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authorYin Fengwei <fengwei.yin@intel.com>2023-08-08 05:09:17 +0300
committerAndrew Morton <akpm@linux-foundation.org>2023-08-25 00:59:46 +0300
commit0e0e9bd5f7b9d40fd03b70092367247d52da1db0 (patch)
tree3a3412be3cd5884a6d5b50adc44cc14b52ec6569 /mm
parent20b18aada1856b2ce0512b087a8681342af73e60 (diff)
downloadlinux-0e0e9bd5f7b9d40fd03b70092367247d52da1db0.tar.xz
madvise:madvise_free_pte_range(): don't use mapcount() against large folio for sharing check
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@intel.com Fixes: 98b211d6415f ("madvise: convert madvise_free_pte_range() to use a folio") Signed-off-by: Yin Fengwei <fengwei.yin@intel.com> Reviewed-by: Yu Zhao <yuzhao@google.com> Reviewed-by: Ryan Roberts <ryan.roberts@arm.com> Cc: David Hildenbrand <david@redhat.com> Cc: Kefeng Wang <wangkefeng.wang@huawei.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Minchan Kim <minchan@kernel.org> Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com> Cc: Yang Shi <shy828301@gmail.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/madvise.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/mm/madvise.c b/mm/madvise.c
index 46802b4cf65a..ec30f48f8f2e 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -680,7 +680,7 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr,
if (folio_test_large(folio)) {
int err;
- if (folio_mapcount(folio) != 1)
+ if (folio_estimated_sharers(folio) != 1)
break;
if (!folio_trylock(folio))
break;