The patch titled Subject: mm: shmem: fix ShmemHugePages at swapout has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-shmem-fix-shmemhugepages-at-swapout.patch
This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...
This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days
------------------------------------------------------ From: Hugh Dickins hughd@google.com Subject: mm: shmem: fix ShmemHugePages at swapout Date: Wed, 4 Dec 2024 22:50:06 -0800 (PST)
/proc/meminfo ShmemHugePages has been showing overlarge amounts (more than Shmem) after swapping out THPs: we forgot to update NR_SHMEM_THPS.
Add shmem_update_stats(), to avoid repetition, and risk of making that mistake again: the call from shmem_delete_from_page_cache() is the bugfix; the call from shmem_replace_folio() is reassuring, but not really a bugfix (replace corrects misplaced swapin readahead, but huge swapin readahead would be a mistake).
Link: https://lkml.kernel.org/r/5ba477c8-a569-70b5-923e-09ab221af45b@google.com Fixes: 809bc86517cc ("mm: shmem: support large folio swap out") Signed-off-by: Hugh Dickins hughd@google.com Reviewed-by: Shakeel Butt shakeel.butt@linux.dev Reviewed-by: Yosry Ahmed yosryahmed@google.com Cc: Baolin Wang baolin.wang@linux.alibaba.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---
mm/shmem.c | 22 ++++++++++++---------- 1 file changed, 12 insertions(+), 10 deletions(-)
--- a/mm/shmem.c~mm-shmem-fix-shmemhugepages-at-swapout +++ a/mm/shmem.c @@ -787,6 +787,14 @@ static bool shmem_huge_global_enabled(st } #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
+static void shmem_update_stats(struct folio *folio, int nr_pages) +{ + if (folio_test_pmd_mappable(folio)) + __lruvec_stat_mod_folio(folio, NR_SHMEM_THPS, nr_pages); + __lruvec_stat_mod_folio(folio, NR_FILE_PAGES, nr_pages); + __lruvec_stat_mod_folio(folio, NR_SHMEM, nr_pages); +} + /* * Somewhat like filemap_add_folio, but error if expected item has gone. */ @@ -821,10 +829,7 @@ static int shmem_add_to_page_cache(struc xas_store(&xas, folio); if (xas_error(&xas)) goto unlock; - if (folio_test_pmd_mappable(folio)) - __lruvec_stat_mod_folio(folio, NR_SHMEM_THPS, nr); - __lruvec_stat_mod_folio(folio, NR_FILE_PAGES, nr); - __lruvec_stat_mod_folio(folio, NR_SHMEM, nr); + shmem_update_stats(folio, nr); mapping->nrpages += nr; unlock: xas_unlock_irq(&xas); @@ -852,8 +857,7 @@ static void shmem_delete_from_page_cache error = shmem_replace_entry(mapping, folio->index, folio, radswap); folio->mapping = NULL; mapping->nrpages -= nr; - __lruvec_stat_mod_folio(folio, NR_FILE_PAGES, -nr); - __lruvec_stat_mod_folio(folio, NR_SHMEM, -nr); + shmem_update_stats(folio, -nr); xa_unlock_irq(&mapping->i_pages); folio_put_refs(folio, nr); BUG_ON(error); @@ -1969,10 +1973,8 @@ static int shmem_replace_folio(struct fo } if (!error) { mem_cgroup_replace_folio(old, new); - __lruvec_stat_mod_folio(new, NR_FILE_PAGES, nr_pages); - __lruvec_stat_mod_folio(new, NR_SHMEM, nr_pages); - __lruvec_stat_mod_folio(old, NR_FILE_PAGES, -nr_pages); - __lruvec_stat_mod_folio(old, NR_SHMEM, -nr_pages); + shmem_update_stats(new, nr_pages); + shmem_update_stats(old, -nr_pages); } xa_unlock_irq(&swap_mapping->i_pages);
_
Patches currently in -mm which might be from hughd@google.com are
mm-shmem-fix-shmemhugepages-at-swapout.patch