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Fri, 28 Apr 2023 12:41:45 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id rSPkDwm/S2TZAgAAMHmgww (envelope-from ); Fri, 28 Apr 2023 12:41:45 +0000 Received: by quack3.suse.cz (Postfix, from userid 1000) id BB9FBA0729; Fri, 28 Apr 2023 14:41:44 +0200 (CEST) From: Jan Kara To: Cc: , Lorenzo Stoakes , Andrew Morton , Christoph Hellwig , David Hildenbrand , Jan Kara Subject: [PATCH] mm: Do not reclaim private data from pinned page Date: Fri, 28 Apr 2023 14:41:40 +0200 Message-Id: <20230428124140.30166-1-jack@suse.cz> X-Mailer: git-send-email 2.35.3 MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=1542; i=jack@suse.cz; h=from:subject; bh=VhR45B065VmS3m1QAwuuueeTtqJBvGh05kRL+9zQOvI=; b=owEBbQGS/pANAwAIAZydqgc/ZEDZAcsmYgBkS7791o0ClFedJaG0n1Kh5ZzrZe52VXmFvp4V0/vf 5sh7IQ2JATMEAAEIAB0WIQSrWdEr1p4yirVVKBycnaoHP2RA2QUCZEu+/QAKCRCcnaoHP2RA2UW6CA DWSYFyTiHP43msHY1/1+T7TJ8aLmgLu5LtlBRE5ZgyiwZ6JwvZJHxT5TkpRnRBpqa7my2w4ZG/VK04 FY7uPFYTbaJf9VeVjXNUwJqvc89uWyRWpiYHrCciQgFpJygMwsk6v1emH/jqPp9rJSr+2gsTYOrWj0 O5QYdk2ri6C6BM79qUUDCEoCzPG3+F61Ijnkmzs9mCReEwWaWWFgvrVA+5LrS2wa7EWTbVaMqJzgfo GvW3Z1vdcvyYWOwlafWggIrfhGMSUha67FY9ZAXJAsucjKQk45sjPbMhVGM77HkwmORWE6FEK8wG6K 3pnp54kpEHrnwTlsDAAQf/td2WcE5l X-Developer-Key: i=jack@suse.cz; 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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 Signed-off-by: Jan Kara Reviewed-by: Matthew Wilcox (Oracle) Reviewed-by: Lorenzo Stoakes Reviewed-by: Christoph Hellwig Reviewed-by: John Hubbard Acked-by: David Hildenbrand Acked-by: Peter Xu --- mm/vmscan.c | 10 ++++++++++ 1 file changed, 10 insertions(+) This was the non-controversial part of my series [1] dealing with pinned pages in filesystems. It is already a win as it avoids crashes in the filesystem and we can drop workarounds for this in ext4. Can we merge it please? [1] https://lore.kernel.org/all/20230209121046.25360-1-jack@suse.cz/ diff --git a/mm/vmscan.c b/mm/vmscan.c index bf3eedf0209c..401a379ea99a 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1901,6 +1901,16 @@ static unsigned int shrink_folio_list(struct list_head *folio_list, } } + /* + * 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)) { /*