Hi Dan

-----Original Message-----
From: Dan Williams <redacted>
Sent: Wednesday, July 8, 2020 11:57 AM
To: Justin He <redacted>
Cc: Michal Hocko <mhocko@kernel.org>; David Hildenbrand <redacted>;
Catalin Marinas [off-list ref]; Will Deacon [off-list ref];
Vishal Verma [off-list ref]; Dave Jiang [off-list ref];
Andrew Morton [off-list ref]; Mike Rapoport
[off-list ref]; Baoquan He [off-list ref]; Chuhong Yuan
[off-list ref]; linux-arm-kernel@lists.infradead.org; linux-
kernel@vger.kernel.org; linux-mm@kvack.org; linux-nvdimm@lists.01.org;
Kaly Xin [off-list ref]
Subject: Re: [PATCH v2 1/3] arm64/numa: export memory_add_physaddr_to_nid
as EXPORT_SYMBOL_GPL

On Tue, Jul 7, 2020 at 7:20 PM Justin He [off-list ref] wrote:

quoted

Hi Michal and David

quoted

-----Original Message-----
From: Michal Hocko <mhocko@kernel.org>
Sent: Tuesday, July 7, 2020 7:55 PM
To: Justin He <redacted>
Cc: Catalin Marinas <Catalin.Marinas@arm.com>; Will Deacon
[off-list ref]; Dan Williams [off-list ref]; Vishal

Verma

quoted

quoted

[off-list ref]; Dave Jiang [off-list ref]; Andrew
Morton [off-list ref]; Mike Rapoport [off-list ref];
Baoquan He [off-list ref]; Chuhong Yuan [off-list ref];

linux-

quoted

quoted

arm-kernel@lists.infradead.org; linux-kernel@vger.kernel.org; linux-
mm@kvack.org; linux-nvdimm@lists.01.org; Kaly Xin [off-list ref]
Subject: Re: [PATCH v2 1/3] arm64/numa: export

memory_add_physaddr_to_nid

quoted

quoted

as EXPORT_SYMBOL_GPL

On Tue 07-07-20 13:59:15, Jia He wrote:

quoted

This exports memory_add_physaddr_to_nid() for module driver to use.

memory_add_physaddr_to_nid() is a fallback option to get the nid in

case

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quoted

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NUMA_NO_NID is detected.

Suggested-by: David Hildenbrand <redacted>
Signed-off-by: Jia He <redacted>
---
 arch/arm64/mm/numa.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/mm/numa.c b/arch/arm64/mm/numa.c
index aafcee3e3f7e..7eeb31740248 100644
--- a/arch/arm64/mm/numa.c
+++ b/arch/arm64/mm/numa.c

@@ -464,10 +464,11 @@ void __init arm64_numa_init(void)

 /*
  * We hope that we will be hotplugging memory on nodes we already

know

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about,

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- * such that acpi_get_node() succeeds and we never fall back to

this...

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+ * such that acpi_get_node() succeeds. But when SRAT is not present,

the node

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+ * id may be probed as NUMA_NO_NODE by acpi, Here provide a

fallback

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option.

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  */
 int memory_add_physaddr_to_nid(u64 addr)
 {
-   pr_warn("Unknown node for memory at 0x%llx, assuming node 0\n",

addr);

quoted

    return 0;
 }
+EXPORT_SYMBOL_GPL(memory_add_physaddr_to_nid);

Does it make sense to export a noop function? Wouldn't make more sense
to simply make it static inline somewhere in a header? I haven't

checked

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whether there is an easy way to do that sanely bu this just hit my

eyes.

quoted

Okay, I can make a change in memory_hotplug.h, sth like:

--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h

@@ -149,13 +149,13 @@ int add_pages(int nid, unsigned long start_pfn,

unsigned long nr_pages,

quoted

              struct mhp_params *params);
 #endif /* ARCH_HAS_ADD_PAGES */

-#ifdef CONFIG_NUMA
-extern int memory_add_physaddr_to_nid(u64 start);
-#else
+#if !defined(CONFIG_NUMA) || !defined(memory_add_physaddr_to_nid)
 static inline int memory_add_physaddr_to_nid(u64 start)
 {
        return 0;
 }
+#else
+extern int memory_add_physaddr_to_nid(u64 start);
 #endif

And then check the memory_add_physaddr_to_nid() helper on all arches,
if it is noop(return 0), I can simply remove it.
if it is not noop, after the helper,
#define memory_add_physaddr_to_nid

What do you think of this proposal?

Especially for architectures that use memblock info for numa info
(which seems to be everyone except x86) why not implement a generic
memory_add_physaddr_to_nid() that does:

int memory_add_physaddr_to_nid(u64 addr)
{
        unsigned long start_pfn, end_pfn, pfn = PHYS_PFN(addr);
        int nid;

        for_each_online_node(nid) {
                get_pfn_range_for_nid(nid, &start_pfn, &end_pfn);
                if (pfn >= start_pfn && pfn <= end_pfn)
                        return nid;
        }
        return NUMA_NO_NODE;
}

Thanks for your suggestion,
Could I wrap the codes and let memory_add_physaddr_to_nid simply invoke
phys_to_target_node()? 


--
Cheers,
Justin (Jia He)


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