question about nommu.c

question about nommu.c

[Julia Lawall]

The function vmalloc_user in the file mm/nommu.c contains the following 
code:

struct vm_area_struct *vma;
...
if (vma)
        vma->vm_flags |= VM_USERMAP;

The constant VM_USERMAP, however, is elsewhere used in a structure of type 
vm_struct, not vm_area_struct.  Furthermore, the value of VM_USERMAP is 8, 
which is the same as the value of VM_SHARED (define in mm.h), which is 
elsewhere used with a vm_area_struct structure.  Is this occurrence of 
VM_USERMAP correct?  Or should it be VM_SHARED?  Or should it be something 
else?

julia


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Re: question about nommu.c

[Paul Mundt]

On Thu, Aug 13, 2009 at 09:41:38PM +0200, Julia Lawall wrote:
> The function vmalloc_user in the file mm/nommu.c contains the following 
> code:
> 
> struct vm_area_struct *vma;
> ...
> if (vma)
>         vma->vm_flags |= VM_USERMAP;
> 
> The constant VM_USERMAP, however, is elsewhere used in a structure of type 
> vm_struct, not vm_area_struct.  Furthermore, the value of VM_USERMAP is 8, 
> which is the same as the value of VM_SHARED (define in mm.h), which is 
> elsewhere used with a vm_area_struct structure.  Is this occurrence of 
> VM_USERMAP correct?  Or should it be VM_SHARED?  Or should it be something 
> else?
> 
Yes, this is currently broken, albeit generally harmless. I've been
working on cleaning this up, but have not gotten around to posting
patches yet.

Part of this requires building on top of the infrastructure we have in
place with the vm_regions to layer a proper vmap implementation on top
of, which should in turn restore some meaning to the vmlist and permit
struct vm_struct to be used on nommu properly.

At the moment this is not a big problem as it doesn't really impact
anything, it's more regarding future directions for the nommu memory
management code.

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Re: question about nommu.c

[Julia Lawall]

On Fri, 14 Aug 2009, Paul Mundt wrote:

> On Thu, Aug 13, 2009 at 09:41:38PM +0200, Julia Lawall wrote:
> > The function vmalloc_user in the file mm/nommu.c contains the following 
> > code:
> > 
> > struct vm_area_struct *vma;
> > ...
> > if (vma)
> >         vma->vm_flags |= VM_USERMAP;
> > 
> > The constant VM_USERMAP, however, is elsewhere used in a structure of type 
> > vm_struct, not vm_area_struct.  Furthermore, the value of VM_USERMAP is 8, 
> > which is the same as the value of VM_SHARED (define in mm.h), which is 
> > elsewhere used with a vm_area_struct structure.  Is this occurrence of 
> > VM_USERMAP correct?  Or should it be VM_SHARED?  Or should it be something 
> > else?
> > 
> Yes, this is currently broken, albeit generally harmless. I've been
> working on cleaning this up, but have not gotten around to posting
> patches yet.
> 
> Part of this requires building on top of the infrastructure we have in
> place with the vm_regions to layer a proper vmap implementation on top
> of, which should in turn restore some meaning to the vmlist and permit
> struct vm_struct to be used on nommu properly.
> 
> At the moment this is not a big problem as it doesn't really impact
> anything, it's more regarding future directions for the nommu memory
> management code.

OK, perhaps I should just let you clean it up in a more general way then.

julia

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