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Message-ID: <5c0bb827-e5f3-4178-ad46-8ac9b99d7726@embeddedor.com>
Date: Mon, 25 Mar 2024 20:57:08 -0600
From: "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To: Jason Gunthorpe <jgg@...pe.ca>,
"Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc: Leon Romanovsky <leon@...nel.org>, linux-rdma@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH][next] RDMA/cm: Avoid -Wflex-array-member-not-at-end
warning
On 3/25/24 16:47, Jason Gunthorpe wrote:
> On Mon, Mar 25, 2024 at 02:24:07PM -0600, Gustavo A. R. Silva wrote:
>> -Wflex-array-member-not-at-end is coming in GCC-14, and we are getting
>> ready to enable it globally.
>>
>> Use the `struct_group_tagged()` helper to separate the flexible array
>> from the rest of the members in flexible `struct cm_work`, and avoid
>> embedding the flexible-array member in `struct cm_timewait_info`.
>>
>> Also, use `container_of()` to retrieve a pointer to the flexible
>> structure.
>>
>> So, with these changes, fix the following warning:
>> drivers/infiniband/core/cm.c:196:24: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
>>
>> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
>> ---
>> drivers/infiniband/core/cm.c | 21 ++++++++++++---------
>> 1 file changed, 12 insertions(+), 9 deletions(-)
>>
>> diff --git a/drivers/infiniband/core/cm.c b/drivers/infiniband/core/cm.c
>> index bf0df6ee4f78..80c87085499c 100644
>> --- a/drivers/infiniband/core/cm.c
>> +++ b/drivers/infiniband/core/cm.c
>> @@ -182,18 +182,21 @@ struct cm_av {
>> };
>>
>> struct cm_work {
>> - struct delayed_work work;
>> - struct list_head list;
>> - struct cm_port *port;
>> - struct ib_mad_recv_wc *mad_recv_wc; /* Received MADs */
>> - __be32 local_id; /* Established / timewait */
>> - __be32 remote_id;
>> - struct ib_cm_event cm_event;
>> + /* New members must be added within the struct_group() macro below. */
>> + struct_group_tagged(cm_work_hdr, hdr,
>> + struct delayed_work work;
>> + struct list_head list;
>> + struct cm_port *port;
>> + struct ib_mad_recv_wc *mad_recv_wc; /* Received MADs */
>> + __be32 local_id; /* Established / timewait */
>> + __be32 remote_id;
>> + struct ib_cm_event cm_event;
>> + );
>> struct sa_path_rec path[];
>> };
>
> I didn't look, but does it make more sense to break out the path side
> into its own type and avoid the struct_group_tagged? I seem to
> remember only one thing used it.
>
I thought about that, but I'd have to change the parameter type of
`static int cm_timewait_handler(struct cm_work *work)`, and that would
imply also modifying the internals of function `cm_work_handler()` (and
then I didn't look much into it). So, the `struct_group_tagged()`
strategy is in general more cleaner and straightforward.
--
Gustavo
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