[PATCH v2 1/2] memblock: add assertion for zero allocation alignment

From: Vineet Gupta
Date: Thu Feb 21 2013 - 15:10:50 EST

This came to light when calling memblock allocator from arc port (for
copying flattended DT). If a "0" alignment is passed, the allocator
round_up() call incorrectly rounds up the size to 0.

round_up(num, alignto) => ((num - 1) | (alignto -1)) + 1

While the obvious allocation failure causes kernel to panic, it is
better to warn the caller to fix the code.

Tejun suggested that instead of BUG_ON(!align) - which might be
ineffective due to pending console init and such, it is better to
WARN_ON, and continue the boot with a reasonable default align.

Caller passing @size need not be handled similarly as the subsequent
panic will indicate that anyhow.

Signed-off-by: Vineet Gupta <vgupta@xxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Yinghai Lu <yinghai@xxxxxxxxxx>
Cc: Wanpeng Li <liwanp@xxxxxxxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: linux-mm@xxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
mm/memblock.c | 3 +++
1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/mm/memblock.c b/mm/memblock.c
index 1bcd9b9..f3804bd 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -824,6 +824,9 @@ static phys_addr_t __init memblock_alloc_base_nid(phys_addr_t size,
/* align @size to avoid excessive fragmentation on reserved array */
size = round_up(size, align);

+ if (WARN_ON(!align))
+ align = __alignof__(long long);
found = memblock_find_in_range_node(0, max_addr, size, align, nid);
if (found && !memblock_reserve(found, size))
return found;

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