Re: [PATCH v2 1/2] xfs: Fix compiler warning in xfs_attr_node_removename_setup

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

On Mon, Jul 27, 2020 at 09:51:54AM -0700, Allison Collins wrote:
> 
> 
> On 7/27/20 8:46 AM, Darrick J. Wong wrote:
> > On Sun, Jul 26, 2020 at 07:26:07PM -0700, Allison Collins wrote:
> > > Fix compiler warning for variable 'blk' set but not used in
> > > xfs_attr_node_removename_setup.  blk is used only in an ASSERT so only
> > > declare blk when DEBUG is set.
> > > 
> > > Reported-by: kernel test robot <lkp@intel.com>
> > > Signed-off-by: Allison Collins <allison.henderson@oracle.com>
> > > ---
> > >   fs/xfs/libxfs/xfs_attr.c | 2 ++
> > >   1 file changed, 2 insertions(+)
> > > 
> > > diff --git a/fs/xfs/libxfs/xfs_attr.c b/fs/xfs/libxfs/xfs_attr.c
> > > index d4583a0..5168d32 100644
> > > --- a/fs/xfs/libxfs/xfs_attr.c
> > > +++ b/fs/xfs/libxfs/xfs_attr.c
> > > @@ -1174,7 +1174,9 @@ int xfs_attr_node_removename_setup(
> > >   	struct xfs_da_state	**state)
> > >   {
> > >   	int			error;
> > > +#ifdef DEBUG
> > >   	struct xfs_da_state_blk	*blk;
> > > +#endif
> > 
> > But now a non-DEBUG compilation will trip over the assignment to blk:
> > 
> > 	blk = &(*state)->path.blk[(*state)->path.active - 1];
> > 
> > that comes just before the asserts, right?
> > 
> > 	ASSERT((*state)->path.blk[(*state)->path.active - 1].bp != NULL);
> > 	ASSERT((*state)->path.blk[(*state)->path.active - 1].magic ==
> > 		XFS_ATTR_LEAF_MAGIC);
> > 
> > In the end you probably just want to encode the accessor logic in the
> > assert body so the whole thing just disappears entirely.
> Are you sure you'd rather have it that way, then once up in the declaration?
> Like this:
> 
> #ifdef DEBUG
> 	struct xfs_da_state_blk	*blk = &(*state)->path.blk[(*state)->path.active -
> 1];
> #endif

I thought xfs_attr_node_hasname could allocate the da state and set
*state, which means that we can't dereference *state until after that
call?

--D

> > 
> > --D
> > 
> > >   	error = xfs_attr_node_hasname(args, state);
> > >   	if (error != -EEXIST)
> > > -- 
> > > 2.7.4
> > >