Make sure we copy pages inserted with "vm_insert_page()" on fork

The logic that decides that a fork() might be able to avoid copying a VM
area when it can be re-created by page faults didn't know about the new
vm_insert_page() case.

Also make some things a bit more anal wrt VM_PFNMAP.

Pointed out by Hugh Dickins <hugh@veritas.com>

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

4 files changed, 5 insertions, 3 deletions

diff --git a/include/linux/mm.h b/include/linux/mm.h
index e5677f456742..a06a84d347fb 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -163,6 +163,7 @@ extern unsigned int kobjsize(const void *objp);
 #define VM_HUGETLB      0x00400000      /* Huge TLB Page VM */
 #define VM_NONLINEAR    0x00800000      /* Is non-linear (remap_file_pages) */
 #define VM_MAPPED_COPY  0x01000000      /* T if mapped copy of data (nommu mmap) */
+#define VM_INSERTPAGE   0x02000000      /* The vma has had "vm_insert_page()" done on it */
 
 #ifndef VM_STACK_DEFAULT_FLAGS          /* arch can override this */
 #define VM_STACK_DEFAULT_FLAGS VM_DATA_DEFAULT_FLAGS
diff --git a/mm/memory.c b/mm/memory.c
index d22f78c8a381..d8dde07a3656 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -574,7 +574,7 @@ int copy_page_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
          * readonly mappings. The tradeoff is that copy_page_range is more
          * efficient than faulting.
          */
-        if (!(vma->vm_flags & (VM_HUGETLB|VM_NONLINEAR|VM_PFNMAP))) {
+        if (!(vma->vm_flags & (VM_HUGETLB|VM_NONLINEAR|VM_PFNMAP|VM_INSERTPAGE))) {
                 if (!vma->anon_vma)
                         return 0;
         }
@@ -1228,6 +1228,7 @@ int vm_insert_page(struct vm_area_struct *vma, unsigned long addr, struct page *
                 return -EFAULT;
         if (!page_count(page))
                 return -EINVAL;
+        vma->vm_flags |= VM_INSERTPAGE;
         return insert_page(vma->vm_mm, addr, page, vma->vm_page_prot);
 }
 EXPORT_SYMBOL(vm_insert_page);
diff --git a/mm/mmap.c b/mm/mmap.c
index 11ca5927d5ff..64ba4dbcb7de 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -611,7 +611,7 @@ again:			remove_next = 1 + (end > next->vm_end);
  * If the vma has a ->close operation then the driver probably needs to release
  * per-vma resources, so we don't attempt to merge those.
  */
-#define VM_SPECIAL (VM_IO | VM_DONTCOPY | VM_DONTEXPAND | VM_RESERVED)
+#define VM_SPECIAL (VM_IO | VM_DONTCOPY | VM_DONTEXPAND | VM_RESERVED | VM_PFNMAP)
 
 static inline int is_mergeable_vma(struct vm_area_struct *vma,
                         struct file *file, unsigned long vm_flags)
diff --git a/mm/mremap.c b/mm/mremap.c
index b535438c363c..ddaeee9a0b69 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -323,7 +323,7 @@ unsigned long do_mremap(unsigned long addr,
         /* We can't remap across vm area boundaries */
         if (old_len > vma->vm_end - addr)
                 goto out;
-        if (vma->vm_flags & VM_DONTEXPAND) {
+        if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP)) {
                 if (new_len > old_len)
                         goto out;
         }