[PATCH v3 1/5] xfs_repair: refuse to run if we don't recognize version or feature flags

["Darrick J. Wong" <darrick.wong@xxxxxxxxxx>]

Apparently xfs_repair running on a v5 filesystem doesn't check the
compat, rocompat, or incompat feature flags for bits that it doesn't
know about, which means that old xfs_repairs can wreak havoc.  So,
strengthen the checks to prevent repair from "repairing" anything it
doesn't understand.

v2: Move the complaint code after the version number check, and print
the actual feature bits that we don't recognize.

v3: Fix some copy-pasta errors, and simpify the warning messages.

Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
---
 repair/versions.c |   14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/repair/versions.c b/repair/versions.c
index c1dff72..10bcd29 100644
--- a/repair/versions.c
+++ b/repair/versions.c
@@ -175,6 +175,20 @@ _("WARNING:  you have disallowed 
superblock-feature-bits-allowed\n"
                }
        }
 
+       /* Look for V5 feature flags we don't know about */
+       if (XFS_SB_VERSION_NUM(sb) >= XFS_SB_VERSION_5 &&
+           (xfs_sb_has_compat_feature(sb, XFS_SB_FEAT_COMPAT_UNKNOWN) ||
+            xfs_sb_has_ro_compat_feature(sb, XFS_SB_FEAT_RO_COMPAT_UNKNOWN) ||
+            xfs_sb_has_incompat_feature(sb, XFS_SB_FEAT_INCOMPAT_UNKNOWN))) {
+               do_warn(
+_("Superblock has unknown compat/rocompat/incompat features 
(0x%x/0x%x/0x%x).\n"
+  "Using a more recent xfs_repair is recommended.\n"),
+                       sb->sb_features_compat & XFS_SB_FEAT_COMPAT_UNKNOWN,
+                       sb->sb_features_ro_compat & 
XFS_SB_FEAT_RO_COMPAT_UNKNOWN,
+                       sb->sb_features_incompat & 
XFS_SB_FEAT_INCOMPAT_UNKNOWN);
+               return 1;
+       }
+
        if (xfs_sb_version_hasattr(sb))  {
                if (!fs_attributes_allowed)  {
                        if (!no_modify)  {