3 files changed, 40 insertions, 10 deletions

diff --git a/fs/ext4/fsync.c b/fs/ext4/fsync.c
index 0b22497d92e1..98bd140aad01 100644
--- a/fs/ext4/fsync.c
+++ b/fs/ext4/fsync.c
@@ -88,9 +88,21 @@ int ext4_sync_file(struct file *file, struct dentry *dentry, int datasync)
                 return ext4_force_commit(inode->i_sb);
 
         commit_tid = datasync ? ei->i_datasync_tid : ei->i_sync_tid;
-        if (jbd2_log_start_commit(journal, commit_tid))
+        if (jbd2_log_start_commit(journal, commit_tid)) {
+                /*
+                 * When the journal is on a different device than the
+                 * fs data disk, we need to issue the barrier in
+                 * writeback mode.  (In ordered mode, the jbd2 layer
+                 * will take care of issuing the barrier.  In
+                 * data=journal, all of the data blocks are written to
+                 * the journal device.)
+                 */
+                if (ext4_should_writeback_data(inode) &&
+                    (journal->j_fs_dev != journal->j_dev) &&
+                    (journal->j_flags & JBD2_BARRIER))
+                        blkdev_issue_flush(inode->i_sb->s_bdev, NULL);
                 jbd2_log_wait_commit(journal, commit_tid);
-        else if (journal->j_flags & JBD2_BARRIER)
+        } else if (journal->j_flags & JBD2_BARRIER)
                 blkdev_issue_flush(inode->i_sb->s_bdev, NULL);
         return ret;
 }
diff --git a/fs/jbd2/checkpoint.c b/fs/jbd2/checkpoint.c
index ca0f5eb62b20..886849370950 100644
--- a/fs/jbd2/checkpoint.c
+++ b/fs/jbd2/checkpoint.c
@@ -22,6 +22,7 @@
 #include <linux/jbd2.h>
 #include <linux/errno.h>
 #include <linux/slab.h>
+#include <linux/blkdev.h>
 #include <trace/events/jbd2.h>
 
 /*
@@ -515,6 +516,20 @@ int jbd2_cleanup_journal_tail(journal_t *journal)
         journal->j_tail_sequence = first_tid;
         journal->j_tail = blocknr;
         spin_unlock(&journal->j_state_lock);
+
+        /*
+         * If there is an external journal, we need to make sure that
+         * any data blocks that were recently written out --- perhaps
+         * by jbd2_log_do_checkpoint() --- are flushed out before we
+         * drop the transactions from the external journal.  It's
+         * unlikely this will be necessary, especially with a
+         * appropriately sized journal, but we need this to guarantee
+         * correctness.  Fortunately jbd2_cleanup_journal_tail()
+         * doesn't get called all that often.
+         */
+        if ((journal->j_fs_dev != journal->j_dev) &&
+            (journal->j_flags & JBD2_BARRIER))
+                blkdev_issue_flush(journal->j_fs_dev, NULL);
         if (!(journal->j_flags & JBD2_ABORT))
                 jbd2_journal_update_superblock(journal, 1);
         return 0;
diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c
index 6a10238d2c63..1bc74b6f26d2 100644
--- a/fs/jbd2/commit.c
+++ b/fs/jbd2/commit.c
@@ -259,6 +259,7 @@ static int journal_submit_data_buffers(journal_t *journal,
                         ret = err;
                 spin_lock(&journal->j_list_lock);
                 J_ASSERT(jinode->i_transaction == commit_transaction);
+                commit_transaction->t_flushed_data_blocks = 1;
                 jinode->i_flags &= ~JI_COMMIT_RUNNING;
                 wake_up_bit(&jinode->i_flags, __JI_COMMIT_RUNNING);
         }
@@ -708,8 +709,17 @@ start_journal_io:
                 }
         }
 
-        /* Done it all: now write the commit record asynchronously. */
+        /* 
+         * If the journal is not located on the file system device,
+         * then we must flush the file system device before we issue
+         * the commit record
+         */
+        if (commit_transaction->t_flushed_data_blocks &&
+            (journal->j_fs_dev != journal->j_dev) &&
+            (journal->j_flags & JBD2_BARRIER))
+                blkdev_issue_flush(journal->j_fs_dev, NULL);
 
+        /* Done it all: now write the commit record asynchronously. */
         if (JBD2_HAS_INCOMPAT_FEATURE(journal,
                                       JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT)) {
                 err = journal_submit_commit_record(journal, commit_transaction,
@@ -720,13 +730,6 @@ start_journal_io:
                         blkdev_issue_flush(journal->j_dev, NULL);
         }
 
-        /*
-         * This is the right place to wait for data buffers both for ASYNC
-         * and !ASYNC commit. If commit is ASYNC, we need to wait only after
-         * the commit block went to disk (which happens above). If commit is
-         * SYNC, we need to wait for data buffers before we start writing
-         * commit block, which happens below in such setting.
-         */
         err = journal_finish_inode_data_buffers(journal, commit_transaction);
         if (err) {
                 printk(KERN_WARNING