Commit 0b530bc5 authored by Josef Bacik's avatar Josef Bacik Committed by David Sterba
Browse files

btrfs: hold a ref on the root in build_backref_tree 



This is trickier than the previous conversions.  We have backref_node's
that need to hold onto their root for their lifetime.  Do the read of
the root and grab the ref.  If at any point we don't use the root we
discard it, however if we use it in our backref node we don't free it
until we free the backref node.  Any time we switch the root's for the
backref node we need to drop our ref on the old root and grab the ref on
the new root, and if we dupe a node we need to get a ref on the root
there as well.

Signed-off-by: default avatarJosef Bacik <josef@toxicpanda.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent 2a2b5d62

fs/btrfs/relocation.c

+29 −9
Original line number Diff line number Diff line
@@ -303,6 +303,7 @@ static void free_backref_node(struct backref_cache *cache, 
{

	if (node) {

		cache->nr_nodes--;

		btrfs_put_fs_root(node->root);

		kfree(node);

	}

}
@@ -636,7 +637,7 @@ static struct btrfs_root *find_reloc_root(struct reloc_control *rc, 
		root = (struct btrfs_root *)node->data;

	}

	spin_unlock(&rc->reloc_root_tree.lock);

	return root;

	return btrfs_grab_fs_root(root);

}



static int is_cowonly_root(u64 root_objectid)
@@ -938,6 +939,10 @@ again: 
			err = PTR_ERR(root);

			goto out;

		}

		if (!btrfs_grab_fs_root(root)) {

			err = -ENOENT;

			goto out;

		}



		if (!test_bit(BTRFS_ROOT_REF_COWS, &root->state))

			cur->cowonly = 1;
@@ -946,10 +951,12 @@ again: 
			/* tree root */

			ASSERT(btrfs_root_bytenr(&root->root_item) ==

			       cur->bytenr);

			if (should_ignore_root(root))

			if (should_ignore_root(root)) {

				btrfs_put_fs_root(root);

				list_add(&cur->list, &useless);

			else

			} else {

				cur->root = root;

			}

			break;

		}
@@ -962,6 +969,7 @@ again: 
		ret = btrfs_search_slot(NULL, root, node_key, path2, 0, 0);

		path2->lowest_level = 0;

		if (ret < 0) {

			btrfs_put_fs_root(root);

			err = ret;

			goto out;

		}
@@ -977,6 +985,7 @@ again: 
				  root->root_key.objectid,

				  node_key->objectid, node_key->type,

				  node_key->offset);

			btrfs_put_fs_root(root);

			err = -ENOENT;

			goto out;

		}
@@ -988,15 +997,18 @@ again: 
			if (!path2->nodes[level]) {

				ASSERT(btrfs_root_bytenr(&root->root_item) ==

				       lower->bytenr);

				if (should_ignore_root(root))

				if (should_ignore_root(root)) {

					btrfs_put_fs_root(root);

					list_add(&lower->list, &useless);

				else

				} else {

					lower->root = root;

				}

				break;

			}



			edge = alloc_backref_edge(cache);

			if (!edge) {

				btrfs_put_fs_root(root);

				err = -ENOMEM;

				goto out;

			}
@@ -1006,6 +1018,7 @@ again: 
			if (!rb_node) {

				upper = alloc_backref_node(cache);

				if (!upper) {

					btrfs_put_fs_root(root);

					free_backref_edge(cache, edge);

					err = -ENOMEM;

					goto out;
@@ -1053,8 +1066,10 @@ again: 
			edge->node[LOWER] = lower;

			edge->node[UPPER] = upper;



			if (rb_node)

			if (rb_node) {

				btrfs_put_fs_root(root);

				break;

			}

			lower = upper;

			upper = NULL;

		}
@@ -1291,7 +1306,8 @@ static int clone_backref_node(struct btrfs_trans_handle *trans, 
	new_node->level = node->level;

	new_node->lowest = node->lowest;

	new_node->checked = 1;

	new_node->root = dest;

	new_node->root = btrfs_grab_fs_root(dest);

	ASSERT(new_node->root);



	if (!node->lowest) {

		list_for_each_entry(edge, &node->lower, list[UPPER]) {
@@ -2669,7 +2685,9 @@ struct btrfs_root *select_reloc_root(struct btrfs_trans_handle *trans, 
			BUG_ON(next->new_bytenr);

			BUG_ON(!list_empty(&next->list));

			next->new_bytenr = root->node->start;

			next->root = root;

			btrfs_put_fs_root(next->root);

			next->root = btrfs_grab_fs_root(root);

			ASSERT(next->root);

			list_add_tail(&next->list,

				      &rc->backref_cache.changed);

			__mark_block_processed(rc, next);
@@ -3141,7 +3159,9 @@ static int relocate_tree_block(struct btrfs_trans_handle *trans, 
			btrfs_record_root_in_trans(trans, root);

			root = root->reloc_root;

			node->new_bytenr = root->node->start;

			node->root = root;

			btrfs_put_fs_root(node->root);

			node->root = btrfs_grab_fs_root(root);

			ASSERT(node->root);

			list_add_tail(&node->list, &rc->backref_cache.changed);

		} else {

			path->lowest_level = node->level;

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