Btrfs: Online btree defragmentation fixes
The btree defragger wasn't making forward progress because the new key wasn't
being saved by the btrfs_search_forward function.
This also disables the automatic btree defrag, it wasn't scaling well to
huge filesystems. The auto-defrag needs to be done differently.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index 7f4cc2b..0cb80f3 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -63,10 +63,9 @@
void btrfs_release_path(struct btrfs_root *root, struct btrfs_path *p)
{
int i;
- int keep = p->keep_locks;
- int skip = p->skip_locking;
for (i = 0; i < BTRFS_MAX_LEVEL; i++) {
+ p->slots[i] = 0;
if (!p->nodes[i])
continue;
if (p->locks[i]) {
@@ -74,10 +73,8 @@
p->locks[i] = 0;
}
free_extent_buffer(p->nodes[i]);
+ p->nodes[i] = NULL;
}
- memset(p, 0, sizeof(*p));
- p->keep_locks = keep;
- p->skip_locking = skip;
}
struct extent_buffer *btrfs_root_node(struct btrfs_root *root)
@@ -463,8 +460,6 @@
search_start = cur->start;
last_block = cur->start;
*last_ret = search_start;
- if (parent_level == 1)
- btrfs_clear_buffer_defrag(cur);
btrfs_tree_unlock(cur);
free_extent_buffer(cur);
}
@@ -2969,8 +2964,138 @@
return 1;
}
+/*
+ * A helper function to walk down the tree starting at min_key, and looking
+ * for nodes or leaves that are either in cache or have a minimum
+ * transaction id. This is used by the btree defrag code, but could
+ * also be used to search for blocks that have changed since a given
+ * transaction id.
+ *
+ * This does not cow, but it does stuff the starting key it finds back
+ * into min_key, so you can call btrfs_search_slot with cow=1 on the
+ * key and get a writable path.
+ *
+ * This does lock as it descends, and path->keep_locks should be set
+ * to 1 by the caller.
+ *
+ * This honors path->lowest_level to prevent descent past a given level
+ * of the tree.
+ *
+ * returns zero if something useful was found, < 0 on error and 1 if there
+ * was nothing in the tree that matched the search criteria.
+ */
+int btrfs_search_forward(struct btrfs_root *root, struct btrfs_key *min_key,
+ struct btrfs_path *path, int cache_only,
+ u64 min_trans)
+{
+ struct extent_buffer *cur;
+ struct btrfs_key found_key;
+ int slot;
+ u32 nritems;
+ int level;
+ int ret = 1;
+
+again:
+ cur = btrfs_lock_root_node(root);
+ level = btrfs_header_level(cur);
+ path->nodes[level] = cur;
+ path->locks[level] = 1;
+
+ if (btrfs_header_generation(cur) < min_trans) {
+ ret = 1;
+ goto out;
+ }
+ while(1) {
+ nritems = btrfs_header_nritems(cur);
+ level = btrfs_header_level(cur);
+ bin_search(cur, min_key, level, &slot);
+
+ /* at level = 0, we're done, setup the path and exit */
+ if (level == 0) {
+ ret = 0;
+ path->slots[level] = slot;
+ btrfs_item_key_to_cpu(cur, &found_key, slot);
+ goto out;
+ }
+ /*
+ * check this node pointer against the cache_only and
+ * min_trans parameters. If it isn't in cache or is too
+ * old, skip to the next one.
+ */
+ while(slot < nritems) {
+ u64 blockptr;
+ u64 gen;
+ struct extent_buffer *tmp;
+ blockptr = btrfs_node_blockptr(cur, slot);
+ gen = btrfs_node_ptr_generation(cur, slot);
+ if (gen < min_trans) {
+ slot++;
+ continue;
+ }
+ if (!cache_only)
+ break;
+
+ tmp = btrfs_find_tree_block(root, blockptr,
+ btrfs_level_size(root, level - 1));
+
+ if (tmp && btrfs_buffer_uptodate(tmp, gen)) {
+ free_extent_buffer(tmp);
+ break;
+ }
+ if (tmp)
+ free_extent_buffer(tmp);
+ slot++;
+ }
+ /*
+ * we didn't find a candidate key in this node, walk forward
+ * and find another one
+ */
+ if (slot >= nritems) {
+ ret = btrfs_find_next_key(root, path, min_key, level,
+ cache_only, min_trans);
+ if (ret == 0) {
+ btrfs_release_path(root, path);
+ goto again;
+ } else {
+ goto out;
+ }
+ }
+ /* save our key for returning back */
+ btrfs_node_key_to_cpu(cur, &found_key, slot);
+ path->slots[level] = slot;
+ if (level == path->lowest_level) {
+ ret = 0;
+ unlock_up(path, level, 1);
+ goto out;
+ }
+ cur = read_node_slot(root, cur, slot);
+
+ btrfs_tree_lock(cur);
+ path->locks[level - 1] = 1;
+ path->nodes[level - 1] = cur;
+ unlock_up(path, level, 1);
+ }
+out:
+ if (ret == 0)
+ memcpy(min_key, &found_key, sizeof(found_key));
+ return ret;
+}
+
+/*
+ * this is similar to btrfs_next_leaf, but does not try to preserve
+ * and fixup the path. It looks for and returns the next key in the
+ * tree based on the current path and the cache_only and min_trans
+ * parameters.
+ *
+ * 0 is returned if another key is found, < 0 if there are any errors
+ * and 1 is returned if there are no higher keys in the tree
+ *
+ * path->keep_locks should be set to 1 on the search made before
+ * calling this function.
+ */
int btrfs_find_next_key(struct btrfs_root *root, struct btrfs_path *path,
- struct btrfs_key *key, int lowest_level)
+ struct btrfs_key *key, int lowest_level,
+ int cache_only, u64 min_trans)
{
int level = lowest_level;
int slot;
@@ -2982,6 +3107,7 @@
slot = path->slots[level] + 1;
c = path->nodes[level];
+next:
if (slot >= btrfs_header_nritems(c)) {
level++;
if (level == BTRFS_MAX_LEVEL) {
@@ -2991,8 +3117,28 @@
}
if (level == 0)
btrfs_item_key_to_cpu(c, key, slot);
- else
+ else {
+ u64 blockptr = btrfs_node_blockptr(c, slot);
+ u64 gen = btrfs_node_ptr_generation(c, slot);
+
+ if (cache_only) {
+ struct extent_buffer *cur;
+ cur = btrfs_find_tree_block(root, blockptr,
+ btrfs_level_size(root, level - 1));
+ if (!cur || !btrfs_buffer_uptodate(cur, gen)) {
+ slot++;
+ if (cur)
+ free_extent_buffer(cur);
+ goto next;
+ }
+ free_extent_buffer(cur);
+ }
+ if (gen < min_trans) {
+ slot++;
+ goto next;
+ }
btrfs_node_key_to_cpu(c, key, slot);
+ }
return 0;
}
return 1;
@@ -3095,6 +3241,12 @@
return 0;
}
+/*
+ * this uses btrfs_prev_leaf to walk backwards in the tree, and keeps
+ * searching until it gets past min_objectid or finds an item of 'type'
+ *
+ * returns 0 if something is found, 1 if nothing was found and < 0 on error
+ */
int btrfs_previous_item(struct btrfs_root *root,
struct btrfs_path *path, u64 min_objectid,
int type)