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Wed, 4 Nov 2026 13:26:09 +0000 (GMT) Received: from [9.123.7.57] (unknown [9.123.7.57]) by smtpav01.dal12v.mail.ibm.com (Postfix) with ESMTP; Wed, 4 Nov 2026 13:26:08 +0000 (GMT) Message-ID: Date: Wed, 4 Nov 2026 18:56:07 +0530 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] blk-mq: take quiesce_lock when removing a queue from the tag set To: Christoph Hellwig , mt4022@columbia.edu Cc: Jens Axboe , Mohamed Khalfella , Keith Busch , Ming Lei , Bart Van Assche , Josef Bacik , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, tz2294@columbia.edu, stable@vger.kernel.org References: <20261103-blk-mq-del-quiesce-lock-v1-1-04aa29a481f6@columbia.edu> <20261104071926.GA29136@lst.de> Content-Language: en-US From: Nilay Shroff In-Reply-To: <20261104071926.GA29136@lst.de> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-GUID: OL6bJ6XdGfIfN-IE_2nKDKeceYmhD930 X-Proofpoint-ORIG-GUID: kjX0ct8-6NHIu3_iWyRCWMcwoDsr-7ZW X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYxMTA0MDA1MiBTYWx0ZWRfXwKFBVFCEePT5 rNCc8CexrDkmhuZK7SJRXcM5SUHKI8IS/QLv/GNZWkGrkpgK6GjzwFLeSu+eGaOiMAz0RDQOAXz lydGC02v0dE+dpONYcrH51O8K/N7zMYszUcWGfnUa3wFJKv7jRt2FpgyTJvnblXrj3mDj6sQHmB 4IMG02DYwsP5v8gXlEf5UpOM4oGqYT5EpAw7PH9qMDN1oZRkSytUlojNbWzQUnftz697NyiTcQN e+Mev6zQ1u87scFqLGKfkNz5NZuJNn9PSEgVlDZc6HGW/tsRypf0H2vgXcxkrciqteRAr+4/DGw M/nSyuTyeqSdMFmDPh2i19ZEboF5vDIOdFb2pAwsf17iTgEg0uszuqyO3N1pzuWUCGDXXe+rTaO 6ckxnRMjo2YWwKGLC88Q9WyyrqvLuT8S5xCzemyFqbyF50bcpmb9kDilTp53vh9c0lqqIDLVJqn GH5uLipbFU/Jhi++T/A== X-Proofpoint-Spam-Info: AW1haW4tMjYxMTA0MDA1MiBTYWx0ZWRfX/ccD5SVabaSY kTLhYnJYNUHqla6dpbi/r8suZKJaxfLjJ1MjA1bUijRJQD7fsPWs/A/81jG8CzSFEx0hgIQwgZq 3awMjGIASlt6K01/6QjjkqNTOrMspfI= X-Authority-Analysis: v=2.4 cv=FIqOVOos c=1 sm=1 tr=0 ts=6aeb3276 cx=c_pps a=GFwsV6G8L6GxiO2Y/PsHdQ==:117 a=GFwsV6G8L6GxiO2Y/PsHdQ==:17 a=IkcTkHD0fZMA:10 a=zJRp6_cAMcgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=uAbxVGIbfxUO_5tXvNgY:22 a=DfyN0UfllRvmPPNdMxQA:9 a=QEXdDO2ut3YA:10 a=zgiPjhLxNE0A:10 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.138,FMLib:17.12.100.49 definitions=2026-11-04_04,2026-11-03_04,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 malwarescore=0 impostorscore=0 spamscore=0 lowpriorityscore=0 bulkscore=0 suspectscore=0 clxscore=1015 priorityscore=1501 phishscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2610300000 definitions=main-2611040052 On 11/4/26 12:49 PM, Christoph Hellwig wrote: > Looks good, but the note from Mohamed should be taken into account. > > Or even better add a guarded_by so that clang catches this (requires > actualy compile testing with clang, though). > Yeah agreed! I also recommend adding __guarded_by() annotation around set->tag_list and set->quiesce_depth. With this change, I have sorted following locking pattern: 1. Every set->tag_list mutation holds both set->tag_list_lock and set->quiesce_lock. 2. Every set->tag_list traversal holds at least one of set->tag_list_lock or set->quiesce_lock. 3. The set->tag_list_lock and set->quiesce_lock order is preserved. So the above scheme fits really well in the context annotations. We can define context annotation as follows: struct blk_mq_tag_set { ... struct list_head tag_list __guarded_by(&tag_list_lock, &quiesce_lock); unsigned int quiesce_depth __guarded_by(&quiesce_lock); ... } Thanks, --Nilay