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 626D4FA3740 for ; Fri, 28 Oct 2022 12:05:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230022AbiJ1ME7 (ORCPT ); Fri, 28 Oct 2022 08:04:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45396 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229959AbiJ1ME4 (ORCPT ); Fri, 28 Oct 2022 08:04:56 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9B6102AC74 for ; Fri, 28 Oct 2022 05:04:51 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 1BBB662806 for ; Fri, 28 Oct 2022 12:04:51 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2C6C1C433C1; Fri, 28 Oct 2022 12:04:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1666958690; bh=HqRxgCAcwRo7Vj35j42nf+TqkpGbX3Siy8B/pS+HHHI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ZslSUm8uBld9RcpzjyGZ3MF2eMUYaMhyc4l/dwUyPmjSH5w4oQxI+789lmkHK+jbZ VUkB8xpQs8z/VwnlgcUp2dQx1sDFnEQlwUPVMtFLw8Tra3dK7rREDZg44Yof+R0mpQ birxhI4GSNWM4bXmq0GUhyk79VRi99ZUS8Do2YlE= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Yu Kuai , Jens Axboe Subject: [PATCH 5.10 16/73] blk-wbt: call rq_qos_add() after wb_normal is initialized Date: Fri, 28 Oct 2022 14:03:13 +0200 Message-Id: <20221028120233.068971425@linuxfoundation.org> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221028120232.344548477@linuxfoundation.org> References: <20221028120232.344548477@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Yu Kuai commit 8c5035dfbb9475b67c82b3fdb7351236525bf52b upstream. Our test found a problem that wbt inflight counter is negative, which will cause io hang(noted that this problem doesn't exist in mainline): t1: device create t2: issue io add_disk blk_register_queue wbt_enable_default wbt_init rq_qos_add // wb_normal is still 0 /* * in mainline, disk can't be opened before * bdev_add(), however, in old kernels, disk * can be opened before blk_register_queue(). */ blkdev_issue_flush // disk size is 0, however, it's not checked submit_bio_wait submit_bio blk_mq_submit_bio rq_qos_throttle wbt_wait bio_to_wbt_flags rwb_enabled // wb_normal is 0, inflight is not increased wbt_queue_depth_changed(&rwb->rqos); wbt_update_limits // wb_normal is initialized rq_qos_track wbt_track rq->wbt_flags |= bio_to_wbt_flags(rwb, bio); // wb_normal is not 0，wbt_flags will be set t3: io completion blk_mq_free_request rq_qos_done wbt_done wbt_is_tracked // return true __wbt_done wbt_rqw_done atomic_dec_return(&rqw->inflight); // inflight is decreased commit 8235b5c1e8c1 ("block: call bdev_add later in device_add_disk") can avoid this problem, however it's better to fix this problem in wbt: 1) Lower kernel can't backport this patch due to lots of refactor. 2) Root cause is that wbt call rq_qos_add() before wb_normal is initialized. Fixes: e34cbd307477 ("blk-wbt: add general throttling mechanism") Cc: Signed-off-by: Yu Kuai Link: https://lore.kernel.org/r/20220913105749.3086243-1-yukuai1@huaweicloud.com Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman --- block/blk-wbt.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) --- a/block/blk-wbt.c +++ b/block/blk-wbt.c @@ -840,6 +840,10 @@ int wbt_init(struct request_queue *q) rwb->enable_state = WBT_STATE_ON_DEFAULT; rwb->wc = 1; rwb->rq_depth.default_depth = RWB_DEF_DEPTH; + rwb->min_lat_nsec = wbt_default_latency_nsec(q); + + wbt_queue_depth_changed(&rwb->rqos); + wbt_set_write_cache(q, test_bit(QUEUE_FLAG_WC, &q->queue_flags)); /* * Assign rwb and add the stats callback. @@ -847,10 +851,5 @@ int wbt_init(struct request_queue *q) rq_qos_add(q, &rwb->rqos); blk_stat_add_callback(q, rwb->cb); - rwb->min_lat_nsec = wbt_default_latency_nsec(q); - - wbt_queue_depth_changed(&rwb->rqos); - wbt_set_write_cache(q, test_bit(QUEUE_FLAG_WC, &q->queue_flags)); - return 0; }