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From: Christoph Hellwig <hch@infradead.org>
To: Goldwyn Rodrigues <rgoldwyn@suse.de>
Cc: Christoph Hellwig <hch@infradead.org>,
	linux-fsdevel@vger.kernel.org, jack@suse.com,
	linux-block@vger.kernel.org, linux-btrfs@vger.kernel.org,
	linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org,
	axboe@kernel.dk, linux-api@vger.kernel.org,
	adam.manzanares@wdc.com, viro@zeniv.linux.org.uk,
	Goldwyn Rodrigues <rgoldwyn@suse.com>
Subject: Re: [PATCH 09/10] xfs: nowait aio support
Date: Mon, 29 May 2017 01:33:38 -0700
Message-ID: <20170529083338.GC1899@infradead.org> (raw)
In-Reply-To: <cfc1e7ad-f74b-a14a-ac30-8472f7f684af@suse.de>

On Sun, May 28, 2017 at 09:38:26PM -0500, Goldwyn Rodrigues wrote:
> 
> 
> On 05/28/2017 04:31 AM, Christoph Hellwig wrote:
> > Despite my previous reviewed-by tag this will need another fix:
> > 
> > xfs_file_iomap_begin needs to return EAGAIN if we don't have the extent
> > list in memoery already.  E.g. something like this:
> > 
> > 	if ((flags & IOMAP_NOWAIT) && !(ip->i_d.if_flags & XFS_IFEXTENTS)) {
> > 		error = -EAGAIN;
> > 		goto out_unlock;
> > 	}
> > 
> > right after locking the ilock.
> > 
> 
> I am not sure if it is right to penalize the application to write to
> file which has been freshly opened (and is the first one to open). It
> basically means extent maps needs to be read from disk. Do you see a
> reason it would have a non-deterministic wait if it is the only user? I
> understand the block layer can block if it has too many requests though.

For either a read or a write we might have to read in the extent list
(note that for few enough extents they are stored in the inode and
we won't have to), in which case the call will block and by the
semantics you define we'll need to return -EAGAIN.

Btw, can you write a small blurb up for the man page to document these
ѕemantics in man-page like language?

  parent reply index

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-05-24 16:41 [PATCH 0/10 v9] No wait AIO Goldwyn Rodrigues
2017-05-24 16:41 ` [PATCH 01/10] fs: Separate out kiocb flags setup based on RWF_* flags Goldwyn Rodrigues
2017-05-25  8:16   ` Jan Kara
2017-05-24 16:41 ` [PATCH 02/10] fs: Introduce filemap_range_has_page() Goldwyn Rodrigues
2017-05-25  8:25   ` Jan Kara
     [not found] ` <20170524164150.9492-1-rgoldwyn-l3A5Bk7waGM@public.gmane.org>
2017-05-24 16:41   ` [PATCH 03/10] fs: Use RWF_* flags for AIO operations Goldwyn Rodrigues
2017-05-25  8:27     ` Jan Kara
2017-05-24 16:41   ` [PATCH 05/10] fs: return if direct write will trigger writeback Goldwyn Rodrigues
2017-05-25  8:32     ` Jan Kara
2017-05-28  9:27   ` [PATCH 0/10 v9] No wait AIO Christoph Hellwig
2017-05-29  2:38     ` Goldwyn Rodrigues
2017-05-29  8:32       ` Christoph Hellwig
2017-05-24 16:41 ` [PATCH 04/10] fs: Introduce RWF_NOWAIT Goldwyn Rodrigues
2017-05-25  8:30   ` Jan Kara
2017-05-24 16:41 ` [PATCH 06/10] fs: Introduce IOMAP_NOWAIT Goldwyn Rodrigues
2017-05-25  8:33   ` Jan Kara
2017-05-24 16:41 ` [PATCH 07/10] fs: return on congested block device Goldwyn Rodrigues
2017-05-24 16:41 ` [PATCH 08/10] ext4: nowait aio support Goldwyn Rodrigues
2017-05-24 16:41 ` [PATCH 09/10] xfs: " Goldwyn Rodrigues
2017-05-24 16:49   ` Darrick J. Wong
     [not found]   ` <20170524164150.9492-10-rgoldwyn-l3A5Bk7waGM@public.gmane.org>
2017-05-28  9:31     ` Christoph Hellwig
2017-05-29  2:38       ` Goldwyn Rodrigues
2017-05-29  8:21         ` Jan Kara
2017-05-29  8:33         ` Christoph Hellwig [this message]
     [not found]           ` <20170529083338.GC1899-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
2017-05-30 16:13             ` Goldwyn Rodrigues
2017-05-31  8:51               ` Jan Kara
2017-05-24 16:41 ` [PATCH 10/10] btrfs: " Goldwyn Rodrigues
  -- strict thread matches above, loose matches on Subject: below --
2017-06-15 15:59 [PATCH 0/10 v12] No wait AIO Goldwyn Rodrigues
2017-06-15 16:00 ` [PATCH 09/10] xfs: nowait aio support Goldwyn Rodrigues
2017-06-06 11:19 [PATCH 0/10 v11] No wait AIO Goldwyn Rodrigues
2017-06-06 11:19 ` [PATCH 09/10] xfs: nowait aio support Goldwyn Rodrigues
2017-06-05  5:35 [PATCH 0/10 v10] No wait AIO Goldwyn Rodrigues
2017-06-05  5:35 ` [PATCH 09/10] xfs: nowait aio support Goldwyn Rodrigues
2017-05-11 19:17 [PATCH 0/10 v8] No wait AIO Goldwyn Rodrigues
2017-05-11 19:17 ` [PATCH 09/10] xfs: nowait aio support Goldwyn Rodrigues

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