linux-kernel - RE: [PATCH v5 3/8] x86/resctrl: Split the rdt

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Message-ID: <SJ1PR11MB6083210E470189053CCD1F70FCC2A@SJ1PR11MB6083.namprd11.prod.outlook.com>
Date:   Wed, 27 Sep 2023 00:00:00 +0000
From:   "Luck, Tony" <tony.luck@...el.com>
To:     "Chatre, Reinette" <reinette.chatre@...el.com>
CC:     "Yu, Fenghua" <fenghua.yu@...el.com>,
        Peter Newman <peternewman@...gle.com>,
        Jonathan Corbet <corbet@....net>,
        Shuah Khan <skhan@...uxfoundation.org>,
        "x86@...nel.org" <x86@...nel.org>,
        Shaopeng Tan <tan.shaopeng@...itsu.com>,
        James Morse <james.morse@....com>,
        Jamie Iles <quic_jiles@...cinc.com>,
        Babu Moger <babu.moger@....com>,
        Randy Dunlap <rdunlap@...radead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "patches@...ts.linux.dev" <patches@...ts.linux.dev>
Subject: RE: [PATCH v5 3/8] x86/resctrl: Split the rdt_domain structure

> I expect you are right and your proposal makes the code cleaner.
> Could the list_entry() call within rdt_find_domain() instead
> extract a pointer to a struct rdt_domain_hdr? To me that would make
> it most generic and avoid using wrong type for a pointer. I do think that
> may have been what you intended by moving id in there though ...

Reinette,

Exactly my thoughts! The function currently looks like this
(though I expect my mail client may mess up the formatting):

struct rdt_domain_hdr *rdt_find_domain(struct list_head *h, int id,
                                       struct list_head **pos)
{
        struct rdt_domain_hdr *d;
        struct list_head *l;

        if (id < 0)
                return ERR_PTR(-ENODEV);

        list_for_each(l, h) {
                d = list_entry(l, struct rdt_domain_hdr, list);
                /* When id is found, return its domain. */
                if (id == d->id)
                        return d;
                /* Stop searching when finding id's position in sorted list. */
                if (id < d->id)
                        break;
        }

        if (pos)
                *pos = l;

        return NULL;
}

and a typical caller does this:

        struct rdt_domain_hdr *hdr;
        struct rdt_mon_domain *d;




        hdr = rdt_find_domain(&r->mon_domains, id, &add_pos);
        if (IS_ERR(hdr)) {
                pr_warn("Couldn't find monitor scope id=%d for CPU %d\n", id, cpu);
                return;
        }
        d = container_of(hdr, struct rdt_mon_domain, hdr);

-Tony