Re: mmotm boot panic bootmem-avoid-dma32-zone-by-default.patch

[Greg Thelen <gthelen@google.com>]

On Fri, Mar 5, 2010 at 10:41 AM, Yinghai Lu <yinghai@kernel.org> wrote:
> On 03/04/2010 09:17 PM, Greg Thelen wrote:
>> On Thu, Mar 4, 2010 at 7:21 PM, Johannes Weiner <hannes@cmpxchg.org> wrote:
>>> On Thu, Mar 04, 2010 at 01:21:41PM -0800, Greg Thelen wrote:
>>>> On several systems I am seeing a boot panic if I use mmotm
>>>> (stamp-2010-03-02-18-38).  If I remove
>>>> bootmem-avoid-dma32-zone-by-default.patch then no panic is seen.  I
>>>> find that:
>>>> * 2.6.33 boots fine.
>>>> * 2.6.33 + mmotm w/o bootmem-avoid-dma32-zone-by-default.patch: boots fine.
>>>> * 2.6.33 + mmotm (including
>>>> bootmem-avoid-dma32-zone-by-default.patch): panics.
> ...
>>
>> Note: mmotm has been recently updated to stamp-2010-03-04-18-05.  I
>> re-tested with 'make defconfig' to confirm the panic with this later
>> mmotm.
>
> please check
>
> [PATCH] early_res: double check with updated goal in alloc_memory_core_early
>
> Johannes Weiner pointed out that new early_res replacement for alloc_bootmem_node
> change the behavoir about goal.
> original bootmem one will try go further regardless of goal.
>
> and it will break his patch about default goal from MAX_DMA to MAX_DMA32...
> also broke uncommon machines with <=16M of memory.
> (really? our x86 kernel still can run on 16M system?)
>
> so try again with update goal.
>
> Reported-by: Greg Thelen <gthelen@google.com>
> Signed-off-by: Yinghai Lu <yinghai@kernel.org>
>
> ---
>  mm/bootmem.c |   28 +++++++++++++++++++++++++---
>  1 file changed, 25 insertions(+), 3 deletions(-)
>
> Index: linux-2.6/mm/bootmem.c
> ===================================================================
> --- linux-2.6.orig/mm/bootmem.c
> +++ linux-2.6/mm/bootmem.c
> @@ -170,6 +170,28 @@ void __init free_bootmem_late(unsigned l
>  }
>
>  #ifdef CONFIG_NO_BOOTMEM
> +static void * __init ___alloc_memory_core_early(pg_data_t *pgdat, u64 size,
> +                                                u64 align, u64 goal, u64 limit)
> +{
> +       void *ptr;
> +       unsigned long end_pfn;
> +
> +       ptr = __alloc_memory_core_early(pgdat->node_id, size, align,
> +                                        goal, limit);
> +       if (ptr)
> +               return ptr;
> +
> +       /* check goal according  */
> +       end_pfn = pgdat->node_start_pfn + pgdat->node_spanned_pages;
> +       if ((end_pfn << PAGE_SHIFT) < (goal + size)) {
> +               goal = pgdat->node_start_pfn << PAGE_SHIFT;
> +               ptr = __alloc_memory_core_early(pgdat->node_id, size, align,
> +                                                goal, limit);
> +       }
> +
> +       return ptr;
> +}
> +
>  static void __init __free_pages_memory(unsigned long start, unsigned long end)
>  {
>        int i;
> @@ -836,7 +858,7 @@ void * __init __alloc_bootmem_node(pg_da
>                return kzalloc_node(size, GFP_NOWAIT, pgdat->node_id);
>
>  #ifdef CONFIG_NO_BOOTMEM
> -       return __alloc_memory_core_early(pgdat->node_id, size, align,
> +       return  ___alloc_memory_core_early(pgdat, size, align,
>                                         goal, -1ULL);
>  #else
>        return ___alloc_bootmem_node(pgdat->bdata, size, align, goal, 0);
> @@ -920,7 +942,7 @@ void * __init __alloc_bootmem_node_nopan
>                return kzalloc_node(size, GFP_NOWAIT, pgdat->node_id);
>
>  #ifdef CONFIG_NO_BOOTMEM
> -       ptr =  __alloc_memory_core_early(pgdat->node_id, size, align,
> +       ptr =  ___alloc_memory_core_early(pgdat, size, align,
>                                                 goal, -1ULL);
>  #else
>        ptr = alloc_arch_preferred_bootmem(pgdat->bdata, size, align, goal, 0);
> @@ -980,7 +1002,7 @@ void * __init __alloc_bootmem_low_node(p
>                return kzalloc_node(size, GFP_NOWAIT, pgdat->node_id);
>
>  #ifdef CONFIG_NO_BOOTMEM
> -       return __alloc_memory_core_early(pgdat->node_id, size, align,
> +       return ___alloc_memory_core_early(pgdat, size, align,
>                                goal, ARCH_LOW_ADDRESS_LIMIT);
>  #else
>        return ___alloc_bootmem_node(pgdat->bdata, size, align,
>

On my 256MB VM, which detected the problem starting this thread, the
"double check with updated goal in alloc_memory_core_early" patch
(above) boots without panic.

My initial impression is that this fixes the reported problem.  Note:
I have not tested to see if any other issues are introduced.

--
Greg

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