Messages in this thread | | | Date | Mon, 14 Jun 2010 11:20:11 -0400 | From | Christoph Hellwig <> | Subject | Re: [PATCH 2/5] fsfreeze: emergency thaw will deadlock on s_umount |
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On Thu, Jun 10, 2010 at 05:19:51PM +1000, Dave Chinner wrote: > The emergency thaw process uses iterate_super() which holds the > sb->s_umount lock in read mode. The current thaw_super() code takes > the sb->s_umount lock in write mode, hence leading to an instant > deadlock. > > Pass the emergency state into the thaw_bdev/thaw_super code to avoid > taking the s_umount lock in this case. We are running under the bdev > freeze mutex, so this is still serialised against freeze despite > only having a read lock on the sb->s_umount. Hence it should be safe > to execute in this manner, especially given that emergency thaw is a > rarely executed "get-out-of-jail" feature.
This is correct as long as no one calls thaw_super directly, which is not the case currently.
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