>From 7056096317825dbe582d005385bc4077ecb62c76 Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Mon, 27 Apr 2015 04:12:22 +1000 Subject: [PATCH 2/2] block: destroy bdi before blockdev is unregistered. Because of the peculiar way that md devices are created (automatically when the device node is opened), a new device can be created and registered immediately after the blk_unregister_region(disk_devt(disk), disk->minors); call in del_gendisk(). Therefore it is important that all visible artifacts of the previous device are removed before this call. In particular, the 'bdi'. Since: commit c4db59d31e39ea067c32163ac961e9c80198fd37 Author: Christoph Hellwig fs: don't reassign dirty inodes to default_backing_dev_info moved the device_unregister(bdi->dev); call from bdi_unregister() to bdi_destroy() it has been quite easy to lose a race and have a new (e.g.) "md127" be created after the blk_unregister_region() call and before bdi_destroy() is ultimately called by the final 'put_disk', which must come after del_gendisk(). The new device finds that the bdi name is already registered in sysfs and complains > [ 9627.630029] WARNING: CPU: 18 PID: 3330 at fs/sysfs/dir.c:31 sysfs_warn_dup+0x5a/0x70() > [ 9627.630032] sysfs: cannot create duplicate filename '/devices/virtual/bdi/9:127' We can fix this by moving the bdi_destroy() call out of blk_release_queue() (which can happen very late when a refcount reaches zero) and into blk_cleanup_queue() - which happens exactly when the md device driver calls it. Then it is only necessary for md to call blk_cleanup_queue() before del_gendisk(). As loop.c devices are also created on demand by opening the device node, we make the same change there. Fixes: c4db59d31e39ea067c32163ac961e9c80198fd37 Reported-by: Azat Khuzhin Cc: Christoph Hellwig Cc: stable@vger.kernel.org (v4.0) Signed-off-by: NeilBrown Reviewed-by: Christoph Hellwig Signed-off-by: Jens Axboe --- block/blk-core.c | 2 ++ block/blk-sysfs.c | 2 -- drivers/block/loop.c | 2 +- drivers/md/md.c | 4 ++-- 4 files changed, 5 insertions(+), 5 deletions(-) diff --git a/block/blk-core.c b/block/blk-core.c index fd154b9..7871603 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -552,6 +552,8 @@ void blk_cleanup_queue(struct request_queue *q) q->queue_lock = &q->__queue_lock; spin_unlock_irq(lock); + bdi_destroy(&q->backing_dev_info); + /* @q is and will stay empty, shutdown and put */ blk_put_queue(q); } diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c index faaf36a..2b8fd30 100644 --- a/block/blk-sysfs.c +++ b/block/blk-sysfs.c @@ -522,8 +522,6 @@ static void blk_release_queue(struct kobject *kobj) blk_trace_shutdown(q); - bdi_destroy(&q->backing_dev_info); - ida_simple_remove(&blk_queue_ida, q->id); call_rcu(&q->rcu_head, blk_free_queue_rcu); } diff --git a/drivers/block/loop.c b/drivers/block/loop.c index ae3fcb4..d7173cb 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -1620,8 +1620,8 @@ out: static void loop_remove(struct loop_device *lo) { - del_gendisk(lo->lo_disk); blk_cleanup_queue(lo->lo_queue); + del_gendisk(lo->lo_disk); blk_mq_free_tag_set(&lo->tag_set); put_disk(lo->lo_disk); kfree(lo); diff --git a/drivers/md/md.c b/drivers/md/md.c index d4f31e1..593a024 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -4818,12 +4818,12 @@ static void md_free(struct kobject *ko) if (mddev->sysfs_state) sysfs_put(mddev->sysfs_state); + if (mddev->queue) + blk_cleanup_queue(mddev->queue); if (mddev->gendisk) { del_gendisk(mddev->gendisk); put_disk(mddev->gendisk); } - if (mddev->queue) - blk_cleanup_queue(mddev->queue); kfree(mddev); } -- 2.4.0