAD(&worker->cmd_list);
        INIT_LIST_HEAD(&worker->idle_list);
@@ -1306,7 +1307,7 @@ static int __loop_clr_fd(struct loop_device *lo, bool release)
                                idle_list) {
                list_del(&worker->idle_list);
                rb_erase(&worker->rb_node, &lo->worker_tree);
-               css_put(worker->css);
+               css_put(worker->blkcg_css);
                kfree(worker);
        }
        spin_unlock_irq(&lo->lo_work_lock);
@@ -2100,13 +2101,18 @@ static blk_status_t loop_queue_rq(struct blk_mq_hw_ctx *hctx,
        }
 
        /* always use the first bio's css */
+       cmd->blkcg_css = NULL;
+       cmd->memcg_css = NULL;
 #ifdef CONFIG_BLK_CGROUP
-       if (cmd->use_aio && rq->bio && rq->bio->bi_blkg) {
-               cmd->css = &bio_blkcg(rq->bio)->css;
-               css_get(cmd->css);
-       } else
+       if (rq->bio && rq->bio->bi_blkg) {
+               cmd->blkcg_css = &bio_blkcg(rq->bio)->css;
+#ifdef CONFIG_MEMCG
+               cmd->memcg_css =
+                       cgroup_get_e_css(cmd->blkcg_css->cgroup,
+                                       &memory_cgrp_subsys);
+#endif
+       }
 #endif
-               cmd->css = NULL;
        loop_queue_work(lo, cmd);
 
        return BLK_STS_OK;
@@ -2118,13 +2124,28 @@ static void loop_handle_cmd(struct loop_cmd *cmd)
        const bool write = op_is_write(req_op(rq));
        struct loop_device *lo = rq->q->queuedata;
        int ret = 0;
+       struct mem_cgroup *old_memcg = NULL;
 
        if (write && (lo->lo_flags & LO_FLAGS_READ_ONLY)) {
                ret = -EIO;
                goto failed;
        }
 
+       if (cmd->blkcg_css)
+               kthread_associate_blkcg(cmd->blkcg_css);
+       if (cmd->memcg_css)
+               old_memcg = set_active_memcg(
+                       mem_cgroup_from_css(cmd->memcg_css));
+
        ret = do_req_filebacked(lo, rq);
+
+       if (cmd->blkcg_css)
+               kthread_associate_blkcg(NULL);
+
+       if (cmd->memcg_css) {
+               set_active_memcg(old_memcg);
+               css_put(cmd->memcg_css);
+       }
  failed:
        /* complete non-aio request */
        if (!cmd->use_aio || ret) {
@@ -2203,7 +2224,7 @@ static void loop_free_idle_workers(struct timer_list *timer)
                        break;
                list_del(&worker->idle_list);
                rb_erase(&worker->rb_node, &lo->worker_tree);
-               css_put(worker->css);
+               css_put(worker->blkcg_css);
                kfree(worker);
        }
        if (!list_empty(&lo->idle_worker_list))

diff --git a/drivers/block/loop.h b/drivers/block/loop.h
index f81c01b..1988899 100644 (file)
--- a/drivers/block/loop.h
+++ b/drivers/block/loop.h
@@ -77,7 +77,8 @@ struct loop_cmd {
        long ret;
        struct kiocb iocb;
        struct bio_vec *bvec;
-       struct cgroup_subsys_state *css;
+       struct cgroup_subsys_state *blkcg_css;
+       struct cgroup_subsys_state *memcg_css;
 };
 
 /* Support for loadable transfer modules */

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 3cc18c2..1de3859 100644 (file)
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -1230,6 +1230,12 @@ static inline struct mem_cgroup *get_mem_cgroup_from_mm(struct mm_struct *mm)
        return NULL;
 }
 
+static inline
+struct mem_cgroup *mem_cgroup_from_css(struct cgroup_subsys_state *css)
+{
+       return NULL;
+}
+
 static inline void mem_cgroup_put(struct mem_cgroup *memcg)
 {
 }

diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 21ecc6e..9cc8c3a 100644 (file)
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -577,6 +577,7 @@ out_unlock:
        rcu_read_unlock();
        return css;
 }
+EXPORT_SYMBOL_GPL(cgroup_get_e_css);
 
 static void cgroup_get_live(struct cgroup *cgrp)
 {

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 8f3244e..4ee243c 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -78,6 +78,7 @@ struct mem_cgroup *root_mem_cgroup __read_mostly;
 
 /* Active memory cgroup to use from an interrupt context */
 DEFINE_PER_CPU(struct mem_cgroup *, int_active_memcg);
+EXPORT_PER_CPU_SYMBOL_GPL(int_active_memcg);
 
 /* Socket memory accounting disabled? */
 static bool cgroup_memory_nosocket;