Re: [PATCH 2/2] btrfs: fix vanished compression property after failed set

[Nikolay Borisov <nborisov@suse.com>]

On 13.03.19 г. 7:36 ч., Anand Jain wrote:
> The compression property resets to NULL, instead of the old value if we
> fail to set the new compression parameter.
> 
> btrfs prop get /btrfs compression
>   compression=lzo
> btrfs prop set /btrfs compression zli
>   ERROR: failed to set compression for /btrfs: Invalid argument
> btrfs prop get /btrfs compression
> 
> This is because the compression property ->validate() is successful for
> 'zli' as the strncmp() used the len passed from the userland.
> 
> Fix it by using the expected string length in strncmp().
> 
> Signed-off-by: Anand Jain <anand.jain@oracle.com>
> ---
>  fs/btrfs/props.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/btrfs/props.c b/fs/btrfs/props.c
> index ef6502a94712..7aa362c2fbcf 100644
> --- a/fs/btrfs/props.c
> +++ b/fs/btrfs/props.c
> @@ -277,11 +277,11 @@ static int prop_compression_validate(struct inode *inode, const char *value,
>  	if (!value)
>  		return 0;
>  
> -	if (!strncmp("lzo", value, len))
> +	if (!strncmp("lzo", value, 3))
>  		return 0;
> -	else if (!strncmp("zlib", value, len))
> +	else if (!strncmp("zlib", value, 4))
>  		return 0;
> -	else if (!strncmp("zstd", value, len))
> +	else if (!strncmp("zstd", value, 4))
>  		return 0;

This also makes the len argument to prop_compression_validate redundant
and should be removed as well.

>  
>  	return -EINVAL;
>