linux/fs/btrfs/extent-tree.c

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#include <stdio.h>
#include <stdlib.h>
#include "kerncompat.h"
#include "radix-tree.h"
#include "ctree.h"
#include "disk-io.h"
#include "print-tree.h"
/*
* pending extents are blocks that we're trying to allocate in the extent
* map while trying to grow the map because of other allocations. To avoid
* recursing, they are tagged in the radix tree and cleaned up after
* other allocations are done. The pending tag is also used in the same
* manner for deletes.
*/
#define CTREE_EXTENT_PENDING 0
/*
* find all the blocks marked as pending in the radix tree and remove
* them from the extent map
*/
static int del_pending_extents(struct ctree_root *extent_root)
{
int ret;
struct key key;
struct tree_buffer *gang[4];
int i;
struct ctree_path path;
while(1) {
ret = radix_tree_gang_lookup_tag(&extent_root->cache_radix,
(void **)gang, 0,
ARRAY_SIZE(gang),
CTREE_EXTENT_PENDING);
if (!ret)
break;
for (i = 0; i < ret; i++) {
key.objectid = gang[i]->blocknr;
key.flags = 0;
key.offset = 1;
init_path(&path);
ret = search_slot(extent_root, &key, &path, -1);
if (ret) {
print_tree(extent_root, extent_root->node);
printf("unable to find %Lu\n", key.objectid);
BUG();
// FIXME undo it and return sane
return ret;
}
ret = del_item(extent_root, &path);
if (ret) {
BUG();
return ret;
}
release_path(extent_root, &path);
radix_tree_tag_clear(&extent_root->cache_radix,
gang[i]->blocknr,
CTREE_EXTENT_PENDING);
tree_block_release(extent_root, gang[i]);
}
}
return 0;
}
/*
* remove an extent from the root, returns 0 on success
*/
int free_extent(struct ctree_root *root, u64 blocknr, u64 num_blocks)
{
struct ctree_path path;
struct key key;
struct ctree_root *extent_root = root->extent_root;
struct tree_buffer *t;
int pending_ret;
int ret;
key.objectid = blocknr;
key.flags = 0;
key.offset = num_blocks;
if (root == extent_root) {
t = read_tree_block(root, key.objectid);
radix_tree_tag_set(&root->cache_radix, key.objectid,
CTREE_EXTENT_PENDING);
return 0;
}
init_path(&path);
ret = search_slot(extent_root, &key, &path, -1);
if (ret) {
print_tree(extent_root, extent_root->node);
printf("failed to find %Lu\n", key.objectid);
BUG();
}
ret = del_item(extent_root, &path);
if (ret)
BUG();
release_path(extent_root, &path);
pending_ret = del_pending_extents(root->extent_root);
return ret ? ret : pending_ret;
}
/*
* walks the btree of allocated extents and find a hole of a given size.
* The key ins is changed to record the hole:
* ins->objectid == block start
* ins->flags = 0
* ins->offset == number of blocks
* Any available blocks before search_start are skipped.
*/
static int find_free_extent(struct ctree_root *orig_root, u64 num_blocks,
u64 search_start, u64 search_end, struct key *ins)
{
struct ctree_path path;
struct key *key;
int ret;
u64 hole_size = 0;
int slot = 0;
u64 last_block;
int start_found;
struct leaf *l;
struct ctree_root * root = orig_root->extent_root;
check_failed:
init_path(&path);
ins->objectid = search_start;
ins->offset = 0;
ins->flags = 0;
start_found = 0;
ret = search_slot(root, ins, &path, 0);
if (ret < 0)
goto error;
while (1) {
l = &path.nodes[0]->leaf;
slot = path.slots[0];
if (slot >= l->header.nritems) {
ret = next_leaf(root, &path);
if (ret == 0)
continue;
if (ret < 0)
goto error;
if (!start_found) {
ins->objectid = search_start;
ins->offset = num_blocks;
start_found = 1;
goto check_pending;
}
ins->objectid = last_block > search_start ?
last_block : search_start;
ins->offset = num_blocks;
goto check_pending;
}
key = &l->items[slot].key;
if (key->objectid >= search_start) {
if (start_found) {
hole_size = key->objectid - last_block;
if (hole_size > num_blocks) {
ins->objectid = last_block;
ins->offset = num_blocks;
goto check_pending;
}
} else
start_found = 1;
last_block = key->objectid + key->offset;
}
path.slots[0]++;
}
// FIXME -ENOSPC
check_pending:
/* we have to make sure we didn't find an extent that has already
* been allocated by the map tree or the original allocation
*/
release_path(root, &path);
BUG_ON(ins->objectid < search_start);
if (orig_root->extent_root == orig_root) {
BUG_ON(num_blocks != 1);
if ((root->current_insert.objectid <= ins->objectid &&
root->current_insert.objectid +
root->current_insert.offset > ins->objectid) ||
(root->current_insert.objectid > ins->objectid &&
root->current_insert.objectid <= ins->objectid +
ins->offset) ||
radix_tree_tag_get(&root->cache_radix, ins->objectid,
CTREE_EXTENT_PENDING)) {
search_start = ins->objectid + 1;
goto check_failed;
}
}
if (ins->offset != 1)
BUG();
return 0;
error:
release_path(root, &path);
return ret;
}
/*
* insert all of the pending extents reserved during the original
* allocation. (CTREE_EXTENT_PENDING). Returns zero if it all worked out
*/
static int insert_pending_extents(struct ctree_root *extent_root)
{
int ret;
struct key key;
struct extent_item item;
struct tree_buffer *gang[4];
int i;
// FIXME -ENOSPC
item.refs = 1;
item.owner = extent_root->node->node.header.parentid;
while(1) {
ret = radix_tree_gang_lookup_tag(&extent_root->cache_radix,
(void **)gang, 0,
ARRAY_SIZE(gang),
CTREE_EXTENT_PENDING);
if (!ret)
break;
for (i = 0; i < ret; i++) {
key.objectid = gang[i]->blocknr;
key.flags = 0;
key.offset = 1;
ret = insert_item(extent_root, &key, &item,
sizeof(item));
if (ret) {
BUG();
// FIXME undo it and return sane
return ret;
}
radix_tree_tag_clear(&extent_root->cache_radix,
gang[i]->blocknr,
CTREE_EXTENT_PENDING);
tree_block_release(extent_root, gang[i]);
}
}
return 0;
}
/*
* finds a free extent and does all the dirty work required for allocation
* returns the key for the extent through ins, and a tree buffer for
* the first block of the extent through buf.
*
* returns 0 if everything worked, non-zero otherwise.
*/
int alloc_extent(struct ctree_root *root, u64 num_blocks, u64 search_start,
u64 search_end, u64 owner, struct key *ins,
struct tree_buffer **buf)
{
int ret;
int pending_ret;
struct extent_item extent_item;
extent_item.refs = 1;
extent_item.owner = owner;
ret = find_free_extent(root, num_blocks, search_start, search_end, ins);
if (ret)
return ret;
if (root != root->extent_root) {
memcpy(&root->extent_root->current_insert, ins, sizeof(*ins));
ret = insert_item(root->extent_root, ins, &extent_item,
sizeof(extent_item));
memset(&root->extent_root->current_insert, 0,
sizeof(struct key));
pending_ret = insert_pending_extents(root->extent_root);
if (ret)
return ret;
if (pending_ret)
return pending_ret;
*buf = find_tree_block(root, ins->objectid);
return 0;
}
/* we're allocating an extent for the extent tree, don't recurse */
BUG_ON(ins->offset != 1);
*buf = find_tree_block(root, ins->objectid);
BUG_ON(!*buf);
radix_tree_tag_set(&root->cache_radix, ins->objectid,
CTREE_EXTENT_PENDING);
(*buf)->count++;
return 0;
}
/*
* helper function to allocate a block for a given tree
* returns the tree buffer or NULL.
*/
struct tree_buffer *alloc_free_block(struct ctree_root *root)
{
struct key ins;
int ret;
struct tree_buffer *buf = NULL;
ret = alloc_extent(root, 1, 0, (unsigned long)-1,
root->node->node.header.parentid,
&ins, &buf);
if (ret) {
BUG();
return NULL;
}
if (root != root->extent_root)
BUG_ON(radix_tree_tag_get(&root->extent_root->cache_radix,
buf->blocknr, CTREE_EXTENT_PENDING));
return buf;
}