From patchwork Thu Jan 11 02:12:55 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mike Snitzer X-Patchwork-Id: 10156607 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 57CBD605BA for ; Thu, 11 Jan 2018 02:13:12 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 453B92874B for ; Thu, 11 Jan 2018 02:13:12 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 3A39E2874E; Thu, 11 Jan 2018 02:13:12 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id CA2D92874B for ; Thu, 11 Jan 2018 02:13:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754376AbeAKCNK (ORCPT ); Wed, 10 Jan 2018 21:13:10 -0500 Received: from mx1.redhat.com ([209.132.183.28]:60016 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753637AbeAKCNH (ORCPT ); Wed, 10 Jan 2018 21:13:07 -0500 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id B25E78763C; Thu, 11 Jan 2018 02:13:06 +0000 (UTC) Received: from localhost (ovpn-112-6.rdu2.redhat.com [10.10.112.6]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 1E9AD8D66D; Thu, 11 Jan 2018 02:13:05 +0000 (UTC) From: Mike Snitzer To: axboe@kernel.dk Cc: Ming Lei , hch@lst.de, Bart.VanAssche@wdc.com, dm-devel@redhat.com, linux-block@vger.kernel.org Subject: [for-4.16 PATCH v3 2/3] block: allow gendisk's request_queue registration to be deferred Date: Wed, 10 Jan 2018 21:12:55 -0500 Message-Id: <20180111021256.37490-3-snitzer@redhat.com> In-Reply-To: <20180111021256.37490-1-snitzer@redhat.com> References: <20180111021256.37490-1-snitzer@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.26]); Thu, 11 Jan 2018 02:13:06 +0000 (UTC) Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Since I can remember DM has forced the block layer to allow the allocation and initialization of the request_queue to be distinct operations. Reason for this is block/genhd.c:add_disk() has requires that the request_queue (and associated bdi) be tied to the gendisk before add_disk() is called -- because add_disk() also deals with exposing the request_queue via blk_register_queue(). DM's dynamic creation of arbitrary device types (and associated request_queue types) requires the DM device's gendisk be available so that DM table loads can establish a master/slave relationship with subordinate devices that are referenced by loaded DM tables -- using bd_link_disk_holder(). But until these DM tables, and their associated subordinate devices, are known DM cannot know what type of request_queue it needs -- nor what its queue_limits should be. This chicken and egg scenario has created all manner of problems for DM and, at times, the block layer. Summary of changes: - Add QUEUE_FLAG_DEFER_REG that a block driver can set to defer the required blk_register_queue() until the block driver's request_queue is fully initialized. - Return early from blk_unregister_queue() if QUEUE_FLAG_REGISTERED is not set. It won't be set if a request_queue with QUEUE_FLAG_DEFER_REG set never called blk_register_queue() -- as can happen if a driver encounters an error and must del_gendisk() before calling blk_register_queue(). - Export blk_register_queue(). These changes allow DM to use device_add_disk() to anchor its gendisk as the "master" for master/slave relationships DM must establish with subordinate devices referenced in DM tables that get loaded. Once all "slave" devices for a DM device are known a request_queue can be properly initialized and then advertised via sysfs -- important improvement being that no request_queue resource initialization is missed -- before these changes DM was known to be missing blk-mq debugfs and proper block throttle initialization. Signed-off-by: Mike Snitzer --- block/blk-sysfs.c | 4 ++++ block/genhd.c | 4 +++- include/linux/blkdev.h | 1 + 3 files changed, 8 insertions(+), 1 deletion(-) diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c index 870484eaed1f..2395122875b4 100644 --- a/block/blk-sysfs.c +++ b/block/blk-sysfs.c @@ -921,6 +921,7 @@ int blk_register_queue(struct gendisk *disk) mutex_unlock(&q->sysfs_lock); return ret; } +EXPORT_SYMBOL_GPL(blk_register_queue); void blk_unregister_queue(struct gendisk *disk) { @@ -929,6 +930,9 @@ void blk_unregister_queue(struct gendisk *disk) if (WARN_ON(!q)) return; + if (!test_bit(QUEUE_FLAG_REGISTERED, &disk->queue->queue_flags)) + return; + mutex_lock(&q->sysfs_lock); queue_flag_clear_unlocked(QUEUE_FLAG_REGISTERED, q); mutex_unlock(&q->sysfs_lock); diff --git a/block/genhd.c b/block/genhd.c index 00620e01e043..3912a82ecc4f 100644 --- a/block/genhd.c +++ b/block/genhd.c @@ -682,7 +682,6 @@ void device_add_disk(struct device *parent, struct gendisk *disk) exact_match, exact_lock, disk); } register_disk(parent, disk); - blk_register_queue(disk); /* * Take an extra ref on queue which will be put on disk_release() @@ -692,6 +691,9 @@ void device_add_disk(struct device *parent, struct gendisk *disk) disk_add_events(disk); blk_integrity_add(disk); + + if (!test_bit(QUEUE_FLAG_DEFER_REG, &disk->queue->queue_flags)) + blk_register_queue(disk); } EXPORT_SYMBOL(device_add_disk); diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 71a9371c8182..84d144c7b025 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -681,6 +681,7 @@ struct request_queue { #define QUEUE_FLAG_SCSI_PASSTHROUGH 27 /* queue supports SCSI commands */ #define QUEUE_FLAG_QUIESCED 28 /* queue has been quiesced */ #define QUEUE_FLAG_PREEMPT_ONLY 29 /* only process REQ_PREEMPT requests */ +#define QUEUE_FLAG_DEFER_REG 30 /* defer registering queue to a disk */ #define QUEUE_FLAG_DEFAULT ((1 << QUEUE_FLAG_IO_STAT) | \ (1 << QUEUE_FLAG_SAME_COMP) | \