Re: [PATCH 1/2 v2] btrfs: label should not contain return char

[David Sterba <dsterba@suse.cz>]

On Tue, May 20, 2014 at 02:36:48PM +0800, Anand Jain wrote:
> From: Anand Jain <Anand.Jain@oracle.com>
> 
> generally if you use
>   echo "test" > /sys/fs/btrfs/<fsid>/label
> it would introduce return char at the end and it can not
> be part of the label. The correct command is
>   echo -n "test" > /sys/fs/btrfs/<fsid>/label
> 
> This patch will check for this user error
> 
> Signed-off-by: Anand Jain <Anand.Jain@oracle.com>
> ---
>  v2: accepts review comments. Thanks Eric and Roman
> 
>  fs/btrfs/sysfs.c |   20 +++++++++++++++++---
>  1 files changed, 17 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
> index c5eb214..ca63fcd 100644
> --- a/fs/btrfs/sysfs.c
> +++ b/fs/btrfs/sysfs.c
> @@ -373,22 +373,36 @@ static ssize_t btrfs_label_store(struct kobject *kobj,
>  	struct btrfs_trans_handle *trans;
>  	struct btrfs_root *root = fs_info->fs_root;
>  	int ret;
> +	char *label;
> +	char *pos;
>  
> -	if (len >= BTRFS_LABEL_SIZE) {
> +	label = kzalloc(len, GFP_NOFS);

You can avoid allocating the buffer entirely:

- search for '\n', if found, use only that amount of bytes
- check for maximum size, copy to label if ok