Re: Patch "Btrfs: use down_read_nested to make lockdep silent" has been added to the 4.4-stable tree

[Greg KH <gregkh@linuxfoundation.org>]

On Fri, Aug 04, 2017 at 03:26:10PM -0700, gregkh@linuxfoundation.org wrote:
> 
> This is a note to let you know that I've just added the patch titled
> 
>     Btrfs: use down_read_nested to make lockdep silent
> 
> to the 4.4-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:
>      btrfs-use-down_read_nested-to-make-lockdep-silent.patch
> and it can be found in the queue-4.4 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.

Oops no, this did not apply, somehow I missed that.  If someone wants
this in 4.4, please provide a working backport.

thanks,

greg k-h

> >From foo@baz Fri Aug  4 15:15:51 PDT 2017
> From: Liu Bo <bo.li.liu@oracle.com>
> Date: Wed, 30 Nov 2016 16:11:04 -0800
> Subject: Btrfs: use down_read_nested to make lockdep silent
> 
> From: Liu Bo <bo.li.liu@oracle.com>
> 
> 
> [ Upstream commit e321f8a801d7b4c40da8005257b05b9c2b51b072 ]
> 
> If @block_group is not @used_bg, it'll try to get @used_bg's lock without
> droping @block_group 's lock and lockdep has throwed a scary deadlock warning
> about it.
> Fix it by using down_read_nested.
> 
> Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
> Reviewed-by: David Sterba <dsterba@suse.com>
> Signed-off-by: David Sterba <dsterba@suse.com>
> Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> ---
>  fs/btrfs/extent-tree.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
> index e46e7fbe1b34..14a37ff0b9e3 100644
> --- a/fs/btrfs/extent-tree.c
> +++ b/fs/btrfs/extent-tree.c
> @@ -7401,7 +7401,8 @@ btrfs_lock_cluster(struct btrfs_block_group_cache *block_group,
>  
>  		spin_unlock(&cluster->refill_lock);
>  
> -		down_read(&used_bg->data_rwsem);
> +		/* We should only have one-level nested. */
> +		down_read_nested(&used_bg->data_rwsem, SINGLE_DEPTH_NESTING);
>  
>  		spin_lock(&cluster->refill_lock);
>  		if (used_bg == cluster->block_group)
> -- 
> 2.13.4
> 
> 
> 
> Patches currently in stable-queue which might be from bo.li.liu@oracle.com are
> 
> queue-4.4/btrfs-adjust-outstanding_extents-counter-properly-when-dio-write-is-split.patch
> queue-4.4/btrfs-use-down_read_nested-to-make-lockdep-silent.patch