[PATCH] ACL handling simplification + support for NFSv4

[Ondrej Valousek <ondrej.valousek.xm@renesas.com>]

The following patch is aiming to improve & simplify ACL handling in copy-acl.c
Changes/Benefits:
* we no longer try to decode ACLs, instead we just copy the whole xattr with ACLs
making the code simpler and faster
* side effect is support for NFSv4 acls
Disadvantages:
* I agree the patch is maybe too aggresive, but works suprisingly well, but let me know
if I missed something important
* it pulls in dependency on libattr (so needs to be linked with -lattr, the automake
changes are not yet included in this patch), but on the other way, we could possibly ditch
dependency on libacl.
* we can't do any ACLs conversions, but these are not (AFAIK) being done anyway in the
old code

As I said, my goal is really for "cp -p" to preserve ACLs regardless of the type.
I tried to experiment with variety of filesystems (posix and nfs) and it seems to me
to work exactly the way the old code worked (plus handy support for NFSv4).

Ondrej

---
 lib/copy-acl.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/lib/copy-acl.c b/lib/copy-acl.c
index 5fc42b7f6..341d1f605 100644
--- a/lib/copy-acl.c
+++ b/lib/copy-acl.c
@@ -29,6 +29,20 @@
 #define _(msgid) gettext (msgid)
 
 
+#if USE_XATTR
+
+# include <attr/libattr.h>
+
+static int
+copy_attr_permissions (const char *name, struct error_context *ctx)
+{
+	int action = attr_copy_action (name, ctx);
+	return action == ATTR_ACTION_PERMISSIONS;
+}
+
+#endif  /* USE_XATTR */
+
+
 /* Copy access control lists from one file to another. If SOURCE_DESC is
    a valid file descriptor, use file descriptor operations, else use
    filename based operations on SRC_NAME. Likewise for DEST_DESC and
@@ -43,7 +57,22 @@ int
 copy_acl (const char *src_name, int source_desc, const char *dst_name,
           int dest_desc, mode_t mode)
 {
-  int ret = qcopy_acl (src_name, source_desc, dst_name, dest_desc, mode);
+  int ret;
+#ifdef USE_XATTR
+  ret = chmod_or_fchmod (dst_name, dest_desc, mode);
+  /* Rather than fiddling with acls one by one, we just copy the whole ACL xattrs 
+   * (Posix or NFSv4). Of course, that won't address ACLs conversion 
+   * (i.e. posix <-> nfs4) but we can't do it anyway, so for now, we don't care
+   */
+  if(ret == 0)
+    ret = source_desc <= 0 && dest_desc <= 0
+      ? attr_copy_file (src_name, dst_name, copy_attr_permissions, NULL)
+      : attr_copy_fd (src_name, source_desc, dst_name, dest_desc, copy_attr_permissions, NULL);
+#else
+  /* no XATTR, so we proceed the old dusty way */
+  ret = qcopy_acl (src_name, source_desc, dst_name, dest_desc, mode);
+#endif
+
   switch (ret)
     {
     case -2: