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

[Yinghai Lu]

On Thu, Feb 21, 2013 at 12:10 PM, Vineet Gupta
<Vineet.Gupta1@xxxxxxxxxxxx> wrote:
> 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);
> +

the checking should be put before round_up?

>         found = memblock_find_in_range_node(0, max_addr, size, align, nid);
>         if (found && !memblock_reserve(found, size))
>                 return found;
> --
> 1.7.4.1
>
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