Re: [PATCH 1/6] iomap: convert iomap_dio_rw() to an args structure

[Dave Chinner <david@fromorbit.com>]

On Mon, Jan 11, 2021 at 05:40:23PM -0800, Darrick J. Wong wrote:
> On Tue, Jan 12, 2021 at 12:07:41PM +1100, Dave Chinner wrote:
> > From: Dave Chinner <dchinner@redhat.com>
> > 
> > Adding yet another parameter to the iomap_dio_rw() interface means
> > changing lots of filesystems to add the parameter. Convert this
> > interface to an args structure so in future we don't need to modify
> > every caller to add a new parameter.
> > 
> > Signed-off-by: Dave Chinner <dchinner@redhat.com>
> > ---
> >  fs/btrfs/file.c       | 21 ++++++++++++++++-----
> >  fs/ext4/file.c        | 24 ++++++++++++++++++------
> >  fs/gfs2/file.c        | 19 ++++++++++++++-----
> >  fs/iomap/direct-io.c  | 30 ++++++++++++++----------------
> >  fs/xfs/xfs_file.c     | 30 +++++++++++++++++++++---------
> >  fs/zonefs/super.c     | 21 +++++++++++++++++----
> >  include/linux/iomap.h | 16 ++++++++++------
> >  7 files changed, 110 insertions(+), 51 deletions(-)
> > 
> > diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
> > index 0e41459b8de6..a49d9fa918d1 100644
> > --- a/fs/btrfs/file.c
> > +++ b/fs/btrfs/file.c
> > @@ -1907,6 +1907,13 @@ static ssize_t btrfs_direct_write(struct kiocb *iocb, struct iov_iter *from)
> >  	ssize_t err;
> >  	unsigned int ilock_flags = 0;
> >  	struct iomap_dio *dio = NULL;
> > +	struct iomap_dio_rw_args args = {
> > +		.iocb			= iocb,
> > +		.iter			= from,
> > +		.ops			= &btrfs_dio_iomap_ops,
> > +		.dops			= &btrfs_dio_ops,
> 
> /me wonders if it would make sense to move all the iomap_dio_ops fields
> into iomap_dio_rw_args to reduce pointer dereferencing when making the
> indirect call?

Perhaps so - there are only two ops defined in that structure so
there's not a whole lot of gain/loss there either way.  Trivial to
do, though, with them encapsulated in this structure...

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com