btrfs: introduce BTRFS_NESTING_LEFT/RIGHT_COW
For similar reasons as BTRFS_NESTING_COW, we need
BTRFS_NESTING_LEFT/RIGHT_COW. The pattern is this
lock leaf -> BTRFS_NESTING_NORMAL
cow leaf -> BTRFS_NESTING_COW
split leaf
lock left -> BTRFS_NESTING_LEFT
cow left -> BTRFS_NESTING_LEFT_COW
We need this in order to indicate to lockdep that these locks are
discrete and are being taken in a safe order.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
diff --git a/fs/btrfs/locking.h b/fs/btrfs/locking.h
index 5844bc1..16563bc 100644
--- a/fs/btrfs/locking.h
+++ b/fs/btrfs/locking.h
@@ -45,6 +45,14 @@ enum btrfs_lock_nesting {
BTRFS_NESTING_RIGHT,
/*
+ * When splitting we will be holding a lock on the left/right node when
+ * we need to cow that node, thus we need a new set of subclasses for
+ * these two operations.
+ */
+ BTRFS_NESTING_LEFT_COW,
+ BTRFS_NESTING_RIGHT_COW,
+
+ /*
* 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
* the limit. As of this writing we're limited to 8, and we're