* Re: Patch "block: destroy bdi before blockdev is unregistered." has been added to the 4.0-stable tree
[not found] <143165628813416@kroah.com>
@ 2015-05-15 7:03 ` Sergey Senozhatsky
2015-05-15 23:16 ` Greg KH
0 siblings, 1 reply; 4+ messages in thread
From: Sergey Senozhatsky @ 2015-05-15 7:03 UTC (permalink / raw)
To: gregkh; +Cc: neilb, a3at.mail, axboe, hch, stable, stable-commits,
linux-kernel
On (05/14/15 19:18), gregkh@linuxfoundation.org wrote:
> 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@vger.kernel.org> know about it.
>
>
Hello Greg,
jfi, I think this commit will WARN_ON(). fixed by https://lkml.org/lkml/2015/5/8/29
(https://lkml.org/lkml/2015/4/28/568)
-ss
> From 6cd18e711dd8075da9d78cfc1239f912ff28968a Mon Sep 17 00:00:00 2001
> From: NeilBrown <neilb@suse.de>
> Date: Mon, 27 Apr 2015 14:12:22 +1000
> Subject: block: destroy bdi before blockdev is unregistered.
>
> From: NeilBrown <neilb@suse.de>
>
> 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@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>
> Signed-off-by: NeilBrown <neilb@suse.de>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> Signed-off-by: Jens Axboe <axboe@fb.com>
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>
> ---
> 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@suse.de are
>
> queue-4.0/block-destroy-bdi-before-blockdev-is-unregistered.patch
> --
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