1 files changed, 113 insertions, 24 deletions

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index df4a19d65206..afa5bc5c7c1a 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -12,6 +12,9 @@ static int split_leaf(struct ctree_root *root, struct ctree_path *path,
                       int data_size);
 static int push_node_left(struct ctree_root *root, struct tree_buffer *dst,
                           struct tree_buffer *src);
+static int balance_node_right(struct ctree_root *root,
+                              struct tree_buffer *dst_buf,
+                              struct tree_buffer *src_buf);
 static int del_ptr(struct ctree_root *root, struct ctree_path *path, int level,
                    int slot);
 
@@ -217,15 +220,16 @@ static int balance_level(struct ctree_root *root, struct ctree_path *path,
         int ret = 0;
         int wret;
         int pslot;
-        int used = 0;
-        int count;
         int orig_slot = path->slots[level];
+        u64 orig_ptr;
 
         if (level == 0)
                 return 0;
 
         mid_buf = path->nodes[level];
         mid = &mid_buf->node;
+        orig_ptr = mid->blockptrs[orig_slot];
+
         if (level < MAX_LEVEL - 1)
                 parent_buf = path->nodes[level + 1];
         pslot = path->slots[level + 1];
@@ -253,24 +257,26 @@ static int balance_level(struct ctree_root *root, struct ctree_path *path,
         if (mid->header.nritems > NODEPTRS_PER_BLOCK / 4)
                 return 0;
 
-        // print_tree(root, root->node);
         left_buf = read_node_slot(root, parent_buf, pslot - 1);
         right_buf = read_node_slot(root, parent_buf, pslot + 1);
-        if (right_buf) {
-                right = &right_buf->node;
-                used = right->header.nritems;
-                count = 1;
-        }
+
+        /* first, try to make some room in the middle buffer */
         if (left_buf) {
                 left = &left_buf->node;
-                used += left->header.nritems;
                 orig_slot += left->header.nritems;
-                count++;
+                wret = push_node_left(root, left_buf, mid_buf);
+                if (wret < 0)
+                        ret = wret;
         }
-        if (left_buf)
-                push_node_left(root, left_buf, mid_buf);
+
+        /*
+         * then try to empty the right most buffer into the middle
+         */
         if (right_buf) {
-                push_node_left(root, mid_buf, right_buf);
+                right = &right_buf->node;
+                wret = push_node_left(root, mid_buf, right_buf);
+                if (wret < 0)
+                        ret = wret;
                 if (right->header.nritems == 0) {
                         u64 blocknr = right_buf->blocknr;
                         tree_block_release(root, right_buf);
@@ -285,9 +291,29 @@ static int balance_level(struct ctree_root *root, struct ctree_path *path,
                 } else {
                         memcpy(parent->keys + pslot + 1, right->keys,
                                 sizeof(struct key));
+                        wret = write_tree_block(root, parent_buf);
+                        if (wret)
+                                ret = wret;
                 }
         }
+        if (mid->header.nritems == 1) {
+                /*
+                 * we're not allowed to leave a node with one item in the
+                 * tree during a delete.  A deletion from lower in the tree
+                 * could try to delete the only pointer in this node.
+                 * So, pull some keys from the left.
+                 * There has to be a left pointer at this point because
+                 * otherwise we would have pulled some pointers from the
+                 * right
+                 */
+                BUG_ON(!left_buf);
+                wret = balance_node_right(root, mid_buf, left_buf);
+                if (wret < 0)
+                        ret = wret;
+                BUG_ON(wret == 1);
+        }
         if (mid->header.nritems == 0) {
+                /* we've managed to empty the middle node, drop it */
                 u64 blocknr = mid_buf->blocknr;
                 tree_block_release(root, mid_buf);
                 mid_buf = NULL;
@@ -298,11 +324,17 @@ static int balance_level(struct ctree_root *root, struct ctree_path *path,
                 wret = free_extent(root, blocknr, 1);
                 if (wret)
                         ret = wret;
-        } else
+        } else {
+                /* update the parent key to reflect our changes */
                 memcpy(parent->keys + pslot, mid->keys, sizeof(struct key));
+                wret = write_tree_block(root, parent_buf);
+                if (wret)
+                        ret = wret;
+        }
 
+        /* update the path */
         if (left_buf) {
-                if (left->header.nritems >= orig_slot) {
+                if (left->header.nritems > orig_slot) {
                         left_buf->count++; // released below
                         path->nodes[level] = left_buf;
                         path->slots[level + 1] -= 1;
@@ -314,12 +346,15 @@ static int balance_level(struct ctree_root *root, struct ctree_path *path,
                         path->slots[level] = orig_slot;
                 }
         }
+        /* double check we haven't messed things up */
+        check_block(path, level);
+        if (orig_ptr != path->nodes[level]->node.blockptrs[path->slots[level]])
+                BUG();
 
         if (right_buf)
                 tree_block_release(root, right_buf);
         if (left_buf)
                 tree_block_release(root, left_buf);
-
         return ret;
 }
 
@@ -378,6 +413,7 @@ again:
                                         goto again;
                                 c = &b->node;
                                 slot = p->slots[level];
+                                BUG_ON(c->header.nritems == 1);
                         }
                         b = read_tree_block(root, c->blockptrs[slot]);
                 } else {
@@ -433,13 +469,7 @@ static int fixup_low_keys(struct ctree_root *root,
 
 /*
  * try to push data from one node into the next node left in the
- * tree.  The src node is found at specified level in the path.
- * If some bytes were pushed, return 0, otherwise return 1.
- *
- * Lower nodes/leaves in the path are not touched, higher nodes may
- * be modified to reflect the push.
- *
- * The path is altered to reflect the push.
+ * tree.
  *
  * returns 0 if some ptrs were pushed left, < 0 if there was some horrible
  * error, and > 0 if there was no room in the left hand block.
@@ -463,7 +493,8 @@ static int push_node_left(struct ctree_root *root, struct tree_buffer *dst_buf,
         }
 
         if (src_nritems < push_items)
-                push_items =src_nritems;
+                push_items = src_nritems;
+
         memcpy(dst->keys + dst_nritems, src->keys,
                 push_items * sizeof(struct key));
         memcpy(dst->blockptrs + dst_nritems, src->blockptrs,
@@ -488,6 +519,64 @@ static int push_node_left(struct ctree_root *root, struct tree_buffer *dst_buf,
 }
 
 /*
+ * try to push data from one node into the next node right in the
+ * tree.
+ *
+ * returns 0 if some ptrs were pushed, < 0 if there was some horrible
+ * error, and > 0 if there was no room in the right hand block.
+ *
+ * this will  only push up to 1/2 the contents of the left node over
+ */
+static int balance_node_right(struct ctree_root *root,
+                              struct tree_buffer *dst_buf,
+                              struct tree_buffer *src_buf)
+{
+        struct node *src = &src_buf->node;
+        struct node *dst = &dst_buf->node;
+        int push_items = 0;
+        int max_push;
+        int src_nritems;
+        int dst_nritems;
+        int ret = 0;
+        int wret;
+
+        src_nritems = src->header.nritems;
+        dst_nritems = dst->header.nritems;
+        push_items = NODEPTRS_PER_BLOCK - dst_nritems;
+        if (push_items <= 0) {
+                return 1;
+        }
+
+        max_push = src_nritems / 2 + 1;
+        /* don't try to empty the node */
+        if (max_push > src_nritems)
+                return 1;
+        if (max_push < push_items)
+                push_items = max_push;
+
+        memmove(dst->keys + push_items, dst->keys,
+                dst_nritems * sizeof(struct key));
+        memmove(dst->blockptrs + push_items, dst->blockptrs,
+                dst_nritems * sizeof(u64));
+        memcpy(dst->keys, src->keys + src_nritems - push_items,
+                push_items * sizeof(struct key));
+        memcpy(dst->blockptrs, src->blockptrs + src_nritems - push_items,
+                push_items * sizeof(u64));
+
+        src->header.nritems -= push_items;
+        dst->header.nritems += push_items;
+
+        wret = write_tree_block(root, src_buf);
+        if (wret < 0)
+                ret = wret;
+
+        wret = write_tree_block(root, dst_buf);
+        if (wret < 0)
+                ret = wret;
+        return ret;
+}
+
+/*
  * helper function to insert a new root level in the tree.
  * A new node is allocated, and a single item is inserted to
  * point to the existing root