Commit ba72b4c8 authored by Dan Williams's avatar Dan Williams Committed by Linus Torvalds
Browse files

mm/sparsemem: support sub-section hotplug 

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:

    # cat /proc/iomem | grep -A1 -B1 Persistent\ Memory
    100000000-1ffffffff : System RAM
    200000000-303ffffff : Persistent Memory (legacy)
    304000000-43fffffff : System RAM
    440000000-23ffffffff : Persistent Memory
    2400000000-43bfffffff : Persistent Memory
      2400000000-43bfffffff : namespace2.0

    WARNING: CPU: 38 PID: 928 at arch/x86/mm/init_64.c:850 add_pages+0x5c/0x60
    [..]
    RIP: 0010:add_pages+0x5c/0x60
    [..]
    Call Trace:
     devm_memremap_pages+0x460/0x6e0
     pmem_attach_disk+0x29e/0x680 [nd_pmem]
     ? nd_dax_probe+0xfc/0x120 [libnvdimm]
     nvdimm_bus_probe+0x66/0x160 [libnvdimm]

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.

Note that EEXIST is no longer treated as success as that is how
sparse_add_section() reports subsection collisions, it was also obviated
by recent changes to perform the request_region() for 'System RAM'
before arch_add_memory() in the add_memory() sequence.

[1] https://lore.kernel.org/r/155000671719.348031.2347363160141119237.stgit@dwillia2-desk3.amr.corp.intel.com

[osalvador@suse.de: fix deactivate_section for early sections]
  Link: http://lkml.kernel.org/r/20190715081549.32577-2-osalvador@suse.de
Link: http://lkml.kernel.org/r/156092354368.979959.6232443923440952359.stgit@dwillia2-desk3.amr.corp.intel.com


Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
Signed-off-by: default avatarOscar Salvador <osalvador@suse.de>
Tested-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>	[ppc64]
Reviewed-by: default avatarOscar Salvador <osalvador@suse.de>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Logan Gunthorpe <logang@deltatee.com>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Jane Chu <jane.chu@oracle.com>
Cc: Jeff Moyer <jmoyer@redhat.com>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: Toshi Kani <toshi.kani@hpe.com>
Cc: Wei Yang <richardw.yang@linux.intel.com>
Cc: Jason Gunthorpe <jgg@mellanox.com>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 7ea62160

include/linux/memory_hotplug.h

+1 −1
Original line number Diff line number Diff line
@@ -348,7 +348,7 @@ extern void move_pfn_range_to_zone(struct zone *zone, unsigned long start_pfn, 
extern bool is_memblock_offlined(struct memory_block *mem);

extern int sparse_add_section(int nid, unsigned long pfn,

		unsigned long nr_pages, struct vmem_altmap *altmap);

extern void sparse_remove_one_section(struct mem_section *ms,

extern void sparse_remove_section(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,

mm/memory_hotplug.c

+4 −23
Original line number Diff line number Diff line
@@ -252,18 +252,6 @@ 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 pfn,

		unsigned long nr_pages,	struct vmem_altmap *altmap)

{

	int ret;



	if (pfn_valid(pfn))

		return -EEXIST;



	ret = sparse_add_section(nid, pfn, nr_pages, altmap);

	return ret < 0 ? ret : 0;

}



static int check_pfn_span(unsigned long pfn, unsigned long nr_pages,

		const char *reason)

{
@@ -327,18 +315,11 @@ int __ref __add_pages(int nid, unsigned long pfn, unsigned long nr_pages, 


		pfns = min(nr_pages, PAGES_PER_SECTION

				- (pfn & ~PAGE_SECTION_MASK));

		err = __add_section(nid, pfn, pfns, altmap);

		err = sparse_add_section(nid, pfn, pfns, altmap);

		if (err)

			break;

		pfn += pfns;

		nr_pages -= pfns;



		/*

		 * EEXIST is finally dealt with by ioresource collision

		 * check. see add_memory() => register_memory_resource()

		 * Warning will be printed if there is collision.

		 */

		if (err && (err != -EEXIST))

			break;

		err = 0;

		cond_resched();

	}

	vmemmap_populate_print_last();
@@ -541,7 +522,7 @@ static void __remove_section(struct zone *zone, unsigned long pfn, 
		return;



	__remove_zone(zone, pfn, nr_pages);

	sparse_remove_one_section(ms, pfn, nr_pages, map_offset, altmap);

	sparse_remove_section(ms, pfn, nr_pages, map_offset, altmap);

}



/**

mm/page_alloc.c

+1 −1
Original line number Diff line number Diff line
@@ -5974,7 +5974,7 @@ void __ref memmap_init_zone_device(struct zone *zone, 
		 * pfn out of zone.

		 *

		 * Please note that MEMMAP_HOTPLUG path doesn't clear memmap

		 * because this is done early in sparse_add_one_section

		 * because this is done early in section_activate()

		 */

		if (!(pfn & (pageblock_nr_pages - 1))) {

			set_pageblock_migratetype(page, MIGRATE_MOVABLE);

mm/sparse.c

+135 −71
Original line number Diff line number Diff line
@@ -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)
@@ -715,10 +722,120 @@ static void free_map_bootmem(struct page *memmap) 
}

#endif /* CONFIG_SPARSEMEM_VMEMMAP */



static void section_deactivate(unsigned long pfn, unsigned long nr_pages,

		struct vmem_altmap *altmap)

{

	DECLARE_BITMAP(map, SUBSECTIONS_PER_SECTION) = { 0 };

	DECLARE_BITMAP(tmp, SUBSECTIONS_PER_SECTION) = { 0 };

	struct mem_section *ms = __pfn_to_section(pfn);

	bool section_is_early = early_section(ms);

	struct page *memmap = NULL;

	unsigned long *subsection_map = ms->usage

		? &ms->usage->subsection_map[0] : NULL;



	subsection_mask_set(map, pfn, nr_pages);

	if (subsection_map)

		bitmap_and(tmp, map, subsection_map, SUBSECTIONS_PER_SECTION);



	if (WARN(!subsection_map || !bitmap_equal(tmp, map, SUBSECTIONS_PER_SECTION),

				"section already deactivated (%#lx + %ld)\n",

				pfn, nr_pages))

		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 subsection_map does not empty 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

	 */

	bitmap_xor(subsection_map, map, subsection_map, SUBSECTIONS_PER_SECTION);

	if (bitmap_empty(subsection_map, SUBSECTIONS_PER_SECTION)) {

		unsigned long section_nr = pfn_to_section_nr(pfn);



		if (!section_is_early) {

			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 (section_is_early && 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)

{

	DECLARE_BITMAP(map, SUBSECTIONS_PER_SECTION) = { 0 };

	struct mem_section *ms = __pfn_to_section(pfn);

	struct mem_section_usage *usage = NULL;

	unsigned long *subsection_map;

	struct page *memmap;

	int rc = 0;



	subsection_mask_set(map, pfn, nr_pages);



	if (!ms->usage) {

		usage = kzalloc(mem_section_usage_size(), GFP_KERNEL);

		if (!usage)

			return ERR_PTR(-ENOMEM);

		ms->usage = usage;

	}

	subsection_map = &ms->usage->subsection_map[0];



	if (bitmap_empty(map, SUBSECTIONS_PER_SECTION))

		rc = -EINVAL;

	else if (bitmap_intersects(map, subsection_map, SUBSECTIONS_PER_SECTION))

		rc = -EEXIST;

	else

		bitmap_or(subsection_map, map, subsection_map,

				SUBSECTIONS_PER_SECTION);



	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 && early_section(ms))

		return pfn_to_page(pfn);



	memmap = populate_section_memmap(pfn, nr_pages, nid, altmap);

	if (!memmap) {

		section_deactivate(pfn, nr_pages, 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.
@@ -732,51 +849,34 @@ 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)

	if (ret < 0)

		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);



	/*

	 * 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);

	set_section_nid(section_nr, nid);

	section_mark_present(ms);

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



out:

	if (ret < 0) {

		kfree(usage);

		depopulate_section_memmap(start_pfn, PAGES_PER_SECTION, altmap);

	}

	return ret;

	/* Align memmap to section boundary in the subsection case */

	if (section_nr_to_pfn(section_nr) != start_pfn)

		memmap = pfn_to_kaddr(section_nr_to_pfn(section_nr));

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



	return 0;

}



#ifdef CONFIG_MEMORY_FAILURE
@@ -809,48 +909,12 @@ static inline void clear_hwpoisoned_pages(struct page *memmap, int nr_pages) 
}

#endif



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

		struct mem_section_usage *usage, unsigned long pfn,

		unsigned long nr_pages, struct vmem_altmap *altmap)

{

	if (!usage)

		return;



	/*

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

	 */

	if (!early_section(ms)) {

		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_one_section(struct mem_section *ms, unsigned long pfn,

void sparse_remove_section(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, nr_pages - map_offset);

	free_section_usage(ms, memmap, usage, pfn, nr_pages, altmap);

	clear_hwpoisoned_pages(pfn_to_page(pfn) + map_offset,

			nr_pages - map_offset);

	section_deactivate(pfn, nr_pages, altmap);

}

#endif /* CONFIG_MEMORY_HOTPLUG */

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