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thp, mlock: do not mlock PTE-mapped file huge pages

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As with anon THP, we only mlock file huge pages if we can prove that the
page is not mapped with PTE.  This way we can avoid mlock leak into
non-mlocked vma on split.

We rely on PageDoubleMap() under lock_page() to check if the the page
may be PTE mapped.  PG_double_map is set by page_add_file_rmap() when
the page mapped with PTEs.

Link: http://lkml.kernel.org/r/1466021202-61880-21-git-send-email-kirill.shutemov@linux.intel.com
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Kirill A. Shutemov
2016-07-26 15:25:53 -07:00
committed by Linus Torvalds
parent baa355fd33
commit 9a73f61bdb
5 changed files with 54 additions and 10 deletions
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2
mm/page_alloc.c
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@@ -1007,6 +1007,8 @@ static __always_inline bool free_pages_prepare(struct page *page,
VM_BUG_ON_PAGE(compound && compound_order(page) != order, page);
if (compound)
ClearPageDoubleMap(page);
for (i = 1; i < (1 << order); i++) {
if (compound)
bad += free_tail_pages_check(page, page + i);