From 35bf659b008e83e725dcd30f542e38461dbb867c Mon Sep 17 00:00:00 2001 From: Mikulas Patocka Date: Thu, 2 Apr 2009 19:55:26 +0100 Subject: [PATCH] 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-format-patch failed