From: Miaohe Lin Subject: mm/vmscan: add a comment about MADV_FREE pages check in folio_check_dirty_writeback Patch series "A few cleanup and fixup patches for vmscan This series contains a few patches to remove obsolete comment, introduce helper to remove duplicated code and so no. Also we take all base pages of THP into account in rare race condition. More details can be found in the respective changelogs. This patch (of 6): The MADV_FREE pages check in folio_check_dirty_writeback is a bit hard to follow. Add a comment to make the code clear. Link: https://lkml.kernel.org/r/20220425111232.23182-2-linmiaohe@huawei.com Suggested-by: Huang, Ying Signed-off-by: Miaohe Lin Reviewed-by: Christoph Hellwig Reviewed-by: Oscar Salvador Cc: Joonsoo Kim Signed-off-by: Andrew Morton --- mm/vmscan.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) --- a/mm/vmscan.c~mm-vmscan-add-a-comment-about-madv_free-pages-check-in-folio_check_dirty_writeback +++ a/mm/vmscan.c @@ -1435,7 +1435,10 @@ static void folio_check_dirty_writeback( /* * Anonymous pages are not handled by flushers and must be written - * from reclaim context. Do not stall reclaim based on them + * from reclaim context. Do not stall reclaim based on them. + * MADV_FREE anonymous pages are put into inactive file list too. + * They could be mistakenly treated as file lru. So further anon + * test is needed. */ if (!folio_is_file_lru(folio) || (folio_test_anon(folio) && !folio_test_swapbacked(folio))) { _