The patch titled
Subject: mm/vmscan: use PG_dropbehind instead of PG_reclaim
has been added to the -mm mm-unstable branch. Its filename is
mm-vmscan-use-pg_dropbehind-instead-of-pg_reclaim.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-vmscan-use-pg_dropbehind-instead-of-pg_reclaim.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Subject: mm/vmscan: use PG_dropbehind instead of PG_reclaim
Date: Thu, 30 Jan 2025 12:00:44 +0200
The recently introduced PG_dropbehind allows for freeing folios
immediately after writeback. Unlike PG_reclaim, it does not need vmscan
to be involved to get the folio freed.
Instead of using folio_set_reclaim(), use folio_set_dropbehind() in
pageout().
It is safe to leave PG_dropbehind on the folio if, for some reason (bug?),
the folio is not in a writeback state after ->writepage(). In these
cases, the kernel had to clear PG_reclaim as it shared a page flag bit
with PG_readahead.
Link: https://lkml.kernel.org/r/20250130100050.1868208-7-kirill.shutemov@xxxxxxxxxxxxxxx
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
Cc: Andi Shyti <andi.shyti@xxxxxxxxxxxxxxx>
Cc: Chengming Zhou <chengming.zhou@xxxxxxxxx>
Cc: Christian Brauner <brauner@xxxxxxxxxx>
Cc: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
Cc: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Cc: Dave Airlie <airlied@xxxxxxxxx>
Cc: gehao <gehao@xxxxxxxxxx>
Cc: Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx>
Cc: Jason A. Donenfeld <jason@xxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Jonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
Cc: Josef Bacik <josef@xxxxxxxxxxxxxx>
Cc: "Masami Hiramatsu (Google)" <mhiramat@xxxxxxxxxx>
Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
Cc: Mattew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Miklos Szeredi <miklos@xxxxxxxxxx>
Cc: Nhat Pham <nphamcs@xxxxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxx>
Cc: Ran Xiaokai <ran.xiaokai@xxxxxxxxxx>
Cc: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx>
Cc: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
Cc: Tvrtko Ursulin <tursulin@xxxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
Cc: Yu Zhao <yuzhao@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/vmscan.c | 9 +++------
1 file changed, 3 insertions(+), 6 deletions(-)
--- a/mm/vmscan.c~mm-vmscan-use-pg_dropbehind-instead-of-pg_reclaim
+++ a/mm/vmscan.c
@@ -692,19 +692,16 @@ static pageout_t pageout(struct folio *f
if (shmem_mapping(mapping) && folio_test_large(folio))
wbc.list = folio_list;
- folio_set_reclaim(folio);
+ folio_set_dropbehind(folio);
+
res = mapping->a_ops->writepage(&folio->page, &wbc);
if (res < 0)
handle_write_error(mapping, folio, res);
if (res == AOP_WRITEPAGE_ACTIVATE) {
- folio_clear_reclaim(folio);
+ folio_clear_dropbehind(folio);
return PAGE_ACTIVATE;
}
- if (!folio_test_writeback(folio)) {
- /* synchronous write or broken a_ops? */
- folio_clear_reclaim(folio);
- }
trace_mm_vmscan_write_folio(folio);
node_stat_add_folio(folio, NR_VMSCAN_WRITE);
return PAGE_SUCCESS;
_
Patches currently in -mm which might be from kirill.shutemov@xxxxxxxxxxxxxxx are
mm-migrate-transfer-pg_dropbehind-to-the-new-folio.patch
drm-i915-gem-convert-__shmem_writeback-to-folios.patch
drm-i915-gem-use-pg_dropbehind-instead-of-pg_reclaim.patch
mm-zswap-use-pg_dropbehind-instead-of-pg_reclaim.patch
mm-truncate-use-folio_set_dropbehind-instead-of-deactivate_file_folio.patch
mm-vmscan-use-pg_dropbehind-instead-of-pg_reclaim.patch
mm-vmscan-use-pg_dropbehind-instead-of-pg_reclaim-in-shrink_folio_list.patch
mm-mglru-check-pg_dropbehind-instead-of-pg_reclaim-in-lru_gen_folio_seq.patch
mm-remove-pg_reclaim.patch
mm-vmscan-do-not-demote-pg_dropbehind-folios.patch
mm-rename-pg_dropbehind-to-pg_reclaim.patch
