support-freezing-ext2-filesystems

   1 ext4: support freezing ext2 (nojournal) file systems
   2
   3 Through an oversight, when we added nojournal support to ext4, we
   4 didn't add support to allow file system freezing.  This is relatively
   5 easy to add, so let's do it.
   6
   7 Signed-off-by: Theodore Ts'o <tytso@mit.edu>
   8 Reported-by: Dexuan Cui <decui@microsoft.com>
   9 ---
  10  fs/ext4/super.c | 27 ++++++++++++++++-----------
  11  1 file changed, 16 insertions(+), 11 deletions(-)
  12
  13 diff --git a/fs/ext4/super.c b/fs/ext4/super.c
  14 index 4770c98..4db537b 100644
  15 --- a/fs/ext4/super.c
  16 +++ b/fs/ext4/super.c
  17 @@ -1131,6 +1131,8 @@ static const struct super_operations ext4_nojournal_sops = {
  18         .drop_inode     = ext4_drop_inode,
  19         .evict_inode    = ext4_evict_inode,
  20         .sync_fs        = ext4_sync_fs,
  21 +       .freeze_fs      = ext4_freeze,
  22 +       .unfreeze_fs    = ext4_unfreeze,
  23         .put_super      = ext4_put_super,
  24         .statfs         = ext4_statfs,
  25         .remount_fs     = ext4_remount,
  26 @@ -4758,23 +4760,26 @@ static int ext4_freeze(struct super_block *sb)
  27
  28         journal = EXT4_SB(sb)->s_journal;
  29
  30 -       /* Now we set up the journal barrier. */
  31 -       jbd2_journal_lock_updates(journal);
  32 +       if (journal) {
  33 +               /* Now we set up the journal barrier. */
  34 +               jbd2_journal_lock_updates(journal);
  35
  36 -       /*
  37 -        * Don't clear the needs_recovery flag if we failed to flush
  38 -        * the journal.
  39 -        */
  40 -       error = jbd2_journal_flush(journal);
  41 -       if (error < 0)
  42 -               goto out;
  43 +               /*
  44 +                * Don't clear the needs_recovery flag if we failed to
  45 +                * flush the journal.
  46 +                */
  47 +               error = jbd2_journal_flush(journal);
  48 +               if (error < 0)
  49 +                       goto out;
  50 +       }
  51
  52         /* Journal blocked and flushed, clear needs_recovery flag. */
  53         EXT4_CLEAR_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_RECOVER);
  54         error = ext4_commit_super(sb, 1);
  55  out:
  56 -       /* we rely on upper layer to stop further updates */
  57 -       jbd2_journal_unlock_updates(EXT4_SB(sb)->s_journal);
  58 +       if (journal)
  59 +               /* we rely on upper layer to stop further updates */
  60 +               jbd2_journal_unlock_updates(journal);
  61         return error;
  62  }
  63