Re: [PATCH v8 21/21] nbd: assert that Error** is not NULL in nbd_iter_channel_error

[Markus Armbruster <armbru@redhat.com>]

Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> writes:

> 06.12.2019 18:58, Markus Armbruster wrote:
>> Eric Blake <eblake@redhat.com> writes:
>> 
>>> On 12/5/19 11:46 AM, Vladimir Sementsov-Ogievskiy wrote:
>>>> The local_err parameter is not here to return information about
>>>> nbd_iter_channel_error failure. Instead it's assumed to be filled when
>>>> passed to the function. This is already stressed by its name
>>>> (local_err, instead of classic errp). Stress it additionally by
>>>> assertion.
>>>>
>>>> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
>>>> ---
>>>>    block/nbd.c | 1 +
>>>>    1 file changed, 1 insertion(+)
>>>
>>> Our timing resulted in crossed mails - I was replying to v7 when this
>>> landed, and my reply there is still relevant (namely, a better commit
>>> message is needed, but the code gets my R-b with that change).
>> 
>> If v8 turns out to be fine except for commit message tweaks, I'll gladly
>> to these in my tree.  Just tell me what to do in a reply to this
>> message.
>> 
>
> Yes, this would be great, thanks!
>
> The only thing is your suggestion on patch 21, but it may be applied in separate (and it's actually a separate thing)

It's closer to idea than to suggestion, and it's separate.

Commit message in my tree:

    nbd: assert that Error** is not NULL in nbd_iter_channel_error
    
    All callers of nbd_iter_channel_error() pass the address of a
    local_err variable, and only call this function if an error has
    already occurred, using this function to propagate that error.
    This is already implied by its name (local_err instead of the classic
    errp), but it is worth additionally stressing this by adding an
    assertion to make it part of the function contract.
    
    The local_err parameter is not here to return information about
    nbd_iter_channel_error failure. Instead it's assumed to be filled when
    passed to the function. This is already stressed by its name
    (local_err, instead of classic errp). Stress it additionally by
    assertion.

Also:
Reviewed-by: Markus Armbruster <armbru@redhat.com>