Re: [PATCH 05/18] xfs: separate out initial attr_set states

["Darrick J. Wong" <djwong@kernel.org>]

On Wed, May 11, 2022 at 11:06:51AM +1000, Dave Chinner wrote:
> On Tue, May 10, 2022 at 04:12:34PM -0700, Darrick J. Wong wrote:
> > On Mon, May 09, 2022 at 10:41:25AM +1000, Dave Chinner wrote:
> > > diff --git a/fs/xfs/libxfs/xfs_attr.h b/fs/xfs/libxfs/xfs_attr.h
> > > index c9c867e3406c..ad52b5dc59e4 100644
> > > --- a/fs/xfs/libxfs/xfs_attr.h
> > > +++ b/fs/xfs/libxfs/xfs_attr.h
> > > @@ -530,4 +553,35 @@ void xfs_attri_destroy_cache(void);
> > >  int __init xfs_attrd_init_cache(void);
> > >  void xfs_attrd_destroy_cache(void);
> > >  
> > > +/*
> > > + * Check to see if the attr should be upgraded from non-existent or shortform to
> > > + * single-leaf-block attribute list.
> > > + */
> > > +static inline bool
> > > +xfs_attr_is_shortform(
> > > +	struct xfs_inode    *ip)
> > > +{
> > > +	return ip->i_afp->if_format == XFS_DINODE_FMT_LOCAL ||
> > > +	       (ip->i_afp->if_format == XFS_DINODE_FMT_EXTENTS &&
> > > +		ip->i_afp->if_nextents == 0);
> > > +}
> > > +
> > > +static inline enum xfs_delattr_state
> > > +xfs_attr_init_add_state(struct xfs_da_args *args)
> > > +{
> > > +	if (!args->dp->i_afp)
> > > +		return XFS_DAS_DONE;
> > 
> > If we're in add/replace attr call without an attr fork, why do we go
> > straight to finished?
> 
> I suspect I've fixed all the issues that triggered crashes here
> because args->dp->i_afp was null. THere were transient states in a
> replace operaiton when the remove takes away the last attr, removes
> the attr fork, then calls the ADD operation. The add operation
> assumes that the attr fork has already been set up, and so bad
> things happened here.
> 
> This also occurred when setting up recovery operations - recovery of
> an add/replace could start from that same "there's no attr fork"
> condition, and so calling xfs_inode_has_attr() or
> xfs_attr_is_shortform() direct from the reocovery setup code would
> go splat because ip->i_afp was null.
> 
> I'm going to leave this for the moment (cleanup note made) because I
> don't want to have to find out that I missed a corner case somewhere
> they hard way right now. It's basically there to stop log recovery
> crashing hard, which only occurs when the experimental larp code is
> running, so I think this is safe to leave for a later cleanup.

Hmm, in that case, can this become:

	if (!args->dp->i_afp) {
		ASSERT(0);
		return XFS_DAS_DONE;
	}

And then you can add:
Reviewed-by: Darrick J. Wong <djwong@kernel.org>

--D


> Cheers,
> 
> Dave.
> -- 
> Dave Chinner
> david@fromorbit.com