}
/*
- * helper function for btrfs_search_slot. The goal is to find a block
- * in cache without setting the path to blocking. If we find the block
- * we return zero and the path is unchanged.
+ * Helper function for btrfs_search_slot() and other functions that do a search
+ * on a btree. The goal is to find a tree block in the cache (the radix tree at
+ * fs_info->buffer_radix), but if we can't find it, or it's not up to date, read
+ * its pages from disk.
*
- * If we can't find the block, we set the path blocking and do some
- * reada. -EAGAIN is returned and the search must be repeated.
+ * Returns -EAGAIN, with the path unlocked, if the caller needs to repeat the
+ * whole btree search, starting again from the current root node.
*/
static int
read_block_for_search(struct btrfs_root *root, struct btrfs_path *p,
struct btrfs_key first_key;
int ret;
int parent_level;
+ bool unlock_up;
+ unlock_up = ((level + 1 < BTRFS_MAX_LEVEL) && p->locks[level + 1]);
blocknr = btrfs_node_blockptr(*eb_ret, slot);
gen = btrfs_node_ptr_generation(*eb_ret, slot);
parent_level = btrfs_header_level(*eb_ret);
btrfs_node_key_to_cpu(*eb_ret, &first_key, slot);
+ /*
+ * If we need to read an extent buffer from disk and we are holding locks
+ * on upper level nodes, we unlock all the upper nodes before reading the
+ * extent buffer, and then return -EAGAIN to the caller as it needs to
+ * restart the search. We don't release the lock on the current level
+ * because we need to walk this node to figure out which blocks to read.
+ */
tmp = find_extent_buffer(fs_info, blocknr);
if (tmp) {
if (p->reada == READA_FORWARD_ALWAYS)
return 0;
}
+ if (unlock_up)
+ btrfs_unlock_up_safe(p, level + 1);
+
/* now we're allowed to do a blocking uptodate check */
ret = btrfs_read_buffer(tmp, gen, parent_level - 1, &first_key);
if (ret) {
btrfs_release_path(p);
return -EIO;
}
- *eb_ret = tmp;
- return 0;
+
+ if (unlock_up)
+ ret = -EAGAIN;
+
+ goto out;
}
- /*
- * reduce lock contention at high levels
- * of the btree by dropping locks before
- * we read. Don't release the lock on the current
- * level because we need to walk this node to figure
- * out which blocks to read.
- */
- btrfs_unlock_up_safe(p, level + 1);
+ if (unlock_up) {
+ btrfs_unlock_up_safe(p, level + 1);
+ ret = -EAGAIN;
+ } else {
+ ret = 0;
+ }
if (p->reada != READA_NONE)
reada_for_search(fs_info, p, level, slot, key->objectid);
- ret = -EAGAIN;
tmp = read_tree_block(fs_info, blocknr, root->root_key.objectid,
gen, parent_level - 1, &first_key);
if (IS_ERR(tmp)) {
*/
if (!extent_buffer_uptodate(tmp))
ret = -EIO;
- free_extent_buffer(tmp);
- btrfs_release_path(p);
+out:
+ if (ret == 0) {
+ *eb_ret = tmp;
+ } else {
+ free_extent_buffer(tmp);
+ btrfs_release_path(p);
+ }
+
return ret;
}