Re: [PATCH rdma-next] RDMA/mana_ib: Retain create CQ flags field name

[Jiri Pirko <jiri@resnulli.us>]

Mon, Aug 03, 2026 at 03:28:44PM +0200, leon@kernel.org wrote:
>On Mon, Aug 03, 2026 at 01:59:07PM +0200, Jiri Pirko wrote:
>> Fri, Jul 31, 2026 at 02:54:31PM +0200, kotaranov@microsoft.com wrote:
>> >> From: Jiri Pirko <jiri@nvidia.com>
>> >> 
>> >> 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.

That is some odd UAPI...


>
>
>> 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.

Ehm, up to you. Very loose.


>
>Thanks
>
>> 
>> 
>> >
>> >- Konstantin
>> >
>> >> Fixes: eb70d83a8645 ("RDMA/mana_ib: Adopt robust udata")
>> >> Signed-off-by: Jiri Pirko <jiri@nvidia.com>
>> >> ---
>> >>  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
>> >