Btrfs: Add a lookup cache to the extent state tree

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

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 624aabc..5f2fbf2 100644 (file)
--- 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) {

diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
index 6fd5e2c..160da3f 100644 (file)
--- a/fs/btrfs/extent_io.h
+++ b/fs/btrfs/extent_io.h
@@ -48,6 +48,7 @@ struct extent_io_tree {
        spinlock_t lru_lock;
        struct list_head buffer_lru;
        int lru_size;
+       struct extent_state *last;
 };
 
 struct extent_state {