linux-kernel - Re: [PATCH v2 1/3] mm/memory_hotplug: Export symbol mhp_supports_memmap_on

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Message-ID: <87sf9d26il.fsf@yhuang6-desk2.ccr.corp.intel.com>
Date:   Mon, 24 Jul 2023 14:00:34 +0800
From:   "Huang, Ying" <ying.huang@...el.com>
To:     Vishal Verma <vishal.l.verma@...el.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        David Hildenbrand <david@...hat.com>,
        Oscar Salvador <osalvador@...e.de>,
        Dan Williams <dan.j.williams@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
        <nvdimm@...ts.linux.dev>, <linux-cxl@...r.kernel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Jeff Moyer <jmoyer@...hat.com>
Subject: Re: [PATCH v2 1/3] mm/memory_hotplug: Export symbol
 mhp_supports_memmap_on_memory()

Vishal Verma <vishal.l.verma@...el.com> writes:

> In preparation for dax drivers, which can be built as modules,
> to use this interface, export it with EXPORT_SYMBOL_GPL(). Add a #else
> case for the symbol for builds without CONFIG_MEMORY_HOTPLUG.
>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: David Hildenbrand <david@...hat.com>
> Cc: Oscar Salvador <osalvador@...e.de>
> Cc: Dan Williams <dan.j.williams@...el.com>
> Cc: Dave Jiang <dave.jiang@...el.com>
> Cc: Dave Hansen <dave.hansen@...ux.intel.com>
> Cc: Huang Ying <ying.huang@...el.com>
> Reviewed-by: David Hildenbrand <david@...hat.com>
> Signed-off-by: Vishal Verma <vishal.l.verma@...el.com>
> ---
>  include/linux/memory_hotplug.h | 5 +++++
>  mm/memory_hotplug.c            | 1 +
>  2 files changed, 6 insertions(+)
>
> diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
> index 013c69753c91..fc5da07ad011 100644
> --- a/include/linux/memory_hotplug.h
> +++ b/include/linux/memory_hotplug.h
> @@ -355,6 +355,11 @@ extern int arch_create_linear_mapping(int nid, u64 start, u64 size,
>  				      struct mhp_params *params);
>  void arch_remove_linear_mapping(u64 start, u64 size);
>  extern bool mhp_supports_memmap_on_memory(unsigned long size);
> +#else
> +static inline bool mhp_supports_memmap_on_memory(unsigned long size)
> +{
> +	return false;
> +}
>  #endif /* CONFIG_MEMORY_HOTPLUG */

It appears that there is no user of mhp_supports_memmap_on_memory() that
may be compiled with !CONFIG_MEMORY_HOTPLUG?

--
Best Regards,
Huang, Ying

>  #endif /* __LINUX_MEMORY_HOTPLUG_H */
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 3f231cf1b410..e9bcacbcbae2 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1284,6 +1284,7 @@ bool mhp_supports_memmap_on_memory(unsigned long size)
>  	       IS_ALIGNED(vmemmap_size, PMD_SIZE) &&
>  	       IS_ALIGNED(remaining_size, (pageblock_nr_pages << PAGE_SHIFT));
>  }
> +EXPORT_SYMBOL_GPL(mhp_supports_memmap_on_memory);
>  
>  /*
>   * NOTE: The caller must call lock_device_hotplug() to serialize hotplug