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Thu, 14 Aug 2025 08:26:18 +0000 (GMT) From: Nilay Shroff To: linux-block@vger.kernel.org Cc: axboe@kernel.dk, ming.lei@redhat.com, yukuai1@huaweicloud.com, hch@lst.de, shinichiro.kawasaki@wdc.com, kch@nvidia.com, gjoyce@ibm.com Subject: [PATCHv3 2/3] block: decrement block_rq_qos static key in rq_qos_del() Date: Thu, 14 Aug 2025 13:54:58 +0530 Message-ID: <20250814082612.500845-3-nilay@linux.ibm.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20250814082612.500845-1-nilay@linux.ibm.com> References: <20250814082612.500845-1-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=KPRaDEFo c=1 sm=1 tr=0 ts=689d9daf cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=2OwXVqhp2XgA:10 a=VnNF1IyMAAAA:8 a=SYFAYIXRm5ESkqApvb4A:9 X-Proofpoint-ORIG-GUID: EwCDCbU5Xzid4rL0FKr10s6ENUPLBsp1 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwODEyMDIyNCBTYWx0ZWRfX2f+Ceo4yA4qD +FDqUorqwpax7Pejz9dtcUHqAV9ZPxbXjYvFtoh4jS5oO0rji+e0fZYrbBWbMSLGzL7dfwUx7KM C8aFbJ9gWoQsp/KKrswnr0wp+Jwj0zj2qitR8+EiOGx4X8SQXpdr98x4lILHPynCjS9waPh6xTe tSG2nxm3JZjrurvj8jEsDIUYnGOp4AO48dJ565+6pvYHq/N1OJlbJ9pl1y//p3k9OBbN1mHKtTt H05piUBE+1Xo5MEvE4z8J/QugjuWIeLU6cuaW2okae6R2+VNw72q9ZHitjMPu46T4bg/lpQB608 w6s4/U+757SRFmH9VImls9eCRka8se/j15ZQDjcW8uJb4CiGO4/1IE64KkZIgCAmvU7CVlwc6Px SU1ovMB/ X-Proofpoint-GUID: EwCDCbU5Xzid4rL0FKr10s6ENUPLBsp1 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1099,Hydra:6.1.9,FMLib:17.12.80.40 definitions=2025-08-13_02,2025-08-11_01,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 impostorscore=0 bulkscore=0 adultscore=0 priorityscore=1501 malwarescore=0 spamscore=0 clxscore=1015 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2507300000 definitions=main-2508120224 rq_qos_add() increments the block_rq_qos static key when a QoS policy is attached. When a QoS policy is removed via rq_qos_del(), we must symmetrically decrement the static key. If this removal drops the last QoS policy from the queue (q->rq_qos becomes NULL), the static branch can be disabled and the jump label patched to a NOP, avoiding overhead on the hot path. This change ensures rq_qos_add()/rq_qos_del() keep the block_rq_qos static key balanced and prevents leaving the branch permanently enabled after the last policy is removed. Fixes: 033b667a823e ("block: blk-rq-qos: guard rq-qos helpers by static key") Signed-off-by: Nilay Shroff --- block/blk-rq-qos.c | 1 + 1 file changed, 1 insertion(+) diff --git a/block/blk-rq-qos.c b/block/blk-rq-qos.c index 848591fb3c57..b1e24bb85ad2 100644 --- a/block/blk-rq-qos.c +++ b/block/blk-rq-qos.c @@ -374,6 +374,7 @@ void rq_qos_del(struct rq_qos *rqos) for (cur = &q->rq_qos; *cur; cur = &(*cur)->next) { if (*cur == rqos) { *cur = rqos->next; + static_branch_dec(&block_rq_qos); break; } } -- 2.50.1