From d772a65d8a6c45c376a8200a38f7f82fb480af6a Mon Sep 17 00:00:00 2001 From: Ming Lei Date: Mon, 27 Aug 2018 15:24:43 +0800 Subject: [PATCH] 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 , Cc: "Martin K. Petersen" , Cc: James Bottomley , Cc: Christoph Hellwig , Cc: Don Brace Cc: Kashyap Desai Cc: Mike Snitzer Cc: Hannes Reinecke Cc: Laurence Oberman Cc: Bart Van Assche Cc: Jens Axboe Reported-by: Jens Axboe Signed-off-by: Ming Lei Signed-off-by: Martin K. Petersen --- drivers/scsi/hosts.c | 24 +----------------------- drivers/scsi/scsi_lib.c | 23 ++++++----------------- 2 files changed, 7 insertions(+), 40 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); diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c index 1046679f5473..eb97d2dd3651 100644 --- a/drivers/scsi/scsi_lib.c +++ b/drivers/scsi/scsi_lib.c @@ -345,8 +345,7 @@ static void scsi_dec_host_busy(struct Scsi_Host *shost) unsigned long flags; rcu_read_lock(); - if (!shost->use_blk_mq) - atomic_dec(&shost->host_busy); + atomic_dec(&shost->host_busy); if (unlikely(scsi_host_in_recovery(shost))) { spin_lock_irqsave(shost->host_lock, flags); if (shost->host_failed || shost->host_eh_scheduled) @@ -445,12 +444,7 @@ static inline bool scsi_target_is_busy(struct scsi_target *starget) static inline bool scsi_host_is_busy(struct Scsi_Host *shost) { - /* - * blk-mq can handle host queue busy efficiently via host-wide driver - * tag allocation - */ - - if (!shost->use_blk_mq && shost->can_queue > 0 && + if (shost->can_queue > 0 && atomic_read(&shost->host_busy) >= shost->can_queue) return true; if (atomic_read(&shost->host_blocked) > 0) @@ -1606,12 +1600,9 @@ static inline int scsi_host_queue_ready(struct request_queue *q, if (scsi_host_in_recovery(shost)) return 0; - if (!shost->use_blk_mq) - busy = atomic_inc_return(&shost->host_busy) - 1; - else - busy = 0; + busy = atomic_inc_return(&shost->host_busy) - 1; if (atomic_read(&shost->host_blocked) > 0) { - if (busy || scsi_host_busy(shost)) + if (busy) goto starved; /* @@ -1625,7 +1616,7 @@ static inline int scsi_host_queue_ready(struct request_queue *q, "unblocking host at zero depth\n")); } - if (!shost->use_blk_mq && shost->can_queue > 0 && busy >= shost->can_queue) + if (shost->can_queue > 0 && busy >= shost->can_queue) goto starved; if (shost->host_self_blocked) goto starved; @@ -1711,9 +1702,7 @@ static void scsi_kill_request(struct request *req, struct request_queue *q) * with the locks as normal issue path does. */ atomic_inc(&sdev->device_busy); - - if (!shost->use_blk_mq) - atomic_inc(&shost->host_busy); + atomic_inc(&shost->host_busy); if (starget->can_queue > 0) atomic_inc(&starget->target_busy); -- GitLab