Re: [PATCH 25/45] block: reference struct block_device from struct hd_struct

[Tejun Heo <tj@xxxxxxxxxx>]

Hello,

On Wed, Nov 25, 2020 at 05:45:15PM +0100, Christoph Hellwig wrote:
> On Tue, Nov 24, 2020 at 04:18:49PM -0500, Tejun Heo wrote:
> > Hello,
> > 
> > Please see lkml.kernel.org/r/X708BTJ5njtbC2z1@xxxxxxxxxxxxxxx for a few nits
> > on the previous version.
> 
> Thanks, I've addressed the mapping_set_gfp mask nit and updated the
> commit log.  As Jan pointed also pointed out I think we do need the
> remove_inode_hash.

Agreed. It'd be nice to replace the stale comment.

> > Also, would it make sense to separate out lookup_sem removal? I *think* it's
> > there to ensure that the same bdev doesn't get associated with old and new
> > gendisks at the same time but can't wrap my head around how it works
> > exactly. I can see that this may not be needed once the lifetimes of gendisk
> > and block_devices are tied together but that may warrant a bit more
> > explanation.
> 
> Jan added lookup_sem in commit 56c0908c855afbb to prevent a three way
> race between del_gendisk and blkdev_open due to the weird bdev vs
> gendisk lifetime rules.  None of that can happen with the new lookup
> scheme.

Understood. I think it'd be worthwhile to note that in the commit log.

Thanks.

-- 
tejun