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Thu, 18 Dec 2025 14:33:27 +0000 (GMT) Message-ID: <6a72b97f-aa13-4a6e-b165-57faa56597fa@linux.ibm.com> Date: Thu, 18 Dec 2025 20:03:25 +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 v5 04/13] blk-rq-qos: fix possible debugfs_mutex deadlock To: Yu Kuai , axboe@kernel.dk, linux-block@vger.kernel.org, tj@kernel.org, ming.lei@redhat.com References: <20251214101409.1723751-1-yukuai@fnnas.com> <20251214101409.1723751-5-yukuai@fnnas.com> Content-Language: en-US From: Nilay Shroff In-Reply-To: <20251214101409.1723751-5-yukuai@fnnas.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUxMjEzMDAxOCBTYWx0ZWRfX16YAIuFqb+Er VhnORrENPD7FQESqmUtk8GpA3kAZgwD5vSZf8V9oAv0e6MfrlsL58a6LCcuKVY0zkWxon3arkwR HCHCEDVcMC2LRG3Uo+wc5KEipkYBsUgKjTeXJKa+7m1erOxmsSej3Jzo1BKb/gaTEYE8egdXqYD kITVAPY8V2C1mrlWoqd47Rbp7Df9l4pLBh9xsOjuHz2VGIEVjtqyBI0sWk0kpdBKu8kpB/HhVbs DOl6wvNlfVEIQuYou5sp3OltRSFeeTInRbHUeeVRgGCiWeIvr4f8iJDu96nu06ITO/A0x4jZm/m Ssqs2nKbMSYX9pcbvJ6M9vhN5/FqDRuD4ffBaCfDd/dCOjzCzB5p7LxoEL/zIPdlQs4UH4mrDw/ yBUktGP7Dm9qowcDGirOQL4Rwiawnw== X-Proofpoint-GUID: NUyVjyM5LdI_TN3m5n6QN-LQfhih1ZNj X-Proofpoint-ORIG-GUID: NUyVjyM5LdI_TN3m5n6QN-LQfhih1ZNj X-Authority-Analysis: v=2.4 cv=LbYxKzfi c=1 sm=1 tr=0 ts=694410bc cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=IkcTkHD0fZMA:10 a=wP3pNCr1ah4A:10 a=VkNPw1HP01LnGYTKEx00:22 a=tJLSzyRPAAAA:8 a=VnNF1IyMAAAA:8 a=rTDWk-x5bkgnBn-qG3IA:9 a=QEXdDO2ut3YA:10 a=H0xsmVfZzgdqH4_HIfU3:22 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.9,FMLib:17.12.100.49 definitions=2025-12-18_02,2025-12-17_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 spamscore=0 phishscore=0 clxscore=1015 suspectscore=0 adultscore=0 malwarescore=0 priorityscore=1501 lowpriorityscore=0 impostorscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2510240000 definitions=main-2512130018 On 12/14/25 3:43 PM, Yu Kuai wrote: > Currently rq-qos debugfs entries are created from rq_qos_add(), while > rq_qos_add() can be called while queue is still frozen. This can > deadlock because creating new entries can trigger fs reclaim. > > Fix this problem by delaying creating rq-qos debugfs entries after queue > is unfrozen. > > - For wbt, 1) it can be initialized by default, fix it by calling new > helper after wbt_init() from wbt_enable_default; 2) it can be > initialized by sysfs, fix it by calling new helper after queue is > unfrozen from queue_wb_lat_store(). > - For iocost and iolatency, they can only be initialized by blkcg > configuration, however, they don't have debugfs entries for now, hence > they are not handled yet. > > Signed-off-by: Yu Kuai Looks good to me: Reviewed-by: Nilay Shroff