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Thu, 16 Oct 2025 05:31:04 +0000 (GMT) From: Nilay Shroff To: linux-block@vger.kernel.org Cc: ming.lei@redhat.com, hch@lst.de, yukuai1@huaweicloud.com, axboe@kernel.dk, yi.zhang@redhat.com, czhong@redhat.com, gjoyce@ibm.com Subject: [PATCH 3/3] block: define alloc_sched_data and free_sched_data methods for kyber Date: Thu, 16 Oct 2025 11:00:49 +0530 Message-ID: <20251016053057.3457663-4-nilay@linux.ibm.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20251016053057.3457663-1-nilay@linux.ibm.com> References: <20251016053057.3457663-1-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-Proofpoint-GUID: VUH_ZV_egEqMzif3tZMdpRBTHY_LJ1nL X-Authority-Analysis: v=2.4 cv=Kr1AGGWN c=1 sm=1 tr=0 ts=68f0831d cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==: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: VUH_ZV_egEqMzif3tZMdpRBTHY_LJ1nL X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUxMDExMDAxNCBTYWx0ZWRfXwZXUL13CLN+k oivr0n/blp9JItbDiYhTSyZFnKCuyk6Sfw/0UjiufEP10TEuIrj4puzgQguFSvvWIFf2CbDS9PL t/vMKVhy+1F9TrAH4YbBFIa0uJdtIxD7J13qwZG5lEEVBY5yroYX3s9PncU+AxSzQ1UZGe20Hkz u37pI27/2bwiWQCem2UM/JY2gLA31QJbZZyqnK2EVkBdb3FIWQ+1Arb7AJW8Y8r8uRApHIY/62I piZFu99nEO2a5Hh/gO6RhDPI6IOmDJtbZHN2IAivCgA6de4Pm1w/9jxGSgJL6e3F6vn1WS30RD8 LDHO2sHpR1DBm3DMcYnDbPlt0Nlv5o8u+rub6vlDpuftrSnOSAHcJeoRfW0eOLbziXplrpGbu7a jt2PbTGPd45OUzE+0KNC4v89vJp//A== 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=2025-10-15_07,2025-10-13_01,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 priorityscore=1501 lowpriorityscore=0 bulkscore=0 adultscore=0 phishscore=0 suspectscore=0 malwarescore=0 clxscore=1015 impostorscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2510020000 definitions=main-2510110014 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