diff options
Diffstat (limited to 'ctree.c')
| -rw-r--r-- | ctree.c | 137 |
1 files changed, 113 insertions, 24 deletions
@@ -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 |