Re: [PATCH 3/5] blktrace: refcount the request_queue during ioctl

[Bart Van Assche]

On 2020-04-15 18:12, Luis Chamberlain wrote:
> On Wed, Apr 15, 2020 at 07:18:22AM -0700, Bart Van Assche wrote:
>> blk_get_queue() prevents concurrent freeing of struct request_queue but
>> does not prevent concurrent blk_cleanup_queue() calls.
> 
> Wouldn't concurrent blk_cleanup_queue() calls be a bug? If so should
> I make it clear that it would be or simply prevent it?

I think calling blk_cleanup_queue() while the queue refcount > 0 is well
established behavior. At least the SCSI core triggers that behavior
since a very long time. I prefer not to change that behavior.

Regarding patch 3/5: how about dropping that patch? If the queue
refcount can drop to zero while blk_trace_ioctl() is in progress I think
that should be fixed in the block_device_operations.open callback
instead of in blk_trace_ioctl().

Thanks,

Bart.