3 files changed, 129 insertions, 8 deletions

diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c
index 5303b3db3c98..35ac5044ddfd 100644
--- a/fs/xfs/xfs_log_recover.c
+++ b/fs/xfs/xfs_log_recover.c
@@ -3959,6 +3959,25 @@ xlog_recover(
                         return error;
                 }
 
+                /*
+                 * Version 5 superblock log feature mask validation. We know the
+                 * log is dirty so check if there are any unknown log features
+                 * in what we need to recover. If there are unknown features
+                 * (e.g. unsupported transactions, then simply reject the
+                 * attempt at recovery before touching anything.
+                 */
+                if (XFS_SB_VERSION_NUM(&log->l_mp->m_sb) == XFS_SB_VERSION_5 &&
+                    xfs_sb_has_incompat_log_feature(&log->l_mp->m_sb,
+                                        XFS_SB_FEAT_INCOMPAT_LOG_UNKNOWN)) {
+                        xfs_warn(log->l_mp,
+"Superblock has unknown incompatible log features (0x%x) enabled.\n"
+"The log can not be fully and/or safely recovered by this kernel.\n"
+"Please recover the log on a kernel that supports the unknown features.",
+                                (log->l_mp->m_sb.sb_features_log_incompat &
+                                        XFS_SB_FEAT_INCOMPAT_LOG_UNKNOWN));
+                        return EINVAL;
+                }
+
                 xfs_notice(log->l_mp, "Starting recovery (logdev: %s)",
                                 log->l_mp->m_logname ? log->l_mp->m_logname
                                                      : "internal");
diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index 140136cf2dc0..f6bfbd734669 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -114,7 +114,9 @@ static const struct {
     { offsetof(xfs_sb_t, sb_features_compat), 0 },
     { offsetof(xfs_sb_t, sb_features_ro_compat), 0 },
     { offsetof(xfs_sb_t, sb_features_incompat), 0 },
+    { offsetof(xfs_sb_t, sb_features_log_incompat), 0 },
     { offsetof(xfs_sb_t, sb_crc),        0 },
+    { offsetof(xfs_sb_t, sb_pad),        0 },
     { offsetof(xfs_sb_t, sb_pquotino),   0 },
     { offsetof(xfs_sb_t, sb_lsn),        0 },
     { sizeof(xfs_sb_t),                  0 }
@@ -334,14 +336,45 @@ xfs_mount_validate_sb(
         }
 
         /*
-         * Do not allow Version 5 superblocks to mount right now, even though
-         * support is in place. We need to implement the proper feature masks
-         * first.
+         * Version 5 superblock feature mask validation. Reject combinations the
+         * kernel cannot support up front before checking anything else.
          */
         if (XFS_SB_VERSION_NUM(sbp) == XFS_SB_VERSION_5) {
                 xfs_alert(mp,
-        "Version 5 superblock detected. Experimental support not yet enabled!");
-                return XFS_ERROR(EINVAL);
+"Version 5 superblock detected. This kernel has EXPERIMENTAL support enabled!\n"
+"Use of these features in this kernel is at your own risk!");
+
+                if (xfs_sb_has_compat_feature(sbp,
+                                        XFS_SB_FEAT_COMPAT_UNKNOWN)) {
+                        xfs_warn(mp,
+"Superblock has unknown compatible features (0x%x) enabled.\n"
+"Using a more recent kernel is recommended.",
+                                (sbp->sb_features_compat &
+                                                XFS_SB_FEAT_COMPAT_UNKNOWN));
+                }
+
+                if (xfs_sb_has_ro_compat_feature(sbp,
+                                        XFS_SB_FEAT_RO_COMPAT_UNKNOWN)) {
+                        xfs_alert(mp,
+"Superblock has unknown read-only compatible features (0x%x) enabled.",
+                                (sbp->sb_features_ro_compat &
+                                                XFS_SB_FEAT_RO_COMPAT_UNKNOWN));
+                        if (!(mp->m_flags & XFS_MOUNT_RDONLY)) {
+                                xfs_warn(mp,
+"Attempted to mount read-only compatible filesystem read-write.\n"
+"Filesystem can only be safely mounted read only.");
+                                return XFS_ERROR(EINVAL);
+                        }
+                }
+                if (xfs_sb_has_incompat_feature(sbp,
+                                        XFS_SB_FEAT_INCOMPAT_UNKNOWN)) {
+                        xfs_warn(mp,
+"Superblock has unknown incompatible features (0x%x) enabled.\n"
+"Filesystem can not be safely mounted by this kernel.",
+                                (sbp->sb_features_incompat &
+                                                XFS_SB_FEAT_INCOMPAT_UNKNOWN));
+                        return XFS_ERROR(EINVAL);
+                }
         }
 
         if (unlikely(
@@ -580,6 +613,9 @@ xfs_sb_from_disk(
         to->sb_features_compat = be32_to_cpu(from->sb_features_compat);
         to->sb_features_ro_compat = be32_to_cpu(from->sb_features_ro_compat);
         to->sb_features_incompat = be32_to_cpu(from->sb_features_incompat);
+        to->sb_features_log_incompat =
+                                be32_to_cpu(from->sb_features_log_incompat);
+        to->sb_pad = 0;
         to->sb_pquotino = be64_to_cpu(from->sb_pquotino);
         to->sb_lsn = be64_to_cpu(from->sb_lsn);
 }
@@ -786,7 +822,7 @@ reread:
         if (bp->b_error) {
                 error = bp->b_error;
                 if (loud)
-                        xfs_warn(mp, "SB validate failed");
+                        xfs_warn(mp, "SB validate failed with error %d.", error);
                 goto release_buf;
         }
 
diff --git a/fs/xfs/xfs_sb.h b/fs/xfs/xfs_sb.h
index 457fefae5683..2de58a85833c 100644
--- a/fs/xfs/xfs_sb.h
+++ b/fs/xfs/xfs_sb.h
@@ -168,8 +168,10 @@ typedef struct xfs_sb {
         __uint32_t      sb_features_compat;
         __uint32_t      sb_features_ro_compat;
         __uint32_t      sb_features_incompat;
+        __uint32_t      sb_features_log_incompat;
 
         __uint32_t      sb_crc;         /* superblock crc */
+        __uint32_t      sb_pad;
 
         xfs_ino_t       sb_pquotino;    /* project quota inode */
         xfs_lsn_t       sb_lsn;         /* last write sequence */
@@ -250,8 +252,10 @@ typedef struct xfs_dsb {
         __be32          sb_features_compat;
         __be32          sb_features_ro_compat;
         __be32          sb_features_incompat;
+        __be32          sb_features_log_incompat;
 
         __le32          sb_crc;         /* superblock crc */
+        __be32          sb_pad;
 
         __be64          sb_pquotino;    /* project quota inode */
         __be64          sb_lsn;         /* last write sequence */
@@ -276,7 +280,8 @@ typedef enum {
         XFS_SBS_INOALIGNMT, XFS_SBS_UNIT, XFS_SBS_WIDTH, XFS_SBS_DIRBLKLOG,
         XFS_SBS_LOGSECTLOG, XFS_SBS_LOGSECTSIZE, XFS_SBS_LOGSUNIT,
         XFS_SBS_FEATURES2, XFS_SBS_BAD_FEATURES2, XFS_SBS_FEATURES_COMPAT,
-        XFS_SBS_FEATURES_RO_COMPAT, XFS_SBS_FEATURES_INCOMPAT, XFS_SBS_CRC,
+        XFS_SBS_FEATURES_RO_COMPAT, XFS_SBS_FEATURES_INCOMPAT,
+        XFS_SBS_FEATURES_LOG_INCOMPAT, XFS_SBS_CRC, XFS_SBS_PAD,
         XFS_SBS_PQUOTINO, XFS_SBS_LSN,
         XFS_SBS_FIELDCOUNT
 } xfs_sb_field_t;
@@ -306,6 +311,7 @@ typedef enum {
 #define XFS_SB_FEATURES_COMPAT  XFS_SB_MVAL(FEATURES_COMPAT)
 #define XFS_SB_FEATURES_RO_COMPAT XFS_SB_MVAL(FEATURES_RO_COMPAT)
 #define XFS_SB_FEATURES_INCOMPAT XFS_SB_MVAL(FEATURES_INCOMPAT)
+#define XFS_SB_FEATURES_LOG_INCOMPAT XFS_SB_MVAL(FEATURES_LOG_INCOMPAT)
 #define XFS_SB_CRC              XFS_SB_MVAL(CRC)
 #define XFS_SB_PQUOTINO         XFS_SB_MVAL(PQUOTINO)
 #define XFS_SB_NUM_BITS         ((int)XFS_SBS_FIELDCOUNT)
@@ -316,7 +322,8 @@ typedef enum {
          XFS_SB_QFLAGS | XFS_SB_SHARED_VN | XFS_SB_UNIT | XFS_SB_WIDTH | \
          XFS_SB_ICOUNT | XFS_SB_IFREE | XFS_SB_FDBLOCKS | XFS_SB_FEATURES2 | \
          XFS_SB_BAD_FEATURES2 | XFS_SB_FEATURES_COMPAT | \
-         XFS_SB_FEATURES_RO_COMPAT | XFS_SB_FEATURES_INCOMPAT | XFS_SB_PQUOTINO)
+         XFS_SB_FEATURES_RO_COMPAT | XFS_SB_FEATURES_INCOMPAT | \
+         XFS_SB_FEATURES_LOG_INCOMPAT | XFS_SB_PQUOTINO)
 
 
 /*
@@ -552,6 +559,65 @@ static inline int xfs_sb_version_hascrc(xfs_sb_t *sbp)
         return XFS_SB_VERSION_NUM(sbp) == XFS_SB_VERSION_5;
 }
 
+
+/*
+ * Extended v5 superblock feature masks. These are to be used for new v5
+ * superblock features only.
+ *
+ * Compat features are new features that old kernels will not notice or affect
+ * and so can mount read-write without issues.
+ *
+ * RO-Compat (read only) are features that old kernels can read but will break
+ * if they write. Hence only read-only mounts of such filesystems are allowed on
+ * kernels that don't support the feature bit.
+ *
+ * InCompat features are features which old kernels will not understand and so
+ * must not mount.
+ *
+ * Log-InCompat features are for changes to log formats or new transactions that
+ * can't be replayed on older kernels. The fields are set when the filesystem is
+ * mounted, and a clean unmount clears the fields.
+ */
+#define XFS_SB_FEAT_COMPAT_ALL 0
+#define XFS_SB_FEAT_COMPAT_UNKNOWN      ~XFS_SB_FEAT_COMPAT_ALL
+static inline bool
+xfs_sb_has_compat_feature(
+        struct xfs_sb   *sbp,
+        __uint32_t      feature)
+{
+        return (sbp->sb_features_compat & feature) != 0;
+}
+
+#define XFS_SB_FEAT_RO_COMPAT_ALL 0
+#define XFS_SB_FEAT_RO_COMPAT_UNKNOWN   ~XFS_SB_FEAT_RO_COMPAT_ALL
+static inline bool
+xfs_sb_has_ro_compat_feature(
+        struct xfs_sb   *sbp,
+        __uint32_t      feature)
+{
+        return (sbp->sb_features_ro_compat & feature) != 0;
+}
+
+#define XFS_SB_FEAT_INCOMPAT_ALL 0
+#define XFS_SB_FEAT_INCOMPAT_UNKNOWN    ~XFS_SB_FEAT_INCOMPAT_ALL
+static inline bool
+xfs_sb_has_incompat_feature(
+        struct xfs_sb   *sbp,
+        __uint32_t      feature)
+{
+        return (sbp->sb_features_incompat & feature) != 0;
+}
+
+#define XFS_SB_FEAT_INCOMPAT_LOG_ALL 0
+#define XFS_SB_FEAT_INCOMPAT_LOG_UNKNOWN        ~XFS_SB_FEAT_INCOMPAT_LOG_ALL
+static inline bool
+xfs_sb_has_incompat_log_feature(
+        struct xfs_sb   *sbp,
+        __uint32_t      feature)
+{
+        return (sbp->sb_features_log_incompat & feature) != 0;
+}
+
 /*
  * end of superblock version macros
  */