From 33fc80e2574737e6e21eecc4c1d7942370a2c752 Mon Sep 17 00:00:00 2001 From: Minchan Kim Date: Wed, 3 May 2017 14:54:17 -0700 Subject: [PATCH] mm: remove SWAP_AGAIN in ttu In 2002, [1] introduced SWAP_AGAIN. At that time, try_to_unmap_one used spin_trylock(&mm->page_table_lock) so it's really easy to contend and fail to hold a lock so SWAP_AGAIN to keep LRU status makes sense. However, now we changed it to mutex-based lock and be able to block without skip pte so there is few of small window to return SWAP_AGAIN so remove SWAP_AGAIN and just return SWAP_FAIL. [1] c48c43e, minimal rmap Link: http://lkml.kernel.org/r/1489555493-14659-7-git-send-email-minchan@kernel.org Signed-off-by: Minchan Kim Cc: Anshuman Khandual Cc: Hillf Danton Cc: Johannes Weiner Cc: Kirill A. Shutemov Cc: Michal Hocko Cc: Naoya Horiguchi Cc: Vlastimil Babka Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/rmap.c | 11 +++-------- mm/vmscan.c | 2 -- 2 files changed, 3 insertions(+), 10 deletions(-) diff --git a/mm/rmap.c b/mm/rmap.c index 45f41d4fa670..a3645d029400 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1504,13 +1504,10 @@ static int page_mapcount_is_zero(struct page *page) * Return values are: * * SWAP_SUCCESS - we succeeded in removing all mappings - * SWAP_AGAIN - we missed a mapping, try again later * SWAP_FAIL - the page is unswappable */ int try_to_unmap(struct page *page, enum ttu_flags flags) { - int ret; - struct rmap_walk_control rwc = { .rmap_one = try_to_unmap_one, .arg = (void *)flags, @@ -1530,13 +1527,11 @@ int try_to_unmap(struct page *page, enum ttu_flags flags) rwc.invalid_vma = invalid_migration_vma; if (flags & TTU_RMAP_LOCKED) - ret = rmap_walk_locked(page, &rwc); + rmap_walk_locked(page, &rwc); else - ret = rmap_walk(page, &rwc); + rmap_walk(page, &rwc); - if (!page_mapcount(page)) - ret = SWAP_SUCCESS; - return ret; + return !page_mapcount(page) ? SWAP_SUCCESS : SWAP_FAIL; } static int page_not_mapped(struct page *page) diff --git a/mm/vmscan.c b/mm/vmscan.c index cfd2651966a8..f80a54da5f7f 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1150,8 +1150,6 @@ static unsigned long shrink_page_list(struct list_head *page_list, case SWAP_FAIL: nr_unmap_fail++; goto activate_locked; - case SWAP_AGAIN: - goto keep_locked; case SWAP_SUCCESS: ; /* try to free the page below */ } -- 2.39.5