From: "Darrick J. Wong" <darrick.wong@oracle.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Matthew Wilcox <willy@infradead.org>,
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 08:59:25 -0700 [thread overview]
Message-ID: <20200721155925.GB3151642@magnolia> (raw)
In-Reply-To: <20200721154132.GA11652@lst.de>
On Tue, Jul 21, 2020 at 05:41:32PM +0200, Christoph Hellwig wrote:
> On Tue, Jul 21, 2020 at 08:27:54AM -0700, Darrick J. Wong wrote:
> > On Tue, Jul 21, 2020 at 05:16:16PM +0200, Christoph Hellwig wrote:
> > > On Tue, Jul 21, 2020 at 04:14:37PM +0100, Matthew Wilcox wrote:
> > > > On Tue, Jul 21, 2020 at 05:06:15PM +0200, Christoph Hellwig wrote:
> > > > > On Tue, Jul 21, 2020 at 04:04:32PM +0100, Matthew Wilcox wrote:
> > > > > > I thought you were going to respin this with EREMCHG changed to ENOTBLK?
> > > > >
> > > > > Oh, true. I'll do that ASAP.
> > > >
> > > > Michael, could we add this to manpages?
> > >
> > > 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).
> >
> > It's worth dropping a comment somewhere that ENOTBLK is the desired
> > "fall back to buffered" errcode, seeing as Dave and I missed that in
> > XFS...
>
> Sounds like a good idea, but what would a good place be?
In the comment that precedes iomap_dio_rw() for the iomap version,
and...
...ye $deity, the old direct-io.c file is a mess of wrappers. Uh... a
new comment preceding __blockdev_direct_IO? Or blockdev_direct_IO? Or
both?
Or I guess the direct_IO documentation in vfs.rst...?
``direct_IO``
called by the generic read/write routines to perform direct_IO -
that is IO requests which bypass the page cache and transfer
data directly between the storage and the application's address
space. This function can return -ENOTBLK to signal that it is
necessary to fallback to buffered IO. Note that
blockdev_direct_IO and variants can also return -ENOTBLK.
--D
next prev parent reply other threads:[~2020-07-21 15:59 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20200713074633.875946-1-hch@lst.de>
[not found] ` <20200720215125.bfz7geaftocy4r5l@fiona>
[not found] ` <20200721145313.GA9217@lst.de>
[not found] ` <20200721150432.GH15516@casper.infradead.org>
[not found] ` <20200721150615.GA10330@lst.de>
2020-07-21 15:14 ` RFC: iomap write invalidation 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 [this message]
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
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