From: Omar Sandoval <osandov@osandov.com>
To: Al Viro <viro@ZenIV.linux.org.uk>
Cc: linux-btrfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
kernel-team@fb.com
Subject: Re: [PATCH 1/3] fs: add initial bh_result->b_private value to __blockdev_direct_IO()
Date: Fri, 11 May 2018 13:41:32 -0700 [thread overview]
Message-ID: <20180511204132.GF29366@vader> (raw)
In-Reply-To: <20180511203228.GF30522@ZenIV.linux.org.uk>
On Fri, May 11, 2018 at 09:32:28PM +0100, Al Viro wrote:
> On Fri, May 11, 2018 at 01:30:01PM -0700, Omar Sandoval wrote:
> > 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
Modifying kiocb isn't going to pan out, it's constructed way up in the
stack so that'd be a mess.
> > That leaves the callbacks, get_block, end_io, and submit_io. Perhaps we
> > can add those to inode_operations?
>
> Or, perhaps, btrfs shouldn't be using the common helper? The question
> is not where to stash the bits and pieces - it's how unreadable the callers
> are and how much boilerplate/hidden information is involved...
I need to call through to do_blockdev_direct_IO() eventually, I'm sure
no one wants me to reimplement the 200 lines in there :) so I'd be happy
to add a separate helper that only Btrfs uses, but if we're going to
call do_blockdev_direct_IO() eventually then we still need the 9
arguments in some form. Am I misunderstanding?
next prev parent reply other threads:[~2018-05-11 20:47 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-11 6:30 [PATCH 0/3] Btrfs: stop abusing current->journal_info for direct I/O Omar Sandoval
2018-05-11 6:30 ` [PATCH 1/3] fs: add initial bh_result->b_private value to __blockdev_direct_IO() Omar Sandoval
2018-05-11 20:05 ` Al Viro
2018-05-11 20:30 ` Omar Sandoval
2018-05-11 20:32 ` Al Viro
2018-05-11 20:41 ` Omar Sandoval [this message]
2018-05-14 16:35 ` David Sterba
2018-06-25 17:16 ` David Sterba
2018-06-29 7:02 ` Omar Sandoval
2018-05-11 6:30 ` [PATCH 2/3] fs: add private argument to dio_submit_t Omar Sandoval
2018-05-11 6:30 ` [PATCH 3/3] Btrfs: stop abusing current->journal_info in btrfs_direct_IO() Omar Sandoval
2018-05-11 9:26 ` [PATCH 0/3] Btrfs: stop abusing current->journal_info for direct I/O David Sterba
2018-05-11 9:53 ` Nikolay Borisov
2018-05-11 10:24 ` David Sterba
2018-05-11 17:28 ` Omar Sandoval
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