From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0DBFF17799F for ; Mon, 6 Jan 2025 03:32:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736134324; cv=none; b=MGrGlXFNkb4n5DSuVYVmGd5dRleywiweCd3CHBdN96yLAQby+QBi4nHd79KhXy/IyTDT6j4ST0FZO4dUwZexMXRby6Nmc2qydgZVLASSy/1Hod0XcQqUGspOTFNK8pbOAS809FDdUa9Gc6I/ntCDAI3i3ruh7LTdfQhPrV2kDiY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736134324; c=relaxed/simple; bh=9MJ0wURY77/qeXCTxvVjqe9VGB2y46cdneWDkp2vif8=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=CARIjfaP5UaOUlBjNlK0U9I/52YJP+yO05/rDoNHPS6D2JM7p6sNOT5ZZOLNLStrp2PylEBaqUfXyxMzfQ5VUx6fJDst7Xm4yz3t1AOF9OcUNaxQ+eRqkPhAvDVsZgDVZkS7hAutbNGZFedKcEFTwZSPG515iIF186OURYj8+NY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=G9SiMht5; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="G9SiMht5" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1736134319; 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=wP7jolLUYxTGQVKFJKvtxIhzzFzEDzKghI1l/9u+ocU=; b=G9SiMht5ZJKXsVD5OXHoVCpPLxQOe3neS+EzD+i9Vk0glL5KiWcSd2da7KasgGNqihauwG 7O9uzhJcBVa6n/hMSSsqPh1CLZIBd5HULMlIJDPoUtSqKlG4mRbSkadY1Jy20edpVgK0Ga Q62Wt+wDbHsF0ok/PLJBnkzfxNp/Cf0= Received: from mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-671-KcX282JuPk29GhOFRtX-TA-1; Sun, 05 Jan 2025 22:31:57 -0500 X-MC-Unique: KcX282JuPk29GhOFRtX-TA-1 X-Mimecast-MFC-AGG-ID: KcX282JuPk29GhOFRtX-TA Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 002351956053; Mon, 6 Jan 2025 03:31:55 +0000 (UTC) Received: from fedora (unknown [10.72.116.65]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 630951956056; Mon, 6 Jan 2025 03:31:48 +0000 (UTC) Date: Mon, 6 Jan 2025 11:31:43 +0800 From: Ming Lei To: Damien Le Moal Cc: Jens Axboe , linux-block@vger.kernel.org, linux-nvme@lists.infradead.org, Christoph Hellwig , Keith Busch , Sagi Grimberg , Nilay Shroff Subject: Re: [PATCH 1/3] block: Fix sysfs queue freeze and limits lock order Message-ID: References: <20250104132522.247376-1-dlemoal@kernel.org> <20250104132522.247376-2-dlemoal@kernel.org> Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250104132522.247376-2-dlemoal@kernel.org> X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 On Sat, Jan 04, 2025 at 10:25:20PM +0900, Damien Le Moal wrote: > queue_attr_store() always freezes a device queue before calling the > attribute store operation. For attributes that control queue limits, the > store operation will also lock the queue limits with a call to > queue_limits_start_update(). However, some drivers (e.g. SCSI sd) may > need to issue commands to a device to obtain limit values from the > hardware with the queue limits locked. This creates a potential ABBA > deadlock situation if a user attempts to modify a limit (thus freezing > the device queue) while the device driver starts a revalidation of the > device queue limits. > > Avoid such deadlock by introducing the ->store_limit() operation in > struct queue_sysfs_entry and use this operation for all attributes that > modify the device queue limits through the QUEUE_RW_LIMIT_ENTRY() macro > definition. queue_attr_store() is modified to call the ->store_limit() > operation (if it is defined) without the device queue frozen. The device > queue freeze for attributes defining the ->stor_limit() operation is > moved to after the operation completes and is done only around the call > to queue_limits_commit_update(). > > Cc: stable@vger.kernel.org # v6.9+ > Signed-off-by: Damien Le Moal > --- > block/blk-sysfs.c | 123 ++++++++++++++++++++++++---------------------- > 1 file changed, 64 insertions(+), 59 deletions(-) > > diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c > index 767598e719ab..4fc0020c73a5 100644 > --- a/block/blk-sysfs.c > +++ b/block/blk-sysfs.c > @@ -24,6 +24,8 @@ struct queue_sysfs_entry { > struct attribute attr; > ssize_t (*show)(struct gendisk *disk, char *page); > ssize_t (*store)(struct gendisk *disk, const char *page, size_t count); > + ssize_t (*store_limit)(struct gendisk *disk, struct queue_limits *lim, > + const char *page, size_t count); As I mentioned in another thread, freezing queue may not be needed in ->store(), so let's discuss and confirm if it is needed here first. https://lore.kernel.org/linux-block/Z3tHozKiUqWr7gjO@fedora/ Also even though freeze is needed, I'd suggest to move freeze in each .store() callback for simplifying & avoiding regression. Thanks, Ming