[RFC PATCH 2/3] mm: Implement for_each_valid_pfn() for CONFIG_FLATMEM

[David Woodhouse <dwmw2@infradead.org>]

From: David Woodhouse <dwmw@amazon.co.uk>

In the FLATMEM case, the default pfn_valid() just checks that the PFN is
within the range [ ARCH_PFN_OFFSET .. ARCH_PFN_OFFSET + max_mapnr ).

The for_each_valid_pfn() function can therefore be a simple for() loop
using those as min/max respectively.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
---
 include/asm-generic/memory_model.h | 26 +++++++++++++++++++++++++-
 1 file changed, 25 insertions(+), 1 deletion(-)

diff --git a/include/asm-generic/memory_model.h b/include/asm-generic/memory_model.h
index a3b5029aebbd..4fe7dd3bc09c 100644
--- a/include/asm-generic/memory_model.h
+++ b/include/asm-generic/memory_model.h
@@ -30,7 +30,31 @@ static inline int pfn_valid(unsigned long pfn)
 	return pfn >= pfn_offset && (pfn - pfn_offset) < max_mapnr;
 }
 #define pfn_valid pfn_valid
-#endif
+
+static inline bool first_valid_pfn(unsigned long *pfn)
+{
+	/* avoid <linux/mm.h> include hell */
+	extern unsigned long max_mapnr;
+	unsigned long pfn_offset = ARCH_PFN_OFFSET;
+
+	if (*pfn < pfn_offset) {
+		*pfn = pfn_offset;
+		return true;
+	}
+
+	if ((*pfn - pfn_offset) < max_mapnr)
+		return true;
+
+	return false;
+}
+
+#ifndef for_each_valid_pfn
+#define for_each_valid_pfn(pfn, start_pfn, end_pfn)			       \
+	for (pfn = max_t(unsigned long  start_pfn, ARCH_PFN_OFFSET);	       \
+	     pfn < min_t(unsigned long, end_pfn, ARCH_PFN_OFFSET + max_mapnr); \
+			 pfn++)
+#endif /* for_each_valid_pfn */
+#endif /* valid_pfn */
 
 #elif defined(CONFIG_SPARSEMEM_VMEMMAP)
 
-- 
2.49.0