Re: [PATCH v2 08/11] blk-mq: Add blk_mq_ops.init_request_no_hctx()

Ming Lei
2021-08-18T07:39:09Z

On Mon, Aug 09, 2021 at 10:29:35PM +0800, John Garry wrote:
> Add a variant of the init_request function which does not pass a hctx_idx
> arg.
>
> This is important for shared sbitmap support, as it needs to be ensured for
> introducing shared static rqs that the LLDD cannot think that requests
> are associated with a specific HW queue.
>
> Signed-off-by: John Garry <john.garry@huawei.com>
> ---
> block/blk-mq.c | 15 ++++++++++-----
> include/linux/blk-mq.h | 7 +++++++
> 2 files changed, 17 insertions(+), 5 deletions(-)
>
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index f14cc2705f9b..4d6723cfa582 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -2427,13 +2427,15 @@ struct blk_mq_tags *blk_mq_alloc_rq_map(struct blk_mq_tag_set *set,
> static int blk_mq_init_request(struct blk_mq_tag_set *set, struct request *rq,
> unsigned int hctx_idx, int node)
> {
> - int ret;
> + int ret = 0;
>
> - if (set->ops->init_request) {
> + if (set->ops->init_request)
> ret = set->ops->init_request(set, rq, hctx_idx, node);
> - if (ret)
> - return ret;
> - }
> + else if (set->ops->init_request_no_hctx)
> + ret = set->ops->init_request_no_hctx(set, rq, node);

The only shared sbitmap user of SCSI does not use passed hctx_idx, not
sure we need such new callback.

If you really want to do this, just wondering why not pass '-1' as
hctx_idx in case of shared sbitmap?

Thanks,
Ming