tree 01611f6d35c041a941269cb3dd3926c0711722ae
parent dc86900e0a8f665122de6faadd27fb4c6d2b3e4d
author Tejun Heo <tj@kernel.org> 1323819218 +0100
committer Jens Axboe <axboe@kernel.dk> 1323819218 +0100

block, cfq: fix race condition in cic creation path and tighten locking

cfq_get_io_context() would fail if multiple tasks race to insert cic's
for the same association.  This patch restructures
cfq_get_io_context() such that slow path insertion race is handled
properly.

Note that the restructuring also makes cfq_get_io_context() called
under queue_lock and performs both ioc and cfqd insertions while
holding both ioc and queue locks.  This is part of on-going locking
tightening and will be used to simplify synchronization rules.

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