[GIT PULL] One last block fix

[GIT PULL] One last block fix

[Jens Axboe]

Hi Linus,

We've had an issue with scsi-mq where probing takes forever. This was
bisected down to the percpu changes for blk_mq_queue_enter(), and the
fact we now suffer an RCU grace period when killing a queue. SCSI
creates and destroys tons of queues, so this let to 10s of seconds of
stalls at boot for some.

Tejun has a real fix for this, but it's too involved for 3.17. So this
is a temporary workaround to expedite the queue killing until we can
fold in the real fix for 3.18 when that merge window opens.

Please pull!

  git://git.kernel.dk/linux-block.git for-linus

for you to fetch changes up to 0a30288da1aec914e158c2d7a3482a85f632750f:

  blk-mq, percpu_ref: implement a kludge for SCSI blk-mq stall during probe (2014-09-24 08:29:36 -0600)

----------------------------------------------------------------
Tejun Heo (1):
      blk-mq, percpu_ref: implement a kludge for SCSI blk-mq stall during probe

 block/blk-mq.c                  | 11 ++++++++++-
 include/linux/percpu-refcount.h |  1 +
 lib/percpu-refcount.c           | 16 ++++++++++++++++
 3 files changed, 27 insertions(+), 1 deletion(-)

-- 
Jens Axboe