Re: [PATCH 0/2] iomap: Waiting for IO in iomap_dio_rw()

[Jan Kara <jack@suse.cz>]

On Thu 10-10-19 07:47:18, Darrick J. Wong wrote:
> On Thu, Oct 10, 2019 at 12:54:20AM -0700, Christoph Hellwig wrote:
> > On Thu, Oct 10, 2019 at 10:02:27AM +1100, Dave Chinner wrote:
> > > That would mean the callers need to do something like this by
> > > default:
> > > 
> > > 	ret = iomap_dio_rw(iocb, iter, ops, dops, is_sync_kiocb(iocb));
> > > 
> > > And filesystems like XFS will need to do:
> > > 
> > > 	ret = iomap_dio_rw(iocb, iter, ops, dops,
> > > 			is_sync_kiocb(iocb) || unaligned);
> > > 
> > > and ext4 will calculate the parameter in whatever way it needs to.
> > 
> > I defintively like that.
> > 
> > > 
> > > In fact, it may be that a wrapper function is better for existing
> > > callers:
> > > 
> > > static inline ssize_t iomap_dio_rw()
> > > {
> > > 	return iomap_dio_rw_wait(iocb, iter, ops, dops, is_sync_kiocb(iocb));
> > > }
> > > 
> > > And XFS/ext4 writes call iomap_dio_rw_wait() directly. That way we
> > > don't need to change the read code at all...
> > 
> > I have to say I really hated the way we were growing all these wrappers
> > in the old direct I/O code, so I've been asked Jan to not add the
> > wrapper in his old version.  But compared to the force_sync version it
> > at least makes a little more sense here.  I'm just not sure if
> > iomap_dio_rw_wait is the right name, but the __-prefix convention for
> > non-trivial differences also sucks.  I can't think of a better name,
> > though.
> 
> <shrug> I'd just add the 'bool wait' parameter at the end of
> iomap_dio_rw() and leave it that way.  If we ever develop more than one
> caller that passes in "is_sync_kiocb(iocb)" (or more than two lucky
> callers screwing it up I guess?) for that parameter then maybe we can
> re-evaluate.

OK, fine by me. I guess this is the least controversial proposal so I'll
resend patches with this change tomorrow...

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