Re: [PATCH v9 1/3] btrfs: add btrfs_strmatch helper

[David Sterba <dsterba@suse.cz>]

On Thu, Oct 22, 2020 at 03:43:35PM +0800, Anand Jain wrote:
> Add a generic helper to match the golden-string in the given-string,
> and ignore the leading and trailing whitespaces if any.
> 
> Signed-off-by: Anand Jain <anand.jain@oracle.com>
> Suggested-by: David Sterba <dsterba@suse.com>
> ---
> v9: use Josef suggested C coding style, using single if statement.
> v5: born
> 
>  fs/btrfs/sysfs.c | 20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)
> 
> diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
> index 8424f5d0e5ed..5ea262d289c6 100644
> --- a/fs/btrfs/sysfs.c
> +++ b/fs/btrfs/sysfs.c
> @@ -863,6 +863,26 @@ static ssize_t btrfs_generation_show(struct kobject *kobj,
>  }
>  BTRFS_ATTR(, generation, btrfs_generation_show);
>  
> +/*
> + * Match the %golden in the %given. Ignore the leading and trailing whitespaces
> + * if any.
> + */
> +static int btrfs_strmatch(const char *given, const char *golden)
> +{
> +	size_t len = strlen(golden);
> +	char *stripped;
> +
> +	/* strip leading whitespace */

This is confusing as it's not stripping the space but merely skipping
it.  The arguments are not changed so you also don't need the separate
variable and just update 'given'.

> +	stripped = skip_spaces(given);
> +
> +	/* strip trailing whitespace */
> +	if ((strncmp(stripped, golden, len) == 0) &&
> +	    (strlen(skip_spaces(stripped + len)) == 0))
> +		return 0;

This a bit hard to read but ok, essentially we can do the string
comparison in a loop or use the library functions.

> +
> +	return -EINVAL;

This does not make sense as it's an error code while the function is a
predicate, without error states.

> +}
> +
>  static const struct attribute *btrfs_attrs[] = {
>  	BTRFS_ATTR_PTR(, label),
>  	BTRFS_ATTR_PTR(, nodesize),
> -- 
> 2.25.1