From: Matthew Bobrowski <mbobrowski@mbobrowski.org>
To: Jan Kara <jack@suse.cz>
Cc: tytso@mit.edu, adilger.kernel@dilger.ca,
linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org,
hch@infradead.org, david@fromorbit.com, darrick.wong@oracle.com
Subject: Re: [PATCH v4 4/8] ext4: introduce direct I/O read path using iomap infrastructure
Date: Wed, 9 Oct 2019 21:55:09 +1100 [thread overview]
Message-ID: <20191009105507.GF14749@poseidon.bobrowski.net> (raw)
In-Reply-To: <20191008105207.GG5078@quack2.suse.cz>
On Tue, Oct 08, 2019 at 12:52:07PM +0200, Jan Kara wrote:
> On Thu 03-10-19 21:34:00, Matthew Bobrowski wrote:
> > This patch introduces a new direct I/O read path that makes use of the
> > iomap infrastructure.
> >
> > The new function ext4_dio_read_iter() is responsible for calling into
> > the iomap infrastructure via iomap_dio_rw(). If the read operation
> > being performed on the inode does not pass the preliminary checks
> > performed within ext4_dio_supported(), then we simply fallback to
> > buffered I/O in order to fulfil the request.
> >
> > Existing direct I/O read buffer_head code has been removed as it's now
> > redundant.
> >
> > Signed-off-by: Matthew Bobrowski <mbobrowski@mbobrowski.org>
>
> The patch looks good to me. Just one small nit below. With that fixed, you
> can add:
>
> Reviewed-by: Jan Kara <jack@suse.cz>
Cool, I'll fix it!
> > + /*
> > + * Get exclusion from truncate and other inode operations.
> > + */
> > + if (!inode_trylock_shared(inode)) {
> > + if (iocb->ki_flags & IOCB_NOWAIT)
> > + return -EAGAIN;
> > + inode_lock_shared(inode);
> > + }
>
> I've noticed here you actually introduce new trylock pattern - previously
> we had unconditional inode_lock_shared() in ext4_direct_IO_read(). So the
> cleanest would be to just use unconditional inode_lock_shared() here and
> then fixup IOCB_NOWAIT handling (I agree that was missing in the original
> code) in a separate patch.
Right, so I will just have an unconditional call to
inode_lock_shared() and in the patch that follows I will fix it up to
apply the new pattern.
> And the pattern should rather look like:
>
> if (iocb->ki_flags & IOCB_NOWAIT) {
> if (!inode_trylock_shared(inode))
> return -EAGAIN;
> } else {
> inode_lock_shared(inode);
> }
>
> to avoid two atomical operations instead of one in the fast path. No need
> to repeat old mistakes when we know better :).
Yes, also agree.
--<M>--
next prev parent reply other threads:[~2019-10-09 10:55 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-03 11:32 [PATCH v4 0/8] ext4: port direct I/O to iomap infrastructure Matthew Bobrowski
2019-10-03 11:33 ` [PATCH v4 1/8] ext4: move out iomap field population into separate helper Matthew Bobrowski
2019-10-08 10:27 ` Jan Kara
2019-10-09 8:57 ` Matthew Bobrowski
2019-10-09 13:06 ` Jan Kara
2019-10-10 5:39 ` Matthew Bobrowski
2019-10-09 6:02 ` Ritesh Harjani
2019-10-09 7:07 ` Christoph Hellwig
2019-10-09 7:50 ` Ritesh Harjani
2019-10-09 9:09 ` Matthew Bobrowski
2019-10-03 11:33 ` [PATCH v4 2/8] ext4: move out IOMAP_WRITE path " Matthew Bobrowski
2019-10-08 10:31 ` Jan Kara
2019-10-09 9:18 ` Matthew Bobrowski
2019-10-09 6:22 ` Ritesh Harjani
2019-10-09 9:31 ` Matthew Bobrowski
2019-10-03 11:33 ` [PATCH v4 3/8] ext4: introduce new callback for IOMAP_REPORT operations Matthew Bobrowski
2019-10-08 10:42 ` Jan Kara
2019-10-09 9:41 ` Matthew Bobrowski
2019-10-09 6:00 ` Ritesh Harjani
2019-10-09 12:08 ` Matthew Bobrowski
2019-10-09 13:14 ` Ritesh Harjani
2019-10-03 11:34 ` [PATCH v4 4/8] ext4: introduce direct I/O read path using iomap infrastructure Matthew Bobrowski
2019-10-08 10:52 ` Jan Kara
2019-10-09 10:55 ` Matthew Bobrowski [this message]
2019-10-09 6:39 ` Ritesh Harjani
2019-10-03 11:34 ` [PATCH v4 5/8] ext4: move inode extension/truncate code out from ->iomap_end() callback Matthew Bobrowski
2019-10-08 11:25 ` Jan Kara
2019-10-09 10:18 ` Matthew Bobrowski
2019-10-09 12:51 ` Jan Kara
2019-10-10 5:44 ` Matthew Bobrowski
2019-10-09 6:27 ` Ritesh Harjani
2019-10-09 10:20 ` Matthew Bobrowski
2019-10-03 11:34 ` [PATCH v4 6/8] ext4: move inode extension checks out from ext4_iomap_alloc() Matthew Bobrowski
2019-10-08 11:27 ` Jan Kara
2019-10-09 10:21 ` Matthew Bobrowski
2019-10-09 6:30 ` Ritesh Harjani
2019-10-09 10:39 ` Matthew Bobrowski
2019-10-03 11:34 ` [PATCH v4 7/8] ext4: reorder map.m_flags checks in ext4_set_iomap() Matthew Bobrowski
2019-10-08 11:30 ` Jan Kara
2019-10-09 10:42 ` Matthew Bobrowski
2019-10-09 6:35 ` Ritesh Harjani
2019-10-09 10:43 ` Matthew Bobrowski
2019-10-03 11:35 ` [PATCH v4 8/8] ext4: introduce direct I/O write path using iomap infrastructure Matthew Bobrowski
2019-10-08 15:12 ` Jan Kara
2019-10-09 7:11 ` Christoph Hellwig
2019-10-09 13:41 ` Jan Kara
2019-10-09 11:53 ` Matthew Bobrowski
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