1 files changed, 15 insertions, 0 deletions

diff --git a/fs/reiserfs/super.c b/fs/reiserfs/super.c
index b82897ae090b..57adfe90d5ae 100644
--- a/fs/reiserfs/super.c
+++ b/fs/reiserfs/super.c
@@ -1725,6 +1725,21 @@ static int reiserfs_fill_super(struct super_block *s, void *data, int silent)
                 set_sb_umount_state(rs, REISERFS_ERROR_FS);
                 set_sb_fs_state(rs, 0);
 
+                /* Clear out s_bmap_nr if it would wrap. We can handle this
+                 * case, but older revisions can't. This will cause the
+                 * file system to fail mount on those older implementations,
+                 * avoiding corruption. -jeffm */
+                if (bmap_would_wrap(reiserfs_bmap_count(s)) &&
+                    sb_bmap_nr(rs) != 0) {
+                        reiserfs_warning(s, "super-2030: This file system "
+                                        "claims to use %u bitmap blocks in "
+                                        "its super block, but requires %u. "
+                                        "Clearing to zero.", sb_bmap_nr(rs),
+                                        reiserfs_bmap_count(s));
+
+                        set_sb_bmap_nr(rs, 0);
+                }
+
                 if (old_format_only(s)) {
                         /* filesystem of format 3.5 either with standard or non-standard
                            journal */