[RFC PATCH] mm: Add a new page type to mark unavailable pages

[Baoquan He]

Firstly, the last user of early_pfn_valid() is memmap_init_zone(), but that code
has been optimized away. Let's remove it.

Secondly, add a new page type to mark unavailale pages.

Thirdly, add a new early_pfn_valid() so that init_unavailable_range()
can initialize those pages in memblock.reserved.

Signed-off-by: Baoquan He <bhe@xxxxxxxxxx>
---
 arch/x86/include/asm/mmzone_32.h |  2 --
 include/linux/mmzone.h           | 18 ++++++++++--------
 include/linux/page-flags.h       |  8 ++++++++
 mm/page_alloc.c                  |  3 ++-
 4 files changed, 20 insertions(+), 11 deletions(-)

diff --git a/arch/x86/include/asm/mmzone_32.h b/arch/x86/include/asm/mmzone_32.h
index 73d8dd14dda2..4da45eff2942 100644
--- a/arch/x86/include/asm/mmzone_32.h
+++ b/arch/x86/include/asm/mmzone_32.h
@@ -49,8 +49,6 @@ static inline int pfn_valid(int pfn)
 	return 0;
 }
 
-#define early_pfn_valid(pfn)	pfn_valid((pfn))
-
 #endif /* CONFIG_DISCONTIGMEM */
 
 #endif /* _ASM_X86_MMZONE_32_H */
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index e8d7d0b0acf4..47d09be73dca 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -1315,20 +1315,23 @@ static inline int pfn_section_valid(struct mem_section *ms, unsigned long pfn)
 #endif
 
 #ifndef CONFIG_HAVE_ARCH_PFN_VALID
-static inline int pfn_valid(unsigned long pfn)
+static inline int early_pfn_valid(unsigned long pfn)
 {
-	struct mem_section *ms;
-
 	if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS)
 		return 0;
-	ms = __nr_to_section(pfn_to_section_nr(pfn));
-	if (!valid_section(ms))
+	return valid_section(__pfn_to_section(pfn))
+}
+
+static inline int pfn_valid(unsigned long pfn)
+{
+	if (!early_pfn_valid(pfn))
 		return 0;
 	/*
 	 * Traditionally early sections always returned pfn_valid() for
 	 * the entire section-sized span.
 	 */
-	return early_section(ms) || pfn_section_valid(ms, pfn);
+	return (early_section(ms) && PageUnavail(pfn_to_page(pfn))) ||
+	       pfn_section_valid(ms, pfn);
 }
 #endif
 
@@ -1364,7 +1367,6 @@ static inline unsigned long next_present_section_nr(unsigned long section_nr)
 #define pfn_to_nid(pfn)		(0)
 #endif
 
-#define early_pfn_valid(pfn)	pfn_valid(pfn)
 void sparse_init(void);
 #else
 #define sparse_init()	do {} while (0)
@@ -1385,7 +1387,7 @@ struct mminit_pfnnid_cache {
 };
 
 #ifndef early_pfn_valid
-#define early_pfn_valid(pfn)	(1)
+#define early_pfn_valid(pfn)	pfn_valid(pfn)
 #endif
 
 void memory_present(int nid, unsigned long start, unsigned long end);
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 222f6f7b2bb3..1c011008100c 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -740,6 +740,7 @@ PAGEFLAG_FALSE(DoubleMap)
 #define PG_kmemcg	0x00000200
 #define PG_table	0x00000400
 #define PG_guard	0x00000800
+#define PG_unavail	0x00001000
 
 #define PageType(page, flag)						\
 	((page->page_type & (PAGE_TYPE_BASE | flag)) == PAGE_TYPE_BASE)
@@ -796,6 +797,13 @@ PAGE_TYPE_OPS(Table, table)
  */
 PAGE_TYPE_OPS(Guard, guard)
 
+/*
+ *  Mark pages which are unavailable to memory allocators after boot.
+ *  They includes pages reserved by firmware pre-boot or during boot,
+ *  holes which share the same setcion with usable RAM.
+ */
+PAGE_TYPE_OPS(Unavail, unavail)
+
 extern bool is_free_buddy_page(struct page *page);
 
 __PAGEFLAG(Isolated, isolated, PF_ANY);
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 940cdce96864..e9ebef6ffbec 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -6972,7 +6972,8 @@ static u64 __init init_unavailable_range(unsigned long spfn, unsigned long epfn)
 		 * (in memblock.reserved but not in memblock.memory) will
 		 * get re-initialized via reserve_bootmem_region() later.
 		 */
-		__init_single_page(pfn_to_page(pfn), pfn, 0, 0);
+		mm_zero_struct_page(pfn_to_page(pfn));
+		__SetPageUnavail(pfn_to_page(pfn));
 		__SetPageReserved(pfn_to_page(pfn));
 		pgcnt++;
 	}
-- 
2.17.2