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Commit 74123bd7 authored by Chris Mason's avatar Chris Mason Committed by David Woodhouse
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Btrfs: Commenting/cleanup 

Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
parent eb60ceac
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Showing with 186 additions and 63 deletions
fs/btrfs/ctree.c
View file @ 74123bd7
......@@ -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;
......
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