mm, memory_failure: Teach memory_failure() about dev_pagemap pages

mce: Uncorrected hardware memory error in user-access at af34214200
    {1}[Hardware Error]: It has been corrected by h/w and requires no further action
    mce: [Hardware Error]: Machine check events logged
    {1}[Hardware Error]: event severity: corrected
    Memory failure: 0xaf34214: reserved kernel page still referenced by 1 users
    [..]
    Memory failure: 0xaf34214: recovery action for reserved kernel page: Failed
    mce: Memory error not recovered

In contrast to typical memory, dev_pagemap pages may be dax mapped. With
dax there is no possibility to map in another page dynamically since dax
establishes 1:1 physical address to file offset associations. Also
dev_pagemap pages associated with NVDIMM / persistent memory devices can
internal remap/repair addresses with poison. While memory_failure()
assumes that it can discard typical poisoned pages and keep them
unmapped indefinitely, dev_pagemap pages may be returned to service
after the error is cleared.

Teach memory_failure() to detect and handle MEMORY_DEVICE_HOST
dev_pagemap pages that have poison consumed by userspace. Mark the
memory as UC instead of unmapping it completely to allow ongoing access
via the device driver (nd_pmem). Later, nd_pmem will grow support for
marking the page back to WB when the error is cleared.

Cc: Jan Kara <jack@suse.cz>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>

diff --git a/include/linux/mm.h b/include/linux/mm.h
index a0fbb9f..374e5e9 100644 (file)
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2725,6 +2725,7 @@ enum mf_action_page_type {
        MF_MSG_TRUNCATED_LRU,
        MF_MSG_BUDDY,
        MF_MSG_BUDDY_2ND,
+       MF_MSG_DAX,
        MF_MSG_UNKNOWN,
 };
 

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 8a81680..32a644d 100644 (file)
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -55,6 +55,7 @@
 #include <linux/hugetlb.h>
 #include <linux/memory_hotplug.h>
 #include <linux/mm_inline.h>
+#include <linux/memremap.h>
 #include <linux/kfifo.h>
 #include <linux/ratelimit.h>
 #include "internal.h"
@@ -263,6 +264,40 @@ void shake_page(struct page *p, int access)
 }
 EXPORT_SYMBOL_GPL(shake_page);
 
+static unsigned long dev_pagemap_mapping_shift(struct page *page,
+               struct vm_area_struct *vma)
+{
+       unsigned long address = vma_address(page, vma);
+       pgd_t *pgd;
+       p4d_t *p4d;
+       pud_t *pud;
+       pmd_t *pmd;
+       pte_t *pte;
+
+       pgd = pgd_offset(vma->vm_mm, address);
+       if (!pgd_present(*pgd))
+               return 0;
+       p4d = p4d_offset(pgd, address);
+       if (!p4d_present(*p4d))
+               return 0;
+       pud = pud_offset(p4d, address);
+       if (!pud_present(*pud))
+               return 0;
+       if (pud_devmap(*pud))
+               return PUD_SHIFT;
+       pmd = pmd_offset(pud, address);
+       if (!pmd_present(*pmd))
+               return 0;
+       if (pmd_devmap(*pmd))
+               return PMD_SHIFT;
+       pte = pte_offset_map(pmd, address);
+       if (!pte_present(*pte))
+               return 0;
+       if (pte_devmap(*pte))
+               return PAGE_SHIFT;
+       return 0;
+}
+
 /*
  * Failure handling: if we can't find or can't kill a process there's
  * not much we can do. We just print a message and ignore otherwise.
@@ -292,7 +327,10 @@ static void add_to_kill(struct task_struct *tsk, struct page *p,
        }
        tk->addr = page_address_in_vma(p, vma);
        tk->addr_valid = 1;
-       tk->size_shift = compound_order(compound_head(p)) + PAGE_SHIFT;
+       if (is_zone_device_page(p))
+               tk->size_shift = dev_pagemap_mapping_shift(p, vma);
+       else
+               tk->size_shift = compound_order(compound_head(p)) + PAGE_SHIFT;
 
        /*
         * In theory we don't have to kill when the page was
@@ -300,7 +338,7 @@ static void add_to_kill(struct task_struct *tsk, struct page *p,
         * likely very rare kill anyways just out of paranoia, but use
         * a SIGKILL because the error is not contained anymore.
         */
-       if (tk->addr == -EFAULT) {
+       if (tk->addr == -EFAULT || tk->size_shift == 0) {
                pr_info("Memory failure: Unable to find user space address %lx in %s\n",
                        page_to_pfn(p), tsk->comm);
                tk->addr_valid = 0;
@@ -514,6 +552,7 @@ static const char * const action_page_types[] = {
        [MF_MSG_TRUNCATED_LRU]          = "already truncated LRU page",
        [MF_MSG_BUDDY]                  = "free buddy page",
        [MF_MSG_BUDDY_2ND]              = "free buddy page (2nd try)",
+       [MF_MSG_DAX]                    = "dax page",
        [MF_MSG_UNKNOWN]                = "unknown page",
 };
 
@@ -1111,6 +1150,83 @@ out:
        return res;
 }
 
+static int memory_failure_dev_pagemap(unsigned long pfn, int flags,
+               struct dev_pagemap *pgmap)
+{
+       struct page *page = pfn_to_page(pfn);
+       const bool unmap_success = true;
+       unsigned long size = 0;
+       struct to_kill *tk;
+       LIST_HEAD(tokill);
+       int rc = -EBUSY;
+       loff_t start;
+
+       /*
+        * Prevent the inode from being freed while we are interrogating
+        * the address_space, typically this would be handled by
+        * lock_page(), but dax pages do not use the page lock. This
+        * also prevents changes to the mapping of this pfn until
+        * poison signaling is complete.
+        */
+       if (!dax_lock_mapping_entry(page))
+               goto out;
+
+       if (hwpoison_filter(page)) {
+               rc = 0;
+               goto unlock;
+       }
+
+       switch (pgmap->type) {
+       case MEMORY_DEVICE_PRIVATE:
+       case MEMORY_DEVICE_PUBLIC:
+               /*
+                * TODO: Handle HMM pages which may need coordination
+                * with device-side memory.
+                */
+               goto unlock;
+       default:
+               break;
+       }
+
+       /*
+        * Use this flag as an indication that the dax page has been
+        * remapped UC to prevent speculative consumption of poison.
+        */
+       SetPageHWPoison(page);
+
+       /*
+        * Unlike System-RAM there is no possibility to swap in a
+        * different physical page at a given virtual address, so all
+        * userspace consumption of ZONE_DEVICE memory necessitates
+        * SIGBUS (i.e. MF_MUST_KILL)
+        */
+       flags |= MF_ACTION_REQUIRED | MF_MUST_KILL;
+       collect_procs(page, &tokill, flags & MF_ACTION_REQUIRED);
+
+       list_for_each_entry(tk, &tokill, nd)
+               if (tk->size_shift)
+                       size = max(size, 1UL << tk->size_shift);
+       if (size) {
+               /*
+                * Unmap the largest mapping to avoid breaking up
+                * device-dax mappings which are constant size. The
+                * actual size of the mapping being torn down is
+                * communicated in siginfo, see kill_proc()
+                */
+               start = (page->index << PAGE_SHIFT) & ~(size - 1);
+               unmap_mapping_range(page->mapping, start, start + size, 0);
+       }
+       kill_procs(&tokill, flags & MF_MUST_KILL, !unmap_success, pfn, flags);
+       rc = 0;
+unlock:
+       dax_unlock_mapping_entry(page);
+out:
+       /* drop pgmap ref acquired in caller */
+       put_dev_pagemap(pgmap);
+       action_result(pfn, MF_MSG_DAX, rc ? MF_FAILED : MF_RECOVERED);
+       return rc;
+}
+
 /**
  * memory_failure - Handle memory failure of a page.
  * @pfn: Page Number of the corrupted page
@@ -1133,6 +1249,7 @@ int memory_failure(unsigned long pfn, int flags)
        struct page *p;
        struct page *hpage;
        struct page *orig_head;
+       struct dev_pagemap *pgmap;
        int res;
        unsigned long page_flags;
 
@@ -1145,6 +1262,10 @@ int memory_failure(unsigned long pfn, int flags)
                return -ENXIO;
        }
 
+       pgmap = get_dev_pagemap(pfn, NULL);
+       if (pgmap)
+               return memory_failure_dev_pagemap(pfn, flags, pgmap);
+
        p = pfn_to_page(pfn);
        if (PageHuge(p))
                return memory_failure_hugetlb(pfn, flags);