From 9ba85f5529f1110aa6d787f8f12553a713f945fc Mon Sep 17 00:00:00 2001 From: Usama Arif Date: Mon, 10 Jun 2024 15:30:37 +0100 Subject: [PATCH] mm: do not start/end writeback for pages stored in zswap Most of the work done in folio_start_writeback is reversed in folio_end_writeback. For e.g. NR_WRITEBACK and NR_ZONE_WRITE_PENDING are incremented in start_writeback and decremented in end_writeback. Calling end_writeback immediately after start_writeback (separated by folio_unlock) cancels the affect of most of the work done in start hence can be removed. There is some extra work done in folio_end_writeback, however it is incorrect/not applicable to zswap: - folio_end_writeback incorrectly increments NR_WRITTEN counter, eventhough the pages aren't written to disk, hence this change corrects this behaviour. - folio_end_writeback calls folio_rotate_reclaimable, but that only makes sense for async writeback pages, while for zswap pages are synchronously reclaimed. Link: https://lkml.kernel.org/r/20240612100109.1616626-1-usamaarif642@gmail.com Link: https://lkml.kernel.org/r/20240610143037.812955-1-usamaarif642@gmail.com Signed-off-by: Usama Arif Acked-by: Johannes Weiner Reviewed-by: Shakeel Butt Acked-by: Yosry Ahmed Reviewed-by: Chengming Zhou Suggested-by: Matthew Wilcox (Oracle) Cc: Nhat Pham Signed-off-by: Andrew Morton --- mm/page_io.c | 2 -- 1 file changed, 2 deletions(-) diff --git a/mm/page_io.c b/mm/page_io.c index f1a9cfab6e74..488ecacef84f 100644 --- a/mm/page_io.c +++ b/mm/page_io.c @@ -196,9 +196,7 @@ int swap_writepage(struct page *page, struct writeback_control *wbc) return ret; } if (zswap_store(folio)) { - folio_start_writeback(folio); folio_unlock(folio); - folio_end_writeback(folio); return 0; } if (!mem_cgroup_zswap_writeback_enabled(folio_memcg(folio))) {