Re: [PATCH v2 00/34] Open block devices as files

Jan Kara
2024-02-05T14:19:18Z

Hi!

On Mon 05-02-24 12:55:18, Christian Brauner wrote:
> On Tue, Jan 23, 2024 at 02:26:17PM +0100, Christian Brauner wrote:
> > Hey Christoph,
> > Hey Jan,
> > Hey Jens,
> >
> > This opens block devices as files. Instead of introducing a separate
> > indirection into bdev_open_by_*() vis struct bdev_handle we can just
> > make bdev_file_open_by_*() return a struct file. Opening and closing a
> > block device from setup_bdev_super() and in all other places just
> > becomes equivalent to opening and closing a file.
> >
> > This has held up in xfstests and in blktests so far and it seems stable
> > and clean. The equivalence of opening and closing block devices to
> > regular files is a win in and of itself imho. Added to that is the
> > ability to do away with struct bdev_handle completely and make various
> > low-level helpers private to the block layer.
> >
> > All places were we currently stash a struct bdev_handle we just stash a
> > file and use an accessor such as file_bdev() akin to I_BDEV() to get to
> > the block device.
> >
> > It's now also possible to use file->f_mapping as a replacement for
> > bdev->bd_inode->i_mapping and file->f_inode or file->f_mapping->host as
> > an alternative to bdev->bd_inode allowing us to significantly reduce or
> > even fully remove bdev->bd_inode in follow-up patches.
> >
> > In addition, we could get rid of sb->s_bdev and various other places
> > that stash the block device directly and instead stash the block device
> > file. Again, this is follow-up work.
> >
> > Thanks!
> > Christian
> >
> > Signed-off-by: Christian Brauner <brauner@kernel.org>
> > ---
>
> With all fixes applied I've moved this into vfs.super on vfs/vfs.git so
> this gets some exposure in -next asap. Please let me know if you have
> quarrels with that.

No quarrels really. I went through the patches and all of them look fine to
me to feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

I have just noticed that in "bdev: make struct bdev_handle private to the
block layer" in bdev_open() we are still leaking the handle in case of
error. This is however temporary (until the end of the series when we get
rid of handles altogether) so whatever.

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