On Wed, Oct 5, 2016 at 12:16 PM, Bart Van Assche
[off-list ref] wrote:

On 10/01/16 15:56, Ming Lei wrote:

quoted

If we just call the rcu/srcu read lock(or the mutex) around .queue_rq(),
the
above code needn't to be duplicated any more.

Hello Ming,

Can you have a look at the attached patch? That patch uses an srcu read lock
for all queue types, whether or not the BLK_MQ_F_BLOCKING flag has been set.

That is much cleaner now.

Additionally, I have dropped the QUEUE_FLAG_QUIESCING flag. Just like
previous versions, this patch has been tested.

I think the flag of QUEUE_FLAG_QUIESCING is still needed because we
have to set this flag to prevent new coming .queue_rq() from being run,
and synchronize_srcu() won't wait for completion of that at all (see
section of 'Update-Side Primitives' in [1]).


[1] https://lwn.net/Articles/202847/

-- 
Ming Lei