From: Goldwyn Rodrigues <rgoldwyn@suse.de> To: Matthew Wilcox <willy@infradead.org> 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 08:49:52 -0500 [thread overview] Message-ID: <20200707134952.3niqhxngwh3gus54@fiona> (raw) In-Reply-To: <20200707125705.GK25523@casper.infradead.org> On 13:57 07/07, Matthew Wilcox wrote: > 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 That indeed would make reads faster. How about if the pages are dirty during DIO reads? Should a direct I/O read be responsible for making sure that the dirty pages are written back. Technically direct I/O reads is that we are reading from the device. > 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. Yes, that makes sense. If this is implemented, what would be the difference between O_DIRECT and O_DSYNC, if any? -- Goldwyn
WARNING: multiple messages have this Message-ID (diff)
From: Goldwyn Rodrigues <rgoldwyn@suse.de> To: cluster-devel.redhat.com Subject: [Cluster-devel] 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 08:49:52 -0500 [thread overview] Message-ID: <20200707134952.3niqhxngwh3gus54@fiona> (raw) In-Reply-To: <20200707125705.GK25523@casper.infradead.org> On 13:57 07/07, Matthew Wilcox wrote: > 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 That indeed would make reads faster. How about if the pages are dirty during DIO reads? Should a direct I/O read be responsible for making sure that the dirty pages are written back. Technically direct I/O reads is that we are reading from the device. > 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. Yes, that makes sense. If this is implemented, what would be the difference between O_DIRECT and O_DSYNC, if any? -- Goldwyn
next prev parent reply other threads:[~2020-07-07 13:49 UTC|newest] Thread overview: 49+ 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 2020-07-01 7:53 ` [Cluster-devel] " Christoph Hellwig 2020-07-07 12:43 ` Goldwyn Rodrigues 2020-07-07 12:43 ` [Cluster-devel] " Goldwyn Rodrigues 2020-07-07 12:57 ` Matthew Wilcox 2020-07-07 12:57 ` [Cluster-devel] " Matthew Wilcox 2020-07-07 13:00 ` Christoph Hellwig 2020-07-07 13:00 ` [Cluster-devel] " Christoph Hellwig 2020-07-08 6:51 ` Dave Chinner 2020-07-08 6:51 ` [Cluster-devel] " Dave Chinner 2020-07-08 13:54 ` Matthew Wilcox 2020-07-08 13:54 ` [Cluster-devel] " Matthew Wilcox 2020-07-08 16:54 ` Christoph Hellwig 2020-07-08 16:54 ` [Cluster-devel] " Christoph Hellwig 2020-07-08 17:11 ` Matthew Wilcox 2020-07-08 17:11 ` [Cluster-devel] " Matthew Wilcox 2020-07-09 8:26 ` Steven Whitehouse 2020-07-09 8:26 ` Steven Whitehouse 2020-07-09 2:25 ` Dave Chinner 2020-07-09 2:25 ` [Cluster-devel] " Dave Chinner 2020-07-09 16:09 ` Darrick J. Wong 2020-07-09 16:09 ` [Cluster-devel] " Darrick J. Wong 2020-07-09 17:05 ` Matthew Wilcox 2020-07-09 17:05 ` [Cluster-devel] " Matthew Wilcox 2020-07-09 17:10 ` Darrick J. Wong 2020-07-09 17:10 ` [Cluster-devel] " Darrick J. Wong 2020-07-09 22:59 ` Dave Chinner 2020-07-09 22:59 ` [Cluster-devel] " Dave Chinner 2020-07-10 16:03 ` Christoph Hellwig 2020-07-10 16:03 ` [Cluster-devel] " Christoph Hellwig 2020-07-12 11:36 ` Avi Kivity 2020-07-12 11:36 ` [Cluster-devel] " Avi Kivity 2020-07-07 13:49 ` Goldwyn Rodrigues [this message] 2020-07-07 13:49 ` Goldwyn Rodrigues 2020-07-07 14:01 ` Darrick J. Wong 2020-07-07 14:01 ` [Cluster-devel] " Darrick J. Wong 2020-07-07 14:30 ` Goldwyn Rodrigues 2020-07-07 14:30 ` [Cluster-devel] " 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
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=20200707134952.3niqhxngwh3gus54@fiona \ --to=rgoldwyn@suse.de \ --cc=cluster-devel@redhat.com \ --cc=darrick.wong@oracle.com \ --cc=david@fromorbit.com \ --cc=dsterba@suse.cz \ --cc=fdmanana@gmail.com \ --cc=hch@lst.de \ --cc=linux-btrfs@vger.kernel.org \ --cc=linux-ext4@vger.kernel.org \ --cc=linux-fsdevel@vger.kernel.org \ --cc=linux-xfs@vger.kernel.org \ --cc=willy@infradead.org \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
This is an external index of several public inboxes, see mirroring instructions on how to clone and mirror all data and code used by this external index.