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mm/sparsemem: support sub-section hotplug

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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: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Oscar Salvador <osalvador@suse.de>
Tested-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>	[ppc64]
Reviewed-by: Oscar 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Dan Williams 2019-07-18 15:58:26 -07:00 committed by Linus Torvalds
parent 7ea6216049
commit ba72b4c8cf
4 changed files with 141 additions and 96 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/linux/memory_hotplug.h
View File

@ -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,

27
mm/memory_hotplug.c
View File

@ -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);
}
/**

2
mm/page_alloc.c
View File

@ -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);

206
mm/sparse.c
View File

@ -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 */