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Wed, 7 May 2025 19:20:39 +0000 (GMT) Message-ID: <5ae53e40-b4d0-4f64-af40-7f86abb41547@linux.ibm.com> Date: Thu, 8 May 2025 00:50:37 +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 2/2] block: avoid unnecessary queue freeze in elevator_set_none() To: Ming Lei , Jens Axboe , linux-block@vger.kernel.org Cc: Christoph Hellwig References: <20250507120406.3028670-1-ming.lei@redhat.com> <20250507120406.3028670-3-ming.lei@redhat.com> Content-Language: en-US From: Nilay Shroff In-Reply-To: <20250507120406.3028670-3-ming.lei@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: 6QFBlDpL4KgHy_D6_zoBuY9s2D5s48sy X-Proofpoint-GUID: 6QFBlDpL4KgHy_D6_zoBuY9s2D5s48sy X-Authority-Analysis: v=2.4 cv=LYc86ifi c=1 sm=1 tr=0 ts=681bb28a cx=c_pps a=aDMHemPKRhS1OARIsFnwRA==:117 a=aDMHemPKRhS1OARIsFnwRA==:17 a=IkcTkHD0fZMA:10 a=dt9VzEwgFbYA:10 a=20KFwNOVAAAA:8 a=9Pzygc1LrLfXtXmLMKgA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwNTA3MDE3NCBTYWx0ZWRfX+a76lkXsOllR Ajt51Ir+hO9UDrVqe8tYAqrOqo7fI8rr//CA1gqjayl/V6LkI6Y8j2UrVFKFEjcAI4x/LgQVdbl XePc3Q6bzDaH8mVhQgYwKvUKHF/fkCVSpKpoZMRORLfXQECRFROvX05lBExLR4DWpAK0U/mYxNO dft503ttrecc3neKNppQm0lvJQTrw5rqMiPg0gcVY1R4QlVQyBfXm9zuACAdJjbDCiFIBjto3+6 xzZbzBxxhtoMJ5r942FKkNM+sIobtsvrNWDSpJbnzIb/tEjpvSm0hajUH5jBJx3pCtxxp/y0f+j nP3CHq5EzgJ+hcZdCVQBL9XRdRbKq+gvG+61r0dcfVIc1EBGycVfw7D4OgvfqW3AWFZ/pn0Dny8 WbMtFdghWlrh35gFQvhmGrqM05wUYmD550bzmhe+4v53vmpQt5R/SgirEKxL/MrJASY/BG2u X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1099,Hydra:6.0.736,FMLib:17.12.80.40 definitions=2025-05-07_06,2025-05-06_01,2025-02-21_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxlogscore=999 mlxscore=0 impostorscore=0 priorityscore=1501 spamscore=0 clxscore=1015 phishscore=0 adultscore=0 bulkscore=0 suspectscore=0 malwarescore=0 lowpriorityscore=0 classifier=spam authscore=0 authtc=n/a authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2504070000 definitions=main-2505070174 On 5/7/25 5:34 PM, Ming Lei wrote: > elevator_set_none() is called when deleting disk, in which queue has been > un-registered, and elevator switch can't happen any more. > > So if q->elevator is NULL, it is not necessary to freeze queue and drain > IO any more. > > Signed-off-by: Ming Lei > --- > block/elevator.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/block/elevator.c b/block/elevator.c > index e1386b84a415..35f4de749dcd 100644 > --- a/block/elevator.c > +++ b/block/elevator.c > @@ -754,8 +754,18 @@ void elevator_set_none(struct request_queue *q) > .name = "none", > .quiesce_queue = true, > }; > + bool need_change; > int err; > > + WARN_ON_ONCE(blk_queue_registered(q)); > + > + /* queue has been unregisted, elevator can't be switched anymore */ > + mutex_lock(&q->elevator_lock); > + need_change = !!q->elevator; > + mutex_unlock(&q->elevator_lock); > + if (!need_change) > + return; > + > err = elevator_change(q, &ctx); > if (err < 0) > pr_warn("%s: set none elevator failed %d\n", __func__, err); What in case blk_unregister_queue/elevator_set_none is called from __add_disk ? The __add_disk and elv_iosched_store may run concurrently. So I think we should remove sysfs entries (i.e. delete disk->queue_kobj) before calling elevator_set_none() from blk_unregister_queue(). Thanks, --Nilay