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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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