linux-kernel - Re: [PATCH] IB/SA: replace usage of found with dedicated list iterator variable

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Message-Id: <FA1E832C-2030-4344-97EA-E0E219DDDF6C@gmail.com>
Date:   Thu, 24 Mar 2022 09:24:01 +0100
From:   Jakob Koschel <jakobkoschel@...il.com>
To:     Mark Zhang <markzhang@...dia.com>
Cc:     Jason Gunthorpe <jgg@...pe.ca>, Leon Romanovsky <leon@...nel.org>,
        Håkon Bugge <haakon.bugge@...cle.com>,
        Mark Bloch <mbloch@...dia.com>,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        linux-rdma <linux-rdma@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Mike Rapoport <rppt@...nel.org>,
        Brian Johannesmeyer <bjohannesmeyer@...il.com>,
        Cristiano Giuffrida <c.giuffrida@...nl>,
        "Bos, H.J." <h.j.bos@...nl>
Subject: Re: [PATCH] IB/SA: replace usage of found with dedicated list
 iterator variable



> On 24. Mar 2022, at 08:53, Mark Zhang <markzhang@...dia.com> wrote:
> 
> On 3/24/2022 3:11 PM, Jakob Koschel wrote:
>> External email: Use caution opening links or attachments
>> To move the list iterator variable into the list_for_each_entry_*()
>> macro in the future it should be avoided to use the list iterator
>> variable after the loop body.
>> To *never* use the list iterator variable after the loop it was
>> concluded to use a separate iterator variable instead of a
>> found boolean [1].
>> This removes the need to use a found variable and simply checking if
>> the variable was set, can determine if the break/goto was hit.
>> Link: https://lore.kernel.org/all/CAHk-=wgRr_D8CB-D9Kg-c=EHreAsk5SqXPwr9Y7k9sA6cWXJ6w@mail.gmail.com/
>> Signed-off-by: Jakob Koschel <jakobkoschel@...il.com>
>> ---
>> drivers/infiniband/core/sa_query.c | 15 +++++++--------
>> 1 file changed, 7 insertions(+), 8 deletions(-)
>> diff --git a/drivers/infiniband/core/sa_query.c b/drivers/infiniband/core/sa_query.c
>> index 74ecd7456a11..74cd84045e5b 100644
>> --- a/drivers/infiniband/core/sa_query.c
>> +++ b/drivers/infiniband/core/sa_query.c
>> @@ -1035,10 +1035,9 @@ int ib_nl_handle_resolve_resp(struct sk_buff *skb,
>> struct netlink_ext_ack *extack)
>> {
>> unsigned long flags;
>> - struct ib_sa_query *query;
>> + struct ib_sa_query *query = NULL, *iter;
>> struct ib_mad_send_buf *send_buf;
>> struct ib_mad_send_wc mad_send_wc;
>> - int found = 0;
>> int ret;
>> if ((nlh->nlmsg_flags & NLM_F_REQUEST) ||
>> @@ -1046,20 +1045,20 @@ int ib_nl_handle_resolve_resp(struct sk_buff *skb,
>> return -EPERM;
>> spin_lock_irqsave(&ib_nl_request_lock, flags);
>> - list_for_each_entry(query, &ib_nl_request_list, list) {
>> + list_for_each_entry(iter, &ib_nl_request_list, list) {
>> /*
>> * If the query is cancelled, let the timeout routine
>> * take care of it.
>> */
>> - if (nlh->nlmsg_seq == query->seq) {
>> - found = !ib_sa_query_cancelled(query);
>> - if (found)
>> - list_del(&query->list);
>> + if (nlh->nlmsg_seq == iter->seq) {
>> + if (!ib_sa_query_cancelled(iter))
>> + list_del(&iter->list);
>> + query = iter;
>> break;
> 
> Should it be:
> 
> if (nlh->nlmsg_seq == iter->seq) {
> 	if (!ib_sa_query_cancelled(iter)) {
> 		list_del(&iter->list);
> 		query = iter;
> 	}
> 	break;

yes you are right. Sorry about that, I'll send a fixed version with v2.

> 
>> }
>> }
>> - if (!found) {
>> + if (!query) {
>> spin_unlock_irqrestore(&ib_nl_request_lock, flags);
>> goto resp_out;
>> }
>> base-commit: f443e374ae131c168a065ea1748feac6b2e76613
>> --
>> 2.25.1