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[172.10.233.147]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-2ef31715ba8sm1997649a91.13.2024.12.04.22.50.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 04 Dec 2024 22:50:17 -0800 (PST) Date: Wed, 4 Dec 2024 22:50:06 -0800 (PST) From: Hugh Dickins To: Andrew Morton cc: Baolin Wang , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH hotfix] mm: shmem: fix ShmemHugePages at swapout Message-ID: <5ba477c8-a569-70b5-923e-09ab221af45b@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" /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). Fixes: 809bc86517cc ("mm: shmem: support large folio swap out") Signed-off-by: Hugh Dickins Cc: stable@vger.kernel.org Reviewed-by: Baolin Wang Reviewed-by: Shakeel Butt Reviewed-by: Yosry Ahmed Tested-by: Baolin Wang --- mm/shmem.c | 22 ++++++++++++---------- 1 file changed, 12 insertions(+), 10 deletions(-) diff --git a/mm/shmem.c b/mm/shmem.c index ccb9629a0f70..f6fb053ac50d 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -787,6 +787,14 @@ static bool shmem_huge_global_enabled(struct inode *in= ode, pgoff_t index, } #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ =20 +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(struct folio *folio, 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 +=3D nr; unlock: xas_unlock_irq(&xas); @@ -852,8 +857,7 @@ static void shmem_delete_from_page_cache(struct folio *= folio, void *radswap) error =3D shmem_replace_entry(mapping, folio->index, folio, radswap); folio->mapping =3D NULL; mapping->nrpages -=3D 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 folio **foliop= , gfp_t gfp, } 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); =20 --=20 2.43.0