[PATCH v7 00/12] mm: Sub-section memory hotplug support

[PATCH v7 00/12] mm: Sub-section memory hotplug support

[Dan Williams]

Changes since v6 [1]:

- Rebase on next-20190501, no related conflicts or updates

- Fix boot crash due to inaccurate setup of the initial section
  ->map_active bitmask caused by multiple activations of the same
  section. (Jane, Jeff)

- Fix pmem startup crash when devm_memremap_pages() needs to instantiate
  a new section. (Jeff)

- Drop mhp_restrictions for the __remove_pages() path in favor of
  find_memory_block() to detect cases where section-aligned remove is
  required (David)

- Add "[PATCH v7 06/12] mm/hotplug: Kill is_dev_zone() usage in
  __remove_pages()"

- Cleanup shrink_{zone,pgdat}_span to remove no longer necessary @ms
  section variables. (Oscar)

- Add subsection_check() to the __add_pages() path to prevent
  inadvertent sub-section misuse.

[1]: https://lore.kernel.org/lkml/155552633539.2015392.2477781120122237934.stgit@dwillia2-desk3.amr.corp.intel.com/

---
[merge logistics]

Hi Andrew,

I believe this is ready for another spin in -mm now that the boot
regression has been squashed. In a chat with Michal last night at LSF/MM
I submitted to his assertion that the boot regression validates the
general concern that there were/are subtle dependencies on sections
beyond what I found to date by code inspection. Of course I want to
relieve the pain that the section constraint inflicts on libnvdimm and
devm_memremap_pages() as soon as possible (i.e. v5.2), but deferment to
v5.3 to give Michal time to do an in-depth look is also acceptable.

---
[cover letter]

The memory hotplug section is an arbitrary / convenient unit for memory
hotplug. 'Section-size' units have bled into the user interface
('memblock' sysfs) and can not be changed without breaking existing
userspace. The section-size constraint, while mostly benign for typical
memory hotplug, has and continues to wreak havoc with 'device-memory'
use cases, persistent memory (pmem) in particular. Recall that pmem uses
devm_memremap_pages(), and subsequently arch_add_memory(), to allocate a
'struct page' memmap for pmem. However, it does not use the 'bottom
half' of memory hotplug, i.e. never marks pmem pages online and never
exposes the userspace memblock interface for pmem. This leaves an
opening to redress the section-size constraint.

To date, the libnvdimm subsystem has attempted to inject padding to
satisfy the internal constraints of arch_add_memory(). Beyond
complicating the code, leading to bugs [2], wasting memory, and limiting
configuration flexibility, the padding hack is broken when the platform
changes this physical memory alignment of pmem from one boot to the
next. Device failure (intermittent or permanent) and physical
reconfiguration are events that can cause the platform firmware to
change the physical placement of pmem on a subsequent boot, and device
failure is an everyday event in a data-center.

It turns out that sections are only a hard requirement of the
user-facing interface for memory hotplug and with a bit more
infrastructure sub-section arch_add_memory() support can be added for
kernel internal usages like devm_memremap_pages(). Here is an analysis
of the current design assumptions in the current code and how they are
addressed in the new implementation:

Current design assumptions:

- Sections that describe boot memory (early sections) are never
  unplugged / removed.

- pfn_valid(), in the CONFIG_SPARSEMEM_VMEMMAP=y, case devolves to a
  valid_section() check

- __add_pages() and helper routines assume all operations occur in
  PAGES_PER_SECTION units.

- The memblock sysfs interface only comprehends full sections

New design assumptions:

- Sections are instrumented with a sub-section bitmask to track (on x86)
  individual 2MB sub-divisions of a 128MB section.

- Partially populated early sections can be extended with additional
  sub-sections, and those sub-sections can be removed with
  arch_remove_memory(). With this in place we no longer lose usable memory
  capacity to padding.

- pfn_valid() is updated to look deeper than valid_section() to also check the
  active-sub-section mask. This indication is in the same cacheline as
  the valid_section() so the performance impact is expected to be
  negligible. So far the lkp robot has not reported any regressions.

- Outside of the core vmemmap population routines which are replaced,
  other helper routines like shrink_{zone,pgdat}_span() are updated to
  handle the smaller granularity. Core memory hotplug routines that deal
  with online memory are not touched.

- The existing memblock sysfs user api guarantees / assumptions are
  not touched since this capability is limited to !online
  !memblock-sysfs-accessible sections.

Meanwhile the issue reports continue to roll in from users that do not
understand when and how the 128MB constraint will bite them. The current
implementation relied on being able to support at least one misaligned
namespace, but that immediately falls over on any moderately complex
namespace creation attempt. Beyond the initial problem of 'System RAM'
colliding with pmem, and the unsolvable problem of physical alignment
changes, Linux is now being exposed to platforms that collide pmem
ranges with other pmem ranges by default [3]. In short,
devm_memremap_pages() has pushed the venerable section-size constraint
past the breaking point, and the simplicity of section-aligned
arch_add_memory() is no longer tenable.

These patches are exposed to the kbuild robot on my libnvdimm-pending
branch [4], and a preview of the unit test for this functionality is
available on the 'subsection-pending' branch of ndctl [5].

[2]: https://lore.kernel.org/r/155000671719.348031.2347363160141119237.stgit@dwillia2-desk3.amr.corp.intel.com
[3]: https://github.com/pmem/ndctl/issues/76
[4]: https://git.kernel.org/pub/scm/linux/kernel/git/djbw/nvdimm.git/log/?h=libnvdimm-pending
[5]: https://github.com/pmem/ndctl/commit/7c59b4867e1c

---

Dan Williams (12):
      mm/sparsemem: Introduce struct mem_section_usage
      mm/sparsemem: Introduce common definitions for the size and mask of a section
      mm/sparsemem: Add helpers track active portions of a section at boot
      mm/hotplug: Prepare shrink_{zone,pgdat}_span for sub-section removal
      mm/sparsemem: Convert kmalloc_section_memmap() to populate_section_memmap()
      mm/hotplug: Kill is_dev_zone() usage in __remove_pages()
      mm: Kill is_dev_zone() helper
      mm/sparsemem: Prepare for sub-section ranges
      mm/sparsemem: Support sub-section hotplug
      mm/devm_memremap_pages: Enable sub-section remap
      libnvdimm/pfn: Fix fsdax-mode namespace info-block zero-fields
      libnvdimm/pfn: Stop padding pmem namespaces to section alignment


 arch/x86/mm/init_64.c          |    4 
 drivers/nvdimm/dax_devs.c      |    2 
 drivers/nvdimm/pfn.h           |   12 -
 drivers/nvdimm/pfn_devs.c      |   93 +++-------
 include/linux/memory_hotplug.h |    7 -
 include/linux/mm.h             |    4 
 include/linux/mmzone.h         |   72 ++++++--
 kernel/memremap.c              |   63 +++----
 mm/hmm.c                       |    2 
 mm/memory_hotplug.c            |  172 ++++++++++---------
 mm/page_alloc.c                |    8 +
 mm/sparse-vmemmap.c            |   21 ++
 mm/sparse.c                    |  370 ++++++++++++++++++++++++++++------------
 13 files changed, 490 insertions(+), 340 deletions(-)

[PATCH v7 01/12] mm/sparsemem: Introduce struct mem_section_usage

[Dan Williams]

Towards enabling memory hotplug to track partial population of a
section, introduce 'struct mem_section_usage'.

A pointer to a 'struct mem_section_usage' instance replaces the existing
pointer to a 'pageblock_flags' bitmap. Effectively it adds one more
'unsigned long' beyond the 'pageblock_flags' (usemap) allocation to
house 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 motivation for this functionality is to support platforms
that mix "System RAM" and "Persistent Memory" within a single section,
or multiple PMEM ranges with different mapping lifetimes within a single
section. The section restriction for hotplug has caused an ongoing saga
of hacks and bugs for devm_memremap_pages() users.

Beyond the fixups to teach existing paths how to retrieve the 'usemap'
from a section, and updates to usemap allocation path, there are no
expected behavior changes.

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 |   23 ++++++++++++--
 mm/memory_hotplug.c    |   18 ++++++-----
 mm/page_alloc.c        |    2 +
 mm/sparse.c            |   81 ++++++++++++++++++++++++------------------------
 4 files changed, 71 insertions(+), 53 deletions(-)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 70394cabaf4e..f0bbd85dc19a 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -1160,6 +1160,19 @@ static inline unsigned long section_nr_to_pfn(unsigned long sec)
 #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 {
@@ -1177,8 +1190,7 @@ 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
@@ -1209,6 +1221,11 @@ extern struct mem_section **mem_section;
 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)
 {
 #ifdef CONFIG_SPARSEMEM_EXTREME
@@ -1220,7 +1237,7 @@ static inline struct mem_section *__nr_to_section(unsigned long nr)
 	return &mem_section[SECTION_NR_TO_ROOT(nr)][nr & SECTION_ROOT_MASK];
 }
 extern int __section_nr(struct mem_section* ms);
-extern unsigned long usemap_size(void);
+extern size_t mem_section_usage_size(void);
 
 /*
  * We use the lower bits of the mem_map pointer to store
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 328878b6799d..a76fc6a6e9fe 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -165,9 +165,10 @@ void put_page_bootmem(struct page *page)
 #ifndef CONFIG_SPARSEMEM_VMEMMAP
 static void register_page_bootmem_info_section(unsigned long start_pfn)
 {
-	unsigned long *usemap, mapsize, section_nr, i;
+	unsigned long mapsize, section_nr, i;
 	struct mem_section *ms;
 	struct page *page, *memmap;
+	struct mem_section_usage *usage;
 
 	section_nr = pfn_to_section_nr(start_pfn);
 	ms = __nr_to_section(section_nr);
@@ -187,10 +188,10 @@ 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 = ms->pageblock_flags;
-	page = virt_to_page(usemap);
+	usage = ms->usage;
+	page = virt_to_page(usage);
 
-	mapsize = PAGE_ALIGN(usemap_size()) >> PAGE_SHIFT;
+	mapsize = PAGE_ALIGN(mem_section_usage_size()) >> PAGE_SHIFT;
 
 	for (i = 0; i < mapsize; i++, page++)
 		get_page_bootmem(section_nr, page, MIX_SECTION_INFO);
@@ -199,9 +200,10 @@ static void register_page_bootmem_info_section(unsigned long start_pfn)
 #else /* CONFIG_SPARSEMEM_VMEMMAP */
 static void register_page_bootmem_info_section(unsigned long start_pfn)
 {
-	unsigned long *usemap, mapsize, section_nr, i;
+	unsigned long mapsize, section_nr, i;
 	struct mem_section *ms;
 	struct page *page, *memmap;
+	struct mem_section_usage *usage;
 
 	section_nr = pfn_to_section_nr(start_pfn);
 	ms = __nr_to_section(section_nr);
@@ -210,10 +212,10 @@ static void register_page_bootmem_info_section(unsigned long start_pfn)
 
 	register_page_bootmem_memmap(section_nr, memmap, PAGES_PER_SECTION);
 
-	usemap = ms->pageblock_flags;
-	page = virt_to_page(usemap);
+	usage = ms->usage;
+	page = virt_to_page(usage);
 
-	mapsize = PAGE_ALIGN(usemap_size()) >> PAGE_SHIFT;
+	mapsize = PAGE_ALIGN(mem_section_usage_size()) >> PAGE_SHIFT;
 
 	for (i = 0; i < mapsize; i++, page++)
 		get_page_bootmem(section_nr, page, MIX_SECTION_INFO);
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 1f99db76b1ff..61c2b54a5b61 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -403,7 +403,7 @@ 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 fd13166949b5..f87de7ad32c8 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -288,33 +288,31 @@ 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,
-		unsigned long *pageblock_bitmap)
+		struct mem_section_usage *usage)
 {
 	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;
+	ms->usage = usage;
 }
 
-unsigned long usemap_size(void)
+static unsigned long usemap_size(void)
 {
 	return BITS_TO_LONGS(SECTION_BLOCKFLAGS_BITS) * sizeof(unsigned long);
 }
 
-#ifdef CONFIG_MEMORY_HOTPLUG
-static unsigned long *__kmalloc_section_usemap(void)
+size_t mem_section_usage_size(void)
 {
-	return kmalloc(usemap_size(), GFP_KERNEL);
+	return sizeof(struct mem_section_usage) + usemap_size();
 }
-#endif /* CONFIG_MEMORY_HOTPLUG */
 
 #ifdef CONFIG_MEMORY_HOTREMOVE
-static unsigned long * __init
+static struct mem_section_usage * __init
 sparse_early_usemaps_alloc_pgdat_section(struct pglist_data *pgdat,
 					 unsigned long size)
 {
+	struct mem_section_usage *usage;
 	unsigned long goal, limit;
-	unsigned long *p;
 	int nid;
 	/*
 	 * A page may contain usemaps for other sections preventing the
@@ -330,15 +328,16 @@ sparse_early_usemaps_alloc_pgdat_section(struct pglist_data *pgdat,
 	limit = goal + (1UL << PA_SECTION_SHIFT);
 	nid = early_pfn_to_nid(goal >> PAGE_SHIFT);
 again:
-	p = memblock_alloc_try_nid(size, SMP_CACHE_BYTES, goal, limit, nid);
-	if (!p && limit) {
+	usage = memblock_alloc_try_nid(size, SMP_CACHE_BYTES, goal, limit, nid);
+	if (!usage && limit) {
 		limit = 0;
 		goto again;
 	}
-	return p;
+	return usage;
 }
 
-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;
@@ -352,7 +351,7 @@ static void __init check_usemap_section_nr(int nid, unsigned long *usemap)
 		old_pgdat_snr = NR_MEM_SECTIONS;
 	}
 
-	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;
@@ -380,14 +379,15 @@ static void __init check_usemap_section_nr(int nid, unsigned long *usemap)
 		usemap_snr, pgdat_snr, nid);
 }
 #else
-static unsigned long * __init
+static struct mem_section_usage * __init
 sparse_early_usemaps_alloc_pgdat_section(struct pglist_data *pgdat,
 					 unsigned long size)
 {
 	return memblock_alloc_node(size, SMP_CACHE_BYTES, 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 */
@@ -474,14 +474,13 @@ static void __init sparse_init_nid(int nid, unsigned long pnum_begin,
 				   unsigned long pnum_end,
 				   unsigned long map_count)
 {
-	unsigned long pnum, usemap_longs, *usemap;
+	struct mem_section_usage *usage;
+	unsigned long pnum;
 	struct page *map;
 
-	usemap_longs = BITS_TO_LONGS(SECTION_BLOCKFLAGS_BITS);
-	usemap = sparse_early_usemaps_alloc_pgdat_section(NODE_DATA(nid),
-							  usemap_size() *
-							  map_count);
-	if (!usemap) {
+	usage = sparse_early_usemaps_alloc_pgdat_section(NODE_DATA(nid),
+			mem_section_usage_size() * map_count);
+	if (!usage) {
 		pr_err("%s: node[%d] usemap allocation failed", __func__, nid);
 		goto failed;
 	}
@@ -497,9 +496,9 @@ static void __init sparse_init_nid(int nid, unsigned long pnum_begin,
 			pnum_begin = pnum;
 			goto failed;
 		}
-		check_usemap_section_nr(nid, usemap);
-		sparse_init_one_section(__nr_to_section(pnum), pnum, map, usemap);
-		usemap += usemap_longs;
+		check_usemap_section_nr(nid, usage);
+		sparse_init_one_section(__nr_to_section(pnum), pnum, map, usage);
+		usage = (void *) usage + mem_section_usage_size();
 	}
 	sparse_buffer_fini();
 	return;
@@ -701,9 +700,9 @@ int __meminit sparse_add_one_section(int nid, unsigned long start_pfn,
 				     struct vmem_altmap *altmap)
 {
 	unsigned long section_nr = pfn_to_section_nr(start_pfn);
+	struct mem_section_usage *usage;
 	struct mem_section *ms;
 	struct page *memmap;
-	unsigned long *usemap;
 	int ret;
 
 	/*
@@ -717,8 +716,8 @@ int __meminit sparse_add_one_section(int nid, unsigned long start_pfn,
 	memmap = kmalloc_section_memmap(section_nr, nid, altmap);
 	if (!memmap)
 		return -ENOMEM;
-	usemap = __kmalloc_section_usemap();
-	if (!usemap) {
+	usage = kzalloc(mem_section_usage_size(), GFP_KERNEL);
+	if (!usage) {
 		__kfree_section_memmap(memmap, altmap);
 		return -ENOMEM;
 	}
@@ -736,11 +735,11 @@ int __meminit sparse_add_one_section(int nid, unsigned long start_pfn,
 	page_init_poison(memmap, sizeof(struct page) * PAGES_PER_SECTION);
 
 	section_mark_present(ms);
-	sparse_init_one_section(ms, section_nr, memmap, usemap);
+	sparse_init_one_section(ms, section_nr, memmap, usage);
 
 out:
 	if (ret < 0) {
-		kfree(usemap);
+		kfree(usage);
 		__kfree_section_memmap(memmap, altmap);
 	}
 	return ret;
@@ -777,20 +776,20 @@ static inline void clear_hwpoisoned_pages(struct page *memmap, int nr_pages)
 }
 #endif
 
-static void free_section_usemap(struct page *memmap, unsigned long *usemap,
-		struct vmem_altmap *altmap)
+static void free_section_usage(struct page *memmap,
+		struct mem_section_usage *usage, struct vmem_altmap *altmap)
 {
-	struct page *usemap_page;
+	struct page *usage_page;
 
-	if (!usemap)
+	if (!usage)
 		return;
 
-	usemap_page = virt_to_page(usemap);
+	usage_page = virt_to_page(usage);
 	/*
 	 * Check to see if allocation came from hot-plug-add
 	 */
-	if (PageSlab(usemap_page) || PageCompound(usemap_page)) {
-		kfree(usemap);
+	if (PageSlab(usage_page) || PageCompound(usage_page)) {
+		kfree(usage);
 		if (memmap)
 			__kfree_section_memmap(memmap, altmap);
 		return;
@@ -809,19 +808,19 @@ void sparse_remove_one_section(struct zone *zone, struct mem_section *ms,
 		unsigned long map_offset, struct vmem_altmap *altmap)
 {
 	struct page *memmap = NULL;
-	unsigned long *usemap = NULL;
+	struct mem_section_usage *usage = NULL;
 
 	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;
 	}
 
 	clear_hwpoisoned_pages(memmap + map_offset,
 			PAGES_PER_SECTION - map_offset);
-	free_section_usemap(memmap, usemap, altmap);
+	free_section_usage(memmap, usage, altmap);
 }
 #endif /* CONFIG_MEMORY_HOTREMOVE */
 #endif /* CONFIG_MEMORY_HOTPLUG */

Re: [PATCH v7 01/12] mm/sparsemem: Introduce struct mem_section_usage

[Oscar Salvador]

On Wed, May 01, 2019 at 10:55:27PM -0700, Dan Williams wrote:
> Towards enabling memory hotplug to track partial population of a
> section, introduce 'struct mem_section_usage'.
> 
> A pointer to a 'struct mem_section_usage' instance replaces the existing
> pointer to a 'pageblock_flags' bitmap. Effectively it adds one more
> 'unsigned long' beyond the 'pageblock_flags' (usemap) allocation to
> house 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 motivation for this functionality is to support platforms
> that mix "System RAM" and "Persistent Memory" within a single section,
> or multiple PMEM ranges with different mapping lifetimes within a single
> section. The section restriction for hotplug has caused an ongoing saga
> of hacks and bugs for devm_memremap_pages() users.
> 
> Beyond the fixups to teach existing paths how to retrieve the 'usemap'
> from a section, and updates to usemap allocation path, there are no
> expected behavior changes.
> 
> 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>

Reviewed-by: Oscar Salvador <osalvador@suse.de>

-- 
Oscar Salvador
SUSE L3

[PATCH v7 02/12] mm/sparsemem: Introduce common definitions for the size and mask of a section

[Dan Williams]

Up-level the local section size and mask from kernel/memremap.c to
global definitions.  These will be used by the new sub-section hotplug
support.

Cc: Michal Hocko <mhocko@suse.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 include/linux/mmzone.h |    2 ++
 kernel/memremap.c      |   10 ++++------
 mm/hmm.c               |    2 --
 3 files changed, 6 insertions(+), 8 deletions(-)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index f0bbd85dc19a..6726fc175b51 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -1134,6 +1134,8 @@ static inline unsigned long early_pfn_to_nid(unsigned long pfn)
  * PFN_SECTION_SHIFT		pfn to/from section number
  */
 #define PA_SECTION_SHIFT	(SECTION_SIZE_BITS)
+#define PA_SECTION_SIZE		(1UL << PA_SECTION_SHIFT)
+#define PA_SECTION_MASK		(~(PA_SECTION_SIZE-1))
 #define PFN_SECTION_SHIFT	(SECTION_SIZE_BITS - PAGE_SHIFT)
 
 #define NR_MEM_SECTIONS		(1UL << SECTIONS_SHIFT)
diff --git a/kernel/memremap.c b/kernel/memremap.c
index 4e59d29245f4..f355586ea54a 100644
--- a/kernel/memremap.c
+++ b/kernel/memremap.c
@@ -14,8 +14,6 @@
 #include <linux/hmm.h>
 
 static DEFINE_XARRAY(pgmap_array);
-#define SECTION_MASK ~((1UL << PA_SECTION_SHIFT) - 1)
-#define SECTION_SIZE (1UL << PA_SECTION_SHIFT)
 
 #if IS_ENABLED(CONFIG_DEVICE_PRIVATE)
 vm_fault_t device_private_entry_fault(struct vm_area_struct *vma,
@@ -98,8 +96,8 @@ static void devm_memremap_pages_release(void *data)
 		put_page(pfn_to_page(pfn));
 
 	/* pages are dead and unused, undo the arch mapping */
-	align_start = res->start & ~(SECTION_SIZE - 1);
-	align_size = ALIGN(res->start + resource_size(res), SECTION_SIZE)
+	align_start = res->start & ~(PA_SECTION_SIZE - 1);
+	align_size = ALIGN(res->start + resource_size(res), PA_SECTION_SIZE)
 		- align_start;
 
 	nid = page_to_nid(pfn_to_page(align_start >> PAGE_SHIFT));
@@ -160,8 +158,8 @@ void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
 	if (!pgmap->ref || !pgmap->kill)
 		return ERR_PTR(-EINVAL);
 
-	align_start = res->start & ~(SECTION_SIZE - 1);
-	align_size = ALIGN(res->start + resource_size(res), SECTION_SIZE)
+	align_start = res->start & ~(PA_SECTION_SIZE - 1);
+	align_size = ALIGN(res->start + resource_size(res), PA_SECTION_SIZE)
 		- align_start;
 	align_end = align_start + align_size - 1;
 
diff --git a/mm/hmm.c b/mm/hmm.c
index 0db8491090b8..a7e7f8e33c5f 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -34,8 +34,6 @@
 #include <linux/mmu_notifier.h>
 #include <linux/memory_hotplug.h>
 
-#define PA_SECTION_SIZE (1UL << PA_SECTION_SHIFT)
-
 #if IS_ENABLED(CONFIG_HMM_MIRROR)
 static const struct mmu_notifier_ops hmm_mmu_notifier_ops;
 

Re: [PATCH v7 02/12] mm/sparsemem: Introduce common definitions for the size and mask of a section

[Oscar Salvador]

On Wed, May 01, 2019 at 10:55:32PM -0700, Dan Williams wrote:
> Up-level the local section size and mask from kernel/memremap.c to
> global definitions.  These will be used by the new sub-section hotplug
> support.
> 
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: Vlastimil Babka <vbabka@suse.cz>
> Cc: Jérôme Glisse <jglisse@redhat.com>
> Cc: Logan Gunthorpe <logang@deltatee.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> ---
>  include/linux/mmzone.h |    2 ++
>  kernel/memremap.c      |   10 ++++------
>  mm/hmm.c               |    2 --
>  3 files changed, 6 insertions(+), 8 deletions(-)
> 
> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> index f0bbd85dc19a..6726fc175b51 100644
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -1134,6 +1134,8 @@ static inline unsigned long early_pfn_to_nid(unsigned long pfn)
>   * PFN_SECTION_SHIFT		pfn to/from section number
>   */
>  #define PA_SECTION_SHIFT	(SECTION_SIZE_BITS)
> +#define PA_SECTION_SIZE		(1UL << PA_SECTION_SHIFT)
> +#define PA_SECTION_MASK		(~(PA_SECTION_SIZE-1))

As discussed here [1], we do not need the new PA_SECTION_MASK if we work with
pfns/pages directly, so I'd drop it if you go that way.

Besides that:

Reviewed-by: Oscar Salvador <osalvador@suse.de>

[1] https://patchwork.kernel.org/patch/10926047/

-- 
Oscar Salvador
SUSE L3

[PATCH v7 03/12] mm/sparsemem: Add helpers track active portions of a section at boot

[Dan Williams]

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>
Tested-by: Jane Chu <jane.chu@oracle.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 61c2b54a5b61..a68735c79609 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -7291,10 +7291,12 @@ 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..8d4f28e2c25e 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);
+		ms->usage->map_active |= mask;
+		pr_debug("%s: sec: %d mask: %#018lx\n", __func__, i, ms->usage->map_active);
+
+		pfn += pfns;
+		nr_pages -= pfns;
+	}
+}
+
 /* Record a memory area against a node. */
 void __init memory_present(int nid, unsigned long start, unsigned long end)
 {

Re: [PATCH v7 03/12] mm/sparsemem: Add helpers track active portions of a section at boot

[Oscar Salvador]

On Wed, May 01, 2019 at 10:55:37PM -0700, Dan Williams wrote:
> 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>
> Tested-by: Jane Chu <jane.chu@oracle.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Unfortunately I did not hear back about the comments/questions I made for this
in the previous version.

> ---
>  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));

section_active_mask() also converts the value to address/size.
Why do we need to convert the values and we cannot work with pfn/pages instead?
It should be perfectly possible unless I am missing something.

The only thing required would be to export earlier your:

+#define PAGES_PER_SUB_SECTION (SECTION_ACTIVE_SIZE / PAGE_SIZE)
+#define PAGE_SUB_SECTION_MASK (~(PAGES_PER_SUB_SECTION-1))

and change section_active_index to:

static inline int section_active_index(unsigned long pfn)
{
	return (pfn & ~(PAGE_SECTION_MASK)) / SUB_SECTION_ACTIVE_PAGES;
}

In this way we do need to shift the values every time and we can work with them
directly.
Maybe you made it work this way because a reason I am missing.

> +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)));

It seems to me that we already picked the lowest value back in
section_active_init, so we should be fine if we drop the min() here?

Another thing is why do we need to convert the values to address/size, and we
cannot work with pfns/pages.
Unless I am missing something it should be possible.

> +	size = ALIGN(size, SECTION_ACTIVE_SIZE);
> +
> +	idx_start = section_active_index(start);
> +	idx_size = section_active_index(size);
> +
> +	if (idx_size == 0)
> +		return -1;

Maybe we would be better off converting that -1 into something like "FULL_SECTION",
or at least dropping a comment there that "-1" means that the section is fully
populated.

> +	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);
> +		ms->usage->map_active |= mask;
> +		pr_debug("%s: sec: %d mask: %#018lx\n", __func__, i, ms->usage->map_active);
> +
> +		pfn += pfns;
> +		nr_pages -= pfns;
> +	}
> +}
> +
>  /* Record a memory area against a node. */
>  void __init memory_present(int nid, unsigned long start, unsigned long end)
>  {
> 

-- 
Oscar Salvador
SUSE L3

Re: [PATCH v7 03/12] mm/sparsemem: Add helpers track active portions of a section at boot

[Dan Williams]

On Thu, May 2, 2019 at 12:48 AM Oscar Salvador <osalvador@suse.de> wrote:
>
> On Wed, May 01, 2019 at 10:55:37PM -0700, Dan Williams wrote:
> > 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>
> > Tested-by: Jane Chu <jane.chu@oracle.com>
> > Signed-off-by: Dan Williams <dan.j.williams@intel.com>
>
> Unfortunately I did not hear back about the comments/questions I made for this
> in the previous version.

Apologies, yes, will incorporate.

>
> > ---
> >  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));
>
> section_active_mask() also converts the value to address/size.
> Why do we need to convert the values and we cannot work with pfn/pages instead?
> It should be perfectly possible unless I am missing something.
>
> The only thing required would be to export earlier your:
>
> +#define PAGES_PER_SUB_SECTION (SECTION_ACTIVE_SIZE / PAGE_SIZE)
> +#define PAGE_SUB_SECTION_MASK (~(PAGES_PER_SUB_SECTION-1))
>
> and change section_active_index to:
>
> static inline int section_active_index(unsigned long pfn)
> {
>         return (pfn & ~(PAGE_SECTION_MASK)) / SUB_SECTION_ACTIVE_PAGES;
> }
>
> In this way we do need to shift the values every time and we can work with them
> directly.
> Maybe you made it work this way because a reason I am missing.
>
> > +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)));
>
> It seems to me that we already picked the lowest value back in
> section_active_init, so we should be fine if we drop the min() here?
>
> Another thing is why do we need to convert the values to address/size, and we
> cannot work with pfns/pages.
> Unless I am missing something it should be possible.

Right, I believe the physical address conversion was a holdover from a
previous version and these helpers can be cleaned up to be pfn based,
good catch.

>
> > +     size = ALIGN(size, SECTION_ACTIVE_SIZE);
> > +
> > +     idx_start = section_active_index(start);
> > +     idx_size = section_active_index(size);
> > +
> > +     if (idx_size == 0)
> > +             return -1;
>
> Maybe we would be better off converting that -1 into something like "FULL_SECTION",
> or at least dropping a comment there that "-1" means that the section is fully
> populated.

Agreed, I'll add a #define.

Thanks Oscar.

Re: [PATCH v7 03/12] mm/sparsemem: Add helpers track active portions of a section at boot

[Oscar Salvador]

On Thu, May 02, 2019 at 07:03:45AM -0700, Dan Williams wrote:
> > section_active_mask() also converts the value to address/size.
> > Why do we need to convert the values and we cannot work with pfn/pages instead?
> > It should be perfectly possible unless I am missing something.
> >
> > The only thing required would be to export earlier your:
> >
> > +#define PAGES_PER_SUB_SECTION (SECTION_ACTIVE_SIZE / PAGE_SIZE)
> > +#define PAGE_SUB_SECTION_MASK (~(PAGES_PER_SUB_SECTION-1))
> >
> > and change section_active_index to:
> >
> > static inline int section_active_index(unsigned long pfn)
> > {
> >         return (pfn & ~(PAGE_SECTION_MASK)) / SUB_SECTION_ACTIVE_PAGES;

Sorry, here I meant:

return (pfn & ~(PAGE_SECTION_MASK)) / PAGES_PER_SUB_SECTION;

But I think you got the idea :-)

-- 
Oscar Salvador
SUSE L3

Re: [PATCH v7 03/12] mm/sparsemem: Add helpers track active portions of a section at boot

[Pavel Tatashin]

On 19-05-01 22:55:37, Dan Williams wrote:
> 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>
> Tested-by: Jane Chu <jane.chu@oracle.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Hi Dan,

I have sent comments to the previous version of this patch:
https://lore.kernel.org/lkml/CA+CK2bAfnCVYz956jPTNQ+AqHJs7uY1ZqWfL8fSUFWQOdKxHcg@mail.gmail.com/

I think they still apply to this one.

Thank you,
Pasha

[PATCH v7 04/12] mm/hotplug: Prepare shrink_{zone, pgdat}_span for sub-section removal

[Dan Williams]

Sub-section hotplug support reduces the unit of operation of hotplug
from section-sized-units (PAGES_PER_SECTION) to sub-section-sized units
(PAGES_PER_SUBSECTION). Teach shrink_{zone,pgdat}_span() to consider
PAGES_PER_SUBSECTION boundaries as the points where pfn_valid(), not
valid_section(), can toggle.

Cc: Michal Hocko <mhocko@suse.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Logan Gunthorpe <logang@deltatee.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 include/linux/mmzone.h |    2 ++
 mm/memory_hotplug.c    |   29 ++++++++---------------------
 2 files changed, 10 insertions(+), 21 deletions(-)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index cffde898e345..b13f0cddf75e 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -1164,6 +1164,8 @@ static inline unsigned long section_nr_to_pfn(unsigned long sec)
 
 #define SECTION_ACTIVE_SIZE ((1UL << SECTION_SIZE_BITS) / BITS_PER_LONG)
 #define SECTION_ACTIVE_MASK (~(SECTION_ACTIVE_SIZE - 1))
+#define PAGES_PER_SUB_SECTION (SECTION_ACTIVE_SIZE / PAGE_SIZE)
+#define PAGE_SUB_SECTION_MASK (~(PAGES_PER_SUB_SECTION-1))
 
 struct mem_section_usage {
 	/*
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index a76fc6a6e9fe..0d379da0f1a8 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -325,12 +325,8 @@ static unsigned long find_smallest_section_pfn(int nid, struct zone *zone,
 				     unsigned long start_pfn,
 				     unsigned long end_pfn)
 {
-	struct mem_section *ms;
-
-	for (; start_pfn < end_pfn; start_pfn += PAGES_PER_SECTION) {
-		ms = __pfn_to_section(start_pfn);
-
-		if (unlikely(!valid_section(ms)))
+	for (; start_pfn < end_pfn; start_pfn += PAGES_PER_SUB_SECTION) {
+		if (unlikely(!pfn_valid(start_pfn)))
 			continue;
 
 		if (unlikely(pfn_to_nid(start_pfn) != nid))
@@ -350,15 +346,12 @@ static unsigned long find_biggest_section_pfn(int nid, struct zone *zone,
 				    unsigned long start_pfn,
 				    unsigned long end_pfn)
 {
-	struct mem_section *ms;
 	unsigned long pfn;
 
 	/* pfn is the end pfn of a memory section. */
 	pfn = end_pfn - 1;
-	for (; pfn >= start_pfn; pfn -= PAGES_PER_SECTION) {
-		ms = __pfn_to_section(pfn);
-
-		if (unlikely(!valid_section(ms)))
+	for (; pfn >= start_pfn; pfn -= PAGES_PER_SUB_SECTION) {
+		if (unlikely(!pfn_valid(pfn)))
 			continue;
 
 		if (unlikely(pfn_to_nid(pfn) != nid))
@@ -380,7 +373,6 @@ static void shrink_zone_span(struct zone *zone, unsigned long start_pfn,
 	unsigned long z = zone_end_pfn(zone); /* zone_end_pfn namespace clash */
 	unsigned long zone_end_pfn = z;
 	unsigned long pfn;
-	struct mem_section *ms;
 	int nid = zone_to_nid(zone);
 
 	zone_span_writelock(zone);
@@ -417,10 +409,8 @@ static void shrink_zone_span(struct zone *zone, unsigned long start_pfn,
 	 * it check the zone has only hole or not.
 	 */
 	pfn = zone_start_pfn;
-	for (; pfn < zone_end_pfn; pfn += PAGES_PER_SECTION) {
-		ms = __pfn_to_section(pfn);
-
-		if (unlikely(!valid_section(ms)))
+	for (; pfn < zone_end_pfn; pfn += PAGES_PER_SUB_SECTION) {
+		if (unlikely(!pfn_valid(pfn)))
 			continue;
 
 		if (page_zone(pfn_to_page(pfn)) != zone)
@@ -448,7 +438,6 @@ static void shrink_pgdat_span(struct pglist_data *pgdat,
 	unsigned long p = pgdat_end_pfn(pgdat); /* pgdat_end_pfn namespace clash */
 	unsigned long pgdat_end_pfn = p;
 	unsigned long pfn;
-	struct mem_section *ms;
 	int nid = pgdat->node_id;
 
 	if (pgdat_start_pfn == start_pfn) {
@@ -485,10 +474,8 @@ static void shrink_pgdat_span(struct pglist_data *pgdat,
 	 * has only hole or not.
 	 */
 	pfn = pgdat_start_pfn;
-	for (; pfn < pgdat_end_pfn; pfn += PAGES_PER_SECTION) {
-		ms = __pfn_to_section(pfn);
-
-		if (unlikely(!valid_section(ms)))
+	for (; pfn < pgdat_end_pfn; pfn += PAGES_PER_SUB_SECTION) {
+		if (unlikely(!pfn_valid(pfn)))
 			continue;
 
 		if (pfn_to_nid(pfn) != nid)

[PATCH v7 05/12] mm/sparsemem: Convert kmalloc_section_memmap() to populate_section_memmap()

[Dan Williams]

Allow sub-section sized ranges to be added to the memmap.
populate_section_memmap() takes an explict pfn range rather than
assuming a full section, and those parameters are plumbed all the way
through to vmmemap_populate(). There should be no sub-section usage in
current deployments. New warnings are added to clarify which memmap
allocation paths are sub-section capable.

Cc: Michal Hocko <mhocko@suse.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 arch/x86/mm/init_64.c |    4 ++-
 include/linux/mm.h    |    4 ++-
 mm/sparse-vmemmap.c   |   21 +++++++++++------
 mm/sparse.c           |   61 +++++++++++++++++++++++++++++++------------------
 4 files changed, 57 insertions(+), 33 deletions(-)

diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 20d14254b686..bb018d09d2dc 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -1457,7 +1457,9 @@ int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node,
 {
 	int err;
 
-	if (boot_cpu_has(X86_FEATURE_PSE))
+	if (end - start < PAGES_PER_SECTION * sizeof(struct page))
+		err = vmemmap_populate_basepages(start, end, node);
+	else if (boot_cpu_has(X86_FEATURE_PSE))
 		err = vmemmap_populate_hugepages(start, end, node, altmap);
 	else if (altmap) {
 		pr_err_once("%s: no cpu support for altmap allocations\n",
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 0e8834ac32b7..5360a0e4051d 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2748,8 +2748,8 @@ const char * arch_vma_name(struct vm_area_struct *vma);
 void print_vma_addr(char *prefix, unsigned long rip);
 
 void *sparse_buffer_alloc(unsigned long size);
-struct page *sparse_mem_map_populate(unsigned long pnum, int nid,
-		struct vmem_altmap *altmap);
+struct page * __populate_section_memmap(unsigned long pfn,
+		unsigned long nr_pages, int nid, struct vmem_altmap *altmap);
 pgd_t *vmemmap_pgd_populate(unsigned long addr, int node);
 p4d_t *vmemmap_p4d_populate(pgd_t *pgd, unsigned long addr, int node);
 pud_t *vmemmap_pud_populate(p4d_t *p4d, unsigned long addr, int node);
diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
index 7fec05796796..dcb023aa23d1 100644
--- a/mm/sparse-vmemmap.c
+++ b/mm/sparse-vmemmap.c
@@ -245,19 +245,26 @@ int __meminit vmemmap_populate_basepages(unsigned long start,
 	return 0;
 }
 
-struct page * __meminit sparse_mem_map_populate(unsigned long pnum, int nid,
-		struct vmem_altmap *altmap)
+struct page * __meminit __populate_section_memmap(unsigned long pfn,
+		unsigned long nr_pages, int nid, struct vmem_altmap *altmap)
 {
 	unsigned long start;
 	unsigned long end;
-	struct page *map;
 
-	map = pfn_to_page(pnum * PAGES_PER_SECTION);
-	start = (unsigned long)map;
-	end = (unsigned long)(map + PAGES_PER_SECTION);
+	/*
+	 * The minimum granularity of memmap extensions is
+	 * SECTION_ACTIVE_SIZE as allocations are tracked in the
+	 * 'map_active' bitmap of the section.
+	 */
+	end = ALIGN(pfn + nr_pages, PHYS_PFN(SECTION_ACTIVE_SIZE));
+	pfn &= PHYS_PFN(SECTION_ACTIVE_MASK);
+	nr_pages = end - pfn;
+
+	start = (unsigned long) pfn_to_page(pfn);
+	end = start + nr_pages * sizeof(struct page);
 
 	if (vmemmap_populate(start, end, nid, altmap))
 		return NULL;
 
-	return map;
+	return pfn_to_page(pfn);
 }
diff --git a/mm/sparse.c b/mm/sparse.c
index 8d4f28e2c25e..ed26761327bf 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -452,8 +452,8 @@ static unsigned long __init section_map_size(void)
 	return PAGE_ALIGN(sizeof(struct page) * PAGES_PER_SECTION);
 }
 
-struct page __init *sparse_mem_map_populate(unsigned long pnum, int nid,
-		struct vmem_altmap *altmap)
+struct page __init *__populate_section_memmap(unsigned long pfn,
+		unsigned long nr_pages, int nid, struct vmem_altmap *altmap)
 {
 	unsigned long size = section_map_size();
 	struct page *map = sparse_buffer_alloc(size);
@@ -534,10 +534,13 @@ static void __init sparse_init_nid(int nid, unsigned long pnum_begin,
 	}
 	sparse_buffer_init(map_count * section_map_size(), nid);
 	for_each_present_section_nr(pnum_begin, pnum) {
+		unsigned long pfn = section_nr_to_pfn(pnum);
+
 		if (pnum >= pnum_end)
 			break;
 
-		map = sparse_mem_map_populate(pnum, nid, NULL);
+		map = __populate_section_memmap(pfn, PAGES_PER_SECTION,
+				nid, NULL);
 		if (!map) {
 			pr_err("%s: node[%d] memory map backing failed. Some memory will not be available.",
 			       __func__, nid);
@@ -637,17 +640,17 @@ void offline_mem_sections(unsigned long start_pfn, unsigned long end_pfn)
 #endif
 
 #ifdef CONFIG_SPARSEMEM_VMEMMAP
-static inline struct page *kmalloc_section_memmap(unsigned long pnum, int nid,
-		struct vmem_altmap *altmap)
+static struct page *populate_section_memmap(unsigned long pfn,
+		unsigned long nr_pages, int nid, struct vmem_altmap *altmap)
 {
-	/* This will make the necessary allocations eventually. */
-	return sparse_mem_map_populate(pnum, nid, altmap);
+	return __populate_section_memmap(pfn, nr_pages, nid, altmap);
 }
-static void __kfree_section_memmap(struct page *memmap,
+
+static void depopulate_section_memmap(unsigned long pfn, unsigned long nr_pages,
 		struct vmem_altmap *altmap)
 {
-	unsigned long start = (unsigned long)memmap;
-	unsigned long end = (unsigned long)(memmap + PAGES_PER_SECTION);
+	unsigned long start = (unsigned long) pfn_to_page(pfn);
+	unsigned long end = start + nr_pages * sizeof(struct page);
 
 	vmemmap_free(start, end, altmap);
 }
@@ -661,11 +664,18 @@ static void free_map_bootmem(struct page *memmap)
 }
 #endif /* CONFIG_MEMORY_HOTREMOVE */
 #else
-static struct page *__kmalloc_section_memmap(void)
+struct page *populate_section_memmap(unsigned long pfn,
+		unsigned long nr_pages, int nid, struct vmem_altmap *altmap)
 {
 	struct page *page, *ret;
 	unsigned long memmap_size = sizeof(struct page) * PAGES_PER_SECTION;
 
+	if ((pfn & ~PAGE_SECTION_MASK) || nr_pages != PAGES_PER_SECTION) {
+		WARN(1, "%s: called with section unaligned parameters\n",
+				__func__);
+		return NULL;
+	}
+
 	page = alloc_pages(GFP_KERNEL|__GFP_NOWARN, get_order(memmap_size));
 	if (page)
 		goto got_map_page;
@@ -682,15 +692,17 @@ static struct page *__kmalloc_section_memmap(void)
 	return ret;
 }
 
-static inline struct page *kmalloc_section_memmap(unsigned long pnum, int nid,
+static void depopulate_section_memmap(unsigned long pfn, unsigned long nr_pages,
 		struct vmem_altmap *altmap)
 {
-	return __kmalloc_section_memmap();
-}
+	struct page *memmap = pfn_to_page(pfn);
+
+	if ((pfn & ~PAGE_SECTION_MASK) || nr_pages != PAGES_PER_SECTION) {
+		WARN(1, "%s: called with section unaligned parameters\n",
+				__func__);
+		return;
+	}
 
-static void __kfree_section_memmap(struct page *memmap,
-		struct vmem_altmap *altmap)
-{
 	if (is_vmalloc_addr(memmap))
 		vfree(memmap);
 	else
@@ -761,12 +773,13 @@ int __meminit sparse_add_one_section(int nid, unsigned long start_pfn,
 	if (ret < 0 && ret != -EEXIST)
 		return ret;
 	ret = 0;
-	memmap = kmalloc_section_memmap(section_nr, nid, altmap);
+	memmap = populate_section_memmap(start_pfn, PAGES_PER_SECTION, nid,
+			altmap);
 	if (!memmap)
 		return -ENOMEM;
 	usage = kzalloc(mem_section_usage_size(), GFP_KERNEL);
 	if (!usage) {
-		__kfree_section_memmap(memmap, altmap);
+		depopulate_section_memmap(start_pfn, PAGES_PER_SECTION, altmap);
 		return -ENOMEM;
 	}
 
@@ -788,7 +801,7 @@ int __meminit sparse_add_one_section(int nid, unsigned long start_pfn,
 out:
 	if (ret < 0) {
 		kfree(usage);
-		__kfree_section_memmap(memmap, altmap);
+		depopulate_section_memmap(start_pfn, PAGES_PER_SECTION, altmap);
 	}
 	return ret;
 }
@@ -825,7 +838,8 @@ static inline void clear_hwpoisoned_pages(struct page *memmap, int nr_pages)
 #endif
 
 static void free_section_usage(struct page *memmap,
-		struct mem_section_usage *usage, struct vmem_altmap *altmap)
+		struct mem_section_usage *usage, unsigned long pfn,
+		unsigned long nr_pages, struct vmem_altmap *altmap)
 {
 	struct page *usage_page;
 
@@ -839,7 +853,7 @@ static void free_section_usage(struct page *memmap,
 	if (PageSlab(usage_page) || PageCompound(usage_page)) {
 		kfree(usage);
 		if (memmap)
-			__kfree_section_memmap(memmap, altmap);
+			depopulate_section_memmap(pfn, nr_pages, altmap);
 		return;
 	}
 
@@ -868,7 +882,8 @@ void sparse_remove_one_section(struct zone *zone, struct mem_section *ms,
 
 	clear_hwpoisoned_pages(memmap + map_offset,
 			PAGES_PER_SECTION - map_offset);
-	free_section_usage(memmap, usage, altmap);
+	free_section_usage(memmap, usage, section_nr_to_pfn(__section_nr(ms)),
+			PAGES_PER_SECTION, altmap);
 }
 #endif /* CONFIG_MEMORY_HOTREMOVE */
 #endif /* CONFIG_MEMORY_HOTPLUG */

Re: [PATCH v7 05/12] mm/sparsemem: Convert kmalloc_section_memmap() to populate_section_memmap()

[Oscar Salvador]

On Wed, May 01, 2019 at 10:55:48PM -0700, Dan Williams wrote:
> Allow sub-section sized ranges to be added to the memmap.
> populate_section_memmap() takes an explict pfn range rather than
> assuming a full section, and those parameters are plumbed all the way
> through to vmmemap_populate(). There should be no sub-section usage in
> current deployments. New warnings are added to clarify which memmap
> allocation paths are sub-section capable.
> 
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: David Hildenbrand <david@redhat.com>
> Cc: Logan Gunthorpe <logang@deltatee.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> ---
>  arch/x86/mm/init_64.c |    4 ++-
>  include/linux/mm.h    |    4 ++-
>  mm/sparse-vmemmap.c   |   21 +++++++++++------
>  mm/sparse.c           |   61 +++++++++++++++++++++++++++++++------------------
>  4 files changed, 57 insertions(+), 33 deletions(-)
> 
> diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
> index 20d14254b686..bb018d09d2dc 100644
> --- a/arch/x86/mm/init_64.c
> +++ b/arch/x86/mm/init_64.c
> @@ -1457,7 +1457,9 @@ int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node,
>  {
>  	int err;
>  
> -	if (boot_cpu_has(X86_FEATURE_PSE))
> +	if (end - start < PAGES_PER_SECTION * sizeof(struct page))
maybe just:

	if (PHYS_PFN(end) - PHYS_PFN(start) < PAGES_PER_SECTION) ?
> +		err = vmemmap_populate_basepages(start, end, node);
> +	else if (boot_cpu_has(X86_FEATURE_PSE))
>  		err = vmemmap_populate_hugepages(start, end, node, altmap);
>  	else if (altmap) {
>  		pr_err_once("%s: no cpu support for altmap allocations\n",

Although the following looks more clear to me:

int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node,
                struct vmem_altmap *altmap)
{
        int err;
        bool partial_section = (PHYS_PFN(end) - PFN_PHYS(start)) < PAGES_PER_SECTION;

        if (partial_section || !boot_cpu_has(X86_FEATURE_PSE))
                err = vmemmap_populate_basepages(start, end, node);
        else if (boot_cpu_has(X86_FEATURE_PSE))
                err = vmemmap_populate_hugepages(start, end, node, altmap);
        else if (altmap) {
                pr_err_once("%s: no cpu support for altmap allocations\n",
                                __func__);
                err = -ENOMEM;
        }

        if (!err)
                sync_global_pgds(start, end - 1);
        return err;
}

> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 0e8834ac32b7..5360a0e4051d 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -2748,8 +2748,8 @@ const char * arch_vma_name(struct vm_area_struct *vma);
>  void print_vma_addr(char *prefix, unsigned long rip);
>  
>  void *sparse_buffer_alloc(unsigned long size);
> -struct page *sparse_mem_map_populate(unsigned long pnum, int nid,
> -		struct vmem_altmap *altmap);
> +struct page * __populate_section_memmap(unsigned long pfn,
> +		unsigned long nr_pages, int nid, struct vmem_altmap *altmap);
>  pgd_t *vmemmap_pgd_populate(unsigned long addr, int node);
>  p4d_t *vmemmap_p4d_populate(pgd_t *pgd, unsigned long addr, int node);
>  pud_t *vmemmap_pud_populate(p4d_t *p4d, unsigned long addr, int node);
> diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
> index 7fec05796796..dcb023aa23d1 100644
> --- a/mm/sparse-vmemmap.c
> +++ b/mm/sparse-vmemmap.c
> @@ -245,19 +245,26 @@ int __meminit vmemmap_populate_basepages(unsigned long start,
>  	return 0;
>  }
>  
> -struct page * __meminit sparse_mem_map_populate(unsigned long pnum, int nid,
> -		struct vmem_altmap *altmap)
> +struct page * __meminit __populate_section_memmap(unsigned long pfn,
> +		unsigned long nr_pages, int nid, struct vmem_altmap *altmap)
>  {
>  	unsigned long start;
>  	unsigned long end;
> -	struct page *map;
>  
> -	map = pfn_to_page(pnum * PAGES_PER_SECTION);
> -	start = (unsigned long)map;
> -	end = (unsigned long)(map + PAGES_PER_SECTION);
> +	/*
> +	 * The minimum granularity of memmap extensions is
> +	 * SECTION_ACTIVE_SIZE as allocations are tracked in the
> +	 * 'map_active' bitmap of the section.
> +	 */
> +	end = ALIGN(pfn + nr_pages, PHYS_PFN(SECTION_ACTIVE_SIZE));

I would use PAGES_PER_SUB_SECTION directly:

	 end = ALIGN(pfn + nr_pages, PAGES_PER_SUB_SECTION);

> +	pfn &= PHYS_PFN(SECTION_ACTIVE_MASK);

	pfn &= PAGE_SUB_SECTION_MASK ?

[...]
> -static struct page *__kmalloc_section_memmap(void)
> +struct page *populate_section_memmap(unsigned long pfn,
> +		unsigned long nr_pages, int nid, struct vmem_altmap *altmap)
>  {
>  	struct page *page, *ret;
>  	unsigned long memmap_size = sizeof(struct page) * PAGES_PER_SECTION;
>  
> +	if ((pfn & ~PAGE_SECTION_MASK) || nr_pages != PAGES_PER_SECTION) {
> +		WARN(1, "%s: called with section unaligned parameters\n",
> +				__func__);
> +		return NULL;
> +	}

Can this actually happen? We need CONFIG_SPARSEMEM_VMEMMAP in order to use nvdimm,
right?

But I guess it is fine to have a safety net just in case.

> +
>  	page = alloc_pages(GFP_KERNEL|__GFP_NOWARN, get_order(memmap_size));
>  	if (page)
>  		goto got_map_page;
> @@ -682,15 +692,17 @@ static struct page *__kmalloc_section_memmap(void)
>  	return ret;
>  }
>  
> -static inline struct page *kmalloc_section_memmap(unsigned long pnum, int nid,
> +static void depopulate_section_memmap(unsigned long pfn, unsigned long nr_pages,
>  		struct vmem_altmap *altmap)
>  {
> -	return __kmalloc_section_memmap();
> -}
> +	struct page *memmap = pfn_to_page(pfn);
> +
> +	if ((pfn & ~PAGE_SECTION_MASK) || nr_pages != PAGES_PER_SECTION) {
> +		WARN(1, "%s: called with section unaligned parameters\n",
> +				__func__);
> +		return;
> +	}
>  
> -static void __kfree_section_memmap(struct page *memmap,
> -		struct vmem_altmap *altmap)
> -{
>  	if (is_vmalloc_addr(memmap))
>  		vfree(memmap);
>  	else
> @@ -761,12 +773,13 @@ int __meminit sparse_add_one_section(int nid, unsigned long start_pfn,
>  	if (ret < 0 && ret != -EEXIST)
>  		return ret;
>  	ret = 0;
> -	memmap = kmalloc_section_memmap(section_nr, nid, altmap);
> +	memmap = populate_section_memmap(start_pfn, PAGES_PER_SECTION, nid,
> +			altmap);
>  	if (!memmap)
>  		return -ENOMEM;
>  	usage = kzalloc(mem_section_usage_size(), GFP_KERNEL);
>  	if (!usage) {
> -		__kfree_section_memmap(memmap, altmap);
> +		depopulate_section_memmap(start_pfn, PAGES_PER_SECTION, altmap);
>  		return -ENOMEM;
>  	}
>  
> @@ -788,7 +801,7 @@ int __meminit sparse_add_one_section(int nid, unsigned long start_pfn,
>  out:
>  	if (ret < 0) {
>  		kfree(usage);
> -		__kfree_section_memmap(memmap, altmap);
> +		depopulate_section_memmap(start_pfn, PAGES_PER_SECTION, altmap);
>  	}
>  	return ret;
>  }
> @@ -825,7 +838,8 @@ static inline void clear_hwpoisoned_pages(struct page *memmap, int nr_pages)
>  #endif
>  
>  static void free_section_usage(struct page *memmap,
> -		struct mem_section_usage *usage, struct vmem_altmap *altmap)
> +		struct mem_section_usage *usage, unsigned long pfn,
> +		unsigned long nr_pages, struct vmem_altmap *altmap)
>  {
>  	struct page *usage_page;
>  
> @@ -839,7 +853,7 @@ static void free_section_usage(struct page *memmap,
>  	if (PageSlab(usage_page) || PageCompound(usage_page)) {
>  		kfree(usage);
>  		if (memmap)
> -			__kfree_section_memmap(memmap, altmap);
> +			depopulate_section_memmap(pfn, nr_pages, altmap);
>  		return;
>  	}
>  
> @@ -868,7 +882,8 @@ void sparse_remove_one_section(struct zone *zone, struct mem_section *ms,
>  
>  	clear_hwpoisoned_pages(memmap + map_offset,
>  			PAGES_PER_SECTION - map_offset);
> -	free_section_usage(memmap, usage, altmap);
> +	free_section_usage(memmap, usage, section_nr_to_pfn(__section_nr(ms)),
> +			PAGES_PER_SECTION, altmap);
>  }
>  #endif /* CONFIG_MEMORY_HOTREMOVE */
>  #endif /* CONFIG_MEMORY_HOTPLUG */
> 

-- 
Oscar Salvador
SUSE L3

[PATCH v7 06/12] mm/hotplug: Kill is_dev_zone() usage in __remove_pages()

[Dan Williams]

The zone type check was a leftover from the cleanup that plumbed altmap
through the memory hotplug path, i.e. commit da024512a1fa "mm: pass the
vmem_altmap to arch_remove_memory and __remove_pages".

Cc: Michal Hocko <mhocko@suse.com>
Cc: Logan Gunthorpe <logang@deltatee.com>
Cc: David Hildenbrand <david@redhat.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 mm/memory_hotplug.c |    7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 0d379da0f1a8..108380e20d8f 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -544,11 +544,8 @@ void __remove_pages(struct zone *zone, unsigned long phys_start_pfn,
 	unsigned long map_offset = 0;
 	int sections_to_remove;
 
-	/* In the ZONE_DEVICE case device driver owns the memory region */
-	if (is_dev_zone(zone)) {
-		if (altmap)
-			map_offset = vmem_altmap_offset(altmap);
-	}
+	if (altmap)
+		map_offset = vmem_altmap_offset(altmap);
 
 	clear_zone_contiguous(zone);
 

Re: [PATCH v7 06/12] mm/hotplug: Kill is_dev_zone() usage in __remove_pages()

[David Hildenbrand]

On 02.05.19 07:55, Dan Williams wrote:
> The zone type check was a leftover from the cleanup that plumbed altmap
> through the memory hotplug path, i.e. commit da024512a1fa "mm: pass the
> vmem_altmap to arch_remove_memory and __remove_pages".
> 
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: Logan Gunthorpe <logang@deltatee.com>
> Cc: David Hildenbrand <david@redhat.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> ---
>  mm/memory_hotplug.c |    7 ++-----
>  1 file changed, 2 insertions(+), 5 deletions(-)
> 
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 0d379da0f1a8..108380e20d8f 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -544,11 +544,8 @@ void __remove_pages(struct zone *zone, unsigned long phys_start_pfn,
>  	unsigned long map_offset = 0;
>  	int sections_to_remove;
>  
> -	/* In the ZONE_DEVICE case device driver owns the memory region */
> -	if (is_dev_zone(zone)) {
> -		if (altmap)
> -			map_offset = vmem_altmap_offset(altmap);
> -	}
> +	if (altmap)
> +		map_offset = vmem_altmap_offset(altmap);
>  
>  	clear_zone_contiguous(zone);
>  
> 


That can be picked up independently

Reviewed-by: David Hildenbrand <david@redhat.com>

-- 

Thanks,

David / dhildenb

Re: [PATCH v7 06/12] mm/hotplug: Kill is_dev_zone() usage in __remove_pages()

[Oscar Salvador]

On Wed, May 01, 2019 at 10:55:53PM -0700, Dan Williams wrote:
> The zone type check was a leftover from the cleanup that plumbed altmap
> through the memory hotplug path, i.e. commit da024512a1fa "mm: pass the
> vmem_altmap to arch_remove_memory and __remove_pages".
> 
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: Logan Gunthorpe <logang@deltatee.com>
> Cc: David Hildenbrand <david@redhat.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Reviewed-by: Oscar Salvador <osalvador@suse.de>

-- 
Oscar Salvador
SUSE L3

[PATCH v7 07/12] mm: Kill is_dev_zone() helper

[Dan Williams]

Given there are no more usages of is_dev_zone() outside of 'ifdef
CONFIG_ZONE_DEVICE' protection, kill off the compilation helper.

Cc: Michal Hocko <mhocko@suse.com>
Cc: Logan Gunthorpe <logang@deltatee.com>
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 include/linux/mmzone.h |   12 ------------
 mm/page_alloc.c        |    2 +-
 2 files changed, 1 insertion(+), 13 deletions(-)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index b13f0cddf75e..3237c5e456df 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -855,18 +855,6 @@ static inline int local_memory_node(int node_id) { return node_id; };
  */
 #define zone_idx(zone)		((zone) - (zone)->zone_pgdat->node_zones)
 
-#ifdef CONFIG_ZONE_DEVICE
-static inline bool is_dev_zone(const struct zone *zone)
-{
-	return zone_idx(zone) == ZONE_DEVICE;
-}
-#else
-static inline bool is_dev_zone(const struct zone *zone)
-{
-	return false;
-}
-#endif
-
 /*
  * Returns true if a zone has pages managed by the buddy allocator.
  * All the reclaim decisions have to use this function rather than
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index a68735c79609..be309d6a79de 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5864,7 +5864,7 @@ void __ref memmap_init_zone_device(struct zone *zone,
 	unsigned long start = jiffies;
 	int nid = pgdat->node_id;
 
-	if (WARN_ON_ONCE(!pgmap || !is_dev_zone(zone)))
+	if (WARN_ON_ONCE(!pgmap || zone_idx(zone) != ZONE_DEVICE))
 		return;
 
 	/*

[PATCH v7 08/12] mm/sparsemem: Prepare for sub-section ranges

[Dan Williams]

Prepare the memory hot-{add,remove} paths for handling sub-section
ranges by plumbing the starting page frame and number of pages being
handled through arch_{add,remove}_memory() to
sparse_{add,remove}_one_section().

This is simply plumbing, small cleanups, and some identifier renames. No
intended functional changes.

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/memory_hotplug.h |    7 +-
 mm/memory_hotplug.c            |  118 +++++++++++++++++++++++++---------------
 mm/sparse.c                    |    7 +-
 3 files changed, 83 insertions(+), 49 deletions(-)

diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index ae892eef8b82..835a94650ee3 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -354,9 +354,10 @@ extern int add_memory_resource(int nid, struct resource *resource);
 extern void move_pfn_range_to_zone(struct zone *zone, unsigned long start_pfn,
 		unsigned long nr_pages, struct vmem_altmap *altmap);
 extern bool is_memblock_offlined(struct memory_block *mem);
-extern int sparse_add_one_section(int nid, unsigned long start_pfn,
-				  struct vmem_altmap *altmap);
-extern void sparse_remove_one_section(struct zone *zone, struct mem_section *ms,
+extern int sparse_add_section(int nid, unsigned long pfn,
+		unsigned long nr_pages, struct vmem_altmap *altmap);
+extern void sparse_remove_section(struct zone *zone, struct mem_section *ms,
+		unsigned long pfn, unsigned long nr_pages,
 		unsigned long map_offset, struct vmem_altmap *altmap);
 extern struct page *sparse_decode_mem_map(unsigned long coded_mem_map,
 					  unsigned long pnum);
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 108380e20d8f..9f73332af910 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -251,22 +251,44 @@ void __init register_page_bootmem_info_node(struct pglist_data *pgdat)
 }
 #endif /* CONFIG_HAVE_BOOTMEM_INFO_NODE */
 
-static int __meminit __add_section(int nid, unsigned long phys_start_pfn,
-		struct vmem_altmap *altmap, bool want_memblock)
+static int __meminit __add_section(int nid, unsigned long pfn,
+		unsigned long nr_pages,	struct vmem_altmap *altmap,
+		bool want_memblock)
 {
 	int ret;
 
-	if (pfn_valid(phys_start_pfn))
+	if (pfn_valid(pfn))
 		return -EEXIST;
 
-	ret = sparse_add_one_section(nid, phys_start_pfn, altmap);
+	ret = sparse_add_section(nid, pfn, nr_pages, altmap);
 	if (ret < 0)
 		return ret;
 
 	if (!want_memblock)
 		return 0;
 
-	return hotplug_memory_register(nid, __pfn_to_section(phys_start_pfn));
+	return hotplug_memory_register(nid, __pfn_to_section(pfn));
+}
+
+static int subsection_check(unsigned long pfn, unsigned long nr_pages,
+		unsigned long flags, const char *reason)
+{
+	/*
+	 * Only allow partial section hotplug for !memblock ranges,
+	 * since register_new_memory() requires section alignment, and
+	 * CONFIG_SPARSEMEM_VMEMMAP=n requires sections to be fully
+	 * populated.
+	 */
+	if ((!IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP)
+				|| (flags & MHP_MEMBLOCK_API))
+			&& ((pfn & ~PAGE_SECTION_MASK)
+				|| (nr_pages & ~PAGE_SECTION_MASK))) {
+		WARN(1, "Sub-section hot-%s incompatible with %s\n", reason,
+				(flags & MHP_MEMBLOCK_API)
+				? "memblock api" : "!CONFIG_SPARSEMEM_VMEMMAP");
+		return -EINVAL;
+	}
+	return 0;
 }
 
 /*
@@ -275,34 +297,40 @@ static int __meminit __add_section(int nid, unsigned long phys_start_pfn,
  * call this function after deciding the zone to which to
  * add the new pages.
  */
-int __ref __add_pages(int nid, unsigned long phys_start_pfn,
-		unsigned long nr_pages, struct mhp_restrictions *restrictions)
+int __ref __add_pages(int nid, unsigned long pfn, unsigned long nr_pages,
+		struct mhp_restrictions *restrictions)
 {
 	unsigned long i;
-	int err = 0;
-	int start_sec, end_sec;
+	int start_sec, end_sec, err;
 	struct vmem_altmap *altmap = restrictions->altmap;
 
-	/* during initialize mem_map, align hot-added range to section */
-	start_sec = pfn_to_section_nr(phys_start_pfn);
-	end_sec = pfn_to_section_nr(phys_start_pfn + nr_pages - 1);
-
 	if (altmap) {
 		/*
 		 * Validate altmap is within bounds of the total request
 		 */
-		if (altmap->base_pfn != phys_start_pfn
+		if (altmap->base_pfn != pfn
 				|| vmem_altmap_offset(altmap) > nr_pages) {
 			pr_warn_once("memory add fail, invalid altmap\n");
-			err = -EINVAL;
-			goto out;
+			return -EINVAL;
 		}
 		altmap->alloc = 0;
 	}
 
+	err = subsection_check(pfn, nr_pages, restrictions->flags, "add");
+	if (err)
+		return err;
+
+	start_sec = pfn_to_section_nr(pfn);
+	end_sec = pfn_to_section_nr(pfn + nr_pages - 1);
 	for (i = start_sec; i <= end_sec; i++) {
-		err = __add_section(nid, section_nr_to_pfn(i), altmap,
+		unsigned long pfns;
+
+		pfns = min(nr_pages, PAGES_PER_SECTION
+				- (pfn & ~PAGE_SECTION_MASK));
+		err = __add_section(nid, pfn, pfns, altmap,
 				restrictions->flags & MHP_MEMBLOCK_API);
+		pfn += pfns;
+		nr_pages -= pfns;
 
 		/*
 		 * EEXIST is finally dealt with by ioresource collision
@@ -315,7 +343,6 @@ int __ref __add_pages(int nid, unsigned long phys_start_pfn,
 		cond_resched();
 	}
 	vmemmap_populate_print_last();
-out:
 	return err;
 }
 
@@ -494,10 +521,10 @@ static void shrink_pgdat_span(struct pglist_data *pgdat,
 	pgdat->node_spanned_pages = 0;
 }
 
-static void __remove_zone(struct zone *zone, unsigned long start_pfn)
+static void __remove_zone(struct zone *zone, unsigned long start_pfn,
+		unsigned long nr_pages)
 {
 	struct pglist_data *pgdat = zone->zone_pgdat;
-	int nr_pages = PAGES_PER_SECTION;
 	unsigned long flags;
 
 	pgdat_resize_lock(zone->zone_pgdat, &flags);
@@ -506,29 +533,26 @@ static void __remove_zone(struct zone *zone, unsigned long start_pfn)
 	pgdat_resize_unlock(zone->zone_pgdat, &flags);
 }
 
-static void __remove_section(struct zone *zone, struct mem_section *ms,
-			     unsigned long map_offset,
-			     struct vmem_altmap *altmap)
+static void __remove_section(struct zone *zone, unsigned long pfn,
+		unsigned long nr_pages, unsigned long map_offset,
+		struct vmem_altmap *altmap)
 {
-	unsigned long start_pfn;
-	int scn_nr;
+	struct mem_section *ms = __nr_to_section(pfn_to_section_nr(pfn));
 
 	if (WARN_ON_ONCE(!valid_section(ms)))
 		return;
 
 	unregister_memory_section(ms);
 
-	scn_nr = __section_nr(ms);
-	start_pfn = section_nr_to_pfn((unsigned long)scn_nr);
-	__remove_zone(zone, start_pfn);
+	__remove_zone(zone, pfn, nr_pages);
 
-	sparse_remove_one_section(zone, ms, map_offset, altmap);
+	sparse_remove_section(zone, ms, pfn, nr_pages, map_offset, altmap);
 }
 
 /**
  * __remove_pages() - remove sections of pages from a zone
  * @zone: zone from which pages need to be removed
- * @phys_start_pfn: starting pageframe (must be aligned to start of a section)
+ * @pfn: starting pageframe (must be aligned to start of a section)
  * @nr_pages: number of pages to remove (must be multiple of section size)
  * @altmap: alternative device page map or %NULL if default memmap is used
  *
@@ -537,31 +561,39 @@ static void __remove_section(struct zone *zone, struct mem_section *ms,
  * sure that pages are marked reserved and zones are adjust properly by
  * calling offline_pages().
  */
-void __remove_pages(struct zone *zone, unsigned long phys_start_pfn,
+void __remove_pages(struct zone *zone, unsigned long pfn,
 		    unsigned long nr_pages, struct vmem_altmap *altmap)
 {
-	unsigned long i;
 	unsigned long map_offset = 0;
-	int sections_to_remove;
+	int i, start_sec, end_sec;
+	struct memory_block *mem;
+	unsigned long flags = 0;
 
 	if (altmap)
 		map_offset = vmem_altmap_offset(altmap);
 
 	clear_zone_contiguous(zone);
 
-	/*
-	 * We can only remove entire sections
-	 */
-	BUG_ON(phys_start_pfn & ~PAGE_SECTION_MASK);
-	BUG_ON(nr_pages % PAGES_PER_SECTION);
+	mem = find_memory_block(__pfn_to_section(pfn));
+	if (mem) {
+		flags |= MHP_MEMBLOCK_API;
+		put_device(&mem->dev);
+	}
 
-	sections_to_remove = nr_pages / PAGES_PER_SECTION;
-	for (i = 0; i < sections_to_remove; i++) {
-		unsigned long pfn = phys_start_pfn + i*PAGES_PER_SECTION;
+	if (subsection_check(pfn, nr_pages, flags, "remove"))
+		return;
+
+	start_sec = pfn_to_section_nr(pfn);
+	end_sec = pfn_to_section_nr(pfn + nr_pages - 1);
+	for (i = start_sec; i <= end_sec; i++) {
+		unsigned long pfns;
 
 		cond_resched();
-		__remove_section(zone, __pfn_to_section(pfn), map_offset,
-				 altmap);
+		pfns = min(nr_pages, PAGES_PER_SECTION
+				- (pfn & ~PAGE_SECTION_MASK));
+		__remove_section(zone, pfn, pfns, map_offset, altmap);
+		pfn += pfns;
+		nr_pages -= pfns;
 		map_offset = 0;
 	}
 
diff --git a/mm/sparse.c b/mm/sparse.c
index ed26761327bf..198371e5fc87 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -756,8 +756,8 @@ static void free_map_bootmem(struct page *memmap)
  * * -EEXIST	- Section has been present.
  * * -ENOMEM	- Out of memory.
  */
-int __meminit sparse_add_one_section(int nid, unsigned long start_pfn,
-				     struct vmem_altmap *altmap)
+int __meminit sparse_add_section(int nid, unsigned long start_pfn,
+		unsigned long nr_pages, struct vmem_altmap *altmap)
 {
 	unsigned long section_nr = pfn_to_section_nr(start_pfn);
 	struct mem_section_usage *usage;
@@ -866,7 +866,8 @@ static void free_section_usage(struct page *memmap,
 		free_map_bootmem(memmap);
 }
 
-void sparse_remove_one_section(struct zone *zone, struct mem_section *ms,
+void sparse_remove_section(struct zone *zone, struct mem_section *ms,
+		unsigned long pfn, unsigned long nr_pages,
 		unsigned long map_offset, struct vmem_altmap *altmap)
 {
 	struct page *memmap = NULL;

Re: [PATCH v7 08/12] mm/sparsemem: Prepare for sub-section ranges

[Oscar Salvador]

On Wed, May 01, 2019 at 10:56:05PM -0700, Dan Williams wrote:
> Prepare the memory hot-{add,remove} paths for handling sub-section
> ranges by plumbing the starting page frame and number of pages being
> handled through arch_{add,remove}_memory() to
> sparse_{add,remove}_one_section().
> 
> This is simply plumbing, small cleanups, and some identifier renames. No
> intended functional changes.
> 
> 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/memory_hotplug.h |    7 +-
>  mm/memory_hotplug.c            |  118 +++++++++++++++++++++++++---------------
>  mm/sparse.c                    |    7 +-
>  3 files changed, 83 insertions(+), 49 deletions(-)
> 
> diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
> index ae892eef8b82..835a94650ee3 100644
> --- a/include/linux/memory_hotplug.h
> +++ b/include/linux/memory_hotplug.h
> @@ -354,9 +354,10 @@ extern int add_memory_resource(int nid, struct resource *resource);
>  extern void move_pfn_range_to_zone(struct zone *zone, unsigned long start_pfn,
>  		unsigned long nr_pages, struct vmem_altmap *altmap);
>  extern bool is_memblock_offlined(struct memory_block *mem);
> -extern int sparse_add_one_section(int nid, unsigned long start_pfn,
> -				  struct vmem_altmap *altmap);
> -extern void sparse_remove_one_section(struct zone *zone, struct mem_section *ms,
> +extern int sparse_add_section(int nid, unsigned long pfn,
> +		unsigned long nr_pages, struct vmem_altmap *altmap);
> +extern void sparse_remove_section(struct zone *zone, struct mem_section *ms,
> +		unsigned long pfn, unsigned long nr_pages,
>  		unsigned long map_offset, struct vmem_altmap *altmap);
>  extern struct page *sparse_decode_mem_map(unsigned long coded_mem_map,
>  					  unsigned long pnum);
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 108380e20d8f..9f73332af910 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -251,22 +251,44 @@ void __init register_page_bootmem_info_node(struct pglist_data *pgdat)
>  }
>  #endif /* CONFIG_HAVE_BOOTMEM_INFO_NODE */
>  
> -static int __meminit __add_section(int nid, unsigned long phys_start_pfn,
> -		struct vmem_altmap *altmap, bool want_memblock)
> +static int __meminit __add_section(int nid, unsigned long pfn,
> +		unsigned long nr_pages,	struct vmem_altmap *altmap,
> +		bool want_memblock)
>  {
>  	int ret;
>  
> -	if (pfn_valid(phys_start_pfn))
> +	if (pfn_valid(pfn))
>  		return -EEXIST;
>  
> -	ret = sparse_add_one_section(nid, phys_start_pfn, altmap);
> +	ret = sparse_add_section(nid, pfn, nr_pages, altmap);
>  	if (ret < 0)
>  		return ret;
>  
>  	if (!want_memblock)
>  		return 0;
>  
> -	return hotplug_memory_register(nid, __pfn_to_section(phys_start_pfn));
> +	return hotplug_memory_register(nid, __pfn_to_section(pfn));
> +}
> +
> +static int subsection_check(unsigned long pfn, unsigned long nr_pages,
> +		unsigned long flags, const char *reason)
> +{
> +	/*
> +	 * Only allow partial section hotplug for !memblock ranges,
> +	 * since register_new_memory() requires section alignment, and

What is register_new_memory?

Reviewed-by: Oscar Salvador <osalvador@suse.de>

-- 
Oscar Salvador
SUSE L3

[PATCH v7 09/12] mm/sparsemem: Support sub-section hotplug

[Dan Williams]

The libnvdimm sub-system has suffered a series of hacks and broken
workarounds for the memory-hotplug implementation's awkward
section-aligned (128MB) granularity. For example the following backtrace
is emitted when attempting arch_add_memory() with physical address
ranges that intersect 'System RAM' (RAM) with 'Persistent Memory' (PMEM)
within a given section:

 WARNING: CPU: 0 PID: 558 at kernel/memremap.c:300 devm_memremap_pages+0x3b5/0x4c0
 devm_memremap_pages attempted on mixed region [mem 0x200000000-0x2fbffffff flags 0x200]
 [..]
 Call Trace:
   dump_stack+0x86/0xc3
   __warn+0xcb/0xf0
   warn_slowpath_fmt+0x5f/0x80
   devm_memremap_pages+0x3b5/0x4c0
   __wrap_devm_memremap_pages+0x58/0x70 [nfit_test_iomap]
   pmem_attach_disk+0x19a/0x440 [nd_pmem]

Recently it was discovered that the problem goes beyond RAM vs PMEM
collisions as some platform produce PMEM vs PMEM collisions within a
given section. The libnvdimm workaround for that case revealed that the
libnvdimm section-alignment-padding implementation has been broken for a
long while. A fix for that long-standing breakage introduces as many
problems as it solves as it would require a backward-incompatible change
to the namespace metadata interpretation. Instead of that dubious route
[1], address the root problem in the memory-hotplug implementation.

[1]: https://lore.kernel.org/r/155000671719.348031.2347363160141119237.stgit@dwillia2-desk3.amr.corp.intel.com
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>
---
 mm/sparse.c |  223 ++++++++++++++++++++++++++++++++++++++++-------------------
 1 file changed, 150 insertions(+), 73 deletions(-)

diff --git a/mm/sparse.c b/mm/sparse.c
index 198371e5fc87..419a3620af6e 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -83,8 +83,15 @@ static int __meminit sparse_index_init(unsigned long section_nr, int nid)
 	unsigned long root = SECTION_NR_TO_ROOT(section_nr);
 	struct mem_section *section;
 
+	/*
+	 * An existing section is possible in the sub-section hotplug
+	 * case. First hot-add instantiates, follow-on hot-add reuses
+	 * the existing section.
+	 *
+	 * The mem_hotplug_lock resolves the apparent race below.
+	 */
 	if (mem_section[root])
-		return -EEXIST;
+		return 0;
 
 	section = sparse_index_alloc(nid);
 	if (!section)
@@ -338,6 +345,15 @@ static void __meminit sparse_init_one_section(struct mem_section *ms,
 		unsigned long pnum, struct page *mem_map,
 		struct mem_section_usage *usage)
 {
+	/*
+	 * Given that SPARSEMEM_VMEMMAP=y supports sub-section hotplug,
+	 * ->section_mem_map can not be guaranteed to point to a full
+	 *  section's worth of memory.  The field is only valid / used
+	 *  in the SPARSEMEM_VMEMMAP=n case.
+	 */
+	if (IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP))
+		mem_map = NULL;
+
 	ms->section_mem_map &= ~SECTION_MAP_MASK;
 	ms->section_mem_map |= sparse_encode_mem_map(mem_map, pnum) |
 							SECTION_HAS_MEM_MAP;
@@ -743,10 +759,130 @@ static void free_map_bootmem(struct page *memmap)
 #endif /* CONFIG_MEMORY_HOTREMOVE */
 #endif /* CONFIG_SPARSEMEM_VMEMMAP */
 
+#ifndef CONFIG_MEMORY_HOTREMOVE
+static void free_map_bootmem(struct page *memmap)
+{
+}
+#endif
+
+static bool is_early_section(struct mem_section *ms)
+{
+	struct page *usage_page;
+
+	usage_page = virt_to_page(ms->usage);
+	if (PageSlab(usage_page) || PageCompound(usage_page))
+		return false;
+	else
+		return true;
+}
+
+static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
+		int nid, struct vmem_altmap *altmap)
+{
+	unsigned long mask = section_active_mask(pfn, nr_pages);
+	struct mem_section *ms = __pfn_to_section(pfn);
+	bool early_section = is_early_section(ms);
+	struct page *memmap = NULL;
+
+	if (WARN(!ms->usage || (ms->usage->map_active & mask) != mask,
+			"section already deactivated: active: %#lx mask: %#lx\n",
+			ms->usage ? ms->usage->map_active : 0, mask))
+		return;
+
+	if (WARN(!IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP)
+				&& nr_pages < PAGES_PER_SECTION,
+				"partial memory section removal not supported\n"))
+		return;
+
+	/*
+	 * There are 3 cases to handle across two configurations
+	 * (SPARSEMEM_VMEMMAP={y,n}):
+	 *
+	 * 1/ deactivation of a partial hot-added section (only possible
+	 * in the SPARSEMEM_VMEMMAP=y case).
+	 *    a/ section was present at memory init
+	 *    b/ section was hot-added post memory init
+	 * 2/ deactivation of a complete hot-added section
+	 * 3/ deactivation of a complete section from memory init
+	 *
+	 * For 1/, when map_active does not go to zero we will not be
+	 * freeing the usage map, but still need to free the vmemmap
+	 * range.
+	 *
+	 * For 2/ and 3/ the SPARSEMEM_VMEMMAP={y,n} cases are unified
+	 */
+	ms->usage->map_active ^= mask;
+	if (ms->usage->map_active == 0) {
+		unsigned long section_nr = pfn_to_section_nr(pfn);
+
+		if (!early_section) {
+			kfree(ms->usage);
+			ms->usage = NULL;
+		}
+		memmap = sparse_decode_mem_map(ms->section_mem_map, section_nr);
+		ms->section_mem_map = sparse_encode_mem_map(NULL, section_nr);
+	}
+
+	if (early_section && memmap)
+		free_map_bootmem(memmap);
+	else
+		depopulate_section_memmap(pfn, nr_pages, altmap);
+}
+
+static struct page * __meminit section_activate(int nid, unsigned long pfn,
+		unsigned long nr_pages, struct vmem_altmap *altmap)
+{
+	unsigned long mask = section_active_mask(pfn, nr_pages);
+	struct mem_section *ms = __pfn_to_section(pfn);
+	struct mem_section_usage *usage = NULL;
+	struct page *memmap;
+	int rc = 0;
+
+	if (!ms->usage) {
+		usage = kzalloc(mem_section_usage_size(), GFP_KERNEL);
+		if (!usage)
+			return ERR_PTR(-ENOMEM);
+		ms->usage = usage;
+	}
+
+	if (!mask)
+		rc = -EINVAL;
+	else if (mask & ms->usage->map_active)
+		rc = -EEXIST;
+	else
+		ms->usage->map_active |= mask;
+
+	if (rc) {
+		if (usage)
+			ms->usage = NULL;
+		kfree(usage);
+		return ERR_PTR(rc);
+	}
+
+	/*
+	 * The early init code does not consider partially populated
+	 * initial sections, it simply assumes that memory will never be
+	 * referenced.  If we hot-add memory into such a section then we
+	 * do not need to populate the memmap and can simply reuse what
+	 * is already there.
+	 */
+	if (nr_pages < PAGES_PER_SECTION && is_early_section(ms))
+		return pfn_to_page(pfn);
+
+	memmap = populate_section_memmap(pfn, nr_pages, nid, altmap);
+	if (!memmap) {
+		section_deactivate(pfn, nr_pages, nid, altmap);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	return memmap;
+}
+
 /**
- * sparse_add_one_section - add a memory section
+ * sparse_add_section - add a memory section, or populate an existing one
  * @nid: The node to add section on
  * @start_pfn: start pfn of the memory range
+ * @nr_pages: number of pfns to add in the section
  * @altmap: device page map
  *
  * This is only intended for hotplug.
@@ -760,49 +896,31 @@ int __meminit sparse_add_section(int nid, unsigned long start_pfn,
 		unsigned long nr_pages, struct vmem_altmap *altmap)
 {
 	unsigned long section_nr = pfn_to_section_nr(start_pfn);
-	struct mem_section_usage *usage;
 	struct mem_section *ms;
 	struct page *memmap;
 	int ret;
 
-	/*
-	 * no locking for this, because it does its own
-	 * plus, it does a kmalloc
-	 */
 	ret = sparse_index_init(section_nr, nid);
 	if (ret < 0 && ret != -EEXIST)
 		return ret;
-	ret = 0;
-	memmap = populate_section_memmap(start_pfn, PAGES_PER_SECTION, nid,
-			altmap);
-	if (!memmap)
-		return -ENOMEM;
-	usage = kzalloc(mem_section_usage_size(), GFP_KERNEL);
-	if (!usage) {
-		depopulate_section_memmap(start_pfn, PAGES_PER_SECTION, altmap);
-		return -ENOMEM;
-	}
 
-	ms = __pfn_to_section(start_pfn);
-	if (ms->section_mem_map & SECTION_MARKED_PRESENT) {
-		ret = -EEXIST;
-		goto out;
-	}
+	memmap = section_activate(nid, start_pfn, nr_pages, altmap);
+	if (IS_ERR(memmap))
+		return PTR_ERR(memmap);
+	ret = 0;
 
 	/*
 	 * Poison uninitialized struct pages in order to catch invalid flags
 	 * combinations.
 	 */
-	page_init_poison(memmap, sizeof(struct page) * PAGES_PER_SECTION);
+	page_init_poison(pfn_to_page(start_pfn), sizeof(struct page) * nr_pages);
 
+	ms = __pfn_to_section(start_pfn);
 	section_mark_present(ms);
-	sparse_init_one_section(ms, section_nr, memmap, usage);
+	sparse_init_one_section(ms, section_nr, memmap, ms->usage);
 
-out:
-	if (ret < 0) {
-		kfree(usage);
-		depopulate_section_memmap(start_pfn, PAGES_PER_SECTION, altmap);
-	}
+	if (ret < 0)
+		section_deactivate(start_pfn, nr_pages, nid, altmap);
 	return ret;
 }
 
@@ -837,54 +955,13 @@ static inline void clear_hwpoisoned_pages(struct page *memmap, int nr_pages)
 }
 #endif
 
-static void free_section_usage(struct page *memmap,
-		struct mem_section_usage *usage, unsigned long pfn,
-		unsigned long nr_pages, 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)) {
-		kfree(usage);
-		if (memmap)
-			depopulate_section_memmap(pfn, nr_pages, altmap);
-		return;
-	}
-
-	/*
-	 * The usemap came from bootmem. This is packed with other usemaps
-	 * on the section which has pgdat at boot time. Just keep it as is now.
-	 */
-
-	if (memmap)
-		free_map_bootmem(memmap);
-}
-
 void sparse_remove_section(struct zone *zone, struct mem_section *ms,
 		unsigned long pfn, unsigned long nr_pages,
 		unsigned long map_offset, struct vmem_altmap *altmap)
 {
-	struct page *memmap = NULL;
-	struct mem_section_usage *usage = NULL;
-
-	if (ms->section_mem_map) {
-		usage = ms->usage;
-		memmap = sparse_decode_mem_map(ms->section_mem_map,
-						__section_nr(ms));
-		ms->section_mem_map = 0;
-		ms->usage = NULL;
-	}
-
-	clear_hwpoisoned_pages(memmap + map_offset,
-			PAGES_PER_SECTION - map_offset);
-	free_section_usage(memmap, usage, section_nr_to_pfn(__section_nr(ms)),
-			PAGES_PER_SECTION, altmap);
+	clear_hwpoisoned_pages(pfn_to_page(pfn) + map_offset,
+			nr_pages - map_offset);
+	section_deactivate(pfn, nr_pages, zone_to_nid(zone), altmap);
 }
 #endif /* CONFIG_MEMORY_HOTREMOVE */
 #endif /* CONFIG_MEMORY_HOTPLUG */

Re: [PATCH v7 09/12] mm/sparsemem: Support sub-section hotplug

[Oscar Salvador]

On Wed, May 01, 2019 at 10:56:10PM -0700, Dan Williams wrote:
> The libnvdimm sub-system has suffered a series of hacks and broken
> workarounds for the memory-hotplug implementation's awkward
> section-aligned (128MB) granularity. For example the following backtrace
> is emitted when attempting arch_add_memory() with physical address
> ranges that intersect 'System RAM' (RAM) with 'Persistent Memory' (PMEM)
> within a given section:
> 
>  WARNING: CPU: 0 PID: 558 at kernel/memremap.c:300 devm_memremap_pages+0x3b5/0x4c0
>  devm_memremap_pages attempted on mixed region [mem 0x200000000-0x2fbffffff flags 0x200]
>  [..]
>  Call Trace:
>    dump_stack+0x86/0xc3
>    __warn+0xcb/0xf0
>    warn_slowpath_fmt+0x5f/0x80
>    devm_memremap_pages+0x3b5/0x4c0
>    __wrap_devm_memremap_pages+0x58/0x70 [nfit_test_iomap]
>    pmem_attach_disk+0x19a/0x440 [nd_pmem]
> 
> Recently it was discovered that the problem goes beyond RAM vs PMEM
> collisions as some platform produce PMEM vs PMEM collisions within a
> given section. The libnvdimm workaround for that case revealed that the
> libnvdimm section-alignment-padding implementation has been broken for a
> long while. A fix for that long-standing breakage introduces as many
> problems as it solves as it would require a backward-incompatible change
> to the namespace metadata interpretation. Instead of that dubious route
> [1], address the root problem in the memory-hotplug implementation.
> 
> [1]: https://lore.kernel.org/r/155000671719.348031.2347363160141119237.stgit@dwillia2-desk3.amr.corp.intel.com
> 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>
> ---
>  mm/sparse.c |  223 ++++++++++++++++++++++++++++++++++++++++-------------------
>  1 file changed, 150 insertions(+), 73 deletions(-)
> 
> diff --git a/mm/sparse.c b/mm/sparse.c
> index 198371e5fc87..419a3620af6e 100644
> --- a/mm/sparse.c
> +++ b/mm/sparse.c
> @@ -83,8 +83,15 @@ static int __meminit sparse_index_init(unsigned long section_nr, int nid)
>  	unsigned long root = SECTION_NR_TO_ROOT(section_nr);
>  	struct mem_section *section;
>  
> +	/*
> +	 * An existing section is possible in the sub-section hotplug
> +	 * case. First hot-add instantiates, follow-on hot-add reuses
> +	 * the existing section.
> +	 *
> +	 * The mem_hotplug_lock resolves the apparent race below.
> +	 */
>  	if (mem_section[root])
> -		return -EEXIST;
> +		return 0;

Just a sidenote: we do not bail out on -EEXIST, so it should be fine if we
stick with it.
But if not, I would then clean up sparse_add_section:

--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -901,13 +901,12 @@ int __meminit sparse_add_section(int nid, unsigned long start_pfn,
        int ret;
 
        ret = sparse_index_init(section_nr, nid);
-       if (ret < 0 && ret != -EEXIST)
+       if (ret < 0)
                return ret;
 
        memmap = section_activate(nid, start_pfn, nr_pages, altmap);
        if (IS_ERR(memmap))
                return PTR_ERR(memmap);
-       ret = 0;


> +
> +	if (!mask)
> +		rc = -EINVAL;
> +	else if (mask & ms->usage->map_active)

	else if (ms->usage->map_active) should be enough?

> +		rc = -EEXIST;
> +	else
> +		ms->usage->map_active |= mask;
> +
> +	if (rc) {
> +		if (usage)
> +			ms->usage = NULL;
> +		kfree(usage);
> +		return ERR_PTR(rc);
> +	}
> +
> +	/*
> +	 * The early init code does not consider partially populated
> +	 * initial sections, it simply assumes that memory will never be
> +	 * referenced.  If we hot-add memory into such a section then we
> +	 * do not need to populate the memmap and can simply reuse what
> +	 * is already there.
> +	 */

This puzzles me a bit.
I think we cannot have partially populated early sections, can we?
And how we even come to hot-add memory into those?

Could you please elaborate a bit here?

> +	ms = __pfn_to_section(start_pfn);
>  	section_mark_present(ms);
> -	sparse_init_one_section(ms, section_nr, memmap, usage);
> +	sparse_init_one_section(ms, section_nr, memmap, ms->usage);
>  
> -out:
> -	if (ret < 0) {
> -		kfree(usage);
> -		depopulate_section_memmap(start_pfn, PAGES_PER_SECTION, altmap);
> -	}
> +	if (ret < 0)
> +		section_deactivate(start_pfn, nr_pages, nid, altmap);

Uhm, if my eyes do not trick me, ret is only used for the return value from
sparse_index_init(), so this is not needed. Can we get rid of it?

Unfortunately I am running out of time, but I plan to keep reviewing this patch
in the next few days.

-- 
Oscar Salvador
SUSE L3

Re: [PATCH v7 09/12] mm/sparsemem: Support sub-section hotplug

[Dan Williams]

On Fri, May 3, 2019 at 5:56 AM Oscar Salvador <osalvador@suse.de> wrote:
>
> On Wed, May 01, 2019 at 10:56:10PM -0700, Dan Williams wrote:
> > The libnvdimm sub-system has suffered a series of hacks and broken
> > workarounds for the memory-hotplug implementation's awkward
> > section-aligned (128MB) granularity. For example the following backtrace
> > is emitted when attempting arch_add_memory() with physical address
> > ranges that intersect 'System RAM' (RAM) with 'Persistent Memory' (PMEM)
> > within a given section:
> >
> >  WARNING: CPU: 0 PID: 558 at kernel/memremap.c:300 devm_memremap_pages+0x3b5/0x4c0
> >  devm_memremap_pages attempted on mixed region [mem 0x200000000-0x2fbffffff flags 0x200]
> >  [..]
> >  Call Trace:
> >    dump_stack+0x86/0xc3
> >    __warn+0xcb/0xf0
> >    warn_slowpath_fmt+0x5f/0x80
> >    devm_memremap_pages+0x3b5/0x4c0
> >    __wrap_devm_memremap_pages+0x58/0x70 [nfit_test_iomap]
> >    pmem_attach_disk+0x19a/0x440 [nd_pmem]
> >
> > Recently it was discovered that the problem goes beyond RAM vs PMEM
> > collisions as some platform produce PMEM vs PMEM collisions within a
> > given section. The libnvdimm workaround for that case revealed that the
> > libnvdimm section-alignment-padding implementation has been broken for a
> > long while. A fix for that long-standing breakage introduces as many
> > problems as it solves as it would require a backward-incompatible change
> > to the namespace metadata interpretation. Instead of that dubious route
> > [1], address the root problem in the memory-hotplug implementation.
> >
> > [1]: https://lore.kernel.org/r/155000671719.348031.2347363160141119237.stgit@dwillia2-desk3.amr.corp.intel.com
> > 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>
> > ---
> >  mm/sparse.c |  223 ++++++++++++++++++++++++++++++++++++++++-------------------
> >  1 file changed, 150 insertions(+), 73 deletions(-)
> >
> > diff --git a/mm/sparse.c b/mm/sparse.c
> > index 198371e5fc87..419a3620af6e 100644
> > --- a/mm/sparse.c
> > +++ b/mm/sparse.c
> > @@ -83,8 +83,15 @@ static int __meminit sparse_index_init(unsigned long section_nr, int nid)
> >       unsigned long root = SECTION_NR_TO_ROOT(section_nr);
> >       struct mem_section *section;
> >
> > +     /*
> > +      * An existing section is possible in the sub-section hotplug
> > +      * case. First hot-add instantiates, follow-on hot-add reuses
> > +      * the existing section.
> > +      *
> > +      * The mem_hotplug_lock resolves the apparent race below.
> > +      */
> >       if (mem_section[root])
> > -             return -EEXIST;
> > +             return 0;
>
> Just a sidenote: we do not bail out on -EEXIST, so it should be fine if we
> stick with it.
> But if not, I would then clean up sparse_add_section:
>
> --- a/mm/sparse.c
> +++ b/mm/sparse.c
> @@ -901,13 +901,12 @@ int __meminit sparse_add_section(int nid, unsigned long start_pfn,
>         int ret;
>
>         ret = sparse_index_init(section_nr, nid);
> -       if (ret < 0 && ret != -EEXIST)
> +       if (ret < 0)
>                 return ret;
>
>         memmap = section_activate(nid, start_pfn, nr_pages, altmap);
>         if (IS_ERR(memmap))
>                 return PTR_ERR(memmap);
> -       ret = 0;

Good catch, folded the cleanup.

>
>
> > +
> > +     if (!mask)
> > +             rc = -EINVAL;
> > +     else if (mask & ms->usage->map_active)
>
>         else if (ms->usage->map_active) should be enough?
>
> > +             rc = -EEXIST;
> > +     else
> > +             ms->usage->map_active |= mask;
> > +
> > +     if (rc) {
> > +             if (usage)
> > +                     ms->usage = NULL;
> > +             kfree(usage);
> > +             return ERR_PTR(rc);
> > +     }
> > +
> > +     /*
> > +      * The early init code does not consider partially populated
> > +      * initial sections, it simply assumes that memory will never be
> > +      * referenced.  If we hot-add memory into such a section then we
> > +      * do not need to populate the memmap and can simply reuse what
> > +      * is already there.
> > +      */
>
> This puzzles me a bit.
> I think we cannot have partially populated early sections, can we?

Yes, at boot memory need not be section aligned it has historically
been handled as a un-removable section of memory with holes.

> And how we even come to hot-add memory into those?
>
> Could you please elaborate a bit here?

Those sections are excluded from add_memory_resource() adding more
memory, but arch_add_memory() with sub-section support can fill in the
subsection holes in mem_map.

>
> > +     ms = __pfn_to_section(start_pfn);
> >       section_mark_present(ms);
> > -     sparse_init_one_section(ms, section_nr, memmap, usage);
> > +     sparse_init_one_section(ms, section_nr, memmap, ms->usage);
> >
> > -out:
> > -     if (ret < 0) {
> > -             kfree(usage);
> > -             depopulate_section_memmap(start_pfn, PAGES_PER_SECTION, altmap);
> > -     }
> > +     if (ret < 0)
> > +             section_deactivate(start_pfn, nr_pages, nid, altmap);
>
> Uhm, if my eyes do not trick me, ret is only used for the return value from
> sparse_index_init(), so this is not needed. Can we get rid of it?

Yes, these can go.

Apologies for the delay and missing these comments in the v8 posting.

[PATCH v7 10/12] mm/devm_memremap_pages: Enable sub-section remap

[Dan Williams]

Teach devm_memremap_pages() about the new sub-section capabilities of
arch_{add,remove}_memory(). Effectively, just replace all usage of
align_start, align_end, and align_size with res->start, res->end, and
resource_size(res). The existing sanity check will still make sure that
the two separate remap attempts do not collide within a sub-section (2MB
on x86).

Cc: Michal Hocko <mhocko@suse.com>
Cc: Toshi Kani <toshi.kani@hpe.com>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 kernel/memremap.c |   61 +++++++++++++++++++++--------------------------------
 1 file changed, 24 insertions(+), 37 deletions(-)

diff --git a/kernel/memremap.c b/kernel/memremap.c
index f355586ea54a..425904858d97 100644
--- a/kernel/memremap.c
+++ b/kernel/memremap.c
@@ -59,7 +59,7 @@ static unsigned long pfn_first(struct dev_pagemap *pgmap)
 	struct vmem_altmap *altmap = &pgmap->altmap;
 	unsigned long pfn;
 
-	pfn = res->start >> PAGE_SHIFT;
+	pfn = PHYS_PFN(res->start);
 	if (pgmap->altmap_valid)
 		pfn += vmem_altmap_offset(altmap);
 	return pfn;
@@ -87,7 +87,6 @@ static void devm_memremap_pages_release(void *data)
 	struct dev_pagemap *pgmap = data;
 	struct device *dev = pgmap->dev;
 	struct resource *res = &pgmap->res;
-	resource_size_t align_start, align_size;
 	unsigned long pfn;
 	int nid;
 
@@ -96,25 +95,21 @@ static void devm_memremap_pages_release(void *data)
 		put_page(pfn_to_page(pfn));
 
 	/* pages are dead and unused, undo the arch mapping */
-	align_start = res->start & ~(PA_SECTION_SIZE - 1);
-	align_size = ALIGN(res->start + resource_size(res), PA_SECTION_SIZE)
-		- align_start;
-
-	nid = page_to_nid(pfn_to_page(align_start >> PAGE_SHIFT));
+	nid = page_to_nid(pfn_to_page(PHYS_PFN(res->start)));
 
 	mem_hotplug_begin();
 	if (pgmap->type == MEMORY_DEVICE_PRIVATE) {
-		pfn = align_start >> PAGE_SHIFT;
+		pfn = PHYS_PFN(res->start);
 		__remove_pages(page_zone(pfn_to_page(pfn)), pfn,
-				align_size >> PAGE_SHIFT, NULL);
+				PHYS_PFN(resource_size(res)), NULL);
 	} else {
-		arch_remove_memory(nid, align_start, align_size,
+		arch_remove_memory(nid, res->start, resource_size(res),
 				pgmap->altmap_valid ? &pgmap->altmap : NULL);
-		kasan_remove_zero_shadow(__va(align_start), align_size);
+		kasan_remove_zero_shadow(__va(res->start), resource_size(res));
 	}
 	mem_hotplug_done();
 
-	untrack_pfn(NULL, PHYS_PFN(align_start), align_size);
+	untrack_pfn(NULL, PHYS_PFN(res->start), resource_size(res));
 	pgmap_array_delete(res);
 	dev_WARN_ONCE(dev, pgmap->altmap.alloc,
 		      "%s: failed to free all reserved pages\n", __func__);
@@ -141,16 +136,13 @@ static void devm_memremap_pages_release(void *data)
  */
 void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
 {
-	resource_size_t align_start, align_size, align_end;
-	struct vmem_altmap *altmap = pgmap->altmap_valid ?
-			&pgmap->altmap : NULL;
 	struct resource *res = &pgmap->res;
 	struct dev_pagemap *conflict_pgmap;
 	struct mhp_restrictions restrictions = {
 		/*
 		 * We do not want any optional features only our own memmap
 		*/
-		.altmap = altmap,
+		.altmap = pgmap->altmap_valid ? &pgmap->altmap : NULL,
 	};
 	pgprot_t pgprot = PAGE_KERNEL;
 	int error, nid, is_ram;
@@ -158,26 +150,21 @@ void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
 	if (!pgmap->ref || !pgmap->kill)
 		return ERR_PTR(-EINVAL);
 
-	align_start = res->start & ~(PA_SECTION_SIZE - 1);
-	align_size = ALIGN(res->start + resource_size(res), PA_SECTION_SIZE)
-		- align_start;
-	align_end = align_start + align_size - 1;
-
-	conflict_pgmap = get_dev_pagemap(PHYS_PFN(align_start), NULL);
+	conflict_pgmap = get_dev_pagemap(PHYS_PFN(res->start), NULL);
 	if (conflict_pgmap) {
 		dev_WARN(dev, "Conflicting mapping in same section\n");
 		put_dev_pagemap(conflict_pgmap);
 		return ERR_PTR(-ENOMEM);
 	}
 
-	conflict_pgmap = get_dev_pagemap(PHYS_PFN(align_end), NULL);
+	conflict_pgmap = get_dev_pagemap(PHYS_PFN(res->end), NULL);
 	if (conflict_pgmap) {
 		dev_WARN(dev, "Conflicting mapping in same section\n");
 		put_dev_pagemap(conflict_pgmap);
 		return ERR_PTR(-ENOMEM);
 	}
 
-	is_ram = region_intersects(align_start, align_size,
+	is_ram = region_intersects(res->start, resource_size(res),
 		IORESOURCE_SYSTEM_RAM, IORES_DESC_NONE);
 
 	if (is_ram != REGION_DISJOINT) {
@@ -198,8 +185,8 @@ void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
 	if (nid < 0)
 		nid = numa_mem_id();
 
-	error = track_pfn_remap(NULL, &pgprot, PHYS_PFN(align_start), 0,
-			align_size);
+	error = track_pfn_remap(NULL, &pgprot, PHYS_PFN(res->start), 0,
+			resource_size(res));
 	if (error)
 		goto err_pfn_remap;
 
@@ -217,25 +204,25 @@ void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
 	 * arch_add_memory().
 	 */
 	if (pgmap->type == MEMORY_DEVICE_PRIVATE) {
-		error = add_pages(nid, align_start >> PAGE_SHIFT,
-				align_size >> PAGE_SHIFT, &restrictions);
+		error = add_pages(nid, PHYS_PFN(res->start),
+				PHYS_PFN(resource_size(res)), &restrictions);
 	} else {
-		error = kasan_add_zero_shadow(__va(align_start), align_size);
+		error = kasan_add_zero_shadow(__va(res->start), resource_size(res));
 		if (error) {
 			mem_hotplug_done();
 			goto err_kasan;
 		}
 
-		error = arch_add_memory(nid, align_start, align_size,
-					&restrictions);
+		error = arch_add_memory(nid, res->start, resource_size(res),
+				&restrictions);
 	}
 
 	if (!error) {
 		struct zone *zone;
 
 		zone = &NODE_DATA(nid)->node_zones[ZONE_DEVICE];
-		move_pfn_range_to_zone(zone, align_start >> PAGE_SHIFT,
-				align_size >> PAGE_SHIFT, altmap);
+		move_pfn_range_to_zone(zone, PHYS_PFN(res->start),
+				PHYS_PFN(resource_size(res)), restrictions.altmap);
 	}
 
 	mem_hotplug_done();
@@ -247,8 +234,8 @@ void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
 	 * to allow us to do the work while not holding the hotplug lock.
 	 */
 	memmap_init_zone_device(&NODE_DATA(nid)->node_zones[ZONE_DEVICE],
-				align_start >> PAGE_SHIFT,
-				align_size >> PAGE_SHIFT, pgmap);
+				PHYS_PFN(res->start),
+				PHYS_PFN(resource_size(res)), pgmap);
 	percpu_ref_get_many(pgmap->ref, pfn_end(pgmap) - pfn_first(pgmap));
 
 	error = devm_add_action_or_reset(dev, devm_memremap_pages_release,
@@ -259,9 +246,9 @@ void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
 	return __va(res->start);
 
  err_add_memory:
-	kasan_remove_zero_shadow(__va(align_start), align_size);
+	kasan_remove_zero_shadow(__va(res->start), resource_size(res));
  err_kasan:
-	untrack_pfn(NULL, PHYS_PFN(align_start), align_size);
+	untrack_pfn(NULL, PHYS_PFN(res->start), resource_size(res));
  err_pfn_remap:
 	pgmap_array_delete(res);
  err_array:

[PATCH v7 11/12] libnvdimm/pfn: Fix fsdax-mode namespace info-block zero-fields

[Dan Williams]

At namespace creation time there is the potential for the "expected to
be zero" fields of a 'pfn' info-block to be filled with indeterminate
data. While the kernel buffer is zeroed on allocation it is immediately
overwritten by nd_pfn_validate() filling it with the current contents of
the on-media info-block location. For fields like, 'flags' and the
'padding' it potentially means that future implementations can not rely
on those fields being zero.

In preparation to stop using the 'start_pad' and 'end_trunc' fields for
section alignment, arrange for fields that are not explicitly
initialized to be guaranteed zero. Bump the minor version to indicate it
is safe to assume the 'padding' and 'flags' are zero. Otherwise, this
corruption is expected to benign since all other critical fields are
explicitly initialized.

Fixes: 32ab0a3f5170 ("libnvdimm, pmem: 'struct page' for pmem")
Cc: <stable@vger.kernel.org>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 drivers/nvdimm/dax_devs.c |    2 +-
 drivers/nvdimm/pfn.h      |    1 +
 drivers/nvdimm/pfn_devs.c |   18 +++++++++++++++---
 3 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/drivers/nvdimm/dax_devs.c b/drivers/nvdimm/dax_devs.c
index 0453f49dc708..326f02ffca81 100644
--- a/drivers/nvdimm/dax_devs.c
+++ b/drivers/nvdimm/dax_devs.c
@@ -126,7 +126,7 @@ int nd_dax_probe(struct device *dev, struct nd_namespace_common *ndns)
 	nvdimm_bus_unlock(&ndns->dev);
 	if (!dax_dev)
 		return -ENOMEM;
-	pfn_sb = devm_kzalloc(dev, sizeof(*pfn_sb), GFP_KERNEL);
+	pfn_sb = devm_kmalloc(dev, sizeof(*pfn_sb), GFP_KERNEL);
 	nd_pfn->pfn_sb = pfn_sb;
 	rc = nd_pfn_validate(nd_pfn, DAX_SIG);
 	dev_dbg(dev, "dax: %s\n", rc == 0 ? dev_name(dax_dev) : "<none>");
diff --git a/drivers/nvdimm/pfn.h b/drivers/nvdimm/pfn.h
index dde9853453d3..e901e3a3b04c 100644
--- a/drivers/nvdimm/pfn.h
+++ b/drivers/nvdimm/pfn.h
@@ -36,6 +36,7 @@ struct nd_pfn_sb {
 	__le32 end_trunc;
 	/* minor-version-2 record the base alignment of the mapping */
 	__le32 align;
+	/* minor-version-3 guarantee the padding and flags are zero */
 	u8 padding[4000];
 	__le64 checksum;
 };
diff --git a/drivers/nvdimm/pfn_devs.c b/drivers/nvdimm/pfn_devs.c
index 01f40672507f..a2406253eb70 100644
--- a/drivers/nvdimm/pfn_devs.c
+++ b/drivers/nvdimm/pfn_devs.c
@@ -420,6 +420,15 @@ static int nd_pfn_clear_memmap_errors(struct nd_pfn *nd_pfn)
 	return 0;
 }
 
+/**
+ * nd_pfn_validate - read and validate info-block
+ * @nd_pfn: fsdax namespace runtime state / properties
+ * @sig: 'devdax' or 'fsdax' signature
+ *
+ * Upon return the info-block buffer contents (->pfn_sb) are
+ * indeterminate when validation fails, and a coherent info-block
+ * otherwise.
+ */
 int nd_pfn_validate(struct nd_pfn *nd_pfn, const char *sig)
 {
 	u64 checksum, offset;
@@ -565,7 +574,7 @@ int nd_pfn_probe(struct device *dev, struct nd_namespace_common *ndns)
 	nvdimm_bus_unlock(&ndns->dev);
 	if (!pfn_dev)
 		return -ENOMEM;
-	pfn_sb = devm_kzalloc(dev, sizeof(*pfn_sb), GFP_KERNEL);
+	pfn_sb = devm_kmalloc(dev, sizeof(*pfn_sb), GFP_KERNEL);
 	nd_pfn = to_nd_pfn(pfn_dev);
 	nd_pfn->pfn_sb = pfn_sb;
 	rc = nd_pfn_validate(nd_pfn, PFN_SIG);
@@ -702,7 +711,7 @@ static int nd_pfn_init(struct nd_pfn *nd_pfn)
 	u64 checksum;
 	int rc;
 
-	pfn_sb = devm_kzalloc(&nd_pfn->dev, sizeof(*pfn_sb), GFP_KERNEL);
+	pfn_sb = devm_kmalloc(&nd_pfn->dev, sizeof(*pfn_sb), GFP_KERNEL);
 	if (!pfn_sb)
 		return -ENOMEM;
 
@@ -711,11 +720,14 @@ static int nd_pfn_init(struct nd_pfn *nd_pfn)
 		sig = DAX_SIG;
 	else
 		sig = PFN_SIG;
+
 	rc = nd_pfn_validate(nd_pfn, sig);
 	if (rc != -ENODEV)
 		return rc;
 
 	/* no info block, do init */;
+	memset(pfn_sb, 0, sizeof(*pfn_sb));
+
 	nd_region = to_nd_region(nd_pfn->dev.parent);
 	if (nd_region->ro) {
 		dev_info(&nd_pfn->dev,
@@ -768,7 +780,7 @@ static int nd_pfn_init(struct nd_pfn *nd_pfn)
 	memcpy(pfn_sb->uuid, nd_pfn->uuid, 16);
 	memcpy(pfn_sb->parent_uuid, nd_dev_to_uuid(&ndns->dev), 16);
 	pfn_sb->version_major = cpu_to_le16(1);
-	pfn_sb->version_minor = cpu_to_le16(2);
+	pfn_sb->version_minor = cpu_to_le16(3);
 	pfn_sb->start_pad = cpu_to_le32(start_pad);
 	pfn_sb->end_trunc = cpu_to_le32(end_trunc);
 	pfn_sb->align = cpu_to_le32(nd_pfn->align);

[PATCH v7 12/12] libnvdimm/pfn: Stop padding pmem namespaces to section alignment

[Dan Williams]

Now that the mm core supports section-unaligned hotplug of ZONE_DEVICE
memory, we no longer need to add padding at pfn/dax device creation
time. The kernel will still honor padding established by older kernels.

Reported-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 drivers/nvdimm/pfn.h      |   11 ++-----
 drivers/nvdimm/pfn_devs.c |   75 +++++++--------------------------------------
 include/linux/mmzone.h    |    4 ++
 3 files changed, 19 insertions(+), 71 deletions(-)

diff --git a/drivers/nvdimm/pfn.h b/drivers/nvdimm/pfn.h
index e901e3a3b04c..ae589cc528f2 100644
--- a/drivers/nvdimm/pfn.h
+++ b/drivers/nvdimm/pfn.h
@@ -41,18 +41,13 @@ struct nd_pfn_sb {
 	__le64 checksum;
 };
 
-#ifdef CONFIG_SPARSEMEM
-#define PFN_SECTION_ALIGN_DOWN(x) SECTION_ALIGN_DOWN(x)
-#define PFN_SECTION_ALIGN_UP(x) SECTION_ALIGN_UP(x)
-#else
 /*
  * In this case ZONE_DEVICE=n and we will disable 'pfn' device support,
  * but we still want pmem to compile.
  */
-#define PFN_SECTION_ALIGN_DOWN(x) (x)
-#define PFN_SECTION_ALIGN_UP(x) (x)
+#ifndef SUB_SECTION_ALIGN_DOWN
+#define SUB_SECTION_ALIGN_DOWN(x) (x)
+#define SUB_SECTION_ALIGN_UP(x) (x)
 #endif
 
-#define PHYS_SECTION_ALIGN_DOWN(x) PFN_PHYS(PFN_SECTION_ALIGN_DOWN(PHYS_PFN(x)))
-#define PHYS_SECTION_ALIGN_UP(x) PFN_PHYS(PFN_SECTION_ALIGN_UP(PHYS_PFN(x)))
 #endif /* __NVDIMM_PFN_H */
diff --git a/drivers/nvdimm/pfn_devs.c b/drivers/nvdimm/pfn_devs.c
index a2406253eb70..7bdaaf3dc77e 100644
--- a/drivers/nvdimm/pfn_devs.c
+++ b/drivers/nvdimm/pfn_devs.c
@@ -595,14 +595,14 @@ static u32 info_block_reserve(void)
 }
 
 /*
- * We hotplug memory at section granularity, pad the reserved area from
- * the previous section base to the namespace base address.
+ * We hotplug memory at sub-section granularity, pad the reserved area
+ * from the previous section base to the namespace base address.
  */
 static unsigned long init_altmap_base(resource_size_t base)
 {
 	unsigned long base_pfn = PHYS_PFN(base);
 
-	return PFN_SECTION_ALIGN_DOWN(base_pfn);
+	return SUB_SECTION_ALIGN_DOWN(base_pfn);
 }
 
 static unsigned long init_altmap_reserve(resource_size_t base)
@@ -610,7 +610,7 @@ static unsigned long init_altmap_reserve(resource_size_t base)
 	unsigned long reserve = info_block_reserve() >> PAGE_SHIFT;
 	unsigned long base_pfn = PHYS_PFN(base);
 
-	reserve += base_pfn - PFN_SECTION_ALIGN_DOWN(base_pfn);
+	reserve += base_pfn - SUB_SECTION_ALIGN_DOWN(base_pfn);
 	return reserve;
 }
 
@@ -641,8 +641,7 @@ static int __nvdimm_setup_pfn(struct nd_pfn *nd_pfn, struct dev_pagemap *pgmap)
 		nd_pfn->npfns = le64_to_cpu(pfn_sb->npfns);
 		pgmap->altmap_valid = false;
 	} else if (nd_pfn->mode == PFN_MODE_PMEM) {
-		nd_pfn->npfns = PFN_SECTION_ALIGN_UP((resource_size(res)
-					- offset) / PAGE_SIZE);
+		nd_pfn->npfns = PHYS_PFN((resource_size(res) - offset));
 		if (le64_to_cpu(nd_pfn->pfn_sb->npfns) > nd_pfn->npfns)
 			dev_info(&nd_pfn->dev,
 					"number of pfns truncated from %lld to %ld\n",
@@ -658,50 +657,10 @@ static int __nvdimm_setup_pfn(struct nd_pfn *nd_pfn, struct dev_pagemap *pgmap)
 	return 0;
 }
 
-static u64 phys_pmem_align_down(struct nd_pfn *nd_pfn, u64 phys)
-{
-	return min_t(u64, PHYS_SECTION_ALIGN_DOWN(phys),
-			ALIGN_DOWN(phys, nd_pfn->align));
-}
-
-/*
- * Check if pmem collides with 'System RAM', or other regions when
- * section aligned.  Trim it accordingly.
- */
-static void trim_pfn_device(struct nd_pfn *nd_pfn, u32 *start_pad, u32 *end_trunc)
-{
-	struct nd_namespace_common *ndns = nd_pfn->ndns;
-	struct nd_namespace_io *nsio = to_nd_namespace_io(&ndns->dev);
-	struct nd_region *nd_region = to_nd_region(nd_pfn->dev.parent);
-	const resource_size_t start = nsio->res.start;
-	const resource_size_t end = start + resource_size(&nsio->res);
-	resource_size_t adjust, size;
-
-	*start_pad = 0;
-	*end_trunc = 0;
-
-	adjust = start - PHYS_SECTION_ALIGN_DOWN(start);
-	size = resource_size(&nsio->res) + adjust;
-	if (region_intersects(start - adjust, size, IORESOURCE_SYSTEM_RAM,
-				IORES_DESC_NONE) == REGION_MIXED
-			|| nd_region_conflict(nd_region, start - adjust, size))
-		*start_pad = PHYS_SECTION_ALIGN_UP(start) - start;
-
-	/* Now check that end of the range does not collide. */
-	adjust = PHYS_SECTION_ALIGN_UP(end) - end;
-	size = resource_size(&nsio->res) + adjust;
-	if (region_intersects(start, size, IORESOURCE_SYSTEM_RAM,
-				IORES_DESC_NONE) == REGION_MIXED
-			|| !IS_ALIGNED(end, nd_pfn->align)
-			|| nd_region_conflict(nd_region, start, size))
-		*end_trunc = end - phys_pmem_align_down(nd_pfn, end);
-}
-
 static int nd_pfn_init(struct nd_pfn *nd_pfn)
 {
 	struct nd_namespace_common *ndns = nd_pfn->ndns;
 	struct nd_namespace_io *nsio = to_nd_namespace_io(&ndns->dev);
-	u32 start_pad, end_trunc, reserve = info_block_reserve();
 	resource_size_t start, size;
 	struct nd_region *nd_region;
 	struct nd_pfn_sb *pfn_sb;
@@ -736,43 +695,35 @@ static int nd_pfn_init(struct nd_pfn *nd_pfn)
 		return -ENXIO;
 	}
 
-	memset(pfn_sb, 0, sizeof(*pfn_sb));
-
-	trim_pfn_device(nd_pfn, &start_pad, &end_trunc);
-	if (start_pad + end_trunc)
-		dev_info(&nd_pfn->dev, "%s alignment collision, truncate %d bytes\n",
-				dev_name(&ndns->dev), start_pad + end_trunc);
-
 	/*
 	 * Note, we use 64 here for the standard size of struct page,
 	 * debugging options may cause it to be larger in which case the
 	 * implementation will limit the pfns advertised through
 	 * ->direct_access() to those that are included in the memmap.
 	 */
-	start = nsio->res.start + start_pad;
+	start = nsio->res.start;
 	size = resource_size(&nsio->res);
-	npfns = PFN_SECTION_ALIGN_UP((size - start_pad - end_trunc - reserve)
-			/ PAGE_SIZE);
+	npfns = PHYS_PFN(size - SZ_8K);
 	if (nd_pfn->mode == PFN_MODE_PMEM) {
 		/*
 		 * The altmap should be padded out to the block size used
 		 * when populating the vmemmap. This *should* be equal to
 		 * PMD_SIZE for most architectures.
 		 */
-		offset = ALIGN(start + reserve + 64 * npfns,
-				max(nd_pfn->align, PMD_SIZE)) - start;
+		offset = ALIGN(start + SZ_8K + 64 * npfns,
+				max(nd_pfn->align, SECTION_ACTIVE_SIZE)) - start;
 	} else if (nd_pfn->mode == PFN_MODE_RAM)
-		offset = ALIGN(start + reserve, nd_pfn->align) - start;
+		offset = ALIGN(start + SZ_8K, nd_pfn->align) - start;
 	else
 		return -ENXIO;
 
-	if (offset + start_pad + end_trunc >= size) {
+	if (offset >= size) {
 		dev_err(&nd_pfn->dev, "%s unable to satisfy requested alignment\n",
 				dev_name(&ndns->dev));
 		return -ENXIO;
 	}
 
-	npfns = (size - offset - start_pad - end_trunc) / SZ_4K;
+	npfns = PHYS_PFN(size - offset);
 	pfn_sb->mode = cpu_to_le32(nd_pfn->mode);
 	pfn_sb->dataoff = cpu_to_le64(offset);
 	pfn_sb->npfns = cpu_to_le64(npfns);
@@ -781,8 +732,6 @@ static int nd_pfn_init(struct nd_pfn *nd_pfn)
 	memcpy(pfn_sb->parent_uuid, nd_dev_to_uuid(&ndns->dev), 16);
 	pfn_sb->version_major = cpu_to_le16(1);
 	pfn_sb->version_minor = cpu_to_le16(3);
-	pfn_sb->start_pad = cpu_to_le32(start_pad);
-	pfn_sb->end_trunc = cpu_to_le32(end_trunc);
 	pfn_sb->align = cpu_to_le32(nd_pfn->align);
 	checksum = nd_sb_checksum((struct nd_gen_sb *) pfn_sb);
 	pfn_sb->checksum = cpu_to_le64(checksum);
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 3237c5e456df..d2445c483ad4 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -1155,6 +1155,10 @@ static inline unsigned long section_nr_to_pfn(unsigned long sec)
 #define PAGES_PER_SUB_SECTION (SECTION_ACTIVE_SIZE / PAGE_SIZE)
 #define PAGE_SUB_SECTION_MASK (~(PAGES_PER_SUB_SECTION-1))
 
+#define SUB_SECTION_ALIGN_UP(pfn) (((pfn) + PAGES_PER_SUB_SECTION - 1) \
+		& PAGE_SUB_SECTION_MASK)
+#define SUB_SECTION_ALIGN_DOWN(pfn) ((pfn) & PAGE_SUB_SECTION_MASK)
+
 struct mem_section_usage {
 	/*
 	 * SECTION_ACTIVE_SIZE portions of the section that are populated in