tree dacf7f8eca75dc0d92566b5d3876f3efe8196e35
parent fccdae435c1b295cca546f23f6f43126a28ffac3
author Sage Weil <sage@newdream.net> 1288381054 -0400
committer Chris Mason <chris.mason@oracle.com> 1288381054 -0400

Btrfs: fix deadlock in btrfs_commit_transaction

We calculate timeout (either 1 or MAX_SCHEDULE_TIMEOUT) based on whether
num_writers > 1 or should_grow at the top of the loop.  Then, much much
later, we wait for that timeout if either num_writers or should_grow is
true.  However, it's possible for a racing process (calling
btrfs_end_transaction()) to decrement num_writers such that we wait
forever instead of for 1.

Fix this by deciding how long to wait when we wait.  Include a smp_mb()
before checking if the waitqueue is active to ensure the num_writers
is visible.

Signed-off-by: Sage Weil <sage@newdream.net>
Signed-off-by: Chris Mason <chris.mason@oracle.com>