netdev - Re: [PATCH V2 5/9] IB/mlx5: Mellanox Connect-IB, IB driver part 1/5

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Date:	Thu, 4 Jul 2013 16:15:25 +0300
From:	Jack Morgenstein <jackm@....mellanox.co.il>
To:	Joe Perches <joe@...ches.com>
Cc:	Or Gerlitz <ogerlitz@...lanox.com>, roland@...nel.org,
	linux-rdma@...r.kernel.org, netdev@...r.kernel.org,
	davem@...emloft.net, eli@....mellanox.co.il, moshel@...lanox.com,
	Eli Cohen <eli@...lanox.com>
Subject: Re: [PATCH V2 5/9] IB/mlx5: Mellanox Connect-IB, IB driver part 1/5

On Wednesday 03 July 2013 23:59, Joe Perches wrote:
> On Wed, 2013-07-03 at 20:13 +0300, Or Gerlitz wrote:
> > From: Eli Cohen <eli@...lanox.com>
> > diff --git a/drivers/infiniband/hw/mlx5/ah.c b/drivers/infiniband/hw/mlx5/ah.c
> []
> > +struct ib_ah *create_ib_ah(struct ib_ah_attr *ah_attr,
> > +			   struct mlx5_ib_ah *ah)
> > +{
> > +	u32 sgi;
> 
> sgi is used once here and looks more confusing than helpful
> 
Will fix in V3
> 
> []
> 
> > +static void *get_sw_cqe(struct mlx5_ib_cq *cq, int n)
> > +{
> > +	void *cqe = get_cqe(cq, n & cq->ibcq.cqe);
> > +	struct mlx5_cqe64 *cqe64;
> > +
> > +	cqe64 = (cq->mcq.cqe_sz == 64) ? cqe : cqe + 64;
> > +	return ((cqe64->op_own & MLX5_CQE_OWNER_MASK) ^
> > +		!!(n & (cq->ibcq.cqe + 1))) ? NULL : cqe;
> 
> I think "foo ^ !!bar" is excessively tricky.
> 
The mlx4 driver already uses "!!foo ^ !!bar" in several places in the kernel (and this is old code).
I assume that your problem with the above code is that it uses "foo" and not "!!foo".

Please note, though, that this code is data-path code -- and in this specific case,  foo = !!foo
(since MLX5_CQE_OWNER_MASK = 1). We decided, therefore, in this specific case, not to add the unnecessary
"!!", even though at first glance it may look tricky -- performance here IMHO is more important.

> > +static enum ib_wc_opcode get_umr_comp(struct mlx5_ib_wq *wq, int idx)
> > +{
> 
> > +		pr_warn("unkonwn completion status\n");
> 
> unknown tyop

Will fix in V3

> []
> 
> > +static int create_cq_user(struct mlx5_ib_dev *dev, struct ib_udata *udata,
> > +			  struct ib_ucontext *context, struct mlx5_ib_cq *cq,
> > +			  int entries, struct mlx5_create_cq_mbox_in **cqb,
> > +			  int *cqe_size, int *index, int *inlen)
> []
> > +	*inlen = sizeof **cqb + sizeof *(*cqb)->pas * ncont;
> 
> sizeof always uses parentheses
> 
> > +	*cqb = vzalloc(*inlen);
> 
> Perhaps you may be using vzalloc too often.
> 
> Maybe you should have a helper allocating either
> from kmalloc or vmalloc as necessary based on size.
We will look into this.

Thanks for reviewing!

-Jack

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