Re: [PATCH 4/4] btrfs: update sprout seed pointer when seed fs is relinquished

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

On Mon, 11 Aug 2014 17:42:56 +0800, Anand Jain wrote:
> We are not updating sprout fs seed pointer when all seed device
> is replaced. This patch will check if all seed device has been
> replaced and then update the sprout pointer accordingly.
> 
> Same reproducer as in the previous patch would apply here.
> And notice that btrfs_close_device will check if seed fs is
> present and spits out the error with out this patch.
> 
> int btrfs_close_devices(struct btrfs_fs_devices *fs_devices)
> {
> ::
>                 seed_devices = fs_devices->seed;
> ::
>         while (seed_devices) {
>                 fs_devices = seed_devices;
>                 seed_devices = fs_devices->seed;
>                 __btrfs_close_devices(fs_devices);
>                 free_fs_devices(fs_devices);
>         }
> 
> Signed-off-by: Anand Jain <anand.jain@oracle.com>
> ---
>  fs/btrfs/volumes.c | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
> 
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index f098ae7..bfdc11f 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -1992,6 +1992,25 @@ void btrfs_rm_dev_replace_srcdev(struct btrfs_fs_info *fs_info,
>  			btrfs_scratch_superblock(srcdev);
>  	}
>  
> +	/* unless fs_devices is seed fs, num_devices shouldn't go
> +	 * zero
> +	 */

According to coding style, the preferred style for multi-line comments is(except files in net
subsystem):

/*
 * <comment>
 */

> +	BUG_ON(!fs_devices->num_devices && !fs_devices->seeding);

Use ASSERT?

> +	/* if this is no devs we rather delete the fs_devices */
> +	if (!fs_devices->num_devices) {
> +		struct btrfs_fs_devices *tmp_fs_devices;
> +
> +		tmp_fs_devices = fs_info->fs_devices;
> +		while (tmp_fs_devices) {
> +			if (tmp_fs_devices->seed == fs_devices) {
> +				tmp_fs_devices->seed = fs_devices->seed;
> +				break;
> +			}
> +			tmp_fs_devices = tmp_fs_devices->seed;
> +		}
> +		fs_devices->seed = NULL;

Why not free fs_devices like btrfs_rm_device?

The other is OK.

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

> +	}
>  	call_rcu(&srcdev->rcu, free_device);
>  }
>  
>