From: Jan Kara <jack@suse.cz>
To: Goldwyn Rodrigues <rgoldwyn@suse.de>
Cc: linux-fsdevel@vger.kernel.org, jack@suse.com, hch@infradead.org,
linux-block@vger.kernel.org, linux-btrfs@vger.kernel.org,
linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org,
sagi@grimberg.me, avi@scylladb.com, axboe@kernel.dk,
linux-api@vger.kernel.org, willy@infradead.org,
tom.leiming@gmail.com, Goldwyn Rodrigues <rgoldwyn@suse.com>
Subject: Re: [PATCH 6/8] nowait aio: ext4
Date: Tue, 4 Apr 2017 09:58:53 +0200 [thread overview]
Message-ID: <20170404075853.GB28522@quack2.suse.cz> (raw)
In-Reply-To: <20170403185307.6243-7-rgoldwyn@suse.de>
On Mon 03-04-17 13:53:05, Goldwyn Rodrigues wrote:
> From: Goldwyn Rodrigues <rgoldwyn@suse.com>
>
> Return EAGAIN if any of the following checks fail for direct I/O:
> + i_rwsem is lockable
> + Writing beyond end of file (will trigger allocation)
> + Blocks are not allocated at the write location
Patches seem to be missing your Signed-off-by tag...
> @@ -235,9 +237,21 @@ ext4_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
>
> iocb->private = &overwrite;
> /* Check whether we do a DIO overwrite or not */
> - if (o_direct && ext4_should_dioread_nolock(inode) && !unaligned_aio &&
> - ext4_overwrite_io(inode, iocb->ki_pos, iov_iter_count(from)))
> - overwrite = 1;
> + if (o_direct && !unaligned_aio) {
> + struct ext4_map_blocks map;
> + if (ext4_blocks_mapped(inode, iocb->ki_pos,
> + iov_iter_count(from), &map)) {
> + /* To exclude unwritten extents, we need to check
> + * m_flags.
> + */
> + if (ext4_should_dioread_nolock(inode) &&
> + (map.m_flags & EXT4_MAP_MAPPED))
> + overwrite = 1;
> + } else if (iocb->ki_flags & IOCB_NOWAIT) {
> + ret = -EAGAIN;
> + goto out;
> + }
> + }
Actually, overwriting unwritten extents is relatively complex in ext4 as
well. In particular we need to start a transaction and split out the
written part of the extent. So I don't think we can easily support this
without blocking. As a result I'd keep the condition for IOCB_NOWAIT the
same as for overwrite IO.
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -117,7 +117,7 @@ static struct file_system_type ext2_fs_type = {
> .name = "ext2",
> .mount = ext4_mount,
> .kill_sb = kill_block_super,
> - .fs_flags = FS_REQUIRES_DEV,
> + .fs_flags = FS_REQUIRES_DEV | FS_NOWAIT,
FS_NOWAIT looks a bit too generic given these are filesystem feature flags.
Can we call it FS_NOWAIT_IO?
Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
next prev parent reply other threads:[~2017-04-04 7:58 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-03 18:52 [PATCH 0/8 v4] No wait AIO Goldwyn Rodrigues
[not found] ` <20170403185307.6243-1-rgoldwyn-l3A5Bk7waGM@public.gmane.org>
2017-04-03 18:53 ` [PATCH 1/8] nowait aio: Introduce IOCB_RW_FLAG_NOWAIT Goldwyn Rodrigues
2017-04-04 6:48 ` Christoph Hellwig
2017-04-03 18:53 ` [PATCH 8/8] nowait aio: btrfs Goldwyn Rodrigues
2017-04-03 18:53 ` [PATCH 2/8] nowait aio: Return if cannot get hold of i_rwsem Goldwyn Rodrigues
2017-04-03 18:53 ` [PATCH 3/8] nowait aio: return if direct write will trigger writeback Goldwyn Rodrigues
2017-04-03 18:53 ` [PATCH 4/8] nowait-aio: Introduce IOMAP_NOWAIT Goldwyn Rodrigues
2017-04-03 18:53 ` [PATCH 5/8] nowait aio: return on congested block device Goldwyn Rodrigues
2017-04-04 6:49 ` Christoph Hellwig
2017-04-03 18:53 ` [PATCH 6/8] nowait aio: ext4 Goldwyn Rodrigues
2017-04-04 7:58 ` Jan Kara [this message]
2017-04-04 8:41 ` Christoph Hellwig
2017-04-04 18:41 ` Goldwyn Rodrigues
2017-04-10 7:45 ` Christoph Hellwig
[not found] ` <20170410074539.GA18250-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
2017-04-10 12:37 ` Jan Kara
2017-04-10 14:39 ` Christoph Hellwig
2017-04-10 15:13 ` Jan Kara
2017-04-03 18:53 ` [PATCH 7/8] nowait aio: xfs Goldwyn Rodrigues
2017-04-04 6:52 ` Christoph Hellwig
[not found] ` <20170404065211.GD21942-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
2017-04-06 22:54 ` Darrick J. Wong
2017-04-07 11:34 ` Goldwyn Rodrigues
2017-04-07 15:08 ` Darrick J. Wong
-- strict thread matches above, loose matches on Subject: below --
2017-05-09 12:22 [PATCH 0/8 v7] No wait AIO Goldwyn Rodrigues
2017-05-09 12:22 ` [PATCH 6/8] nowait aio: ext4 Goldwyn Rodrigues
[not found] ` <20170509122219.31756-7-rgoldwyn-l3A5Bk7waGM@public.gmane.org>
2017-05-09 14:57 ` Jan Kara
2017-04-14 12:02 [PATCH 0/8 v6] No wait AIO Goldwyn Rodrigues
2017-04-14 12:02 ` [PATCH 6/8] nowait aio: ext4 Goldwyn Rodrigues
2017-03-15 21:50 [PATCH 0/8 v3] No wait AIO Goldwyn Rodrigues
2017-03-15 21:51 ` [PATCH 6/8] nowait aio: ext4 Goldwyn Rodrigues
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