Btrfs: Do more extensive readahead during tree searches

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

1 files changed, 49 insertions, 13 deletions

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index 51eea5ccb645..c0782a5b04c5 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -43,8 +43,10 @@ struct btrfs_path *btrfs_alloc_path(void)
 {
         struct btrfs_path *path;
         path = kmem_cache_alloc(btrfs_path_cachep, GFP_NOFS);
-        if (path)
+        if (path) {
                 btrfs_init_path(path);
+                path->reada = 1;
+        }
         return path;
 }
 
@@ -159,6 +161,34 @@ static int close_blocks(u64 blocknr, u64 other)
         return 0;
 }
 
+static int should_defrag_leaf(struct buffer_head *bh)
+{
+        struct btrfs_leaf *leaf = btrfs_buffer_leaf(bh);
+        struct btrfs_disk_key *key;
+        u32 nritems;
+
+        if (buffer_defrag(bh))
+                return 1;
+
+        nritems = btrfs_header_nritems(&leaf->header);
+        if (nritems == 0)
+                return 0;
+
+        key = &leaf->items[0].key;
+        if (btrfs_disk_key_type(key) == BTRFS_DIR_ITEM_KEY)
+                return 1;
+
+        key = &leaf->items[nritems-1].key;
+        if (btrfs_disk_key_type(key) == BTRFS_DIR_ITEM_KEY)
+                return 1;
+        if (nritems > 4) {
+                key = &leaf->items[nritems/2].key;
+                if (btrfs_disk_key_type(key) == BTRFS_DIR_ITEM_KEY)
+                        return 1;
+        }
+        return 0;
+}
+
 int btrfs_realloc_node(struct btrfs_trans_handle *trans,
                        struct btrfs_root *root, struct buffer_head *parent,
                        int cache_only, u64 *last_ret)
@@ -217,7 +247,9 @@ int btrfs_realloc_node(struct btrfs_trans_handle *trans,
 
                 cur_bh = btrfs_find_tree_block(root, blocknr);
                 if (!cur_bh || !buffer_uptodate(cur_bh) ||
-                    buffer_locked(cur_bh) || !buffer_defrag(cur_bh)) {
+                    buffer_locked(cur_bh) ||
+                    (parent_level != 1 && !buffer_defrag(cur_bh)) ||
+                    (parent_level == 1 && !should_defrag_leaf(cur_bh))) {
                         if (cache_only) {
                                 brelse(cur_bh);
                                 continue;
@@ -297,6 +329,7 @@ static int check_node(struct btrfs_root *root, struct btrfs_path *path,
                 parent = btrfs_buffer_node(path->nodes[level + 1]);
 
         slot = path->slots[level];
+        BUG_ON(!buffer_uptodate(path->nodes[level]));
         BUG_ON(nritems == 0);
         if (parent) {
                 struct btrfs_disk_key *parent_key;
@@ -511,9 +544,6 @@ static int balance_level(struct btrfs_trans_handle *trans, struct btrfs_root
                 err_on_enospc = 1;
 
         left_buf = read_node_slot(root, parent_buf, pslot - 1);
-        right_buf = read_node_slot(root, parent_buf, pslot + 1);
-
-        /* first, try to make some room in the middle buffer */
         if (left_buf) {
                 wret = btrfs_cow_block(trans, root, left_buf,
                                        parent_buf, pslot - 1, &left_buf);
@@ -521,6 +551,19 @@ static int balance_level(struct btrfs_trans_handle *trans, struct btrfs_root
                         ret = wret;
                         goto enospc;
                 }
+        }
+        right_buf = read_node_slot(root, parent_buf, pslot + 1);
+        if (right_buf) {
+                wret = btrfs_cow_block(trans, root, right_buf,
+                                       parent_buf, pslot + 1, &right_buf);
+                if (wret) {
+                        ret = wret;
+                        goto enospc;
+                }
+        }
+
+        /* first, try to make some room in the middle buffer */
+        if (left_buf) {
                 left = btrfs_buffer_node(left_buf);
                 orig_slot += btrfs_header_nritems(&left->header);
                 wret = push_node_left(trans, root, left_buf, mid_buf);
@@ -534,13 +577,6 @@ static int balance_level(struct btrfs_trans_handle *trans, struct btrfs_root
          * then try to empty the right most buffer into the middle
          */
         if (right_buf) {
-                wret = btrfs_cow_block(trans, root, right_buf,
-                                       parent_buf, pslot + 1, &right_buf);
-                if (wret) {
-                        ret = wret;
-                        goto enospc;
-                }
-
                 right = btrfs_buffer_node(right_buf);
                 wret = push_node_left(trans, root, mid_buf, right_buf);
                 if (wret < 0 && wret != -ENOSPC)
@@ -817,7 +853,7 @@ static void reada_for_search(struct btrfs_root *root, struct btrfs_path *path,
                 for (i = 0; i < ret; i++) {
                         blocknr = gang[i];
                         clear_radix_bit(&found, blocknr);
-                        if (nread > 32)
+                        if (path->reada == 1 && nread > 16)
                                 continue;
                         if (close_blocks(cluster_start, blocknr)) {
                                 readahead_tree_block(root, blocknr);