hpsa: count passthru cmds with atomics, not a spin locked int

Performance enhancement. Remove spin_locks from the driver.

Reviewed-by: Scott Teel <scott.teel@pmcs.com>
Signed-off-by: Don Brace <don.brace@pmcs.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

diff --git a/drivers/scsi/hpsa.c b/drivers/scsi/hpsa.c
index 72abcf3bfabf733b2a0ed2ae934671bd03eb053a..bae3759e30e2e30ab741471b1b87bb837ffcd11c 100644 (file)
--- a/drivers/scsi/hpsa.c
+++ b/drivers/scsi/hpsa.c
@@ -5105,35 +5105,6 @@ static void check_ioctl_unit_attention(struct ctlr_info *h,
                (void) check_for_unit_attention(h, c);
 }
 
-static int increment_passthru_count(struct ctlr_info *h)
-{
-       unsigned long flags;
-
-       spin_lock_irqsave(&h->passthru_count_lock, flags);
-       if (h->passthru_count >= HPSA_MAX_CONCURRENT_PASSTHRUS) {
-               spin_unlock_irqrestore(&h->passthru_count_lock, flags);
-               return -1;
-       }
-       h->passthru_count++;
-       spin_unlock_irqrestore(&h->passthru_count_lock, flags);
-       return 0;
-}
-
-static void decrement_passthru_count(struct ctlr_info *h)
-{
-       unsigned long flags;
-
-       spin_lock_irqsave(&h->passthru_count_lock, flags);
-       if (h->passthru_count <= 0) {
-               spin_unlock_irqrestore(&h->passthru_count_lock, flags);
-               /* not expecting to get here. */
-               dev_warn(&h->pdev->dev, "Bug detected, passthru_count seems to be incorrect.\n");
-               return;
-       }
-       h->passthru_count--;
-       spin_unlock_irqrestore(&h->passthru_count_lock, flags);
-}
-
 /*
  * ioctl
  */
@@ -5156,16 +5127,16 @@ static int hpsa_ioctl(struct scsi_device *dev, int cmd, void __user *arg)
        case CCISS_GETDRIVVER:
                return hpsa_getdrivver_ioctl(h, argp);
        case CCISS_PASSTHRU:
-               if (increment_passthru_count(h))
+               if (atomic_dec_if_positive(&h->passthru_cmds_avail) < 0)
                        return -EAGAIN;
                rc = hpsa_passthru_ioctl(h, argp);
-               decrement_passthru_count(h);
+               atomic_inc(&h->passthru_cmds_avail);
                return rc;
        case CCISS_BIG_PASSTHRU:
-               if (increment_passthru_count(h))
+               if (atomic_dec_if_positive(&h->passthru_cmds_avail) < 0)
                        return -EAGAIN;
                rc = hpsa_big_passthru_ioctl(h, argp);
-               decrement_passthru_count(h);
+               atomic_inc(&h->passthru_cmds_avail);
                return rc;
        default:
                return -ENOTTY;
@@ -6852,7 +6823,7 @@ reinit_after_soft_reset:
        spin_lock_init(&h->lock);
        spin_lock_init(&h->offline_device_lock);
        spin_lock_init(&h->scan_lock);
-       spin_lock_init(&h->passthru_count_lock);
+       atomic_set(&h->passthru_cmds_avail, HPSA_MAX_CONCURRENT_PASSTHRUS);
 
        h->resubmit_wq = alloc_workqueue("hpsa", WQ_MEM_RECLAIM, 0);
        if (!h->resubmit_wq) {

diff --git a/drivers/scsi/hpsa.h b/drivers/scsi/hpsa.h
index 981479a1393505d03ceca8c0c93f7d448ce71136..1856445f883a0fee08f346b2977c6d92dc708991 100644 (file)
--- a/drivers/scsi/hpsa.h
+++ b/drivers/scsi/hpsa.h
@@ -183,8 +183,7 @@ struct ctlr_info {
 
        /* cap concurrent passthrus at some reasonable maximum */
 #define HPSA_MAX_CONCURRENT_PASSTHRUS (10)
-       spinlock_t passthru_count_lock; /* protects passthru_count */
-       int passthru_count;
+       atomic_t passthru_cmds_avail;
 
        /*
         * Performant mode completion buffers