3 files changed, 22 insertions, 7 deletions

diff --git a/Documentation/filesystems/ext4.txt b/Documentation/filesystems/ext4.txt
index bf4f4b7e11b3..6d94e0696f8c 100644
--- a/Documentation/filesystems/ext4.txt
+++ b/Documentation/filesystems/ext4.txt
@@ -134,9 +134,15 @@ ro                   	Mount filesystem read only. Note that ext4 will
                         mount options "ro,noload" can be used to prevent
                         writes to the filesystem.
 
+journal_checksum        Enable checksumming of the journal transactions.
+                        This will allow the recovery code in e2fsck and the
+                        kernel to detect corruption in the kernel.  It is a
+                        compatible change and will be ignored by older kernels.
+
 journal_async_commit    Commit block can be written to disk without waiting
                         for descriptor blocks. If enabled older kernels cannot
-                        mount the device.
+                        mount the device. This will enable 'journal_checksum'
+                        internally.
 
 journal=update          Update the ext4 file system's journal to the current
                         format.
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 984ca0cb38c3..00d153f2f261 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -743,6 +743,7 @@ struct ext4_inode_info {
 #define EXT4_MOUNT_QUOTA                0x80000 /* Some quota option set */
 #define EXT4_MOUNT_USRQUOTA             0x100000 /* "old" user quota */
 #define EXT4_MOUNT_GRPQUOTA             0x200000 /* "old" group quota */
+#define EXT4_MOUNT_JOURNAL_CHECKSUM     0x800000 /* Journal checksums */
 #define EXT4_MOUNT_JOURNAL_ASYNC_COMMIT 0x1000000 /* Journal Async Commit */
 #define EXT4_MOUNT_I_VERSION            0x2000000 /* i_version support */
 #define EXT4_MOUNT_DELALLOC             0x8000000 /* Delalloc support */
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. */