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Tue, 02 Jun 2020 08:04:21 +0000 Received: from pps.filterd (aserp3020.oracle.com [127.0.0.1]) by aserp3020.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 0527vsDH126055; Tue, 2 Jun 2020 08:02:20 GMT Received: from aserv0122.oracle.com (aserv0122.oracle.com [141.146.126.236]) by aserp3020.oracle.com with ESMTP id 31c25n51rj-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 02 Jun 2020 08:02:20 +0000 Received: from abhmp0009.oracle.com (abhmp0009.oracle.com [141.146.116.15]) by aserv0122.oracle.com (8.14.4/8.14.4) with ESMTP id 05282Jir015345; Tue, 2 Jun 2020 08:02:19 GMT Received: from [192.168.0.110] (/183.246.144.78) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Tue, 02 Jun 2020 01:02:19 -0700 Subject: Re: [PATCH 1/1] blk-mq: get ctx in order to handle BLK_MQ_S_INACTIVE in blk_mq_get_tag() To: Dongli Zhang , linux-block@vger.kernel.org Cc: axboe@kernel.dk, hare@suse.de, dwagner@suse.de, ming.lei@redhat.com, linux-kernel@vger.kernel.org References: <20200602061749.32029-1-dongli.zhang@oracle.com> From: Bob Liu Message-ID: Date: Tue, 2 Jun 2020 16:01:43 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: <20200602061749.32029-1-dongli.zhang@oracle.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9639 signatures=668686 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 adultscore=0 suspectscore=0 spamscore=0 malwarescore=0 bulkscore=0 mlxscore=0 phishscore=0 mlxlogscore=999 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2006020051 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9639 signatures=668686 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 cotscore=-2147483648 adultscore=0 priorityscore=1501 phishscore=0 mlxlogscore=999 suspectscore=0 spamscore=0 clxscore=1011 lowpriorityscore=0 mlxscore=0 bulkscore=0 malwarescore=0 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2006020051 Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 6/2/20 2:17 PM, Dongli Zhang wrote: > When scheduler is set, we hit below page fault when we offline cpu. > > [ 1061.007725] BUG: kernel NULL pointer dereference, address: 0000000000000040 > [ 1061.008710] #PF: supervisor read access in kernel mode > [ 1061.009492] #PF: error_code(0x0000) - not-present page > [ 1061.010241] PGD 0 P4D 0 > [ 1061.010614] Oops: 0000 [#1] SMP PTI > [ 1061.011130] CPU: 0 PID: 122 Comm: kworker/0:1H Not tainted 5.7.0-rc7+ #2' > ... ... > [ 1061.013760] Workqueue: kblockd blk_mq_run_work_fn > [ 1061.014446] RIP: 0010:blk_mq_put_tag+0xf/0x30 > ... ... > [ 1061.017726] RSP: 0018:ffffa5c18037fc70 EFLAGS: 00010287 > [ 1061.018475] RAX: 0000000000000000 RBX: ffffa5c18037fcf0 RCX: 0000000000000004 > [ 1061.019507] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff911535dc1180 > ... ... > [ 1061.028454] Call Trace: > [ 1061.029307] blk_mq_get_tag+0x26e/0x280 > [ 1061.029866] ? wait_woken+0x80/0x80 > [ 1061.030378] blk_mq_get_driver_tag+0x99/0x110 > [ 1061.031009] blk_mq_dispatch_rq_list+0x107/0x5e0 > [ 1061.031672] ? elv_rb_del+0x1a/0x30 > [ 1061.032178] blk_mq_do_dispatch_sched+0xe2/0x130 > [ 1061.032844] __blk_mq_sched_dispatch_requests+0xcc/0x150 > [ 1061.033638] blk_mq_sched_dispatch_requests+0x2b/0x50 > [ 1061.034239] __blk_mq_run_hw_queue+0x75/0x110 > [ 1061.034867] process_one_work+0x15c/0x370 > [ 1061.035450] worker_thread+0x44/0x3d0 > [ 1061.035980] kthread+0xf3/0x130 > [ 1061.036440] ? max_active_store+0x80/0x80 > [ 1061.037018] ? kthread_bind+0x10/0x10 > [ 1061.037554] ret_from_fork+0x35/0x40 > [ 1061.038073] Modules linked in: > [ 1061.038543] CR2: 0000000000000040 > [ 1061.038962] ---[ end trace d20e1df7d028e69f ]--- > > This is because blk_mq_get_driver_tag() would be used to allocate tag once > scheduler (e.g., mq-deadline) is set. However, in order to handle > BLK_MQ_S_INACTIVE in blk_mq_get_tag(), we need to set data->ctx for > blk_mq_put_tag(). > > Fixes: bf0beec0607db3c6 ("blk-mq: drain I/O when all CPUs in a hctx are offline") > Signed-off-by: Dongli Zhang > --- > This is based on for-next because currently the pull request for v5.8 is > not picked by mainline. > > block/blk-mq.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/block/blk-mq.c b/block/blk-mq.c > index 9a36ac1c1fa1..8bf6c06a86c1 100644 > --- a/block/blk-mq.c > +++ b/block/blk-mq.c > @@ -1056,6 +1056,7 @@ bool blk_mq_get_driver_tag(struct request *rq) > { > struct blk_mq_alloc_data data = { > .q = rq->q, > + .ctx = rq->mq_ctx, > .hctx = rq->mq_hctx, > .flags = BLK_MQ_REQ_NOWAIT, > .cmd_flags = rq->cmd_flags, > Nice catch! Reviewed-by: Bob Liu