Re: [PATCH rdma-next] RDMA/uverbs: Propagate errors from rdma_lookup_get_uobject()

[Jason Gunthorpe <jgg@nvidia.com>]

On Wed, Feb 19, 2025 at 05:56:47PM +0200, Leon Romanovsky wrote:
> On Wed, Feb 19, 2025 at 10:46:16AM -0400, Jason Gunthorpe wrote:
> > On Wed, Feb 19, 2025 at 03:52:05PM +0200, Leon Romanovsky wrote:
> > > From: Maher Sanalla <msanalla@nvidia.com>
> > > 
> > > Currently, the IB uverbs API calls uobj_get_uobj_read(), which in turn
> > > uses the rdma_lookup_get_uobject() helper to retrieve user objects.
> > > In case of failure, uobj_get_uobj_read() returns NULL, overriding the
> > > error code from rdma_lookup_get_uobject(). The IB uverbs API then
> > > translates this NULL to -EINVAL, masking the actual error and
> > > complicating debugging.
> > 
> > This may have been deliberate as this old stuff is not supposed to be
> > returning weird error codes.
> 
> I assumed that this was the reason for such overwrite in the past, but
> is this continue to be true in 2025?

Maybe, it is ABI that leaks out libiverbs

But also, maybe nobody cares. There is a small chance places are
relying on detecting certain errnos.

> > What error code are you missing here?
> 
> Error returned from modify QP was masked by setting real error to be -EINVAL.

What errno was it though? What other errors are there that are now no
longer supressed?

I think the commit message needs a deeper analysis to be convincing
the ABI break is low risk

Jason