[PATCH] unpaged: private write VM_RESERVED

The PageReserved removal in 2.6.15-rc1 issued a "deprecated" message when you
tried to mmap or mprotect MAP_PRIVATE PROT_WRITE a VM_RESERVED, and failed
with -EACCES: because do_wp_page lacks the refinement to COW pages in those
areas, nor do we expect to find anonymous pages in them; and it seemed just
bloat to add code for handling such a peculiar case.  But immediately it
caused vbetool and ddcprobe (using lrmi) to fail.

So revert the "deprecated" messages, letting mmap and mprotect succeed.  But
leave do_wp_page's BUG_ON(vma->vm_flags & VM_RESERVED) in place until we've
added the code to do it right: so this particular patch is only good if the
app doesn't really need to write to that private area.
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

mm/mmap.c

@@ -1076,17 +1076,6 @@ unsigned long do_mmap_pgoff(struct file * file, unsigned long addr,
 		error = file->f_op->mmap(file, vma);
 		if (error)
 			goto unmap_and_free_vma;
-		if ((vma->vm_flags & (VM_SHARED | VM_WRITE | VM_RESERVED))
-						== (VM_WRITE | VM_RESERVED)) {
-			printk(KERN_WARNING "program %s is using MAP_PRIVATE, "
-				"PROT_WRITE mmap of VM_RESERVED memory, which "
-				"is deprecated. Please report this to "
-				"linux-kernel@vger.kernel.org\n",current->comm);
-			if (vma->vm_ops && vma->vm_ops->close)
-				vma->vm_ops->close(vma);
-			error = -EACCES;
-			goto unmap_and_free_vma;
-		}
 	} else if (vm_flags & VM_SHARED) {
 		error = shmem_zero_setup(vma);
 		if (error)

mm/mprotect.c

@@ -124,14 +124,6 @@ mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev,
 	 * a MAP_NORESERVE private mapping to writable will now reserve.
 	 */
 	if (newflags & VM_WRITE) {
-		if (oldflags & VM_RESERVED) {
-			BUG_ON(oldflags & VM_WRITE);
-			printk(KERN_WARNING "program %s is using MAP_PRIVATE, "
-				"PROT_WRITE mprotect of VM_RESERVED memory, "
-				"which is deprecated. Please report this to "
-				"linux-kernel@vger.kernel.org\n",current->comm);
-			return -EACCES;
-		}
 		if (!(oldflags & (VM_ACCOUNT|VM_WRITE|VM_SHARED|VM_HUGETLB))) {
 			charged = nrpages;
 			if (security_vm_enough_memory(charged))