dm: publish array_too_big

Move array_too_big to include/linux/device-mapper.h because it is
used by targets.

Remove the test from dm-raid1 as the number of mirror legs is limited
such that it can never fail. (Even for stripes it seems rather
unlikely.)

Signed-off-by: Mikulas Patocka <[e-mail]>
Signed-off-by: Alasdair G Kergon <[e-mail]>

drivers/md/dm-raid1.c

···
 	size_t len;
 	struct mirror_set *ms = NULL;
 
-	if (array_too_big(sizeof(*ms), sizeof(ms->mirror[0]), nr_mirrors))
-		return NULL;
-
 	len = sizeof(*ms) + (sizeof(ms->mirror[0]) * nr_mirrors);
 
 	ms = kzalloc(len, GFP_KERNEL);

drivers/md/dm-stripe.c

···
 {
 	size_t len;
 
-	if (array_too_big(sizeof(struct stripe_c), sizeof(struct stripe),
-			  stripes))
+	if (dm_array_too_big(sizeof(struct stripe_c), sizeof(struct stripe),
+			     stripes))
 		return NULL;
 
 	len = sizeof(struct stripe_c) + (sizeof(struct stripe) * stripes);

drivers/md/dm.h

···
 int dm_target_iterate(void (*iter_func)(struct target_type *tt,
 					void *param), void *param);
 
-/*-----------------------------------------------------------------
- * Useful inlines.
- *---------------------------------------------------------------*/
-static inline int array_too_big(unsigned long fixed, unsigned long obj,
-				unsigned long num)
-{
-	return (num > (ULONG_MAX - fixed) / obj);
-}
-
 int dm_split_args(int *argc, char ***argvp, char *input);
 
 /*

include/linux/device-mapper.h

···
  */
 #define dm_round_up(n, sz) (dm_div_up((n), (sz)) * (sz))
 
+#define dm_array_too_big(fixed, obj, num) \
+	((num) > (UINT_MAX - (fixed)) / (obj))
+
 static inline sector_t to_sector(unsigned long n)
 {
 	return (n >> SECTOR_SHIFT);