Re: [PATCH 1/3] fs: add initial bh_result->b_private value to __blockdev_direct_IO()

[Omar Sandoval <osandov@osandov.com>]

On Fri, May 11, 2018 at 09:05:38PM +0100, Al Viro wrote:
> On Thu, May 10, 2018 at 11:30:10PM -0700, Omar Sandoval wrote:
> >  do_blockdev_direct_IO(struct kiocb *iocb, struct inode *inode,
> >  		      struct block_device *bdev, struct iov_iter *iter,
> >  		      get_block_t get_block, dio_iodone_t end_io,
> > -		      dio_submit_t submit_io, int flags)
> > +		      dio_submit_t submit_io, int flags, void *private)
> 
> Oh, dear...  That's what, 9 arguments?  I agree that the hack in question
> is obscene, but so is this ;-/

So looking at these one by one, obviously needed:

- iocb
- inode
- iter

bdev is almost always inode->i_sb->s_bdev, except for Btrfs :(

These could _maybe_ go in struct kiocb:

- flags could maybe be folded into ki_flags
- private could maybe go in iocb->private, but I haven't yet read
  through to figure out if we're already using iocb->private for direct
  I/O

That leaves the callbacks, get_block, end_io, and submit_io. Perhaps we
can add those to inode_operations?

Thoughts?