xfs: Extend project quotas to support 32bit project ids

This patch adds support for 32bit project quota identifiers.

On disk format is backward compatible with 16bit projid numbers. projid
on disk is now kept in two 16bit values - di_projid_lo (which holds the
same position as old 16bit projid value) and new di_projid_hi (takes
existing padding) and converts from/to 32bit value on the fly.

xfs_admin (for existing fs), mkfs.xfs (for new fs) needs to be used
to enable PROJID32BIT support.

Signed-off-by: Arkadiusz Miƛkiewicz <arekm@maven.pl>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Alex Elder <aelder@sgi.com>
diff --git a/fs/xfs/xfs_dinode.h b/fs/xfs/xfs_dinode.h
index e5b153b..dffba9b 100644
--- a/fs/xfs/xfs_dinode.h
+++ b/fs/xfs/xfs_dinode.h
@@ -49,8 +49,9 @@
 	__be32		di_uid;		/* owner's user id */
 	__be32		di_gid;		/* owner's group id */
 	__be32		di_nlink;	/* number of links to file */
-	__be16		di_projid;	/* owner's project id */
-	__u8		di_pad[8];	/* unused, zeroed space */
+	__be16		di_projid_lo;	/* lower part of owner's project id */
+	__be16		di_projid_hi;	/* higher part owner's project id */
+	__u8		di_pad[6];	/* unused, zeroed space */
 	__be16		di_flushiter;	/* incremented on flush */
 	xfs_timestamp_t	di_atime;	/* time last accessed */
 	xfs_timestamp_t	di_mtime;	/* time last modified */