Re: [PATCH 03/12] mm: page_alloc: move set_zone_contiguous() into mm_init.c

From: Kefeng Wang
Date: Mon May 08 2023 - 03:27:50 EST

On 2023/5/8 15:12, Huang, Ying wrote:
Kefeng Wang <> writes:

set_zone_contiguous() is only used in mm init/hotplug, and
clear_zone_contiguous() only used in hotplug, move them from
page_alloc.c to the more appropriate file.

Signed-off-by: Kefeng Wang <>
include/linux/memory_hotplug.h | 3 --
mm/internal.h | 7 +++
mm/mm_init.c | 74 +++++++++++++++++++++++++++++++
mm/page_alloc.c | 79 ----------------------------------
4 files changed, 81 insertions(+), 82 deletions(-)

+ * Check that the whole (or subset of) a pageblock given by the interval of
+ * [start_pfn, end_pfn) is valid and within the same zone, before scanning it
+ * with the migration of free compaction scanner.
+ *
+ * Return struct page pointer of start_pfn, or NULL if checks were not passed.
+ *
+ * It's possible on some configurations to have a setup like node0 node1 node0
+ * i.e. it's possible that all pages within a zones range of pages do not
+ * belong to a single zone. We assume that a border between node0 and node1
+ * can occur within a single pageblock, but not a node0 node1 node0
+ * interleaving within a single pageblock. It is therefore sufficient to check
+ * the first and last page of a pageblock and avoid checking each individual
+ * page in a pageblock.
+ *
+ * Note: the function may return non-NULL struct page even for a page block
+ * which contains a memory hole (i.e. there is no physical memory for a subset
+ * of the pfn range). For example, if the pageblock order is MAX_ORDER, which
+ * will fall into 2 sub-sections, and the end pfn of the pageblock may be hole
+ * even though the start pfn is online and valid. This should be safe most of
+ * the time because struct pages are still initialized via init_unavailable_range()
+ * and pfn walkers shouldn't touch any physical memory range for which they do
+ * not recognize any specific metadata in struct pages.
+ */
+struct page *__pageblock_pfn_to_page(unsigned long start_pfn,
+ unsigned long end_pfn, struct zone *zone)

__pageblock_pfn_to_page() is also called by compaction code too (e.g.,
isolate_freepages_range() -> pageblock_pfn_to_page() ->

So, it is used not only by initialization and hotplug?

I should drop the move of this function, thanks for your reminder.

Best Regards,
Huang, Ying