From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id AB506C10F14 for ; Fri, 12 Apr 2019 03:31:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 816A920675 for ; Fri, 12 Apr 2019 03:31:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726877AbfDLDb0 (ORCPT ); Thu, 11 Apr 2019 23:31:26 -0400 Received: from mx1.redhat.com ([209.132.183.28]:38260 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726731AbfDLDbZ (ORCPT ); Thu, 11 Apr 2019 23:31:25 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 8136387627; Fri, 12 Apr 2019 03:31:25 +0000 (UTC) Received: from localhost (ovpn-8-26.pek2.redhat.com [10.72.8.26]) by smtp.corp.redhat.com (Postfix) with ESMTP id A6D4C5C21E; Fri, 12 Apr 2019 03:31:24 +0000 (UTC) From: Ming Lei To: Jens Axboe Cc: linux-block@vger.kernel.org, Ming Lei , Dongli Zhang , James Smart , Bart Van Assche , linux-scsi@vger.kernel.org, "Martin K . Petersen" , Christoph Hellwig , "James E . J . Bottomley" , jianchao wang Subject: [PATCH V5 9/9] SCSI: don't hold device refcount in IO path Date: Fri, 12 Apr 2019 11:30:32 +0800 Message-Id: <20190412033032.10418-10-ming.lei@redhat.com> In-Reply-To: <20190412033032.10418-1-ming.lei@redhat.com> References: <20190412033032.10418-1-ming.lei@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.26]); Fri, 12 Apr 2019 03:31:25 +0000 (UTC) Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org scsi_device's refcount is always grabbed in IO path. Turns out it isn't necessary, because blk_queue_cleanup() will drain any in-flight IOs, then cancel timeout/requeue work, and SCSI's requeue_work is canceled too in __scsi_remove_device(). Also scsi_device won't go away until blk_cleanup_queue() is done. So don't hold the refcount in IO path, especially the refcount isn't required in IO path since blk_queue_enter() / blk_queue_exit() is introduced in the legacy block layer. Cc: Dongli Zhang Cc: James Smart Cc: Bart Van Assche Cc: linux-scsi@vger.kernel.org, Cc: Martin K . Petersen , Cc: Christoph Hellwig , Cc: James E . J . Bottomley , Cc: jianchao wang Reviewed-by: Bart Van Assche Signed-off-by: Ming Lei --- drivers/scsi/scsi_lib.c | 28 ++-------------------------- 1 file changed, 2 insertions(+), 26 deletions(-) diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c index 601b9f1de267..3369d66911eb 100644 --- a/drivers/scsi/scsi_lib.c +++ b/drivers/scsi/scsi_lib.c @@ -141,8 +141,6 @@ scsi_set_blocked(struct scsi_cmnd *cmd, int reason) static void scsi_mq_requeue_cmd(struct scsi_cmnd *cmd) { - struct scsi_device *sdev = cmd->device; - if (cmd->request->rq_flags & RQF_DONTPREP) { cmd->request->rq_flags &= ~RQF_DONTPREP; scsi_mq_uninit_cmd(cmd); @@ -150,7 +148,6 @@ static void scsi_mq_requeue_cmd(struct scsi_cmnd *cmd) WARN_ON_ONCE(true); } blk_mq_requeue_request(cmd->request, true); - put_device(&sdev->sdev_gendev); } /** @@ -189,19 +186,7 @@ static void __scsi_queue_insert(struct scsi_cmnd *cmd, int reason, bool unbusy) */ cmd->result = 0; - /* - * Before a SCSI command is dispatched, - * get_device(&sdev->sdev_gendev) is called and the host, - * target and device busy counters are increased. Since - * requeuing a request causes these actions to be repeated and - * since scsi_device_unbusy() has already been called, - * put_device(&device->sdev_gendev) must still be called. Call - * put_device() after blk_mq_requeue_request() to avoid that - * removal of the SCSI device can start before requeueing has - * happened. - */ blk_mq_requeue_request(cmd->request, true); - put_device(&device->sdev_gendev); } /* @@ -619,7 +604,6 @@ static bool scsi_end_request(struct request *req, blk_status_t error, blk_mq_run_hw_queues(q, true); percpu_ref_put(&q->q_usage_counter); - put_device(&sdev->sdev_gendev); return false; } @@ -1613,7 +1597,6 @@ static void scsi_mq_put_budget(struct blk_mq_hw_ctx *hctx) struct scsi_device *sdev = q->queuedata; atomic_dec(&sdev->device_busy); - put_device(&sdev->sdev_gendev); } static bool scsi_mq_get_budget(struct blk_mq_hw_ctx *hctx) @@ -1621,16 +1604,9 @@ static bool scsi_mq_get_budget(struct blk_mq_hw_ctx *hctx) struct request_queue *q = hctx->queue; struct scsi_device *sdev = q->queuedata; - if (!get_device(&sdev->sdev_gendev)) - goto out; - if (!scsi_dev_queue_ready(q, sdev)) - goto out_put_device; - - return true; + if (scsi_dev_queue_ready(q, sdev)) + return true; -out_put_device: - put_device(&sdev->sdev_gendev); -out: if (atomic_read(&sdev->device_busy) == 0 && !scsi_device_blocked(sdev)) blk_mq_delay_run_hw_queue(hctx, SCSI_QUEUE_DELAY); return false; -- 2.9.5