ceph: Switch to generic xattr handlers

Add a catch-all xattr handler at the end of ceph_xattr_handlers.  Check
for valid attribute names there, and remove those checks from
__ceph_{get,set,remove}xattr instead.  No "system.*" xattrs need to be
handled by the catch-all handler anymore.

The set xattr handler is called with a NULL value to indicate that the
attribute should be removed; __ceph_setxattr already handles that case
correctly (ceph_set_acl could already calling __ceph_setxattr with a NULL
value).

Move the check for snapshots from ceph_{set,remove}xattr into
__ceph_{set,remove}xattr.  With that, ceph_{get,set,remove}xattr can be
replaced with the generic iops.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: "Yan, Zheng" <zyan@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/ceph/dir.c b/fs/ceph/dir.c
index fadc243..2e0afdc 100644
--- a/fs/ceph/dir.c
+++ b/fs/ceph/dir.c
@@ -5,6 +5,7 @@
 #include <linux/namei.h>
 #include <linux/slab.h>
 #include <linux/sched.h>
+#include <linux/xattr.h>
 
 #include "super.h"
 #include "mds_client.h"
@@ -1342,10 +1343,10 @@
 	.permission = ceph_permission,
 	.getattr = ceph_getattr,
 	.setattr = ceph_setattr,
-	.setxattr = ceph_setxattr,
-	.getxattr = ceph_getxattr,
+	.setxattr = generic_setxattr,
+	.getxattr = generic_getxattr,
 	.listxattr = ceph_listxattr,
-	.removexattr = ceph_removexattr,
+	.removexattr = generic_removexattr,
 	.get_acl = ceph_get_acl,
 	.set_acl = ceph_set_acl,
 	.mknod = ceph_mknod,