Allow freeze_bdev() to return an error.
Signed-Off-By: NAlasdair G Kergon <agk@redhat.com>
From: Christoph Hellwig <hch@lst.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>