From: Baoquan He <bhe@redhat.com>
To: Borislav Petkov <bp@suse.de>
Cc: linux-kernel@vger.kernel.org, akpm@linux-foundation.org,
robh+dt@kernel.org, dan.j.williams@intel.com,
nicolas.pitre@linaro.org, josh@joshtriplett.org,
"Thomas Gleixner" <tglx@linutronix.de>,
"Brijesh Singh" <brijesh.singh@amd.com>,
"Jérôme Glisse" <jglisse@redhat.com>,
"Tom Lendacky" <thomas.lendacky@amd.com>,
"Wei Yang" <richard.weiyang@gmail.com>
Subject: Re: [PATCH v3 2/3] resource: add walk_system_ram_res_rev()
Date: Thu, 26 Apr 2018 16:56:49 +0800 [thread overview]
Message-ID: <20180426085649.GC18395@localhost.localdomain> (raw)
In-Reply-To: <20180419100745.GC3896@pd.tnic>
Sorry to all reviewers, I had a redhat urgent issue, this patchset
discussing is delayed.
On 04/19/18 at 12:07pm, Borislav Petkov wrote:
> On Thu, Apr 19, 2018 at 08:18:47AM +0800, Baoquan He wrote:
> > This function, being a variant of walk_system_ram_res() introduced in
> > commit 8c86e70acead ("resource: provide new functions to walk through
> > resources"), walks through a list of all the resources of System RAM
> > in reversed order, i.e., from higher to lower.
> >
> > It will be used in kexec_file code.
>
> Of course, what is missing is the big *WHY* you need this to happen this
> way...
Sorry for that, I just ran scripts/get_maintainer.pl to get expert's
name and added them into each patch. The reason this change is made is
in patch 3/3. Test robot reported a code bug on the latest kernel, will
repost and CC everyone in all patches.
Rob Herring asked the same question in v2, I explained to him. The
discussion can be found here:
https://lkml.org/lkml/2018/4/10/484
>
> > /*
> > + * This function, being a variant of walk_system_ram_res(), calls the @func
> > + * callback against all memory ranges of type System RAM which are marked as
> > + * IORESOURCE_SYSTEM_RAM and IORESOUCE_BUSY in reversed order, i.e., from
> > + * higher to lower.
> > + */
> > +int walk_system_ram_res_rev(u64 start, u64 end, void *arg,
> > + int (*func)(struct resource *, void *))
> > +{
> > + unsigned long flags;
> > + struct resource *res;
> > + int ret = -1;
> > +
> > + flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
> > +
> > + read_lock(&resource_lock);
> > + list_for_each_entry_reverse(res, &iomem_resource.child, sibling) {
>
> ... and the other thing that I'm not clear on is why are you
> slapping this function just like that instead of extending
> __walk_iomem_res_desc() to do reverse direction too?
Yes, I planned to do as you said when started to write code. After investigation,
I changed to use the way of this patch. Because __walk_iomem_res_desc()
provides two interfaces by calling find_next_iomem_res(). If
'first_level_children_only' is true, it only iterates system RAM
resource; if 'first_level_children_only' is false, it does depth first
iteration in iomem_resource. The 1st interface is only used by
walk_system_ram_res() and walk_mem_res(). While the 2nd interface need
call find_next_iomem_res() which resorts to next_resource().
next_resource() will check 'sibling_only' to decide if iterate
iomem_resource's children, or walk over all resources of iomem_resource
with depth first. For walk_system_ram_res_rev(), we only need to iterate
iomem_resource's children, and seems no one has requirement to
iterate all iomem_resource's children and grand children
revresedly. For simplifying code implementation, I just did as in this
patch, surely, if any suggestion or scenario given about the reversed
iteration of all resources, I can change to add below functions, and
based on them to implement walk_system_ram_res_rev().
walk_system_ram_res_rev
->__walk_iomem_res_desc_rev
->find_next_iomem_res_rev
->next_resource_rev
Thanks
Baoquan
>
> SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
> --
next prev parent reply other threads:[~2018-04-26 8:57 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-19 0:18 [PATCH v3 0/3] resource: Use list_head to link sibling resource Baoquan He
2018-04-19 0:18 ` [PATCH v3 1/3] " Baoquan He
2018-04-19 0:18 ` Baoquan He
2018-04-19 0:18 ` Baoquan He
2018-04-19 0:18 ` Baoquan He
2018-04-26 1:18 ` Wei Yang
2018-04-26 1:18 ` Wei Yang
2018-04-26 1:18 ` Wei Yang
2018-04-26 1:18 ` Wei Yang
2018-05-07 1:14 ` Baoquan He
2018-05-07 1:14 ` Baoquan He
2018-05-07 1:14 ` Baoquan He
2018-05-07 1:14 ` Baoquan He
2018-05-08 11:48 ` Wei Yang
2018-05-08 11:48 ` Wei Yang
2018-05-08 11:48 ` Wei Yang
2018-05-08 11:48 ` Wei Yang
2018-05-08 12:11 ` Baoquan He
2018-05-08 12:11 ` Baoquan He
2018-05-08 12:11 ` Baoquan He
2018-05-08 23:41 ` Wei Yang
2018-05-08 23:41 ` Wei Yang
2018-05-08 23:41 ` Wei Yang
2018-05-08 23:41 ` Wei Yang
2018-04-26 3:01 ` kbuild test robot
2018-04-26 3:01 ` kbuild test robot
2018-04-26 3:01 ` kbuild test robot
2018-05-06 6:31 ` Baoquan He
2018-05-06 6:31 ` Baoquan He
2018-05-06 6:31 ` Baoquan He
2018-05-06 6:31 ` Baoquan He
2018-04-26 3:23 ` kbuild test robot
2018-04-26 3:23 ` kbuild test robot
2018-04-26 3:23 ` kbuild test robot
2018-05-06 6:30 ` Baoquan He
2018-05-06 6:30 ` Baoquan He
2018-05-06 6:30 ` Baoquan He
2018-05-06 6:30 ` Baoquan He
2018-04-19 0:18 ` [PATCH v3 2/3] resource: add walk_system_ram_res_rev() Baoquan He
2018-04-19 10:07 ` Borislav Petkov
2018-04-26 8:56 ` Baoquan He [this message]
2018-04-26 11:09 ` Borislav Petkov
2018-04-26 13:22 ` Baoquan He
2018-05-04 10:16 ` Borislav Petkov
2018-05-06 6:19 ` Baoquan He
2018-04-19 0:18 ` [PATCH v3 3/3] kexec_file: Load kernel at top of system RAM if required Baoquan He
2018-04-19 0:18 ` Baoquan He
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