jbd2: optimize jbd2_journal_force_commit

Current implementation of jbd2_journal_force_commit() is suboptimal because
result in empty and useless commits. But callers just want to force and wait
any unfinished commits. We already have jbd2_journal_force_commit_nested()
which does exactly what we want, except we are guaranteed that we do not hold
journal transaction open.

Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

2 files changed, 48 insertions, 37 deletions

diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index 70990d682a0c..0e6c13bdcc14 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -529,20 +529,17 @@ int jbd2_log_start_commit(journal_t *journal, tid_t tid)
 }
 
 /*
- * Force and wait upon a commit if the calling process is not within
- * transaction.  This is used for forcing out undo-protected data which contains
- * bitmaps, when the fs is running out of space.
- *
- * We can only force the running transaction if we don't have an active handle;
- * otherwise, we will deadlock.
- *
- * Returns true if a transaction was started.
+ * Force and wait any uncommitted transactions.  We can only force the running
+ * transaction if we don't have an active handle, otherwise, we will deadlock.
+ * Returns: <0 in case of error,
+ *           0 if nothing to commit,
+ *           1 if transaction was successfully committed.
  */
-int jbd2_journal_force_commit_nested(journal_t *journal)
+static int __jbd2_journal_force_commit(journal_t *journal)
 {
         transaction_t *transaction = NULL;
         tid_t tid;
-        int need_to_start = 0;
+        int need_to_start = 0, ret = 0;
 
         read_lock(&journal->j_state_lock);
         if (journal->j_running_transaction && !current->journal_info) {
@@ -553,16 +550,53 @@ int jbd2_journal_force_commit_nested(journal_t *journal)
                 transaction = journal->j_committing_transaction;
 
         if (!transaction) {
+                /* Nothing to commit */
                 read_unlock(&journal->j_state_lock);
-                return 0;       /* Nothing to retry */
+                return 0;
         }
-
         tid = transaction->t_tid;
         read_unlock(&journal->j_state_lock);
         if (need_to_start)
                 jbd2_log_start_commit(journal, tid);
-        jbd2_log_wait_commit(journal, tid);
-        return 1;
+        ret = jbd2_log_wait_commit(journal, tid);
+        if (!ret)
+                ret = 1;
+
+        return ret;
+}
+
+/**
+ * Force and wait upon a commit if the calling process is not within
+ * transaction.  This is used for forcing out undo-protected data which contains
+ * bitmaps, when the fs is running out of space.
+ *
+ * @journal: journal to force
+ * Returns true if progress was made.
+ */
+int jbd2_journal_force_commit_nested(journal_t *journal)
+{
+        int ret;
+
+        ret = __jbd2_journal_force_commit(journal);
+        return ret > 0;
+}
+
+/**
+ * int journal_force_commit() - force any uncommitted transactions
+ * @journal: journal to force
+ *
+ * Caller want unconditional commit. We can only force the running transaction
+ * if we don't have an active handle, otherwise, we will deadlock.
+ */
+int jbd2_journal_force_commit(journal_t *journal)
+{
+        int ret;
+
+        J_ASSERT(!current->journal_info);
+        ret = __jbd2_journal_force_commit(journal);
+        if (ret > 0)
+                ret = 0;
+        return ret;
 }
 
 /*
diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
index f33342a2a95e..dd422e680418 100644
--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -1661,29 +1661,6 @@ int jbd2_journal_stop(handle_t *handle)
         return err;
 }
 
-/**
- * int jbd2_journal_force_commit() - force any uncommitted transactions
- * @journal: journal to force
- *
- * For synchronous operations: force any uncommitted transactions
- * to disk.  May seem kludgy, but it reuses all the handle batching
- * code in a very simple manner.
- */
-int jbd2_journal_force_commit(journal_t *journal)
-{
-        handle_t *handle;
-        int ret;
-
-        handle = jbd2_journal_start(journal, 1);
-        if (IS_ERR(handle)) {
-                ret = PTR_ERR(handle);
-        } else {
-                handle->h_sync = 1;
-                ret = jbd2_journal_stop(handle);
-        }
-        return ret;
-}
-
 /*
  *
  * List management code snippets: various functions for manipulating the