+ mm-do-not-reclaim-private-data-from-pinned-page.patch added to mm-hotfixes-unstable branch

+ mm-do-not-reclaim-private-data-from-pinned-page.patch added to mm-hotfixes-unstable branch

[Andrew Morton]

The patch titled
     Subject: mm: do not reclaim private data from pinned page
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     mm-do-not-reclaim-private-data-from-pinned-page.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-do-not-reclaim-private-data-from-pinned-page.patch

This patch will later appear in the mm-hotfixes-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Jan Kara <jack@suse.cz>
Subject: mm: do not reclaim private data from pinned page
Date: Fri, 28 Apr 2023 14:41:40 +0200

If the page is pinned, there's no point in trying to reclaim it. 
Furthermore if the page is from the page cache we don't want to reclaim
fs-private data from the page because the pinning process may be writing
to the page at any time and reclaiming fs private info on a dirty page can
upset the filesystem (see link below).

Link: https://lore.kernel.org/linux-mm/20180103100430.GE4911@quack2.suse.cz
Link: https://lkml.kernel.org/r/20230428124140.30166-1-jack@suse.cz
Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Lorenzo Stoakes <lstoakes@gmail.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: Peter Xu <peterx@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/vmscan.c |   10 ++++++++++
 1 file changed, 10 insertions(+)

--- a/mm/vmscan.c~mm-do-not-reclaim-private-data-from-pinned-page
+++ a/mm/vmscan.c
@@ -1967,6 +1967,16 @@ retry:
 			}
 		}
 
+		/*
+		 * Folio is unmapped now so it cannot be newly pinned anymore.
+		 * No point in trying to reclaim folio if it is pinned.
+		 * Furthermore we don't want to reclaim underlying fs metadata
+		 * if the folio is pinned and thus potentially modified by the
+		 * pinning process as that may upset the filesystem.
+		 */
+		if (folio_maybe_dma_pinned(folio))
+			goto activate_locked;
+
 		mapping = folio_mapping(folio);
 		if (folio_test_dirty(folio)) {
 			/*
_

Patches currently in -mm which might be from jack@suse.cz are

mm-do-not-reclaim-private-data-from-pinned-page.patch