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    Subject[patch 10/11] mm: Reimplementation of dynamic per-cpu allocator -- allow_early_mapvmarea
    This patch provides for early calls to map_vm_area.  Currently, map_vm_area
    cannot be called early during the boot process since map_vm_area depends on
    kmalloc for the vm_struct objects. This patch is a bad hack to let
    map_vm_area work early, but just for a few calls so that the dynamic per-cpu
    subsystem can allocate a block and satisfy some early requests. This is
    primarily to enable slab code use alloc_percpu for slab head arrays. This
    patch might not be elegant, but solves the chicken and egg problem in using
    alloc_percpu for slab.

    Signed-off-by: Ravikiran Thirumalai <kiran.th@gmail.com>

    Index: alloc_percpu-2.6.13-rc6/include/linux/slab.h
    ===================================================================
    --- alloc_percpu-2.6.13-rc6.orig/include/linux/slab.h 2005-08-14 21:47:56.000000000 -0700
    +++ alloc_percpu-2.6.13-rc6/include/linux/slab.h 2005-08-15 17:29:41.000000000 -0700
    @@ -76,6 +76,8 @@
    extern struct cache_sizes malloc_sizes[];
    extern void *__kmalloc(size_t, unsigned int __nocast);

    +#define SLAB_READY ({malloc_sizes[0].cs_cachep != NULL;})
    +
    static inline void *kmalloc(size_t size, unsigned int __nocast flags)
    {
    if (__builtin_constant_p(size)) {
    Index: alloc_percpu-2.6.13-rc6/include/linux/vmalloc.h
    ===================================================================
    --- alloc_percpu-2.6.13-rc6.orig/include/linux/vmalloc.h 2005-08-15 17:28:42.000000000 -0700
    +++ alloc_percpu-2.6.13-rc6/include/linux/vmalloc.h 2005-08-15 17:29:41.000000000 -0700
    @@ -8,6 +8,7 @@
    #define VM_IOREMAP 0x00000001 /* ioremap() and friends */
    #define VM_ALLOC 0x00000002 /* vmalloc() */
    #define VM_MAP 0x00000004 /* vmap()ed pages */
    +#define VM_EARLY 0x00000008 /* indicates static vm_struct */
    /* bits [20..32] reserved for arch specific ioremap internals */

    struct vm_struct {
    Index: alloc_percpu-2.6.13-rc6/mm/vmalloc.c
    ===================================================================
    --- alloc_percpu-2.6.13-rc6.orig/mm/vmalloc.c 2005-08-15 17:28:42.000000000 -0700
    +++ alloc_percpu-2.6.13-rc6/mm/vmalloc.c 2005-08-15 17:35:29.000000000 -0700
    @@ -160,6 +160,15 @@

    #define IOREMAP_MAX_ORDER (7 + PAGE_SHIFT) /* 128 pages */

    +/*
    + * Statically define a few vm_structs so that early per-cpu allocator code
    + * can get vm_areas even before slab is up. NR_EARLY_VMAREAS should remain
    + * in single digits
    + */
    +#define NR_EARLY_VMAREAS (1)
    +static struct vm_struct early_vmareas[NR_EARLY_VMAREAS];
    +static int early_vmareas_idx = 0;
    +
    struct vm_struct *__get_vm_area(unsigned long size, unsigned long flags,
    unsigned long start, unsigned long end,
    unsigned int gfp_flags)
    @@ -168,6 +177,9 @@
    unsigned long align = 1;
    unsigned long addr;

    + if (unlikely(!size))
    + return NULL;
    +
    if (flags & VM_IOREMAP) {
    int bit = fls(size);

    @@ -184,10 +196,16 @@
    area = kmalloc(sizeof(*area), gfp_flags);
    if (unlikely(!area))
    return NULL;
    -
    - if (unlikely(!size)) {
    - kfree (area);
    - return NULL;
    + if (likely(SLAB_READY)) {
    + area = kmalloc(sizeof(*area), GFP_KERNEL);
    + if (unlikely(!area))
    + return NULL;
    + } else {
    + if (early_vmareas_idx < NR_EARLY_VMAREAS) {
    + area = &early_vmareas[early_vmareas_idx++];
    + flags |= VM_EARLY;
    + } else
    + return NULL;
    }

    /*
    @@ -228,7 +246,8 @@

    out:
    write_unlock(&vmlist_lock);
    - kfree(area);
    + if (likely(!(flags & VM_EARLY)))
    + kfree(area);
    if (printk_ratelimit())
    printk(KERN_WARNING "allocation failed: out of vmalloc space - use vmalloc=<size> to increase size.\n");
    return NULL;
    @@ -326,7 +345,8 @@
    kfree(area->pages);
    }

    - kfree(area);
    + if (likely(!(area->flags & VM_EARLY)))
    + kfree(area);
    return;
    }

    @@ -415,7 +435,8 @@
    area->pages = pages;
    if (!area->pages) {
    remove_vm_area(area->addr);
    - kfree(area);
    + if (likely(!(area->flags & VM_EARLY)))
    + kfree(area);
    return NULL;
    }
    memset(area->pages, 0, array_size);
    -
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