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

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. 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.


>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.


>
>- 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
>