Btrfs: Add a lookup cache to the extent state tree

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 40 insertions, 17 deletions

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 624aabc3e6f2..5f2fbf2054f2 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -90,6 +90,7 @@ void extent_io_tree_init(struct extent_io_tree *tree,
         tree->mapping = mapping;
         INIT_LIST_HEAD(&tree->buffer_lru);
         tree->lru_size = 0;
+        tree->last = NULL;
 }
 EXPORT_SYMBOL(extent_io_tree_init);
 
@@ -158,16 +159,23 @@ static struct rb_node *tree_insert(struct rb_root *root, u64 offset,
         return NULL;
 }
 
-static struct rb_node *__tree_search(struct rb_root *root, u64 offset,
+static struct rb_node *__etree_search(struct extent_io_tree *tree, u64 offset,
                                      struct rb_node **prev_ret,
                                      struct rb_node **next_ret)
 {
+        struct rb_root *root = &tree->state;
         struct rb_node * n = root->rb_node;
         struct rb_node *prev = NULL;
         struct rb_node *orig_prev = NULL;
         struct tree_entry *entry;
         struct tree_entry *prev_entry = NULL;
 
+        if (tree->last) {
+                struct extent_state *state;
+                state = tree->last;
+                if (state->start <= offset && offset <= state->end)
+                        return &tree->last->rb_node;
+        }
         while(n) {
                 entry = rb_entry(n, struct tree_entry, rb_node);
                 prev = n;
@@ -177,8 +185,10 @@ static struct rb_node *__tree_search(struct rb_root *root, u64 offset,
                         n = n->rb_left;
                 else if (offset > entry->end)
                         n = n->rb_right;
-                else
+                else {
+                        tree->last = rb_entry(n, struct extent_state, rb_node);
                         return n;
+                }
         }
 
         if (prev_ret) {
@@ -202,14 +212,20 @@ static struct rb_node *__tree_search(struct rb_root *root, u64 offset,
         return NULL;
 }
 
-static inline struct rb_node *tree_search(struct rb_root *root, u64 offset)
+static inline struct rb_node *tree_search(struct extent_io_tree *tree,
+                                          u64 offset)
 {
         struct rb_node *prev = NULL;
         struct rb_node *ret;
 
-        ret = __tree_search(root, offset, &prev, NULL);
-        if (!ret)
+        ret = __etree_search(tree, offset, &prev, NULL);
+        if (!ret) {
+                if (prev) {
+                        tree->last = rb_entry(prev, struct extent_state,
+                                              rb_node);
+                }
                 return prev;
+        }
         return ret;
 }
 
@@ -238,6 +254,8 @@ static int merge_state(struct extent_io_tree *tree,
                     other->state == state->state) {
                         state->start = other->start;
                         other->tree = NULL;
+                        if (tree->last == other)
+                                tree->last = NULL;
                         rb_erase(&other->rb_node, &tree->state);
                         free_extent_state(other);
                 }
@@ -249,6 +267,8 @@ static int merge_state(struct extent_io_tree *tree,
                     other->state == state->state) {
                         other->start = state->start;
                         state->tree = NULL;
+                        if (tree->last == state)
+                                tree->last = NULL;
                         rb_erase(&state->rb_node, &tree->state);
                         free_extent_state(state);
                 }
@@ -311,6 +331,7 @@ static int insert_state(struct extent_io_tree *tree,
                 return -EEXIST;
         }
         state->tree = tree;
+        tree->last = state;
         merge_state(tree, state);
         return 0;
 }
@@ -375,6 +396,8 @@ static int clear_state_bit(struct extent_io_tree *tree,
                 wake_up(&state->wq);
         if (delete || state->state == 0) {
                 if (state->tree) {
+                        if (tree->last == state)
+                                tree->last = NULL;
                         rb_erase(&state->rb_node, &tree->state);
                         state->tree = NULL;
                         free_extent_state(state);
@@ -422,7 +445,7 @@ again:
          * this search will find the extents that end after
          * our range starts
          */
-        node = tree_search(&tree->state, start);
+        node = tree_search(tree, start);
         if (!node)
                 goto out;
         state = rb_entry(node, struct extent_state, rb_node);
@@ -533,7 +556,7 @@ again:
                  * this search will find all the extents that end after
                  * our range starts
                  */
-                node = tree_search(&tree->state, start);
+                node = tree_search(tree, start);
                 if (!node)
                         break;
 
@@ -612,7 +635,7 @@ again:
          * this search will find all the extents that end after
          * our range starts.
          */
-        node = tree_search(&tree->state, start);
+        node = tree_search(tree, start);
         if (!node) {
                 err = insert_state(tree, prealloc, start, end, bits);
                 prealloc = NULL;
@@ -915,7 +938,7 @@ int find_first_extent_bit(struct extent_io_tree *tree, u64 start,
          * this search will find all the extents that end after
          * our range starts.
          */
-        node = tree_search(&tree->state, start);
+        node = tree_search(tree, start);
         if (!node || IS_ERR(node)) {
                 goto out;
         }
@@ -953,7 +976,7 @@ u64 find_lock_delalloc_range(struct extent_io_tree *tree,
          * our range starts.
          */
 search_again:
-        node = tree_search(&tree->state, cur_start);
+        node = tree_search(tree, cur_start);
         if (!node || IS_ERR(node)) {
                 *end = (u64)-1;
                 goto out;
@@ -1041,7 +1064,7 @@ u64 count_range_bits(struct extent_io_tree *tree,
          * this search will find all the extents that end after
          * our range starts.
          */
-        node = tree_search(&tree->state, cur_start);
+        node = tree_search(tree, cur_start);
         if (!node || IS_ERR(node)) {
                 goto out;
         }
@@ -1142,7 +1165,7 @@ int set_state_private(struct extent_io_tree *tree, u64 start, u64 private)
          * this search will find all the extents that end after
          * our range starts.
          */
-        node = tree_search(&tree->state, start);
+        node = tree_search(tree, start);
         if (!node || IS_ERR(node)) {
                 ret = -ENOENT;
                 goto out;
@@ -1169,7 +1192,7 @@ int get_state_private(struct extent_io_tree *tree, u64 start, u64 *private)
          * this search will find all the extents that end after
          * our range starts.
          */
-        node = tree_search(&tree->state, start);
+        node = tree_search(tree, start);
         if (!node || IS_ERR(node)) {
                 ret = -ENOENT;
                 goto out;
@@ -1200,7 +1223,7 @@ int test_range_bit(struct extent_io_tree *tree, u64 start, u64 end,
         unsigned long flags;
 
         spin_lock_irqsave(&tree->lock, flags);
-        node = tree_search(&tree->state, start);
+        node = tree_search(tree, start);
         while (node && start <= end) {
                 state = rb_entry(node, struct extent_state, rb_node);
 
@@ -1348,7 +1371,7 @@ static int end_bio_extent_writepage(struct bio *bio,
                 spin_lock_irqsave(&tree->lock, flags);
                 if (!state || state->end != end) {
                         state = NULL;
-                        node = __tree_search(&tree->state, start, NULL, NULL);
+                        node = __etree_search(tree, start, NULL, NULL);
                         if (node) {
                                 state = rb_entry(node, struct extent_state,
                                                  rb_node);
@@ -1468,7 +1491,7 @@ static int end_bio_extent_readpage(struct bio *bio,
                 spin_lock_irqsave(&tree->lock, flags);
                 if (!state || state->end != end) {
                         state = NULL;
-                        node = __tree_search(&tree->state, start, NULL, NULL);
+                        node = __etree_search(tree, start, NULL, NULL);
                         if (node) {
                                 state = rb_entry(node, struct extent_state,
                                                  rb_node);
@@ -1631,7 +1654,7 @@ static int submit_one_bio(int rw, struct bio *bio)
         end = start + bvec->bv_len - 1;
 
         spin_lock_irq(&tree->lock);
-        node = __tree_search(&tree->state, start, NULL, NULL);
+        node = __etree_search(tree, start, NULL, NULL);
         BUG_ON(!node);
         state = rb_entry(node, struct extent_state, rb_node);
         while(state->end < end) {