xfs: add a incompat feature bit for parent pointers

Create an incompat feature bit and a fs geometry flag so that we can
enable the feature in the ondisk superblock and advertise its existence
to userspace.
Signed-off-by: Mark Tinguely <mark.tinguely@oracle.com>
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Allison Henderson <allison.henderson@oracle.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>

fs/xfs/libxfs/xfs_format.h

@@ -374,6 +374,7 @@ xfs_sb_has_ro_compat_feature(
 #define XFS_SB_FEAT_INCOMPAT_NEEDSREPAIR (1 << 4) /* needs xfs_repair */
 #define XFS_SB_FEAT_INCOMPAT_NREXT64	(1 << 5)  /* large extent counters */
 #define XFS_SB_FEAT_INCOMPAT_EXCHRANGE	(1 << 6)  /* exchangerange supported */
+#define XFS_SB_FEAT_INCOMPAT_PARENT	(1 << 7)  /* parent pointers */
 #define XFS_SB_FEAT_INCOMPAT_ALL \
 		(XFS_SB_FEAT_INCOMPAT_FTYPE | \
 		 XFS_SB_FEAT_INCOMPAT_SPINODES | \

fs/xfs/libxfs/xfs_fs.h

@@ -240,6 +240,7 @@ typedef struct xfs_fsop_resblks {
 #define XFS_FSOP_GEOM_FLAGS_INOBTCNT	(1 << 22) /* inobt btree counter */
 #define XFS_FSOP_GEOM_FLAGS_NREXT64	(1 << 23) /* large extent counters */
 #define XFS_FSOP_GEOM_FLAGS_EXCHANGE_RANGE (1 << 24) /* exchange range */
+#define XFS_FSOP_GEOM_FLAGS_PARENT	(1 << 25) /* linux parent pointers */
 
 /*
  * Minimum and maximum sizes need for growth checks.

fs/xfs/libxfs/xfs_sb.c

@@ -178,6 +178,8 @@ xfs_sb_version_to_features(
 		features |= XFS_FEAT_NREXT64;
 	if (sbp->sb_features_incompat & XFS_SB_FEAT_INCOMPAT_EXCHRANGE)
 		features |= XFS_FEAT_EXCHANGE_RANGE;
+	if (sbp->sb_features_incompat & XFS_SB_FEAT_INCOMPAT_PARENT)
+		features |= XFS_FEAT_PARENT;
 
 	return features;
 }
@@ -1254,6 +1256,8 @@ xfs_fs_geometry(
 		geo->flags |= XFS_FSOP_GEOM_FLAGS_BIGTIME;
 	if (xfs_has_inobtcounts(mp))
 		geo->flags |= XFS_FSOP_GEOM_FLAGS_INOBTCNT;
+	if (xfs_has_parent(mp))
+		geo->flags |= XFS_FSOP_GEOM_FLAGS_PARENT;
 	if (xfs_has_sector(mp)) {
 		geo->flags |= XFS_FSOP_GEOM_FLAGS_SECTOR;
 		geo->logsectsize = sbp->sb_logsectsize;

fs/xfs/xfs_super.c

@@ -1746,6 +1746,10 @@ xfs_fs_fill_super(
 		xfs_warn(mp,
 	"EXPERIMENTAL exchange-range feature enabled. Use at your own risk!");
 
+	if (xfs_has_parent(mp))
+		xfs_warn(mp,
+	"EXPERIMENTAL parent pointer feature enabled. Use at your own risk!");
+
 	error = xfs_mountfs(mp);
 	if (error)
 		goto out_filestream_unmount;