Re: [PATCH v2 24/35] block: null_blk: fix opencoded find_and_set_bit() in get_tag()

Chengming Zhou
2023-12-05T02:39:43Z

On 2023/12/4 03:32, Yury Norov wrote:
> get_tag() opencodes find_and_set_bit(). Switch the code to use the
> dedicated function, and get rid of get_tag entirely.
>
> Signed-off-by: Yury Norov <yury.norov@gmail.com>

Looks good to me!

Reviewed-by: Chengming Zhou <zhouchengming@bytedance.com>

> ---
> drivers/block/null_blk/main.c | 41 +++++++++++------------------------
> 1 file changed, 13 insertions(+), 28 deletions(-)
>
> diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c
> index 3021d58ca51c..671dbb9ab928 100644
> --- a/drivers/block/null_blk/main.c
> +++ b/drivers/block/null_blk/main.c
> @@ -760,19 +760,6 @@ static void put_tag(struct nullb_queue *nq, unsigned int tag)
> wake_up(&nq->wait);
> }
>
> -static unsigned int get_tag(struct nullb_queue *nq)
> -{
> - unsigned int tag;
> -
> - do {
> - tag = find_first_zero_bit(nq->tag_map, nq->queue_depth);
> - if (tag >= nq->queue_depth)
> - return -1U;
> - } while (test_and_set_bit_lock(tag, nq->tag_map));
> -
> - return tag;
> -}
> -
> static void free_cmd(struct nullb_cmd *cmd)
> {
> put_tag(cmd->nq, cmd->tag);
> @@ -782,24 +769,22 @@ static enum hrtimer_restart null_cmd_timer_expired(struct hrtimer *timer);
>
> static struct nullb_cmd *__alloc_cmd(struct nullb_queue *nq)
> {
> + unsigned int tag = find_and_set_bit_lock(nq->tag_map, nq->queue_depth);
> struct nullb_cmd *cmd;
> - unsigned int tag;
> -
> - tag = get_tag(nq);
> - if (tag != -1U) {
> - cmd = &nq->cmds[tag];
> - cmd->tag = tag;
> - cmd->error = BLK_STS_OK;
> - cmd->nq = nq;
> - if (nq->dev->irqmode == NULL_IRQ_TIMER) {
> - hrtimer_init(&cmd->timer, CLOCK_MONOTONIC,
> - HRTIMER_MODE_REL);
> - cmd->timer.function = null_cmd_timer_expired;
> - }
> - return cmd;
> +
> + if (tag >= nq->queue_depth)
> + return NULL;
> +
> + cmd = &nq->cmds[tag];
> + cmd->tag = tag;
> + cmd->error = BLK_STS_OK;
> + cmd->nq = nq;
> + if (nq->dev->irqmode == NULL_IRQ_TIMER) {
> + hrtimer_init(&cmd->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
> + cmd->timer.function = null_cmd_timer_expired;
> }
>
> - return NULL;
> + return cmd;
> }
>
> static struct nullb_cmd *alloc_cmd(struct nullb_queue *nq, struct bio *bio)