[PATCH] resize2fs: exit fix_sb_journal_backup early for external journal

[Eric Sandeen <sandeen@redhat.com>]

Resizing a filesystem with an external journal fails when it tries
to read inode 0:

# touch testfs
# truncate testfs 1342177280
# touch testjournal
# truncate testjournal 134217728
# mke2fs -O journal_dev testjournal 
# losetup /dev/loop0 testjournal 
# mkfs.ext4 -J device=/dev/loop0 testfs 127680
# resize2fs testfs 
resize2fs 1.41.9 (22-Aug-2009)
Resizing the filesystem on testfs to 327680 (4k) blocks.
resize2fs: Illegal inode number while trying to resize testfs
Please run 'e2fsck -fy testfs' to fix the filesystem
after the aborted resize operation.

I think the right, simple thing to do is just bail out early
for an external journal here, as there are no backup blocks
to update.

Reported-by: mjevans1983@gmail.com
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
---

diff --git a/resize/resize2fs.c b/resize/resize2fs.c
index 5a1eb2a..2d4a14f 100644
--- a/resize/resize2fs.c
+++ b/resize/resize2fs.c
@@ -1887,6 +1887,10 @@ static errcode_t fix_sb_journal_backup(ext2_filsys fs)
 	if (!(fs->super->s_feature_compat & EXT3_FEATURE_COMPAT_HAS_JOURNAL))
 		return 0;
 
+	/* External journal? Nothing to do. */
+	if (fs->super->s_journal_dev && !fs->super->s_journal_inum)
+		return 0;
+
 	retval = ext2fs_read_inode(fs, fs->super->s_journal_inum, &inode);
 	if (retval)
 		return retval;