Revert "ext4: Remove journal_checksum mount option and enable it by default"

This reverts commit d0646f7b636d067d715fab52a2ba9c6f0f46b0d7, as
requested by Eric Sandeen.

It can basically cause an ext4 filesystem to miss recovery (and thus get
mounted with errors) if the journal checksum does not match.

Quoth Eric:

   "My hand-wavy hunch about what is happening is that we're finding a
    bad checksum on the last partially-written transaction, which is
    not surprising, but if we have a wrapped log and we're doing the
    initial scan for head/tail, and we abort scanning on that bad
    checksum, then we are essentially running an unrecovered filesystem.

    But that's hand-wavy and I need to go look at the code.

    We lived without journal checksums on by default until now, and at
    this point they're doing more harm than good, so we should revert
    the default-changing commit until we can fix it and do some good
    power-fail testing with the fixes in place."

See

	http://bugzilla.kernel.org/show_bug.cgi?id=14354

for all the gory details.

Requested-by: Eric Sandeen <sandeen@redhat.com>
Cc: Theodore Tso <tytso@mit.edu>
Cc: Alexey Fisher <bug-track@fisher-privat.net>
Cc: Maxim Levitsky <maximlevitsky@gmail.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: Mathias Burén <mathias.buren@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 14 insertions, 6 deletions

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 312211ee05af..d4ca92aab514 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1300,9 +1300,11 @@ static int parse_options(char *options, struct super_block *sb,
                         *journal_devnum = option;
                         break;
                 case Opt_journal_checksum:
-                        break;  /* Kept for backwards compatibility */
+                        set_opt(sbi->s_mount_opt, JOURNAL_CHECKSUM);
+                        break;
                 case Opt_journal_async_commit:
                         set_opt(sbi->s_mount_opt, JOURNAL_ASYNC_COMMIT);
+                        set_opt(sbi->s_mount_opt, JOURNAL_CHECKSUM);
                         break;
                 case Opt_noload:
                         set_opt(sbi->s_mount_opt, NOLOAD);
@@ -2759,14 +2761,20 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
                 goto failed_mount4;
         }
 
-        jbd2_journal_set_features(sbi->s_journal,
-                                  JBD2_FEATURE_COMPAT_CHECKSUM, 0, 0);
-        if (test_opt(sb, JOURNAL_ASYNC_COMMIT))
-                jbd2_journal_set_features(sbi->s_journal, 0, 0,
+        if (test_opt(sb, JOURNAL_ASYNC_COMMIT)) {
+                jbd2_journal_set_features(sbi->s_journal,
+                                JBD2_FEATURE_COMPAT_CHECKSUM, 0,
                                 JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT);
-        else
+        } else if (test_opt(sb, JOURNAL_CHECKSUM)) {
+                jbd2_journal_set_features(sbi->s_journal,
+                                JBD2_FEATURE_COMPAT_CHECKSUM, 0, 0);
                 jbd2_journal_clear_features(sbi->s_journal, 0, 0,
                                 JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT);
+        } else {
+                jbd2_journal_clear_features(sbi->s_journal,
+                                JBD2_FEATURE_COMPAT_CHECKSUM, 0,
+                                JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT);
+        }
 
         /* We have now updated the journal if required, so we can
          * validate the data journaling mode. */