Re: doubt about VMA struct

["pradeep singh" <2500.pradeep@xxxxxxxxx>]

On 3/20/07, sandeep lahane <sandeep.lahane@xxxxxxxxx> wrote:
> On 3/20/07, pradeep singh <2500.pradeep@xxxxxxxxx> wrote:
> > Hi all,
> >
> > All questions are related to linux-2.6.20.1.
> >
> > file linux/mm.h has VMA struct declaration as -
> >
> > struct vm_area_struct {
> >    ...
> >
> >   struct vm_operations_struct *vm_ops;
> >    ...
> >
> > }
> >
> > vma_ops is the pointer to the operations related to this VMA struct
> > for our process address space(i.e mm_struct) AFAIK.
> >
> > My question is declaration of the struct vm_operations_struct in the
> > same file have some interesting members like
> >    - open
> >    - close
> >    - nopage  etc.
> > since there is an open and a close related to every VMA struct for a
> > process address space, does this means vm_area_struct for a process's
> > address space is treated like a file?( in terms with the philosophy of
> > almost everything is file :) ) .
> >
> > Does it means accessing a virtual address space for a process is not
> > allowed if open fails or is not allowed?( suppose i do that
> > delibarately in my module ).
> >
> > What if a open succeeds for a vma struct but close fails?
> >
> > Am i missing something with the concept of "everything is file" ?
> >
> > Thank you
> >
> > --psr
> >
> >
> > --
> > play the game
> >
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> >
>
>
> > since there is an open and a close related to every VMA struct for a
> > process address space, does this means vm_area_struct for a process's
> > address space is treated like a file?( in terms with the philosophy of
> > almost everything is file :) ) .
>
> Open and close are called when a region is created and deleted respectively.
> no_page is used during page faults for locating the pages and
> allocating it if needed etc.

Ok got it.

> > Does it means accessing a virtual address space for a process is not
> > allowed if open fails or is not allowed?( suppose i do that
> > delibarately in my module ).
>
> if open fails then it should mean that the region is not created how
> would you access it then?

So, another question who defines these functions?
Broadly speaking ,Is it the job of the device driver writer?
I think no and yes :(
> IMHO 'everything is file' doesn't apply here.

yes agreed but that was just an inquisitive query :-).

Thank you

--psr
> --
>
> Regards,
> Sandeep.


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play the game

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