Re: [PATCH -next 2/2] bcache: Use max_t() when comparing different types

[Joe Perches <joe@perches.com>]

On Wed, 2014-01-15 at 10:06 +0100, Geert Uytterhoeven wrote:
> drivers/md/bcache/btree.c: In function ‘insert_u64s_remaining’:
> drivers/md/bcache/btree.c:1816: warning: comparison of distinct pointer types lacks a cast
[]
> diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
[]
> @@ -1813,7 +1813,7 @@ static size_t insert_u64s_remaining(struct btree *b)
>  	if (b->keys.ops->is_extents)
>  		ret -= KEY_MAX_U64S;
>  
> -	return max(ret, 0L);
> +	return max_t(ssize_t, ret, 0L);

why not
	return max(ret, 0);

I think it odd that:

drivers/md/bcache/bset.h:static inline size_t bch_btree_keys_u64s_remaining(struct btree_keys *b)

and:

static size_t insert_u64s_remaining(struct btree *b)
{
	ssize_t ret = bch_btree_keys_u64s_remaining(&b->keys);

	/*
	 * Might land in the middle of an existing extent and have to split it
	 */
	if (b->keys.ops->is_extents)
		ret -= KEY_MAX_U64S;

	return max(ret, 0L);
}

so the only use of that size_t inline is cast to ssize_t