[PATCH] reduce size of struct buffer_head on 64bit

[PATCH] reduce size of struct buffer_head on 64bit

Reduce size of buffer_head from 96 to 88 bytes on 64bit architectures by
putting b_count and b_size together.  b_count will still be in the first 16
bytes on 32bit architectures, so 16 byte cacheline machines shouldnt be
affected.

With this change the number of objects per 4kB slab goes up from 40 to 44
on ppc64.

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>