gfs2: Switch to generic xattr handlers

Switch to the generic xattr handlers and take the necessary glocks at
the layer below. The following are the new xattr "entry points"; they
are called with the glock held already in the following cases:

  gfs2_xattr_get: From SELinux, during lookups.
  gfs2_xattr_set: The glock is never held.
  gfs2_get_acl: From gfs2_create_inode -> posix_acl_create and
                gfs2_setattr -> posix_acl_chmod.
  gfs2_set_acl: From gfs2_setattr -> posix_acl_chmod.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/gfs2/acl.h

@@ -15,6 +15,7 @@
 #define GFS2_ACL_MAX_ENTRIES(sdp) ((300 << (sdp)->sd_sb.sb_bsize_shift) >> 12)
 
 extern struct posix_acl *gfs2_get_acl(struct inode *inode, int type);
+extern int __gfs2_set_acl(struct inode *inode, struct posix_acl *acl, int type);
 extern int gfs2_set_acl(struct inode *inode, struct posix_acl *acl, int type);
 
 #endif /* __ACL_DOT_H__ */