Re: [PATCH 2/4] btrfs: replace seed device followed by unmount causes kernel WARNING

[Miao Xie <miaox@cn.fujitsu.com>]

On Mon, 11 Aug 2014 17:42:54 +0800, Anand Jain wrote:
> reproducer:
> mount /dev/sdb /btrfs
> btrfs dev add /dev/sdc /btrfs
> btrfs rep start -B /dev/sdb /dev/sdd /btrfs
> umount /btrfs
> 
> WARNING: CPU: 0 PID: 12661 at fs/btrfs/volumes.c:891 __btrfs_close_devices+0x1b0/0x200 [btrfs]()
> ::
> 
> __btrfs_close_devices()
> ::
>         WARN_ON(fs_devices->open_devices);
> 
> After the seed device has been replaced the new target device
> is no more a seed device. So we need to update the device
> numbers in the fs_devices as pointed by the fs_info.
> 
> Signed-off-by: Anand Jain <anand.jain@oracle.com>
> ---
>  fs/btrfs/volumes.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index 5fd0132..f098ae7 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -1964,7 +1964,13 @@ void btrfs_rm_dev_replace_srcdev(struct btrfs_fs_info *fs_info,
>  
>  	WARN_ON(!mutex_is_locked(&fs_info->fs_devices->device_list_mutex));
>  
> -	fs_devices = fs_info->fs_devices;
> +	/*
> +	 * in case of fs with no seed, srcdev->fs_devices will point
> +	 * to fs_devices of fs_info. However when the dev being replaced is
> +	 * a seed dev it will point to the seed's local fs_devices. In short
> +	 * srcdev will have its correct fs_devices in both the cases.
> +	 */
> +	fs_devices = srcdev->fs_devices;

Reviewed-by: Miao Xie <miaox@cn.fujitsu.com>

>  
>  	list_del_rcu(&srcdev->dev_list);
>  	list_del_rcu(&srcdev->dev_alloc_list);
>