Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753724AbbGBOak (ORCPT ); Thu, 2 Jul 2015 10:30:40 -0400 Received: from mail-pa0-f44.google.com ([209.85.220.44]:33648 "EHLO mail-pa0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751106AbbGBOa2 (ORCPT ); Thu, 2 Jul 2015 10:30:28 -0400 From: Akinobu Mita To: linux-kernel@vger.kernel.org Cc: Akinobu Mita , Jens Axboe , Ming Lei Subject: [PATCH v2 1/6] blk-mq: fix sysfs registration/unregistration race Date: Thu, 2 Jul 2015 23:29:52 +0900 Message-Id: <1435847397-724-2-git-send-email-akinobu.mita@gmail.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1435847397-724-1-git-send-email-akinobu.mita@gmail.com> References: <1435847397-724-1-git-send-email-akinobu.mita@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5256 Lines: 193 There is a race between cpu hotplug handling and adding/deleting gendisk for blk-mq, where both are trying to register and unregister the same sysfs entries. CPU hotplug handling for blk-mq (blk_mq_queue_reinit) does unregister and register sysfs entries of hctx for all request queues in all_q_list. On the other hand, these entries for a request queue may have already been unregistered or in the middle of registration when CPU hotplug event occurs. Because those sysfs entries are registered by blk_mq_register_disk() after the request queue is added to all_q_list, and similarily the request queue is deleted from all_q_list after those are unregistered by blk_mq_unregister_disk(). So we need proper mutual exclusion for those registration and unregistration. Signed-off-by: Akinobu Mita Cc: Jens Axboe Cc: Ming Lei --- block/blk-core.c | 1 + block/blk-mq-sysfs.c | 44 ++++++++++++++++++++++++++++++++++---------- include/linux/blkdev.h | 3 +++ 3 files changed, 38 insertions(+), 10 deletions(-) diff --git a/block/blk-core.c b/block/blk-core.c index 82819e6..bbf67cd 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -687,6 +687,7 @@ struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id) __set_bit(QUEUE_FLAG_BYPASS, &q->queue_flags); init_waitqueue_head(&q->mq_freeze_wq); + mutex_init(&q->mq_sysfs_lock); if (blkcg_init_queue(q)) goto fail_bdi; diff --git a/block/blk-mq-sysfs.c b/block/blk-mq-sysfs.c index b79685e..79a3e8d 100644 --- a/block/blk-mq-sysfs.c +++ b/block/blk-mq-sysfs.c @@ -332,13 +332,15 @@ static void blk_mq_unregister_hctx(struct blk_mq_hw_ctx *hctx) struct blk_mq_ctx *ctx; int i; - if (!hctx->nr_ctx || !(hctx->flags & BLK_MQ_F_SYSFS_UP)) + if (!(hctx->flags & BLK_MQ_F_SYSFS_UP)) return; hctx_for_each_ctx(hctx, ctx, i) kobject_del(&ctx->kobj); kobject_del(&hctx->kobj); + + hctx->flags &= ~BLK_MQ_F_SYSFS_UP; } static int blk_mq_register_hctx(struct blk_mq_hw_ctx *hctx) @@ -347,7 +349,7 @@ static int blk_mq_register_hctx(struct blk_mq_hw_ctx *hctx) struct blk_mq_ctx *ctx; int i, ret; - if (!hctx->nr_ctx || !(hctx->flags & BLK_MQ_F_SYSFS_UP)) + if (!hctx->nr_ctx) return 0; ret = kobject_add(&hctx->kobj, &q->mq_kobj, "%u", hctx->queue_num); @@ -357,10 +359,12 @@ static int blk_mq_register_hctx(struct blk_mq_hw_ctx *hctx) hctx_for_each_ctx(hctx, ctx, i) { ret = kobject_add(&ctx->kobj, &hctx->kobj, "cpu%u", ctx->cpu); if (ret) - break; + return ret; } - return ret; + hctx->flags |= BLK_MQ_F_SYSFS_UP; + + return 0; } void blk_mq_unregister_disk(struct gendisk *disk) @@ -370,6 +374,8 @@ void blk_mq_unregister_disk(struct gendisk *disk) struct blk_mq_ctx *ctx; int i, j; + mutex_lock(&q->mq_sysfs_lock); + queue_for_each_hw_ctx(q, hctx, i) { blk_mq_unregister_hctx(hctx); @@ -384,6 +390,9 @@ void blk_mq_unregister_disk(struct gendisk *disk) kobject_put(&q->mq_kobj); kobject_put(&disk_to_dev(disk)->kobj); + + q->mq_sysfs_init_done = false; + mutex_unlock(&q->mq_sysfs_lock); } static void blk_mq_sysfs_init(struct request_queue *q) @@ -414,27 +423,30 @@ int blk_mq_register_disk(struct gendisk *disk) struct blk_mq_hw_ctx *hctx; int ret, i; + mutex_lock(&q->mq_sysfs_lock); + blk_mq_sysfs_init(q); ret = kobject_add(&q->mq_kobj, kobject_get(&dev->kobj), "%s", "mq"); if (ret < 0) - return ret; + goto out; kobject_uevent(&q->mq_kobj, KOBJ_ADD); queue_for_each_hw_ctx(q, hctx, i) { - hctx->flags |= BLK_MQ_F_SYSFS_UP; ret = blk_mq_register_hctx(hctx); if (ret) break; } - if (ret) { + if (ret) blk_mq_unregister_disk(disk); - return ret; - } + else + q->mq_sysfs_init_done = true; +out: + mutex_unlock(&q->mq_sysfs_lock); - return 0; + return ret; } EXPORT_SYMBOL_GPL(blk_mq_register_disk); @@ -443,8 +455,14 @@ void blk_mq_sysfs_unregister(struct request_queue *q) struct blk_mq_hw_ctx *hctx; int i; + mutex_lock(&q->mq_sysfs_lock); + if (!q->mq_sysfs_init_done) + goto out; + queue_for_each_hw_ctx(q, hctx, i) blk_mq_unregister_hctx(hctx); +out: + mutex_unlock(&q->mq_sysfs_lock); } int blk_mq_sysfs_register(struct request_queue *q) @@ -452,11 +470,17 @@ int blk_mq_sysfs_register(struct request_queue *q) struct blk_mq_hw_ctx *hctx; int i, ret = 0; + mutex_lock(&q->mq_sysfs_lock); + if (!q->mq_sysfs_init_done) + goto out; + queue_for_each_hw_ctx(q, hctx, i) { ret = blk_mq_register_hctx(hctx); if (ret) break; } +out: + mutex_unlock(&q->mq_sysfs_lock); return ret; } diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index d4068c1..c56f5a6 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -462,6 +462,9 @@ struct request_queue { struct blk_mq_tag_set *tag_set; struct list_head tag_set_list; + + struct mutex mq_sysfs_lock; + bool mq_sysfs_init_done; }; #define QUEUE_FLAG_QUEUED 1 /* uses generic tag queueing */ -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/