The patch titled
Subject: mm/memory_hotplug: export mhp_supports_memmap_on_memory()
has been added to the -mm mm-unstable branch. Its filename is
mm-memory_hotplug-export-mhp_supports_memmap_on_memory.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-export-mhp_supports_memmap_on_memory.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: Vishal Verma <vishal.l.verma@xxxxxxxxx>
Subject: mm/memory_hotplug: export mhp_supports_memmap_on_memory()
Date: Wed, 24 Jan 2024 12:03:49 -0800
In preparation for adding sysfs ABI to toggle memmap_on_memory semantics
for drivers adding memory, export the mhp_supports_memmap_on_memory()
helper. This allows drivers to check if memmap_on_memory support is
available before trying to request it, and display an appropriate
message if it isn't available. As part of this, remove the size argument
to this - with recent updates to allow memmap_on_memory for larger
ranges, and the internal splitting of altmaps into respective memory
blocks, the size argument is meaningless.
Link: https://lkml.kernel.org/r/20240124-vv-dax_abi-v7-4-20d16cb8d23d@xxxxxxxxx
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Dave Jiang <dave.jiang@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Huang Ying <ying.huang@xxxxxxxxx>
Suggested-by: David Hildenbrand <david@xxxxxxxxxx>
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
Signed-off-by: Vishal Verma <vishal.l.verma@xxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
Cc: Li Zhijian <lizhijian@xxxxxxxxxxx>
Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: <nvdimm@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/memory_hotplug.h | 6 ++++++
mm/memory_hotplug.c | 17 ++++++-----------
2 files changed, 12 insertions(+), 11 deletions(-)
--- a/include/linux/memory_hotplug.h~mm-memory_hotplug-export-mhp_supports_memmap_on_memory
+++ a/include/linux/memory_hotplug.h
@@ -137,6 +137,7 @@ struct mhp_params {
bool mhp_range_allowed(u64 start, u64 size, bool need_mapping);
struct range mhp_get_pluggable_range(bool need_mapping);
+bool mhp_supports_memmap_on_memory(void);
/*
* Zone resizing functions
@@ -277,6 +278,11 @@ static inline bool movable_node_is_enabl
{
return false;
}
+
+static bool mhp_supports_memmap_on_memory(void)
+{
+ return false;
+}
static inline void pgdat_kswapd_lock(pg_data_t *pgdat) {}
static inline void pgdat_kswapd_unlock(pg_data_t *pgdat) {}
--- a/mm/memory_hotplug.c~mm-memory_hotplug-export-mhp_supports_memmap_on_memory
+++ a/mm/memory_hotplug.c
@@ -1337,7 +1337,7 @@ static inline bool arch_supports_memmap_
}
#endif
-static bool mhp_supports_memmap_on_memory(unsigned long size)
+bool mhp_supports_memmap_on_memory(void)
{
unsigned long vmemmap_size = memory_block_memmap_size();
unsigned long memmap_pages = memory_block_memmap_on_memory_pages();
@@ -1346,17 +1346,11 @@ static bool mhp_supports_memmap_on_memor
* Besides having arch support and the feature enabled at runtime, we
* need a few more assumptions to hold true:
*
- * a) We span a single memory block: memory onlining/offlinin;g happens
- * in memory block granularity. We don't want the vmemmap of online
- * memory blocks to reside on offline memory blocks. In the future,
- * we might want to support variable-sized memory blocks to make the
- * feature more versatile.
- *
- * b) The vmemmap pages span complete PMDs: We don't want vmemmap code
+ * a) The vmemmap pages span complete PMDs: We don't want vmemmap code
* to populate memory from the altmap for unrelated parts (i.e.,
* other memory blocks)
*
- * c) The vmemmap pages (and thereby the pages that will be exposed to
+ * b) The vmemmap pages (and thereby the pages that will be exposed to
* the buddy) have to cover full pageblocks: memory onlining/offlining
* code requires applicable ranges to be page-aligned, for example, to
* set the migratetypes properly.
@@ -1368,7 +1362,7 @@ static bool mhp_supports_memmap_on_memor
* altmap as an alternative source of memory, and we do not exactly
* populate a single PMD.
*/
- if (!mhp_memmap_on_memory() || size != memory_block_size_bytes())
+ if (!mhp_memmap_on_memory())
return false;
/*
@@ -1391,6 +1385,7 @@ static bool mhp_supports_memmap_on_memor
return arch_supports_memmap_on_memory(vmemmap_size);
}
+EXPORT_SYMBOL_GPL(mhp_supports_memmap_on_memory);
static void __ref remove_memory_blocks_and_altmaps(u64 start, u64 size)
{
@@ -1526,7 +1521,7 @@ int __ref add_memory_resource(int nid, s
* Self hosted memmap array
*/
if ((mhp_flags & MHP_MEMMAP_ON_MEMORY) &&
- mhp_supports_memmap_on_memory(memory_block_size_bytes())) {
+ mhp_supports_memmap_on_memory()) {
ret = create_altmaps_and_memory_blocks(nid, group, start, size, mhp_flags);
if (ret)
goto error;
_
Patches currently in -mm which might be from vishal.l.verma@xxxxxxxxx are
dax-busc-replace-driver-core-lock-usage-by-a-local-rwsem.patch
dax-busc-replace-several-sprintf-with-sysfs_emit.patch
documentatiion-abi-add-abi-documentation-for-sys-bus-dax.patch
mm-memory_hotplug-export-mhp_supports_memmap_on_memory.patch
dax-add-a-sysfs-knob-to-control-memmap_on_memory-behavior.patch
