Re: [PATCH 07/11] vfs: add nowait parameter for file_accessed()

[Matthew Wilcox]

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@xxxxxxxxxxx>
> > > 
> > > 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.