Re: [PATCH v2] fs: Fix page cache inconsistency when mixing buffered and AIO DIO

[Lukas Czerner <lczerner@redhat.com>]

On Tue, Jul 18, 2017 at 11:06:26AM +0200, Jan Kara wrote:
> On Tue 18-07-17 09:39:35, Lukas Czerner wrote:
> > On Mon, Jul 17, 2017 at 11:39:09AM -0400, Jeff Moyer wrote:
> > > Lukas Czerner <lczerner@redhat.com> writes:
> > > 
> > > > About the error case, is it not possible that some data has already been
> > > > writtent to the disk despite the error ?
> > > 
> > > Yes, it's possible.  However, that data is in an inconsistent state, so
> > > it shouldn't be read, anyway.
> > 
> > I think it can be read if we wrote into already allocated space.
> > 
> > > 
> > > Now, in the non-async path, we do the invalidation unconditionally, so I
> > > could go either way on this.  I don't think it's going to matter for
> > > performance or data integrity.
> > 
> > That's part of the reason why I did it unconditionaly as well, however
> > Jan is right that ret would be negative. The way to fix it would differ
> > depending on whether I am right about reading partially written data
> > from AIO that failed. We still want to invalidate in that case.
> 
> Frankly, I don't think it really matters so I'd go for not invalidating
> anything on error just out of philosophy: "There's something weird going
> on, bail out as quickly as you can."
> 
> 								Honza

Fair enough, thanks!

-Lukas

> -- 
> Jan Kara <jack@suse.com>
> SUSE Labs, CR