Re: [PATCH 1/2] block: call blk_mq_exit_queue from disk_release for never added disks

[Ming Lei <ming.lei@redhat.com>]

On Mon, Jul 18, 2022 at 03:07:25PM +0200, Christoph Hellwig wrote:
> On Mon, Jul 18, 2022 at 03:18:52PM +0800, Ming Lei wrote:
> > Request queue is allocated successfully, but disk allocation may fail,
> > so blk_mq_exit_queue still may be missed in this case.
> 
> Yes.  That's a separate issue, though and solved by this one liner:
> 
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index d716b7f3763f3..70177ee74295b 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -3960,7 +3960,7 @@ struct gendisk *__blk_mq_alloc_disk(struct blk_mq_tag_set *set, void *queuedata,
>  
>  	disk = __alloc_disk_node(q, set->numa_node, lkclass);
>  	if (!disk) {
> -		blk_put_queue(q);
> +		blk_mq_destroy_queue(q);
>  		return ERR_PTR(-ENOMEM);

OK, but it is still tricky, since there isn't the required order between
calling blk_mq_free_tag_set and put_disk, but now put_disk has to be called
before calling blk_mq_free_tag_set, so you may have to audit drivers
first, and make sure that all put_disk is called before blk_mq_free_tag_set()
in driver's error handling code path.



Thanks,
Ming