Revert "scsi: core: avoid host-wide host_busy counter for scsi_mq"

This reverts commit 328728630d9f2bf14b82ca30b5e47489beefe361.

There is fundamental issue in commit 328728630d9f2bf1 (scsi: core: avoid
host-wide host_busy counter for scsi_mq) because SCSI's host busy counter
may not be same with counter of blk-mq's inflight tags, especially in case
of none io scheduler.

We may switch to other approach for addressing this scsi_mq's performance
issue, such as percpu counter or kind of ways, so revert this commit first
for fixing this kind of issue in EH path, as reported by Jens.

Cc: Omar Sandoval <osandov@fb.com>,
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>,
Cc: James Bottomley <james.bottomley@hansenpartnership.com>,
Cc: Christoph Hellwig <hch@lst.de>,
Cc: Don Brace <don.brace@microsemi.com>
Cc: Kashyap Desai <kashyap.desai@broadcom.com>
Cc: Mike Snitzer <snitzer@redhat.com>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Laurence Oberman <loberman@redhat.com>
Cc: Bart Van Assche <bart.vanassche@wdc.com>
Cc: Jens Axboe <axboe@kernel.dk>
Reported-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

1 files changed, 1 insertions, 23 deletions

diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c
index f02dcc875a09..ea4b0bb0c1cd 100644
--- a/drivers/scsi/hosts.c
+++ b/drivers/scsi/hosts.c
@@ -563,35 +563,13 @@ struct Scsi_Host *scsi_host_get(struct Scsi_Host *shost)
 }
 EXPORT_SYMBOL(scsi_host_get);
 
-struct scsi_host_mq_in_flight {
-	int cnt;
-};
-
-static void scsi_host_check_in_flight(struct request *rq, void *data,
-		bool reserved)
-{
-	struct scsi_host_mq_in_flight *in_flight = data;
-
-	if (blk_mq_request_started(rq))
-		in_flight->cnt++;
-}
-
 /**
  * scsi_host_busy - Return the host busy counter
  * @shost:	Pointer to Scsi_Host to inc.
  **/
 int scsi_host_busy(struct Scsi_Host *shost)
 {
-	struct scsi_host_mq_in_flight in_flight = {
-		.cnt = 0,
-	};
-
-	if (!shost->use_blk_mq)
-		return atomic_read(&shost->host_busy);
-
-	blk_mq_tagset_busy_iter(&shost->tag_set, scsi_host_check_in_flight,
-			&in_flight);
-	return in_flight.cnt;
+	return atomic_read(&shost->host_busy);
 }
 EXPORT_SYMBOL(scsi_host_busy);