lib/interval_tree: fast overlap detection

Allow interval trees to quickly check for overlaps to avoid unnecesary
tree lookups in interval_tree_iter_first().

As of this patch, all interval tree flavors will require using a
'rb_root_cached' such that we can have the leftmost node easily
available.  While most users will make use of this feature, those with
special functions (in addition to the generic insert, delete, search
calls) will avoid using the cached option as they can do funky things
with insertions -- for example, vma_interval_tree_insert_after().

[jglisse@redhat.com: fix deadlock from typo vm_lock_anon_vma()]
  Link: http://lkml.kernel.org/r/20170808225719.20723-1-jglisse@redhat.com
Link: http://lkml.kernel.org/r/20170719014603.19029-12-dave@stgolabs.net
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
Acked-by: Christian König <christian.koenig@amd.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Doug Ledford <dledford@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Christian Benvenuti <benve@cisco.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 5 insertions, 5 deletions

diff --git a/mm/interval_tree.c b/mm/interval_tree.c
index f2c2492..b476643 100644
--- a/mm/interval_tree.c
+++ b/mm/interval_tree.c
@@ -28,7 +28,7 @@ INTERVAL_TREE_DEFINE(struct vm_area_struct, shared.rb,
 /* Insert node immediately after prev in the interval tree */
 void vma_interval_tree_insert_after(struct vm_area_struct *node,
 				    struct vm_area_struct *prev,
-				    struct rb_root *root)
+				    struct rb_root_cached *root)
 {
 	struct rb_node **link;
 	struct vm_area_struct *parent;
@@ -55,7 +55,7 @@ void vma_interval_tree_insert_after(struct vm_area_struct *node,
 
 	node->shared.rb_subtree_last = last;
 	rb_link_node(&node->shared.rb, &parent->shared.rb, link);
-	rb_insert_augmented(&node->shared.rb, root,
+	rb_insert_augmented(&node->shared.rb, &root->rb_root,
 			    &vma_interval_tree_augment);
 }
 
@@ -74,7 +74,7 @@ INTERVAL_TREE_DEFINE(struct anon_vma_chain, rb, unsigned long, rb_subtree_last,
 		     static inline, __anon_vma_interval_tree)
 
 void anon_vma_interval_tree_insert(struct anon_vma_chain *node,
-				   struct rb_root *root)
+				   struct rb_root_cached *root)
 {
 #ifdef CONFIG_DEBUG_VM_RB
 	node->cached_vma_start = avc_start_pgoff(node);
@@ -84,13 +84,13 @@ void anon_vma_interval_tree_insert(struct anon_vma_chain *node,
 }
 
 void anon_vma_interval_tree_remove(struct anon_vma_chain *node,
-				   struct rb_root *root)
+				   struct rb_root_cached *root)
 {
 	__anon_vma_interval_tree_remove(node, root);
 }
 
 struct anon_vma_chain *
-anon_vma_interval_tree_iter_first(struct rb_root *root,
+anon_vma_interval_tree_iter_first(struct rb_root_cached *root,
 				  unsigned long first, unsigned long last)
 {
 	return __anon_vma_interval_tree_iter_first(root, first, last);