[dm-devel] [PATCH RFC 2/7] block: add helper function fetching gendisk from queue

[Mike Snitzer]

On Wed, Dec 23 2020 at  6:26am -0500,
Jeffle Xu <jefflexu at linux.alibaba.com> wrote:

> Sometimes we need to get the corresponding gendisk from request_queue.
> 
> One such use case is that, the block device driver had ever stored the
> same private data both in queue->queuedata and gendisk->private_data,
> while nowadays gendisk->private_data is more preferable in such case,
> e.g. commit c4a59c4e5db3 ("dm: stop using ->queuedata"). So if only
> request_queue given, we need to get the corresponding gendisk from
> queue, to get the private data stored in gendisk.
> 
> Signed-off-by: Jeffle Xu <jefflexu at linux.alibaba.com>
> ---
>  include/linux/blkdev.h       | 2 ++
>  include/trace/events/kyber.h | 6 +++---
>  2 files changed, 5 insertions(+), 3 deletions(-)

Looks good, but please update the patch subject and header to be:

block: add queue_to_disk() to get gendisk from request_queue

Sometimes we need to get the corresponding gendisk from request_queue.

It is preferred that block drivers store private data in
gendisk->private_data rather than request_queue->queuedata, e.g. see:
commit c4a59c4e5db3 ("dm: stop using ->queuedata").

So if only request_queue is given, we need to get its corresponding
gendisk to get the private data stored in that gendisk.

Signed-off-by: Jeffle Xu <jefflexu at linux.alibaba.com>
Review-by: Mike Snitzer <snitzer at redhat.com>