Re: [PATCH v12 1/4] xfs: Refactor xfs_isilocked()

[Brian Foster <bfoster@redhat.com>]

On Fri, Oct 16, 2020 at 04:10:02AM +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>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> ---
>  fs/xfs/xfs_inode.c | 39 +++++++++++++++++++++++++++++++--------
>  fs/xfs/xfs_inode.h | 21 ++++++++++++++-------
>  2 files changed, 45 insertions(+), 15 deletions(-)
> 
> diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
> index c06129cffba9..1fdf8c7eb990 100644
> --- a/fs/xfs/xfs_inode.c
> +++ b/fs/xfs/xfs_inode.c
> @@ -345,9 +345,34 @@ xfs_ilock_demote(
>  }
>  
>  #if defined(DEBUG) || defined(XFS_WARN)
> -int
> +static inline bool
> +__xfs_rwsem_islocked(
> +	struct rw_semaphore	*rwsem,
> +	int			lock_flags,
> +	int			shift)
> +{
> +	lock_flags >>= shift;
> +
> +	if (!debug_locks)
> +		return rwsem_is_locked(rwsem);
> +	/*
> +	 * If the shared flag is not set, pass 0 to explicitly check for
> +	 * exclusive access to the lock. If the shared flag is set, we typically
> +	 * want to make sure the lock is at least held in shared mode
> +	 * (i.e., shared | excl) but we don't necessarily care that it might
> +	 * actually be held exclusive. Therefore, pass -1 to check whether the
> +	 * lock is held in any mode rather than one of the explicit shared mode
> +	 * values (1 or 2)."
> +	 */
> +	if (lock_flags & (1 << XFS_SHARED_LOCK_SHIFT)) {
> +		return lockdep_is_held_type(rwsem, -1);
> +	}

Nit: no need for braces here. Otherwise LGTM. Thanks for the tweaks.

Reviewed-by: Brian Foster <bfoster@redhat.com>

> +	return lockdep_is_held_type(rwsem, 0);
> +}
> +
> +bool
>  xfs_isilocked(
> -	xfs_inode_t		*ip,
> +	struct xfs_inode	*ip,
>  	uint			lock_flags)
>  {
>  	if (lock_flags & (XFS_ILOCK_EXCL|XFS_ILOCK_SHARED)) {
> @@ -362,15 +387,13 @@ xfs_isilocked(
>  		return rwsem_is_locked(&ip->i_mmaplock.mr_lock);
>  	}
>  
> -	if (lock_flags & (XFS_IOLOCK_EXCL|XFS_IOLOCK_SHARED)) {
> -		if (!(lock_flags & XFS_IOLOCK_SHARED))
> -			return !debug_locks ||
> -				lockdep_is_held_type(&VFS_I(ip)->i_rwsem, 0);
> -		return rwsem_is_locked(&VFS_I(ip)->i_rwsem);
> +	if (lock_flags & (XFS_IOLOCK_EXCL | XFS_IOLOCK_SHARED)) {
> +		return __xfs_rwsem_islocked(&VFS_I(ip)->i_rwsem, lock_flags,
> +				XFS_IOLOCK_FLAG_SHIFT);
>  	}
>  
>  	ASSERT(0);
> -	return 0;
> +	return false;
>  }
>  #endif
>  
> diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h
> index e9a8bb184d1f..9cecd6c9c90c 100644
> --- a/fs/xfs/xfs_inode.h
> +++ b/fs/xfs/xfs_inode.h
> @@ -268,12 +268,19 @@ static inline void xfs_ifunlock(struct xfs_inode *ip)
>   * Bit ranges:	1<<1  - 1<<16-1 -- iolock/ilock modes (bitfield)
>   *		1<<16 - 1<<32-1 -- lockdep annotation (integers)
>   */
> -#define	XFS_IOLOCK_EXCL		(1<<0)
> -#define	XFS_IOLOCK_SHARED	(1<<1)
> -#define	XFS_ILOCK_EXCL		(1<<2)
> -#define	XFS_ILOCK_SHARED	(1<<3)
> -#define	XFS_MMAPLOCK_EXCL	(1<<4)
> -#define	XFS_MMAPLOCK_SHARED	(1<<5)
> +
> +#define XFS_IOLOCK_FLAG_SHIFT	0
> +#define XFS_ILOCK_FLAG_SHIFT	2
> +#define XFS_MMAPLOCK_FLAG_SHIFT	4
> +
> +#define XFS_SHARED_LOCK_SHIFT	1
> +
> +#define XFS_IOLOCK_EXCL		(1 << XFS_IOLOCK_FLAG_SHIFT)
> +#define XFS_IOLOCK_SHARED	(XFS_IOLOCK_EXCL << XFS_SHARED_LOCK_SHIFT)
> +#define XFS_ILOCK_EXCL		(1 << XFS_ILOCK_FLAG_SHIFT)
> +#define XFS_ILOCK_SHARED	(XFS_ILOCK_EXCL << XFS_SHARED_LOCK_SHIFT)
> +#define XFS_MMAPLOCK_EXCL	(1 << XFS_MMAPLOCK_FLAG_SHIFT)
> +#define XFS_MMAPLOCK_SHARED	(XFS_MMAPLOCK_EXCL << XFS_SHARED_LOCK_SHIFT)
>  
>  #define XFS_LOCK_MASK		(XFS_IOLOCK_EXCL | XFS_IOLOCK_SHARED \
>  				| XFS_ILOCK_EXCL | XFS_ILOCK_SHARED \
> @@ -412,7 +419,7 @@ void		xfs_ilock(xfs_inode_t *, uint);
>  int		xfs_ilock_nowait(xfs_inode_t *, uint);
>  void		xfs_iunlock(xfs_inode_t *, uint);
>  void		xfs_ilock_demote(xfs_inode_t *, uint);
> -int		xfs_isilocked(xfs_inode_t *, uint);
> +bool		xfs_isilocked(struct xfs_inode *, uint);
>  uint		xfs_ilock_data_map_shared(struct xfs_inode *);
>  uint		xfs_ilock_attr_map_shared(struct xfs_inode *);
>  
> -- 
> 2.26.2
>