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Btrfs: Fold some btree readahead routines into something more generic.

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Signed-off-by: Chris Mason <chris.mason@oracle.com>
This commit is contained in:
Chris Mason
2007-08-07 15:52:22 -04:00
committed by David Woodhouse
parent 9f3a742736
commit 3c69faecb8
4 changed files with 81 additions and 96 deletions
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77
fs/btrfs/ctree.c
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@@ -639,6 +639,73 @@ static int push_nodes_for_insert(struct btrfs_trans_handle *trans,
return 1;
}
/*
* readahead one full node of leaves
*/
static void reada_for_search(struct btrfs_root *root, struct btrfs_path *path,
int slot)
{
struct btrfs_node *node;
int i;
u32 nritems;
u64 item_objectid;
u64 blocknr;
u64 search;
u64 cluster_start;
int ret;
int nread = 0;
int direction = path->reada;
struct radix_tree_root found;
unsigned long gang[8];
struct buffer_head *bh;
if (!path->nodes[1])
return;
node = btrfs_buffer_node(path->nodes[1]);
search = btrfs_node_blockptr(node, slot);
bh = btrfs_find_tree_block(root, search);
if (bh) {
brelse(bh);
return;
}
init_bit_radix(&found);
nritems = btrfs_header_nritems(&node->header);
for (i = slot; i < nritems; i++) {
item_objectid = btrfs_disk_key_objectid(&node->ptrs[i].key);
blocknr = btrfs_node_blockptr(node, i);
set_radix_bit(&found, blocknr);
}
if (direction > 0) {
cluster_start = search - 4;
if (cluster_start > search)
cluster_start = 0;
} else
cluster_start = search + 4;
while(1) {
ret = find_first_radix_bit(&found, gang, 0, ARRAY_SIZE(gang));
if (!ret)
break;
for (i = 0; i < ret; i++) {
blocknr = gang[i];
clear_radix_bit(&found, blocknr);
if (nread > 64)
continue;
if (direction > 0 && cluster_start <= blocknr &&
cluster_start + 8 > blocknr) {
cluster_start = blocknr;
readahead_tree_block(root, blocknr);
nread++;
} else if (direction < 0 && cluster_start >= blocknr &&
blocknr + 8 > cluster_start) {
cluster_start = blocknr;
readahead_tree_block(root, blocknr);
nread++;
}
}
}
}
/*
* 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
@@ -660,9 +727,11 @@ int btrfs_search_slot(struct btrfs_trans_handle *trans, struct btrfs_root
struct buffer_head *cow_buf;
struct btrfs_node *c;
struct btrfs_root_item *root_item = &root->root_item;
u64 blocknr;
int slot;
int ret;
int level;
int should_reada = p->reada;
u8 lowest_level = 0;
if (btrfs_root_refs(root_item) == 0 && root->ref_cows) {
@@ -728,7 +797,11 @@ again:
/* this is only true while dropping a snapshot */
if (level == lowest_level)
break;
blocknr = btrfs_node_blockptr(c, slot);
if (level == 1 && should_reada)
reada_for_search(root, p, slot);
b = read_tree_block(root, btrfs_node_blockptr(c, slot));
} else {
struct btrfs_leaf *l = (struct btrfs_leaf *)c;
p->slots[level] = slot;
@@ -1915,6 +1988,8 @@ int btrfs_next_leaf(struct btrfs_root *root, struct btrfs_path *path)
blocknr = btrfs_node_blockptr(c_node, slot);
if (next)
btrfs_block_release(root, next);
if (level == 1 && path->reada)
reada_for_search(root, path, slot);
next = read_tree_block(root, blocknr);
break;
}
@@ -1927,6 +2002,8 @@ int btrfs_next_leaf(struct btrfs_root *root, struct btrfs_path *path)
path->slots[level] = 0;
if (!level)
break;
if (level == 1 && path->reada)
reada_for_search(root, path, slot);
next = read_tree_block(root,
btrfs_node_blockptr(btrfs_buffer_node(next), 0));
}