This is a note to let you know that I've just added the patch titled
mm: fix for negative counter: nr_file_hugepages
to the 6.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
mm-fix-for-negative-counter-nr_file_hugepages.patch
and it can be found in the queue-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From a48d5bdc877b85201e42cef9c2fdf5378164c23a Mon Sep 17 00:00:00 2001
From: Stefan Roesch <shr@xxxxxxxxxxxx>
Date: Mon, 6 Nov 2023 10:19:18 -0800
Subject: mm: fix for negative counter: nr_file_hugepages
From: Stefan Roesch <shr@xxxxxxxxxxxx>
commit a48d5bdc877b85201e42cef9c2fdf5378164c23a upstream.
While qualifiying the 6.4 release, the following warning was detected in
messages:
vmstat_refresh: nr_file_hugepages -15664
The warning is caused by the incorrect updating of the NR_FILE_THPS
counter in the function split_huge_page_to_list. The if case is checking
for folio_test_swapbacked, but the else case is missing the check for
folio_test_pmd_mappable. The other functions that manipulate the counter
like __filemap_add_folio and filemap_unaccount_folio have the
corresponding check.
I have a test case, which reproduces the problem. It can be found here:
https://github.com/sroeschus/testcase/blob/main/vmstat_refresh/madv.c
The test case reproduces on an XFS filesystem. Running the same test
case on a BTRFS filesystem does not reproduce the problem.
AFAIK version 6.1 until 6.6 are affected by this problem.
[akpm@xxxxxxxxxxxxxxxxxxxx: whitespace fix]
[shr@xxxxxxxxxxxx: test for folio_test_pmd_mappable()]
Link: https://lkml.kernel.org/r/20231108171517.2436103-1-shr@xxxxxxxxxxxx
Link: https://lkml.kernel.org/r/20231106181918.1091043-1-shr@xxxxxxxxxxxx
Signed-off-by: Stefan Roesch <shr@xxxxxxxxxxxx>
Co-debugged-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Reviewed-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
Reviewed-by: Yang Shi <shy828301@xxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
mm/huge_memory.c | 16 +++++++++-------
1 file changed, 9 insertions(+), 7 deletions(-)
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2737,13 +2737,15 @@ int split_huge_page_to_list(struct page
int nr = folio_nr_pages(folio);
xas_split(&xas, folio, folio_order(folio));
- if (folio_test_swapbacked(folio)) {
- __lruvec_stat_mod_folio(folio, NR_SHMEM_THPS,
- -nr);
- } else {
- __lruvec_stat_mod_folio(folio, NR_FILE_THPS,
- -nr);
- filemap_nr_thps_dec(mapping);
+ if (folio_test_pmd_mappable(folio)) {
+ if (folio_test_swapbacked(folio)) {
+ __lruvec_stat_mod_folio(folio,
+ NR_SHMEM_THPS, -nr);
+ } else {
+ __lruvec_stat_mod_folio(folio,
+ NR_FILE_THPS, -nr);
+ filemap_nr_thps_dec(mapping);
+ }
}
}
Patches currently in stable-queue which might be from shr@xxxxxxxxxxxx are
queue-6.6/mm-fix-for-negative-counter-nr_file_hugepages.patch
