Commit 0a9f9f62 authored by Baoquan He's avatar Baoquan He Committed by Linus Torvalds
Browse files

mm/sparse.c: only use subsection map in VMEMMAP case 



Currently, to support subsection aligned memory region adding for pmem,
subsection map is added to track which subsection is present.

However, config ZONE_DEVICE depends on SPARSEMEM_VMEMMAP.  It means
subsection map only makes sense when SPARSEMEM_VMEMMAP enabled.  For the
classic sparse, it's meaningless.  Even worse, it may confuse people when
checking code related to the classic sparse.

About the classic sparse which doesn't support subsection hotplug, Dan
said it's more because the effort and maintenance burden outweighs the
benefit.  Besides, the current 64 bit ARCHes all enable
SPARSEMEM_VMEMMAP_ENABLE by default.

Combining the above reasons, no need to provide subsection map and the
relevant handling for the classic sparse.  Let's remove them.

Signed-off-by: default avatarBaoquan He <bhe@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Reviewed-by: default avatarDavid Hildenbrand <david@redhat.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Wei Yang <richard.weiyang@gmail.com>
Link: http://lkml.kernel.org/r/20200312124414.439-4-bhe@redhat.com


Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 37bc1502

include/linux/mmzone.h

+2 −0
Original line number Diff line number Diff line
@@ -1143,7 +1143,9 @@ static inline unsigned long section_nr_to_pfn(unsigned long sec) 
#define SUBSECTION_ALIGN_DOWN(pfn) ((pfn) & PAGE_SUBSECTION_MASK)



struct mem_section_usage {

#ifdef CONFIG_SPARSEMEM_VMEMMAP

	DECLARE_BITMAP(subsection_map, SUBSECTIONS_PER_SECTION);

#endif

	/* See declaration of similar field in struct zone */

	unsigned long pageblock_flags[0];

};

mm/sparse.c

+25 −0
Original line number Diff line number Diff line
@@ -209,6 +209,7 @@ static inline unsigned long first_present_section_nr(void) 
	return next_present_section_nr(-1);

}



#ifdef CONFIG_SPARSEMEM_VMEMMAP

static void subsection_mask_set(unsigned long *map, unsigned long pfn,

		unsigned long nr_pages)

{
@@ -243,6 +244,11 @@ void __init subsection_map_init(unsigned long pfn, unsigned long nr_pages) 
		nr_pages -= pfns;

	}

}

#else

void __init subsection_map_init(unsigned long pfn, unsigned long nr_pages)

{

}

#endif



/* Record a memory area against a node. */

void __init memory_present(int nid, unsigned long start, unsigned long end)
@@ -705,6 +711,7 @@ static void free_map_bootmem(struct page *memmap) 
}

#endif /* CONFIG_SPARSEMEM_VMEMMAP */



#ifdef CONFIG_SPARSEMEM_VMEMMAP

static int clear_subsection_map(unsigned long pfn, unsigned long nr_pages)

{

	DECLARE_BITMAP(map, SUBSECTIONS_PER_SECTION) = { 0 };
@@ -731,6 +738,17 @@ static bool is_subsection_map_empty(struct mem_section *ms) 
	return bitmap_empty(&ms->usage->subsection_map[0],

			    SUBSECTIONS_PER_SECTION);

}

#else

static int clear_subsection_map(unsigned long pfn, unsigned long nr_pages)

{

	return 0;

}



static bool is_subsection_map_empty(struct mem_section *ms)

{

	return true;

}

#endif



static void section_deactivate(unsigned long pfn, unsigned long nr_pages,

		struct vmem_altmap *altmap)
@@ -792,6 +810,7 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages, 
		ms->section_mem_map = (unsigned long)NULL;

}



#ifdef CONFIG_SPARSEMEM_VMEMMAP

static int fill_subsection_map(unsigned long pfn, unsigned long nr_pages)

{

	struct mem_section *ms = __pfn_to_section(pfn);
@@ -813,6 +832,12 @@ static int fill_subsection_map(unsigned long pfn, unsigned long nr_pages) 


	return rc;

}

#else

static int fill_subsection_map(unsigned long pfn, unsigned long nr_pages)

{

	return 0;

}

#endif



static struct page * __meminit section_activate(int nid, unsigned long pfn,

		unsigned long nr_pages, struct vmem_altmap *altmap)

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