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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 43AD9C433EF for ; Tue, 24 May 2022 12:14:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235417AbiEXMOg (ORCPT ); Tue, 24 May 2022 08:14:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50694 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230394AbiEXMOe (ORCPT ); Tue, 24 May 2022 08:14:34 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id AFF496F492 for ; Tue, 24 May 2022 05:14:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1653394472; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=9JI11b85ofkZF9fW3eAAZPAx9w5swJPzDrsDSmuEDHo=; b=OE34eTElvNxk9abGAhgiAmev5mXCZFcpzfyuA4760+CT2O0KqX5mHXIknBvO2LfEPRyGJq tVf0fcabL3gIIbz/zconwjUaqSwo/hMXFhpe1g2sBEmJACEm/GZ+hiWzvvmlrKl+JWvkSn WPocKtrYuUWTBvdd+ilCk2cCudIc4Kk= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-510--HnNk4O4Nce-xzdg-sLThw-1; Tue, 24 May 2022 08:14:29 -0400 X-MC-Unique: -HnNk4O4Nce-xzdg-sLThw-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 2C0D91D32362; Tue, 24 May 2022 12:14:29 +0000 (UTC) Received: from T590 (ovpn-8-20.pek2.redhat.com [10.72.8.20]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 3B27C2166B25; Tue, 24 May 2022 12:14:23 +0000 (UTC) Date: Tue, 24 May 2022 20:14:18 +0800 From: Ming Lei To: Christoph Hellwig Cc: axboe@kernel.dk, shinichiro.kawasaki@wdc.com, dan.j.williams@intel.com, yukuai3@huawei.com, linux-block@vger.kernel.org Subject: Re: [PATCH] block: remove per-disk debugfs files in blk_unregister_queue Message-ID: References: <20220524083325.833981-1-hch@lst.de> <20220524120134.GB17563@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220524120134.GB17563@lst.de> X-Scanned-By: MIMEDefang 2.78 on 10.11.54.6 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Tue, May 24, 2022 at 02:01:34PM +0200, Christoph Hellwig wrote: > On Tue, May 24, 2022 at 07:47:03PM +0800, Ming Lei wrote: > > Not look into details yet, but as one blk-mq debugfs user, I don't like > > the idea, since I often see io hang issue when calling > > blk_mq_freeze_queue_wait(), and blk-mq debugfs is very helpful for > > investigating this kind of issue. > > > > But now blk-mq debugfs is gone with this patch __before__ draining IO in > > del_gendisk, and it becomes not useful as before. > > This is the way hot it is set up, so in doubt I want it to be torn down > synchronously. There might be a way to move the teardown later, but > that will require a very careful audit. Then please move it to disk release at least, when blk-mq debug becomes less useful. In theory, blk_cleanup_queue() may have similar issue, but most of drivers release disk after blk_cleanup_queue() except for scsi disk. So from user viewpoint, the best place to tear down blk-mq debugfs is still in queue release handler. Thanks, Ming