[PATCH v20 8/9] mm: memory_hotplug: disable memmap_on_memory when hugetlb_free_vmemmap enabled

[Muchun Song]

The parameter of memory_hotplug.memmap_on_memory is not compatible with
hugetlb_free_vmemmap. So disable it when hugetlb_free_vmemmap is
enabled.

Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
---
 Documentation/admin-guide/kernel-parameters.txt |  4 ++++
 drivers/acpi/acpi_memhotplug.c                  |  1 +
 mm/memory_hotplug.c                             | 18 +++++++++++++-----
 3 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 9e655f5206ac..1f648b3e6120 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2893,6 +2893,10 @@
 			Note that even when enabled, there are a few cases where
 			the feature is not effective.
 
+			This is not compatible with hugetlb_free_vmemmap. If
+			both parameters are enabled, hugetlb_free_vmemmap takes
+			precedence over memory_hotplug.memmap_on_memory.
+
 	memtest=	[KNL,X86,ARM,PPC,RISCV] Enable memtest
 			Format: <integer>
 			default : 0 <disable>
diff --git a/drivers/acpi/acpi_memhotplug.c b/drivers/acpi/acpi_memhotplug.c
index 8cc195c4c861..0d7f595ee441 100644
--- a/drivers/acpi/acpi_memhotplug.c
+++ b/drivers/acpi/acpi_memhotplug.c
@@ -15,6 +15,7 @@
 #include <linux/acpi.h>
 #include <linux/memory.h>
 #include <linux/memory_hotplug.h>
+#include <linux/hugetlb.h>
 
 #include "internal.h"
 
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 68923c19bdea..c45ed6c0cd9f 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -981,6 +981,7 @@ static int online_memory_block(struct memory_block *mem, void *arg)
 
 bool mhp_supports_memmap_on_memory(unsigned long size)
 {
+	bool supported;
 	unsigned long nr_vmemmap_pages = size / PAGE_SIZE;
 	unsigned long vmemmap_size = nr_vmemmap_pages * sizeof(struct page);
 	unsigned long remaining_size = size - vmemmap_size;
@@ -1011,11 +1012,18 @@ bool mhp_supports_memmap_on_memory(unsigned long size)
 	 *	 altmap as an alternative source of memory, and we do not exactly
 	 *	 populate a single PMD.
 	 */
-	return memmap_on_memory &&
-	       IS_ENABLED(CONFIG_MHP_MEMMAP_ON_MEMORY) &&
-	       size == memory_block_size_bytes() &&
-	       IS_ALIGNED(vmemmap_size, PMD_SIZE) &&
-	       IS_ALIGNED(remaining_size, pageblock_nr_pages << PAGE_SHIFT);
+	supported = memmap_on_memory &&
+		    IS_ENABLED(CONFIG_MHP_MEMMAP_ON_MEMORY) &&
+		    size == memory_block_size_bytes() &&
+		    IS_ALIGNED(vmemmap_size, PMD_SIZE) &&
+		    IS_ALIGNED(remaining_size, pageblock_nr_pages << PAGE_SHIFT);
+
+	if (supported && is_hugetlb_free_vmemmap_enabled()) {
+		pr_info("Cannot enable memory_hotplug.memmap_on_memory, it is not compatible with hugetlb_free_vmemmap\n");
+		supported = false;
+	}
+
+	return supported;
 }
 
 /*
-- 
2.11.0