Kiyoshi Ueda f88fb98118 dm: dec_pending needs locking to save error value
Multiple instances of dec_pending() can run concurrently so a lock is
needed when it saves the first error code.

I have never experienced actual problem without locking and just found
this during code inspection while implementing the barrier support
patch for request-based dm.

This patch adds the locking.
I've done compile, boot and basic I/O testings.

Cc: stable@kernel.org
Signed-off-by: Kiyoshi Ueda <k-ueda@ct.jp.nec.com>
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-10-16 23:18:15 +01:00
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