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thp: fix memory-failure hugetlbfs vs THP collision 

hugetlbfs was changed to allow memory failure to migrate the hugetlbfs
pages and that broke THP as split_huge_page was then called on hugetlbfs
pages too.

compound_head/order was also run unsafe on THP pages that can be splitted
at any time.

All compound_head() invocations in memory-failure.c that are run on pages
that aren't pinned and that can be freed and reused from under us (while
compound_head is running) are buggy because compound_head can return a
dangling pointer, but I'm not fixing this as this is a generic
memory-failure bug not specific to THP but it applies to hugetlbfs too, so
I can fix it later after THP is merged upstream.

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Andrea Arcangeli 2011-01-13 15:47:16 -08:00 committed by Linus Torvalds
parent 14d1a55cd2
commit 91600e9e59
2 changed files with 2 additions and 2 deletions
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2
mm/memory-failure.c
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@ -386,7 +386,7 @@ static void collect_procs_anon(struct page *page, struct list_head *to_kill,
struct task_struct *tsk; struct task_struct *tsk;
struct anon_vma *av; struct anon_vma *av;
if (unlikely(split_huge_page(page))) if (!PageHuge(page) && unlikely(split_huge_page(page)))
return; return;
read_lock(&tasklist_lock); read_lock(&tasklist_lock);
av = page_lock_anon_vma(page); av = page_lock_anon_vma(page);

2
mm/rmap.c
View File

@ -1430,7 +1430,7 @@ int try_to_unmap(struct page *page, enum ttu_flags flags)
int ret; int ret;
BUG_ON(!PageLocked(page)); BUG_ON(!PageLocked(page));
BUG_ON(PageTransHuge(page)); VM_BUG_ON(!PageHuge(page) && PageTransHuge(page));
if (unlikely(PageKsm(page))) if (unlikely(PageKsm(page)))
ret = try_to_unmap_ksm(page, flags); ret = try_to_unmap_ksm(page, flags);