The patch titled
Subject: mm: filemap_unaccount_folio() large skip mapcount fixup
has been added to the -mm tree. Its filename is
mm-filemap_unaccount_folio-large-skip-mapcount-fixup.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-filemap_unaccount_folio-large-skip-mapcount-fixup.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-filemap_unaccount_folio-large-skip-mapcount-fixup.patch
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------------------------------------------------------
From: Hugh Dickins <hughd@xxxxxxxxxx>
Subject: mm: filemap_unaccount_folio() large skip mapcount fixup
The page_mapcount_reset() when folio_mapped() while mapping_exiting() was
devised long before there were huge or compound pages in the cache. It is
still valid for small pages, but not at all clear what's right to check
and reset on large pages. Just don't try when folio_test_large().
Link: https://lkml.kernel.org/r/879c4426-4122-da9c-1a86-697f2c9a083@xxxxxxxxxx
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/filemap.c | 26 +++++++++++++-------------
1 file changed, 13 insertions(+), 13 deletions(-)
--- a/mm/filemap.c~mm-filemap_unaccount_folio-large-skip-mapcount-fixup
+++ a/mm/filemap.c
@@ -152,25 +152,25 @@ static void filemap_unaccount_folio(stru
VM_BUG_ON_FOLIO(folio_mapped(folio), folio);
if (!IS_ENABLED(CONFIG_DEBUG_VM) && unlikely(folio_mapped(folio))) {
- int mapcount;
-
pr_alert("BUG: Bad page cache in process %s pfn:%05lx\n",
current->comm, folio_pfn(folio));
dump_page(&folio->page, "still mapped when deleted");
dump_stack();
add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
- mapcount = page_mapcount(&folio->page);
- if (mapping_exiting(mapping) &&
- folio_ref_count(folio) >= mapcount + 2) {
- /*
- * All vmas have already been torn down, so it's
- * a good bet that actually the folio is unmapped,
- * and we'd prefer not to leak it: if we're wrong,
- * some other bad page check should catch it later.
- */
- page_mapcount_reset(&folio->page);
- folio_ref_sub(folio, mapcount);
+ if (mapping_exiting(mapping) && !folio_test_large(folio)) {
+ int mapcount = page_mapcount(&folio->page);
+
+ if (folio_ref_count(folio) >= mapcount + 2) {
+ /*
+ * All vmas have already been torn down, so it's
+ * a good bet that actually the page is unmapped
+ * and we'd rather not leak it: if we're wrong,
+ * another bad page check should catch it later.
+ */
+ page_mapcount_reset(&folio->page);
+ folio_ref_sub(folio, mapcount);
+ }
}
}
_
Patches currently in -mm which might be from hughd@xxxxxxxxxx are
mm-fs-delete-pf_swapwrite.patch
tmpfs-support-for-file-creation-time-fix.patch
shmem-mapping_set_exiting-to-help-mapped-resilience.patch
mm-_install_special_mapping-apply-vm_locked_clear_mask.patch
mm-thp-refix-__split_huge_pmd_locked-for-migration-pmd.patch
mm-thp-clearpagedoublemap-in-first-page_add_file_rmap.patch
mm-delete-__clearpagewaiters.patch
mm-filemap_unaccount_folio-large-skip-mapcount-fixup.patch
mm-thp-fix-nr_file_mapped-accounting-in-page__file_rmap.patch
