1 files changed, 55 insertions, 3 deletions

diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index e0ec3db1c395..9a7826990304 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -479,9 +479,12 @@ int __jbd2_log_space_left(journal_t *journal)
 int __jbd2_log_start_commit(journal_t *journal, tid_t target)
 {
         /*
-         * Are we already doing a recent enough commit?
+         * The only transaction we can possibly wait upon is the
+         * currently running transaction (if it exists).  Otherwise,
+         * the target tid must be an old one.
          */
-        if (!tid_geq(journal->j_commit_request, target)) {
+        if (journal->j_running_transaction &&
+            journal->j_running_transaction->t_tid == target) {
                 /*
                  * We want a new commit: OK, mark the request and wakeup the
                  * commit thread.  We do _not_ do the commit ourselves.
@@ -493,7 +496,15 @@ int __jbd2_log_start_commit(journal_t *journal, tid_t target)
                           journal->j_commit_sequence);
                 wake_up(&journal->j_wait_commit);
                 return 1;
-        }
+        } else if (!tid_geq(journal->j_commit_request, target))
+                /* This should never happen, but if it does, preserve
+                   the evidence before kjournald goes into a loop and
+                   increments j_commit_sequence beyond all recognition. */
+                WARN_ONCE(1, "jbd: bad log_start_commit: %u %u %u %u\n",
+                          journal->j_commit_request,
+                          journal->j_commit_sequence,
+                          target, journal->j_running_transaction ? 
+                          journal->j_running_transaction->t_tid : 0);
         return 0;
 }
 
@@ -577,6 +588,47 @@ int jbd2_journal_start_commit(journal_t *journal, tid_t *ptid)
 }
 
 /*
+ * Return 1 if a given transaction has not yet sent barrier request
+ * connected with a transaction commit. If 0 is returned, transaction
+ * may or may not have sent the barrier. Used to avoid sending barrier
+ * twice in common cases.
+ */
+int jbd2_trans_will_send_data_barrier(journal_t *journal, tid_t tid)
+{
+        int ret = 0;
+        transaction_t *commit_trans;
+
+        if (!(journal->j_flags & JBD2_BARRIER))
+                return 0;
+        read_lock(&journal->j_state_lock);
+        /* Transaction already committed? */
+        if (tid_geq(journal->j_commit_sequence, tid))
+                goto out;
+        commit_trans = journal->j_committing_transaction;
+        if (!commit_trans || commit_trans->t_tid != tid) {
+                ret = 1;
+                goto out;
+        }
+        /*
+         * Transaction is being committed and we already proceeded to
+         * submitting a flush to fs partition?
+         */
+        if (journal->j_fs_dev != journal->j_dev) {
+                if (!commit_trans->t_need_data_flush ||
+                    commit_trans->t_state >= T_COMMIT_DFLUSH)
+                        goto out;
+        } else {
+                if (commit_trans->t_state >= T_COMMIT_JFLUSH)
+                        goto out;
+        }
+        ret = 1;
+out:
+        read_unlock(&journal->j_state_lock);
+        return ret;
+}
+EXPORT_SYMBOL(jbd2_trans_will_send_data_barrier);
+
+/*
  * Wait for a specified commit to complete.
  * The caller may not hold the journal lock.
  */