diff -urNp --exclude CVS --exclude BitKeeper --exclude {arch} --exclude .arch-ids x-ref/mm/memory.c x/mm/memory.c
--- x-ref/mm/memory.c	2004-05-31 12:49:48.952993264 +0200
+++ x/mm/memory.c	2004-05-31 12:50:50.205681440 +0200
@@ -576,17 +576,24 @@ int map_user_kiobuf(int rw, struct kiobu
 	err = get_user_pages(current, mm, va, pgcount,
 			(rw==READ), 0, iobuf->maplist, NULL);
 	up_read(&mm->mmap_sem);
-	if (err < 0) {
+	/* get_user_pages returns the amount of mapped pages,
+	 * which can be less than the amount of requested pages
+	 * in some cases. To avoid surprises downstream, we
+	 * unmap and return an error in those cases.  -bjornw
+	 */
+	if(err > 0)
+		iobuf->nr_pages = err;
+	if (err < pgcount) {
+		/* unmap depends on nr_pages being set at this point */
 		unmap_kiobuf(iobuf);
 		dprintk ("map_user_kiobuf: end %d\n", err);
-		return err;
+		return err < 0 ? err : -ENOMEM;
 	}
-	iobuf->nr_pages = err;
-	while (pgcount--) {
+	while (err--) {
 		/* FIXME: flush superflous for rw==READ,
 		 * probably wrong function for rw==WRITE
 		 */
-		flush_dcache_page(iobuf->maplist[pgcount]);
+		flush_dcache_page(iobuf->maplist[err]);
 	}
 	dprintk ("map_user_kiobuf: end OK\n");
 	return 0;