From: Baolin Wang Date: Fri, 17 Oct 2025 07:53:07 +0000 (+0800) Subject: mm: vmscan: simplify the logic for activating dirty file folios X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=04d5378bb26dc240ea3b2a1c23b0d4c75c147e61;p=users%2Fjedix%2Flinux-maple.git mm: vmscan: simplify the logic for activating dirty file folios After commit 6b0dfabb3555 ("fs: Remove aops->writepage"), we no longer attempt to write back filesystem folios through reclaim. However, in the shrink_folio_list() function, there still remains some logic related to writeback control of dirty file folios. The original logic was that, for direct reclaim, or when folio_test_reclaim() is false, or the PGDAT_DIRTY flag is not set, the dirty file folios would be directly activated to avoid being scanned again; otherwise, it will try to writeback the dirty file folios. However, since we can no longer perform writeback on dirty folios, the dirty file folios will still be activated. Additionally, under the original logic, if we continue to try writeback dirty file folios, we will also check the references flag, sc->may_writepage, and may_enter_fs(), which may result in dirty file folios being left in the inactive list. This is unreasonable. Even if these dirty folios are scanned again, we still cannot clean them. Therefore, the checks on these dirty file folios appear to be redundant and can be removed. Dirty file folios should be directly moved to the active list to avoid being scanned again. Since we set the PG_reclaim flag for the dirty folios, once the writeback is completed, they will be moved back to the tail of the inactive list to be retried for quick reclaim. Link: https://lkml.kernel.org/r/ba5c49955fd93c6850bcc19abf0e02e1573768aa.1760687075.git.baolin.wang@linux.alibaba.com Signed-off-by: Baolin Wang Cc: David Hildenbrand Cc: Hugh Dickins Cc: Johannes Weiner Cc: Lorenzo Stoakes Cc: Matthew Wilcox (Oracle) Cc: Michal Hocko Cc: Qi Zheng Cc: Shakeel Butt Signed-off-by: Andrew Morton --- diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 7fb7331c5725..4398e027f450 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -1060,10 +1060,6 @@ struct zone { } ____cacheline_internodealigned_in_smp; enum pgdat_flags { - PGDAT_DIRTY, /* reclaim scanning has recently found - * many dirty file pages at the tail - * of the LRU. - */ PGDAT_WRITEBACK, /* reclaim scanning has recently found * many pages under writeback */ diff --git a/mm/vmscan.c b/mm/vmscan.c index 320831e78b92..92f4ca99b73c 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1387,21 +1387,7 @@ retry: mapping = folio_mapping(folio); if (folio_test_dirty(folio)) { - /* - * Only kswapd can writeback filesystem folios - * to avoid risk of stack overflow. But avoid - * injecting inefficient single-folio I/O into - * flusher writeback as much as possible: only - * write folios when we've encountered many - * dirty folios, and when we've already scanned - * the rest of the LRU for clean folios and see - * the same dirty folios again (with the reclaim - * flag set). - */ - if (folio_is_file_lru(folio) && - (!current_is_kswapd() || - !folio_test_reclaim(folio) || - !test_bit(PGDAT_DIRTY, &pgdat->flags))) { + if (folio_is_file_lru(folio)) { /* * Immediately reclaim when written back. * Similar in principle to folio_deactivate() @@ -1410,7 +1396,8 @@ retry: */ node_stat_mod_folio(folio, NR_VMSCAN_IMMEDIATE, nr_pages); - folio_set_reclaim(folio); + if (!folio_test_reclaim(folio)) + folio_set_reclaim(folio); goto activate_locked; } @@ -6105,11 +6092,6 @@ again: if (sc->nr.writeback && sc->nr.writeback == sc->nr.taken) set_bit(PGDAT_WRITEBACK, &pgdat->flags); - /* Allow kswapd to start writing pages during reclaim.*/ - if (sc->nr.unqueued_dirty && - sc->nr.unqueued_dirty == sc->nr.file_taken) - set_bit(PGDAT_DIRTY, &pgdat->flags); - /* * If kswapd scans pages marked for immediate * reclaim and under writeback (nr_immediate), it @@ -6850,7 +6832,6 @@ static void clear_pgdat_congested(pg_data_t *pgdat) clear_bit(LRUVEC_NODE_CONGESTED, &lruvec->flags); clear_bit(LRUVEC_CGROUP_CONGESTED, &lruvec->flags); - clear_bit(PGDAT_DIRTY, &pgdat->flags); clear_bit(PGDAT_WRITEBACK, &pgdat->flags); }