From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933652AbaFLNsV (ORCPT ); Thu, 12 Jun 2014 09:48:21 -0400 Received: from casper.infradead.org ([85.118.1.10]:59464 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933288AbaFLNrJ (ORCPT ); Thu, 12 Jun 2014 09:47:09 -0400 From: Christoph Hellwig To: James Bottomley Cc: Jens Axboe , Bart Van Assche , Robert Elliot , linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH 10/14] scsi: only maintain target_blocked if the driver has a target queue limit Date: Thu, 12 Jun 2014 15:49:02 +0200 Message-Id: <1402580946-11470-11-git-send-email-hch@lst.de> X-Mailer: git-send-email 1.7.10.4 In-Reply-To: <1402580946-11470-1-git-send-email-hch@lst.de> References: <1402580946-11470-1-git-send-email-hch@lst.de> X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This saves us an atomic operation for each I/O submission and completion for the usual case where the driver doesn't set a per-target can_queue value. Only a few iscsi hardware offload drivers set the per-target can_queue value at the moment. Signed-off-by: Christoph Hellwig --- drivers/scsi/scsi_lib.c | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-) diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c index 0e33dee..763b3c9 100644 --- a/drivers/scsi/scsi_lib.c +++ b/drivers/scsi/scsi_lib.c @@ -295,7 +295,8 @@ void scsi_device_unbusy(struct scsi_device *sdev) unsigned long flags; atomic_dec(&shost->host_busy); - atomic_dec(&starget->target_busy); + if (starget->can_queue > 0) + atomic_dec(&starget->target_busy); if (unlikely(scsi_host_in_recovery(shost) && (shost->host_failed || shost->host_eh_scheduled))) { @@ -1335,6 +1336,9 @@ static inline int scsi_target_queue_ready(struct Scsi_Host *shost, spin_unlock_irq(shost->host_lock); } + if (starget->can_queue <= 0) + return 1; + busy = atomic_inc_return(&starget->target_busy) - 1; if (busy == 0 && atomic_read(&starget->target_blocked) > 0) { if (atomic_dec_return(&starget->target_blocked) > 0) @@ -1344,7 +1348,7 @@ static inline int scsi_target_queue_ready(struct Scsi_Host *shost, "unblocking target at zero depth\n")); } - if (starget->can_queue > 0 && busy >= starget->can_queue) + if (busy >= starget->can_queue) goto starved; if (atomic_read(&starget->target_blocked) > 0) goto starved; @@ -1356,7 +1360,8 @@ starved: list_move_tail(&sdev->starved_entry, &shost->starved_list); spin_unlock_irq(shost->host_lock); out_dec: - atomic_dec(&starget->target_busy); + if (starget->can_queue > 0) + atomic_dec(&starget->target_busy); return 0; } @@ -1473,7 +1478,8 @@ static void scsi_kill_request(struct request *req, struct request_queue *q) */ atomic_inc(&sdev->device_busy); atomic_inc(&shost->host_busy); - atomic_inc(&starget->target_busy); + if (starget->can_queue > 0) + atomic_inc(&starget->target_busy); blk_complete_request(req); } @@ -1642,7 +1648,8 @@ static void scsi_request_fn(struct request_queue *q) return; host_not_ready: - atomic_dec(&scsi_target(sdev)->target_busy); + if (&scsi_target(sdev)->can_queue > 0) + atomic_dec(&scsi_target(sdev)->target_busy); not_ready: /* * lock q, handle tag, requeue req, and decrement device_busy. We -- 1.7.10.4