Btrfs: more efficient split extent state insertion

When we split an extent state there's no need to start the rbtree search
from the root node - we can start it from the original extent state node,
since we would end up in its subtree if we do the search starting at the
root node anyway.

Signed-off-by: Filipe David Borba Manana <fdmanana@gmail.com>
Signed-off-by: Josef Bacik <jbacik@fb.com>

1 files changed, 8 insertions, 5 deletions

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 2c9fbe3b6eec..fd78c84821c8 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -229,12 +229,14 @@ void free_extent_state(struct extent_state *state)
         }
 }
 
-static struct rb_node *tree_insert(struct rb_root *root, u64 offset,
+static struct rb_node *tree_insert(struct rb_root *root,
+                                   struct rb_node *search_start,
+                                   u64 offset,
                                    struct rb_node *node,
                                    struct rb_node ***p_in,
                                    struct rb_node **parent_in)
 {
-        struct rb_node **p = &root->rb_node;
+        struct rb_node **p;
         struct rb_node *parent = NULL;
         struct tree_entry *entry;
 
@@ -244,6 +246,7 @@ static struct rb_node *tree_insert(struct rb_root *root, u64 offset,
                 goto do_insert;
         }
 
+        p = search_start ? &search_start : &root->rb_node;
         while (*p) {
                 parent = *p;
                 entry = rb_entry(parent, struct tree_entry, rb_node);
@@ -430,7 +433,7 @@ static int insert_state(struct extent_io_tree *tree,
 
         set_state_bits(tree, state, bits);
 
-        node = tree_insert(&tree->state, end, &state->rb_node, p, parent);
+        node = tree_insert(&tree->state, NULL, end, &state->rb_node, p, parent);
         if (node) {
                 struct extent_state *found;
                 found = rb_entry(node, struct extent_state, rb_node);
@@ -477,8 +480,8 @@ static int split_state(struct extent_io_tree *tree, struct extent_state *orig,
         prealloc->state = orig->state;
         orig->start = split;
 
-        node = tree_insert(&tree->state, prealloc->end, &prealloc->rb_node,
-                           NULL, NULL);
+        node = tree_insert(&tree->state, &orig->rb_node, prealloc->end,
+                           &prealloc->rb_node, NULL, NULL);
         if (node) {
                 free_extent_state(prealloc);
                 return -EEXIST;