The quilt patch titled
Subject: madvise:madvise_free_pte_range(): don't use mapcount() against large folio for sharing check
has been removed from the -mm tree. Its filename was
madvise-madvise_free_pte_range-dont-use-mapcount-against-large-folio-for-sharing-check.patch
This patch was dropped because it was merged into the mm-hotfixes-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------
From: Yin Fengwei <fengwei.yin@xxxxxxxxx>
Subject: madvise:madvise_free_pte_range(): don't use mapcount() against large folio for sharing check
Date: Tue, 8 Aug 2023 10:09:17 +0800
Commit 98b211d6415f ("madvise: convert madvise_free_pte_range() to use a
folio") replaced the page_mapcount() with folio_mapcount() to check
whether the folio is shared by other mapping.
It's not correct for large folios. folio_mapcount() returns the total
mapcount of large folio which is not suitable to detect whether the folio
is shared.
Use folio_estimated_sharers() which returns a estimated number of shares.
That means it's not 100% correct. It should be OK for madvise case here.
User-visible effects is that the THP is skipped when user call madvise.
But the correct behavior is THP should be split and processed then.
NOTE: this change is a temporary fix to reduce the user-visible effects
before the long term fix from David is ready.
Link: https://lkml.kernel.org/r/20230808020917.2230692-4-fengwei.yin@xxxxxxxxx
Fixes: 98b211d6415f ("madvise: convert madvise_free_pte_range() to use a folio")
Signed-off-by: Yin Fengwei <fengwei.yin@xxxxxxxxx>
Reviewed-by: Yu Zhao <yuzhao@xxxxxxxxxx>
Reviewed-by: Ryan Roberts <ryan.roberts@xxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Vishal Moola (Oracle) <vishal.moola@xxxxxxxxx>
Cc: Yang Shi <shy828301@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/madvise.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/madvise.c~madvise-madvise_free_pte_range-dont-use-mapcount-against-large-folio-for-sharing-check
+++ a/mm/madvise.c
@@ -680,7 +680,7 @@ static int madvise_free_pte_range(pmd_t
if (folio_test_large(folio)) {
int err;
- if (folio_mapcount(folio) != 1)
+ if (folio_estimated_sharers(folio) != 1)
break;
if (!folio_trylock(folio))
break;
_
Patches currently in -mm which might be from fengwei.yin@xxxxxxxxx are
filemap-add-filemap_map_folio_range.patch
rmap-add-folio_add_file_rmap_range.patch
mm-convert-do_set_pte-to-set_pte_range.patch
filemap-batch-pte-mappings.patch
