mm/memblock: drop WARN and use SMP_CACHE_BYTES as a default alignment

Don't produce warning and interpret 0 as "default align" equal to
SMP_CACHE_BYTES in case if caller of memblock_alloc_base_nid() doesn't
specify alignment for the block (align == 0).

This is done in preparation of introducing common memblock alloc interface
to make code behavior consistent.  More details are in below thread :

	https://lkml.org/lkml/2013/10/13/117.

Signed-off-by: Grygorii Strashko <[email protected]>
Signed-off-by: Santosh Shilimkar <[email protected]>
Cc: Yinghai Lu <[email protected]>
Cc: Tejun Heo <[email protected]>
Cc: "Rafael J. Wysocki" <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: KAMEZAWA Hiroyuki <[email protected]>
Cc: Konrad Rzeszutek Wilk <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Paul Walmsley <[email protected]>
Cc: Pavel Machek <[email protected]>
Cc: Russell King <[email protected]>
Cc: Tony Lindgren <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

mm/memblock.c

@@ -969,8 +969,8 @@ static phys_addr_t __init memblock_alloc_base_nid(phys_addr_t size,
 {
 	phys_addr_t found;
 
-	if (WARN_ON(!align))
-		align = __alignof__(long long);
+	if (!align)
+		align = SMP_CACHE_BYTES;
 
 	/* align @size to avoid excessive fragmentation on reserved array */
 	size = round_up(size, align);