linux-kernel - Re: [PATCH 6/6] treewide: remove check of list iterator against head past the loop body

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Message-ID: <20220228131255.GC2812@kadam>
Date:   Mon, 28 Feb 2022 16:12:55 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Jakob Koschel <jakobkoschel@...il.com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Arnd Bergman <arnd@...db.de>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Kees Cook <keescook@...omium.org>,
        Mike Rapoport <rppt@...nel.org>,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        Brian Johannesmeyer <bjohannesmeyer@...il.com>,
        Cristiano Giuffrida <c.giuffrida@...nl>,
        "Bos, H.J." <h.j.bos@...nl>,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Nathan Chancellor <nathan@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-sgx@...r.kernel.org,
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Subject: Re: [PATCH 6/6] treewide: remove check of list iterator against head
 past the loop body

On Mon, Feb 28, 2022 at 12:08:22PM +0100, Jakob Koschel wrote:
> diff --git a/drivers/infiniband/hw/hfi1/tid_rdma.c b/drivers/infiniband/hw/hfi1/tid_rdma.c
> index 2a7abf7a1f7f..a069847b56aa 100644
> --- a/drivers/infiniband/hw/hfi1/tid_rdma.c
> +++ b/drivers/infiniband/hw/hfi1/tid_rdma.c
> @@ -1239,7 +1239,7 @@ static int kern_alloc_tids(struct tid_rdma_flow *flow)
>  	struct hfi1_ctxtdata *rcd = flow->req->rcd;
>  	struct hfi1_devdata *dd = rcd->dd;
>  	u32 ngroups, pageidx = 0;
> -	struct tid_group *group = NULL, *used;
> +	struct tid_group *group = NULL, *used, *tmp;
>  	u8 use;
> 
>  	flow->tnode_cnt = 0;
> @@ -1248,13 +1248,15 @@ static int kern_alloc_tids(struct tid_rdma_flow *flow)
>  		goto used_list;
> 
>  	/* First look at complete groups */
> -	list_for_each_entry(group,  &rcd->tid_group_list.list, list) {
> -		kern_add_tid_node(flow, rcd, "complete groups", group,
> -				  group->size);
> +	list_for_each_entry(tmp,  &rcd->tid_group_list.list, list) {
> +		kern_add_tid_node(flow, rcd, "complete groups", tmp,
> +				  tmp->size);
> 
> -		pageidx += group->size;
> -		if (!--ngroups)
> +		pageidx += tmp->size;
> +		if (!--ngroups) {
> +			group = tmp;
>  			break;
> +		}
>  	}
> 
>  	if (pageidx >= flow->npagesets)
> @@ -1277,7 +1279,7 @@ static int kern_alloc_tids(struct tid_rdma_flow *flow)
>  	 * However, if we are at the head, we have reached the end of the
                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>  	 * complete groups list from the first loop above
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>  	 */

Originally this code tested for an open code list_is_head() so the
comment made sense, but it's out of date now.  Just delete it.


> -	if (group && &group->list == &rcd->tid_group_list.list)
> +	if (!group)
>  		goto bail_eagain;
>  	group = list_prepare_entry(group, &rcd->tid_group_list.list,
>  				   list);

regards,
dan carpenter