[PATCH v6 2/7] mm/memory_hotplug: Allow memmap on memory hotplug request to fallback

[Aneesh Kumar K.V]

If not supported, fallback to not using memap on memmory. This avoids
the need for callers to do the fallback.

Acked-by: David Hildenbrand <da...@redhat.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.ku...@linux.ibm.com>
---
 drivers/acpi/acpi_memhotplug.c |  3 +--
 include/linux/memory_hotplug.h |  3 ++-
 mm/memory_hotplug.c            | 13 ++++++-------
 3 files changed, 9 insertions(+), 10 deletions(-)

diff --git a/drivers/acpi/acpi_memhotplug.c b/drivers/acpi/acpi_memhotplug.c
index 24f662d8bd39..d0c1a71007d0 100644
--- 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
index 013c69753c91..7d2076583494 100644
--- 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
index 7cfd13c91568..eca32ccd45cc 100644
--- 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 */
-- 
2.41.0