Re: No more bits in vm_area_struct's vm_flags.

[KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>]

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
> 
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to majordomo@kvack.org.  For more info on Linux MM,
> see: http://www.linux-mm.org/ .
> Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
> 

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>