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Date:   Wed, 26 Jul 2023 15:14:40 -0700
From:   "Darrick J. Wong" <djwong@kernel.org>
To:     Dave Chinner <david@fromorbit.com>
Cc:     Hao Xu <hao.xu@linux.dev>, io-uring@vger.kernel.org,
        Jens Axboe <axboe@kernel.dk>,
        Dominique Martinet <asmadeus@codewreck.org>,
        Pavel Begunkov <asml.silence@gmail.com>,
        Christian Brauner <brauner@kernel.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Stefan Roesch <shr@fb.com>, Clay Harris <bugs@claycon.org>,
        linux-fsdevel@vger.kernel.org, linux-xfs@vger.kernel.org,
        linux-ext4@vger.kernel.org, Wanpeng Li <wanpengli@tencent.com>
Subject: Re: [PATCH 2/7] xfs: add nowait support for xfs_seek_iomap_begin()
Message-ID: <20230726221440.GB11352@frogsfrogsfrogs>
References: <20230726102603.155522-1-hao.xu@linux.dev>
 <20230726102603.155522-3-hao.xu@linux.dev>
 <ZMGWYyNz6SUTdRef@dread.disaster.area>
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On Thu, Jul 27, 2023 at 07:55:47AM +1000, Dave Chinner wrote:
> On Wed, Jul 26, 2023 at 06:25:58PM +0800, Hao Xu wrote:
> > From: Hao Xu <howeyxu@tencent.com>
> > 
> > To support nowait llseek(), IOMAP_NOWAIT semantics should be respected.
> > In xfs, xfs_seek_iomap_begin() is the only place which may be blocked
> > by ilock and extent loading. Let's turn it into trylock logic just like
> > what we've done in xfs_readdir().
> > 
> > Signed-off-by: Hao Xu <howeyxu@tencent.com>
> > ---
> >  fs/xfs/xfs_iomap.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> > 
> > diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
> > index 18c8f168b153..bbd7c6b27701 100644
> > --- a/fs/xfs/xfs_iomap.c
> > +++ b/fs/xfs/xfs_iomap.c
> > @@ -1294,7 +1294,9 @@ xfs_seek_iomap_begin(
> >  	if (xfs_is_shutdown(mp))
> >  		return -EIO;
> >  
> > -	lockmode = xfs_ilock_data_map_shared(ip);
> > +	lockmode = xfs_ilock_data_map_shared_generic(ip, flags & IOMAP_NOWAIT);
> 
> What does this magic XFS function I can't find anywhere in this
> patch set do?

It's in (iirc) the io_uring getdents patchset that wasn't cc'd to
linux-xfs and that I haven't looked at yet.

--D

> -Dave.
> -- 
> Dave Chinner
> david@fromorbit.com