Fix bug #13298 with failed backups by falling back on set-file-modes.

 src/fileio.c (Fset_file_selinux_context, Fset_file_acl): Return t if
 file's SELinux context or ACLs successfully set, nil otherwise.

 lisp/files.el (backup-buffer-copy, basic-save-buffer-2): If
 set-file-extended-attributes fails, fall back on set-file-modes
 instead of signaling an error.

 doc/lispref/files.texi (Changing Files): Document the return values of
 set-file-selinux-context and set-file-acl.

2 files changed, 12 insertions, 2 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 76f6865972c..f40f936d13a 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,5 +1,9 @@
 2012-12-29  Eli Zaretskii  <eliz@gnu.org>
 
+        * fileio.c (Fset_file_selinux_context, Fset_file_acl): Return t if
+        file's SELinux context or ACLs successfully set, nil otherwise.
+        (Bug#13298)
+
         * w32proc.c (reader_thread): Avoid passing NULL handles to
         SetEvent and WaitForSingleObject.
 
diff --git a/src/fileio.c b/src/fileio.c
index 9f70c790592..e824a7abcc5 100644
--- a/src/fileio.c
+++ b/src/fileio.c
@@ -2996,8 +2996,10 @@ DEFUN ("set-file-selinux-context", Fset_file_selinux_context,
 CONTEXT should be a list (USER ROLE TYPE RANGE), where the list
 elements are strings naming the components of a SELinux context.
 
-This function does nothing if SELinux is disabled, or if Emacs was not
-compiled with SELinux support.  */)
+Value is t if setting of SELinux context was successful, nil otherwise.
+
+This function does nothing and returns nil if SELinux is disabled,
+or if Emacs was not compiled with SELinux support.  */)
   (Lisp_Object filename, Lisp_Object context)
 {
   Lisp_Object absname;
@@ -3063,6 +3065,7 @@ compiled with SELinux support.  */)
 
           context_free (parsed_con);
           freecon (con);
+          return Qt;
         }
       else
         report_file_error ("Doing lgetfilecon", Fcons (absname, Qnil));
@@ -3127,6 +3130,8 @@ DEFUN ("set-file-acl", Fset_file_acl, Sset_file_acl,
 ACL-STRING should contain the textual representation of the ACL
 entries in a format suitable for the platform.
 
+Value is t if setting of ACL was successful, nil otherwise.
+
 Setting ACL for local files requires Emacs to be built with ACL
 support.  */)
   (Lisp_Object filename, Lisp_Object acl_string)
@@ -3166,6 +3171,7 @@ support.  */)
         report_file_error ("Setting ACL", Fcons (absname, Qnil));
 
       acl_free (acl);
+      return Qt;
     }
 #endif