[dm-devel] [PATCH 7/7] dm-mpath: Fix a race condition in __multipath_map()

[Bart Van Assche]

On 11/15/2016 05:01 PM, Mike Snitzer wrote:
> On Tue, Nov 15 2016 at  7:40pm -0500,
> Bart Van Assche <bart.vanassche at sandisk.com> wrote:
>> Are you aware that dm_table_determine_type() sets "all_blk_mq" to
>> false if there are no paths, even if the dm device is in blk-mq
>> mode?
>
> That shouldn't matter.  Once the type is established, it is used to
> initialize the DM device's request_queue, the type cannot change across
> different table loads.

For a single queue dm device, what prevents a user from removing all 
single queue paths and to add one or more blk-mq paths? I think this 
will cause dm_table_determine_type() to change the table type.

Bart.