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    Subject[patch 03/10] SLUB: Do not use page->mapping
    After moving the lockless_freelist to kmem_cache_cpu we no longer need
    page->lockless_freelist. Restructure the use of the struct page fields in
    such a way that we never touch the mapping field.

    This is turn allows us to remove the special casing of SLUB when determining
    the mapping of a page (needed for corner cases of virtual caches machines that
    need to flush caches of processors mapping a page).

    Signed-off-by: Christoph Lameter <clameter@sgi.com>

    ---
    include/linux/mm.h | 4 ----
    include/linux/mm_types.h | 9 ++-------
    mm/slub.c | 2 --
    3 files changed, 2 insertions(+), 13 deletions(-)

    Index: linux-2.6.22-rc6-mm1/include/linux/mm.h
    ===================================================================
    --- linux-2.6.22-rc6-mm1.orig/include/linux/mm.h 2007-07-05 19:05:02.000000000 -0700
    +++ linux-2.6.22-rc6-mm1/include/linux/mm.h 2007-07-05 19:05:24.000000000 -0700
    @@ -632,10 +632,6 @@ static inline struct address_space *page
    VM_BUG_ON(PageSlab(page));
    if (unlikely(PageSwapCache(page)))
    mapping = &swapper_space;
    -#ifdef CONFIG_SLUB
    - else if (unlikely(PageSlab(page)))
    - mapping = NULL;
    -#endif
    else if (unlikely((unsigned long)mapping & PAGE_MAPPING_ANON))
    mapping = NULL;
    return mapping;
    Index: linux-2.6.22-rc6-mm1/include/linux/mm_types.h
    ===================================================================
    --- linux-2.6.22-rc6-mm1.orig/include/linux/mm_types.h 2007-07-05 19:00:19.000000000 -0700
    +++ linux-2.6.22-rc6-mm1/include/linux/mm_types.h 2007-07-05 19:05:24.000000000 -0700
    @@ -49,13 +49,8 @@ struct page {
    #if NR_CPUS >= CONFIG_SPLIT_PTLOCK_CPUS
    spinlock_t ptl;
    #endif
    - struct { /* SLUB uses */
    - void **lockless_freelist;
    - struct kmem_cache *slab; /* Pointer to slab */
    - };
    - struct {
    - struct page *first_page; /* Compound pages */
    - };
    + struct kmem_cache *slab; /* SLUB: Pointer to slab */
    + struct page *first_page; /* Compound tail pages */
    };
    union {
    pgoff_t index; /* Our offset within mapping. */
    Index: linux-2.6.22-rc6-mm1/mm/slub.c
    ===================================================================
    --- linux-2.6.22-rc6-mm1.orig/mm/slub.c 2007-07-05 19:05:16.000000000 -0700
    +++ linux-2.6.22-rc6-mm1/mm/slub.c 2007-07-05 19:05:24.000000000 -0700
    @@ -1109,7 +1109,6 @@ static struct page *new_slab(struct kmem
    atomic_long_inc(&n->nr_slabs);

    page->inuse = 0;
    - page->lockless_freelist = NULL;
    page->offset = s->offset / sizeof(void *);
    page->slab = s;

    @@ -1163,7 +1162,6 @@ static void __free_slab(struct kmem_cach
    NR_SLAB_RECLAIMABLE : NR_SLAB_UNRECLAIMABLE,
    - pages);

    - page->mapping = NULL;
    __free_pages(page, s->order);
    }

    --
    -
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