diff options
| author | Stefan Roesch <shr@devkernel.io> | 2023-11-06 10:19:18 -0800 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2023-11-15 15:30:09 -0800 |
| commit | a48d5bdc877b85201e42cef9c2fdf5378164c23a (patch) | |
| tree | 44701b53045094e87655f1e425c1f03b8fab88a3 /mm | |
| parent | edf14544324dd036183fafe372fe5709708bdddd (diff) | |
| download | lwn-a48d5bdc877b85201e42cef9c2fdf5378164c23a.tar.gz lwn-a48d5bdc877b85201e42cef9c2fdf5378164c23a.zip | |
mm: fix for negative counter: nr_file_hugepages
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@linux-foundation.org: whitespace fix]
[shr@devkernel.io: test for folio_test_pmd_mappable()]
Link: https://lkml.kernel.org/r/20231108171517.2436103-1-shr@devkernel.io
Link: https://lkml.kernel.org/r/20231106181918.1091043-1-shr@devkernel.io
Signed-off-by: Stefan Roesch <shr@devkernel.io>
Co-debugged-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/huge_memory.c | 16 |
1 files changed, 9 insertions, 7 deletions
diff --git a/mm/huge_memory.c b/mm/huge_memory.c index f31f02472396..4f542444a91f 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2769,13 +2769,15 @@ 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); + } } } |