[PATCH 2/2] ubi: block: Fix deadlock on remove

[Vincent Whitchurch]

On Tue, 2023-05-23 at 23:04 -0700, Christoph Hellwig wrote:
> If you imlement ->free_disk, the list_del and kfree can move into
> that, and we don't really care if a new opener raced with the delete.

Moving the kfree() to ->free_disk() works, but the list_del() still
needs to be in ubiblock_remove() since otherwise ubiblock_remove() could
attempt to remove the same device twice.

I assumed the current code really wanted to prevent new openers racing
with delete, but if that is not needed, yes, we don't need to add a
->removing flag if we move the kfree() to ->free_disk().  I'll re-spin
this based on your suggestions.  Thanks.