Fix problem with add a device to a 1.x array created with older mdadm.

When adding new disk to an array, don't reserve so much bitmap
space that the disk cannot store the required data. (Needed when
1.x array was created with older mdadm).

ChangeLog

@@ -1,5 +1,8 @@
 Changes Prior to this release
     -   allow --write-behind to be set for --grow.
+    -   When adding new disk to an array, don't reserve so much bitmap
+        space that the disk cannot store the required data. (Needed when
+	1.x array was created with older mdadm).
 
 Changes Prior to 2.6.2 release
     -   --fail detached and --remove faulty can be used to fail and

super1.c

@@ -917,12 +917,16 @@ static int write_init_super1(struct supertype *st, void *sbv,
 		break;
 	case 1:
 		sb->super_offset = __cpu_to_le64(0);
+		if (4*2 + bm_space + __le64_to_cpu(sb->size) > dsize)
+			bm_space = dsize - __le64_to_cpu(sb->size) - 4*2;
 		sb->data_offset = __cpu_to_le64(bm_space + 4*2);
 		sb->data_size = __cpu_to_le64(dsize - bm_space - 4*2);
 		break;
 	case 2:
 		sb_offset = 4*2;
 		sb->super_offset = __cpu_to_le64(4*2);
+		if (4*2 + 4*2 + bm_space + __le64_to_cpu(sb->size) > dsize)
+			bm_space = dsize - __le64_to_cpu(sb->size) - 4*2 - 4*2;
 		sb->data_offset = __cpu_to_le64(4*2 + 4*2 + bm_space);
 		sb->data_size = __cpu_to_le64(dsize - 4*2 - 4*2 - bm_space );
 		break;