Hi,
在 2024/04/07 9:51, Al Viro 写道:
On Sun, Apr 07, 2024 at 09:18:20AM +0800, Yu Kuai wrote:
Yes, patch 23-26 already do the work to remove the field block_device
and convert to use bdev_file for iomap and buffer_head.
What for? I mean, what makes that dummy struct file * any better than
struct block_device *? What's the point?
I agree that keeping an opened struct file for a block device is
a good idea - certainly better than weird crap used to carry the
"how had it been opened" along with bdev. But that does *not*
mean not keeping ->s_bdev around; we might or might not find that
convenient, but it's not "struct block_device is Evil(tm), let's
exorcise".
Why do we care to do anything to struct buffer_head? Or to
struct bio, for that matter...
Other than raw block_device fops, other filesystems can use the opened
bdev_file directly for iomap and buffer_head, and they actually don't
need to reference block_device anymore. The point here is that whether
we want to keep a special handling for block_device fops or not. There
are two proposes now:
- one is from Christian to keep using block_device for block_device
fops, in order to do that, a new flag and some special handling is added
to iomap and buffer_head. See the patch from last version [1].
- one is from this patchset, allocate a *dummy* bdev_file just for iomap
and buffer_head to access bdev and bd_inode.
I personally prefer the later one, that's why there is a new version,
however, what do I know? That will depend on how people think.
[1]
https://lore.kernel.org/all/20240222124555.2049140-20-yukuai1@xxxxxxxxxxxxxxx/
Thanks,
Kuai
I'm not saying that parts of the patchset do not make sense on
their own, but I don't understand what the last part is all
about.
Al, still going through that series...
.
