From: Dave Chinner <david@fromorbit.com>
To: Jan Kara <jack@suse.cz>
Cc: Matthew Bobrowski <mbobrowski@mbobrowski.org>,
linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org,
tytso@mit.edu, riteshh@linux.ibm.com
Subject: Re: [PATCH 4/5] ext4: introduce direct IO write code path using iomap infrastructure
Date: Thu, 29 Aug 2019 08:32:18 +1000 [thread overview]
Message-ID: <20190828223218.GZ7777@dread.disaster.area> (raw)
In-Reply-To: <20190828202619.GG22343@quack2.suse.cz>
On Wed, Aug 28, 2019 at 10:26:19PM +0200, Jan Kara wrote:
> On Mon 12-08-19 22:53:26, Matthew Bobrowski wrote:
> > This patch introduces a new direct IO write code path implementation
> > that makes use of the iomap infrastructure.
> >
> > All direct IO write operations are now passed from the ->write_iter() callback
> > to the new function ext4_dio_write_iter(). This function is responsible for
> > calling into iomap infrastructure via iomap_dio_rw(). Snippets of the direct
> > IO code from within ext4_file_write_iter(), such as checking whether the IO
> > request is unaligned asynchronous IO, or whether it will ber overwriting
> > allocated and initialized blocks has been moved out and into
> > ext4_dio_write_iter().
> >
> > The block mapping flags that are passed to ext4_map_blocks() from within
> > ext4_dio_get_block() and friends have effectively been taken out and
> > introduced within the ext4_iomap_begin(). If ext4_map_blocks() happens to have
> > instantiated blocks beyond the i_size, then we attempt to place the inode onto
> > the orphan list. Despite being able to perform i_size extension checking
> > earlier on in the direct IO code path, it makes most sense to perform this bit
> > post successful block allocation.
> >
> > The ->end_io() callback ext4_dio_write_end_io() is responsible for removing
> > the inode from the orphan list and determining if we should truncate a failed
> > write in the case of an error. We also convert a range of unwritten extents to
> > written if IOMAP_DIO_UNWRITTEN is set and perform the necessary
> > i_size/i_disksize extension if the iocb->ki_pos + dio->size > i_size_read(inode).
> >
> > In the instance of a short write, we fallback to buffered IO and complete
> > whatever is left the 'iter'. Any blocks that may have been allocated in
> > preparation for direct IO will be reused by buffered IO, so there's no issue
> > with leaving allocated blocks beyond EOF.
> >
> > Signed-off-by: Matthew Bobrowski <mbobrowski@mbobrowski.org>
> > ---
> > fs/ext4/file.c | 227 ++++++++++++++++++++++++++++++++++++++++----------------
> > fs/ext4/inode.c | 42 +++++++++--
> > 2 files changed, 199 insertions(+), 70 deletions(-)
>
> Overall this is very nice. Some smaller comments below.
>
> > @@ -235,6 +244,34 @@ static ssize_t ext4_write_checks(struct kiocb *iocb, struct iov_iter *from)
> > return iov_iter_count(from);
> > }
> >
> > +static ssize_t ext4_buffered_write_iter(struct kiocb *iocb,
> > + struct iov_iter *from)
> > +{
> > + ssize_t ret;
> > + struct inode *inode = file_inode(iocb->ki_filp);
> > +
> > + if (!inode_trylock(inode)) {
> > + if (iocb->ki_flags & IOCB_NOWAIT)
> > + return -EOPNOTSUPP;
> > + inode_lock(inode);
> > + }
>
> Currently there's no support for IOCB_NOWAIT for buffered IO so you can
> replace this with "inode_lock(inode)".
IOCB_NOWAIT is supported for buffered reads. It is not supported on
buffered writes (as yet), so this should return EOPNOTSUPP if
IOCB_NOWAIT is set, regardless of whether the lock can be grabbed or
not.
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
next prev parent reply other threads:[~2019-08-28 22:32 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-12 12:52 [PATCH 0/5] ext4: direct IO via iomap infrastructure Matthew Bobrowski
2019-08-12 12:52 ` [PATCH 1/5] ext4: introduce direct IO read code path using " Matthew Bobrowski
2019-08-12 17:18 ` Christoph Hellwig
2019-08-12 20:17 ` Matthew Wilcox
2019-08-13 10:45 ` Matthew Bobrowski
2019-08-12 12:52 ` [PATCH 2/5] ext4: move inode extension/truncate code out from ext4_iomap_end() Matthew Bobrowski
2019-08-12 17:18 ` Christoph Hellwig
2019-08-13 10:46 ` Matthew Bobrowski
2019-08-28 19:59 ` Jan Kara
2019-08-28 21:54 ` Matthew Bobrowski
2019-08-29 8:18 ` Jan Kara
2019-08-12 12:53 ` [PATCH 3/5] iomap: modify ->end_io() calling convention Matthew Bobrowski
2019-08-12 17:18 ` Christoph Hellwig
2019-08-13 10:43 ` Matthew Bobrowski
2019-08-12 12:53 ` [PATCH 4/5] ext4: introduce direct IO write code path using iomap infrastructure Matthew Bobrowski
2019-08-12 17:04 ` RITESH HARJANI
2019-08-13 12:58 ` Matthew Bobrowski
2019-08-13 14:35 ` Darrick J. Wong
2019-08-14 9:51 ` Matthew Bobrowski
2019-08-12 17:34 ` Christoph Hellwig
2019-08-13 10:45 ` Matthew Bobrowski
2019-08-28 20:26 ` Jan Kara
2019-08-28 22:32 ` Dave Chinner [this message]
2019-08-29 8:03 ` Jan Kara
2019-08-29 11:47 ` Matthew Bobrowski
2019-08-29 11:45 ` Matthew Bobrowski
2019-08-29 12:38 ` Jan Kara
2019-08-12 12:53 ` [PATCH 5/5] ext4: clean up redundant buffer_head direct IO code Matthew Bobrowski
2019-08-12 17:31 ` [PATCH 0/5] ext4: direct IO via iomap infrastructure RITESH HARJANI
2019-08-13 11:10 ` Matthew Bobrowski
2019-08-13 12:27 ` RITESH HARJANI
2019-08-14 9:48 ` Matthew Bobrowski
2019-08-14 11:58 ` RITESH HARJANI
2019-08-21 13:14 ` Matthew Bobrowski
2019-08-22 12:00 ` Matthew Bobrowski
2019-08-22 14:11 ` Ritesh Harjani
2019-08-24 3:18 ` Matthew Bobrowski
2019-08-24 3:55 ` Darrick J. Wong
2019-08-24 23:04 ` Christoph Hellwig
2019-08-27 9:52 ` Matthew Bobrowski
2019-08-28 12:05 ` Matthew Bobrowski
2019-08-28 14:27 ` Theodore Y. Ts'o
2019-08-28 18:02 ` Jan Kara
2019-08-29 6:36 ` Christoph Hellwig
2019-08-29 11:20 ` Matthew Bobrowski
2019-08-29 14:41 ` Christoph Hellwig
2019-08-23 13:43 ` [RFC 1/1] ext4: PoC implementation of option-1 Ritesh Harjani
2019-08-23 13:49 ` Ritesh Harjani
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