[PATCH][next] RDMA/cm: Avoid -Wflex-array-member-not-at-end warning

[PATCH][next] RDMA/cm: Avoid -Wflex-array-member-not-at-end warning

[Gustavo A. R. Silva]

-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@kernel.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[];
 };
 
 struct cm_timewait_info {
-	struct cm_work work;
+	struct cm_work_hdr work;
 	struct list_head list;
 	struct rb_node remote_qp_node;
 	struct rb_node remote_id_node;
@@ -3440,7 +3443,7 @@ static int cm_timewait_handler(struct cm_work *work)
 	struct cm_timewait_info *timewait_info;
 	struct cm_id_private *cm_id_priv;
 
-	timewait_info = container_of(work, struct cm_timewait_info, work);
+	timewait_info = container_of(&work->hdr, struct cm_timewait_info, work);
 	spin_lock_irq(&cm.lock);
 	list_del(&timewait_info->list);
 	spin_unlock_irq(&cm.lock);
-- 
2.34.1

Re: [PATCH][next] RDMA/cm: Avoid -Wflex-array-member-not-at-end warning

[Jason Gunthorpe]

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@kernel.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.

Jason

Re: [PATCH][next] RDMA/cm: Avoid -Wflex-array-member-not-at-end warning

[Gustavo A. R. Silva]

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@kernel.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

Re: [PATCH][next] RDMA/cm: Avoid -Wflex-array-member-not-at-end warning

[Leon Romanovsky]

On Mon, Mar 25, 2024 at 08:57:08PM -0600, Gustavo A. R. Silva wrote:
> 
> 
> 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@kernel.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 let's try to invest in this direction first before we add obfuscation
with magic words to the code.

Thanks

> So, the `struct_group_tagged()` strategy is in general more cleaner and straightforward.
> 
> --
> Gustavo
> 
>