On 02.06.21 13:10, Max Gurtovoy wrote:
Hotplugged memory has alignmet restrictions. E.g, it disallows all
operations smaller than a sub-section and only allow operations smaller
than a section for SPARSEMEM_VMEMMAP. Export the alignment restrictions
for mhp users.
Signed-off-by: Max Gurtovoy <mgurtovoy@xxxxxxxxxx>
---
include/linux/memory_hotplug.h | 5 +++++
mm/memory_hotplug.c | 33 +++++++++++++++++++--------------
2 files changed, 24 insertions(+), 14 deletions(-)
diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index 28f32fd00fe9..c55a9049b11e 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -76,6 +76,7 @@ struct mhp_params {
bool mhp_range_allowed(u64 start, u64 size, bool need_mapping);
struct range mhp_get_pluggable_range(bool need_mapping);
+unsigned long mhp_get_min_align(void);
/*
* Zone resizing functions
@@ -248,6 +249,10 @@ void mem_hotplug_done(void);
___page; \
})
+static inline unsigned long mhp_get_min_align(void)
+{
+ return 0;
+}
static inline unsigned zone_span_seqbegin(struct zone *zone)
{
return 0;
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 9e86e9ee0a10..161bb6704a9b 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -270,24 +270,29 @@ void __init register_page_bootmem_info_node(struct pglist_data *pgdat)
}
#endif /* CONFIG_HAVE_BOOTMEM_INFO_NODE */
+/*
+ * Disallow all operations smaller than a sub-section and only
+ * allow operations smaller than a section for
+ * SPARSEMEM_VMEMMAP. Note that check_hotplug_memory_range()
+ * enforces a larger memory_block_size_bytes() granularity for
+ * memory that will be marked online, so this check should only
+ * fire for direct arch_{add,remove}_memory() users outside of
+ * add_memory_resource().
+ */
+unsigned long mhp_get_min_align(void)
+{
+ if (IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP))
+ return PAGES_PER_SUBSECTION;
+ return PAGES_PER_SECTION;
+}
+EXPORT_SYMBOL_GPL(mhp_get_min_align);
We have to main interfaces to "hotplug" memory:
a) add_memory() and friends for System RAM, which have memory block
alignment requirements.
b) memremap_pages(), which has the alignemnt requirements you mention here.
I feel like what you need would better be exposed in mm/memremap.c, for
example, via "memremap_min_alignment" so it matches the "memremap_pages"
semantics.
And then, memremap_pages() is only available with CONFIG_ZONE_DEVICE,
which depends on SPARSEMEM_VMEMMAP. So you'll always have
PAGES_PER_SUBSECTION.
I can already spot "memremap_compat_align", maybe you can reuse that or
handle it accordingly in there?
--
Thanks,
David / dhildenb
