tree a1954f352d16307d0846e42b2246be6b1594fb9b
parent da8303c63b8de73619884382d6e573d44aae0810
author Tejun Heo <tj@kernel.org> 1319027588 +0200
committer Jens Axboe <axboe@kernel.dk> 1319027588 +0200

block: drop @tsk from attempt_plug_merge() and explain sync rules

attempt_plug_merge() accesses elevator without holding queue_lock and
may call into ->elevator_bio_merge_fn().  The elvator is guaranteed to
be valid because it's accessed iff the plugged list has requests and
elevator is never exited with live requests, so as long as the
elevator method can deal with unlocked access, this is safe.

Explain the sync rules around attempt_plug_merge() and drop the
unnecessary @tsk parameter.

This patch doesn't introduce any functional change.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>