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    Subject[06/18] Vcompound: Update page address determination
    Make page_address() correctly determine the address of a potentially
    virtually mapped compound page.

    There are 3 cases to consider:

    1. !HASHED_PAGE_VIRTUAL && !WANT_PAGE_VIRTUAL

    Call vmalloc_address() directly from the page_address function
    defined in mm.h.

    2. HASHED_PAGE_VIRTUAL

    Modify page_address() in highmem.c to call vmalloc_address().

    3. WANT_PAGE_VIRTUAL

    set_page_address() is used to set up the virtual addresses of
    all pages that are part of the virtual compound.

    Cc: apw@shadowen.org
    Signed-off-by: Christoph Lameter <clameter@sgi.com>

    ---
    include/linux/mm.h | 9 ++++++++-
    mm/highmem.c | 10 ++++++++--
    2 files changed, 16 insertions(+), 3 deletions(-)

    Index: linux-2.6/include/linux/mm.h
    ===================================================================
    --- linux-2.6.orig/include/linux/mm.h 2007-10-03 19:39:52.000000000 -0700
    +++ linux-2.6/include/linux/mm.h 2007-10-03 19:40:29.000000000 -0700
    @@ -605,7 +605,14 @@ void page_address_init(void);
    #endif

    #if !defined(HASHED_PAGE_VIRTUAL) && !defined(WANT_PAGE_VIRTUAL)
    -#define page_address(page) lowmem_page_address(page)
    +
    +static inline void *page_address(struct page *page)
    +{
    + if (unlikely(PageVcompound(page)))
    + return vmalloc_address(page);
    + return lowmem_page_address(page);
    +}
    +
    #define set_page_address(page, address) do { } while(0)
    #define page_address_init() do { } while(0)
    #endif
    Index: linux-2.6/mm/highmem.c
    ===================================================================
    --- linux-2.6.orig/mm/highmem.c 2007-10-03 19:39:25.000000000 -0700
    +++ linux-2.6/mm/highmem.c 2007-10-03 19:40:29.000000000 -0700
    @@ -265,8 +265,11 @@ void *page_address(struct page *page)
    void *ret;
    struct page_address_slot *pas;

    - if (!PageHighMem(page))
    + if (!PageHighMem(page)) {
    + if (PageVcompound(page))
    + return vmalloc_address(page);
    return lowmem_page_address(page);
    + }

    pas = page_slot(page);
    ret = NULL;
    @@ -294,7 +297,10 @@ void set_page_address(struct page *page,
    struct page_address_slot *pas;
    struct page_address_map *pam;

    - BUG_ON(!PageHighMem(page));
    + if (!PageHighMem(page)) {
    + BUG_ON(!PageVcompound(page));
    + return;
    + }

    pas = page_slot(page);
    if (virtual) { /* Add */
    --
    -
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