On Thu, Jun 21, 2012 at 05:57:09PM -0400, Rik van Riel wrote:
> + if (!vma->vm_prev) {
> + /* This is the left-most VMA. */
> + if (vma->vm_start - len >= lower_limit) {
> + addr = lower_limit;
> + goto found_addr;
> + }
> + } else {
> + /* Is this gap large enough? Remember it. */
> + vma_start = max(vma->vm_prev->vm_end, lower_limit);
> + if (vma->vm_start - len >= vma_start) {
> + addr = vma_start;
> + found_here = true;
> + }
> + }
You could unify these two cases:
vma_start = lower_limit;
if (vma->vm_prev && vma->vm_prev->vm_end > vma_start)
vma_start = vma->vm_prev->vm_end;
if (vma->vm_start - len >= vma_start) {
addr = vma_start;
found_here = true;
}
You don't need the goto found_addr; the search won't be going left as there
is no node there and it won't be going right as found_here is true.
We may also be albe to dispense with found_here and replace it with a special
value (either NULL or something not page aligned) for addr.
> + if (!found_here && node_free_gap(rb_node->rb_right) >= len) {
> + /* Last known gap is to the right of this subtree. */
> + rb_node = rb_node->rb_right;
> + continue;
> + } else if (!addr) {
> + rb_node = rb_find_next_uncle(rb_node);
> + continue;
> }
Looks like you're already using my suggestion of using !addr to indicate
we haven't found a suitable gap yet :)
I don't think we want to visit just any uncle though - we want to visit one
that has a large enough free gap somewhere in its subtree.
So, maybe:
if (!found_here) { // or if(!addr) or whatever
struct rb_node *rb_prev = NULL;
do {
if (rb_node != rb_prev &&
node_free_gap(rb_node->rb_right) >= len) {
rb_node = rb_node->rb_right;
break;
}
rb_prev = rb_node;
rb_node = rb_parent(rb_node);
} while (rb_node);
continue;
}
> + /* This is the left-most gap. */
> + goto found_addr;
> }
> +
> + /*
> + * There is not enough space to the left of any VMA.
> + * Check the far right-hand side of the VMA tree.
> + */
> + rb_node = mm->mm_rb.rb_node;
> + while (rb_node->rb_right)
> + rb_node = rb_node->rb_right;
> + vma = rb_to_vma(rb_node);
> + addr = vma->vm_end;
> +
> + /*
> + * The right-most VMA ends below the lower limit. Can only happen
> + * if a binary personality loads the stack below the executable.
> + */
> + if (addr < lower_limit)
> + addr = lower_limit;
> +
> + found_addr:
> + if (TASK_SIZE - len < addr)
> + return -ENOMEM;
I'm confused - if we come from 'goto found_addr', we found a gap to the
left of an existing vma; aren't we guaranteed that this gap ends to the
left of TASK_SIZE too since the existing vma's vm_begin should be
less than TASK_SIZE ?
--
Michel "Walken" Lespinasse
A program is never fully debugged until the last user dies.
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>