From: "Darrick J. Wong" <darrick.wong@oracle.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: Christoph Hellwig <hch@lst.de>,
Goldwyn Rodrigues <rgoldwyn@suse.de>,
Dave Chinner <david@fromorbit.com>,
Damien Le Moal <damien.lemoal@wdc.com>,
Naohiro Aota <naohiro.aota@wdc.com>,
Johannes Thumshirn <jth@kernel.org>,
linux-btrfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
cluster-devel@redhat.com, linux-ext4@vger.kernel.org,
linux-xfs@vger.kernel.org,
Michael Kerrisk <mtk.manpages@gmail.com>,
linux-man@vger.kernel.org
Subject: Re: RFC: iomap write invalidation
Date: Tue, 21 Jul 2020 09:03:42 -0700 [thread overview]
Message-ID: <20200721160342.GC3151642@magnolia> (raw)
In-Reply-To: <20200721155201.GL15516@casper.infradead.org>
On Tue, Jul 21, 2020 at 04:52:01PM +0100, Matthew Wilcox wrote:
> On Tue, Jul 21, 2020 at 05:42:40PM +0200, Christoph Hellwig wrote:
> > On Tue, Jul 21, 2020 at 04:31:36PM +0100, Matthew Wilcox wrote:
> > > > Umm, no. -ENOTBLK is internal - the file systems will retry using
> > > > buffered I/O and the error shall never escape to userspace (or even the
> > > > VFS for that matter).
> > >
> > > Ah, I made the mistake of believing the comments that I could see in
> > > your patch instead of reading the code.
> > >
> > > Can I suggest deleting this comment:
> > >
> > > /*
> > > * No fallback to buffered IO on errors for XFS, direct IO will either
> > > * complete fully or fail.
> > > */
> > >
> > > and rewording this one:
> > >
> > > /*
> > > * Allow a directio write to fall back to a buffered
> > > * write *only* in the case that we're doing a reflink
> > > * CoW. In all other directio scenarios we do not
> > > * allow an operation to fall back to buffered mode.
> > > */
> > >
> > > as part of your revised patchset?
> >
> > That isn't actually true. In current mainline we only fallback on
> > reflink RMW cases, but with this series we also fall back for
> > invalidation failures.
>
> ... that's why I'm suggesting that you delete the first one and rewrite
> the second one. Because they aren't true.
/*
* We allow only three outcomes of a directio: (1) it succeeds
* completely; (2) it fails with a negative error code; or (3) it
* returns -ENOTBLK to signal that we should fall back to buffered IO.
*
* The third scenario should only happen if iomap refuses to perform the
* direct IO, or the direct write request requires CoW but is not aligned
* to the filesystem block size.
*/
?
--D
prev parent reply other threads:[~2020-07-21 16:06 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-13 7:46 RFC: iomap write invalidation Christoph Hellwig
2020-07-13 7:46 ` [PATCH 1/2] iomap: Only invalidate page cache pages on direct IO writes Christoph Hellwig
2020-07-13 7:46 ` [PATCH 2/2] iomap: fall back to buffered writes for invalidation failures Christoph Hellwig
2020-07-13 11:55 ` Matthew Wilcox
2020-07-14 11:00 ` Christoph Hellwig
2020-07-13 12:20 ` Goldwyn Rodrigues
2020-07-13 16:09 ` David Sterba
2020-07-13 15:39 ` Darrick J. Wong
2020-07-14 11:00 ` Christoph Hellwig
2020-07-14 1:41 ` Damien Le Moal
2020-07-15 1:47 ` RFC: iomap write invalidation Dave Chinner
2020-07-20 21:51 ` Goldwyn Rodrigues
2020-07-21 14:53 ` Christoph Hellwig
2020-07-21 14:59 ` Darrick J. Wong
2020-07-21 15:04 ` Matthew Wilcox
2020-07-21 15:06 ` Christoph Hellwig
2020-07-21 15:14 ` Matthew Wilcox
2020-07-21 15:16 ` Christoph Hellwig
2020-07-21 15:27 ` Darrick J. Wong
2020-07-21 15:41 ` Christoph Hellwig
2020-07-21 15:59 ` Darrick J. Wong
2020-07-21 16:01 ` Christoph Hellwig
2020-07-21 16:05 ` Darrick J. Wong
2020-07-21 15:31 ` Matthew Wilcox
2020-07-21 15:42 ` Christoph Hellwig
2020-07-21 15:52 ` Matthew Wilcox
2020-07-21 16:03 ` Darrick J. Wong [this message]
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