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mm/migrate: check-before-clear PageSwapCache

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With the page flag sanitization patchset, an invalid usage of
ClearPageSwapCache() is detected in migration_page_copy().
migrate_page_copy() is shared by both normal and hugepage (both thp and
hugetlb) code path, so let's check PageSwapCache() and clear it if it's
set to avoid misuse of the invalid clear operation.

Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Acked-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:
Naoya Horiguchi 2015-04-15 16:13:15 -07:00 committed by Linus Torvalds
parent 8d63d99a5d
commit b3b3a99c53
1 changed files with 2 additions and 1 deletions
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mm/migrate.c
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@ -537,7 +537,8 @@ void migrate_page_copy(struct page *newpage, struct page *page)
* Please do not reorder this without considering how mm/ksm.c's
* get_ksm_page() depends upon ksm_migrate_page() and PageSwapCache().
*/
ClearPageSwapCache(page);
if (PageSwapCache(page))
ClearPageSwapCache(page);
ClearPagePrivate(page);
set_page_private(page, 0);