1 files changed, 133 insertions, 0 deletions

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index 0c5c28ff794f..e8b32641ea90 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -5490,6 +5490,139 @@ int btrfs_next_leaf(struct btrfs_root *root, struct btrfs_path *path)
         return btrfs_next_old_leaf(root, path, 0);
 }
 
+/* Release the path up to but not including the given level */
+static void btrfs_release_level(struct btrfs_path *path, int level)
+{
+        int i;
+
+        for (i = 0; i < level; i++) {
+                path->slots[i] = 0;
+                if (!path->nodes[i])
+                        continue;
+                if (path->locks[i]) {
+                        btrfs_tree_unlock_rw(path->nodes[i], path->locks[i]);
+                        path->locks[i] = 0;
+                }
+                free_extent_buffer(path->nodes[i]);
+                path->nodes[i] = NULL;
+        }
+}
+
+/*
+ * This function assumes 2 things
+ *
+ * 1) You are using path->keep_locks
+ * 2) You are not inserting items.
+ *
+ * If either of these are not true do not use this function. If you need a next
+ * leaf with either of these not being true then this function can be easily
+ * adapted to do that, but at the moment these are the limitations.
+ */
+int btrfs_next_leaf_write(struct btrfs_trans_handle *trans,
+                          struct btrfs_root *root, struct btrfs_path *path,
+                          int del)
+{
+        struct extent_buffer *b;
+        struct btrfs_key key;
+        u32 nritems;
+        int level = 1;
+        int slot;
+        int ret = 1;
+        int write_lock_level = BTRFS_MAX_LEVEL;
+        int ins_len = del ? -1 : 0;
+
+        WARN_ON(!(path->keep_locks || path->really_keep_locks));
+
+        nritems = btrfs_header_nritems(path->nodes[0]);
+        btrfs_item_key_to_cpu(path->nodes[0], &key, nritems - 1);
+
+        while (path->nodes[level]) {
+                nritems = btrfs_header_nritems(path->nodes[level]);
+                if (!(path->locks[level] & BTRFS_WRITE_LOCK)) {
+search:
+                        btrfs_release_path(path);
+                        ret = btrfs_search_slot(trans, root, &key, path,
+                                                ins_len, 1);
+                        if (ret < 0)
+                                goto out;
+                        level = 1;
+                        continue;
+                }
+
+                if (path->slots[level] >= nritems - 1) {
+                        level++;
+                        continue;
+                }
+
+                btrfs_release_level(path, level);
+                break;
+        }
+
+        if (!path->nodes[level]) {
+                ret = 1;
+                goto out;
+        }
+
+        path->slots[level]++;
+        b = path->nodes[level];
+
+        while (b) {
+                level = btrfs_header_level(b);
+
+                if (!should_cow_block(trans, root, b))
+                        goto cow_done;
+
+                btrfs_set_path_blocking(path);
+                ret = btrfs_cow_block(trans, root, b,
+                                      path->nodes[level + 1],
+                                      path->slots[level + 1], &b);
+                if (ret)
+                        goto out;
+cow_done:
+                path->nodes[level] = b;
+                btrfs_clear_path_blocking(path, NULL, 0);
+                if (level != 0) {
+                        ret = setup_nodes_for_search(trans, root, path, b,
+                                                     level, ins_len,
+                                                     &write_lock_level);
+                        if (ret == -EAGAIN)
+                                goto search;
+                        if (ret)
+                                goto out;
+
+                        b = path->nodes[level];
+                        slot = path->slots[level];
+
+                        ret = read_block_for_search(trans, root, path,
+                                                    &b, level, slot, &key, 0);
+                        if (ret == -EAGAIN)
+                                goto search;
+                        if (ret)
+                                goto out;
+                        level = btrfs_header_level(b);
+                        if (!btrfs_try_tree_write_lock(b)) {
+                                btrfs_set_path_blocking(path);
+                                btrfs_tree_lock(b);
+                                btrfs_clear_path_blocking(path, b,
+                                                          BTRFS_WRITE_LOCK);
+                        }
+                        path->locks[level] = BTRFS_WRITE_LOCK;
+                        path->nodes[level] = b;
+                        path->slots[level] = 0;
+                } else {
+                        path->slots[level] = 0;
+                        ret = 0;
+                        break;
+                }
+        }
+
+out:
+        if (ret)
+                btrfs_release_path(path);
+
+        return ret;
+}
+
 int btrfs_next_old_leaf(struct btrfs_root *root, struct btrfs_path *path,
                         u64 time_seq)
 {