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    Subjectvm_unmap_aliases and Xen
    I've been having a few problems with Xen, I suspect as a result of the 
    lazy unmapping in vmalloc.c.

    One immediate one is that vm_unmap_aliases() will oops if you call it
    before vmalloc_init() is called, which can happen in the Xen case. RFC
    patch below.

    But the bigger problem I'm seeing is that despite calling
    vm_unmap_aliases() at the pertinent places, I'm still seeing errors
    resulting from stray aliases. Is it possible that vm_unmap_aliases()
    could be missing some, or not completely synchronous?

    Subject: vmap: cope with vm_unmap_aliases before vmalloc_init()

    Xen can end up calling vm_unmap_aliases() before vmalloc_init() has
    been called. In this case its safe to make it a simple no-op.

    Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
    diff -r 42c8b29f7ccf mm/vmalloc.c
    --- a/mm/vmalloc.c Wed Oct 22 12:43:39 2008 -0700
    +++ b/mm/vmalloc.c Wed Oct 22 21:39:00 2008 -0700
    @@ -591,6 +591,8 @@

    #define VMAP_BLOCK_SIZE (VMAP_BBMAP_BITS * PAGE_SIZE)

    +static bool vmap_initialized = false;
    +
    struct vmap_block_queue {
    spinlock_t lock;
    struct list_head free;
    @@ -827,6 +829,9 @@
    int cpu;
    int flush = 0;

    + if (!vmap_initialized)
    + return;
    +
    for_each_possible_cpu(cpu) {
    struct vmap_block_queue *vbq = &per_cpu(vmap_block_queue, cpu);
    struct vmap_block *vb;
    @@ -940,6 +945,8 @@
    INIT_LIST_HEAD(&vbq->dirty);
    vbq->nr_dirty = 0;
    }
    +
    + vmap_initialized = true;
    }

    void unmap_kernel_range(unsigned long addr, unsigned long size)



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