On Wed, Mar 6, 2013 at 2:44 PM, <a...@linux-foundation.org> wrote:
> ------------------------------------------------------
> From: Vineet Gupta <vineet.gup...@synopsys.com>
> Subject: memblock: add assertion for zero allocation alignment
>
> 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 <vgu...@synopsys.com>
> Cc: Yinghai Lu <ying...@kernel.org>
> Cc: Wanpeng Li <liw...@linux.vnet.ibm.com>
> Cc: Ingo Molnar <mi...@kernel.org>
> Acked-by: Tejun Heo <t...@kernel.org>
> Signed-off-by: Andrew Morton <a...@linux-foundation.org>
> ---
>
> mm/memblock.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff -puN mm/memblock.c~memblock-add-assertion-for-zero-allocation-alignment
> mm/memblock.c
> --- a/mm/memblock.c~memblock-add-assertion-for-zero-allocation-alignment
> +++ a/mm/memblock.c
> @@ -771,6 +771,9 @@ static phys_addr_t __init memblock_alloc
> {
> phys_addr_t found;
>
> + if (WARN_ON(!align))
> + align = __alignof__(long long);
> +
> /* align @size to avoid excessive fragmentation on reserved array */
> size = round_up(size, align);
Hi, Peter,
Do you agree that we should check align in round_up()?
Thanks
Yinghai
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