[RFC PATCH 5/7] mm: memory_hotplug, sparse: enable memory hotplug/hotremove subsections

Zi Yan
2021-05-06T15:26:21Z

From: Zi Yan <ziy@nvidia.com>

Remove the section size alignment checks for memory hotplug/hotremove,
so that we can online/offline subsection memory.

Signed-off-by: Zi Yan <ziy@nvidia.com>
---
mm/memory_hotplug.c | 16 +++++++++-------
mm/page_isolation.c | 4 ----
mm/sparse.c | 17 ++++++++++++++---
3 files changed, 23 insertions(+), 14 deletions(-)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 6e93b0ecc5cb..5384bb62ac10 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -661,12 +661,15 @@ static void online_pages_range(unsigned long start_pfn, unsigned long nr_pages)
* When using memmap_on_memory, the range might not be aligned to
* MAX_ORDER_NR_PAGES - 1, but pageblock aligned. __ffs() will detect
* this and the first chunk to online will be pageblock_nr_pages.
+ * When onlining subsections, the range might be smaller than MAX_ORDER
+ * - 1, use __ffs(nr_pages) to get the right size.
*/
for (pfn = start_pfn; pfn < end_pfn;) {
- int order = min(MAX_ORDER - 1UL, __ffs(pfn));
+ int order = min3(MAX_ORDER - 1UL, __ffs(pfn), __ffs(nr_pages));

(*online_page_callback)(pfn_to_page(pfn), order);
pfn += (1UL << order);
+ nr_pages -= (1UL << order);
}

/* mark all involved sections as online */
@@ -912,16 +915,16 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, struct zone *z
struct memory_notify arg;

/*
- * {on,off}lining is constrained to full memory sections (or more
+ * {on,off}lining is constrained to memory subsections (or more
* precisly to memory blocks from the user space POV).
* memmap_on_memory is an exception because it reserves initial part
* of the physical memory space for vmemmaps. That space is pageblock
* aligned.
*/
if (WARN_ON_ONCE(!nr_pages ||
- !IS_ALIGNED(pfn, pageblock_nr_pages) ||
- !IS_ALIGNED(pfn + nr_pages, PAGES_PER_SECTION)))
+ !IS_ALIGNED(pfn + nr_pages, PAGES_PER_SUBSECTION))) {
return -EINVAL;
+ }

mem_hotplug_begin();

@@ -1702,15 +1705,14 @@ int __ref offline_pages(unsigned long start_pfn, unsigned long nr_pages)
char *reason;

/*
- * {on,off}lining is constrained to full memory sections (or more
+ * {on,off}lining is constrained to memory subsections (or more
* precisly to memory blocks from the user space POV).
* memmap_on_memory is an exception because it reserves initial part
* of the physical memory space for vmemmaps. That space is pageblock
* aligned.
*/
if (WARN_ON_ONCE(!nr_pages ||
- !IS_ALIGNED(start_pfn, pageblock_nr_pages) ||
- !IS_ALIGNED(start_pfn + nr_pages, PAGES_PER_SECTION)))
+ !IS_ALIGNED(start_pfn + nr_pages, PAGES_PER_SUBSECTION)))
return -EINVAL;

mem_hotplug_begin();
diff --git a/mm/page_isolation.c b/mm/page_isolation.c
index c1b9b8848382..7f1791faf03f 100644
--- a/mm/page_isolation.c
+++ b/mm/page_isolation.c
@@ -147,7 +147,6 @@ __first_valid_page(unsigned long pfn, unsigned long nr_pages)
* be MIGRATE_ISOLATE.
* @start_pfn: The lower PFN of the range to be isolated.
* @end_pfn: The upper PFN of the range to be isolated.
- * start_pfn/end_pfn must be aligned to pageblock_order.
* @migratetype: Migrate type to set in error recovery.
* @flags: The following flags are allowed (they can be combined in
* a bit mask)
@@ -190,9 +189,6 @@ int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
unsigned long undo_pfn;
struct page *page;

- BUG_ON(!IS_ALIGNED(start_pfn, pageblock_nr_pages));
- BUG_ON(!IS_ALIGNED(end_pfn, pageblock_nr_pages));
-
for (pfn = start_pfn;
pfn < end_pfn;
pfn += pageblock_nr_pages) {
diff --git a/mm/sparse.c b/mm/sparse.c
index 1c2957807882..09b5e6978ab0 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -251,7 +251,8 @@ void __init subsection_map_init(unsigned long pfn, unsigned long nr_pages)
/* Record a memory area against a node. */
static void __init memory_present(int nid, unsigned long start, unsigned long end)
{
- unsigned long pfn;
+ unsigned long pfn, nr_pages;
+ unsigned long section, end_sec, start_sec;

#ifdef CONFIG_SPARSEMEM_EXTREME
if (unlikely(!mem_section)) {
@@ -268,9 +269,17 @@ static void __init memory_present(int nid, unsigned long start, unsigned long en

start &= PAGE_SECTION_MASK;
mminit_validate_memmodel_limits(&start, &end);
- for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION) {
- unsigned long section = pfn_to_section_nr(pfn);
+ start_sec = pfn_to_section_nr(start);
+ end_sec = pfn_to_section_nr(end - 1);
+ pfn = start;
+ nr_pages = end - start;
+
+ for (section = start_sec; section <= end_sec; section++) {
struct mem_section *ms;
+ unsigned long pfns;
+
+ pfns = min(nr_pages, PAGES_PER_SECTION
+ - (pfn & ~PAGE_SECTION_MASK));

sparse_index_init(section, nid);
set_section_nid(section, nid);
@@ -281,6 +290,8 @@ static void __init memory_present(int nid, unsigned long start, unsigned long en
SECTION_IS_ONLINE;
section_mark_present(ms);
}
+ pfn += pfns;
+ nr_pages -= pfns;
}
}

--
2.30.2