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scsi: convert host_busy to atomic_t

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Avoid taking the host-wide host_lock to check the per-host queue limit.
Instead we do an atomic_inc_return early on to grab our slot in the queue,
and if necessary decrement it after finishing all checks.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Webb Scales <webbnh@hp.com>
Acked-by: Jens Axboe <axboe@kernel.dk>
Tested-by: Bart Van Assche <bvanassche@acm.org>
Tested-by: Robert Elliott <elliott@hp.com>
This commit is contained in:
Christoph Hellwig
2014-01-22 15:29:29 +01:00
parent 7ae65c0f96
commit 7466501608
9 changed files with 69 additions and 48 deletions
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10
include/scsi/scsi_host.h
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@@ -582,13 +582,9 @@ struct Scsi_Host {
*/
struct blk_queue_tag *bqt;
/*
* The following two fields are protected with host_lock;
* however, eh routines can safely access during eh processing
* without acquiring the lock.
*/
unsigned int host_busy; /* commands actually active on low-level */
unsigned int host_failed; /* commands that failed. */
atomic_t host_busy; /* commands actually active on low-level */
unsigned int host_failed; /* commands that failed.
protected by host_lock */
unsigned int host_eh_scheduled; /* EH scheduled without command */
unsigned int host_no; /* Used for IOCTL_GET_IDLUN, /proc/scsi et al. */