linux-kernel - [PATCH] mm: fix execution order in alloc_contig_range

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Message-Id: <20260105133250.763076-1-suhua.tanke@gmail.com>
Date: Mon,  5 Jan 2026 21:32:50 +0800
From: Hua Su <suhua.tanke@...il.com>
To: akpm@...ux-foundation.org,
	vbabka@...e.cz,
	surenb@...gle.com,
	mhocko@...e.com,
	jackmanb@...gle.com,
	hannes@...xchg.org,
	ziy@...dia.com,
	suhua.tanke@...il.com
Cc: linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Hua Su <huasu@...omi.com>
Subject: [PATCH] mm: fix execution order in alloc_contig_range_noprof

Fix the execution order issue in alloc_contig_range_noprof where
drain_all_pages was called after start_isolate_page_range, which
may be lead to race conditions.

Based on community patches commit ec6e8c7e0314 ("mm, page_alloc:
disable pcplists during memory offline") and commit d479960e44f27
("mm: disable LRU pagevec during the migration temporarily"), we
disable pcplists and LRU cache before page isolation to ensure no
pages are left in per-cpu lists during isolation.

Signed-off-by: Hua Su <huasu@...omi.com>
Signed-off-by: Hua Su <suhua.tanke@...il.com>
---
 mm/page_alloc.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 6a47443c48ff..d08f929ca64c 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -6815,8 +6815,6 @@ static int __alloc_contig_migrate_range(struct compact_control *cc,
 		.reason = MR_CONTIG_RANGE,
 	};
 
-	lru_cache_disable();
-
 	while (pfn < end || !list_empty(&cc->migratepages)) {
 		if (fatal_signal_pending(current)) {
 			ret = -EINTR;
@@ -6850,7 +6848,6 @@ static int __alloc_contig_migrate_range(struct compact_control *cc,
 			break;
 	}
 
-	lru_cache_enable();
 	if (ret < 0) {
 		if (!(cc->gfp_mask & __GFP_NOWARN) && ret == -EBUSY)
 			alloc_contig_dump_pages(&cc->migratepages);
@@ -6973,6 +6970,9 @@ int alloc_contig_range_noprof(unsigned long start, unsigned long end,
 	if (__alloc_contig_verify_gfp_mask(gfp_mask, (gfp_t *)&cc.gfp_mask))
 		return -EINVAL;
 
+	zone_pcp_disable(cc.zone);
+	lru_cache_disable();
+
 	/*
 	 * What we do here is we mark all pageblocks in range as
 	 * MIGRATE_ISOLATE.  Because pageblock and max order pages may
@@ -6998,8 +6998,6 @@ int alloc_contig_range_noprof(unsigned long start, unsigned long end,
 	if (ret)
 		goto done;
 
-	drain_all_pages(cc.zone);
-
 	/*
 	 * In case of -EBUSY, we'd like to know which page causes problem.
 	 * So, just fall through. test_pages_isolated() has a tracepoint
@@ -7076,6 +7074,8 @@ int alloc_contig_range_noprof(unsigned long start, unsigned long end,
 		     start, end, outer_start, outer_end);
 	}
 done:
+	lru_cache_enable();
+	zone_pcp_enable(cc.zone);
 	undo_isolate_page_range(start, end);
 	return ret;
 }
-- 
2.34.1