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Subject[PATCH v6 03/12] mm/sparsemem: Add helpers track active portions of a section at boot
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Prepare for hot{plug,remove} of sub-ranges of a section by tracking a
section active bitmask, each bit representing 2MB (SECTION_SIZE (128M) /
map_active bitmask length (64)). If it turns out that 2MB is too large
of an active tracking granularity it is trivial to increase the size of
the map_active bitmap.

The implications of a partially populated section is that pfn_valid()
needs to go beyond a valid_section() check and read the sub-section
active ranges from the bitmask.

Cc: Michal Hocko <mhocko@suse.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
include/linux/mmzone.h | 29 ++++++++++++++++++++++++++++-
mm/page_alloc.c | 4 +++-
mm/sparse.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 79 insertions(+), 2 deletions(-)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 6726fc175b51..cffde898e345 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -1175,6 +1175,8 @@ struct mem_section_usage {
unsigned long pageblock_flags[0];
};

+void section_active_init(unsigned long pfn, unsigned long nr_pages);
+
struct page;
struct page_ext;
struct mem_section {
@@ -1312,12 +1314,36 @@ static inline struct mem_section *__pfn_to_section(unsigned long pfn)

extern int __highest_present_section_nr;

+static inline int section_active_index(phys_addr_t phys)
+{
+ return (phys & ~(PA_SECTION_MASK)) / SECTION_ACTIVE_SIZE;
+}
+
+#ifdef CONFIG_SPARSEMEM_VMEMMAP
+static inline int pfn_section_valid(struct mem_section *ms, unsigned long pfn)
+{
+ int idx = section_active_index(PFN_PHYS(pfn));
+
+ return !!(ms->usage->map_active & (1UL << idx));
+}
+#else
+static inline int pfn_section_valid(struct mem_section *ms, unsigned long pfn)
+{
+ return 1;
+}
+#endif
+
#ifndef CONFIG_HAVE_ARCH_PFN_VALID
static inline int pfn_valid(unsigned long pfn)
{
+ struct mem_section *ms;
+
if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS)
return 0;
- return valid_section(__nr_to_section(pfn_to_section_nr(pfn)));
+ ms = __nr_to_section(pfn_to_section_nr(pfn));
+ if (!valid_section(ms))
+ return 0;
+ return pfn_section_valid(ms, pfn);
}
#endif

@@ -1349,6 +1375,7 @@ void sparse_init(void);
#define sparse_init() do {} while (0)
#define sparse_index_init(_sec, _nid) do {} while (0)
#define pfn_present pfn_valid
+#define section_active_init(_pfn, _nr_pages) do {} while (0)
#endif /* CONFIG_SPARSEMEM */

/*
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index f671401a7c0b..c9ad28a78018 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -7273,10 +7273,12 @@ void __init free_area_init_nodes(unsigned long *max_zone_pfn)

/* Print out the early node map */
pr_info("Early memory node ranges\n");
- for_each_mem_pfn_range(i, MAX_NUMNODES, &start_pfn, &end_pfn, &nid)
+ for_each_mem_pfn_range(i, MAX_NUMNODES, &start_pfn, &end_pfn, &nid) {
pr_info(" node %3d: [mem %#018Lx-%#018Lx]\n", nid,
(u64)start_pfn << PAGE_SHIFT,
((u64)end_pfn << PAGE_SHIFT) - 1);
+ section_active_init(start_pfn, end_pfn - start_pfn);
+ }

/* Initialise every node */
mminit_verify_pageflags_layout();
diff --git a/mm/sparse.c b/mm/sparse.c
index f87de7ad32c8..5ef2f884c4e1 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -210,6 +210,54 @@ static inline unsigned long first_present_section_nr(void)
return next_present_section_nr(-1);
}

+static unsigned long section_active_mask(unsigned long pfn,
+ unsigned long nr_pages)
+{
+ int idx_start, idx_size;
+ phys_addr_t start, size;
+
+ if (!nr_pages)
+ return 0;
+
+ start = PFN_PHYS(pfn);
+ size = PFN_PHYS(min(nr_pages, PAGES_PER_SECTION
+ - (pfn & ~PAGE_SECTION_MASK)));
+ size = ALIGN(size, SECTION_ACTIVE_SIZE);
+
+ idx_start = section_active_index(start);
+ idx_size = section_active_index(size);
+
+ if (idx_size == 0)
+ return -1;
+ return ((1UL << idx_size) - 1) << idx_start;
+}
+
+void section_active_init(unsigned long pfn, unsigned long nr_pages)
+{
+ int end_sec = pfn_to_section_nr(pfn + nr_pages - 1);
+ int i, start_sec = pfn_to_section_nr(pfn);
+
+ if (!nr_pages)
+ return;
+
+ for (i = start_sec; i <= end_sec; i++) {
+ struct mem_section *ms;
+ unsigned long mask;
+ unsigned long pfns;
+
+ pfns = min(nr_pages, PAGES_PER_SECTION
+ - (pfn & ~PAGE_SECTION_MASK));
+ mask = section_active_mask(pfn, pfns);
+
+ ms = __nr_to_section(i);
+ pr_debug("%s: sec: %d mask: %#018lx\n", __func__, i, mask);
+ ms->usage->map_active = mask;
+
+ pfn += pfns;
+ nr_pages -= pfns;
+ }
+}
+
/* Record a memory area against a node. */
void __init memory_present(int nid, unsigned long start, unsigned long end)
{
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