From: hch <hch@lst.de>
To: Johannes Thumshirn <Johannes.Thumshirn@wdc.com>
Cc: "Darrick J. Wong" <djwong@kernel.org>, hch <hch@lst.de>,
Jan Kara <jack@suse.cz>, Keith Busch <kbusch@kernel.org>,
Dave Chinner <david@fromorbit.com>,
Carlos Maiolino <cem@kernel.org>,
Christian Brauner <brauner@kernel.org>,
"Martin K. Petersen" <martin.petersen@oracle.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-xfs@vger.kernel.org" <linux-xfs@vger.kernel.org>,
"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
"linux-raid@vger.kernel.org" <linux-raid@vger.kernel.org>,
"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>
Subject: Re: fall back from direct to buffered I/O when stable writes are required
Date: Thu, 6 Nov 2025 13:49:00 +0100 [thread overview]
Message-ID: <20251106124900.GA6144@lst.de> (raw)
In-Reply-To: <9530fca4-418d-4415-b365-cad04a06449b@wdc.com>
On Thu, Nov 06, 2025 at 09:50:10AM +0000, Johannes Thumshirn wrote:
> On 11/5/25 10:44 PM, Darrick J. Wong wrote:
> > Just out of curiosity -- is qemu itself mutating the buffers that it is
> > passing down to the lower levels via dio? Or is it a program in the
> > guest that's mutating buffers that are submitted for dio, which then get
> > zerocopied all the way down to the hypervisor?
>
> If my memory serves me right it is the guest (or at least can be). I
> remember a bug report on btrfs where a Windows guest had messed up
> checksums because of modifying inflight I/O.
qemu passes I/O through, so yes it is guest controller. Windows is most
famous, but the Linux swap code can trigger it easily too.
next prev parent reply other threads:[~2025-11-06 12:49 UTC|newest]
Thread overview: 61+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-10-29 7:15 fall back from direct to buffered I/O when stable writes are required Christoph Hellwig
2025-10-29 7:15 ` [PATCH 1/4] fs: replace FOP_DIO_PARALLEL_WRITE with a fmode bits Christoph Hellwig
2025-10-29 16:01 ` Darrick J. Wong
2025-11-04 7:00 ` Nirjhar Roy (IBM)
2025-11-05 14:04 ` Christoph Hellwig
2025-11-11 9:44 ` Christian Brauner
2025-10-29 7:15 ` [PATCH 2/4] fs: return writeback errors for IOCB_DONTCACHE in generic_write_sync Christoph Hellwig
2025-10-29 16:01 ` Darrick J. Wong
2025-10-29 16:37 ` Christoph Hellwig
2025-10-29 18:12 ` Darrick J. Wong
2025-10-30 5:59 ` Christoph Hellwig
2025-11-04 12:04 ` Nirjhar Roy (IBM)
2025-11-04 15:53 ` Christoph Hellwig
2025-10-29 7:15 ` [PATCH 3/4] xfs: use IOCB_DONTCACHE when falling back to buffered writes Christoph Hellwig
2025-10-29 15:57 ` Darrick J. Wong
2025-11-04 12:33 ` Nirjhar Roy (IBM)
2025-11-04 15:52 ` Christoph Hellwig
2025-10-29 7:15 ` [PATCH 4/4] xfs: fallback to buffered I/O for direct I/O when stable writes are required Christoph Hellwig
2025-10-29 15:53 ` Darrick J. Wong
2025-10-29 16:35 ` Christoph Hellwig
2025-10-29 21:23 ` Qu Wenruo
2025-10-30 5:58 ` Christoph Hellwig
2025-10-30 6:37 ` Qu Wenruo
2025-10-30 6:49 ` Christoph Hellwig
2025-10-30 6:53 ` Qu Wenruo
2025-10-30 6:55 ` Christoph Hellwig
2025-10-30 7:14 ` Qu Wenruo
2025-10-30 7:17 ` Christoph Hellwig
2025-11-10 13:38 ` Nirjhar Roy (IBM)
2025-11-10 13:59 ` Christoph Hellwig
2025-11-12 7:13 ` Nirjhar Roy (IBM)
2025-10-29 15:58 ` fall back from direct to buffered " Bart Van Assche
2025-10-29 16:14 ` Darrick J. Wong
2025-10-29 16:33 ` Christoph Hellwig
2025-10-30 11:20 ` Dave Chinner
2025-10-30 12:00 ` Geoff Back
2025-10-30 12:54 ` Jan Kara
2025-10-30 14:35 ` Christoph Hellwig
2025-10-30 22:02 ` Dave Chinner
2025-10-30 14:33 ` Christoph Hellwig
2025-10-30 23:18 ` Dave Chinner
2025-10-31 13:00 ` Christoph Hellwig
2025-10-31 15:57 ` Keith Busch
2025-10-31 16:47 ` Christoph Hellwig
2025-11-03 11:14 ` Jan Kara
2025-11-03 12:21 ` Christoph Hellwig
2025-11-03 22:47 ` Keith Busch
2025-11-04 23:38 ` Darrick J. Wong
2025-11-05 14:11 ` Christoph Hellwig
2025-11-05 21:44 ` Darrick J. Wong
2025-11-06 9:50 ` Johannes Thumshirn
2025-11-06 12:49 ` hch [this message]
2025-11-12 14:18 ` Ming Lei
2025-11-12 14:38 ` hch
2025-11-13 17:39 ` Kevin Wolf
2025-11-14 5:39 ` Christoph Hellwig
2025-11-14 9:29 ` Kevin Wolf
2025-11-14 12:01 ` Christoph Hellwig
2025-11-14 12:31 ` Kevin Wolf
2025-11-14 15:36 ` Christoph Hellwig
2025-11-14 16:55 ` Kevin Wolf
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