The initial motivation for this change is persistent memory platforms
that, unfortunately, align the pmem range on a boundary less than a full
section (64M vs 128M), and may change the alignment from one boot to the
next. A secondary motivation is the arrival of prospective ZONE_DEVICE
users that want devm_memremap_pages() to map PCI-E device memory ranges
to enable peer-to-peer DMA.
Currently the nvdimm core injects padding when 'pfn' (struct page
mapping configuration) instances are created. However, not all users of
devm_memremap_pages() have the opportunity to inject such padding. Users
of the memmap=ss!nn kernel command line option can trigger the following
failure with unaligned parameters like "memmap=0xfc000000!8G":
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:
[<ffffffff814c0393>] dump_stack+0x86/0xc3
[<ffffffff810b173b>] __warn+0xcb/0xf0
[<ffffffff810b17bf>] warn_slowpath_fmt+0x5f/0x80
[<ffffffff811eb105>] devm_memremap_pages+0x3b5/0x4c0
[<ffffffffa006f308>] __wrap_devm_memremap_pages+0x58/0x70 [nfit_test_iomap]
[<ffffffffa00e231a>] pmem_attach_disk+0x19a/0x440 [nd_pmem]
Without this change a user could inadvertently lose access to nvdimm
namespaces by adding/removing other DIMMs in the platform leading to the
BIOS changing the base alignment of the namespace in an incompatible
fashion. With this support we can accommodate a BIOS changing the
namespace to any alignment provided it is >= SECTION_ACTIVE_SIZE.
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Logan Gunthorpe <logang@xxxxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Stephen Bates <stephen.bates@xxxxxxxxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
---
mm/sparse.c | 272 ++++++++++++++++++++++++++++++++++++++++++++---------------
1 file changed, 204 insertions(+), 68 deletions(-)
diff --git a/mm/sparse.c b/mm/sparse.c
index edb1d2a21a2e..cc9a865ac10d 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -24,6 +24,7 @@
#ifdef CONFIG_SPARSEMEM_EXTREME
struct mem_section *mem_section[NR_SECTION_ROOTS]
____cacheline_internodealigned_in_smp;
+static DEFINE_SPINLOCK(mem_section_lock); /* atomically instantiate new entries */
#else
struct mem_section mem_section[NR_SECTION_ROOTS][SECTIONS_PER_ROOT]
____cacheline_internodealigned_in_smp;
@@ -89,7 +90,22 @@ static int __meminit sparse_index_init(unsigned long section_nr, int nid)
if (!section)
return -ENOMEM;
- mem_section[root] = section;
+ spin_lock(&mem_section_lock);
+ if (mem_section[root] == NULL) {
+ mem_section[root] = section;
+ section = NULL;
+ }
+ spin_unlock(&mem_section_lock);
+
+ /*
+ * The only time we expect adding a section may race is during
+ * post-meminit hotplug. So, there is no expectation that 'section'
+ * leaks in the !slab_is_available() case.
+ */
+ if (section && slab_is_available()) {
+ kfree(section);
+ return -EEXIST;
+ }
return 0;
}
@@ -288,6 +304,15 @@ 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;
@@ -753,12 +778,176 @@ static void free_map_bootmem(struct page *memmap)
#endif /* CONFIG_MEMORY_HOTREMOVE */
#endif /* CONFIG_SPARSEMEM_VMEMMAP */
+static bool is_early_section(struct mem_section *ms)
+{
+ struct page *usemap_page;
+
+ usemap_page = virt_to_page(ms->usage->pageblock_flags);
+ if (PageSlab(usemap_page) || PageCompound(usemap_page))
+ return false;
+ else
+ return true;
+
+}
+
+#ifndef CONFIG_MEMORY_HOTREMOVE
+static void free_map_bootmem(struct page *memmap)
+{
+}
+#endif
+
+static void section_deactivate(struct pglist_data *pgdat, unsigned long pfn,
+ unsigned long nr_pages)
+{
+ bool early_section;
+ struct page *memmap = NULL;
+ struct mem_section_usage *usage = NULL;
+ int section_nr = pfn_to_section_nr(pfn);
+ struct mem_section *ms = __nr_to_section(section_nr);
+ unsigned long mask = section_active_mask(pfn, nr_pages), flags;
+
+ pgdat_resize_lock(pgdat, &flags);
+ if (!ms->usage) {
+ mask = 0;
+ } else if ((ms->usage->map_active & mask) != mask) {
+ WARN(1, "section already deactivated active: %#lx mask: %#lx\n",
+ ms->usage->map_active, mask);
+ mask = 0;
+ } else {
+ early_section = is_early_section(ms);
+ ms->usage->map_active ^= mask;
+ if (ms->usage->map_active == 0) {
+ usage = ms->usage;
+ ms->usage = NULL;
+ memmap = sparse_decode_mem_map(ms->section_mem_map,
+ section_nr);
+ ms->section_mem_map = 0;
+ }
+ }
+ pgdat_resize_unlock(pgdat, &flags);
+
+ /*
+ * 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
+ */
+ if (!mask)
+ return;
+ if (nr_pages < PAGES_PER_SECTION) {
+ if (!IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP)) {
+ WARN(1, "partial memory section removal not supported\n");
+ return;
+ }
+ if (!early_section)
+ depopulate_section_memmap(pfn, nr_pages);
+ memmap = 0;
+ }
+
+ if (usage) {
+ if (!early_section) {
+ /*
+ * 'memmap' may be zero in the SPARSEMEM_VMEMMAP=y case
+ * (see sparse_init_one_section()), so we can't rely on
+ * it to determine if we need to depopulate the memmap.
+ * Instead, we uncoditionally depopulate due to 'usage'
+ * being valid.
+ */
+ if (memmap || (nr_pages >= PAGES_PER_SECTION
+ && IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP)))
+ depopulate_section_memmap(pfn, nr_pages);
+ kfree(usage);
+ 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);
+}
+
+static struct page * __meminit section_activate(struct pglist_data *pgdat,
+ unsigned long pfn, unsigned nr_pages)
+{
+ struct mem_section *ms = __nr_to_section(pfn_to_section_nr(pfn));
+ unsigned long mask = section_active_mask(pfn, nr_pages), flags;
+ struct mem_section_usage *usage;
+ bool early_section = false;
+ struct page *memmap;
+ int rc = 0;
+
+ usage = __alloc_section_usage();
+ if (!usage)
+ return ERR_PTR(-ENOMEM);
+
+ pgdat_resize_lock(pgdat, &flags);
+ if (!ms->usage) {
+ ms->usage = usage;
+ usage = NULL;
+ } else
+ early_section = is_early_section(ms);
+
+ if (!mask)
+ rc = -EINVAL;
+ else if (mask & ms->usage->map_active)
+ rc = -EBUSY;
+ else
+ ms->usage->map_active |= mask;
+ pgdat_resize_unlock(pgdat, &flags);
+
+ kfree(usage);
+
+ if (rc)
+ 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)
+ return pfn_to_page(pfn);
+
+ memmap = populate_section_memmap(pfn, nr_pages, pgdat->node_id);
+ if (!memmap) {
+ section_deactivate(pgdat, pfn, nr_pages);
+ return ERR_PTR(-ENOMEM);
+ }
+
+ return memmap;
+}
+
+/**
+ * sparse_add_section() - create a new memmap section, or populate an
+ * existing one
+ * @zone: host zone for the new memory mapping
+ * @start_pfn: first pfn to add (section aligned if zone != ZONE_DEVICE)
+ * @nr_pages: number of new pages to add
+ *
+ * Returns 0 on success.
+ */
int __meminit sparse_add_section(struct zone *zone, unsigned long start_pfn,
unsigned long nr_pages)
{
unsigned long section_nr = pfn_to_section_nr(start_pfn);
struct pglist_data *pgdat = zone->zone_pgdat;
- static struct mem_section_usage *usage;
struct mem_section *ms;
struct page *memmap;
unsigned long flags;
@@ -771,37 +960,27 @@ int __meminit sparse_add_section(struct zone *zone, unsigned long start_pfn,
ret = sparse_index_init(section_nr, pgdat->node_id);
if (ret < 0 && ret != -EEXIST)
return ret;
- memmap = populate_section_memmap(start_pfn, PAGES_PER_SECTION,
- pgdat->node_id);
- if (!memmap)
- return -ENOMEM;
- usage = __alloc_section_usage();
- if (!usage) {
- depopulate_section_memmap(start_pfn, PAGES_PER_SECTION);
- return -ENOMEM;
- }
- pgdat_resize_lock(pgdat, &flags);
+ memmap = section_activate(pgdat, start_pfn, nr_pages);
+ if (IS_ERR(memmap))
+ return PTR_ERR(memmap);
+ pgdat_resize_lock(pgdat, &flags);
ms = __pfn_to_section(start_pfn);
- if (ms->section_mem_map & SECTION_MARKED_PRESENT) {
+ if (nr_pages == PAGES_PER_SECTION && (ms->section_mem_map
+ & SECTION_MARKED_PRESENT)) {
ret = -EBUSY;
goto out;
}
-
- memset(memmap, 0, sizeof(struct page) * PAGES_PER_SECTION);
-
ms->section_mem_map |= SECTION_MARKED_PRESENT;
-
- sparse_init_one_section(ms, section_nr, memmap, usage);
-
+ sparse_init_one_section(ms, section_nr, memmap, ms->usage);
out:
pgdat_resize_unlock(pgdat, &flags);
- if (ret < 0 && ret != -EEXIST) {
- kfree(usage);
- depopulate_section_memmap(start_pfn, PAGES_PER_SECTION);
+ if (nr_pages == PAGES_PER_SECTION && ret < 0 && ret != -EEXIST) {
+ section_deactivate(pgdat, start_pfn, nr_pages);
return ret;
}
+ memset(memmap, 0, sizeof(struct page) * nr_pages);
return 0;
}
@@ -827,58 +1006,15 @@ 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 page *usemap_page;
-
- if (!usage)
- return;
-
- usemap_page = virt_to_page(usage->pageblock_flags);
- /*
- * Check to see if allocation came from hot-plug-add
- */
- if (PageSlab(usemap_page) || PageCompound(usemap_page)) {
- kfree(usage);
- if (memmap)
- depopulate_section_memmap(pfn, nr_pages);
- 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)
{
- unsigned long flags;
- struct page *memmap = NULL;
- struct mem_section_usage *usage = NULL;
struct pglist_data *pgdat = zone->zone_pgdat;
- pgdat_resize_lock(pgdat, &flags);
- 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;
- }
- pgdat_resize_unlock(pgdat, &flags);
-
- 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);
+ clear_hwpoisoned_pages(pfn_to_page(pfn) + map_offset,
+ nr_pages - map_offset);
+ section_deactivate(pgdat, pfn, nr_pages);
}
#endif /* CONFIG_MEMORY_HOTREMOVE */
#endif /* CONFIG_MEMORY_HOTPLUG */
--
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