[PATCH v3 3/3] mm: use vmem_altmap code without CONFIG_ZONE_DEVICE

From: Sumanth Korikkar
Date: Mon Nov 20 2023 - 09:55:11 EST


vmem_altmap_free() and vmem_altmap_offset() could be utlized without
CONFIG_ZONE_DEVICE enabled. For example,
mm/memory_hotplug.c:__add_pages() relies on that. The altmap is no
longer restricted to ZONE_DEVICE handling, but instead depends on
CONFIG_SPARSEMEM_VMEMMAP.

When CONFIG_SPARSEMEM_VMEMMAP is disabled, these functions are defined
as inline stubs, ensuring compatibility with configurations that do not
use sparsemem vmemmap. Without it, lkp reported the following:

ld: arch/x86/mm/init_64.o: in function `remove_pagetable':
init_64.c:(.meminit.text+0xfc7): undefined reference to
`vmem_altmap_free'

Reported-by: kernel test robot <lkp@xxxxxxxxx>
Closes: https://lore.kernel.org/oe-kbuild-all/202311180545.VeyRXEDq-lkp@xxxxxxxxx/
Reviewed-by: Gerald Schaefer <gerald.schaefer@xxxxxxxxxxxxx>
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
Signed-off-by: Sumanth Korikkar <sumanthk@xxxxxxxxxxxxx>
---
include/linux/memremap.h | 12 ------------
include/linux/mm.h | 26 ++++++++++++++++++++++++++
mm/memremap.c | 14 +-------------
3 files changed, 27 insertions(+), 25 deletions(-)

diff --git a/include/linux/memremap.h b/include/linux/memremap.h
index 1314d9c5f05b..744c830f4b13 100644
--- a/include/linux/memremap.h
+++ b/include/linux/memremap.h
@@ -196,8 +196,6 @@ struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
struct dev_pagemap *pgmap);
bool pgmap_pfn_valid(struct dev_pagemap *pgmap, unsigned long pfn);

-unsigned long vmem_altmap_offset(struct vmem_altmap *altmap);
-void vmem_altmap_free(struct vmem_altmap *altmap, unsigned long nr_pfns);
unsigned long memremap_compat_align(void);
#else
static inline void *devm_memremap_pages(struct device *dev,
@@ -228,16 +226,6 @@ static inline bool pgmap_pfn_valid(struct dev_pagemap *pgmap, unsigned long pfn)
return false;
}

-static inline unsigned long vmem_altmap_offset(struct vmem_altmap *altmap)
-{
- return 0;
-}
-
-static inline void vmem_altmap_free(struct vmem_altmap *altmap,
- unsigned long nr_pfns)
-{
-}
-
/* when memremap_pages() is disabled all archs can remap a single page */
static inline unsigned long memremap_compat_align(void)
{
diff --git a/include/linux/mm.h b/include/linux/mm.h
index bf5d0b1b16f4..f2344fd8acbe 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -3786,6 +3786,32 @@ void vmemmap_free(unsigned long start, unsigned long end,
struct vmem_altmap *altmap);
#endif

+#ifdef CONFIG_SPARSEMEM_VMEMMAP
+static inline unsigned long vmem_altmap_offset(struct vmem_altmap *altmap)
+{
+ /* number of pfns from base where pfn_to_page() is valid */
+ if (altmap)
+ return altmap->reserve + altmap->free;
+ return 0;
+}
+
+static inline void vmem_altmap_free(struct vmem_altmap *altmap,
+ unsigned long nr_pfns)
+{
+ altmap->alloc -= nr_pfns;
+}
+#else
+static inline unsigned long vmem_altmap_offset(struct vmem_altmap *altmap)
+{
+ return 0;
+}
+
+static inline void vmem_altmap_free(struct vmem_altmap *altmap,
+ unsigned long nr_pfns)
+{
+}
+#endif
+
#define VMEMMAP_RESERVE_NR 2
#ifdef CONFIG_ARCH_WANT_OPTIMIZE_DAX_VMEMMAP
static inline bool __vmemmap_can_optimize(struct vmem_altmap *altmap,
diff --git a/mm/memremap.c b/mm/memremap.c
index bee85560a243..9531faa92a7c 100644
--- a/mm/memremap.c
+++ b/mm/memremap.c
@@ -7,6 +7,7 @@
#include <linux/memremap.h>
#include <linux/pfn_t.h>
#include <linux/swap.h>
+#include <linux/mm.h>
#include <linux/mmzone.h>
#include <linux/swapops.h>
#include <linux/types.h>
@@ -422,19 +423,6 @@ void devm_memunmap_pages(struct device *dev, struct dev_pagemap *pgmap)
}
EXPORT_SYMBOL_GPL(devm_memunmap_pages);

-unsigned long vmem_altmap_offset(struct vmem_altmap *altmap)
-{
- /* number of pfns from base where pfn_to_page() is valid */
- if (altmap)
- return altmap->reserve + altmap->free;
- return 0;
-}
-
-void vmem_altmap_free(struct vmem_altmap *altmap, unsigned long nr_pfns)
-{
- altmap->alloc -= nr_pfns;
-}
-
/**
* get_dev_pagemap() - take a new live reference on the dev_pagemap for @pfn
* @pfn: page frame number to lookup page_map
--
2.41.0