diff options
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/btrfs/ctree.c | 249 |
1 files changed, 186 insertions, 63 deletions
diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c index 6f0522f2108..6b64f49a027 100644 --- a/fs/btrfs/ctree.c +++ b/fs/btrfs/ctree.c @@ -20,6 +20,11 @@ static void release_path(struct ctree_root *root, struct ctree_path *p) } } +/* + * The leaf data grows from end-to-front in the node. + * this returns the address of the start of the last item, + * which is the stop of the leaf data stack + */ static inline unsigned int leaf_data_end(struct leaf *leaf) { unsigned int nr = leaf->header.nritems; @@ -28,6 +33,11 @@ static inline unsigned int leaf_data_end(struct leaf *leaf) return leaf->items[nr-1].offset; } +/* + * The space between the end of the leaf items and + * the start of the leaf data. IOW, how much room + * the leaf has left for both items and data + */ static inline int leaf_free_space(struct leaf *leaf) { int data_end = leaf_data_end(leaf); @@ -36,6 +46,9 @@ static inline int leaf_free_space(struct leaf *leaf) return (char *)(leaf->data + data_end) - (char *)items_end; } +/* + * compare two keys in a memcmp fashion + */ int comp_keys(struct key *k1, struct key *k2) { if (k1->objectid > k2->objectid) @@ -52,6 +65,16 @@ int comp_keys(struct key *k1, struct key *k2) return -1; return 0; } + +/* + * search for key in the array p. items p are item_size apart + * and there are 'max' items in p + * the slot in the array is returned via slot, and it points to + * the place where you would insert key if it is not found in + * the array. + * + * slot may point to max if the key is bigger than all of the keys + */ int generic_bin_search(char *p, int item_size, struct key *key, int max, int *slot) { @@ -92,6 +115,14 @@ int bin_search(struct node *c, struct key *key, int *slot) return -1; } +/* + * look for key in the tree. path is filled in with nodes along the way + * if key is found, we return zero and you can find the item in the leaf + * level of the path (level 0) + * + * If the key isn't found, the path points to the slot where it should + * be inserted. + */ int search_slot(struct ctree_root *root, struct key *key, struct ctree_path *p) { struct tree_buffer *b = root->node; @@ -120,12 +151,18 @@ int search_slot(struct ctree_root *root, struct key *key, struct ctree_path *p) return -1; } +/* + * adjust the pointers going up the tree, starting at level + * making sure the right key of each node is points to 'key'. + * This is used after shifting pointers to the left, so it stops + * fixing up pointers when a given leaf/node is not in slot 0 of the + * higher levels + */ static void fixup_low_keys(struct ctree_root *root, struct ctree_path *path, struct key *key, int level) { int i; - /* adjust the pointers going up the tree */ for (i = level; i < MAX_LEVEL; i++) { struct node *t; int tslot = path->slots[i]; @@ -139,64 +176,16 @@ static void fixup_low_keys(struct ctree_root *root, } } -int __insert_ptr(struct ctree_root *root, - struct ctree_path *path, struct key *key, - u64 blocknr, int slot, int level) -{ - struct node *c; - struct node *lower; - struct key *lower_key; - int nritems; - /* need a new root */ - if (!path->nodes[level]) { - struct tree_buffer *t; - t = alloc_free_block(root); - c = &t->node; - memset(c, 0, sizeof(c)); - c->header.nritems = 2; - c->header.flags = node_level(level); - c->header.blocknr = t->blocknr; - lower = &path->nodes[level-1]->node; - if (is_leaf(lower->header.flags)) - lower_key = &((struct leaf *)lower)->items[0].key; - else - lower_key = lower->keys; - memcpy(c->keys, lower_key, sizeof(struct key)); - memcpy(c->keys + 1, key, sizeof(struct key)); - c->blockptrs[0] = path->nodes[level-1]->blocknr; - c->blockptrs[1] = blocknr; - /* the path has an extra ref to root->node */ - tree_block_release(root, root->node); - root->node = t; - t->count++; - write_tree_block(root, t); - path->nodes[level] = t; - path->slots[level] = 0; - if (c->keys[1].objectid == 0) - BUG(); - return 0; - } - lower = &path->nodes[level]->node; - nritems = lower->header.nritems; - if (slot > nritems) - BUG(); - if (nritems == NODEPTRS_PER_BLOCK) - BUG(); - if (slot != nritems) { - memmove(lower->keys + slot + 1, lower->keys + slot, - (nritems - slot) * sizeof(struct key)); - memmove(lower->blockptrs + slot + 1, lower->blockptrs + slot, - (nritems - slot) * sizeof(u64)); - } - memcpy(lower->keys + slot, key, sizeof(struct key)); - lower->blockptrs[slot] = blocknr; - lower->header.nritems++; - if (lower->keys[1].objectid == 0) - BUG(); - write_tree_block(root, path->nodes[level]); - return 0; -} - +/* + * 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. + */ int push_node_left(struct ctree_root *root, struct ctree_path *path, int level) { int slot; @@ -259,6 +248,16 @@ int push_node_left(struct ctree_root *root, struct ctree_path *path, int level) return 0; } +/* + * try to push data from one node into the next node right 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. + */ int push_node_right(struct ctree_root *root, struct ctree_path *path, int level) { int slot; @@ -270,8 +269,11 @@ int push_node_right(struct ctree_root *root, struct ctree_path *path, int level) int dst_nritems; int src_nritems; + /* can't push from the root */ if (level == MAX_LEVEL - 1 || path->nodes[level + 1] == 0) return 1; + + /* only try to push inside the node higher up */ slot = path->slots[level + 1]; if (slot == NODEPTRS_PER_BLOCK - 1) return 1; @@ -315,7 +317,7 @@ int push_node_right(struct ctree_root *root, struct ctree_path *path, int level) write_tree_block(root, t); write_tree_block(root, src_buffer); - /* then fixup the leaf pointer in the path */ + /* then fixup the pointers in the path */ if (path->slots[level] >= src->header.nritems) { path->slots[level] -= src->header.nritems; tree_block_release(root, path->nodes[level]); @@ -327,6 +329,76 @@ int push_node_right(struct ctree_root *root, struct ctree_path *path, int level) return 0; } +/* + * worker function to insert a single pointer in a node. + * the node should have enough room for the pointer already + * slot and level indicate where you want the key to go, and + * blocknr is the block the key points to. + */ +int __insert_ptr(struct ctree_root *root, + struct ctree_path *path, struct key *key, + u64 blocknr, int slot, int level) +{ + struct node *c; + struct node *lower; + struct key *lower_key; + int nritems; + /* need a new root */ + if (!path->nodes[level]) { + struct tree_buffer *t; + t = alloc_free_block(root); + c = &t->node; + memset(c, 0, sizeof(c)); + c->header.nritems = 2; + c->header.flags = node_level(level); + c->header.blocknr = t->blocknr; + lower = &path->nodes[level-1]->node; + if (is_leaf(lower->header.flags)) + lower_key = &((struct leaf *)lower)->items[0].key; + else + lower_key = lower->keys; + memcpy(c->keys, lower_key, sizeof(struct key)); + memcpy(c->keys + 1, key, sizeof(struct key)); + c->blockptrs[0] = path->nodes[level-1]->blocknr; + c->blockptrs[1] = blocknr; + /* the path has an extra ref to root->node */ + tree_block_release(root, root->node); + root->node = t; + t->count++; + write_tree_block(root, t); + path->nodes[level] = t; + path->slots[level] = 0; + if (c->keys[1].objectid == 0) + BUG(); + return 0; + } + lower = &path->nodes[level]->node; + nritems = lower->header.nritems; + if (slot > nritems) + BUG(); + if (nritems == NODEPTRS_PER_BLOCK) + BUG(); + if (slot != nritems) { + memmove(lower->keys + slot + 1, lower->keys + slot, + (nritems - slot) * sizeof(struct key)); + memmove(lower->blockptrs + slot + 1, lower->blockptrs + slot, + (nritems - slot) * sizeof(u64)); + } + memcpy(lower->keys + slot, key, sizeof(struct key)); + lower->blockptrs[slot] = blocknr; + lower->header.nritems++; + if (lower->keys[1].objectid == 0) + BUG(); + write_tree_block(root, path->nodes[level]); + return 0; +} + + +/* + * insert a key,blocknr pair into the tree at a given level + * If the node at that level in the path doesn't have room, + * it is split or shifted as appropriate. + */ int insert_ptr(struct ctree_root *root, struct ctree_path *path, struct key *key, u64 blocknr, int level) @@ -340,6 +412,15 @@ int insert_ptr(struct ctree_root *root, int mid; int bal_start = -1; + /* + * check to see if we need to make room in the node for this + * pointer. If we do, keep walking the tree, making sure there + * is enough room in each level for the required insertions. + * + * The bal array is filled in with any nodes to be inserted + * due to splitting. Once we've done all the splitting required + * do the inserts based on the data in the bal array. + */ memset(bal, 0, ARRAY_SIZE(bal)); while(t && t->node.header.nritems == NODEPTRS_PER_BLOCK) { c = &t->node; @@ -373,6 +454,11 @@ int insert_ptr(struct ctree_root *root, bal_level += 1; t = path->nodes[bal_level]; } + /* + * bal_start tells us the first level in the tree that needed to + * be split. Go through the bal array inserting the new nodes + * as needed. The path is fixed as we go. + */ while(bal_start > 0) { b_buffer = bal[bal_start]; c = &path->nodes[bal_start]->node; @@ -390,10 +476,16 @@ int insert_ptr(struct ctree_root *root, if (!bal[bal_start]) break; } + /* Now that the tree has room, insert the requested pointer */ return __insert_ptr(root, path, key, blocknr, path->slots[level] + 1, level); } +/* + * how many bytes are required to store the items in a leaf. start + * and nr indicate which items in the leaf to check. This totals up the + * space used both by the item structs and the item data + */ int leaf_space_used(struct leaf *l, int start, int nr) { int data_len; @@ -407,6 +499,10 @@ int leaf_space_used(struct leaf *l, int start, int nr) return data_len; } +/* + * push some data in the path leaf to the left, trying to free up at + * least data_size bytes. returns zero if the push worked, nonzero otherwise + */ int push_leaf_left(struct ctree_root *root, struct ctree_path *path, int data_size) { @@ -498,6 +594,10 @@ int push_leaf_left(struct ctree_root *root, struct ctree_path *path, return 0; } +/* + * split the path's leaf in two, making sure there is at least data_size + * available for the resulting leaf level of the path. + */ int split_leaf(struct ctree_root *root, struct ctree_path *path, int data_size) { struct tree_buffer *l_buf = path->nodes[0]; @@ -548,9 +648,10 @@ int split_leaf(struct ctree_root *root, struct ctree_path *path, int data_size) l->data + leaf_data_end(l), data_copy_size); rt_data_off = LEAF_DATA_SIZE - (l->items[mid].offset + l->items[mid].size); - for (i = 0; i < right->header.nritems; i++) { + + for (i = 0; i < right->header.nritems; i++) right->items[i].offset += rt_data_off; - } + l->header.nritems = mid; ret = insert_ptr(root, path, &right->items[0].key, right_buffer->blocknr, 1); @@ -570,6 +671,10 @@ int split_leaf(struct ctree_root *root, struct ctree_path *path, int data_size) return ret; } +/* + * Given a key and some data, insert an item into the tree. + * This does all the path init required, making room in the tree if needed. + */ int insert_item(struct ctree_root *root, struct key *key, void *data, int data_size) { @@ -582,6 +687,7 @@ int insert_item(struct ctree_root *root, struct key *key, unsigned int data_end; struct ctree_path path; + /* create a root if there isn't one */ if (!root->node) { struct tree_buffer *t; t = alloc_free_block(root); @@ -602,6 +708,8 @@ int insert_item(struct ctree_root *root, struct key *key, slot_orig = path.slots[0]; leaf_buf = path.nodes[0]; leaf = &leaf_buf->leaf; + + /* make room if needed */ if (leaf_free_space(leaf) < sizeof(struct item) + data_size) { split_leaf(root, &path, data_size); leaf_buf = path.nodes[0]; @@ -638,6 +746,7 @@ int insert_item(struct ctree_root *root, struct key *key, data_end, old_data - data_end); data_end = old_data; } + /* copy the new data in */ memcpy(&leaf->items[slot].key, key, sizeof(struct key)); leaf->items[slot].offset = data_end - data_size; leaf->items[slot].size = data_size; @@ -650,6 +759,14 @@ int insert_item(struct ctree_root *root, struct key *key, return 0; } +/* + * delete the pointer from a given level in the path. The path is not + * fixed up, so after calling this it is not valid at that level. + * + * If the delete empties a node, the node is removed from the tree, + * continuing all the way the root if required. The root is converted into + * a leaf if all the nodes are emptied. + */ int del_ptr(struct ctree_root *root, struct ctree_path *path, int level) { int slot; @@ -705,6 +822,10 @@ int del_ptr(struct ctree_root *root, struct ctree_path *path, int level) return 0; } +/* + * delete the item at the leaf level in path. If that empties + * the leaf, remove it from the tree + */ int del_item(struct ctree_root *root, struct ctree_path *path) { int slot; @@ -732,6 +853,7 @@ int del_item(struct ctree_root *root, struct ctree_path *path) (leaf->header.nritems - slot - 1)); } leaf->header.nritems -= 1; + /* delete the leaf if we've emptied it */ if (leaf->header.nritems == 0) { if (leaf_buf == root->node) { leaf->header.flags = node_level(0); @@ -742,6 +864,7 @@ int del_item(struct ctree_root *root, struct ctree_path *path) if (slot == 0) fixup_low_keys(root, path, &leaf->items[0].key, 1); write_tree_block(root, leaf_buf); + /* delete the leaf if it is mostly empty */ if (leaf_space_used(leaf, 0, leaf->header.nritems) < LEAF_DATA_SIZE / 4) { /* push_leaf_left fixes the path. @@ -837,7 +960,7 @@ int main() { int i; int num; int ret; - int run_size = 1000000; + int run_size = 25000; int max_key = 100000000; int tree_size = 0; struct ctree_path path; |