[ostree] libostree: Silently ignore EPERM when setting EXT2_IMMUTABLE_FL

[Colin Walters <walters src gnome org>]

commit e31daf448afdaec9e692612ae522c7d89bf8be28
Author: Colin Walters <walters verbum org>
Date:   Wed Jun 4 18:21:32 2014 -0400

    libostree: Silently ignore EPERM when setting EXT2_IMMUTABLE_FL
    
    In the case of running ostree as non-root on a regular filesystem (not
    tmpfs which doesn't support immutable), we should just silently do
    nothing if we encounter EPERM.  Cache the result to avoid spam in
    strace.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=728006

 src/libostree/ostree-linuxfsutil.c |   17 +++++++++++++----
 1 files changed, 13 insertions(+), 4 deletions(-)
---
diff --git a/src/libostree/ostree-linuxfsutil.c b/src/libostree/ostree-linuxfsutil.c
index 8e11d2c..2bfc92f 100644
--- a/src/libostree/ostree-linuxfsutil.c
+++ b/src/libostree/ostree-linuxfsutil.c
@@ -38,8 +38,9 @@
  * Alter the immutable flag of object referred to by @fd; may be a
  * regular file or a directory.
  *
- * If the operation is not supported by the underlying filesystem,
- * this function will silently do nothing.
+ * If the operation is not supported by the underlying filesystem, or
+ * we are running without sufficient privileges, this function will
+ * silently do nothing.
  */
 gboolean
 _ostree_linuxfs_fd_alter_immutable_flag (int            fd,
@@ -50,12 +51,18 @@ _ostree_linuxfs_fd_alter_immutable_flag (int            fd,
   gboolean ret = FALSE;
   unsigned long flags;
   int r;
+  static gint no_alter_immutable = 0;
+
+  if (g_atomic_int_get (&no_alter_immutable))
+    return TRUE;
 
   r = ioctl (fd, EXT2_IOC_GETFLAGS, &flags);
   if (r == -1)
     {
       int errsv = errno;
-      if (errsv == EOPNOTSUPP || errsv == ENOTTY)
+      if (errsv == EPERM)
+        g_atomic_int_set (&no_alter_immutable, 1);
+      else if (errsv == EOPNOTSUPP || errsv == ENOTTY)
         ;
       else
         {
@@ -75,7 +82,9 @@ _ostree_linuxfs_fd_alter_immutable_flag (int            fd,
       if (r == -1)
         {
           int errsv = errno;
-          if (errsv == EOPNOTSUPP || errsv == ENOTTY)
+          if (errsv == EPERM)
+            g_atomic_int_set (&no_alter_immutable, 1);
+          else if (errsv == EOPNOTSUPP || errsv == ENOTTY)
             ;
           else
             {