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    SubjectRe: [patch 3/3] mm: fault handler to replace nopage and populate
    On Tue, 10 Oct 2006 14:13:27 +0200
    Nick Piggin <npiggin@suse.de> wrote:

    > On Tue, Oct 10, 2006 at 01:10:03PM +0100, Christoph Hellwig wrote:
    > > On Sat, Oct 07, 2006 at 03:06:32PM +0200, Nick Piggin wrote:
    > > > +/*
    > > > + * fault_data is filled in the the pagefault handler and passed to the
    > > > + * vma's ->fault function. That function is responsible for filling in
    > > > + * 'type', which is the type of fault if a page is returned, or the type
    > > > + * of error if NULL is returned.
    > > > + */
    > > > +struct fault_data {
    > > > + struct vm_area_struct *vma;
    > > > + unsigned long address;
    > > > + pgoff_t pgoff;
    > > > + unsigned int flags;
    > > > +
    > > > + int type;
    > > > +};
    > > >
    > > > /*
    > > > * These are the virtual MM functions - opening of an area, closing and
    > > > @@ -203,6 +221,7 @@ extern pgprot_t protection_map[16];
    > > > struct vm_operations_struct {
    > > > void (*open)(struct vm_area_struct * area);
    > > > void (*close)(struct vm_area_struct * area);
    > > > + struct page * (*fault)(struct fault_data * data);
    > >
    > > Please pass the vma as an explicit first argument so that all vm_operations
    > > operate on a vma. It's also much cleaner to have the separate between the
    > > the object operated on (the vma) and all the fault details (struct fault_data).
    >
    > Hmm... I agree it is more consistent, but OTOH if we're passing a
    > structure I thought it may as well just go in there. But I will
    > change unless anyone comes up with an objection.

    I'd agree that it's more attractive to have the vma* in the argument list,
    but it presumably adds runtime cost: cycles and stack depth. I don't how
    much though.
    -
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