The patch titled
Subject: mm/memory_hotplug: move debug_pagealloc_map_pages() into online_pages_range()
has been added to the -mm mm-unstable branch. Its filename is
mm-memory_hotplug-move-debug_pagealloc_map_pages-into-online_pages_range.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-move-debug_pagealloc_map_pages-into-online_pages_range.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: David Hildenbrand <david@xxxxxxxxxx>
Subject: mm/memory_hotplug: move debug_pagealloc_map_pages() into online_pages_range()
Date: Tue, 3 Dec 2024 11:20:50 +0100
In the near future, we want to have a single way to handover PageOffline
pages to the buddy, whereby they could have:
(a) Never been exposed to the buddy before: kept PageOffline when onlining
the memory block.
(b) Been allocated from the buddy, for example using
alloc_contig_range() to then be set PageOffline,
Let's start by making generic_online_page() less special compared to
ordinary page freeing (e.g., free_contig_range()), and perform the
debug_pagealloc_map_pages() call unconditionally, even when the online
callback might decide to keep the pages offline.
All pages are already initialized with PageOffline, so nobody touches them
either way.
Link: https://lkml.kernel.org/r/20241203102050.223318-1-david@xxxxxxxxxx
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
Acked-by: Oscar Salvador <osalvador@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memory_hotplug.c | 10 +++++++++-
mm/page_alloc.c | 6 ------
2 files changed, 9 insertions(+), 7 deletions(-)
--- a/mm/memory_hotplug.c~mm-memory_hotplug-move-debug_pagealloc_map_pages-into-online_pages_range
+++ a/mm/memory_hotplug.c
@@ -650,6 +650,7 @@ static void online_pages_range(unsigned
* this and the first chunk to online will be pageblock_nr_pages.
*/
for (pfn = start_pfn; pfn < end_pfn;) {
+ struct page *page = pfn_to_page(pfn);
int order;
/*
@@ -664,7 +665,14 @@ static void online_pages_range(unsigned
else
order = MAX_PAGE_ORDER;
- (*online_page_callback)(pfn_to_page(pfn), order);
+ /*
+ * Exposing the page to the buddy by freeing can cause
+ * issues with debug_pagealloc enabled: some archs don't
+ * like double-unmappings. So treat them like any pages that
+ * were allocated from the buddy.
+ */
+ debug_pagealloc_map_pages(page, 1 << order);
+ (*online_page_callback)(page, order);
pfn += (1UL << order);
}
--- a/mm/page_alloc.c~mm-memory_hotplug-move-debug_pagealloc_map_pages-into-online_pages_range
+++ a/mm/page_alloc.c
@@ -1293,12 +1293,6 @@ void __meminit __free_pages_core(struct
set_page_count(p, 0);
}
- /*
- * Freeing the page with debug_pagealloc enabled will try to
- * unmap it; some archs don't like double-unmappings, so
- * map it first.
- */
- debug_pagealloc_map_pages(page, nr_pages);
adjust_managed_page_count(page, nr_pages);
} else {
for (loop = 0; loop < nr_pages; loop++, p++) {
_
Patches currently in -mm which might be from david@xxxxxxxxxx are
mm-mempolicy-fix-migrate_to_node-assuming-there-is-at-least-one-vma-in-a-mm.patch
mm-filemap-dont-call-folio_test_locked-without-a-reference-in-next_uptodate_folio.patch
docs-tmpfs-update-the-large-folios-policy-for-tmpfs-and-shmem.patch
mm-memory_hotplug-move-debug_pagealloc_map_pages-into-online_pages_range.patch
