From: Christoph Hellwig <hch@lst.de>
To: Jens Axboe <axboe@kernel.dk>,
Christian Brauner <brauner@kernel.org>,
"Darrick J. Wong" <djwong@kernel.org>,
Carlos Maiolino <cem@kernel.org>
Cc: Tal Zussman <tz2294@columbia.edu>,
Anuj Gupta <anuj20.g@samsung.com>,
linux-block@vger.kernel.org, linux-xfs@vger.kernel.org,
linux-fsdevel@vger.kernel.org
Subject: lazy bounce buffering for checksummed reads v3
Date: Wed, 9 Sep 2026 09:08:49 +0300 [thread overview]
Message-ID: <20260909060924.1102037-1-hch@lst.de> (raw)
Hi all,
this series improves performance and resource usage for reads from
devices that require stable pages due to checksumming on XFS.
Currently XFS unconditionally bounce buffers reads on such devices to
prevent user modifications to the buffer from corrupting the data,
leading to checksum failures.
This uses DRAM bandwidth and CPU cycles for copies that are not needed
most of the time, and due to the use of a bio_vec for the bounce
buffer to smaller than wanted and unaligned I/O sizes when using 4k
user pages (i.e. 1MB-4k I/O).
This series addresses this by reading without the bounce buffer first,
and then only allocating a buffer and reading into that again on an
initial checksum failure. To accommodate for rare (or hypothetical?)
applications that have legitimate needs to frequently modify in-flight
buffers, a sysfs know is provided to revert to the old behavior.
NOTE/QUESTION TO SUBSYSTEM MAINTAINERS: The patches in this series are
split over 3 subsystems, and I'd love to hear from the maintainers
about their preferences for merging this.
The baseline of this series is mainline with the
"misc block PI / bounce buffering fixes" series.
A git tree is available to help with the review here:
git://git.infradead.org/users/hch/misc.git lazy-bounce
Gitweb:
https://git.infradead.org/?p=users/hch/misc.git;a=shortlog;h=refs/heads/lazy-bounce
Changes since v2:
- break out of bio_iov_iter_get_pages when bi_size reaches maxlen
- various fixes for pre-existing issues pointed out by Sashiko
- generate zone PI a bit earlier
- initialize the csum dir in sysfs unconditionally to protect against the
rather theoretical case of the flag changing underneath us
- redo sysfs initialization order to avoid a cleanup bug
- use NOFS allocations in xfs_read_bounce_and_resubmit
- rework bio setup for reissue to not leave land mines for other uses
- fix commit message typos
- fix comment typos
Changes since v1:
- rebase on 7.3rc-1 and xfs for-next, which has the bio complete in
task support merged
- remove the now unused IOMAP_DIO_BOUNCE support for reads
- fix compilation with integrity disabled
- make I/O size limitation actually work
- clear REQ_POLLED when bounce buffering
- use sysfs string match helpers to allow non -n echo
next reply other threads:[~2026-09-09 6:09 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-09 6:08 Christoph Hellwig [this message]
2026-09-09 6:08 ` [PATCH 01/16] block: split bio_iov_iter_bounce_write Christoph Hellwig
2026-09-09 6:08 ` [PATCH 02/16] block: export fs_bio_integrity_{alloc,free} Christoph Hellwig
2026-09-09 6:08 ` [PATCH 03/16] block: add a bio_prepare_reissue helper Christoph Hellwig
2026-09-09 16:05 ` Darrick J. Wong
2026-09-09 6:08 ` [PATCH 04/16] iomap: respect maximum I/O size in iomap_dio_bio_iter_one Christoph Hellwig
2026-09-09 6:08 ` [PATCH 05/16] iomap: add a iomap_ioend_flags helper Christoph Hellwig
2026-09-09 6:08 ` [PATCH 06/16] iomap: add a IOMAP_IOEND_INTEGRITY flag Christoph Hellwig
2026-09-09 6:08 ` [PATCH 07/16] iomap,xfs: move T10 PI handling for direct I/O into ->submit_io Christoph Hellwig
2026-09-09 6:08 ` [PATCH 08/16] xfs: move PI generation into xfs_submit_zoned_bio Christoph Hellwig
2026-09-09 16:06 ` Darrick J. Wong
2026-09-09 6:08 ` [PATCH 09/16] block,iomap: fix protection information verification with initial bvec offset Christoph Hellwig
2026-09-09 6:08 ` [PATCH 10/16] iomap: better read bounce buffering support Christoph Hellwig
2026-09-09 6:09 ` [PATCH 11/16] xfs: use BIO_COMPLETE_IN_TASK for bounce buffered read I/Os Christoph Hellwig
2026-09-09 6:09 ` [PATCH 12/16] iomap,xfs: move integrity verification to the file system Christoph Hellwig
2026-09-09 6:09 ` [PATCH 13/16] xfs: add support for lazy direct read bounce buffering Christoph Hellwig
2026-09-09 6:09 ` [PATCH 14/16] xfs: add error injection for lazy " Christoph Hellwig
2026-09-09 6:09 ` [PATCH 15/16] xfs: log a message at mount time when using integrity protection Christoph Hellwig
2026-09-09 6:09 ` [PATCH 16/16] block,iomap: remove the old read side bounce buffering support Christoph Hellwig
2026-09-09 16:15 ` Darrick J. Wong
2026-09-10 20:50 ` lazy bounce buffering for checksummed reads v3 Jens Axboe
2026-09-10 20:51 ` Jens Axboe
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