Btrfs: Use mutex_lock_nested for tree locking (6dddcbeb) · Commits · 戴 / test

Lockdep has the notion of locking subclasses so that you can identify locks you expect to be taken after other locks of the same class. This changes the per-extent buffer btree locking routines to use a subclass based on the level in the tree. Unfortunately, lockdep can only handle 8 total subclasses, and the btrfs max level is also 8. So when lockdep is on, use a lower max level. Signed-off-by:

Chris Mason <chris.mason@oracle.com>

fs/btrfs/ctree.h

+5 −1

Original line number	Diff line number	Diff line
		@@ -42,7 +42,11 @@ struct btrfs_ordered_sum;

		#define BTRFS_MAGIC "_B5RfS_M"

		#ifdef CONFIG_LOCKDEP
		# define BTRFS_MAX_LEVEL 7
		#else
		# define BTRFS_MAX_LEVEL 8
		#endif

		/* holds pointers to all of the tree roots */
		#define BTRFS_ROOT_TREE_OBJECTID 1ULL

fs/btrfs/locking.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -37,7 +37,7 @@ int btrfs_tree_lock(struct extent_buffer *eb)
		return 0;
		}
		cpu_relax();
		mutex_lock(&eb->mutex);
		mutex_lock_nested(&eb->mutex, BTRFS_MAX_LEVEL - btrfs_header_level(eb));
		return 0;
		}

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