[PATCH v1: vfio: avoid unnecessary pin memory when dma map io address space 1/2] mm: introduce vma flag VM_PGOFF_IS_PFN

[Qinyun Tan <qinyuntan@linux.alibaba.com>]

Introduce a new vma flag 'VM_PGOFF_IS_PFN', which means
vma->vm_pgoff == pfn. This allows us to directly obtain pfn
through vma->vm_pgoff. No Functional Change.

Signed-off-by: Qinyun Tan <qinyuntan@linux.alibaba.com>
Reviewed-by: Guanghui Feng <guanghuifeng@linux.alibaba.com>
Reviewed-by: Xunlei Pang <xlpang@linux.alibaba.com>
---
 include/linux/mm.h | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index ecf63d2b05825..80849b1b9aa92 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -322,6 +322,12 @@ extern unsigned int kobjsize(const void *objp);
 #define VM_NOHUGEPAGE	0x40000000	/* MADV_NOHUGEPAGE marked this vma */
 #define VM_MERGEABLE	0x80000000	/* KSM may merge identical pages */
 
+#ifdef CONFIG_ARCH_USES_HIGH_VMA_FLAGS	/* vma->vm_pgoff == pfn */
+    #define VM_PGOFF_IS_PFN   BIT(62)
+#else
+    #define VM_PGOFF_IS_PFN   VM_NONE
+#endif
+
 #ifdef CONFIG_ARCH_USES_HIGH_VMA_FLAGS
 #define VM_HIGH_ARCH_BIT_0	32	/* bit only usable on 64-bit architectures */
 #define VM_HIGH_ARCH_BIT_1	33	/* bit only usable on 64-bit architectures */
-- 
2.43.5