From: NeilBrown <neilb@suse.de>

Some devices (dasd!) have 4K sectors, so metadata must be
aligned on 4K boundaries.
superblock already is, but bitmap might not be.  So force the
bitmap to a 4K boundary for v1.x metadata
It already is for v1.1 and v1.2, so just fix for v1.0

(Note that v0.90 already uses a 4K boundary too).

Signed-off-by: NeilBrown <neilb@suse.de>

diff --git a/super1.c b/super1.c
index fee22a9..66e9771 100644
--- a/super1.c
+++ b/super1.c
@@ -1437,11 +1437,6 @@ add_internal_bitmap1(struct supertype *st,
 			 */
 			offset = 0;
 			room = choose_bm_space(__le64_to_cpu(sb->size));
-			if (room == 4*2) {
-				/* make it 3K after the superblock */
-				room = 3*2;
-				offset = 2;
-			}
 		} else {
 			room = __le64_to_cpu(sb->super_offset)
 				- __le64_to_cpu(sb->data_offset)
@@ -1498,8 +1493,9 @@ add_internal_bitmap1(struct supertype *st,
 
 	if (offset == 0) {
 		bits = (size*512) / chunk + 1;
-		room = ((bits+7)/8 + sizeof(bitmap_super_t) +511)/512;
-		offset = -room;
+		/* Align bitmap space to a 4K boundary as some devices need that */
+		room = ((bits+7)/8 + sizeof(bitmap_super_t) +4095)/4096;
+		offset = -room * 8; /* *8 to convert 4K blocks to sectors */
 	}
 
 	sb->bitmap_offset = __cpu_to_le32(offset);