linux-api.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
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

  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

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=20170404075853.GB28522@quack2.suse.cz \
    --to=jack@suse.cz \
    --cc=avi@scylladb.com \
    --cc=axboe@kernel.dk \
    --cc=hch@infradead.org \
    --cc=jack@suse.com \
    --cc=linux-api@vger.kernel.org \
    --cc=linux-block@vger.kernel.org \
    --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=rgoldwyn@suse.com \
    --cc=rgoldwyn@suse.de \
    --cc=sagi@grimberg.me \
    --cc=tom.leiming@gmail.com \
    --cc=willy@infradead.org \
    --subject='Re: [PATCH 6/8] nowait aio: ext4' \
    /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: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).