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block: make queue flags non-atomic

Browse source 
We can save some atomic ops in the IO path, if we clearly define
the rules of how to modify the queue flags.

Signed-off-by: Jens Axboe <[email protected]>
This commit is contained in:
Nick Piggin 2008-04-29 14:48:33 +02:00 • committed by Jens Axboe
commit 75ad23bc0f
13 changed files with 102 additions and 49 deletions
Download patch file Download diff file Expand all files Collapse all files

2
drivers/scsi/scsi_debug.c
View file

@ -1773,7 +1773,7 @@ static int scsi_debug_slave_alloc(struct scsi_device *sdp)
if (SCSI_DEBUG_OPT_NOISE & scsi_debug_opts)
printk(KERN_INFO "scsi_debug: slave_alloc <%u %u %u %u>\n",
sdp->host->host_no, sdp->channel, sdp->id, sdp->lun);
set_bit(QUEUE_FLAG_BIDI, &sdp->request_queue->queue_flags);
queue_flag_set_unlocked(QUEUE_FLAG_BIDI, sdp->request_queue);
return 0;
}

29
drivers/scsi/scsi_lib.c
View file

@ -536,6 +536,9 @@ static void scsi_run_queue(struct request_queue *q)
!shost->host_blocked && !shost->host_self_blocked &&
!((shost->can_queue > 0) &&
(shost->host_busy >= shost->can_queue))) {
int flagset;
/*
* As long as shost is accepting commands and we have
* starved queues, call blk_run_queue. scsi_request_fn
@ -549,19 +552,20 @@ static void scsi_run_queue(struct request_queue *q)
sdev = list_entry(shost->starved_list.next,
struct scsi_device, starved_entry);
list_del_init(&sdev->starved_entry);
spin_unlock_irqrestore(shost->host_lock, flags);
spin_unlock(shost->host_lock);
spin_lock(sdev->request_queue->queue_lock);
flagset = test_bit(QUEUE_FLAG_REENTER, &q->queue_flags) &&
!test_bit(QUEUE_FLAG_REENTER,
&sdev->request_queue->queue_flags);
if (flagset)
queue_flag_set(QUEUE_FLAG_REENTER, sdev->request_queue);
__blk_run_queue(sdev->request_queue);
if (flagset)
queue_flag_clear(QUEUE_FLAG_REENTER, sdev->request_queue);
spin_unlock(sdev->request_queue->queue_lock);
if (test_bit(QUEUE_FLAG_REENTER, &q->queue_flags) &&
!test_and_set_bit(QUEUE_FLAG_REENTER,
&sdev->request_queue->queue_flags)) {
blk_run_queue(sdev->request_queue);
clear_bit(QUEUE_FLAG_REENTER,
&sdev->request_queue->queue_flags);
} else
blk_run_queue(sdev->request_queue);
spin_lock_irqsave(shost->host_lock, flags);
spin_lock(shost->host_lock);
if (unlikely(!list_empty(&sdev->starved_entry)))
/*
* sdev lost a race, and was put back on the
@ -1585,8 +1589,9 @@ struct request_queue *__scsi_alloc_queue(struct Scsi_Host *shost,
blk_queue_max_segment_size(q, dma_get_max_seg_size(dev));
/* New queue, no concurrency on queue_flags */
if (!shost->use_clustering)
clear_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);
queue_flag_clear_unlocked(QUEUE_FLAG_CLUSTER, q);
/*
* set a reasonable default alignment on word boundaries: the

3
drivers/scsi/scsi_transport_sas.c
View file

@ -248,8 +248,7 @@ static int sas_bsg_initialize(struct Scsi_Host *shost, struct sas_rphy *rphy)
else
q->queuedata = shost;
set_bit(QUEUE_FLAG_BIDI, &q->queue_flags);
queue_flag_set_unlocked(QUEUE_FLAG_BIDI, q);
return 0;
}