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Subject[PATCH] find_vma_prev rewrite

find_vma_prev doesn't return a pointer to the `prev' vma if the address
is greater than the last existing vma. This doesn't matter unless you're
on a PA-RISC machine :-)

This rewrite should speed up & make find_vma_prev simpler, as well as
fixing the previous behaviour.

--- linux-t10/mm/mmap.c Fri Oct 13 20:10:30 2000
+++ linux-mine/mm/mmap.c Wed Dec 20 15:22:53 2000
@@ -417,54 +417,48 @@
struct vm_area_struct * find_vma_prev(struct mm_struct * mm, unsigned long addr,
struct vm_area_struct **pprev)
{
- if (mm) {
- if (!mm->mmap_avl) {
- /* Go through the linear list. */
- struct vm_area_struct * prev = NULL;
- struct vm_area_struct * vma = mm->mmap;
- while (vma && vma->vm_end <= addr) {
- prev = vma;
- vma = vma->vm_next;
- }
- *pprev = prev;
- return vma;
- } else {
- /* Go through the AVL tree quickly. */
- struct vm_area_struct * vma = NULL;
- struct vm_area_struct * last_turn_right = NULL;
- struct vm_area_struct * prev = NULL;
- struct vm_area_struct * tree = mm->mmap_avl;
- for (;;) {
- if (tree == vm_avl_empty)
+ struct vm_area_struct *vma = NULL;
+ struct vm_area_struct *prev = NULL;
+ if (!mm)
+ goto out;
+ prev = mm->mmap_cache;
+ if (prev) {
+ vma = prev->vm_next;
+ if (prev->vm_end < addr &&
+ ((vma == NULL) || (addr < vma->vm_end)))
+ goto out;
+ prev = NULL;
+ }
+ vma = mm->mmap; /* guard against there being no prev */
+ if (!mm->mmap_avl) {
+ /* Go through the linear list. */
+ while (vma && vma->vm_end <= addr) {
+ prev = vma;
+ vma = vma->vm_next;
+ }
+ } else {
+ /* Go through the AVL tree quickly. */
+ struct vm_area_struct * tree = mm->mmap_avl;
+ while (tree != vm_avl_empty) {
+ if (addr < tree->vm_end) {
+ tree = tree->vm_avl_left;
+ } else {
+ prev = tree;
+ if (tree->vm_next == NULL)
break;
- if (tree->vm_end > addr) {
- vma = tree;
- prev = last_turn_right;
- if (tree->vm_start <= addr)
- break;
- tree = tree->vm_avl_left;
- } else {
- last_turn_right = tree;
- tree = tree->vm_avl_right;
- }
- }
- if (vma) {
- if (vma->vm_avl_left != vm_avl_empty) {
- prev = vma->vm_avl_left;
- while (prev->vm_avl_right != vm_avl_empty)
- prev = prev->vm_avl_right;
- }
- if ((prev ? prev->vm_next : mm->mmap) != vma)
- printk("find_vma_prev: tree inconsistent with list\n");
- *pprev = prev;
- return vma;
+ if (addr < tree->vm_next->vm_end)
+ break;
+ tree = tree->vm_avl_right;
}
}
}
- *pprev = NULL;
- return NULL;
+ mm->mmap_cache = prev;
+out:
+ *pprev = prev;
+ return prev ? prev->vm_next : vma;
}

+/* XXX: Needs to be fixed for PA-RISC -- won't grow our stack. */
struct vm_area_struct * find_extend_vma(struct mm_struct * mm, unsigned long addr)
{
struct vm_area_struct * vma;
--
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