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

["Darrick J. Wong" <darrick.wong@oracle.com>]

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.

--D