The patch titled Subject: madvise:madvise_free_pte_range(): don't use mapcount() against large folio for sharing check has been added to the -mm mm-hotfixes-unstable branch. Its filename is madvise-madvise_free_pte_range-dont-use-mapcount-against-large-folio-for-sharing-check.patch
This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...
This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days
------------------------------------------------------ From: Yin Fengwei fengwei.yin@intel.com 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@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 ---
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@intel.com are
madvise-madvise_cold_or_pageout_pte_range-dont-use-mapcount-against-large-folio-for-sharing-check.patch madvise-madvise_free_huge_pmd-dont-use-mapcount-against-large-folio-for-sharing-check.patch madvise-madvise_free_pte_range-dont-use-mapcount-against-large-folio-for-sharing-check.patch 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