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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: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Josef Bacik 2020-08-20 11:46:04 -04:00 committed by David Sterba
parent 9631e4cc1a
commit bf77467a93
2 changed files with 20 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
fs/btrfs/ctree.c
View File

@ -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;

12
fs/btrfs/locking.h
View File

@ -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