3.14-stable review patch. If anyone has any objections, please let me know.
------------------ From: Mel Gorman <[email protected]> commit 6fb81a17d21f2a138b8f424af4cf379f2b694060 upstream. When adding pages to the LRU we clear the active bit unconditionally. As the page could be reachable from other paths we cannot use unlocked operations without risk of corruption such as a parallel mark_page_accessed. This patch tests if is necessary to clear the active flag before using an atomic operation. This potentially opens a tiny race when PageActive is checked as mark_page_accessed could be called after PageActive was checked. The race already exists but this patch changes it slightly. The consequence is that that the page may be promoted to the active list that might have been left on the inactive list before the patch. It's too tiny a race and too marginal a consequence to always use atomic operations for. Signed-off-by: Mel Gorman <[email protected]> Acked-by: Johannes Weiner <[email protected]> Cc: Vlastimil Babka <[email protected]> Cc: Jan Kara <[email protected]> Cc: Michal Hocko <[email protected]> Cc: Hugh Dickins <[email protected]> Cc: Dave Hansen <[email protected]> Cc: Theodore Ts'o <[email protected]> Cc: "Paul E. McKenney" <[email protected]> Cc: Oleg Nesterov <[email protected]> Cc: Rik van Riel <[email protected]> Cc: Peter Zijlstra <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]> Signed-off-by: Mel Gorman <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- mm/swap.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) --- a/mm/swap.c +++ b/mm/swap.c @@ -597,13 +597,15 @@ static void __lru_cache_add(struct page */ void lru_cache_add_anon(struct page *page) { - ClearPageActive(page); + if (PageActive(page)) + ClearPageActive(page); __lru_cache_add(page); } void lru_cache_add_file(struct page *page) { - ClearPageActive(page); + if (PageActive(page)) + ClearPageActive(page); __lru_cache_add(page); } EXPORT_SYMBOL(lru_cache_add_file); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
