The patch below does not apply to the 6.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.4.y git checkout FETCH_HEAD git cherry-pick -x 0e0e9bd5f7b9d40fd03b70092367247d52da1db0 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2023082614-choice-mongoose-0731@gregkh' --subject-prefix 'PATCH 6.4.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 0e0e9bd5f7b9d40fd03b70092367247d52da1db0 Mon Sep 17 00:00:00 2001 From: Yin Fengwei fengwei.yin@intel.com Date: Tue, 8 Aug 2023 10:09:17 +0800 Subject: [PATCH] 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

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;