mm: VM_flags comment fixes

Try to comment away a little of the confusion between mm's vm_area_struct
vm_flags and vmalloc's vm_struct flags: based on an idea by Ulrich Drepper.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/mm.h

diff --git a/include/linux/mm.h b/include/linux/mm.h
index fa65160..72a15dc 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -73,7 +73,7 @@
 #endif
 
 /*
- * vm_flags..
+ * vm_flags in vm_area_struct, see mm_types.h.
  */
 #define VM_READ		0x00000001	/* currently active flags */
 #define VM_WRITE	0x00000002

include/linux/mm_types.h

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 386edbe..bf33413 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -113,7 +113,7 @@
 	struct vm_area_struct *vm_next;
 
 	pgprot_t vm_page_prot;		/* Access permissions of this VMA. */
-	unsigned long vm_flags;		/* Flags, listed below. */
+	unsigned long vm_flags;		/* Flags, see mm.h. */
 
 	struct rb_node vm_rb;
 

include/linux/vmalloc.h

diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
index 364789a..328eb40 100644
--- a/include/linux/vmalloc.h
+++ b/include/linux/vmalloc.h
@@ -4,9 +4,9 @@
 #include <linux/spinlock.h>
 #include <asm/page.h>		/* pgprot_t */
 
-struct vm_area_struct;
+struct vm_area_struct;		/* vma defining user mapping in mm_types.h */
 
-/* bits in vm_struct->flags */
+/* bits in flags of vmalloc's vm_struct below */
 #define VM_IOREMAP	0x00000001	/* ioremap() and friends */
 #define VM_ALLOC	0x00000002	/* vmalloc() */
 #define VM_MAP		0x00000004	/* vmap()ed pages */