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Wed, 29 Oct 2025 10:36:52 +0000 (GMT) From: Nilay Shroff To: linux-block@vger.kernel.org Cc: ming.lei@redhat.com, hch@lst.de, axboe@kernel.dk, yi.zhang@redhat.com, czhong@redhat.com, gjoyce@ibm.com Subject: [PATCHv3 4/4] block: define alloc_sched_data and free_sched_data methods for kyber Date: Wed, 29 Oct 2025 16:06:17 +0530 Message-ID: <20251029103622.205607-5-nilay@linux.ibm.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20251029103622.205607-1-nilay@linux.ibm.com> References: <20251029103622.205607-1-nilay@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=K+gv3iWI c=1 sm=1 tr=0 ts=6901ee4c cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=x6icFKpwvdMA:10 a=VkNPw1HP01LnGYTKEx00:22 a=VwQbUJbxAAAA:8 a=pGLkceISAAAA:8 a=20KFwNOVAAAA:8 a=VnNF1IyMAAAA:8 a=1sDiDhgU5wRd15m8xSAA:9 a=cPQSjfK2_nFv0Q5t_7PE:22 X-Proofpoint-ORIG-GUID: JFL0HebPwaaB9PaPR-CWwaHrxqnkvzqu X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUxMDI4MDE2NiBTYWx0ZWRfX74sXxHBmMvA1 PP32OCjM3R3teETQN0V4Y3VPYBoRse94mRcEDExnP2SzbJYcFpi2AC+T3q8Z1riImnbmL266TZP xfJXWkdlGWfBtM4pZgXsJ23toI9mi9dK6i/xZCHZeCO/dS37pC/STxRRvDCWFO0vwZ/29L29gmH M7KBFcFmYaWhLCxpURLc/nnvOM5LPsdJ9tqB7PXgQj5qBN9lNH39nb7HiPDP+OvkoieMKlVDIU8 XugL2hH4htMzKI5BVdxrm9n2qRiLsdEaDmsrTN+90LOkdBSyrb4GLWLw2pf3f0Q9jd7D5XQdQV0 e19e2RZ3K7b4E1MLEef5TSqaS/TZ8vkA+oe6Rmh9pyIt9MjMoFkvYTE40kQvMtqo48ZCK1MPhMr IeeJ29CiJmUr91Aolq5BV2w66iPgKw== X-Proofpoint-GUID: JFL0HebPwaaB9PaPR-CWwaHrxqnkvzqu X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.9,FMLib:17.12.80.40 definitions=2025-10-29_04,2025-10-22_01,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 priorityscore=1501 impostorscore=0 suspectscore=0 adultscore=0 clxscore=1015 malwarescore=0 phishscore=0 spamscore=0 bulkscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2510240000 definitions=main-2510280166 Currently, the Kyber elevator allocates its private data dynamically in ->init_sched and frees it in ->exit_sched. However, since ->init_sched is invoked during elevator switch after acquiring both ->freeze_lock and ->elevator_lock, it may trigger the lockdep splat [1] due to dependency on pcpu_alloc_mutex. To resolve this, move the elevator data allocation and deallocation logic from ->init_sched and ->exit_sched into the newly introduced ->alloc_sched_data and ->free_sched_data methods. These callbacks are invoked before acquiring ->freeze_lock and ->elevator_lock, ensuring that memory allocation happens safely without introducing additional locking dependencies. This change breaks the dependency chain involving pcpu_alloc_mutex and prevents the reported lockdep warning. [1] https://lore.kernel.org/all/CAGVVp+VNW4M-5DZMNoADp6o2VKFhi7KxWpTDkcnVyjO0=-D5+A@mail.gmail.com/ Reported-by: Changhui Zhong Reported-by: Yi Zhang Closes: https://lore.kernel.org/all/CAGVVp+VNW4M-5DZMNoADp6o2VKFhi7KxWpTDkcnVyjO0=-D5+A@mail.gmail.com/ Tested-by: Yi Zhang Signed-off-by: Nilay Shroff --- block/kyber-iosched.c | 30 ++++++++++++++++++++++-------- 1 file changed, 22 insertions(+), 8 deletions(-) diff --git a/block/kyber-iosched.c b/block/kyber-iosched.c index 18efd6ef2a2b..c1b36ffd19ce 100644 --- a/block/kyber-iosched.c +++ b/block/kyber-iosched.c @@ -409,30 +409,42 @@ static void kyber_depth_updated(struct request_queue *q) static int kyber_init_sched(struct request_queue *q, struct elevator_queue *eq) { - struct kyber_queue_data *kqd; - - kqd = kyber_queue_data_alloc(q); - if (IS_ERR(kqd)) - return PTR_ERR(kqd); - blk_stat_enable_accounting(q); blk_queue_flag_clear(QUEUE_FLAG_SQ_SCHED, q); - eq->elevator_data = kqd; q->elevator = eq; kyber_depth_updated(q); return 0; } +static void *kyber_alloc_sched_data(struct request_queue *q) +{ + struct kyber_queue_data *kqd; + + kqd = kyber_queue_data_alloc(q); + if (IS_ERR(kqd)) + return NULL; + + return kqd; +} + static void kyber_exit_sched(struct elevator_queue *e) { struct kyber_queue_data *kqd = e->elevator_data; - int i; timer_shutdown_sync(&kqd->timer); blk_stat_disable_accounting(kqd->q); +} + +static void kyber_free_sched_data(void *elv_data) +{ + struct kyber_queue_data *kqd = elv_data; + int i; + + if (!kqd) + return; for (i = 0; i < KYBER_NUM_DOMAINS; i++) sbitmap_queue_free(&kqd->domain_tokens[i]); @@ -1004,6 +1016,8 @@ static struct elevator_type kyber_sched = { .exit_sched = kyber_exit_sched, .init_hctx = kyber_init_hctx, .exit_hctx = kyber_exit_hctx, + .alloc_sched_data = kyber_alloc_sched_data, + .free_sched_data = kyber_free_sched_data, .limit_depth = kyber_limit_depth, .bio_merge = kyber_bio_merge, .prepare_request = kyber_prepare_request, -- 2.51.0