block: add BLK_MQ_POLL_CLASSIC for hybrid poll and return EINVAL for unexpected value

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.

Additionally, since val is an int obtained with kstrtoint(), val can be
a negative value other than -1, so return -EINVAL for that case.

Thanks to Damien Le Moal for some good suggestion.

Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Yufen Yu <yuyufen@huawei.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

3 files changed, 12 insertions, 7 deletions

diff --git a/block/blk-mq.c b/block/blk-mq.c
index ea01c23b58a3..76a3f78c566a 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2856,7 +2856,7 @@ 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);
@@ -3391,7 +3391,7 @@ 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 59685918167e..422327089e0f 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -360,8 +360,8 @@ static ssize_t queue_poll_delay_show(struct request_queue *q, char *page)
 {
         int val;
 
-        if (q->poll_nsec == -1)
-                val = -1;
+        if (q->poll_nsec == BLK_MQ_POLL_CLASSIC)
+                val = BLK_MQ_POLL_CLASSIC;
         else
                 val = q->poll_nsec / 1000;
 
@@ -380,10 +380,12 @@ static ssize_t queue_poll_delay_store(struct request_queue *q, const char *page,
         if (err < 0)
                 return err;
 
-        if (val == -1)
-                q->poll_nsec = -1;
-        else
+        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;
 
         return count;
 }
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 0de92b29f589..5c58a3b2bf00 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.