The patch titled
Subject: mm: page_alloc: free pages to correct buddy list after PCP lock contention
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
mm-page_alloc-free-pages-to-correct-buddy-list-after-pcp-lock-contention.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-page_alloc-free-pages-to-correct-buddy-list-after-pcp-lock-contention.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Subject: mm: page_alloc: free pages to correct buddy list after PCP lock contention
Date: Tue, 5 Sep 2023 10:09:22 +0100
Commit 4b23a68f9536 ("mm/page_alloc: protect PCP lists with a spinlock")
returns pages to the buddy list on PCP lock contention. However, for
migratetypes that are not MIGRATE_PCPTYPES, the migratetype may have
been clobbered already for pages that are not being isolated. In
practice, this means that CMA pages may be returned to the wrong
buddy list. While this might be harmless in some cases as it is
MIGRATE_MOVABLE, the pageblock could be reassigned in rmqueue_fallback
and prevent a future CMA allocation. Lookup the PCP migratetype
against unconditionally if the PCP lock is contended.
[lecopzer.chen@xxxxxxxxxxxx: CMA-specific fix]
Link: https://lkml.kernel.org/r/20230905090922.zy7srh33rg5c3zao@xxxxxxxxxxxxxxxxxxx
Fixes: 4b23a68f9536 ("mm/page_alloc: protect PCP lists with a spinlock")
Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Reported-by: Joe Liu <joe.liu@xxxxxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_alloc.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
--- a/mm/page_alloc.c~mm-page_alloc-free-pages-to-correct-buddy-list-after-pcp-lock-contention
+++ a/mm/page_alloc.c
@@ -2428,7 +2428,13 @@ void free_unref_page(struct page *page,
free_unref_page_commit(zone, pcp, page, migratetype, order);
pcp_spin_unlock(pcp);
} else {
- free_one_page(zone, page, pfn, order, migratetype, FPI_NONE);
+ /*
+ * The page migratetype may have been clobbered for types
+ * (type >= MIGRATE_PCPTYPES && !is_migrate_isolate) so
+ * must be rechecked.
+ */
+ free_one_page(zone, page, pfn, order,
+ get_pcppage_migratetype(page), FPI_NONE);
}
pcp_trylock_finish(UP_flags);
}
_
Patches currently in -mm which might be from mgorman@xxxxxxxxxxxxxxxxxxx are
mm-page_alloc-free-pages-to-correct-buddy-list-after-pcp-lock-contention.patch
