tree c0b10a7287ac810bfc406541e32b850ad4580248
parent 3f3420df505e47751ef76a652b5cb660e5360d6f
author Chris Mason <chris.mason@oracle.com> 1234465785 -0500
committer Chris Mason <chris.mason@oracle.com> 1234465785 -0500

Btrfs: make a lockdep class for the extent buffer locks

Btrfs is currently using spin_lock_nested with a nested value based
on the tree depth of the block.  But, this doesn't quite work because
the max tree depth is bigger than what spin_lock_nested can deal with,
and because locks are sometimes taken before the level field is filled in.

The solution here is to use lockdep_set_class_and_name instead, and to
set the class before unlocking the pages when the block is read from the
disk and just after init of a freshly allocated tree block.

btrfs_clear_path_blocking is also changed to take the locks in the proper
order, and it also makes sure all the locks currently held are properly
set to blocking before it tries to retake the spinlocks.  Otherwise, lockdep
gets upset about bad lock orderin.

The lockdep magic cam from Peter Zijlstra <peterz@infradead.org>

Signed-off-by: Chris Mason <chris.mason@oracle.com>