The patch titled
Subject: mm/migrate: correct nr_failed in migrate_pages_sync()
has been added to the -mm mm-unstable branch. Its filename is
mm-migrate-correct-nr_failed-in-migrate_pages_sync.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-migrate-correct-nr_failed-in-migrate_pages_sync.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: Zi Yan <ziy@xxxxxxxxxx>
Subject: mm/migrate: correct nr_failed in migrate_pages_sync()
Date: Mon, 9 Oct 2023 16:32:31 -0400
In the upstream tree, large folios can be migrated via move_pages()
syscall and there is no VM_BUG_ON in do_move_pages_to_node() but pages
left in the source page list will not be returned to LRU lists. This is
from my code inspection and I have not reproduced it on upstream tree yet.
nr_failed was missing the rc value from migrate_pages_batch() and can
cause a mismatch between migrate_pages() return value and the number of
not migrated pages, i.e., when the return value of migrate_pages() is 0,
there are still pages left in the from page list. It will happen when a
non-PMD THP large folio fails to migrate due to -ENOMEM and is split
successfully but not all the split pages are not migrated,
migrate_pages_batch() would return non-zero, but astats.nr_thp_split =3D
0. nr_failed would be 0 and returned to the caller of migrate_pages(),
but the not migrated pages are left in the from page list without being
added back to LRU lists.
Link: https://lkml.kernel.org/r/20231009203231.1715845-2-zi.yan@xxxxxxxx
Fixes: 2ef7dbb26990 ("migrate_pages: try migrate in batch asynchronously fi=
rstly")
Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
Cc: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Huang Ying <ying.huang@xxxxxxxxx>
Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/migrate.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/migrate.c~mm-migrate-correct-nr_failed-in-migrate_pages_sync
+++ a/mm/migrate.c
@@ -1834,7 +1834,7 @@ static int migrate_pages_sync(struct lis
return rc;
}
stats->nr_thp_failed += astats.nr_thp_split;
- nr_failed += astats.nr_thp_split;
+ nr_failed += rc + astats.nr_thp_split;
/*
* Fall back to migrate all failed folios one by one synchronously. All
* failed folios except split THPs will be retried, so their failure
_
Patches currently in -mm which might be from ziy@xxxxxxxxxx are
mm-migrate-correct-nr_failed-in-migrate_pages_sync.patch
