tree e89ac12fdb794b17fc107c757a79b6a27e5010bd
parent 0982368bfd59647b4f30415c9ed038f60b859875
author Lars Ellenberg <lars.ellenberg@linbit.com> 1465856779 +0200
committer Jens Axboe <axboe@fb.com> 1465875785 -0600

drbd: allow parallel flushes for multi-volume resources

To maintain write-order fidelity accros all volumes in a DRBD resource,
the receiver of a P_BARRIER needs to issue flushes to all volumes.
We used to do this by calling blkdev_issue_flush(), synchronously,
one volume at a time.

We now submit all flushes to all volumes in parallel, then wait for all
completions, to reduce worst-case latencies on multi-volume resources.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
Signed-off-by: Jens Axboe <axboe@fb.com>