Replace miss typing va->va_start > tmp_va->va_start and va->va_end < tmp_va->va_end
with va->va_start > tmp_va->va_end and va->va_end < tmp_va->va_end.
It ensures va and tmp never overlap.
> On Sep 4, 2016, at 9:29 PM, Peng Gao <peng.gao.dut@xxxxxxxxx> wrote:
>
> I am browsing the code
>
> static void __insert_vmap_area(struct vmap_area *va)
> {
> struct rb_node **p = &vmap_area_root.rb_node;
> struct rb_node *parent = NULL;
> struct rb_node *tmp;
>
> while (*p) {
> struct vmap_area *tmp_va;
>
> parent = *p;
> tmp_va = rb_entry(parent, struct vmap_area, rb_node);
> if (va->va_start < tmp_va->va_end)
> p = &(*p)->rb_left;
> else if (va->va_end > tmp_va->va_start)
> p = &(*p)->rb_right;
> else
> BUG();
> }
>
> rb_link_node(&va->rb_node, parent, p);
> rb_insert_color(&va->rb_node, &vmap_area_root);
>
> /* address-sort this list */
> tmp = rb_prev(&va->rb_node);
> if (tmp) {
> struct vmap_area *prev;
> prev = rb_entry(tmp, struct vmap_area, rb_node);
> list_add_rcu(&va->list, &prev->list);
> } else
> list_add_rcu(&va->list, &vmap_area_list);
> }
>
> As far as I can know map_area is a range for the vmalloc to alloc non-contigious memory, which confuses me is that why not use va->va_start > tmp_va->va_start and va->va_end < tmp_va->va_end to insert a new vmap_area. Can a virtual address mapping overlap?
>
> One more question
>
> In alloc_map_area, I found this part of code.
>
> /* from the starting point, walk areas until a suitable hole is found */
> while (addr + size > first->va_start && addr + size <= vend) {
> if (addr + cached_hole_size < first->va_start) /* cached_hole_size */
> cached_hole_size = first->va_start - addr;
> addr = ALIGN(first->va_end, align);
> if (addr + size < addr)
> goto overflow;
>
> if (list_is_last(&first->list, &vmap_area_list))
> goto found;
>
> first = list_next_entry(first, list);
> }
>
> It seems like just inert a map_area at the end of list, what dose suitable hole means?
> Why not add this?
>
> if(addr+size < first->va_start)
> goto notound
>
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