Commit bf77467a authored by Josef Bacik's avatar Josef Bacik Committed by David Sterba
Browse files

btrfs: introduce BTRFS_NESTING_LEFT/BTRFS_NESTING_RIGHT 



Our lockdep maps are based on rootid+level, however in some cases we
will lock adjacent blocks on the same level, namely in searching forward
or in split/balance.  Because of this lockdep will complain, so we need
a separate subclass to indicate to lockdep that these are different
locks.

lock leaf -> BTRFS_NESTING_NORMAL
  cow leaf -> BTRFS_NESTING_COW
    split leaf
       lock left -> BTRFS_NESTING_LEFT
       lock right -> BTRFS_NESTING_RIGHT

The above graph illustrates the need for this new nesting subclass.

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 9631e4cc

fs/btrfs/ctree.c

+8 −8
Original line number Diff line number Diff line
@@ -1896,7 +1896,7 @@ static noinline int balance_level(struct btrfs_trans_handle *trans, 
		left = NULL;



	if (left) {

		btrfs_tree_lock(left);

		__btrfs_tree_lock(left, BTRFS_NESTING_LEFT);

		btrfs_set_lock_blocking_write(left);

		wret = btrfs_cow_block(trans, root, left,

				       parent, pslot - 1, &left,
@@ -1912,7 +1912,7 @@ static noinline int balance_level(struct btrfs_trans_handle *trans, 
		right = NULL;



	if (right) {

		btrfs_tree_lock(right);

		__btrfs_tree_lock(right, BTRFS_NESTING_RIGHT);

		btrfs_set_lock_blocking_write(right);

		wret = btrfs_cow_block(trans, root, right,

				       parent, pslot + 1, &right,
@@ -2076,7 +2076,7 @@ static noinline int push_nodes_for_insert(struct btrfs_trans_handle *trans, 
	if (left) {

		u32 left_nr;



		btrfs_tree_lock(left);

		__btrfs_tree_lock(left, BTRFS_NESTING_LEFT);

		btrfs_set_lock_blocking_write(left);



		left_nr = btrfs_header_nritems(left);
@@ -2131,7 +2131,7 @@ static noinline int push_nodes_for_insert(struct btrfs_trans_handle *trans, 
	if (right) {

		u32 right_nr;



		btrfs_tree_lock(right);

		__btrfs_tree_lock(right, BTRFS_NESTING_RIGHT);

		btrfs_set_lock_blocking_write(right);



		right_nr = btrfs_header_nritems(right);
@@ -3806,7 +3806,7 @@ static int push_leaf_right(struct btrfs_trans_handle *trans, struct btrfs_root 
	if (IS_ERR(right))

		return 1;



	btrfs_tree_lock(right);

	__btrfs_tree_lock(right, BTRFS_NESTING_RIGHT);

	btrfs_set_lock_blocking_write(right);



	free_space = btrfs_leaf_free_space(right);
@@ -4045,7 +4045,7 @@ static int push_leaf_left(struct btrfs_trans_handle *trans, struct btrfs_root 
	if (IS_ERR(left))

		return 1;



	btrfs_tree_lock(left);

	__btrfs_tree_lock(left, BTRFS_NESTING_LEFT);

	btrfs_set_lock_blocking_write(left);



	free_space = btrfs_leaf_free_space(left);
@@ -5467,7 +5467,7 @@ int btrfs_next_old_leaf(struct btrfs_root *root, struct btrfs_path *path, 
			if (!ret) {

				btrfs_set_path_blocking(path);

				__btrfs_tree_read_lock(next,

						       BTRFS_NESTING_NORMAL,

						       BTRFS_NESTING_RIGHT,

						       path->recurse);

			}

			next_rw_lock = BTRFS_READ_LOCK;
@@ -5504,7 +5504,7 @@ int btrfs_next_old_leaf(struct btrfs_root *root, struct btrfs_path *path, 
			if (!ret) {

				btrfs_set_path_blocking(path);

				__btrfs_tree_read_lock(next,

						       BTRFS_NESTING_NORMAL,

						       BTRFS_NESTING_RIGHT,

						       path->recurse);

			}

			next_rw_lock = BTRFS_READ_LOCK;

fs/btrfs/locking.h

+12 −0
Original line number Diff line number Diff line
@@ -32,6 +32,18 @@ enum btrfs_lock_nesting { 
	 */

	BTRFS_NESTING_COW,



	/*

	 * Oftentimes we need to lock adjacent nodes on the same level while

	 * still holding the lock on the original node we searched to, such as

	 * for searching forward or for split/balance.

	 *

	 * Because of this we need to indicate to lockdep that this is

	 * acceptable by having a different subclass for each of these

	 * operations.

	 */

	BTRFS_NESTING_LEFT,

	BTRFS_NESTING_RIGHT,



	/*

	 * We are limited to MAX_LOCKDEP_SUBLCLASSES number of subclasses, so

	 * add this in here and add a static_assert to keep us from going over