Re: [PATCH v11 1/4] xfs: Refactor xfs_isilocked()

[Christoph Hellwig <hch@infradead.org>]

On Fri, Oct 09, 2020 at 09:55:12PM +0200, Pavel Reichl wrote:
> Refactor xfs_isilocked() to use newly introduced __xfs_rwsem_islocked().
> __xfs_rwsem_islocked() is a helper function which encapsulates checking
> state of rw_semaphores hold by inode.
> 
> Signed-off-by: Pavel Reichl <preichl@redhat.com>
> Suggested-by: Dave Chinner <dchinner@redhat.com>
> Suggested-by: Eric Sandeen <sandeen@redhat.com>
> Suggested-by: Darrick J. Wong <darrick.wong@oracle.com>
> Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
> ---
>  fs/xfs/xfs_inode.c | 48 ++++++++++++++++++++++++++++++++++++++--------
>  fs/xfs/xfs_inode.h | 21 +++++++++++++-------
>  2 files changed, 54 insertions(+), 15 deletions(-)
> 
> diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
> index c06129cffba9..7c1ceb4df4ec 100644
> --- a/fs/xfs/xfs_inode.c
> +++ b/fs/xfs/xfs_inode.c
> @@ -345,9 +345,43 @@ xfs_ilock_demote(
>  }
>  
>  #if defined(DEBUG) || defined(XFS_WARN)
> -int
> +static inline bool
> +__xfs_rwsem_islocked(
> +	struct rw_semaphore	*rwsem,
> +	int			lock_flags)
> +{
> +	int			arg;
> +
> +	if (!debug_locks)
> +		return rwsem_is_locked(rwsem);
> +
> +	if (lock_flags & (1 << XFS_SHARED_LOCK_SHIFT)) {
> +		/*
> +		 * The caller could be asking if we have (shared | excl)
> +		 * access to the lock. Ask lockdep if the rwsem is
> +		 * locked either for read or write access.
> +		 *
> +		 * The caller could also be asking if we have only
> +		 * shared access to the lock. Holding a rwsem
> +		 * write-locked implies read access as well, so the
> +		 * request to lockdep is the same for this case.
> +		 */
> +		arg = -1;
> +	} else {
> +		/*
> +		 * The caller is asking if we have only exclusive access
> +		 * to the lock. Ask lockdep if the rwsem is locked for
> +		 * write access.
> +		 */
> +		arg = 0;
> +	}
> +
> +	return lockdep_is_held_type(rwsem, arg);

Why not write this as:

	if (lock_flags & (1 << XFS_SHARED_LOCK_SHIFT)) {
		...
		return lockdep_is_held_type(rwsem, 1);
	}

	...
	return lockdep_is_held_type(rwsem, 0);
}

which seems a lot easier to read compare to the strange arg variable.

Otherwise this looks good to me:

Reviewed-by: Christoph Hellwig <hch@lst.de>