Re: [PATCH] RDMA/mana_ib: Add flex array to struct mana_cfg_rx_steer_req_v2

[Erick Archer]

Hi Gustavo,

On Sun, Mar 31, 2024 at 08:53:07PM -0600, Gustavo A. R. Silva wrote:
> 
> 
> On 31/03/24 09:04, Erick Archer wrote:
> > The "struct mana_cfg_rx_steer_req_v2" uses a dynamically sized set of
> > trailing elements. Specifically, it uses a "mana_handle_t" array. So,
> > use the preferred way in the kernel declaring a flexible array [1].
> > 
> > Also, avoid the open-coded arithmetic in the memory allocator functions
> > [2] using the "struct_size" macro.
> > 
> > Moreover, use the "offsetof" helper to get the indirect table offset
> > instead of the "sizeof" operator and avoid the open-coded arithmetic in
> > pointers using the new flex member.
> > 
> > Now, it is also possible to use the "flex_array_size" helper to compute
> > the size of these trailing elements in the "memcpy" function.
> > 
> > Link: https://www.kernel.org/doc/html/next/process/deprecated.html#zero-length-and-one-element-arrays [1]
> > Link: https://www.kernel.org/doc/html/next/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments [2]
> > Signed-off-by: Erick Archer <erick.archer@xxxxxxxxxxx>
> > ---
> >   drivers/infiniband/hw/mana/qp.c               | 8 ++++----
> >   drivers/net/ethernet/microsoft/mana/mana_en.c | 9 +++++----
> >   include/net/mana/mana.h                       | 1 +
> >   3 files changed, 10 insertions(+), 8 deletions(-)
> > 
> > diff --git a/drivers/infiniband/hw/mana/qp.c b/drivers/infiniband/hw/mana/qp.c
> > index 6e7627745c95..c2a39db8ef92 100644
> > --- a/drivers/infiniband/hw/mana/qp.c
> > +++ b/drivers/infiniband/hw/mana/qp.c
> > @@ -22,8 +22,7 @@ static int mana_ib_cfg_vport_steering(struct mana_ib_dev *dev,
> >   	gc = mdev_to_gc(dev);
> > -	req_buf_size =
> > -		sizeof(*req) + sizeof(mana_handle_t) * MANA_INDIRECT_TABLE_SIZE;
> > +	req_buf_size = struct_size(req, indir_tab, MANA_INDIRECT_TABLE_SIZE);
> >   	req = kzalloc(req_buf_size, GFP_KERNEL);
> >   	if (!req)
> >   		return -ENOMEM;
> > @@ -44,11 +43,12 @@ static int mana_ib_cfg_vport_steering(struct mana_ib_dev *dev,
> >   		req->rss_enable = true;
> >   	req->num_indir_entries = MANA_INDIRECT_TABLE_SIZE;
> > -	req->indir_tab_offset = sizeof(*req);
> > +	req->indir_tab_offset = offsetof(struct mana_cfg_rx_steer_req_v2,
> > +					 indir_tab);
> >   	req->update_indir_tab = true;
> >   	req->cqe_coalescing_enable = 1;
> > -	req_indir_tab = (mana_handle_t *)(req + 1);
> > +	req_indir_tab = req->indir_tab;
> 
> It seems that `req_indir_tab` can be removed, and `req->indir_tab` be directly used.

It seems reasonable to me. Thanks for looking at this.

Regards,
Erick

> 
> >   	/* The ind table passed to the hardware must have
> >   	 * MANA_INDIRECT_TABLE_SIZE entries. Adjust the verb
> >   	 * ind_table to MANA_INDIRECT_TABLE_SIZE if required
> > diff --git a/drivers/net/ethernet/microsoft/mana/mana_en.c b/drivers/net/ethernet/microsoft/mana/mana_en.c
> > index 59287c6e6cee..04aa096c6cc4 100644
> > --- a/drivers/net/ethernet/microsoft/mana/mana_en.c
> > +++ b/drivers/net/ethernet/microsoft/mana/mana_en.c
> > @@ -1062,7 +1062,7 @@ static int mana_cfg_vport_steering(struct mana_port_context *apc,
> >   	u32 req_buf_size;
> >   	int err;
> > -	req_buf_size = sizeof(*req) + sizeof(mana_handle_t) * num_entries;
> > +	req_buf_size = struct_size(req, indir_tab, num_entries);
> >   	req = kzalloc(req_buf_size, GFP_KERNEL);
> >   	if (!req)
> >   		return -ENOMEM;
> > @@ -1074,7 +1074,8 @@ static int mana_cfg_vport_steering(struct mana_port_context *apc,
> >   	req->vport = apc->port_handle;
> >   	req->num_indir_entries = num_entries;
> > -	req->indir_tab_offset = sizeof(*req);
> > +	req->indir_tab_offset = offsetof(struct mana_cfg_rx_steer_req_v2,
> > +					 indir_tab);
> >   	req->rx_enable = rx;
> >   	req->rss_enable = apc->rss_state;
> >   	req->update_default_rxobj = update_default_rxobj;
> > @@ -1087,9 +1088,9 @@ static int mana_cfg_vport_steering(struct mana_port_context *apc,
> >   		memcpy(&req->hashkey, apc->hashkey, MANA_HASH_KEY_SIZE);
> >   	if (update_tab) {
> > -		req_indir_tab = (mana_handle_t *)(req + 1);
> > +		req_indir_tab = req->indir_tab;
> 
> Ditto.
> 
> Thanks
> --
> Gustavo
> 
> >   		memcpy(req_indir_tab, apc->rxobj_table,
> > -		       req->num_indir_entries * sizeof(mana_handle_t));
> > +		       flex_array_size(req, indir_tab, req->num_indir_entries));
> >   	}
> >   	err = mana_send_request(apc->ac, req, req_buf_size, &resp,
> > diff --git a/include/net/mana/mana.h b/include/net/mana/mana.h
> > index 76147feb0d10..20ffcae29e1e 100644
> > --- a/include/net/mana/mana.h
> > +++ b/include/net/mana/mana.h
> > @@ -671,6 +671,7 @@ struct mana_cfg_rx_steer_req_v2 {
> >   	u8 hashkey[MANA_HASH_KEY_SIZE];
> >   	u8 cqe_coalescing_enable;
> >   	u8 reserved2[7];
> > +	mana_handle_t indir_tab[];
> >   }; /* HW DATA */
> >   struct mana_cfg_rx_steer_resp {