From: "Darrick J. Wong" <darrick.wong@oracle.com>
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,
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 7/8] nowait aio: xfs
Date: Fri, 7 Apr 2017 08:08:51 -0700 [thread overview]
Message-ID: <20170407150851.GC4853@birch.djwong.org> (raw)
In-Reply-To: <6cc69b0c-7af4-879e-1012-aae8ba5358bd@suse.de>
On Fri, Apr 07, 2017 at 06:34:28AM -0500, Goldwyn Rodrigues wrote:
>
>
> On 04/06/2017 05:54 PM, Darrick J. Wong wrote:
> > On Mon, Apr 03, 2017 at 11:52:11PM -0700, Christoph Hellwig wrote:
> >>> + if (unaligned_io) {
> >>> + /* If we are going to wait for other DIO to finish, bail */
> >>> + if ((iocb->ki_flags & IOCB_NOWAIT) &&
> >>> + atomic_read(&inode->i_dio_count))
> >>> + return -EAGAIN;
> >>> inode_dio_wait(inode);
> >>
> >> This checks i_dio_count twice in the nowait case, I think it should be:
> >>
> >> if (iocb->ki_flags & IOCB_NOWAIT) {
> >> if (atomic_read(&inode->i_dio_count))
> >> return -EAGAIN;
> >> } else {
> >> inode_dio_wait(inode);
> >> }
> >>
> >>> if ((flags & (IOMAP_WRITE | IOMAP_ZERO)) && xfs_is_reflink_inode(ip)) {
> >>> if (flags & IOMAP_DIRECT) {
> >>> + /* A reflinked inode will result in CoW alloc */
> >>> + if (flags & IOMAP_NOWAIT) {
> >>> + error = -EAGAIN;
> >>> + goto out_unlock;
> >>> + }
> >>
> >> This is a bit pessimistic - just because the inode has any shared
> >> extents we could still write into unshared ones. For now I think this
> >> pessimistic check is fine, but the comment should be corrected.
> >
> > Consider what happens in both _reflink_{allocate,reserve}_cow. If there
> > is already an existing reservation in the CoW fork then we'll have to
> > CoW and therefore can't satisfy the NOWAIT flag. If there isn't already
> > anything in the CoW fork, then we have to see if there are shared blocks
> > by calling _reflink_trim_around_shared. That performs a refcountbt
> > lookup, which involves locking the AGF, so we also can't satisfy NOWAIT.
> >
> > IOWs, I think this hunk has to move outside the IOMAP_DIRECT check to
> > cover both write-to-reflinked-file cases.
> >
>
> IOMAP_NOWAIT is set only with IOMAP_DIRECT since the nowait feature is
> for direct-IO only. This is checked early on, when we are checking for
Ah, ok. Disregard what I said about moving it then.
--D
> user-passed flags, and if not, -EINVAL is returned.
>
>
> --
> Goldwyn
next prev parent reply other threads:[~2017-04-07 15:08 UTC|newest]
Thread overview: 27+ 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
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 [this message]
-- 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 7/8] nowait aio: xfs Goldwyn Rodrigues
2017-05-11 7:45 ` Christoph Hellwig
2017-04-14 12:02 [PATCH 0/8 v6] No wait AIO Goldwyn Rodrigues
2017-04-14 12:02 ` [PATCH 7/8] nowait aio: xfs Goldwyn Rodrigues
2017-04-19 6:45 ` Christoph Hellwig
2017-03-15 21:50 [PATCH 0/8 v3] No wait AIO Goldwyn Rodrigues
2017-03-15 21:51 ` [PATCH 7/8] nowait aio: xfs 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=20170407150851.GC4853@birch.djwong.org \
--to=darrick.wong@oracle.com \
--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 \
/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
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
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).