| Message ID | 20231108171517.2436103-1-shr@devkernel.io (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [v3] mm: Fix for negative counter: nr_file_hugepages | expand |
On Wed, Nov 08, 2023 at 09:15:17AM -0800, 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@devkernel.io> > Co-debugged-by: Johannes Weiner <hannes@cmpxchg.org> > Acked-by: Johannes Weiner <hannes@cmpxchg.org> > Cc: stable@vger.kernel.org Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
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@devkernel.io> > Co-debugged-by: Johannes Weiner <hannes@cmpxchg.org> > Acked-by: Johannes Weiner <hannes@cmpxchg.org> > Cc: stable@vger.kernel.org > --- > 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@redhat.com> 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).
On Wed, Nov 8, 2023 at 9:15 AM Stefan Roesch <shr@devkernel.io> 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@devkernel.io> > Co-debugged-by: Johannes Weiner <hannes@cmpxchg.org> > Acked-by: Johannes Weiner <hannes@cmpxchg.org> > Cc: stable@vger.kernel.org Reviewed-by: Yang Shi <shy828301@gmail.com> > --- > 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); > + } > } > } > > > base-commit: ffc253263a1375a65fa6c9f62a893e9767fbebfa > -- > 2.39.3 > >
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); + } } }