mm: re-architect the VM_UNPAGED logic

This replaces the (in my opinion horrible) VM_UNMAPPED logic with very
explicit support for a "remapped page range" aka VM_PFNMAP.  It allows a
VM area to contain an arbitrary range of page table entries that the VM
never touches, and never considers to be normal pages.

Any user of "remap_pfn_range()" automatically gets this new
functionality, and doesn't even have to mark the pages reserved or
indeed mark them any other way.  It just works.  As a side effect, doing
mmap() on /dev/mem works for arbitrary ranges.

Sparc update from David in the next commit.

Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 3 insertions, 2 deletions

diff --git a/include/linux/mm.h b/include/linux/mm.h
index f0cdfd18db55..6a75a7a78bf1 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -145,7 +145,7 @@ extern unsigned int kobjsize(const void *objp);
 #define VM_GROWSDOWN    0x00000100      /* general info on the segment */
 #define VM_GROWSUP      0x00000200
 #define VM_SHM          0x00000000      /* Means nothing: delete it later */
-#define VM_UNPAGED      0x00000400      /* Pages managed without map count */
+#define VM_PFNMAP       0x00000400      /* Page-ranges managed without "struct page", just pure PFN */
 #define VM_DENYWRITE    0x00000800      /* ETXTBSY on write attempts.. */
 
 #define VM_EXECUTABLE   0x00001000
@@ -664,6 +664,7 @@ struct zap_details {
         unsigned long truncate_count;           /* Compare vm_truncate_count */
 };
 
+struct page *vm_normal_page(struct vm_area_struct *, unsigned long, pte_t);
 unsigned long zap_page_range(struct vm_area_struct *vma, unsigned long address,
                 unsigned long size, struct zap_details *);
 unsigned long unmap_vmas(struct mmu_gather **tlb,
@@ -953,7 +954,7 @@ unsigned long vmalloc_to_pfn(void *addr);
 int remap_pfn_range(struct vm_area_struct *, unsigned long addr,
                         unsigned long pfn, unsigned long size, pgprot_t);
 
-struct page *follow_page(struct mm_struct *, unsigned long address,
+struct page *follow_page(struct vm_area_struct *, unsigned long address,
                         unsigned int foll_flags);
 #define FOLL_WRITE      0x01    /* check pte is writable */
 #define FOLL_TOUCH      0x02    /* mark page accessed */