diff -r 6112bcc5d1cf -r b9cc58992572 librazor/atomic-emulate.c
--- a/librazor/atomic-emulate.c	Sat Feb 11 23:50:26 2012 +0000
+++ b/librazor/atomic-emulate.c	Wed Aug 20 18:56:17 2014 +0100
@@ -77,13 +77,6 @@
 
 	atomic = zalloc(sizeof *atomic);
 
-	atomic->toplevel = strdup(".atomic-XXXXXX");
-	if (!mkdtemp(atomic->toplevel)) {
-		free(atomic->toplevel);
-		free(atomic);
-		return NULL;
-	}
-
 	atomic->description = strdup(description);
 
 	return atomic;
@@ -126,12 +119,107 @@
 	free(atomic);
 }
 
+/*
+ * We need a toplevel directory in which to hold temporary files
+ * before they are committed. Since we can generally assume that
+ * we have write permissions anywhere on the disk in question,
+ * the best location is in the relevant root directory. The most
+ * common case where this assumption fails is when testing, when
+ * the current directory is a good choice.
+ * It might be even better to find a mount point above path instead
+ * but this is hard to do, and probably not worth the effort.
+ */
+
+static int
+razor_atomic_set_toplevel_from_path(struct razor_atomic *atomic,
+				    const char *path)
+{
+	if (razor_atomic_in_error_state(atomic))
+		return -1;
+
+	if (atomic->toplevel)
+		return 0;
+
+#ifdef MSWIN_API
+	if (path[0]=='\\' && path[1]=='\\' && path[2] && path[2]!='\\'
+	    && strchr(path+3,'\\')) {
+		/* We have a UNC path: \\servername\sharename... */
+		const char *sharename, *root;
+		int disklen;
+
+		sharename = strchr(path+3,'\\')+1;
+		root = strchr(sharename,'\\');
+		if (root)
+		    disklen = root - path;
+		else
+		    disklen = strlen(path);
+
+		atomic->toplevel =
+		  malloc(disklen + strlen("\\atomic-XXXXXX") + 1);
+		memcpy(atomic->toplevel, path, disklen);
+		strcpy(atomic->toplevel + disklen, "\\atomic-XXXXXX");
+	} else if ((*path>='A' && *path<='Z' || *path>='a' && *path<='z') &&
+		    path[1]==':') {
+		atomic->toplevel = strdup("X:\\atomic-XXXXXX");
+		*atomic->toplevel = *path;
+	} else {
+		DWORD n;
+		wchar_t *buf;
+		char *dir;
+
+		n = GetCurrentDirectoryW(0, NULL);
+		buf = malloc(n * sizeof(wchar_t));
+
+		if (GetCurrentDirectoryW(n, buf)) {
+			dir = razor_utf16_to_utf8(buf, n - 1);
+			razor_atomic_set_toplevel_from_path(atomic, dir);
+
+			free(dir);
+			free(buf);
+			return;
+		} else
+			atomic->toplevel = strdup("C:\\atomic-XXXXXX");
+
+		free(buf);
+	}
+#else
+	atomic->toplevel = strdup("/.atomic-XXXXXX");
+#endif
+
+	if (!mkdtemp(atomic->toplevel)) {
+		int err = errno;
+
+#ifdef EACCES
+		if (err == EACCES) {
+			char *s = strdup("atomic-XXXXXX");
+
+			if (mkdtemp(s)) {
+				free(atomic->toplevel);
+				atomic->toplevel = s;
+				return 0;
+			} else
+				free(s);
+		}
+#endif
+
+		atomic->error = razor_error_new_str(atomic->toplevel,
+						    strerror(err));
+
+		free(atomic->toplevel);
+		atomic->toplevel = NULL;
+	}
+
+	return !atomic->toplevel;
+}
+
 RAZOR_EXPORT int
 razor_atomic_make_dirs(struct razor_atomic *atomic, const char *root,
 		       const char *path)
 {
 	struct atomic_action *a;
 
+	razor_atomic_set_toplevel_from_path(atomic, *root ? root : path);
+
 	if (razor_atomic_in_error_state(atomic))
 		return -1;
 
@@ -148,6 +236,8 @@
 {
 	struct atomic_action *a;
 
+	razor_atomic_set_toplevel_from_path(atomic, path);
+
 	if (razor_atomic_in_error_state(atomic))
 		return -1;
 
@@ -164,6 +254,8 @@
 {
 	struct atomic_action *a;
 
+	razor_atomic_set_toplevel_from_path(atomic, newpath);
+
 	if (razor_atomic_in_error_state(atomic))
 		return -1;
 
@@ -181,6 +273,8 @@
 {
 	struct atomic_action *a;
 
+	razor_atomic_set_toplevel_from_path(atomic, dirname);
+
 	if (razor_atomic_in_error_state(atomic))
 		return -1;
 
@@ -198,6 +292,8 @@
 {
 #if HAVE_SYMLINK
 	struct atomic_action *a;
+
+	razor_atomic_set_toplevel_from_path(atomic, path);
 #endif
 
 	if (razor_atomic_in_error_state(atomic))
@@ -227,6 +323,8 @@
 	struct atomic_action *a;
 	char *tmpnam;
 
+	razor_atomic_set_toplevel_from_path(atomic, filename);
+
 	if (razor_atomic_in_error_state(atomic))
 		return -1;