xfs: define a new "needrepair" feature

Define an incompat feature flag to indicate that the filesystem needs to
be repaired.  While libxfs will recognize this feature, the kernel will
refuse to mount if the feature flag is set, and only xfs_repair will be
able to clear the flag.  The goal here is to force the admin to run
xfs_repair to completion after upgrading the filesystem, or if we
otherwise detect anomalies.
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>

fs/xfs/libxfs/xfs_format.h

@@ -468,6 +468,7 @@ xfs_sb_has_ro_compat_feature(
 #define XFS_SB_FEAT_INCOMPAT_SPINODES	(1 << 1)	/* sparse inode chunks */
 #define XFS_SB_FEAT_INCOMPAT_META_UUID	(1 << 2)	/* metadata UUID */
 #define XFS_SB_FEAT_INCOMPAT_BIGTIME	(1 << 3)	/* large timestamps */
+#define XFS_SB_FEAT_INCOMPAT_NEEDSREPAIR (1 << 4)	/* needs xfs_repair */
 #define XFS_SB_FEAT_INCOMPAT_ALL \
 		(XFS_SB_FEAT_INCOMPAT_FTYPE|	\
 		 XFS_SB_FEAT_INCOMPAT_SPINODES|	\
@@ -584,6 +585,12 @@ static inline bool xfs_sb_version_hasinobtcounts(struct xfs_sb *sbp)
 		(sbp->sb_features_ro_compat & XFS_SB_FEAT_RO_COMPAT_INOBTCNT);
 }
 
+static inline bool xfs_sb_version_needsrepair(struct xfs_sb *sbp)
+{
+	return XFS_SB_VERSION_NUM(sbp) == XFS_SB_VERSION_5 &&
+		(sbp->sb_features_incompat & XFS_SB_FEAT_INCOMPAT_NEEDSREPAIR);
+}
+
 /*
  * end of superblock version macros
  */

fs/xfs/xfs_super.c

@@ -1467,6 +1467,13 @@ xfs_fc_fill_super(
 #endif
 	}
 
+	/* Filesystem claims it needs repair, so refuse the mount. */
+	if (xfs_sb_version_needsrepair(&mp->m_sb)) {
+		xfs_warn(mp, "Filesystem needs repair.  Please run xfs_repair.");
+		error = -EFSCORRUPTED;
+		goto out_free_sb;
+	}
+
 	/*
 	 * Don't touch the filesystem if a user tool thinks it owns the primary
 	 * superblock.  mkfs doesn't clear the flag from secondary supers, so