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

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This reverts commit 328728630d.

There is fundamental issue in commit 328728630d (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 <[email protected]>,
Cc: "Martin K. Petersen" <[email protected]>,
Cc: James Bottomley <[email protected]>,
Cc: Christoph Hellwig <[email protected]>,
Cc: Don Brace <[email protected]>
Cc: Kashyap Desai <[email protected]>
Cc: Mike Snitzer <[email protected]>
Cc: Hannes Reinecke <[email protected]>
Cc: Laurence Oberman <[email protected]>
Cc: Bart Van Assche <[email protected]>
Cc: Jens Axboe <[email protected]>
Reported-by: Jens Axboe <[email protected]>
Signed-off-by: Ming Lei <[email protected]>
Signed-off-by: Martin K. Petersen <[email protected]>
This commit is contained in:
Ming Lei 2018-08-27 15:24:43 +08:00 • committed by Martin K. Petersen
commit d772a65d8a
2 changed files with 7 additions and 40 deletions
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24
drivers/scsi/hosts.c
View file

@ -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);

23
drivers/scsi/scsi_lib.c
View file

@ -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);