Re: [PATCH v5 1/4] xfs: Refactor xfs_isilocked()

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Mon, Feb 17, 2020 at 05:35:21AM -0800, Christoph Hellwig wrote:
> On Fri, Feb 14, 2020 at 07:59:39PM +0100, 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>
> > ---
> >  fs/xfs/xfs_inode.c | 54 ++++++++++++++++++++++++++++++++--------------
> >  fs/xfs/xfs_inode.h |  2 +-
> >  2 files changed, 39 insertions(+), 17 deletions(-)
> > 
> > diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
> > index c5077e6326c7..3d28c4790231 100644
> > --- a/fs/xfs/xfs_inode.c
> > +++ b/fs/xfs/xfs_inode.c
> > @@ -345,32 +345,54 @@ xfs_ilock_demote(
> >  }
> >  
> >  #if defined(DEBUG) || defined(XFS_WARN)
> > -int
> > +static inline bool
> > +__xfs_rwsem_islocked(
> > +	struct rw_semaphore	*rwsem,
> > +	bool			shared,
> > +	bool			excl)
> > +{
> > +	bool locked = false;
> > +
> > +	if (!rwsem_is_locked(rwsem))
> > +		return false;
> > +
> > +	if (!debug_locks)
> > +		return true;
> > +
> > +	if (shared)
> > +		locked = lockdep_is_held_type(rwsem, 0);
> > +
> > +	if (excl)
> > +		locked |= lockdep_is_held_type(rwsem, 1);
> > +
> > +	return locked;
> 
> This could use some comments explaining the logic, especially why we
> need the shared and excl flags, which seems very confusing given that
> a lock can be held either shared or exclusive, but not neither and not
> both.

Yes, this predicate should document that callers are allowed to pass in
shared==true and excl==true when the caller wants to assert that either
lock type (shared or excl) of a given lock class (e.g. iolock) are held.

--D