3 files changed, 61 insertions, 0 deletions

diff --git a/fs/nilfs2/nilfs.h b/fs/nilfs2/nilfs.h
index cfedc48d78d9..0842d775b3e0 100644
--- a/fs/nilfs2/nilfs.h
+++ b/fs/nilfs2/nilfs.h
@@ -275,6 +275,8 @@ extern struct nilfs_super_block *
 nilfs_read_super_block(struct super_block *, u64, int, struct buffer_head **);
 extern int nilfs_store_magic_and_option(struct super_block *,
                                         struct nilfs_super_block *, char *);
+extern int nilfs_check_feature_compatibility(struct super_block *,
+                                             struct nilfs_super_block *);
 extern void nilfs_set_log_cursor(struct nilfs_super_block *,
                                  struct the_nilfs *);
 extern struct nilfs_super_block **nilfs_prepare_super(struct nilfs_sb_info *,
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);
diff --git a/fs/nilfs2/the_nilfs.c b/fs/nilfs2/the_nilfs.c
index f2efc8c5be7f..da67b560f3c3 100644
--- a/fs/nilfs2/the_nilfs.c
+++ b/fs/nilfs2/the_nilfs.c
@@ -385,11 +385,23 @@ int load_nilfs(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi)
                 goto skip_recovery;
 
         if (s_flags & MS_RDONLY) {
+                __u64 features;
+
                 if (nilfs_test_opt(sbi, NORECOVERY)) {
                         printk(KERN_INFO "NILFS: norecovery option specified. "
                                "skipping roll-forward recovery\n");
                         goto skip_recovery;
                 }
+                features = le64_to_cpu(nilfs->ns_sbp[0]->s_feature_compat_ro) &
+                        ~NILFS_FEATURE_COMPAT_RO_SUPP;
+                if (features) {
+                        printk(KERN_ERR "NILFS: couldn't proceed with "
+                               "recovery because of unsupported optional "
+                               "features (%llx)\n",
+                               (unsigned long long)features);
+                        err = -EROFS;
+                        goto failed_unload;
+                }
                 if (really_read_only) {
                         printk(KERN_ERR "NILFS: write access "
                                "unavailable, cannot proceed.\n");
@@ -644,6 +656,10 @@ int init_nilfs(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi, char *data)
                 if (err)
                         goto out;
 
+                err = nilfs_check_feature_compatibility(sb, sbp);
+                if (err)
+                        goto out;
+
                 blocksize = BLOCK_SIZE << le32_to_cpu(sbp->s_log_block_size);
                 if (sb->s_blocksize != blocksize &&
                     !sb_set_blocksize(sb, blocksize)) {
@@ -669,6 +685,10 @@ int init_nilfs(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi, char *data)
         if (err)
                 goto failed_sbh;
 
+        err = nilfs_check_feature_compatibility(sb, sbp);
+        if (err)
+                goto failed_sbh;
+
         blocksize = BLOCK_SIZE << le32_to_cpu(sbp->s_log_block_size);
         if (sb->s_blocksize != blocksize) {
                 int hw_blocksize = bdev_logical_block_size(sb->s_bdev);