[PATCH v4 03/13] mm: introduce struct mem_section_usage to track partial population of a section

From: Dan Williams
Date: Thu Mar 16 2017 - 02:12:38 EST

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'struct mem_section_usage' combines the existing 'pageblock_flags' bitmap
with a new 'map_active' bitmap. The new bitmap enables the memory
hot{plug,remove} implementation to act on incremental sub-divisions of
a section. The primary impetus for this functionality is to support
platforms that mix "System RAM" and "Persistent Memory" within a single
section. We want to be able to hotplug "Persistent Memory" to extend a
partially populated section and share that section between ZONE_DEVICE and
ZONE_NORMAL/MOVABLE memory.

This introduces a pointer to the new 'map_active' bitmap through struct
mem_section, but otherwise should not change any behavior.

Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Logan Gunthorpe <logang@xxxxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Stephen Bates <stephen.bates@xxxxxxxxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
---
include/linux/mmzone.h | 21 +++++++++-
mm/memory_hotplug.c | 4 +-
mm/page_alloc.c | 2 -
mm/sparse.c | 98 ++++++++++++++++++++++++++----------------------
4 files changed, 75 insertions(+), 50 deletions(-)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index ffa9503d5be5..82a1af3afa04 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -1070,6 +1070,19 @@ static inline unsigned long early_pfn_to_nid(unsigned long pfn)
#define SECTION_ALIGN_UP(pfn) (((pfn) + PAGES_PER_SECTION - 1) & PAGE_SECTION_MASK)
#define SECTION_ALIGN_DOWN(pfn) ((pfn) & PAGE_SECTION_MASK)

+#define SECTION_ACTIVE_SIZE ((1UL << SECTION_SIZE_BITS) / BITS_PER_LONG)
+#define SECTION_ACTIVE_MASK (~(SECTION_ACTIVE_SIZE - 1))
+
+struct mem_section_usage {
+ /*
+ * SECTION_ACTIVE_SIZE portions of the section that are populated in
+ * the memmap
+ */
+ unsigned long map_active;
+ /* See declaration of similar field in struct zone */
+ unsigned long pageblock_flags[0];
+};
+
struct page;
struct page_ext;
struct mem_section {
@@ -1087,8 +1100,7 @@ struct mem_section {
*/
unsigned long section_mem_map;

- /* See declaration of similar field in struct zone */
- unsigned long *pageblock_flags;
+ struct mem_section_usage *usage;
#ifdef CONFIG_PAGE_EXTENSION
/*
* If SPARSEMEM, pgdat doesn't have page_ext pointer. We use
@@ -1119,6 +1131,11 @@ extern struct mem_section *mem_section[NR_SECTION_ROOTS];
extern struct mem_section mem_section[NR_SECTION_ROOTS][SECTIONS_PER_ROOT];
#endif

+static inline unsigned long *section_to_usemap(struct mem_section *ms)
+{
+ return ms->usage->pageblock_flags;
+}
+
static inline struct mem_section *__nr_to_section(unsigned long nr)
{
if (!mem_section[SECTION_NR_TO_ROOT(nr)])
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index e1751ca002fa..07accab8441d 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -235,7 +235,7 @@ static void register_page_bootmem_info_section(unsigned long start_pfn)
for (i = 0; i < mapsize; i++, page++)
get_page_bootmem(section_nr, page, SECTION_INFO);

- usemap = __nr_to_section(section_nr)->pageblock_flags;
+ usemap = section_to_usemap(__nr_to_section(section_nr));
page = virt_to_page(usemap);

mapsize = PAGE_ALIGN(usemap_size()) >> PAGE_SHIFT;
@@ -261,7 +261,7 @@ static void register_page_bootmem_info_section(unsigned long start_pfn)

register_page_bootmem_memmap(section_nr, memmap, PAGES_PER_SECTION);

- usemap = __nr_to_section(section_nr)->pageblock_flags;
+ usemap = section_to_usemap(__nr_to_section(section_nr));
page = virt_to_page(usemap);

mapsize = PAGE_ALIGN(usemap_size()) >> PAGE_SHIFT;
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 6cbde310abed..50858eef1cc4 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -357,7 +357,7 @@ static inline unsigned long *get_pageblock_bitmap(struct page *page,
unsigned long pfn)
{
#ifdef CONFIG_SPARSEMEM
- return __pfn_to_section(pfn)->pageblock_flags;
+ return section_to_usemap(__pfn_to_section(pfn));
#else
return page_zone(page)->pageblock_flags;
#endif /* CONFIG_SPARSEMEM */
diff --git a/mm/sparse.c b/mm/sparse.c
index db6bf3c97ea2..d0d4c005dc60 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -233,15 +233,15 @@ struct page *sparse_decode_mem_map(unsigned long coded_mem_map, unsigned long pn

static int __meminit sparse_init_one_section(struct mem_section *ms,
unsigned long pnum, struct page *mem_map,
- unsigned long *pageblock_bitmap)
+ struct mem_section_usage *usage)
{
if (!present_section(ms))
return -EINVAL;

ms->section_mem_map &= ~SECTION_MAP_MASK;
ms->section_mem_map |= sparse_encode_mem_map(mem_map, pnum) |
- SECTION_HAS_MEM_MAP;
- ms->pageblock_flags = pageblock_bitmap;
+ SECTION_HAS_MEM_MAP;
+ ms->usage = usage;

return 1;
}
@@ -255,9 +255,13 @@ unsigned long usemap_size(void)
}

#ifdef CONFIG_MEMORY_HOTPLUG
-static unsigned long *__kmalloc_section_usemap(void)
+static struct mem_section_usage *__alloc_section_usage(void)
{
- return kmalloc(usemap_size(), GFP_KERNEL);
+ struct mem_section_usage *usage;
+
+ usage = kzalloc(sizeof(*usage) + usemap_size(), GFP_KERNEL);
+ /* TODO: allocate the map_active bitmap */
+ return usage;
}
#endif /* CONFIG_MEMORY_HOTPLUG */

@@ -293,7 +297,8 @@ sparse_early_usemaps_alloc_pgdat_section(struct pglist_data *pgdat,
return p;
}

-static void __init check_usemap_section_nr(int nid, unsigned long *usemap)
+static void __init check_usemap_section_nr(int nid,
+ struct mem_section_usage *usage)
{
unsigned long usemap_snr, pgdat_snr;
static unsigned long old_usemap_snr = NR_MEM_SECTIONS;
@@ -301,7 +306,7 @@ static void __init check_usemap_section_nr(int nid, unsigned long *usemap)
struct pglist_data *pgdat = NODE_DATA(nid);
int usemap_nid;

- usemap_snr = pfn_to_section_nr(__pa(usemap) >> PAGE_SHIFT);
+ usemap_snr = pfn_to_section_nr(__pa(usage) >> PAGE_SHIFT);
pgdat_snr = pfn_to_section_nr(__pa(pgdat) >> PAGE_SHIFT);
if (usemap_snr == pgdat_snr)
return;
@@ -336,7 +341,8 @@ sparse_early_usemaps_alloc_pgdat_section(struct pglist_data *pgdat,
return memblock_virt_alloc_node_nopanic(size, pgdat->node_id);
}

-static void __init check_usemap_section_nr(int nid, unsigned long *usemap)
+static void __init check_usemap_section_nr(int nid,
+ struct mem_section_usage *usage)
{
}
#endif /* CONFIG_MEMORY_HOTREMOVE */
@@ -344,26 +350,27 @@ static void __init check_usemap_section_nr(int nid, unsigned long *usemap)
static void __init sparse_early_usemaps_alloc_node(void *data,
unsigned long pnum_begin,
unsigned long pnum_end,
- unsigned long usemap_count, int nodeid)
+ unsigned long usage_count, int nodeid)
{
- void *usemap;
+ void *usage;
unsigned long pnum;
- unsigned long **usemap_map = (unsigned long **)data;
- int size = usemap_size();
+ struct mem_section_usage **usage_map = data;
+ int size = sizeof(struct mem_section_usage) + usemap_size();

- usemap = sparse_early_usemaps_alloc_pgdat_section(NODE_DATA(nodeid),
- size * usemap_count);
- if (!usemap) {
+ usage = sparse_early_usemaps_alloc_pgdat_section(NODE_DATA(nodeid),
+ size * usage_count);
+ if (!usage) {
pr_warn("%s: allocation failed\n", __func__);
return;
}

+ memset(usage, 0, size * usage_count);
for (pnum = pnum_begin; pnum < pnum_end; pnum++) {
if (!present_section_nr(pnum))
continue;
- usemap_map[pnum] = usemap;
- usemap += size;
- check_usemap_section_nr(nodeid, usemap_map[pnum]);
+ usage_map[pnum] = usage;
+ usage += size;
+ check_usemap_section_nr(nodeid, usage_map[pnum]);
}
}

@@ -468,7 +475,7 @@ void __weak __meminit vmemmap_populate_print_last(void)

/**
* alloc_usemap_and_memmap - memory alloction for pageblock flags and vmemmap
- * @map: usemap_map for pageblock flags or mmap_map for vmemmap
+ * @map: usage_map for mem_section_usage or mmap_map for vmemmap
*/
static void __init alloc_usemap_and_memmap(void (*alloc_func)
(void *, unsigned long, unsigned long,
@@ -521,10 +528,9 @@ static void __init alloc_usemap_and_memmap(void (*alloc_func)
*/
void __init sparse_init(void)
{
+ struct mem_section_usage *usage, **usage_map;
unsigned long pnum;
struct page *map;
- unsigned long *usemap;
- unsigned long **usemap_map;
int size;
#ifdef CONFIG_SPARSEMEM_ALLOC_MEM_MAP_TOGETHER
int size2;
@@ -539,21 +545,21 @@ void __init sparse_init(void)

/*
* map is using big page (aka 2M in x86 64 bit)
- * usemap is less one page (aka 24 bytes)
+ * usage is less one page (aka 24 bytes)
* so alloc 2M (with 2M align) and 24 bytes in turn will
* make next 2M slip to one more 2M later.
* then in big system, the memory will have a lot of holes...
* here try to allocate 2M pages continuously.
*
* powerpc need to call sparse_init_one_section right after each
- * sparse_early_mem_map_alloc, so allocate usemap_map at first.
+ * sparse_early_mem_map_alloc, so allocate usage_map at first.
*/
- size = sizeof(unsigned long *) * NR_MEM_SECTIONS;
- usemap_map = memblock_virt_alloc(size, 0);
- if (!usemap_map)
- panic("can not allocate usemap_map\n");
+ size = sizeof(struct mem_section_usage *) * NR_MEM_SECTIONS;
+ usage_map = memblock_virt_alloc(size, 0);
+ if (!usage_map)
+ panic("can not allocate usage_map\n");
alloc_usemap_and_memmap(sparse_early_usemaps_alloc_node,
- (void *)usemap_map);
+ (void *)usage_map);

#ifdef CONFIG_SPARSEMEM_ALLOC_MEM_MAP_TOGETHER
size2 = sizeof(struct page *) * NR_MEM_SECTIONS;
@@ -568,8 +574,8 @@ void __init sparse_init(void)
if (!present_section_nr(pnum))
continue;

- usemap = usemap_map[pnum];
- if (!usemap)
+ usage = usage_map[pnum];
+ if (!usage)
continue;

#ifdef CONFIG_SPARSEMEM_ALLOC_MEM_MAP_TOGETHER
@@ -581,7 +587,7 @@ void __init sparse_init(void)
continue;

sparse_init_one_section(__nr_to_section(pnum), pnum, map,
- usemap);
+ usage);
}

vmemmap_populate_print_last();
@@ -589,7 +595,7 @@ void __init sparse_init(void)
#ifdef CONFIG_SPARSEMEM_ALLOC_MEM_MAP_TOGETHER
memblock_free_early(__pa(map_map), size2);
#endif
- memblock_free_early(__pa(usemap_map), size);
+ memblock_free_early(__pa(usage_map), size);
}

#ifdef CONFIG_MEMORY_HOTPLUG
@@ -693,9 +699,9 @@ int __meminit sparse_add_one_section(struct zone *zone, unsigned long start_pfn)
{
unsigned long section_nr = pfn_to_section_nr(start_pfn);
struct pglist_data *pgdat = zone->zone_pgdat;
+ static struct mem_section_usage *usage;
struct mem_section *ms;
struct page *memmap;
- unsigned long *usemap;
unsigned long flags;
int ret;

@@ -709,8 +715,8 @@ int __meminit sparse_add_one_section(struct zone *zone, unsigned long start_pfn)
memmap = kmalloc_section_memmap(section_nr, pgdat->node_id);
if (!memmap)
return -ENOMEM;
- usemap = __kmalloc_section_usemap();
- if (!usemap) {
+ usage = __alloc_section_usage();
+ if (!usage) {
__kfree_section_memmap(memmap);
return -ENOMEM;
}
@@ -727,12 +733,12 @@ int __meminit sparse_add_one_section(struct zone *zone, unsigned long start_pfn)

ms->section_mem_map |= SECTION_MARKED_PRESENT;

- ret = sparse_init_one_section(ms, section_nr, memmap, usemap);
+ ret = sparse_init_one_section(ms, section_nr, memmap, usage);

out:
pgdat_resize_unlock(pgdat, &flags);
if (ret <= 0) {
- kfree(usemap);
+ kfree(usage);
__kfree_section_memmap(memmap);
}
return ret;
@@ -760,19 +766,20 @@ static inline void clear_hwpoisoned_pages(struct page *memmap, int nr_pages)
}
#endif

-static void free_section_usemap(struct page *memmap, unsigned long *usemap)
+static void free_section_usage(struct page *memmap,
+ struct mem_section_usage *usage)
{
struct page *usemap_page;

- if (!usemap)
+ if (!usage)
return;

- usemap_page = virt_to_page(usemap);
+ usemap_page = virt_to_page(usage->pageblock_flags);
/*
* Check to see if allocation came from hot-plug-add
*/
if (PageSlab(usemap_page) || PageCompound(usemap_page)) {
- kfree(usemap);
+ kfree(usage);
if (memmap)
__kfree_section_memmap(memmap);
return;
@@ -790,23 +797,24 @@ static void free_section_usemap(struct page *memmap, unsigned long *usemap)
void sparse_remove_one_section(struct zone *zone, struct mem_section *ms,
unsigned long map_offset)
{
+ unsigned long flags;
struct page *memmap = NULL;
- unsigned long *usemap = NULL, flags;
+ struct mem_section_usage *usage = NULL;
struct pglist_data *pgdat = zone->zone_pgdat;

pgdat_resize_lock(pgdat, &flags);
if (ms->section_mem_map) {
- usemap = ms->pageblock_flags;
+ usage = ms->usage;
memmap = sparse_decode_mem_map(ms->section_mem_map,
__section_nr(ms));
ms->section_mem_map = 0;
- ms->pageblock_flags = NULL;
+ ms->usage = NULL;
}
pgdat_resize_unlock(pgdat, &flags);

clear_hwpoisoned_pages(memmap + map_offset,
PAGES_PER_SECTION - map_offset);
- free_section_usemap(memmap, usemap);
+ free_section_usage(memmap, usage);
}
#endif /* CONFIG_MEMORY_HOTREMOVE */
#endif /* CONFIG_MEMORY_HOTPLUG */

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