locking/lockdep: Provide a type check for lock_is_held

locking/lockdep: Provide a type check for lock_is_held

Christoph requested lockdep_assert_held() variants that distinguish
between held-for-read or held-for-write.

Provide:

  int lock_is_held_type(struct lockdep_map *lock, int read)

which takes the same argument as lock_acquire(.read) and matches it to
the held_lock instance.

Use of this function should be gated by the debug_locks variable. When
that is 0 the return value of the lock_is_held_type() function is
undefined. This is done to allow both negative and positive tests for
holding locks.

By default we provide (positive) lockdep_assert_held{,_exclusive,_read}()
macros.

Requested-by: Christoph Hellwig <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Tested-by: Jens Axboe <[email protected]>
Reviewed-by: Darrick J. Wong <[email protected]>
Signed-off-by: Dave Chinner <[email protected]>