md/raid1-10: add a helper raid1_check_read_range()

	return false;

}

/**

 * raid1_check_read_range() - check a given read range for bad blocks,

 * available read length is returned;

 * @rdev: the rdev to read;

 * @this_sector: read position;

 * @len: read length;

 *

 * helper function for read_balance()

 *

 * 1) If there are no bad blocks in the range, @len is returned;

 * 2) If the range are all bad blocks, 0 is returned;

 * 3) If there are partial bad blocks:

 *  - If the bad block range starts after @this_sector, the length of first

 *  good region is returned;

 *  - If the bad block range starts before @this_sector, 0 is returned and

 *  the @len is updated to the offset into the region before we get to the

 *  good blocks;

 */

static inline int raid1_check_read_range(struct md_rdev *rdev,

					 sector_t this_sector, int *len)

{

	sector_t first_bad;

	int bad_sectors;

	/* no bad block overlap */

	if (!is_badblock(rdev, this_sector, *len, &first_bad, &bad_sectors))

		return *len;

	/*

	 * bad block range starts offset into our range so we can return the

	 * number of sectors before the bad blocks start.

	 */

	if (first_bad > this_sector)

		return first_bad - this_sector;

	/* read range is fully consumed by bad blocks. */

	if (this_sector + *len <= first_bad + bad_sectors)

		return 0;

	/*

	 * final case, bad block range starts before or at the start of our

	 * range but does not cover our entire range so we still return 0 but

	 * update the length with the number of sectors before we get to the

	 * good ones.

	 */

	*len = first_bad + bad_sectors - this_sector;

	return 0;

}