From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bart Van Assche Subject: [PATCH 5/7] Micro-optimize scsi_request_fn() Date: Tue, 20 Aug 2013 14:09:22 +0200 Message-ID: <52135C72.6070304@acm.org> References: <52135B99.2000102@acm.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from gerard.telenet-ops.be ([195.130.132.48]:55146 "EHLO gerard.telenet-ops.be" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750974Ab3HTMJX (ORCPT ); Tue, 20 Aug 2013 08:09:23 -0400 In-Reply-To: <52135B99.2000102@acm.org> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: James Bottomley Cc: Mike Christie , Hannes Reinecke , David Milburn , linux-scsi SCSI devices may only be removed by calling scsi_remove_device(). That function must invoke blk_cleanup_queue() before the final put of sdev->sdev_gendev. Since blk_cleanup_queue() waits for the block queue to drain and then tears it down, scsi_request_fn cannot be active anymore after blk_cleanup_queue() has returned and hence the get_device()/put_device() pair in scsi_request_fn is unnecessary. Signed-off-by: Bart Van Assche Acked-by: Tejun Heo Reviewed-by: Mike Christie Cc: Hannes Reinecke --- drivers/scsi/scsi_lib.c | 14 +++----------- 1 file changed, 3 insertions(+), 11 deletions(-) diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c index 362855d..905ac00 100644 --- a/drivers/scsi/scsi_lib.c +++ b/drivers/scsi/scsi_lib.c @@ -1544,16 +1544,14 @@ static void scsi_softirq_done(struct request *rq) * Lock status: IO request lock assumed to be held when called. */ static void scsi_request_fn(struct request_queue *q) + __releases(q->queue_lock) + __acquires(q->queue_lock) { struct scsi_device *sdev = q->queuedata; struct Scsi_Host *shost; struct scsi_cmnd *cmd; struct request *req; - if(!get_device(&sdev->sdev_gendev)) - /* We must be tearing the block queue down already */ - return; - /* * To start with, we keep looping until the queue is empty, or until * the host is no longer able to accept any more requests. @@ -1642,7 +1640,7 @@ static void scsi_request_fn(struct request_queue *q) goto out_delay; } - goto out; + return; not_ready: spin_unlock_irq(shost->host_lock); @@ -1661,12 +1659,6 @@ static void scsi_request_fn(struct request_queue *q) out_delay: if (sdev->device_busy == 0) blk_delay_queue(q, SCSI_QUEUE_DELAY); -out: - /* must be careful here...if we trigger the ->remove() function - * we cannot be holding the q lock */ - spin_unlock_irq(q->queue_lock); - put_device(&sdev->sdev_gendev); - spin_lock_irq(q->queue_lock); } u64 scsi_calculate_bounce_limit(struct Scsi_Host *shost) -- 1.7.10.4