Re: [PATCH] Btrfs: remove rcu_barrier in btrfs_close_devices

[David Sterba <dsterba@suse.cz>]

On Wed, Oct 11, 2017 at 11:02:49AM -0600, Liu Bo wrote:
> On Wed, Oct 11, 2017 at 03:41:23PM +0800, Anand Jain wrote:
> > 
> > 
> > On 10/11/2017 02:11 PM, Anand Jain wrote:
> > > 
> > > 
> > > On 10/11/2017 05:51 AM, Liu Bo wrote:
> > > > It was introduced because btrfs used to do blkdev_put in a deferred
> > > > work, now that btrfs has put blkdev in place, this rcu_barrier can be
> > > > removed.
> > 
> >  On the 2nd thought, modprobe -r btrfs would still need rcu_barrier(), some
> > where else outside of umount context ?
> 
> Thanks a lot for the comments.
> 
> modprobe -r btrfs will do btrfs_cleanup_fs_uuids(), where it cleanup
> every %fs_devices on the list, but when we do btrfs_close_devices(), we
> have replaced the devices on the list with dummy ones which only have
> the same name and uuid, so modprobe -r btrfs will free those instead
> of what we were using, this change won't cause a problem for it.

Added to the changelog.

Reviewed-by: David Sterba <dsterba@suse.com>