On Wed, Aug 30, 2023 at 02:11:31PM +0800, Hao Xu wrote: > On 8/29/23 19:53, Matthew Wilcox wrote: > > 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 > > I'm ok to do that. > > > 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. > > Hi Matthew, > The previous discussion shows this does cause issues in real > producations: https://lore.kernel.org/io-uring/2785f009-2ebb-028d-8250-d5f3a30510f0@xxxxxxxxx/#:~:text=fwiw%2C%20we%27ve%20just%20recently%20had%20similar%20problems%20with%20io_uring%20read/write > Then separate it out into it's own patch set so we can have a discussion on the merits of requiring using noatime, relatime or lazytime for really latency sensitive IO applications. Changing code is not always the right solution... -Dave. -- Dave Chinner david@xxxxxxxxxxxxx
