Btrfs: Allocator improvements

Reduce CPU time searching for free blocks by optimizing find_first_extent_bit

Fix find_free_extent to make better use of the last_alloc hint.  Before it
was often finding blocks just before the hint.

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

1 files changed, 34 insertions, 4 deletions

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 9262ab37a7cd..fb6400895ed6 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -255,7 +255,7 @@ static int merge_state(struct extent_io_tree *tree,
                         state->start = other->start;
                         other->tree = NULL;
                         if (tree->last == other)
-                                tree->last = NULL;
+                                tree->last = state;
                         rb_erase(&other->rb_node, &tree->state);
                         free_extent_state(other);
                 }
@@ -268,7 +268,7 @@ static int merge_state(struct extent_io_tree *tree,
                         other->start = state->start;
                         state->tree = NULL;
                         if (tree->last == state)
-                                tree->last = NULL;
+                                tree->last = other;
                         rb_erase(&state->rb_node, &tree->state);
                         free_extent_state(state);
                 }
@@ -397,8 +397,9 @@ static int clear_state_bit(struct extent_io_tree *tree,
         if (delete || state->state == 0) {
                 if (state->tree) {
                         clear_state_cb(tree, state, state->state);
-                        if (tree->last == state)
-                                tree->last = NULL;
+                        if (tree->last == state) {
+                                tree->last = extent_state_next(state);
+                        }
                         rb_erase(&state->rb_node, &tree->state);
                         state->tree = NULL;
                         free_extent_state(state);
@@ -962,6 +963,35 @@ out:
 }
 EXPORT_SYMBOL(find_first_extent_bit);
 
+struct extent_state *find_first_extent_bit_state(struct extent_io_tree *tree,
+                                                 u64 start, int bits)
+{
+        struct rb_node *node;
+        struct extent_state *state;
+
+        /*
+         * this search will find all the extents that end after
+         * our range starts.
+         */
+        node = tree_search(tree, start);
+        if (!node || IS_ERR(node)) {
+                goto out;
+        }
+
+        while(1) {
+                state = rb_entry(node, struct extent_state, rb_node);
+                if (state->end >= start && (state->state & bits)) {
+                        return state;
+                }
+                node = rb_next(node);
+                if (!node)
+                        break;
+        }
+out:
+        return NULL;
+}
+EXPORT_SYMBOL(find_first_extent_bit_state);
+
 u64 find_lock_delalloc_range(struct extent_io_tree *tree,
                              u64 *start, u64 *end, u64 max_bytes)
 {