+ mm-memory_hotplug-allow-memmap-on-memory-hotplug-request-to-fallback.patch added to mm-unstable branch

+ mm-memory_hotplug-allow-memmap-on-memory-hotplug-request-to-fallback.patch added to mm-unstable branch

[Andrew Morton]

The patch titled
     Subject: mm/memory_hotplug: allow memmap on memory hotplug request to fallback
has been added to the -mm mm-unstable branch.  Its filename is
     mm-memory_hotplug-allow-memmap-on-memory-hotplug-request-to-fallback.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-memory_hotplug-allow-memmap-on-memory-hotplug-request-to-fallback.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Subject: mm/memory_hotplug: allow memmap on memory hotplug request to fallback
Date: Tue, 8 Aug 2023 14:44:57 +0530

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/20230808091501.287660-3-aneesh.kumar@linux.ibm.com
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 drivers/acpi/acpi_memhotplug.c |    3 +--
 include/linux/memory_hotplug.h |    3 ++-
 mm/memory_hotplug.c            |   13 ++++++-------
 3 files changed, 9 insertions(+), 10 deletions(-)

--- a/drivers/acpi/acpi_memhotplug.c~mm-memory_hotplug-allow-memmap-on-memory-hotplug-request-to-fallback
+++ a/drivers/acpi/acpi_memhotplug.c
@@ -211,8 +211,7 @@ static int acpi_memory_enable_device(str
 		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);
 
--- a/include/linux/memory_hotplug.h~mm-memory_hotplug-allow-memmap-on-memory-hotplug-request-to-fallback
+++ a/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(i
 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 */
--- a/mm/memory_hotplug.c~mm-memory_hotplug-allow-memmap-on-memory-hotplug-request-to-fallback
+++ a/mm/memory_hotplug.c
@@ -1247,7 +1247,7 @@ static int online_memory_block(struct me
 	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, s
 	 * 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 */
_

Patches currently in -mm which might be from aneesh.kumar@linux.ibm.com are

mm-hugepage-pud-allow-arch-specific-helper-function-to-check-huge-page-pud-support.patch
mm-hugepage-pud-allow-arch-specific-helper-function-to-check-huge-page-pud-support-fix.patch
mm-change-pudp_huge_get_and_clear_full-take-vm_area_struct-as-arg.patch
mm-vmemmap-improve-vmemmap_can_optimize-and-allow-architectures-to-override.patch
mm-vmemmap-allow-architectures-to-override-how-vmemmap-optimization-works.patch
mm-add-pud_same-similar-to-__have_arch_p4d_same.patch
mm-huge-pud-use-transparent-huge-pud-helpers-only-with-config_transparent_hugepage.patch
mm-vmemmap-optimization-split-hugetlb-and-devdax-vmemmap-optimization.patch
powerpc-mm-trace-convert-trace-event-to-trace-event-class.patch
powerpc-book3s64-mm-enable-transparent-pud-hugepage.patch
powerpc-book3s64-vmemmap-switch-radix-to-use-a-different-vmemmap-handling-function.patch
powerpc-book3s64-vmemmap-switch-radix-to-use-a-different-vmemmap-handling-function-fix.patch
powerpc-book3s64-vmemmap-switch-radix-to-use-a-different-vmemmap-handling-function-fix-2.patch
powerpc-book3s64-radix-add-support-for-vmemmap-optimization-for-radix.patch
powerpc-book3s64-radix-add-support-for-vmemmap-optimization-for-radix-fix.patch
powerpc-book3s64-radix-remove-mmu_vmemmap_psize.patch
powerpc-book3s64-radix-remove-mmu_vmemmap_psize-fix.patch
powerpc-book3s64-radix-add-debug-message-to-give-more-details-of-vmemmap-allocation.patch
mm-memory_hotplug-simplify-arch_mhp_memmap_on_memory_enable-kconfig.patch
mm-memory_hotplug-allow-memmap-on-memory-hotplug-request-to-fallback.patch
mm-memory_hotplug-allow-architecture-to-override-memmap-on-memory-support-check.patch
mm-memory_hotplug-support-memmap_on_memory-when-memmap-is-not-aligned-to-pageblocks.patch
powerpc-book3s64-memhotplug-enable-memmap-on-memory-for-radix.patch
mm-memory_hotplug-embed-vmem_altmap-details-in-memory-block.patch