4.8-stable review patch. If anyone has any objections, please let me know.
------------------
From: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
commit c3901e722b2975666f42748340df798114742d6d upstream.
When memory_failure() runs on a thp tail page after pmd is split, we
trigger the following VM_BUG_ON_PAGE():
page:ffffd7cd819b0040 count:0 mapcount:0 mapping: (null) index:0x1
flags: 0x1fffc000400000(hwpoison)
page dumped because: VM_BUG_ON_PAGE(!page_count(p))
------------[ cut here ]------------
kernel BUG at /src/linux-dev/mm/memory-failure.c:1132!
memory_failure() passed refcount and page lock from tail page to head
page, which is not needed because we can pass any subpage to
split_huge_page().
Fixes: 61f5d698cc97 ("mm: re-enable THP")
Link: http://lkml.kernel.org/r/1477961577-7183-1-git-send-email-n-horiguchi@xxxxxxxxxxxxx
Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
mm/memory-failure.c | 12 +++++-------
1 file changed, 5 insertions(+), 7 deletions(-)
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1112,10 +1112,10 @@ int memory_failure(unsigned long pfn, in
}
if (!PageHuge(p) && PageTransHuge(hpage)) {
- lock_page(hpage);
- if (!PageAnon(hpage) || unlikely(split_huge_page(hpage))) {
- unlock_page(hpage);
- if (!PageAnon(hpage))
+ lock_page(p);
+ if (!PageAnon(p) || unlikely(split_huge_page(p))) {
+ unlock_page(p);
+ if (!PageAnon(p))
pr_err("Memory failure: %#lx: non anonymous thp\n",
pfn);
else
@@ -1126,9 +1126,7 @@ int memory_failure(unsigned long pfn, in
put_hwpoison_page(p);
return -EBUSY;
}
- unlock_page(hpage);
- get_hwpoison_page(p);
- put_hwpoison_page(hpage);
+ unlock_page(p);
VM_BUG_ON_PAGE(!page_count(p), p);
hpage = compound_head(p);
}
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