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=-16.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 35173C4320A for ; Wed, 11 Aug 2021 15:52:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0D0AA61019 for ; Wed, 11 Aug 2021 15:52:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233338AbhHKPxN (ORCPT ); Wed, 11 Aug 2021 11:53:13 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:21573 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233276AbhHKPxL (ORCPT ); Wed, 11 Aug 2021 11:53:11 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1628697147; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=DUxtRhCT6Yy2CRsBgNph4jPMuk409yTWI7Iuc9nD2EI=; b=cQKejN2MiwDbSIZFqS+No2UB89z7CdEAZfwI7k3rzrb/m2J4oNh1bsG91ZLEqkoPmG/Aj8 CDEY07Ldi/BE3CAi+lot2z/TOQo+zty5ieRYETdZ8fEInLUBEE690W4W1kv53wIE7hOIh2 c1BuLI11V0Np0XqAWc1yRM5cUE9UiFY= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-390-YziSKtdzPuuTP3vZTmEs9A-1; Wed, 11 Aug 2021 11:52:24 -0400 X-MC-Unique: YziSKtdzPuuTP3vZTmEs9A-1 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 mimecast-mx01.redhat.com (Postfix) with ESMTPS id 024FD1853028; Wed, 11 Aug 2021 15:52:23 +0000 (UTC) Received: from localhost (ovpn-12-52.pek2.redhat.com [10.72.12.52]) by smtp.corp.redhat.com (Postfix) with ESMTP id 574A65C1B4; Wed, 11 Aug 2021 15:52:16 +0000 (UTC) From: Ming Lei To: Jens Axboe Cc: linux-block@vger.kernel.org, Christoph Hellwig , Bart Van Assche , John Garry , Ming Lei , Keith Busch Subject: [PATCH V2] blk-mq: don't grab rq's refcount in blk_mq_check_expired() Date: Wed, 11 Aug 2021 23:52:02 +0800 Message-Id: <20210811155202.629575-1-ming.lei@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Inside blk_mq_queue_tag_busy_iter() we already grabbed request's refcount before calling ->fn(), so needn't to grab it one more time in blk_mq_check_expired(). Meantime remove extra request expire check in blk_mq_check_expired(). Cc: Keith Busch Signed-off-by: Ming Lei --- V2: - remove extra request expire check as suggested by Keith - modify comment a bit block/blk-mq.c | 30 +++++------------------------- 1 file changed, 5 insertions(+), 25 deletions(-) diff --git a/block/blk-mq.c b/block/blk-mq.c index d2725f94491d..b5237211ccb7 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -923,34 +923,14 @@ static bool blk_mq_check_expired(struct blk_mq_hw_ctx *hctx, unsigned long *next = priv; /* - * Just do a quick check if it is expired before locking the request in - * so we're not unnecessarilly synchronizing across CPUs. - */ - if (!blk_mq_req_expired(rq, next)) - return true; - - /* - * We have reason to believe the request may be expired. Take a - * reference on the request to lock this request lifetime into its - * currently allocated context to prevent it from being reallocated in - * the event the completion by-passes this timeout handler. - * - * If the reference was already released, then the driver beat the - * timeout handler to posting a natural completion. - */ - if (!refcount_inc_not_zero(&rq->ref)) - return true; - - /* - * The request is now locked and cannot be reallocated underneath the - * timeout handler's processing. Re-verify this exact request is truly - * expired; if it is not expired, then the request was completed and - * reallocated as a new request. + * blk_mq_queue_tag_busy_iter() has locked the request, so it cannot + * be reallocated underneath the timeout handler's processing, then + * the expire check is reliable. If the request is not expired, then + * it was completed and reallocated as a new request after returning + * from blk_mq_check_expired(). */ if (blk_mq_req_expired(rq, next)) blk_mq_rq_timed_out(rq, reserved); - - blk_mq_put_rq_ref(rq); return true; } -- 2.31.1