xfs: Define a new function xfs_is_quota_inode()

In preparation for combined pquota/gquota support, define
a new function to check if the given inode is a quota inode.

Signed-off-by: Chandra Seetharaman <sekharan@us.ibm.com>
Reviewed-by: Ben Myers <bpm@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>

fs/xfs/xfs_sb.h

@@ -618,6 +618,12 @@ xfs_sb_has_incompat_log_feature(
 	return (sbp->sb_features_log_incompat & feature) != 0;
 }
 
+static inline bool
+xfs_is_quota_inode(struct xfs_sb *sbp, xfs_ino_t ino)
+{
+	return (ino == sbp->sb_uquotino || ino == sbp->sb_gquotino);
+}
+
 /*
  * end of superblock version macros
  */