Re: [PATCH] x86/mm: Fix phys_to_target_node() export

[Randy Dunlap <rdunlap@infradead.org>]

On 10/29/20 7:29 PM, Dan Williams wrote:
> The core-mm has a default __weak implementation of phys_to_target_node()
> when the architecture does not override it. That symbol is exported
> for modules. However, while the export in mm/memory_hotplug.c exported
> the symbol in the configuration cases of:
> 
> 	CONFIG_NUMA_KEEP_MEMINFO=y
> 	CONFIG_MEMORY_HOTPLUG=y
> 
> ...and:
> 
> 	CONFIG_NUMA_KEEP_MEMINFO=n
> 	CONFIG_MEMORY_HOTPLUG=y
> 
> ...it failed to export the symbol in the case of:
> 
> 	CONFIG_NUMA_KEEP_MEMINFO=y
> 	CONFIG_MEMORY_HOTPLUG=n
> 
> Always export the symbol from the CONFIG_NUMA_KEEP_MEMINFO section of
> arch/x86/mm/numa.c, and teach mm/memory_hotplug.c to optionally export
> in case arch/x86/mm/numa.c has already performed the export.
> 
> The dependency on NUMA_KEEP_MEMINFO for DEV_DAX_HMEM_DEVICES is invalid
> now that the symbol is properly exported in all combinations of
> CONFIG_NUMA_KEEP_MEMINFO and CONFIG_MEMORY_HOTPLUG. Note that in the
> CONFIG_NUMA=n case no export is needed since their is a dummy static
> inline implementation of phys_to_target_node() in that case.
> 
> Reported-by: Randy Dunlap <rdunlap@infradead.org>
> Reported-by: Thomas Gleixner <tglx@linutronix.de>
> Reported-by: kernel test robot <lkp@intel.com>
> Fixes: a035b6bf863e ("mm/memory_hotplug: introduce default phys_to_target_node() implementation")
> Cc: Joao Martins <joao.m.martins@oracle.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: x86@kernel.org
> Cc: Vishal Verma <vishal.l.verma@intel.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Looks good. Thanks.

Acked-by: Randy Dunlap <rdunlap@infradead.org> # build-tested


> ---
>  arch/x86/mm/numa.c  |    1 +
>  drivers/dax/Kconfig |    1 -
>  mm/memory_hotplug.c |    5 +++++
>  3 files changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/mm/numa.c b/arch/x86/mm/numa.c
> index 44148691d78b..e025947f19e0 100644
> --- a/arch/x86/mm/numa.c
> +++ b/arch/x86/mm/numa.c
> @@ -938,6 +938,7 @@ int phys_to_target_node(phys_addr_t start)
>  
>  	return meminfo_to_nid(&numa_reserved_meminfo, start);
>  }
> +EXPORT_SYMBOL_GPL(phys_to_target_node);
>  
>  int memory_add_physaddr_to_nid(u64 start)
>  {
> diff --git a/drivers/dax/Kconfig b/drivers/dax/Kconfig
> index 567428e10b7b..d2834c2cfa10 100644
> --- a/drivers/dax/Kconfig
> +++ b/drivers/dax/Kconfig
> @@ -50,7 +50,6 @@ config DEV_DAX_HMEM
>  	  Say M if unsure.
>  
>  config DEV_DAX_HMEM_DEVICES
> -	depends on NUMA_KEEP_MEMINFO # for phys_to_target_node()
>  	depends on DEV_DAX_HMEM && DAX=y
>  	def_bool y
>  
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index b44d4c7ba73b..ed326b489674 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -365,9 +365,14 @@ int __weak phys_to_target_node(u64 start)
>  			start);
>  	return 0;
>  }
> +
> +/* If the arch did not export a strong symbol, export the weak one. */
> +#ifndef CONFIG_NUMA_KEEP_MEMINFO
>  EXPORT_SYMBOL_GPL(phys_to_target_node);
>  #endif
>  
> +#endif
> +
>  /* find the smallest valid pfn in the range [start_pfn, end_pfn) */
>  static unsigned long find_smallest_section_pfn(int nid, struct zone *zone,
>  				     unsigned long start_pfn,
> 
> 


-- 
~Randy