Commit 326e1b8f authored by Dan Williams's avatar Dan Williams Committed by Linus Torvalds
Browse files

mm/sparsemem: introduce a SECTION_IS_EARLY flag 

In preparation for sub-section hotplug, track whether a given section
was created during early memory initialization, or later via memory
hotplug.  This distinction is needed to maintain the coarse expectation
that pfn_valid() returns true for any pfn within a given section even if
that section has pages that are reserved from the page allocator.

For example one of the of goals of subsection hotplug is to support
cases where the system physical memory layout collides System RAM and
PMEM within a section.  Several pfn_valid() users expect to just check
if a section is valid, but they are not careful to check if the given
pfn is within a "System RAM" boundary and instead expect pgdat
information to further validate the pfn.

Rather than unwind those paths to make their pfn_valid() queries more
precise a follow on patch uses the SECTION_IS_EARLY flag to maintain the
traditional expectation that pfn_valid() returns true for all early
sections.

Link: https://lore.kernel.org/lkml/1560366952-10660-1-git-send-email-cai@lca.pw/
Link: http://lkml.kernel.org/r/156092350358.979959.5817209875548072819.stgit@dwillia2-desk3.amr.corp.intel.com


Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
Reported-by: default avatarQian Cai <cai@lca.pw>
Tested-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>	[ppc64]
Reviewed-by: default avatarOscar Salvador <osalvador@suse.de>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Logan Gunthorpe <logang@deltatee.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Jane Chu <jane.chu@oracle.com>
Cc: Jeff Moyer <jmoyer@redhat.com>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: Toshi Kani <toshi.kani@hpe.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Yang <richardw.yang@linux.intel.com>
Cc: Jason Gunthorpe <jgg@mellanox.com>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent f1eca35a

include/linux/mmzone.h

+7 −1
Original line number Diff line number Diff line
@@ -1260,7 +1260,8 @@ extern size_t mem_section_usage_size(void); 
#define	SECTION_MARKED_PRESENT	(1UL<<0)

#define SECTION_HAS_MEM_MAP	(1UL<<1)

#define SECTION_IS_ONLINE	(1UL<<2)

#define SECTION_MAP_LAST_BIT	(1UL<<3)

#define SECTION_IS_EARLY	(1UL<<3)

#define SECTION_MAP_LAST_BIT	(1UL<<4)

#define SECTION_MAP_MASK	(~(SECTION_MAP_LAST_BIT-1))

#define SECTION_NID_SHIFT	3
@@ -1286,6 +1287,11 @@ static inline int valid_section(struct mem_section *section) 
	return (section && (section->section_mem_map & SECTION_HAS_MEM_MAP));

}



static inline int early_section(struct mem_section *section)

{

	return (section && (section->section_mem_map & SECTION_IS_EARLY));

}



static inline int valid_section_nr(unsigned long nr)

{

	return valid_section(__nr_to_section(nr));

mm/sparse.c

+9 −11
Original line number Diff line number Diff line
@@ -288,11 +288,11 @@ struct page *sparse_decode_mem_map(unsigned long coded_mem_map, unsigned long pn 


static void __meminit sparse_init_one_section(struct mem_section *ms,

		unsigned long pnum, struct page *mem_map,

		struct mem_section_usage *usage)

		struct mem_section_usage *usage, unsigned long flags)

{

	ms->section_mem_map &= ~SECTION_MAP_MASK;

	ms->section_mem_map |= sparse_encode_mem_map(mem_map, pnum) |

							SECTION_HAS_MEM_MAP;

	ms->section_mem_map |= sparse_encode_mem_map(mem_map, pnum)

		| SECTION_HAS_MEM_MAP | flags;

	ms->usage = usage;

}
@@ -497,7 +497,8 @@ static void __init sparse_init_nid(int nid, unsigned long pnum_begin, 
			goto failed;

		}

		check_usemap_section_nr(nid, usage);

		sparse_init_one_section(__nr_to_section(pnum), pnum, map, usage);

		sparse_init_one_section(__nr_to_section(pnum), pnum, map, usage,

				SECTION_IS_EARLY);

		usage = (void *) usage + mem_section_usage_size();

	}

	sparse_buffer_fini();
@@ -732,7 +733,7 @@ int __meminit sparse_add_one_section(int nid, unsigned long start_pfn, 


	set_section_nid(section_nr, nid);

	section_mark_present(ms);

	sparse_init_one_section(ms, section_nr, memmap, usage);

	sparse_init_one_section(ms, section_nr, memmap, usage, 0);



out:

	if (ret < 0) {
@@ -772,19 +773,16 @@ static inline void clear_hwpoisoned_pages(struct page *memmap, int nr_pages) 
}

#endif



static void free_section_usage(struct page *memmap,

static void free_section_usage(struct mem_section *ms, struct page *memmap,

		struct mem_section_usage *usage, struct vmem_altmap *altmap)

{

	struct page *usage_page;



	if (!usage)

		return;



	usage_page = virt_to_page(usage);

	/*

	 * Check to see if allocation came from hot-plug-add

	 */

	if (PageSlab(usage_page) || PageCompound(usage_page)) {

	if (!early_section(ms)) {

		kfree(usage);

		if (memmap)

			__kfree_section_memmap(memmap, altmap);
@@ -816,6 +814,6 @@ void sparse_remove_one_section(struct mem_section *ms, unsigned long map_offset, 


	clear_hwpoisoned_pages(memmap + map_offset,

			PAGES_PER_SECTION - map_offset);

	free_section_usage(memmap, usage, altmap);

	free_section_usage(ms, memmap, usage, altmap);

}

#endif /* CONFIG_MEMORY_HOTPLUG */

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