From: Matthew Wilcox <willy@infradead.org>
To: Goldwyn Rodrigues <rgoldwyn@suse.de>
Cc: Christoph Hellwig <hch@lst.de>,
linux-fsdevel@vger.kernel.org, linux-btrfs@vger.kernel.org,
fdmanana@gmail.com, dsterba@suse.cz, david@fromorbit.com,
darrick.wong@oracle.com, cluster-devel@redhat.com,
linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org
Subject: Re: always fall back to buffered I/O after invalidation failures, was: Re: [PATCH 2/6] iomap: IOMAP_DIO_RWF_NO_STALE_PAGECACHE return if page invalidation fails
Date: Tue, 7 Jul 2020 13:57:05 +0100 [thread overview]
Message-ID: <20200707125705.GK25523@casper.infradead.org> (raw)
In-Reply-To: <20200707124346.xnr5gtcysuzehejq@fiona>
On Tue, Jul 07, 2020 at 07:43:46AM -0500, Goldwyn Rodrigues wrote:
> On 9:53 01/07, Christoph Hellwig wrote:
> > On Mon, Jun 29, 2020 at 02:23:49PM -0500, Goldwyn Rodrigues wrote:
> > > From: Goldwyn Rodrigues <rgoldwyn@suse.com>
> > >
> > > For direct I/O, add the flag IOMAP_DIO_RWF_NO_STALE_PAGECACHE to indicate
> > > that if the page invalidation fails, return back control to the
> > > filesystem so it may fallback to buffered mode.
> > >
> > > Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
> > > Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
> >
> > I'd like to start a discussion of this shouldn't really be the
> > default behavior. If we have page cache that can't be invalidated it
> > actually makes a whole lot of sense to not do direct I/O, avoid the
> > warnings, etc.
> >
> > Adding all the relevant lists.
>
> Since no one responded so far, let me see if I can stir the cauldron :)
>
> What error should be returned in case of such an error? I think the
Christoph's message is ambiguous. I don't know if he means "fail the
I/O with an error" or "satisfy the I/O through the page cache". I'm
strongly in favour of the latter. Indeed, I'm in favour of not invalidating
the page cache at all for direct I/O. For reads, I think the page cache
should be used to satisfy any portion of the read which is currently
cached. For writes, I think we should write into the page cache pages
which currently exist, and then force those pages to be written back,
but left in cache.
next prev parent reply other threads:[~2020-07-07 12:57 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-29 19:23 [PATCH 0/6 v10] btrfs direct-io using iomap Goldwyn Rodrigues
2020-06-29 19:23 ` [PATCH 1/6] iomap: Convert wait_for_completion to flags Goldwyn Rodrigues
2020-06-29 23:03 ` David Sterba
2020-06-30 16:35 ` David Sterba
2020-07-01 7:34 ` Johannes Thumshirn
2020-07-01 7:50 ` Christoph Hellwig
2020-06-29 19:23 ` [PATCH 2/6] iomap: IOMAP_DIO_RWF_NO_STALE_PAGECACHE return if page invalidation fails Goldwyn Rodrigues
2020-07-01 7:53 ` always fall back to buffered I/O after invalidation failures, was: " Christoph Hellwig
2020-07-07 12:43 ` Goldwyn Rodrigues
2020-07-07 12:57 ` Matthew Wilcox [this message]
2020-07-07 13:00 ` Christoph Hellwig
2020-07-08 6:51 ` Dave Chinner
2020-07-08 13:54 ` Matthew Wilcox
2020-07-08 16:54 ` Christoph Hellwig
2020-07-08 17:11 ` Matthew Wilcox
2020-07-09 8:26 ` [Cluster-devel] " Steven Whitehouse
2020-07-09 2:25 ` Dave Chinner
2020-07-09 16:09 ` Darrick J. Wong
2020-07-09 17:05 ` Matthew Wilcox
2020-07-09 17:10 ` Darrick J. Wong
2020-07-09 22:59 ` Dave Chinner
2020-07-10 16:03 ` Christoph Hellwig
2020-07-12 11:36 ` Avi Kivity
2020-07-07 13:49 ` Goldwyn Rodrigues
2020-07-07 14:01 ` Darrick J. Wong
2020-07-07 14:30 ` Goldwyn Rodrigues
2020-06-29 19:23 ` [PATCH 3/6] btrfs: switch to iomap_dio_rw() for dio Goldwyn Rodrigues
2020-06-29 19:23 ` [PATCH 4/6] fs: remove dio_end_io() Goldwyn Rodrigues
2020-06-29 19:23 ` [PATCH 5/6] btrfs: remove BTRFS_INODE_READDIO_NEED_LOCK Goldwyn Rodrigues
2020-06-29 19:23 ` [PATCH 6/6] btrfs: split btrfs_direct_IO to read and write part Goldwyn Rodrigues
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