[PATCH v2 1/3] x86/devmem: Remove duplicate range_is_allowed() definition

[Dan Williams]

It looks like x86 has a local re-implementation of range_is_allowed()
just to add a pat_enabled() check for the strong symbol override of
phys_mem_access_prot_allowed() from drivers/char/mem.c.

In preparation for updating range_is_allowed() logic, arrange for there
to be only one shared instance of "range_is_allowed()" in the kernel by
moving a common helper to include/linux/io.h.

Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
---
 arch/x86/mm/pat/memtype.c |   31 ++++---------------------------
 drivers/char/mem.c        |   18 ------------------
 include/linux/io.h        |   21 +++++++++++++++++++++
 3 files changed, 25 insertions(+), 45 deletions(-)

diff --git a/arch/x86/mm/pat/memtype.c b/arch/x86/mm/pat/memtype.c
index 72d8cbc61158..c97b6598f187 100644
--- a/arch/x86/mm/pat/memtype.c
+++ b/arch/x86/mm/pat/memtype.c
@@ -38,6 +38,7 @@
 #include <linux/kernel.h>
 #include <linux/pfn_t.h>
 #include <linux/slab.h>
+#include <linux/io.h>
 #include <linux/mm.h>
 #include <linux/highmem.h>
 #include <linux/fs.h>
@@ -773,38 +774,14 @@ pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
 	return vma_prot;
 }
 
-#ifdef CONFIG_STRICT_DEVMEM
-/* This check is done in drivers/char/mem.c in case of STRICT_DEVMEM */
-static inline int range_is_allowed(unsigned long pfn, unsigned long size)
-{
-	return 1;
-}
-#else
-/* This check is needed to avoid cache aliasing when PAT is enabled */
-static inline int range_is_allowed(unsigned long pfn, unsigned long size)
-{
-	u64 from = ((u64)pfn) << PAGE_SHIFT;
-	u64 to = from + size;
-	u64 cursor = from;
-
-	if (!pat_enabled())
-		return 1;
-
-	while (cursor < to) {
-		if (!devmem_is_allowed(pfn))
-			return 0;
-		cursor += PAGE_SIZE;
-		pfn++;
-	}
-	return 1;
-}
-#endif /* CONFIG_STRICT_DEVMEM */
-
 int phys_mem_access_prot_allowed(struct file *file, unsigned long pfn,
 				unsigned long size, pgprot_t *vma_prot)
 {
 	enum page_cache_mode pcm = _PAGE_CACHE_MODE_WB;
 
+	if (!pat_enabled())
+		return 1;
+
 	if (!range_is_allowed(pfn, size))
 		return 0;
 
diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index 169eed162a7f..48839958b0b1 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -61,29 +61,11 @@ static inline int page_is_allowed(unsigned long pfn)
 {
 	return devmem_is_allowed(pfn);
 }
-static inline int range_is_allowed(unsigned long pfn, unsigned long size)
-{
-	u64 from = ((u64)pfn) << PAGE_SHIFT;
-	u64 to = from + size;
-	u64 cursor = from;
-
-	while (cursor < to) {
-		if (!devmem_is_allowed(pfn))
-			return 0;
-		cursor += PAGE_SIZE;
-		pfn++;
-	}
-	return 1;
-}
 #else
 static inline int page_is_allowed(unsigned long pfn)
 {
 	return 1;
 }
-static inline int range_is_allowed(unsigned long pfn, unsigned long size)
-{
-	return 1;
-}
 #endif
 
 static inline bool should_stop_iteration(void)
diff --git a/include/linux/io.h b/include/linux/io.h
index 6a6bc4d46d0a..0642c7ee41db 100644
--- a/include/linux/io.h
+++ b/include/linux/io.h
@@ -183,4 +183,25 @@ static inline void arch_io_free_memtype_wc(resource_size_t base,
 int devm_arch_io_reserve_memtype_wc(struct device *dev, resource_size_t start,
 				    resource_size_t size);
 
+#ifdef CONFIG_STRICT_DEVMEM
+static inline int range_is_allowed(unsigned long pfn, unsigned long size)
+{
+	u64 from = ((u64)pfn) << PAGE_SHIFT;
+	u64 to = from + size;
+	u64 cursor = from;
+
+	while (cursor < to) {
+		if (!devmem_is_allowed(pfn))
+			return 0;
+		cursor += PAGE_SIZE;
+		pfn++;
+	}
+	return 1;
+}
+#else
+static inline int range_is_allowed(unsigned long pfn, unsigned long size)
+{
+	return 1;
+}
+#endif
 #endif /* _LINUX_IO_H */