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    SubjectRe: [05/17] vunmap: return page array
    On Wed, 19 Sep 2007 15:15:58 -0700 (PDT)
    Christoph Lameter <clameter@sgi.com> wrote:

    > On Wed, 19 Sep 2007, KAMEZAWA Hiroyuki wrote:
    >
    > > Hmm, I don't like returning array which someone allocated in past and forgot.
    >
    > But that is exactly the point. There is no need to keep track of the
    > information that is of no interest until the disposition of the mapping.
    >
    yes. But I think neat style of this kind function is
    ==
    /* If array != NULL, pointer of unmapped pages are stored in array[] */
    extern int vunmap(const void *addr, struct page **array);
    ==
    But yes, this costs.

    > > And, area->page[] array under vmalloc() is allocated as following (in -rc6-mm1)
    > > ==
    > > if (array_size > PAGE_SIZE) {
    > > pages = __vmalloc_node(array_size, gfp_mask | __GFP_ZERO,
    > > PAGE_KERNEL, node);
    > > area->flags |= VM_VPAGES;
    > > } else {
    > > pages = kmalloc_node(array_size,
    > > (gfp_mask & GFP_RECLAIM_MASK) | __GFP_ZERO,
    > > node);
    > > }
    > > ==
    > > A bit complicating.
    >
    > Not at all. You can pass a __vmalloc'ed entity to vmap if you add VM_VPAGES
    > to the flags passed to it.
    >
    > > At least, please add comments "How to free page-array returned by vummap"
    >
    > But that depends on how the vmap was called. The caller knows what he has
    > done to acquire the memory and therefore also knows how to get rid of it.
    >
    Hm, it seems all your patch are for hiding usage of vmalloc()/vmap().
    If freeing pages[] array is also hidden in your patch's context, no problem.

    Thanks,
    -Kame


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