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mm: hwpoison: fix thp split handling in memory_failure()

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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: 61f5d698cc ("mm: re-enable THP")
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Naoya Horiguchi <[email protected]>
Cc: <[email protected]>	[4.5+]
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Naoya Horiguchi authored and Linus Torvalds committed 2016-11-11 08:12:37 -08:00
1 parent dd111be691
commit c3901e722b
1 file changed
+5 -7
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mm/memory-failure.c
+5 -7
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@@ -1112,10 +1112,10 @@ int memory_failure(unsigned long pfn, int trapno, int flags)
}
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, int trapno, int flags)
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);
}