From d17be2d9ff6c689fd70d2d451153d613508a56ae Mon Sep 17 00:00:00 2001 From: Miaohe Lin Date: Thu, 2 Sep 2021 14:59:39 -0700 Subject: mm/vmscan: remove the PageDirty check after MADV_FREE pages are page_ref_freezed Patch series "Cleanups for vmscan", v2. This series contains cleanups to remove unneeded return value, misleading setting and so on. Also this remove the PageDirty check after MADV_FREE pages are page_ref_freezed. More details can be found in the respective changelogs. This patch (of 4): If the MADV_FREE pages are redirtied before they could be reclaimed, put the pages back to anonymous LRU list by setting SwapBacked flag and the pages will be reclaimed in normal swapout way. But as Yu Zhao pointed out, "The page has only one reference left, which is from the isolation. After the caller puts the page back on lru and drops the reference, the page will be freed anyway. It doesn't matter which lru it goes." So we don't bother checking PageDirty here. [Yu Zhao's comment is also quoted in the code.] Link: https://lkml.kernel.org/r/20210717065911.61497-1-linmiaohe@huawei.com Link: https://lkml.kernel.org/r/20210717065911.61497-2-linmiaohe@huawei.com Signed-off-by: Miaohe Lin Reviewed-by: Yu Zhao Cc: Johannes Weiner Cc: Vlastimil Babka Cc: Michal Hocko Cc: Jens Axboe Cc: Joonsoo Kim Cc: Alex Shi Cc: Alistair Popple Cc: Matthew Wilcox Cc: Minchan Kim Cc: David Hildenbrand Cc: Shaohua Li Cc: Hillf Danton Cc: John Hubbard Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/vmscan.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index 2255025f1891..044207d0bb66 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1732,11 +1732,14 @@ retry: /* follow __remove_mapping for reference */ if (!page_ref_freeze(page, 1)) goto keep_locked; - if (PageDirty(page)) { - page_ref_unfreeze(page, 1); - goto keep_locked; - } - + /* + * The page has only one reference left, which is + * from the isolation. After the caller puts the + * page back on lru and drops the reference, the + * page will be freed anyway. It doesn't matter + * which lru it goes. So we don't bother checking + * PageDirty here. + */ count_vm_event(PGLAZYFREED); count_memcg_page_event(page, PGLAZYFREED); } else if (!mapping || !__remove_mapping(mapping, page, true, -- cgit v1.2.3