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Date: Tue, 13 Aug 2019 11:29:22 +0200
From: Uladzislau Rezki <urezki@...il.com>
To: Michel Lespinasse <walken@...gle.com>
Cc: "Uladzislau Rezki (Sony)" <urezki@...il.com>,
Andrew Morton <akpm@...ux-foundation.org>,
linux-mm <linux-mm@...ck.org>,
LKML <linux-kernel@...r.kernel.org>,
Peter Zijlstra <peterz@...radead.org>,
Roman Gushchin <guro@...com>, Hillf Danton <hdanton@...a.com>,
Michal Hocko <mhocko@...e.com>,
Matthew Wilcox <willy@...radead.org>,
Oleksiy Avramchenko <oleksiy.avramchenko@...ymobile.com>,
Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH 0/2] some cleanups related to RB_DECLARE_CALLBACKS_MAX
>
> I think it would be sufficient to call RBCOMPUTE(node, true) on every
> node and check the return value ?
>
Yes, that is enough for sure. The only way i was thinking about to make it
public, because checking the tree for MAX is generic for every users which
use RB_DECLARE_CALLBACKS_MAX template. Something like:
validate_rb_max_tree() {
for (nd = rb_first(root); nd; nd = rb_next(nd)) {
fooo = rb_entry(nd, struct sometinhf, rb_field);
WARN_ON(!*_compute_max(foo, true);
}
}
and call this public function under debug code. But i do not have strong
opinion here and it is probably odd. Anyway i am fine with your change.
There is small comment below:
>
> Something like the following (probably applicable in other files too):
>
> ---------------------------------- 8< ------------------------------------
>
> augmented rbtree: use generated compute_max function for debug checks
>
> In debug code, use the generated compute_max function instead of
> reimplementing similar functionality in multiple places.
>
> Signed-off-by: Michel Lespinasse <walken@...gle.com>
> ---
> lib/rbtree_test.c | 15 +-------------
> mm/mmap.c | 26 +++--------------------
> mm/vmalloc.c | 53 +++++++----------------------------------------
> 3 files changed, 12 insertions(+), 82 deletions(-)
>
> diff --git a/lib/rbtree_test.c b/lib/rbtree_test.c
> index 41ae3c7570d3..a5a04e820f77 100644
> --- a/lib/rbtree_test.c
> +++ b/lib/rbtree_test.c
> @@ -222,20 +222,7 @@ static void check_augmented(int nr_nodes)
> check(nr_nodes);
> for (rb = rb_first(&root.rb_root); rb; rb = rb_next(rb)) {
> struct test_node *node = rb_entry(rb, struct test_node, rb);
> - u32 subtree, max = node->val;
> - if (node->rb.rb_left) {
> - subtree = rb_entry(node->rb.rb_left, struct test_node,
> - rb)->augmented;
> - if (max < subtree)
> - max = subtree;
> - }
> - if (node->rb.rb_right) {
> - subtree = rb_entry(node->rb.rb_right, struct test_node,
> - rb)->augmented;
> - if (max < subtree)
> - max = subtree;
> - }
> - WARN_ON_ONCE(node->augmented != max);
> + WARN_ON_ONCE(!augment_callbacks_compute_max(node, true));
> }
> }
>
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 24f0772d6afd..d6d23e6c2d10 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -311,24 +311,6 @@ static inline unsigned long vma_compute_gap(struct vm_area_struct *vma)
> }
>
> #ifdef CONFIG_DEBUG_VM_RB
> -static unsigned long vma_compute_subtree_gap(struct vm_area_struct *vma)
> -{
> - unsigned long max = vma_compute_gap(vma), subtree_gap;
> - if (vma->vm_rb.rb_left) {
> - subtree_gap = rb_entry(vma->vm_rb.rb_left,
> - struct vm_area_struct, vm_rb)->rb_subtree_gap;
> - if (subtree_gap > max)
> - max = subtree_gap;
> - }
> - if (vma->vm_rb.rb_right) {
> - subtree_gap = rb_entry(vma->vm_rb.rb_right,
> - struct vm_area_struct, vm_rb)->rb_subtree_gap;
> - if (subtree_gap > max)
> - max = subtree_gap;
> - }
> - return max;
> -}
> -
> static int browse_rb(struct mm_struct *mm)
> {
> struct rb_root *root = &mm->mm_rb;
> @@ -355,10 +337,8 @@ static int browse_rb(struct mm_struct *mm)
> bug = 1;
> }
> spin_lock(&mm->page_table_lock);
> - if (vma->rb_subtree_gap != vma_compute_subtree_gap(vma)) {
> - pr_emerg("free gap %lx, correct %lx\n",
> - vma->rb_subtree_gap,
> - vma_compute_subtree_gap(vma));
> + if (!vma_gap_callbacks_compute_max(vma, true)) {
> + pr_emerg("wrong subtree gap in vma %p\n", vma);
> bug = 1;
> }
> spin_unlock(&mm->page_table_lock);
> @@ -385,7 +365,7 @@ static void validate_mm_rb(struct rb_root *root, struct vm_area_struct *ignore)
> struct vm_area_struct *vma;
> vma = rb_entry(nd, struct vm_area_struct, vm_rb);
> VM_BUG_ON_VMA(vma != ignore &&
> - vma->rb_subtree_gap != vma_compute_subtree_gap(vma),
> + !vma_gap_callbacks_compute_max(vma, true),
> vma);
> }
> }
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index f7c61accb0e2..ea23ccaf70fc 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -553,48 +553,6 @@ unlink_va(struct vmap_area *va, struct rb_root *root)
> RB_CLEAR_NODE(&va->rb_node);
> }
>
> -#if DEBUG_AUGMENT_PROPAGATE_CHECK
> -static void
> -augment_tree_propagate_check(struct rb_node *n)
> -{
> - struct vmap_area *va;
> - struct rb_node *node;
> - unsigned long size;
> - bool found = false;
> -
> - if (n == NULL)
> - return;
> -
> - va = rb_entry(n, struct vmap_area, rb_node);
> - size = va->subtree_max_size;
> - node = n;
> -
> - while (node) {
> - va = rb_entry(node, struct vmap_area, rb_node);
> -
> - if (get_subtree_max_size(node->rb_left) == size) {
> - node = node->rb_left;
> - } else {
> - if (va_size(va) == size) {
> - found = true;
> - break;
> - }
> -
> - node = node->rb_right;
> - }
> - }
> -
> - if (!found) {
> - va = rb_entry(n, struct vmap_area, rb_node);
> - pr_emerg("tree is corrupted: %lu, %lu\n",
> - va_size(va), va->subtree_max_size);
> - }
> -
> - augment_tree_propagate_check(n->rb_left);
> - augment_tree_propagate_check(n->rb_right);
> -}
> -#endif
> -
> /*
> * This function populates subtree_max_size from bottom to upper
> * levels starting from VA point. The propagation must be done
> @@ -645,9 +603,14 @@ augment_tree_propagate_from(struct vmap_area *va)
> node = rb_parent(&va->rb_node);
> }
>
> -#if DEBUG_AUGMENT_PROPAGATE_CHECK
> - augment_tree_propagate_check(free_vmap_area_root.rb_node);
> -#endif
> + if (DEBUG_AUGMENT_PROPAGATE_CHECK) {
> + struct vmap_area *va;
> +
> + list_for_each_entry(va, &free_vmap_area_list, list) {
> + WARN_ON(!free_vmap_area_rb_augment_cb_compute_max(
> + va, true));
> + }
> + }
> }
>
The object of validating is the tree, therefore it makes sense to go with it,
instead of iterating over the list.
Thank you!
--
Vlad Rezki
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