From mboxrd@z Thu Jan  1 00:00:00 1970
From: Matthew Wilcox <willy@infradead.org>
Subject: Re: [PATCH 07/11] vfs: add nowait parameter for file_accessed()
Date: Tue, 29 Aug 2023 12:53:07 +0100
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To: Hao Xu <hao.xu@linux.dev>
Cc: 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>, Dave Chinner <david@fromorbit.com>, "Darrick J . Wong" <djwong@kernel.org>, linux-fsdevel@vger.kernel.org, linux-xfs@vger.kernel.org, linux-ext4@vger.kernel.org, linux-cachefs@redhat.com, ecryptfs@vger.kernel.org, linux-nfs@vger.kernel.org, linux-unionfs@vger.kernel.org, bpf@vger.kernel.org, netdev@vger.kernel.org, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, linux-btrfs@vger.kernel.org, codalist@coda.cs.cmu.edu, linux-f2fs-devel@lists.sourceforge.net, cluster-devel@redhat.com, linux-mm@kvack.org, linux-nilfs@vger.kernel.org, devel@lists.orangefs.

On Tue, Aug 29, 2023 at 03:46:13PM +0800, Hao Xu wrote:
> On 8/28/23 05:32, Matthew Wilcox wrote:
> > On Sun, Aug 27, 2023 at 09:28:31PM +0800, Hao Xu wrote:
> > > From: Hao Xu <howeyxu@tencent.com>
> > > 
> > > Add a boolean parameter for file_accessed() to support nowait semantics.
> > > Currently it is true only with io_uring as its initial caller.
> > 
> > So why do we need to do this as part of this series?  Apparently it
> > hasn't caused any problems for filemap_read().
> > 
> 
> We need this parameter to indicate if nowait semantics should be enforced in
> touch_atime(), There are locks and maybe IOs in it.

That's not my point.  We currently call file_accessed() and
touch_atime() for nowait reads and nowait writes.  You haven't done
anything to fix those.

I suspect you can trim this patchset down significantly by avoiding
fixing the file_accessed() problem.  And then come back with a later
patchset that fixes it for all nowait i/o.  Or do a separate prep series
first that fixes it for the existing nowait users, and then a second
series to do all the directory stuff.

I'd do the first thing.  Just ignore the problem.  Directory atime
updates cause I/O so rarely that you can afford to ignore it.  Almost
everyone uses relatime or nodiratime.