From: Jan Kara <jack@suse.cz>
To: Matthew Wilcox <willy@infradead.org>
Cc: Jan Kara <jack@suse.cz>, Baokun Li <libaokun1@huawei.com>,
linux-mm@kvack.org, linux-ext4@vger.kernel.org, tytso@mit.edu,
adilger.kernel@dilger.ca, akpm@linux-foundation.org,
ritesh.list@gmail.com, linux-kernel@vger.kernel.org,
yi.zhang@huawei.com, yangerkun@huawei.com, yukuai3@huawei.com
Subject: Re: [PATCH -RFC 0/2] mm/ext4: avoid data corruption when extending DIO write race with buffered read
Date: Tue, 12 Dec 2023 15:25:43 +0100 [thread overview]
Message-ID: <20231212142543.jrortgje22traesa@quack3> (raw)
In-Reply-To: <ZXfjXZWK4HlJi6pg@casper.infradead.org>
On Tue 12-12-23 04:36:45, Matthew Wilcox wrote:
> On Wed, Dec 06, 2023 at 08:37:57PM +0100, Jan Kara wrote:
> > Within the same page buffered reads and writes should be consistent because
> > they are synchronized by the page lock. However once reads and writes
> > involve multiple pages, there is no serialization so you can get contents
> > of some pages before write and some pages after being written. However this
> > doesn't seem to be your particular case here. I just wanted to point out
> > that in general even buffered reads vs writes are not fully consistent.
>
> Buffered reads don't take the page/folio lock. We only use the folio
> lock to avoid reading stale data from the page cache while we're
> fetching the data from storage. Once the uptodate flag is set on the
> folio, we never take the folio lock for reads.
Right, I've noticed once I've reread the code but thanks for correction
anyway. :)
Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
next prev parent reply other threads:[~2023-12-12 14:25 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-12-02 9:14 Baokun Li
2023-12-02 9:14 ` [PATCH -RFC 1/2] mm: " Baokun Li
2023-12-02 9:14 ` [PATCH -RFC 2/2] ext4: " Baokun Li
2023-12-04 12:11 ` [PATCH -RFC 0/2] mm/ext4: " Jan Kara
2023-12-04 13:50 ` Baokun Li
2023-12-04 14:41 ` Jan Kara
2023-12-05 12:50 ` Baokun Li
2023-12-06 19:37 ` Jan Kara
2023-12-07 3:01 ` Baokun Li
2023-12-07 14:15 ` Baokun Li
2023-12-11 17:49 ` Jan Kara
2023-12-12 2:15 ` Baokun Li
2023-12-12 4:36 ` Matthew Wilcox
2023-12-12 14:25 ` Jan Kara [this message]
2023-12-05 4:17 ` Theodore Ts'o
2023-12-05 13:19 ` Baokun Li
2023-12-06 21:55 ` Theodore Ts'o
2023-12-07 6:41 ` Baokun Li
2023-12-06 8:35 ` Dave Chinner
2023-12-06 9:02 ` Christoph Hellwig
2023-12-06 10:34 ` Dave Chinner
2023-12-06 12:20 ` Christoph Hellwig
2023-12-06 11:57 ` Baokun Li
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