Re: [03/17] is_vmalloc_addr(): Check if an address is within the vmalloc boundaries

[Anton Altaparmakov]

On 19 Sep 2007, at 09:09, David Rientjes wrote:
> On Wed, 19 Sep 2007, Anton Altaparmakov wrote:
> > > > Index: linux-2.6/include/linux/mm.h
> > > > ===================================================================
> > > > --- linux-2.6.orig/include/linux/mm.h	2007-09-17 21:46:06.000000000
> > > > -0700
> > > > +++ linux-2.6/include/linux/mm.h	2007-09-17 23:56:54.000000000  
> > > > -0700
> > > > @@ -1158,6 +1158,14 @@ static inline unsigned long vma_pages(st
> > > > 	return (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
> > > > }
> > > >
> > > > +/* Determine if an address is within the vmalloc range */
> > > > +static inline int is_vmalloc_addr(const void *x)
> > > > +{
> > > > +	unsigned long addr = (unsigned long)x;
> > > > +
> > > > +	return addr >= VMALLOC_START && addr < VMALLOC_END;
> > > > +}
> > >
> > > This breaks on i386 because VMALLOC_END is defined in terms of  
> > > PKMAP_BASE
> > > in the CONFIG_HIGHMEM case.
> >
> > That is incorrect.  This works perfectly on i386 and on ALL  
> > architectures
> > supported by Linux.  A lot of places in the kernel already do this  
> > today
> > (mostly hand coded though, eg XFS and NTFS)...
>
> Hmm, really?
>
> After applying patches 1-3 in this series and compiling on my i386  
> with
> defconfig, I get this:
>
> In file included from include/linux/suspend.h:11,
>                  from arch/i386/kernel/asm-offsets.c:11:
> include/linux/mm.h: In function 'is_vmalloc_addr':
> include/linux/mm.h:1166: error: 'PKMAP_BASE' undeclared (first use  
> in this function)
> include/linux/mm.h:1166: error: (Each undeclared identifier is  
> reported only once
> include/linux/mm.h:1166: error: for each function it appears in.)
>
> so I don't know what you're talking about.

Just a compile failure not inherently broken!

Add:

#include <linux/highmem.h> to the top of linux/mm.h and it should  
compile just fine.

Although it may cause a problem as highmem.h also includes mm.h so a  
bit of trickery may be needed to get it to compile...

I suspect that is_vmalloc_addr() should not be in linux/mm.h at all  
and should be in linux/vmalloc.h instead and vmalloc.h should include  
linux/highmem.h.  That would be more sensible than sticking a vmalloc  
related function into linux/mm.h where it does not belong...

Best regards,

	Anton
--
Anton Altaparmakov <aia21 at cam.ac.uk> (replace at with @)
Unix Support, Computing Service, University of Cambridge, CB2 3QH, UK
Linux NTFS maintainer, http://www.linux-ntfs.org/


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