Commit 07e8c82b5eff ("madvise: convert madvise_cold_or_pageout_pte_range() to use folios") replaced the page_mapcount() with folio_mapcount() to check whether the folio is shared by other mapping.
It's not correct for large folio. 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.
Fixes: 07e8c82b5eff ("madvise: convert madvise_cold_or_pageout_pte_range() to use folios") Cc: stable@vger.kernel.org Signed-off-by: Yin Fengwei fengwei.yin@intel.com Reviewed-by: Yu Zhao yuzhao@google.com Reviewed-by: Ryan Roberts ryan.roberts@arm.com --- mm/madvise.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/mm/madvise.c b/mm/madvise.c index 1d7933933e31..49af35e2d99a 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -383,7 +383,7 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd, folio = pfn_folio(pmd_pfn(orig_pmd));
/* Do not interfere with other mappings of this folio */ - if (folio_mapcount(folio) != 1) + if (folio_estimated_sharers(folio) != 1) goto huge_unlock;
if (pageout_anon_only_filter && !folio_test_anon(folio)) @@ -459,7 +459,7 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd, if (folio_test_large(folio)) { int err;
- if (folio_mapcount(folio) != 1) + if (folio_estimated_sharers(folio) != 1) break; if (pageout_anon_only_filter && !folio_test_anon(folio)) break;