mm/memory_hotplug: allow memmap on memory hotplug request to fallback

If not supported, fallback to not using memap on memmory. This avoids the need for callers to do the fallback. Link: https://lkml.kernel.org/r/[email protected] Signed-off-by: Aneesh Kumar K.V <[email protected]> Acked-by: Michal Hocko <[email protected]> Acked-by: David Hildenbrand <[email protected]> Cc: Christophe Leroy <[email protected]> Cc: Michael Ellerman <[email protected]> Cc: Nicholas Piggin <[email protected]> Cc: Oscar Salvador <[email protected]> Cc: Vishal Verma <[email protected]> Signed-off-by: Andrew Morton <[email protected]>
torvalds · Aug 21, 2023 · e3c2bfd · e3c2bfd
1 parent 04d5ea4
commit e3c2bfd
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Showing 3 changed files with 9 additions and 10 deletions.
diff --git a/drivers/acpi/acpi_memhotplug.c b/drivers/acpi/acpi_memhotplug.c
@@ -211,8 +211,7 @@ static int acpi_memory_enable_device(struct acpi_memory_device *mem_device)
  if (!info->length)
  continue;
 
- if (mhp_supports_memmap_on_memory(info->length))
- mhp_flags |= MHP_MEMMAP_ON_MEMORY;
+ mhp_flags |= MHP_MEMMAP_ON_MEMORY;
  result = __add_memory(mgid, info->start_addr, info->length,
  mhp_flags);
 

diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
@@ -97,6 +97,8 @@ typedef int __bitwise mhp_t;
  * To do so, we will use the beginning of the hot-added range to build
  * the page tables for the memmap array that describes the entire range.
  * Only selected architectures support it with SPARSE_VMEMMAP.
+ * This is only a hint, the core kernel can decide to not do this based on
+ * different alignment checks.
  */
 #define MHP_MEMMAP_ON_MEMORY ((__force mhp_t)BIT(1))
 /*
@@ -354,7 +356,6 @@ extern struct zone *zone_for_pfn_range(int online_type, int nid,
 extern int arch_create_linear_mapping(int nid, u64 start, u64 size,
  struct mhp_params *params);
 void arch_remove_linear_mapping(u64 start, u64 size);
-extern bool mhp_supports_memmap_on_memory(unsigned long size);
 #endif /* CONFIG_MEMORY_HOTPLUG */
 
 #endif /* __LINUX_MEMORY_HOTPLUG_H */
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
@@ -1247,7 +1247,7 @@ static int online_memory_block(struct memory_block *mem, void *arg)
  return device_online(&mem->dev);
 }
 
-bool mhp_supports_memmap_on_memory(unsigned long size)
+static bool mhp_supports_memmap_on_memory(unsigned long size)
 {
  unsigned long nr_vmemmap_pages = size / PAGE_SIZE;
  unsigned long vmemmap_size = nr_vmemmap_pages * sizeof(struct page);
@@ -1339,13 +1339,12 @@ int __ref add_memory_resource(int nid, struct resource *res, mhp_t mhp_flags)
  * Self hosted memmap array
  */
  if (mhp_flags & MHP_MEMMAP_ON_MEMORY) {
- if (!mhp_supports_memmap_on_memory(size)) {
- ret = -EINVAL;
- goto error;
+ if (mhp_supports_memmap_on_memory(size)) {
+ mhp_altmap.free = PHYS_PFN(size);
+ mhp_altmap.base_pfn = PHYS_PFN(start);
+ params.altmap = &mhp_altmap;
  }
- mhp_altmap.free = PHYS_PFN(size);
- mhp_altmap.base_pfn = PHYS_PFN(start);
- params.altmap = &mhp_altmap;
+ /* fallback to not using altmap */
  }
 
  /* call arch's memory hotadd */