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Tue, 28 Jan 2025 14:34:44 +0000 Received: from smtpav07.fra02v.mail.ibm.com (smtpav07.fra02v.mail.ibm.com [10.20.54.106]) by smtprelay01.fra02v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 50SEYhcN53215498 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 28 Jan 2025 14:34:43 GMT Received: from smtpav07.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 2206A200A7; Tue, 28 Jan 2025 14:34:43 +0000 (GMT) Received: from smtpav07.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id D549C200A8; Tue, 28 Jan 2025 14:34:41 +0000 (GMT) Received: from li-c9696b4c-3419-11b2-a85c-f9edc3bf8a84.ibm.com.com (unknown [9.171.95.231]) by smtpav07.fra02v.mail.ibm.com (Postfix) with ESMTP; Tue, 28 Jan 2025 14:34:41 +0000 (GMT) From: Nilay Shroff To: linux-block@vger.kernel.org Cc: hch@lst.de, ming.lei@redhat.com, dlemoal@kernel.org, axboe@kernel.dk, gjoyce@ibm.com Subject: [RFC PATCHv3 2/2] block: fix nr_hw_queue update racing with disk addition/removal Date: Tue, 28 Jan 2025 20:04:14 +0530 Message-ID: <20250128143436.874357-3-nilay@linux.ibm.com> X-Mailer: git-send-email 2.47.1 In-Reply-To: <20250128143436.874357-1-nilay@linux.ibm.com> References: <20250128143436.874357-1-nilay@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: dMOjqT1QqhGdmNDrP85oMwH-ih4FnxEz X-Proofpoint-GUID: dMOjqT1QqhGdmNDrP85oMwH-ih4FnxEz X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1057,Hydra:6.0.680,FMLib:17.12.68.34 definitions=2025-01-28_04,2025-01-27_01,2024-11-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 mlxscore=0 mlxlogscore=993 malwarescore=0 phishscore=0 priorityscore=1501 clxscore=1015 spamscore=0 suspectscore=0 adultscore=0 impostorscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2411120000 definitions=main-2501280108 The nr_hw_queue update could potentially race with disk addtion/removal while registering/unregistering hctx sysfs files. The __blk_mq_update_ nr_hw_queues() runs with q->tag_list_lock held and so to avoid it racing with disk addition/removal we should acquire q->tag_list_lock while registering/unregistering hctx sysfs files. With this patch, blk_mq_sysfs_register() (called during disk addition) and blk_mq_sysfs_unregister() (called during disk removal) now runs with q->tag_list_lock held so that it avoids racing with __blk_mq_update _nr_hw_queues(). Signed-off-by: Nilay Shroff Reviewed-by: Christoph Hellwig Reviewed-by: Hannes Reinecke --- block/blk-mq-sysfs.c | 17 +++++++++-------- 1 file changed, 9 insertions(+), 8 deletions(-) diff --git a/block/blk-mq-sysfs.c b/block/blk-mq-sysfs.c index 6113328abd70..3feeeccf8a99 100644 --- a/block/blk-mq-sysfs.c +++ b/block/blk-mq-sysfs.c @@ -225,25 +225,25 @@ int blk_mq_sysfs_register(struct gendisk *disk) ret = kobject_add(q->mq_kobj, &disk_to_dev(disk)->kobj, "mq"); if (ret < 0) - goto out; + return ret; kobject_uevent(q->mq_kobj, KOBJ_ADD); + mutex_lock(&q->tag_set->tag_list_lock); queue_for_each_hw_ctx(q, hctx, i) { ret = blk_mq_register_hctx(hctx); if (ret) - goto unreg; + goto out_unreg; } + mutex_unlock(&q->tag_set->tag_list_lock); + return 0; - -out: - return ret; - -unreg: +out_unreg: queue_for_each_hw_ctx(q, hctx, j) { if (j < i) blk_mq_unregister_hctx(hctx); } + mutex_unlock(&q->tag_set->tag_list_lock); kobject_uevent(q->mq_kobj, KOBJ_REMOVE); kobject_del(q->mq_kobj); @@ -256,9 +256,10 @@ void blk_mq_sysfs_unregister(struct gendisk *disk) struct blk_mq_hw_ctx *hctx; unsigned long i; - + mutex_lock(&q->tag_set->tag_list_lock); queue_for_each_hw_ctx(q, hctx, i) blk_mq_unregister_hctx(hctx); + mutex_unlock(&q->tag_set->tag_list_lock); kobject_uevent(q->mq_kobj, KOBJ_REMOVE); kobject_del(q->mq_kobj);