linux-kernel - Re: [PATCH v3 1/3] resource: Use list

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Date:   Mon, 9 Apr 2018 19:34:09 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     Baoquan He <bhe@...hat.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Patrik Jakobsson <patrik.r.jakobsson@...il.com>,
        David Airlie <airlied@...ux.ie>,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Keith Busch <keith.busch@...el.com>,
        Jonathan Derrick <jonathan.derrick@...el.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Brijesh Singh <brijesh.singh@....com>,
        Jérôme Glisse <jglisse@...hat.com>,
        Borislav Petkov <bp@...e.de>,
        Tom Lendacky <thomas.lendacky@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Yaowei Bai <baiyaowei@...s.chinamobile.com>,
        Wei Yang <richard.weiyang@...il.com>,
        devel@...uxdriverproject.org, linux-input@...r.kernel.org,
        linux-nvdimm <linux-nvdimm@...ts.01.org>,
        Device Tree <devicetree@...r.kernel.org>,
        linux-pci@...r.kernel.org
Subject: Re: [PATCH v3 1/3] resource: Use list_head to link resource sibling

On Mon, Apr 9, 2018 at 7:10 PM, Baoquan He <bhe@...hat.com> wrote:
> On 04/09/18 at 08:38am, Dan Williams wrote:
>> On Mon, Apr 9, 2018 at 2:08 AM, Baoquan He <bhe@...hat.com> wrote:
>> > The struct resource uses singly linked list to link siblings. It's not
>> > easy to do reverse iteration on sibling list. So replace it with list_head.
>> >
>> > And code refactoring makes codes in kernel/resource.c more readable than
>> > pointer operation.
>> >
>> > Besides, type of member variables of struct resource, sibling and child, are
>> > changed from 'struct resource *' to 'struct list_head'. Kernel size will
>> > increase because of those statically defined struct resource instances.
>> >
>> > Signed-off-by: Baoquan He <bhe@...hat.com>
>> > ---
>> [..]
>> > diff --git a/kernel/resource.c b/kernel/resource.c
>> > index e270b5048988..473c624606f9 100644
>> > --- a/kernel/resource.c
>> > +++ b/kernel/resource.c
>> > @@ -31,6 +31,8 @@ struct resource ioport_resource = {
>> >         .start  = 0,
>> >         .end    = IO_SPACE_LIMIT,
>> >         .flags  = IORESOURCE_IO,
>> > +       .sibling = LIST_HEAD_INIT(ioport_resource.sibling),
>> > +       .child  = LIST_HEAD_INIT(ioport_resource.child),
>> >  };
>> >  EXPORT_SYMBOL(ioport_resource);
>> >
>> > @@ -39,6 +41,8 @@ struct resource iomem_resource = {
>> >         .start  = 0,
>> >         .end    = -1,
>> >         .flags  = IORESOURCE_MEM,
>> > +       .sibling = LIST_HEAD_INIT(iomem_resource.sibling),
>> > +       .child  = LIST_HEAD_INIT(iomem_resource.child),
>> >  };
>> >  EXPORT_SYMBOL(iomem_resource);
>> >
>> > @@ -57,20 +61,32 @@ static DEFINE_RWLOCK(resource_lock);
>> >   * by boot mem after the system is up. So for reusing the resource entry
>> >   * we need to remember the resource.
>> >   */
>> > -static struct resource *bootmem_resource_free;
>> > +static struct list_head bootmem_resource_free = LIST_HEAD_INIT(bootmem_resource_free);
>> >  static DEFINE_SPINLOCK(bootmem_resource_lock);
>> >
>> > +struct resource *sibling(struct resource *res)
>> > +{
>> > +       if (res->parent && !list_is_last(&res->sibling, &res->parent->child))
>> > +               return list_next_entry(res, sibling);
>> > +       return NULL;
>> > +}
>> > +
>> > +struct resource *first_child(struct list_head *head)
>> > +{
>> > +       return list_first_entry_or_null(head, struct resource, sibling);
>> > +}
>> > +
>>
>> These names are too generic for new global symbols. A "resource_"
>> prefix is warranted.
>
> Thanks, sounds reasonable, will change them as resource_sibling() and
> resource_first_child(). Or res_sibling()/res_1st_child()?
>

resource_sibling() and resource_first_child()