This is a note to let you know that I've just added the patch titled
block: destroy bdi before blockdev is unregistered.
to the 4.0-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
block-destroy-bdi-before-blockdev-is-unregistered.patch
and it can be found in the queue-4.0 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 6cd18e711dd8075da9d78cfc1239f912ff28968a Mon Sep 17 00:00:00 2001
From: NeilBrown <neilb@xxxxxxx>
Date: Mon, 27 Apr 2015 14:12:22 +1000
Subject: block: destroy bdi before blockdev is unregistered.
From: NeilBrown <neilb@xxxxxxx>
commit 6cd18e711dd8075da9d78cfc1239f912ff28968a upstream.
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@xxxxxx>
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@xxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: NeilBrown <neilb@xxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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(-)
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -552,6 +552,8 @@ void blk_cleanup_queue(struct request_qu
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);
}
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -522,8 +522,6 @@ static void blk_release_queue(struct kob
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);
}
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -1672,8 +1672,8 @@ 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);
--- 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);
}
Patches currently in stable-queue which might be from neilb@xxxxxxx are
queue-4.0/block-destroy-bdi-before-blockdev-is-unregistered.patch
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