Re: [PATCH v2 16/22] ARM: mm: cleanup checks for membank overlapwith vmalloc area

[Cyril Chemparathy]

On 8/12/2012 12:36 AM, Nicolas Pitre wrote:
> On Fri, 10 Aug 2012, Cyril Chemparathy wrote:
>
> > On Keystone platforms, physical memory is entirely outside the 32-bit
> > addressible range.  Therefore, the (bank->start > ULONG_MAX) check below marks
> > the entire system memory as highmem, and this causes unpleasentness all over.
> >
> > This patch eliminates the extra bank start check (against ULONG_MAX) by
> > checking bank->start against the physical address corresponding to vmalloc_min
> > instead.
> >
> > In the process, this patch also cleans up parts of the highmem sanity check
> > code by removing what has now become a redundant check for banks that entirely
> > overlap with the vmalloc range.
>
> Are you sure of this?  The code that you removed not only checks for
> banks that fall into the vmalloc area, but it also skipp them.  This is
> now lost.

I almost missed out on this email...

The check is not quite lost, we still have the following in the 
!CONFIG_HIGHMEM block:

	if (highmem) {
		printk(...);
		continue;
	}

The change is that highmem is now set outside the #ifdef when 
(bank->start >= vmalloc_limit), and therefore the check is truly redundant.

> > Signed-off-by: Cyril Chemparathy <cyril@xxxxxx>
> > Signed-off-by: Vitaly Andrianov <vitalya@xxxxxx>
> > ---
> >   arch/arm/mm/mmu.c |   19 +------------------
> >   1 file changed, 1 insertion(+), 18 deletions(-)
> >
> > diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
> > index f764c03..3d685c6 100644
> > --- a/arch/arm/mm/mmu.c
> > +++ b/arch/arm/mm/mmu.c
> > @@ -901,15 +901,12 @@ void __init sanity_check_meminfo(void)
> >   		struct membank *bank = &meminfo.bank[j];
> >   		*bank = meminfo.bank[i];
> >
> > -		if (bank->start > ULONG_MAX)
> > -			highmem = 1;
> > -
> > -#ifdef CONFIG_HIGHMEM
> >   		if (bank->start >= vmalloc_limit)
> >   			highmem = 1;
> >
> >   		bank->highmem = highmem;
> >
> > +#ifdef CONFIG_HIGHMEM
> >   		/*
> >   		 * Split those memory banks which are partially overlapping
> >   		 * the vmalloc area greatly simplifying things later.
> > @@ -932,8 +929,6 @@ void __init sanity_check_meminfo(void)
> >   			bank->size = vmalloc_limit - bank->start;
> >   		}
> >   #else
> > -		bank->highmem = highmem;
> > -
> >   		/*
> >   		 * Highmem banks not allowed with !CONFIG_HIGHMEM.
> >   		 */
> > @@ -946,18 +941,6 @@ void __init sanity_check_meminfo(void)
> >   		}
> >
> >   		/*
> > -		 * Check whether this memory bank would entirely overlap
> > -		 * the vmalloc area.
> > -		 */
> > -		if (bank->start >= vmalloc_limit) {
> > -			printk(KERN_NOTICE "Ignoring RAM at %.8llx-%.8llx "
> > -			       "(vmalloc region overlap).\n",
> > -			       (unsigned long long)bank->start,
> > -			       (unsigned long long)bank->start + bank->size - 1);
> > -			continue;
> > -		}
> > -
> > -		/*
> >   		 * Check whether this memory bank would partially overlap
> >   		 * the vmalloc area.
> >   		 */
> > --
> > 1.7.9.5

--
Thanks
- Cyril
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