Btrfs: btrfs_check_super_valid: Allow 4096 as stripesize

Older btrfs-progs/mkfs.btrfs sets 4096 as the stripesize. Hence
restricting stripesize to be equal to sectorsize would cause super block
validation to return an error on architectures where PAGE_SIZE is not
equal to 4096.

Hence as a workaround, this commit allows stripesize to be set to 4096
bytes.
Signed-off-by: Chandan Rajendra <chandan@linux.vnet.ibm.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/disk-io.c

@@ -4134,7 +4134,8 @@ static int btrfs_check_super_valid(struct btrfs_fs_info *fs_info,
 		ret = -EINVAL;
 	}
 	if (!is_power_of_2(btrfs_super_stripesize(sb)) ||
-	    btrfs_super_stripesize(sb) != sectorsize) {
+		((btrfs_super_stripesize(sb) != sectorsize) &&
+			(btrfs_super_stripesize(sb) != 4096))) {
 		btrfs_err(fs_info, "invalid stripesize %u",
 		       btrfs_super_stripesize(sb));
 		ret = -EINVAL;