From 6cd18e711dd8075da9d78cfc1239f912ff28968a Mon Sep 17 00:00:00 2001
From: NeilBrown <neilb@suse.de>
Date: Mon, 27 Apr 2015 14:12:22 +1000
Subject: [PATCH] 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 <hch@lst.de>
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 <a3at.mail@gmail.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: stable@vger.kernel.org (v4.0)
Signed-off-by: NeilBrown <neilb@suse.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>
---
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 fd154b94447a..7871603f0a29 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 faaf36ade7eb..2b8fd302f677 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 ae3fcb4199e9..d7173cb1ea76 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 e6178787ce3d..e47d1dd046da 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -4754,12 +4754,12 @@ 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);
}