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Mon, 17 Nov 2025 10:11:04 +0000 (GMT) Message-ID: <8bb140e5-ac13-4947-98e4-6e35cdf5fc75@linux.ibm.com> Date: Mon, 17 Nov 2025 15:41:03 +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 RESEND 2/5] blk-wbt: fix incorrect lock order for rq_qos_mutex and freeze queue To: Yu Kuai , axboe@kernel.dk, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, tj@kernel.org, ming.lei@redhat.com References: <20251116041024.120500-1-yukuai@fnnas.com> <20251116041024.120500-3-yukuai@fnnas.com> Content-Language: en-US From: Nilay Shroff In-Reply-To: <20251116041024.120500-3-yukuai@fnnas.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=C/nkCAP+ c=1 sm=1 tr=0 ts=691af4bc cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=IkcTkHD0fZMA:10 a=6UeiqGixMTsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=tJLSzyRPAAAA:8 a=VnNF1IyMAAAA:8 a=L4sSNPb1VJOVPSNS_QsA:9 a=QEXdDO2ut3YA:10 a=ZXulRonScM0A:10 a=H0xsmVfZzgdqH4_HIfU3:22 a=cPQSjfK2_nFv0Q5t_7PE:22 X-Proofpoint-GUID: TOU6647_dogJ0XJmGBaRwIBWdYRyx1L9 X-Proofpoint-ORIG-GUID: TOU6647_dogJ0XJmGBaRwIBWdYRyx1L9 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUxMTE1MDAzMiBTYWx0ZWRfXy49Fa6/W0YQI WzpgCdEMMJlU5D1CKSge5fWLBNlyQJC0GSxRP31bluhd08u8yF3rovuw7TVUGn1J/3RllGg82bZ TpdbNbITdtlcbNKGSwu7UI3GAfbjkXT/zv0OUgKG0/gzRSsPFNMp7E7s8k6pqws2As25pdNcRas QXg0KA5sOUwgXuSkxlHaRrb2u83FhzYlGmlWep2XtzGpfWHzpJsp8uTtPzt1IweBbil7vcWNTfn Fxe/fXDPoAkV6zb+dOuY/sPFx781PkCaUeCh9aW5Hh63g5yUfSi+86fdamoBIkSaozAmEHP+fUd cIrn12G+zy9MPrmxR2s6YdH85XT16wLXdpjCkjezgQ7ATLf+I4BM894gax2SDe+kuenW4vFuf/1 3iPqYlcuLiuEq7nTa7ZbjlyOUMtdkg== 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=2025-11-17_02,2025-11-13_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 priorityscore=1501 spamscore=0 impostorscore=0 bulkscore=0 malwarescore=0 suspectscore=0 clxscore=1015 lowpriorityscore=0 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2510240000 definitions=main-2511150032 On 11/16/25 9:40 AM, Yu Kuai wrote: > wbt_init() can be called from sysfs attribute and wbt_enable_default(), > however the lock order are inversely. > > - queue_wb_lat_store() freeze queue first, and then wbt_init() hold > rq_qos_mutex. In this case queue will be freezed again inside > rq_qos_add(), however, in this case freeze queue recursivly is > inoperative; > - wbt_enable_default() from elevator switch will hold rq_qos_mutex > first, and then rq_qos_add() will freeze queue; > > Fix this problem by converting to use new helper rq_qos_add_freezed() in > wbt_init(), and for wbt_enable_default(), freeze queue before calling > wbt_init(). > > Fixes: a13bd91be223 ("block/rq_qos: protect rq_qos apis with a new lock") > Signed-off-by: Yu Kuai Looks good to me: Reviewed-by: Nilay Shroff