On Mon, Aug 03, 2026 at 01:59:07PM +0200, Jiri Pirko wrote: > Fri, Jul 31, 2026 at 02:54:31PM +0200, [email protected] wrote: > >> From: Jiri Pirko <[email protected]> > >> > >> Commit eb70d83a8645 ("RDMA/mana_ib: Adopt robust udata") renamed the > >> "flags" field of struct mana_ib_create_cq to "comp_mask", as > >> ib_copy_validate_udata_in_cm() only validates a member with that name. > >> > >> The layout did not change, but the field has been a part of the UAPI since > >> commit 44b607ad4cdf ("RDMA/mana_ib: implement uapi for creation of rnic > >> cq"), so the rename breaks userspace referring to it, for example the mana > >> provider of rdma-core assigning cmd_drv->flags. > >> > >> Convert the field to a union providing both names, so that > >> ib_copy_validate_udata_in_cm() still finds "comp_mask" and userspace keeps > >> "flags", without having to add a helper for this single case. > >> > > > >Thanks for the patch, but my understanding that it is a common practice to > >rename the fields, > >and kernels headers should not accumulate historical names. > > That is not doable in UAPI.
There are multiple levels of UAPI contracts. In RDMA, we guarantee binary compatibility because userspace (rdma-core) is effectively the second half of the RDMA driver stack. These drivers do not exist without rdma-core. As such, this is exactly how the RDMA UAPI is intended to work. > Some userspace app, like rdma-core in this case, might use it and rename > breaks the compilation. Some other > app you don't know about may use it. rdma-core does not use these headers directly. Instead, it vendors them in the kernel-headers directories specifically for this purpose. > > > >I also faced a similar problem from renames in other providers, when I > >needed a new kernel header in rdma-core. > >If this breaks your rdma-core in a PR, just remove the field rename in > >kernel update commit as that header update commit is not getting merged > >anyway from your PR. > >My understanding that maintainers of RDMA-core will merge the kernel header > >update, and will bring this change from my PR: > >https://github.com/linux-rdma/rdma-core/pull/1765/commits/0dcadd9316f1b98e21973e3a6e0f96186d49bd5a > > this is not how UAPI can be changed :/ It simply can't be changed. It can, at least in RDMA and elsewhere in the kernel, where user access is provided through properly designed libraries. Thanks > > > > > >- Konstantin > > > >> Fixes: eb70d83a8645 ("RDMA/mana_ib: Adopt robust udata") > >> Signed-off-by: Jiri Pirko <[email protected]> > >> --- > >> include/uapi/rdma/mana-abi.h | 5 ++++- > >> 1 file changed, 4 insertions(+), 1 deletion(-) > >> > >> diff --git a/include/uapi/rdma/mana-abi.h b/include/uapi/rdma/mana-abi.h > >> index 410f0ddc8c89..431c7076f20a 100644 > >> --- a/include/uapi/rdma/mana-abi.h > >> +++ b/include/uapi/rdma/mana-abi.h > >> @@ -25,7 +25,10 @@ enum mana_ib_create_cq_flags { > >> > >> struct mana_ib_create_cq { > >> __aligned_u64 buf_addr; > >> - __u16 comp_mask; > >> + union { > >> + __u16 comp_mask; > >> + __u16 flags; /* the original name of the field */ > >> + }; > >> __u16 reserved0; > >> __u32 reserved1; > >> }; > >> -- > >> 2.54.0 > >
