Subject: Re: [PATCH v2 4/6] mm/memory_hotplug: Rename walk_memory_range() and pass start+size instead of pfns

From: Nathan Chancellor <[email-masked]>
Date: Thu, 20 Jun 2019 09:05:07 -0700

On Thu, Jun 20, 2019 at 12:35:18PM +0200, David Hildenbrand wrote:
> walk_memory_range() was once used to iterate over sections. Now, it
> iterates over memory blocks. Rename the function, fixup the
> documentation. Also, pass start+size instead of PFNs, which is what most
> callers already have at hand. (we'll rework link_mem_sections() most
> probably soon)
> 
> Follow-up patches wil rework, simplify, and move walk_memory_blocks() to
> drivers/base/memory.c.
> 
> Note: walk_memory_blocks() only works correctly right now if the
> start_pfn is aligned to a section start. This is the case right now,
> but we'll generalize the function in a follow up patch so the semantics
> match the documentation.
> 
> Cc: Benjamin Herrenschmidt <[email-masked]>
> Cc: Paul Mackerras <[email-masked]>
> Cc: Michael Ellerman <[email-masked]>
> Cc: "Rafael J. Wysocki" <[email-masked]>
> Cc: Len Brown <[email-masked]>
> Cc: Greg Kroah-Hartman <[email-masked]>
> Cc: David Hildenbrand <[email-masked]>
> Cc: Rashmica Gupta <[email-masked]>
> Cc: Andrew Morton <[email-masked]>
> Cc: Pavel Tatashin <[email-masked]>
> Cc: Anshuman Khandual <[email-masked]>
> Cc: Michael Neuling <[email-masked]>
> Cc: Thomas Gleixner <[email-masked]>
> Cc: Oscar Salvador <[email-masked]>
> Cc: Michal Hocko <[email-masked]>
> Cc: Wei Yang <[email-masked]>
> Cc: Juergen Gross <[email-masked]>
> Cc: Qian Cai <[email-masked]>
> Cc: Arun KS <[email-masked]>
> Signed-off-by: David Hildenbrand <[email-masked]>
> ---
>  arch/powerpc/platforms/powernv/memtrace.c | 22 ++++++++++-----------
>  drivers/acpi/acpi_memhotplug.c            | 19 ++++--------------
>  drivers/base/node.c                       |  5 +++--
>  include/linux/memory_hotplug.h            |  2 +-
>  mm/memory_hotplug.c                       | 24 ++++++++++++-----------
>  5 files changed, 32 insertions(+), 40 deletions(-)
> 
> diff --git a/arch/powerpc/platforms/powernv/memtrace.c b/arch/powerpc/platforms/powernv/memtrace.c
> index 5e53c1392d3b..8c82c041afe6 100644
> --- a/arch/powerpc/platforms/powernv/memtrace.c
> +++ b/arch/powerpc/platforms/powernv/memtrace.c
> @@ -70,23 +70,24 @@ static int change_memblock_state(struct memory_block *mem, void *arg)
>  /* called with device_hotplug_lock held */
>  static bool memtrace_offline_pages(u32 nid, u64 start_pfn, u64 nr_pages)
>  {
> +	const unsigned long start = PFN_PHYS(start_pfn);
> +	const unsigned long size = PFN_PHYS(nr_pages);
>  	u64 end_pfn = start_pfn + nr_pages - 1;

This variable should be removed:

arch/powerpc/platforms/powernv/memtrace.c:75:6: warning: unused variable 'end_pfn' [-Wunused-variable]
        u64 end_pfn = start_pfn + nr_pages - 1;
            ^
1 warning generated.

https://travis-ci.com/ClangBuiltLinux/continuous-integration/jobs/209576737

Cheers,
Nathan

>  
> -	if (walk_memory_range(start_pfn, end_pfn, NULL,
> -	    check_memblock_online))
> +	if (walk_memory_blocks(start, size, NULL, check_memblock_online))
>  		return false;
>  
> -	walk_memory_range(start_pfn, end_pfn, (void *)MEM_GOING_OFFLINE,
> -			  change_memblock_state);
> +	walk_memory_blocks(start, size, (void *)MEM_GOING_OFFLINE,
> +			   change_memblock_state);
>  
>  	if (offline_pages(start_pfn, nr_pages)) {
> -		walk_memory_range(start_pfn, end_pfn, (void *)MEM_ONLINE,
> -				  change_memblock_state);
> +		walk_memory_blocks(start, size, (void *)MEM_ONLINE,
> +				   change_memblock_state);
>  		return false;
>  	}
>  
> -	walk_memory_range(start_pfn, end_pfn, (void *)MEM_OFFLINE,
> -			  change_memblock_state);
> +	walk_memory_blocks(start, size, (void *)MEM_OFFLINE,
> +			   change_memblock_state);
>  
>  
>  	return true;
> @@ -242,9 +243,8 @@ static int memtrace_online(void)
>  		 */
>  		if (!memhp_auto_online) {
>  			lock_device_hotplug();
> -			walk_memory_range(PFN_DOWN(ent->start),
> -					  PFN_UP(ent->start + ent->size - 1),
> -					  NULL, online_mem_block);
> +			walk_memory_blocks(ent->start, ent->size, NULL,
> +					   online_mem_block);
>  			unlock_device_hotplug();
>  		}
>  
> diff --git a/drivers/acpi/acpi_memhotplug.c b/drivers/acpi/acpi_memhotplug.c
> index db013dc21c02..e294f44a7850 100644
> --- a/drivers/acpi/acpi_memhotplug.c
> +++ b/drivers/acpi/acpi_memhotplug.c
> @@ -155,16 +155,6 @@ static int acpi_memory_check_device(struct acpi_memory_device *mem_device)
>  	return 0;
>  }
>  
> -static unsigned long acpi_meminfo_start_pfn(struct acpi_memory_info *info)
> -{
> -	return PFN_DOWN(info->start_addr);
> -}
> -
> -static unsigned long acpi_meminfo_end_pfn(struct acpi_memory_info *info)
> -{
> -	return PFN_UP(info->start_addr + info->length-1);
> -}
> -
>  static int acpi_bind_memblk(struct memory_block *mem, void *arg)
>  {
>  	return acpi_bind_one(&mem->dev, arg);
> @@ -173,9 +163,8 @@ static int acpi_bind_memblk(struct memory_block *mem, void *arg)
>  static int acpi_bind_memory_blocks(struct acpi_memory_info *info,
>  				   struct acpi_device *adev)
>  {
> -	return walk_memory_range(acpi_meminfo_start_pfn(info),
> -				 acpi_meminfo_end_pfn(info), adev,
> -				 acpi_bind_memblk);
> +	return walk_memory_blocks(info->start_addr, info->length, adev,
> +				  acpi_bind_memblk);
>  }
>  
>  static int acpi_unbind_memblk(struct memory_block *mem, void *arg)
> @@ -186,8 +175,8 @@ static int acpi_unbind_memblk(struct memory_block *mem, void *arg)
>  
>  static void acpi_unbind_memory_blocks(struct acpi_memory_info *info)
>  {
> -	walk_memory_range(acpi_meminfo_start_pfn(info),
> -			  acpi_meminfo_end_pfn(info), NULL, acpi_unbind_memblk);
> +	walk_memory_blocks(info->start_addr, info->length, NULL,
> +			   acpi_unbind_memblk);
>  }
>  
>  static int acpi_memory_enable_device(struct acpi_memory_device *mem_device)
> diff --git a/drivers/base/node.c b/drivers/base/node.c
> index e6364e3e3e31..d8c02e65df68 100644
> --- a/drivers/base/node.c
> +++ b/drivers/base/node.c
> @@ -833,8 +833,9 @@ void unregister_memory_block_under_nodes(struct memory_block *mem_blk)
>  
>  int link_mem_sections(int nid, unsigned long start_pfn, unsigned long end_pfn)
>  {
> -	return walk_memory_range(start_pfn, end_pfn, (void *)&nid,
> -					register_mem_sect_under_node);
> +	return walk_memory_blocks(PFN_PHYS(start_pfn),
> +				  PFN_PHYS(end_pfn - start_pfn), (void *)&nid,
> +				  register_mem_sect_under_node);
>  }
>  
>  #ifdef CONFIG_HUGETLBFS
> diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
> index 79e0add6a597..d9fffc34949f 100644
> --- a/include/linux/memory_hotplug.h
> +++ b/include/linux/memory_hotplug.h
> @@ -340,7 +340,7 @@ static inline void __remove_memory(int nid, u64 start, u64 size) {}
>  #endif /* CONFIG_MEMORY_HOTREMOVE */
>  
>  extern void __ref free_area_init_core_hotplug(int nid);
> -extern int walk_memory_range(unsigned long start_pfn, unsigned long end_pfn,
> +extern int walk_memory_blocks(unsigned long start, unsigned long size,
>  		void *arg, int (*func)(struct memory_block *, void *));
>  extern int __add_memory(int nid, u64 start, u64 size);
>  extern int add_memory(int nid, u64 start, u64 size);
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index a88c5f334e5a..122a7d31efdd 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1126,8 +1126,7 @@ int __ref add_memory_resource(int nid, struct resource *res)
>  
>  	/* online pages if requested */
>  	if (memhp_auto_online)
> -		walk_memory_range(PFN_DOWN(start), PFN_UP(start + size - 1),
> -				  NULL, online_memory_block);
> +		walk_memory_blocks(start, size, NULL, online_memory_block);
>  
>  	return ret;
>  error:
> @@ -1665,20 +1664,24 @@ int offline_pages(unsigned long start_pfn, unsigned long nr_pages)
>  #endif /* CONFIG_MEMORY_HOTREMOVE */
>  
>  /**
> - * walk_memory_range - walks through all mem sections in [start_pfn, end_pfn)
> - * @start_pfn: start pfn of the memory range
> - * @end_pfn: end pfn of the memory range
> + * walk_memory_blocks - walk through all present memory blocks overlapped
> + *			by the range [start, start + size)
> + *
> + * @start: start address of the memory range
> + * @size: size of the memory range
>   * @arg: argument passed to func
> - * @func: callback for each memory section walked
> + * @func: callback for each memory block walked
>   *
> - * This function walks through all present mem sections in range
> - * [start_pfn, end_pfn) and call func on each mem section.
> + * This function walks through all present memory blocks overlapped by the
> + * range [start, start + size), calling func on each memory block.
>   *
>   * Returns the return value of func.
>   */
> -int walk_memory_range(unsigned long start_pfn, unsigned long end_pfn,
> +int walk_memory_blocks(unsigned long start, unsigned long size,
>  		void *arg, int (*func)(struct memory_block *, void *))
>  {
> +	const unsigned long start_pfn = PFN_DOWN(start);
> +	const unsigned long end_pfn = PFN_UP(start + size - 1);
>  	struct memory_block *mem = NULL;
>  	struct mem_section *section;
>  	unsigned long pfn, section_nr;
> @@ -1824,8 +1827,7 @@ static int __ref try_remove_memory(int nid, u64 start, u64 size)
>  	 * whether all memory blocks in question are offline and return error
>  	 * if this is not the case.
>  	 */
> -	rc = walk_memory_range(PFN_DOWN(start), PFN_UP(start + size - 1), NULL,
> -			       check_memblock_offlined_cb);
> +	rc = walk_memory_blocks(start, size, NULL, check_memblock_offlined_cb);
>  	if (rc)
>  		goto done;
>  
> -- 
> 2.21.0
>