disallow-changing-journal-csum-option-during-remount

   1 ext4: disallow changing journal_csum option during remount
   2
   3 From: "Darrick J. Wong" <darrick.wong@oracle.com>
   4
   5 ext4 does not permit changing the metadata or journal checksum feature
   6 flag while mounted.  Until we decide to support that, don't allow a
   7 remount to change the journal_csum flag (right now we silently fail to
   8 change anything).
   9
  10 Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
  11 Signed-off-by: Theodore Ts'o <tytso@mit.edu>
  12 ---
  13  fs/ext4/super.c |    8 ++++++++
  14  1 file changed, 8 insertions(+)
  15
  16
  17 diff --git a/fs/ext4/super.c b/fs/ext4/super.c
  18 index 5c11e21..96059e0 100644
  19 --- a/fs/ext4/super.c
  20 +++ b/fs/ext4/super.c
  21 @@ -4845,6 +4845,14 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
  22                 goto restore_opts;
  23         }
  24
  25 +       if ((old_opts.s_mount_opt & EXT4_MOUNT_JOURNAL_CHECKSUM) ^
  26 +           test_opt(sb, JOURNAL_CHECKSUM)) {
  27 +               ext4_msg(sb, KERN_ERR, "changing journal_checksum "
  28 +                        "during remount not supported");
  29 +               err = -EINVAL;
  30 +               goto restore_opts;
  31 +       }
  32 +
  33         if (test_opt(sb, DATA_FLAGS) == EXT4_MOUNT_JOURNAL_DATA) {
  34                 if (test_opt2(sb, EXPLICIT_DELALLOC)) {
  35                         ext4_msg(sb, KERN_ERR, "can't mount with "
  36
  37