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SubjectRe: No more bits in vm_area_struct's vm_flags.
On Fri, 25 Sep 2009 18:34:56 +1000
Nigel Cunningham <ncunningham@crca.org.au> wrote:

> Hi.
>
> KAMEZAWA Hiroyuki wrote:
> >> I have some code in TuxOnIce that needs a bit too (explicitly mark the
> >> VMA as needing to be atomically copied, for GEM objects), and am not
> >> sure what the canonical way to proceed is. Should a new unsigned long be
> >> added? The difficulty I see with that is that my flag was used in
> >> shmem_file_setup's flags parameter (drm_gem_object_alloc), so that
> >> function would need an extra parameter too..
> >
> > Hmm, how about adding vma->vm_flags2 ?
>
> The difficulty there is that some functions pass these flags as arguments.
>
Ah yes. But I wonder some special flags, which is rarey used, can be moved
to vm_flags2...

For example,

#define VM_SEQ_READ 0x00008000 /* App will access data sequentially */
#define VM_RAND_READ 0x00010000 /* App will not benefit from clustered reads */
are all capsuled under
mm.h
117 #define VM_READHINTMASK (VM_SEQ_READ | VM_RAND_READ)
118 #define VM_ClearReadHint(v) (v)->vm_flags &= ~VM_READHINTMASK
119 #define VM_NormalReadHint(v) (!((v)->vm_flags & VM_READHINTMASK))
120 #define VM_SequentialReadHint(v) ((v)->vm_flags & VM_SEQ_READ)
121 #define VM_RandomReadHint(v) ((v)->vm_flags & VM_RAND_READ)
Or

105 #define VM_PFN_AT_MMAP 0x40000000 /* PFNMAP vma that is fully mapped at mmap time */
is only used under special situation.
etc..

They'll be able to be moved to other(new) flag field, IIUC.

Thanks,
-Kame




> Regards,
>
> Nigel
>
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