linux-kernel - [PATCH 5/8] mm/vmscan: Use PG_dropbehind instead of PG

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Message-ID: <20250113093453.1932083-6-kirill.shutemov@linux.intel.com>
Date: Mon, 13 Jan 2025 11:34:50 +0200
From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To: Andrew Morton <akpm@...ux-foundation.org>,
	"Matthew Wilcox (Oracle)" <willy@...radead.org>,
	Jens Axboe <axboe@...nel.dk>
Cc: "Jason A. Donenfeld" <Jason@...c4.com>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Andi Shyti <andi.shyti@...ux.intel.com>,
	Chengming Zhou <chengming.zhou@...ux.dev>,
	Christian Brauner <brauner@...nel.org>,
	Christophe Leroy <christophe.leroy@...roup.eu>,
	Dan Carpenter <dan.carpenter@...aro.org>,
	David Airlie <airlied@...il.com>,
	David Hildenbrand <david@...hat.com>,
	Hao Ge <gehao@...inos.cn>,
	Jani Nikula <jani.nikula@...ux.intel.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
	Josef Bacik <josef@...icpanda.com>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Miklos Szeredi <miklos@...redi.hu>,
	Nhat Pham <nphamcs@...il.com>,
	Oscar Salvador <osalvador@...e.de>,
	Ran Xiaokai <ran.xiaokai@....com.cn>,
	Rodrigo Vivi <rodrigo.vivi@...el.com>,
	Simona Vetter <simona@...ll.ch>,
	Steven Rostedt <rostedt@...dmis.org>,
	Tvrtko Ursulin <tursulin@...ulin.net>,
	Vlastimil Babka <vbabka@...e.cz>,
	Yosry Ahmed <yosryahmed@...gle.com>,
	Yu Zhao <yuzhao@...gle.com>,
	intel-gfx@...ts.freedesktop.org,
	dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org,
	linux-mm@...ck.org,
	linux-trace-kernel@...r.kernel.org
Subject: [PATCH 5/8] mm/vmscan: Use PG_dropbehind instead of PG_reclaim

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.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
---
 mm/vmscan.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index a099876fa029..d15f80333d6b 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -692,19 +692,16 @@ static pageout_t pageout(struct folio *folio, struct address_space *mapping,
 		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;
-- 
2.45.2