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Thu, 23 Jan 2025 17:41:30 +0000 Received: from smtpav03.fra02v.mail.ibm.com (smtpav03.fra02v.mail.ibm.com [10.20.54.102]) by smtprelay07.fra02v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 50NHfTjb65536394 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 23 Jan 2025 17:41:29 GMT Received: from smtpav03.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 0509120043; Thu, 23 Jan 2025 17:41:29 +0000 (GMT) Received: from smtpav03.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 9D45220040; Thu, 23 Jan 2025 17:41:27 +0000 (GMT) Received: from li-c9696b4c-3419-11b2-a85c-f9edc3bf8a84.ibm.com.com (unknown [9.171.46.6]) by smtpav03.fra02v.mail.ibm.com (Postfix) with ESMTP; Thu, 23 Jan 2025 17:41:27 +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 PATCHv2 1/2] block: get rid of request queue ->sysfs_dir_lock Date: Thu, 23 Jan 2025 23:10:23 +0530 Message-ID: <20250123174124.24554-2-nilay@linux.ibm.com> X-Mailer: git-send-email 2.47.1 In-Reply-To: <20250123174124.24554-1-nilay@linux.ibm.com> References: <20250123174124.24554-1-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-GUID: 11pBYqcfCkmAH1f05GLO34yGd2-eIy64 X-Proofpoint-ORIG-GUID: 11pBYqcfCkmAH1f05GLO34yGd2-eIy64 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=2025-01-23_07,2025-01-23_01,2024-11-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 impostorscore=0 mlxscore=0 suspectscore=0 phishscore=0 mlxlogscore=999 malwarescore=0 adultscore=0 clxscore=1015 lowpriorityscore=0 bulkscore=0 spamscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2411120000 definitions=main-2501230125 The request queue uses ->sysfs_dir_lock for protecting the addition/ deletion of kobject entries under sysfs while we register/unregister blk-mq. However kobject addition/deletion is already protected with kernfs/sysfs internal synchronization primitives. So use of q->sysfs_ dir_lock seems redundant. Moreover, q->sysfs_dir_lock is also used at few other callsites along with q->sysfs_lock for protecting the addition/deletion of kojects. One such example is when we register with sysfs a set of independent access ranges for a disk. Here as well we could get rid off q->sysfs_ dir_lock and only use q->sysfs_lock. The only variable which q->sysfs_dir_lock appears to protect is q-> mq_sysfs_init_done which is set/unset while registering/unregistering blk-mq with sysfs. But use of q->mq_sysfs_init_done could be easily replaced using queue registered bit QUEUE_FLAG_REGISTERED. So with this patch we remove q->sysfs_dir_lock from each callsite and replace q->mq_sysfs_init_done using QUEUE_FLAG_REGISTERED. Signed-off-by: Nilay Shroff Reviewed-by: Christoph Hellwig --- block/blk-core.c | 1 - block/blk-ia-ranges.c | 4 ---- block/blk-mq-sysfs.c | 23 +++++------------------ block/blk-sysfs.c | 5 ----- include/linux/blkdev.h | 3 --- 5 files changed, 5 insertions(+), 31 deletions(-) diff --git a/block/blk-core.c b/block/blk-core.c index 32fb28a6372c..d6c4fa3943b5 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -430,7 +430,6 @@ struct request_queue *blk_alloc_queue(struct queue_limits *lim, int node_id) refcount_set(&q->refs, 1); mutex_init(&q->debugfs_mutex); mutex_init(&q->sysfs_lock); - mutex_init(&q->sysfs_dir_lock); mutex_init(&q->limits_lock); mutex_init(&q->rq_qos_mutex); spin_lock_init(&q->queue_lock); diff --git a/block/blk-ia-ranges.c b/block/blk-ia-ranges.c index c9eb4241e048..d479f5481b66 100644 --- a/block/blk-ia-ranges.c +++ b/block/blk-ia-ranges.c @@ -111,7 +111,6 @@ int disk_register_independent_access_ranges(struct gendisk *disk) struct request_queue *q = disk->queue; int i, ret; - lockdep_assert_held(&q->sysfs_dir_lock); lockdep_assert_held(&q->sysfs_lock); if (!iars) @@ -155,7 +154,6 @@ void disk_unregister_independent_access_ranges(struct gendisk *disk) struct blk_independent_access_ranges *iars = disk->ia_ranges; int i; - lockdep_assert_held(&q->sysfs_dir_lock); lockdep_assert_held(&q->sysfs_lock); if (!iars) @@ -289,7 +287,6 @@ void disk_set_independent_access_ranges(struct gendisk *disk, { struct request_queue *q = disk->queue; - mutex_lock(&q->sysfs_dir_lock); mutex_lock(&q->sysfs_lock); if (iars && !disk_check_ia_ranges(disk, iars)) { kfree(iars); @@ -313,6 +310,5 @@ void disk_set_independent_access_ranges(struct gendisk *disk, disk_register_independent_access_ranges(disk); unlock: mutex_unlock(&q->sysfs_lock); - mutex_unlock(&q->sysfs_dir_lock); } EXPORT_SYMBOL_GPL(disk_set_independent_access_ranges); diff --git a/block/blk-mq-sysfs.c b/block/blk-mq-sysfs.c index 156e9bb07abf..6113328abd70 100644 --- a/block/blk-mq-sysfs.c +++ b/block/blk-mq-sysfs.c @@ -223,8 +223,6 @@ int blk_mq_sysfs_register(struct gendisk *disk) unsigned long i, j; int ret; - lockdep_assert_held(&q->sysfs_dir_lock); - ret = kobject_add(q->mq_kobj, &disk_to_dev(disk)->kobj, "mq"); if (ret < 0) goto out; @@ -237,7 +235,6 @@ int blk_mq_sysfs_register(struct gendisk *disk) goto unreg; } - q->mq_sysfs_init_done = true; out: return ret; @@ -259,15 +256,12 @@ void blk_mq_sysfs_unregister(struct gendisk *disk) struct blk_mq_hw_ctx *hctx; unsigned long i; - lockdep_assert_held(&q->sysfs_dir_lock); queue_for_each_hw_ctx(q, hctx, i) blk_mq_unregister_hctx(hctx); kobject_uevent(q->mq_kobj, KOBJ_REMOVE); kobject_del(q->mq_kobj); - - q->mq_sysfs_init_done = false; } void blk_mq_sysfs_unregister_hctxs(struct request_queue *q) @@ -275,15 +269,11 @@ void blk_mq_sysfs_unregister_hctxs(struct request_queue *q) struct blk_mq_hw_ctx *hctx; unsigned long i; - mutex_lock(&q->sysfs_dir_lock); - if (!q->mq_sysfs_init_done) - goto unlock; + if (!blk_queue_registered(q)) + return; queue_for_each_hw_ctx(q, hctx, i) blk_mq_unregister_hctx(hctx); - -unlock: - mutex_unlock(&q->sysfs_dir_lock); } int blk_mq_sysfs_register_hctxs(struct request_queue *q) @@ -292,9 +282,8 @@ int blk_mq_sysfs_register_hctxs(struct request_queue *q) unsigned long i; int ret = 0; - mutex_lock(&q->sysfs_dir_lock); - if (!q->mq_sysfs_init_done) - goto unlock; + if (!blk_queue_registered(q)) + goto out; queue_for_each_hw_ctx(q, hctx, i) { ret = blk_mq_register_hctx(hctx); @@ -302,8 +291,6 @@ int blk_mq_sysfs_register_hctxs(struct request_queue *q) break; } -unlock: - mutex_unlock(&q->sysfs_dir_lock); - +out: return ret; } diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c index e09b455874bf..7b970e6765e7 100644 --- a/block/blk-sysfs.c +++ b/block/blk-sysfs.c @@ -764,7 +764,6 @@ int blk_register_queue(struct gendisk *disk) struct request_queue *q = disk->queue; int ret; - mutex_lock(&q->sysfs_dir_lock); kobject_init(&disk->queue_kobj, &blk_queue_ktype); ret = kobject_add(&disk->queue_kobj, &disk_to_dev(disk)->kobj, "queue"); if (ret < 0) @@ -805,7 +804,6 @@ int blk_register_queue(struct gendisk *disk) if (q->elevator) kobject_uevent(&q->elevator->kobj, KOBJ_ADD); mutex_unlock(&q->sysfs_lock); - mutex_unlock(&q->sysfs_dir_lock); /* * SCSI probing may synchronously create and destroy a lot of @@ -830,7 +828,6 @@ int blk_register_queue(struct gendisk *disk) mutex_unlock(&q->sysfs_lock); out_put_queue_kobj: kobject_put(&disk->queue_kobj); - mutex_unlock(&q->sysfs_dir_lock); return ret; } @@ -861,7 +858,6 @@ void blk_unregister_queue(struct gendisk *disk) blk_queue_flag_clear(QUEUE_FLAG_REGISTERED, q); mutex_unlock(&q->sysfs_lock); - mutex_lock(&q->sysfs_dir_lock); /* * Remove the sysfs attributes before unregistering the queue data * structures that can be modified through sysfs. @@ -878,7 +874,6 @@ void blk_unregister_queue(struct gendisk *disk) /* Now that we've deleted all child objects, we can delete the queue. */ kobject_uevent(&disk->queue_kobj, KOBJ_REMOVE); kobject_del(&disk->queue_kobj); - mutex_unlock(&q->sysfs_dir_lock); blk_debugfs_remove(disk); } diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 76f0a4e7c2e5..248416ecd01c 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -561,7 +561,6 @@ struct request_queue { struct list_head flush_list; struct mutex sysfs_lock; - struct mutex sysfs_dir_lock; struct mutex limits_lock; /* @@ -605,8 +604,6 @@ struct request_queue { * Serializes all debugfs metadata operations using the above dentries. */ struct mutex debugfs_mutex; - - bool mq_sysfs_init_done; }; /* Keep blk_queue_flag_name[] in sync with the definitions below */ From patchwork Thu Jan 23 17:40:24 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Nilay Shroff X-Patchwork-Id: 13948513 Received: from mx0b-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 55DB5147C96 for ; Thu, 23 Jan 2025 17:41:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=148.163.158.5 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1737654102; cv=none; 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Thu, 23 Jan 2025 17:41:29 +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 PATCHv2 2/2] block: fix nr_hw_queue update racing with disk addition/removal Date: Thu, 23 Jan 2025 23:10:24 +0530 Message-ID: <20250123174124.24554-3-nilay@linux.ibm.com> X-Mailer: git-send-email 2.47.1 In-Reply-To: <20250123174124.24554-1-nilay@linux.ibm.com> References: <20250123174124.24554-1-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-GUID: ufaSCIUDi2czDKVvJBJOBOp4ZIFD_Rkd X-Proofpoint-ORIG-GUID: ufaSCIUDi2czDKVvJBJOBOp4ZIFD_Rkd 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=2025-01-23_07,2025-01-23_01,2024-11-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 impostorscore=0 adultscore=0 malwarescore=0 bulkscore=0 priorityscore=1501 clxscore=1015 mlxscore=0 phishscore=0 lowpriorityscore=0 mlxlogscore=971 spamscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2411120000 definitions=main-2501230128 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 --- block/blk-mq-sysfs.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/block/blk-mq-sysfs.c b/block/blk-mq-sysfs.c index 6113328abd70..2b9df2b73bf6 100644 --- a/block/blk-mq-sysfs.c +++ b/block/blk-mq-sysfs.c @@ -229,22 +229,31 @@ int blk_mq_sysfs_register(struct gendisk *disk) 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) + if (ret) { + mutex_unlock(&q->tag_set->tag_list_lock); goto unreg; + } } + mutex_unlock(&q->tag_set->tag_list_lock); out: return ret; unreg: + mutex_lock(&q->tag_set->tag_list_lock); + 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); return ret; @@ -256,10 +265,13 @@ 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); }