scsi: convert host_busy to atomic_t

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>

1 files changed, 2 insertions, 2 deletions

diff --git a/drivers/scsi/libiscsi.c b/drivers/scsi/libiscsi.c
index f2db82beb646..f9f3a1224dfa 100644
--- a/drivers/scsi/libiscsi.c
+++ b/drivers/scsi/libiscsi.c
@@ -2971,7 +2971,7 @@ void iscsi_conn_teardown(struct iscsi_cls_conn *cls_conn)
          */
         for (;;) {
                 spin_lock_irqsave(session->host->host_lock, flags);
-                if (!session->host->host_busy) { /* OK for ERL == 0 */
+                if (!atomic_read(&session->host->host_busy)) { /* OK for ERL == 0 */
                         spin_unlock_irqrestore(session->host->host_lock, flags);
                         break;
                 }
@@ -2979,7 +2979,7 @@ void iscsi_conn_teardown(struct iscsi_cls_conn *cls_conn)
                 msleep_interruptible(500);
                 iscsi_conn_printk(KERN_INFO, conn, "iscsi conn_destroy(): "
                                   "host_busy %d host_failed %d\n",
-                                  session->host->host_busy,
+                                  atomic_read(&session->host->host_busy),
                                   session->host->host_failed);
                 /*
                  * force eh_abort() to unblock