[PATCH v5 1/2] mm: allow optional initialization of page count and PG_reserved flag

[Yajun Deng <yajun.deng@linux.dev>]

__init_single_page() unconditionally resets page count which is
unnecessary for reserved pages.

To allow skipping page count initialization and marking a page reserved
in one go add flags parameter to __init_single_page().

No functional changes.

Signed-off-by: Yajun Deng <yajun.deng@linux.dev>
---
v5: change the subject and commit.
v4: remove the changes of __init_zone_device_page().
v3: Introduce enum init_page_flags.
v2: Introduce INIT_PAGE_COUNT and INIT_PAGE_RESERVED.
v1: https://lore.kernel.org/all/20230922070923.355656-1-yajun.deng@linux.dev/
---
 mm/hugetlb.c  |  2 +-
 mm/internal.h |  8 +++++++-
 mm/mm_init.c  | 24 +++++++++++++-----------
 3 files changed, 21 insertions(+), 13 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 32dbb4f82470..9c22297d9c57 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -3064,7 +3064,7 @@ static void __init hugetlb_folio_init_tail_vmemmap(struct folio *folio,
 	for (pfn = head_pfn + start_page_number; pfn < end_pfn; pfn++) {
 		struct page *page = pfn_to_page(pfn);
 
-		__init_single_page(page, pfn, zone, nid);
+		__init_single_page(page, pfn, zone, nid, INIT_PAGE_COUNT);
 		prep_compound_tail((struct page *)folio, pfn - head_pfn);
 		ret = page_ref_freeze(page, 1);
 		VM_BUG_ON(!ret);
diff --git a/mm/internal.h b/mm/internal.h
index d7916f1e9e98..536bbaa11be1 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -1209,8 +1209,14 @@ struct vma_prepare {
 	struct vm_area_struct *remove2;
 };
 
+enum page_init_flags {
+	INIT_PAGE_COUNT    = (1 << 0),
+	INIT_PAGE_RESERVED = (1 << 1),
+};
+
 void __meminit __init_single_page(struct page *page, unsigned long pfn,
-				unsigned long zone, int nid);
+				  unsigned long zone, int nid,
+				  enum page_init_flags flags);
 
 /* shrinker related functions */
 unsigned long shrink_slab(gfp_t gfp_mask, int nid, struct mem_cgroup *memcg,
diff --git a/mm/mm_init.c b/mm/mm_init.c
index 06a72c223bce..0549e7c3d588 100644
--- a/mm/mm_init.c
+++ b/mm/mm_init.c
@@ -557,11 +557,11 @@ static void __init find_zone_movable_pfns_for_nodes(void)
 }
 
 void __meminit __init_single_page(struct page *page, unsigned long pfn,
-				unsigned long zone, int nid)
+				  unsigned long zone, int nid,
+				  enum page_init_flags flags)
 {
 	mm_zero_struct_page(page);
 	set_page_links(page, zone, nid, pfn);
-	init_page_count(page);
 	page_mapcount_reset(page);
 	page_cpupid_reset_last(page);
 	page_kasan_tag_reset(page);
@@ -572,6 +572,10 @@ void __meminit __init_single_page(struct page *page, unsigned long pfn,
 	if (!is_highmem_idx(zone))
 		set_page_address(page, __va(pfn << PAGE_SHIFT));
 #endif
+	if (flags & INIT_PAGE_COUNT)
+		init_page_count(page);
+	if (flags & INIT_PAGE_RESERVED)
+		__SetPageReserved(page);
 }
 
 #ifdef CONFIG_NUMA
@@ -714,7 +718,7 @@ static void __meminit init_reserved_page(unsigned long pfn, int nid)
 		if (zone_spans_pfn(zone, pfn))
 			break;
 	}
-	__init_single_page(pfn_to_page(pfn), pfn, zid, nid);
+	__init_single_page(pfn_to_page(pfn), pfn, zid, nid, INIT_PAGE_COUNT);
 }
 #else
 static inline void pgdat_set_deferred_range(pg_data_t *pgdat) {}
@@ -821,8 +825,8 @@ static void __init init_unavailable_range(unsigned long spfn,
 			pfn = pageblock_end_pfn(pfn) - 1;
 			continue;
 		}
-		__init_single_page(pfn_to_page(pfn), pfn, zone, node);
-		__SetPageReserved(pfn_to_page(pfn));
+		__init_single_page(pfn_to_page(pfn), pfn, zone, node,
+				   INIT_PAGE_COUNT | INIT_PAGE_RESERVED);
 		pgcnt++;
 	}
 
@@ -884,7 +888,7 @@ void __meminit memmap_init_range(unsigned long size, int nid, unsigned long zone
 		}
 
 		page = pfn_to_page(pfn);
-		__init_single_page(page, pfn, zone, nid);
+		__init_single_page(page, pfn, zone, nid, INIT_PAGE_COUNT);
 		if (context == MEMINIT_HOTPLUG)
 			__SetPageReserved(page);
 
@@ -967,9 +971,6 @@ static void __ref __init_zone_device_page(struct page *page, unsigned long pfn,
 					  unsigned long zone_idx, int nid,
 					  struct dev_pagemap *pgmap)
 {
-
-	__init_single_page(page, pfn, zone_idx, nid);
-
 	/*
 	 * Mark page reserved as it will need to wait for onlining
 	 * phase for it to be fully associated with a zone.
@@ -977,7 +978,8 @@ static void __ref __init_zone_device_page(struct page *page, unsigned long pfn,
 	 * We can use the non-atomic __set_bit operation for setting
 	 * the flag as we are still initializing the pages.
 	 */
-	__SetPageReserved(page);
+	__init_single_page(page, pfn, zone_idx, nid,
+			   INIT_PAGE_COUNT | INIT_PAGE_RESERVED);
 
 	/*
 	 * ZONE_DEVICE pages union ->lru with a ->pgmap back pointer
@@ -2058,7 +2060,7 @@ static unsigned long  __init deferred_init_pages(struct zone *zone,
 		} else {
 			page++;
 		}
-		__init_single_page(page, pfn, zid, nid);
+		__init_single_page(page, pfn, zid, nid, INIT_PAGE_COUNT);
 		nr_pages++;
 	}
 	return (nr_pages);
-- 
2.25.1