[PATCH v2 1/5] mm: page_alloc: remain memblock_next_valid_pfn() when CONFIG_HAVE_ARCH_PFN_VALID is enable

[Jia He]

Commit b92df1de5d28 ("mm: page_alloc: skip over regions of invalid pfns
where possible") optimized the loop in memmap_init_zone(). But it causes
possible panic bug. So Daniel Vacek reverted it later.

But memblock_next_valid_pfn is valid when CONFIG_HAVE_ARCH_PFN_VALID is
enabled. And as verified by Eugeniu Rosca, arm can benifit from this
commit. So remain the memblock_next_valid_pfn.

Signed-off-by: Jia He <jia.he@xxxxxxxxxxxxxxxx>
---
 include/linux/memblock.h |  4 ++++
 mm/memblock.c            | 29 +++++++++++++++++++++++++++++
 mm/page_alloc.c          | 11 ++++++++++-
 3 files changed, 43 insertions(+), 1 deletion(-)

diff --git a/include/linux/memblock.h b/include/linux/memblock.h
index 0257aee..efbbe4b 100644
--- a/include/linux/memblock.h
+++ b/include/linux/memblock.h
@@ -203,6 +203,10 @@ void __next_mem_pfn_range(int *idx, int nid, unsigned long *out_start_pfn,
 	     i >= 0; __next_mem_pfn_range(&i, nid, p_start, p_end, p_nid))
 #endif /* CONFIG_HAVE_MEMBLOCK_NODE_MAP */
 
+#ifdef CONFIG_HAVE_ARCH_PFN_VALID
+unsigned long memblock_next_valid_pfn(unsigned long pfn);
+#endif
+
 /**
  * for_each_free_mem_range - iterate through free memblock areas
  * @i: u64 used as loop variable
diff --git a/mm/memblock.c b/mm/memblock.c
index ba7c878..bea5a9c 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -1102,6 +1102,35 @@ void __init_memblock __next_mem_pfn_range(int *idx, int nid,
 		*out_nid = r->nid;
 }
 
+#ifdef CONFIG_HAVE_ARCH_PFN_VALID
+unsigned long __init_memblock memblock_next_valid_pfn(unsigned long pfn)
+{
+	struct memblock_type *type = &memblock.memory;
+	unsigned int right = type->cnt;
+	unsigned int mid, left = 0;
+	phys_addr_t addr = PFN_PHYS(++pfn);
+
+	do {
+		mid = (right + left) / 2;
+
+		if (addr < type->regions[mid].base)
+			right = mid;
+		else if (addr >= (type->regions[mid].base +
+				  type->regions[mid].size))
+			left = mid + 1;
+		else {
+			/* addr is within the region, so pfn is valid */
+			return pfn;
+		}
+	} while (left < right);
+
+	if (right == type->cnt)
+		return -1UL;
+	else
+		return PHYS_PFN(type->regions[right].base);
+}
+#endif /*CONFIG_HAVE_ARCH_PFN_VALID*/
+
 /**
  * memblock_set_node - set node ID on memblock regions
  * @base: base of area to set node ID for
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index c19f5ac..2a967f7 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5483,8 +5483,17 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
 		if (context != MEMMAP_EARLY)
 			goto not_early;
 
-		if (!early_pfn_valid(pfn))
+		if (!early_pfn_valid(pfn)) {
+#if (defined CONFIG_HAVE_MEMBLOCK) && (defined CONFIG_HAVE_ARCH_PFN_VALID)
+			/*
+			 * Skip to the pfn preceding the next valid one (or
+			 * end_pfn), such that we hit a valid pfn (or end_pfn)
+			 * on our next iteration of the loop.
+			 */
+			pfn = memblock_next_valid_pfn(pfn) - 1;
+#endif
 			continue;
+		}
 		if (!early_pfn_in_nid(pfn, nid))
 			continue;
 		if (!update_defer_init(pgdat, pfn, end_pfn, &nr_initialised))
-- 
2.7.4