From: Christoph Hellwig <hch@lst.de>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>,
linux-fsdevel@vger.kernel.org, Jens Axboe <axboe@kernel.dk>,
Matthew Wilcox <willy@infradead.org>
Subject: Re: [PATCH 2/9] btrfs_direct_write(): cleaner way to handle generic_write_sync() suppression
Date: Wed, 8 Jun 2022 08:16:18 +0200 [thread overview]
Message-ID: <20220608061618.GA7532@lst.de> (raw)
In-Reply-To: <Yp93nbSBggvxjVqa@zeniv-ca.linux.org.uk>
On Tue, Jun 07, 2022 at 04:06:53PM +0000, Al Viro wrote:
> > Also the FUA check below needs to check IOMAP_DIO_NOSYNC as
> > well.
>
> Does it? AFAICS, we don't really care about REQ_FUA on any requests - what
> btrfs hack tries to avoid is stepping into
> if (ret > 0 && (dio->flags & IOMAP_DIO_NEED_SYNC))
> ret = generic_write_sync(iocb, ret);
> with generic_write_sync() called by btrfs_do_write_iter() after it has
> dropped the lock held through btrfs_direct_write(). Do we want to
> suppress REQ_FUA on the requests generated by __iomap_dio_rw() in
> that case (DSYNC, !SYNC)? Confused...
Yes. FUA is an used an an optimization so that we can avid the
generic_write_sync or similar call if a O_DSYNC write doesn't need
any metadata update. If the caller already does the generic_write_sync
equivalent we don't also need FUA. It is not actually harmful in that
it gives worse results, but it will kill performance.
next prev parent reply other threads:[~2022-06-08 6:50 UTC|newest]
Thread overview: 93+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-07 4:08 [RFC][PATCHES] iov_iter stuff Al Viro
2022-06-07 4:09 ` [PATCH 1/9] No need of likely/unlikely on calls of check_copy_size() Al Viro
2022-06-07 4:41 ` Christoph Hellwig
2022-06-07 11:49 ` Christian Brauner
2022-06-07 4:09 ` [PATCH 2/9] btrfs_direct_write(): cleaner way to handle generic_write_sync() suppression Al Viro
2022-06-07 4:42 ` Christoph Hellwig
2022-06-07 16:06 ` Al Viro
2022-06-07 23:27 ` Al Viro
2022-06-07 23:31 ` [PATCH 01/10] No need of likely/unlikely on calls of check_copy_size() Al Viro
2022-06-07 23:31 ` [PATCH 02/10] teach iomap_dio_rw() to suppress dsync Al Viro
2022-06-08 6:18 ` Christoph Hellwig
2022-06-08 15:17 ` Darrick J. Wong
2022-06-10 11:38 ` Christian Brauner
2022-06-07 23:31 ` [PATCH 03/10] btrfs: use IOMAP_DIO_NOSYNC Al Viro
2022-06-08 6:18 ` Christoph Hellwig
2022-06-10 11:09 ` Christian Brauner
2022-06-07 23:31 ` [PATCH 04/10] struct file: use anonymous union member for rcuhead and llist Al Viro
2022-06-07 23:31 ` [PATCH 05/10] iocb: delay evaluation of IS_SYNC(...) until we want to check IOCB_DSYNC Al Viro
2022-06-10 11:41 ` Christian Brauner
2022-06-07 23:31 ` [PATCH 06/10] keep iocb_flags() result cached in struct file Al Viro
2022-06-09 0:35 ` Dave Chinner
2022-06-10 11:43 ` Christian Brauner
2022-06-07 23:31 ` [PATCH 07/10] copy_page_{to,from}_iter(): switch iovec variants to generic Al Viro
2022-06-07 23:31 ` [PATCH 08/10] new iov_iter flavour - ITER_UBUF Al Viro
2022-06-07 23:31 ` [PATCH 09/10] switch new_sync_{read,write}() to ITER_UBUF Al Viro
2022-06-10 11:11 ` Christian Brauner
2022-06-07 23:31 ` [PATCH 10/10] iov_iter_bvec_advance(): don't bother with bvec_iter Al Viro
2022-06-08 6:16 ` Christoph Hellwig [this message]
2022-06-07 14:49 ` [PATCH 2/9] btrfs_direct_write(): cleaner way to handle generic_write_sync() suppression Matthew Wilcox
2022-06-07 20:17 ` Al Viro
2022-06-07 4:10 ` [PATCH 3/9] struct file: use anonymous union member for rcuhead and llist Al Viro
2022-06-07 10:18 ` Jan Kara
2022-06-07 11:46 ` Christian Brauner
2022-06-07 4:11 ` [PATCH 4/9] iocb: delay evaluation of IS_SYNC(...) until we want to check IOCB_DSYNC Al Viro
2022-06-07 10:34 ` Jan Kara
2022-06-07 15:34 ` Al Viro
2022-06-07 4:11 ` [PATCH 5/9] keep iocb_flags() result cached in struct file Al Viro
2022-06-07 4:12 ` [PATCH 6/9] copy_page_{to,from}_iter(): switch iovec variants to generic Al Viro
2022-06-07 4:12 ` [PATCH 7/9] new iov_iter flavour - ITER_UBUF Al Viro
2022-06-07 4:13 ` [PATCH 8/9] switch new_sync_{read,write}() to ITER_UBUF Al Viro
2022-06-07 4:13 ` [PATCH 9/9] iov_iter_bvec_advance(): don't bother with bvec_iter Al Viro
2022-06-08 19:28 ` [RFC][PATCHES] iov_iter stuff Sedat Dilek
2022-06-08 20:39 ` Al Viro
2022-06-09 19:10 ` Sedat Dilek
2022-06-09 19:22 ` Matthew Wilcox
2022-06-09 19:58 ` Matthew Wilcox
2022-06-09 19:45 ` Al Viro
2022-06-17 22:30 ` Jens Axboe
2022-06-17 22:48 ` Al Viro
2022-06-18 5:27 ` Al Viro
2022-06-18 5:35 ` [PATCH 01/31] splice: stop abusing iov_iter_advance() to flush a pipe Al Viro
2022-06-18 5:35 ` [PATCH 02/31] ITER_PIPE: helper for getting pipe buffer by index Al Viro
2022-06-18 5:35 ` [PATCH 03/31] ITER_PIPE: helpers for adding pipe buffers Al Viro
2022-06-18 5:35 ` [PATCH 04/31] ITER_PIPE: allocate buffers as we go in copy-to-pipe primitives Al Viro
2022-06-19 1:34 ` Al Viro
2022-06-18 5:35 ` [PATCH 05/31] ITER_PIPE: fold push_pipe() into __pipe_get_pages() Al Viro
2022-06-18 5:35 ` [PATCH 06/31] ITER_PIPE: lose iter_head argument of __pipe_get_pages() Al Viro
2022-06-18 5:35 ` [PATCH 07/31] ITER_PIPE: clean pipe_advance() up Al Viro
2022-06-18 5:35 ` [PATCH 08/31] ITER_PIPE: clean iov_iter_revert() Al Viro
2022-06-18 5:35 ` [PATCH 09/31] ITER_PIPE: cache the type of last buffer Al Viro
2022-06-18 5:35 ` [PATCH 10/10] iov_iter_bvec_advance(): don't bother with bvec_iter Al Viro
2022-06-18 5:35 ` [PATCH 10/31] ITER_PIPE: fold data_start() and pipe_space_for_user() together Al Viro
2022-06-19 2:25 ` Al Viro
2022-06-18 5:35 ` [PATCH 11/31] iov_iter_get_pages{,_alloc}(): cap the maxsize with LONG_MAX Al Viro
2022-06-18 5:35 ` [PATCH 12/31] iov_iter_get_pages_alloc(): lift freeing pages array on failure exits into wrapper Al Viro
2022-06-18 5:35 ` [PATCH 13/31] iov_iter_get_pages(): sanity-check arguments Al Viro
2022-06-19 3:07 ` Al Viro
2022-06-18 5:35 ` [PATCH 14/31] unify pipe_get_pages() and pipe_get_pages_alloc() Al Viro
2022-06-18 5:35 ` [PATCH 15/31] unify xarray_get_pages() and xarray_get_pages_alloc() Al Viro
2022-06-18 5:35 ` [PATCH 16/31] unify the rest of iov_iter_get_pages()/iov_iter_get_pages_alloc() guts Al Viro
2022-06-19 3:56 ` Al Viro
2022-06-18 5:35 ` [PATCH 17/31] ITER_XARRAY: don't open-code DIV_ROUND_UP() Al Viro
2022-06-18 5:35 ` [PATCH 18/31] iov_iter: lift dealing with maxpages out of first_{iovec,bvec}_segment() Al Viro
2022-06-18 5:35 ` [PATCH 19/31] iov_iter: massage calling conventions for first_{iovec,bvec}_segment() Al Viro
2022-06-18 11:13 ` Al Viro
2022-06-18 11:18 ` Al Viro
2022-06-18 5:35 ` [PATCH 20/31] found_iovec_segment(): just return address Al Viro
2022-06-18 5:35 ` [PATCH 21/31] fold __pipe_get_pages() into pipe_get_pages() Al Viro
2022-06-18 5:35 ` [PATCH 22/31] iov_iter: saner helper for page array allocation Al Viro
2022-06-18 11:14 ` Al Viro
2022-06-18 5:35 ` [PATCH 23/31] iov_iter: advancing variants of iov_iter_get_pages{,_alloc}() Al Viro
2022-06-18 5:35 ` [PATCH 24/31] block: convert to " Al Viro
2022-06-18 5:35 ` [PATCH 25/31] iter_to_pipe(): switch to advancing variant of iov_iter_get_pages() Al Viro
2022-06-18 5:35 ` [PATCH 26/31] af_alg_make_sg(): " Al Viro
2022-06-18 5:35 ` [PATCH 27/31] 9p: convert to advancing variant of iov_iter_get_pages_alloc() Al Viro
2022-06-18 5:35 ` [PATCH 28/31] ceph: switch the last caller " Al Viro
2022-06-18 5:35 ` [PATCH 29/31] get rid of non-advancing variants Al Viro
2022-06-18 11:14 ` Al Viro
2022-06-18 5:35 ` [PATCH 30/31] pipe_get_pages(): switch to append_pipe() Al Viro
2022-06-19 4:01 ` Al Viro
2022-06-19 4:09 ` Al Viro
2022-06-18 5:35 ` [PATCH 31/31] expand those iov_iter_advance() Al Viro
2022-06-18 11:14 ` Al Viro
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