nilfs2: reject incompatible filesystem

This forces nilfs to check compatibility of feature flags so as to
reject a filesystem with unknown features when it mounts or remounts
the filesystem.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

1 files changed, 39 insertions, 0 deletions

diff --git a/fs/nilfs2/super.c b/fs/nilfs2/super.c
index 164457316df1..26078b3407c9 100644
--- a/fs/nilfs2/super.c
+++ b/fs/nilfs2/super.c
@@ -790,6 +790,30 @@ int nilfs_store_magic_and_option(struct super_block *sb,
         return !parse_options(data, sb, 0) ? -EINVAL : 0 ;
 }
 
+int nilfs_check_feature_compatibility(struct super_block *sb,
+                                      struct nilfs_super_block *sbp)
+{
+        __u64 features;
+
+        features = le64_to_cpu(sbp->s_feature_incompat) &
+                ~NILFS_FEATURE_INCOMPAT_SUPP;
+        if (features) {
+                printk(KERN_ERR "NILFS: couldn't mount because of unsupported "
+                       "optional features (%llx)\n",
+                       (unsigned long long)features);
+                return -EINVAL;
+        }
+        features = le64_to_cpu(sbp->s_feature_compat_ro) &
+                ~NILFS_FEATURE_COMPAT_RO_SUPP;
+        if (!(sb->s_flags & MS_RDONLY) && features) {
+                printk(KERN_ERR "NILFS: couldn't mount RDWR because of "
+                       "unsupported optional features (%llx)\n",
+                       (unsigned long long)features);
+                return -EINVAL;
+        }
+        return 0;
+}
+
 /**
  * nilfs_fill_super() - initialize a super block instance
  * @sb: super_block
@@ -984,11 +1008,26 @@ static int nilfs_remount(struct super_block *sb, int *flags, char *data)
                 nilfs_cleanup_super(sbi);
                 up_write(&nilfs->ns_sem);
         } else {
+                __u64 features;
+
                 /*
                  * Mounting a RDONLY partition read-write, so reread and
                  * store the current valid flag.  (It may have been changed
                  * by fsck since we originally mounted the partition.)
                  */
+                down_read(&nilfs->ns_sem);
+                features = le64_to_cpu(nilfs->ns_sbp[0]->s_feature_compat_ro) &
+                        ~NILFS_FEATURE_COMPAT_RO_SUPP;
+                up_read(&nilfs->ns_sem);
+                if (features) {
+                        printk(KERN_WARNING "NILFS (device %s): couldn't "
+                               "remount RDWR because of unsupported optional "
+                               "features (%llx)\n",
+                               sb->s_id, (unsigned long long)features);
+                        err = -EROFS;
+                        goto restore_opts;
+                }
+
                 sb->s_flags &= ~MS_RDONLY;
 
                 err = nilfs_attach_segment_constructor(sbi);