From: Mikulas Patocka Date: Thu, 2 Apr 2009 18:55:26 +0000 (+0100) Subject: dm snapshot: avoid having two exceptions for the same chunk X-Git-Tag: v2.6.30-rc1~230^2~30 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=35bf659b008e83e725dcd30f542e38461dbb867c;p=pandora-kernel.git dm snapshot: avoid having two exceptions for the same chunk We need to check if the exception was completed after dropping the lock. After regaining the lock, __find_pending_exception checks if the exception was already placed into &s->pending hash. But we don't check if the exception was already completed and placed into &s->complete hash. If the process waiting in alloc_pending_exception was delayed at this point because of a scheduling latency and the exception was meanwhile completed, we'd miss that and allocate another pending exception for already completed chunk. It would lead to a situation where two records for the same chunk exist and potential data corruption because multiple snapshot I/Os to the affected chunk could be redirected to different locations in the snapshot. Cc: stable@kernel.org Signed-off-by: Mikulas Patocka Signed-off-by: Alasdair G Kergon --- Reading git-diff-tree failed