6.12-stable review patch. If anyone has any objections, please let me know.
------------------
From: Hugh Dickins hughd@google.com
commit dad2dc9c92e0f93f33cebcb0595b8daa3d57473f upstream.
/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 Reviewed-by: Baolin Wang baolin.wang@linux.alibaba.com Tested-by: Baolin Wang baolin.wang@linux.alibaba.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- mm/shmem.c | 22 ++++++++++++---------- 1 file changed, 12 insertions(+), 10 deletions(-)
--- a/mm/shmem.c +++ b/mm/shmem.c @@ -779,6 +779,14 @@ 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. */ @@ -813,10 +821,7 @@ 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); @@ -844,8 +849,7 @@ 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); @@ -1944,10 +1948,8 @@ 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);