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=-9.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,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 6704CC56201 for ; Thu, 12 Nov 2020 07:55:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0E0DF21D40 for ; Thu, 12 Nov 2020 07:55:58 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Uxt4bYm+" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726204AbgKLHz5 (ORCPT ); Thu, 12 Nov 2020 02:55:57 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:34892 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726202AbgKLHz5 (ORCPT ); Thu, 12 Nov 2020 02:55:57 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1605167756; 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: in-reply-to:in-reply-to:references:references; bh=jsAotUmAOeJ+J67Hd+8VkNC2AHSQC76cxUm+/CDDsK0=; b=Uxt4bYm+me3u7dWsxdZoXkhFS0DBOoZY3CW+QdTkytKcXpy+iygIvsReXVSBSl16Yz1g0G sG0K0gAZG4nesk5PvR0IRLoZnYJuA9JvDj+m9peQFUYKxnY/tYu4fDHE6XwBK2JUXwgqLm QRvfWOl1SSyKON0XQvOGIcF5sTo7Tm0= 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-285-bJRgz6FvMfiLKET8DRTB5g-1; Thu, 12 Nov 2020 02:55:52 -0500 X-MC-Unique: bJRgz6FvMfiLKET8DRTB5g-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id B41EB8015B1; Thu, 12 Nov 2020 07:55:50 +0000 (UTC) Received: from localhost (ovpn-12-132.pek2.redhat.com [10.72.12.132]) by smtp.corp.redhat.com (Postfix) with ESMTP id E64EA55766; Thu, 12 Nov 2020 07:55:43 +0000 (UTC) From: Ming Lei To: Jens Axboe , linux-block@vger.kernel.org, linux-nvme@lists.infradead.org, Christoph Hellwig Cc: Ming Lei , Qian Cai , Sumit Saxena , John Garry , Kashyap Desai , Bart Van Assche , Hannes Reinecke Subject: [PATCH 2/3] nvme-loop: use blk_mq_hctx_set_fq_lock_class to set loop's lock class Date: Thu, 12 Nov 2020 15:55:25 +0800 Message-Id: <20201112075526.947079-3-ming.lei@redhat.com> In-Reply-To: <20201112075526.947079-1-ming.lei@redhat.com> References: <20201112075526.947079-1-ming.lei@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Set nvme-loop's lock class via blk_mq_hctx_set_fq_lock_class for avoiding lockdep possible recursive locking, then we can remove the dynamically allocated lock class for each flush queue, finally we can avoid horrible SCSI probe delay. This way may not address situation in which one nvme-loop is backed on another nvme-loop. However, in reality, people seldom uses this way for test. Even though someone played in this way, it is just one recursive locking false positive, no real deadlock issue. Reported-by: Qian Cai Cc: Sumit Saxena Cc: John Garry Cc: Kashyap Desai Cc: Bart Van Assche Cc: Hannes Reinecke Signed-off-by: Ming Lei --- drivers/nvme/target/loop.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/drivers/nvme/target/loop.c b/drivers/nvme/target/loop.c index f6d81239be21..07806016c09d 100644 --- a/drivers/nvme/target/loop.c +++ b/drivers/nvme/target/loop.c @@ -211,6 +211,8 @@ static int nvme_loop_init_request(struct blk_mq_tag_set *set, (set == &ctrl->tag_set) ? hctx_idx + 1 : 0); } +static struct lock_class_key loop_hctx_fq_lock_key; + static int nvme_loop_init_hctx(struct blk_mq_hw_ctx *hctx, void *data, unsigned int hctx_idx) { @@ -219,6 +221,14 @@ static int nvme_loop_init_hctx(struct blk_mq_hw_ctx *hctx, void *data, BUG_ON(hctx_idx >= ctrl->ctrl.queue_count); + /* + * flush_end_io() can be called recursively for us, so use our own + * lock class key for avoiding lockdep possible recursive locking, + * then we can remove the dynamically allocated lock class for each + * flush queue, that way may cause horrible boot delay. + */ + blk_mq_hctx_set_fq_lock_class(hctx, &loop_hctx_fq_lock_key); + hctx->driver_data = queue; return 0; } -- 2.25.4