On 08.11.23 18:15, Stefan Roesch wrote:
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.
Signed-off-by: Stefan Roesch <shr@xxxxxxxxxxxx>
Co-debugged-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
---
mm/huge_memory.c | 16 +++++++++-------
1 file changed, 9 insertions(+), 7 deletions(-)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 064fbd90822b4..874000f97bfc1 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2737,13 +2737,15 @@ int split_huge_page_to_list(struct page *page, struct list_head *list)
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);
+ }
Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
Yes, that's the current state: update these counters only for
(traditional, IOW PMD-sized) THP. What we'll do with non-pmd-sized THP
remains to be discussed (Ryan had some ideas).
--
Cheers,
David / dhildenb
