md/dm-raid: remove max_write_behind setting limit

The comments said 'vaule in kB', while the value actually means the
number of write_behind IOs. And since md-bitmap will automatically
adjust the value to max COUNTER_MAX / 2, there is no need to fail
early.

Also move some macros that is only used md-bitmap.c.

Link: https://lore.kernel.org/linux-raid/20250524061320.370630-15-yukuai1@huaweicloud.com
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Xiao Ni <xni@redhat.com>

Author: YuKuai-huawei

drivers/md/dm-raid.c

@@ -1356,11 +1356,7 @@ static int parse_raid_params(struct raid_set *rs, struct dm_arg_set *as,
 				return -EINVAL;
 			}
 
-			/*
-			 * In device-mapper, we specify things in sectors, but
-			 * MD records this value in kB
-			 */
-			if (value < 0 || value / 2 > COUNTER_MAX) {
+			if (value < 0) {
 				rs->ti->error = "Max write-behind limit out of range";
 				return -EINVAL;
 			}

drivers/md/md-bitmap.c

@@ -105,9 +105,19 @@
  *
  */
 
+typedef __u16 bitmap_counter_t;
+
 #define PAGE_BITS (PAGE_SIZE << 3)
 #define PAGE_BIT_SHIFT (PAGE_SHIFT + 3)
 
+#define COUNTER_BITS 16
+#define COUNTER_BIT_SHIFT 4
+#define COUNTER_BYTE_SHIFT (COUNTER_BIT_SHIFT - 3)
+
+#define NEEDED_MASK ((bitmap_counter_t) (1 << (COUNTER_BITS - 1)))
+#define RESYNC_MASK ((bitmap_counter_t) (1 << (COUNTER_BITS - 2)))
+#define COUNTER_MAX ((bitmap_counter_t) RESYNC_MASK - 1)
+
 #define NEEDED(x) (((bitmap_counter_t) x) & NEEDED_MASK)
 #define RESYNC(x) (((bitmap_counter_t) x) & RESYNC_MASK)
 #define COUNTER(x) (((bitmap_counter_t) x) & COUNTER_MAX)

drivers/md/md-bitmap.h

@@ -9,15 +9,6 @@
 
 #define BITMAP_MAGIC 0x6d746962
 
-typedef __u16 bitmap_counter_t;
-#define COUNTER_BITS 16
-#define COUNTER_BIT_SHIFT 4
-#define COUNTER_BYTE_SHIFT (COUNTER_BIT_SHIFT - 3)
-
-#define NEEDED_MASK ((bitmap_counter_t) (1 << (COUNTER_BITS - 1)))
-#define RESYNC_MASK ((bitmap_counter_t) (1 << (COUNTER_BITS - 2)))
-#define COUNTER_MAX ((bitmap_counter_t) RESYNC_MASK - 1)
-
 /* use these for bitmap->flags and bitmap->sb->state bit-fields */
 enum bitmap_state {
 	BITMAP_STALE	   = 1,  /* the bitmap file is out of date or had -EIO */