Re: [PATCH rdma-next 2/3] RDMA/core: Let ib_find_gid() continue search even after empty entry

[Leon Romanovsky <leon@kernel.org>]

On Tue, Dec 07, 2021 at 02:43:04PM -0400, Jason Gunthorpe wrote:
> On Mon, Nov 22, 2021 at 01:53:57PM +0200, Leon Romanovsky wrote:
> > From: Avihai Horon <avihaih@nvidia.com>
> > 
> > Currently, ib_find_gid() will stop searching after encountering the
> > first empty GID table entry. This behavior is wrong since neither IB
> > nor RoCE spec enforce tightly packed GID tables.
> > 
> > For example, when a valid GID entry exists at index N, and if a GID
> > entry is empty at index N-1, ib_find_gid() will fail to find the valid
> > entry.
> > 
> > Fix it by making ib_find_gid() continue searching even after
> > encountering missing entries.
> > 
> > Fixes: 5eb620c81ce3 ("IB/core: Add helpers for uncached GID and P_Key searches")
> > Signed-off-by: Avihai Horon <avihaih@nvidia.com>
> > Reviewed-by: Mark Zhang <markzhang@nvidia.com>
> > Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
> >  drivers/infiniband/core/device.c | 3 +++
> >  1 file changed, 3 insertions(+)
> > 
> > diff --git a/drivers/infiniband/core/device.c b/drivers/infiniband/core/device.c
> > index 22a4adda7981..b5d8443030d4 100644
> > +++ b/drivers/infiniband/core/device.c
> > @@ -2460,8 +2460,11 @@ int ib_find_gid(struct ib_device *device, union ib_gid *gid,
> >  		for (i = 0; i < device->port_data[port].immutable.gid_tbl_len;
> >  		     ++i) {
> >  			ret = rdma_query_gid(device, port, i, &tmp_gid);
> > +			if (ret == -ENOENT)
> > +				continue;
> >  			if (ret)
> >  				return ret;
> 
> There is no return code from rdma_query_gid that means stop searching,

In rdma_query_gid() any error stopped searching, and here we continue
same behaviour as before. You can argue that this function can't really
get illegal parameters and it never returns -EINVAL, but someone needs
to check all callers that this is true.

> so just write
> 
> if (ret)
>    continue

As long as we don't delete input validity checks, it is not correct.

Thanks

> 
> Jason