Re: question about nommu.c

[Paul Mundt <lethal@linux-sh.org>]

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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