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Thu, 1 May 2025 09:55:03 +0000 (GMT) Message-ID: <1b9ddb33-2db2-490a-a3f3-cd91d8837c7a@linux.ibm.com> Date: Thu, 1 May 2025 15:25:01 +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 V4 11/24] block: move blk_queue_registered() check into elv_iosched_store() To: Ming Lei , Jens Axboe , linux-block@vger.kernel.org Cc: Shinichiro Kawasaki , =?UTF-8?Q?Thomas_Hellstr=C3=B6m?= , Christoph Hellwig References: <20250430043529.1950194-1-ming.lei@redhat.com> <20250430043529.1950194-12-ming.lei@redhat.com> Content-Language: en-US From: Nilay Shroff In-Reply-To: <20250430043529.1950194-12-ming.lei@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: vK6Y0zqmTCjD0tNpwDdy9kKxiHVCuJEF X-Proofpoint-ORIG-GUID: vK6Y0zqmTCjD0tNpwDdy9kKxiHVCuJEF X-Authority-Analysis: v=2.4 cv=LKNmQIW9 c=1 sm=1 tr=0 ts=681344fc cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=IkcTkHD0fZMA:10 a=dt9VzEwgFbYA:10 a=20KFwNOVAAAA:8 a=MkBpbG05XsvgUO-hY6AA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwNTAxMDA3MiBTYWx0ZWRfX+9RTdE74qlto sDEoh8EdLEEpDEcEpuDG8uIgkBaxRqQkzQK0Y+WphfGQxWHQ1hxXYd55W7xNvTgDuTSngo/l7Va YfW78uS8GikNpWvALf3S3KQDQ+6tvhp+LVoX5EcdNzhH0Lnro6M/MaaBtJrnieE5y9GoZ3nfTSN MLrn6bCbqiRFkzhBMNTaa6wTL3iklQizMO6jZEJxfSQNucDlLwY+wpz2jrbtS81z4kOtpef1K0S ZWpPFxzqUszl/2EyLYaU8BRkbBSUnBljUN0mebU55BHCGlOKWN2ISIbz3OrmaN6TzhO/4911Uk/ x5MQHQ0LVWSeePokUHkjJ0YIvWH6oze6rAUmPtwGccfytncBX24OMNdmaHtM4S8vt/Y3xUXgTOI VQn/otw1iWG5HuKV3k7SQwvD/DSyvmnpJPRNYDVJAAZBur5Z3rm1lDurYqZlkZ7MNPmAPkls 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=2025-05-01_03,2025-04-24_02,2025-02-21_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 priorityscore=1501 malwarescore=0 suspectscore=0 spamscore=0 mlxscore=0 impostorscore=0 adultscore=0 bulkscore=0 mlxlogscore=999 clxscore=1015 phishscore=0 classifier=spam authscore=0 authtc=n/a authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2504070000 definitions=main-2505010072 On 4/30/25 10:05 AM, Ming Lei wrote: > Move blk_queue_registered() check into elv_iosched_store() and prepare > for using elevator_change() for covering any kind of elevator change in > adding/deleting disk and updating nr_hw_queue. > > Signed-off-by: Ming Lei > --- > block/elevator.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/block/elevator.c b/block/elevator.c > index df3e59107a2a..ac72c4f5a542 100644 > --- a/block/elevator.c > +++ b/block/elevator.c > @@ -676,10 +676,6 @@ int elevator_switch(struct request_queue *q, const char *name) > */ > static int elevator_change(struct request_queue *q, const char *elevator_name) > { > - /* Make sure queue is not in the middle of being removed */ > - if (!blk_queue_registered(q)) > - return -ENOENT; > - > if (q->elevator && elevator_match(q->elevator->type, elevator_name)) > return 0; > > @@ -708,6 +704,10 @@ ssize_t elv_iosched_store(struct gendisk *disk, const char *buf, > struct request_queue *q = disk->queue; > struct blk_mq_tag_set *set = q->tag_set; > > + /* Make sure queue is not in the middle of being removed */ > + if (!blk_queue_registered(q)) > + return -ENOENT; > + > /* > * If the attribute needs to load a module, do it before freezing the > * queue to ensure that the module file can be read when the request Shouldn't blk_queue_registered needs protection? For instance, I see here a race while queue is being removed from del_gendisk and at the same time elevator is being updated from elv_iosched_store. BTW, I saw that your patch 19/24 adds that protection using disable_elv_switch before deleting disk (and so you may want to fold this patch 11/24 into patch 19/24 ?) but with that also I foresee a thin race window. I will comment on it while reviewing the patch 19/24. Thanks, --Nilay