Re: [PATCH v2] block: add a new flag BLK_MQ_POLL_CLASSIC for hybrid poll

[yuyufen]

Hi,


On 2019/3/11 21:51, Damien Le Moal wrote:

On 2019/03/11 6:31, yuyufen wrote:

ping?


On 2019/3/1 9:28, Yufen Yu wrote:

For q->poll_nsec == -1, means doing classic poll, not hybrid poll.
We introduce a new flag BLK_MQ_POLL_CLASSIC to replace -1, which
may make code much easier to read.

Signed-off-by: Yufen Yu <yuyu...@huawei.com>
---
   block/blk-mq.c         | 4 ++--
   block/blk-sysfs.c      | 4 ++--
   include/linux/blkdev.h | 3 +++
   3 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 9437a5eb07cf..e70202e3b378 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2857,7 +2857,7 @@ struct request_queue *blk_mq_init_allocated_queue(struct 
blk_mq_tag_set *set,
        /*
         * Default to classic polling
         */
-       q->poll_nsec = -1;
+       q->poll_nsec = BLK_MQ_POLL_CLASSIC;

blk_mq_init_cpu_queues(q, set->nr_hw_queues);

        blk_mq_add_queue_tag_set(set, q);
@@ -3389,7 +3389,7 @@ static bool blk_mq_poll_hybrid(struct request_queue *q,
   {
        struct request *rq;

- if (q->poll_nsec == -1)

+       if (q->poll_nsec == BLK_MQ_POLL_CLASSIC)
                return false;

if (!blk_qc_t_is_internal(cookie))

diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 590d1ef2f961..8639e135687e 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -360,7 +360,7 @@ static ssize_t queue_poll_delay_show(struct request_queue 
*q, char *page)
   {
        int val;

- if (q->poll_nsec == -1)

+       if (q->poll_nsec == BLK_MQ_POLL_CLASSIC)
                val = -1;
        else
                val = q->poll_nsec / 1000;
@@ -381,7 +381,7 @@ static ssize_t queue_poll_delay_store(struct request_queue 
*q, const char *page,
                return err;

if (val == -1)

Since val is an int obtained with kstrtoint(), val can be a negative value other
than -1. So what about something like:

        if (val == BLK_MQ_POLL_CLASSIC)
                q->poll_nsec = BLK_MQ_POLL_CLASSIC;
        else if (val >= 0)
                q->poll_nsec = val * 1000;
        else
                return -EINVAL;

That would avoid problems with negative values other than -1.

I agree with you. This may be more reasonable.
Thanks a lot for your suggestion.

Yufen.
Thanks

-               q->poll_nsec = -1;
+               q->poll_nsec = BLK_MQ_POLL_CLASSIC;
        else
                q->poll_nsec = val * 1000;

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h

index 338604dff7d0..f9c2ebf5e621 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -50,6 +50,9 @@ struct blk_stat_callback;
   /* Must be consistent with blk_mq_poll_stats_bkt() */
   #define BLK_MQ_POLL_STATS_BKTS 16

+/* Doing classic polling */

+#define BLK_MQ_POLL_CLASSIC -1
+
   /*
    * Maximum number of blkcg policies allowed to be registered concurrently.
    * Defined here to simplify include dependency.