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Thu, 10 Apr 2025 18:57:18 +0000 (GMT) Message-ID: Date: Fri, 11 Apr 2025 00:27:17 +0530 Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 12/15] block: move debugfs/sysfs register out of freezing queue To: Ming Lei , Jens Axboe , linux-block@vger.kernel.org Cc: Shinichiro Kawasaki , =?UTF-8?Q?Thomas_Hellstr=C3=B6m?= , Christoph Hellwig References: <20250410133029.2487054-1-ming.lei@redhat.com> <20250410133029.2487054-13-ming.lei@redhat.com> Content-Language: en-US From: Nilay Shroff In-Reply-To: <20250410133029.2487054-13-ming.lei@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: hQnU3JbmpRlEAp14Lqg96EjSrzLH5dY6 X-Proofpoint-GUID: hQnU3JbmpRlEAp14Lqg96EjSrzLH5dY6 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1095,Hydra:6.0.680,FMLib:17.12.68.34 definitions=2025-04-10_05,2025-04-10_01,2024-11-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 lowpriorityscore=0 clxscore=1015 malwarescore=0 spamscore=0 bulkscore=0 impostorscore=0 priorityscore=1501 suspectscore=0 mlxlogscore=999 phishscore=0 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2502280000 definitions=main-2504100137 On 4/10/25 7:00 PM, Ming Lei wrote: > Move debugfs/sysfs register out of freezing queue in > __blk_mq_update_nr_hw_queues(), so that the following lockdep dependency > can be killed: > > #2 (&q->q_usage_counter(io)#16){++++}-{0:0}: > #1 (fs_reclaim){+.+.}-{0:0}: > #0 (&sb->s_type->i_mutex_key#3){+.+.}-{4:4}: //debugfs > > And registering/un-registering debugfs/sysfs does not require queue to be > frozen. > > Signed-off-by: Ming Lei > --- > block/blk-mq.c | 20 ++++++++++---------- > 1 file changed, 10 insertions(+), 10 deletions(-) > > diff --git a/block/blk-mq.c b/block/blk-mq.c > index 7219b01764da..0fb72a698d77 100644 > --- a/block/blk-mq.c > +++ b/block/blk-mq.c > @@ -4947,15 +4947,15 @@ static void __blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, > if (set->nr_maps == 1 && nr_hw_queues == set->nr_hw_queues) > return; > > - memflags = memalloc_noio_save(); > - list_for_each_entry(q, &set->tag_list, tag_set_list) > - blk_mq_freeze_queue_nomemsave(q); > - > list_for_each_entry(q, &set->tag_list, tag_set_list) { > blk_mq_debugfs_unregister_hctxs(q); > blk_mq_sysfs_unregister_hctxs(q); > } As we removed hctx sysfs protection while un-registering it, this might cause crash or other side-effect if simultaneously these sysfs attributes are accessed. The read access of these attributes are still protected using ->elevator_lock. Thanks, --Nilay