Re: [PATCH v2 2/3] block: don't hide inode from block_device users

[Pavel Begunkov]

On 10/13/21 16:25, Christoph Hellwig wrote:
> On Wed, Oct 13, 2021 at 09:57:12AM +0100, Pavel Begunkov wrote:
> > Instead of tricks with struct bdev_inode, just openly place the inode
> > inside struct block_device. First, it allows us to inline I_BDEV, which
> > is simple but non-inline nature of it impacts performance. Also, make it
> > possible to get rid of ->bd_inode pointer and hooping with extra
> > indirection, the amount of which became a noticeable problem for the
> > block layer.
>
> What fast path outside of bdev.c cares about an inlined I_BDEV?

Mildly hot in io_uring w/o fixed files, but that's not peak perf,
but would also be great to get rid of bdev->bd_inode dereference,
e.g. lots of in fops.c.

Are you going to just hid the dereference in helpers or kill it
with some offseting magic?


> I have dusted off patches to reduce (and hopefully eventually kill)
> accesses to bd_inode outside of bdev.c, so this goes into the wrong
> direction.
>
> If needed I'd rather figure out a way to fix any smoking gun without
> this change.

--
Pavel Begunkov