Btrfs: fix inode cache waiters hanging on failure to start caching thread

Btrfs: fix inode cache waiters hanging on failure to start caching thread

BugLink: https://bugs.launchpad.net/bugs/1863019
[ Upstream commit a68ebe0790fc88b4314d17984a2cf99ce2361901 ]

If we fail to start the inode caching thread, we print an error message
and disable the inode cache, however we never wake up any waiters, so they
hang forever waiting for the caching to finish. Fix this by waking them
up and have them fallback to a call to btrfs_find_free_objectid().

Fixes: e60efa84252c05 ("Btrfs: avoid triggering bug_on() when we fail to start inode caching task")
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>