1 files changed, 16 insertions, 12 deletions

diff --git a/fs/jbd2/checkpoint.c b/fs/jbd2/checkpoint.c
index 6a79fd0a1a32..2c62c5aae82f 100644
--- a/fs/jbd2/checkpoint.c
+++ b/fs/jbd2/checkpoint.c
@@ -97,10 +97,14 @@ static int __try_to_free_cp_buf(struct journal_head *jh)
 
         if (jh->b_jlist == BJ_None && !buffer_locked(bh) &&
             !buffer_dirty(bh) && !buffer_write_io_error(bh)) {
+                /*
+                 * Get our reference so that bh cannot be freed before
+                 * we unlock it
+                 */
+                get_bh(bh);
                 JBUFFER_TRACE(jh, "remove from checkpoint list");
                 ret = __jbd2_journal_remove_checkpoint(jh) + 1;
                 jbd_unlock_bh_state(bh);
-                jbd2_journal_remove_journal_head(bh);
                 BUFFER_TRACE(bh, "release");
                 __brelse(bh);
         } else {
@@ -223,8 +227,8 @@ restart:
                         spin_lock(&journal->j_list_lock);
                         goto restart;
                 }
+                get_bh(bh);
                 if (buffer_locked(bh)) {
-                        atomic_inc(&bh->b_count);
                         spin_unlock(&journal->j_list_lock);
                         jbd_unlock_bh_state(bh);
                         wait_on_buffer(bh);
@@ -243,7 +247,6 @@ restart:
                  */
                 released = __jbd2_journal_remove_checkpoint(jh);
                 jbd_unlock_bh_state(bh);
-                jbd2_journal_remove_journal_head(bh);
                 __brelse(bh);
         }
 
@@ -284,7 +287,7 @@ static int __process_buffer(journal_t *journal, struct journal_head *jh,
         int ret = 0;
 
         if (buffer_locked(bh)) {
-                atomic_inc(&bh->b_count);
+                get_bh(bh);
                 spin_unlock(&journal->j_list_lock);
                 jbd_unlock_bh_state(bh);
                 wait_on_buffer(bh);
@@ -316,12 +319,12 @@ static int __process_buffer(journal_t *journal, struct journal_head *jh,
                 ret = 1;
                 if (unlikely(buffer_write_io_error(bh)))
                         ret = -EIO;
+                get_bh(bh);
                 J_ASSERT_JH(jh, !buffer_jbddirty(bh));
                 BUFFER_TRACE(bh, "remove from checkpoint");
                 __jbd2_journal_remove_checkpoint(jh);
                 spin_unlock(&journal->j_list_lock);
                 jbd_unlock_bh_state(bh);
-                jbd2_journal_remove_journal_head(bh);
                 __brelse(bh);
         } else {
                 /*
@@ -554,7 +557,8 @@ int jbd2_cleanup_journal_tail(journal_t *journal)
 /*
  * journal_clean_one_cp_list
  *
- * Find all the written-back checkpoint buffers in the given list and release them.
+ * Find all the written-back checkpoint buffers in the given list and
+ * release them.
  *
  * Called with the journal locked.
  * Called with j_list_lock held.
@@ -663,8 +667,8 @@ out:
  * checkpoint lists.
  *
  * The function returns 1 if it frees the transaction, 0 otherwise.
+ * The function can free jh and bh.
  *
- * This function is called with the journal locked.
  * This function is called with j_list_lock held.
  * This function is called with jbd_lock_bh_state(jh2bh(jh))
  */
@@ -684,13 +688,14 @@ int __jbd2_journal_remove_checkpoint(struct journal_head *jh)
         }
         journal = transaction->t_journal;
 
+        JBUFFER_TRACE(jh, "removing from transaction");
         __buffer_unlink(jh);
         jh->b_cp_transaction = NULL;
+        jbd2_journal_put_journal_head(jh);
 
         if (transaction->t_checkpoint_list != NULL ||
             transaction->t_checkpoint_io_list != NULL)
                 goto out;
-        JBUFFER_TRACE(jh, "transaction has no more buffers");
 
         /*
          * There is one special case to worry about: if we have just pulled the
@@ -701,10 +706,8 @@ int __jbd2_journal_remove_checkpoint(struct journal_head *jh)
          * The locking here around t_state is a bit sleazy.
          * See the comment at the end of jbd2_journal_commit_transaction().
          */
-        if (transaction->t_state != T_FINISHED) {
-                JBUFFER_TRACE(jh, "belongs to running/committing transaction");
+        if (transaction->t_state != T_FINISHED)
                 goto out;
-        }
 
         /* OK, that was the last buffer for the transaction: we can now
            safely remove this transaction from the log */
@@ -723,7 +726,6 @@ int __jbd2_journal_remove_checkpoint(struct journal_head *jh)
         wake_up(&journal->j_wait_logspace);
         ret = 1;
 out:
-        JBUFFER_TRACE(jh, "exit");
         return ret;
 }
 
@@ -742,6 +744,8 @@ void __jbd2_journal_insert_checkpoint(struct journal_head *jh,
         J_ASSERT_JH(jh, buffer_dirty(jh2bh(jh)) || buffer_jbddirty(jh2bh(jh)));
         J_ASSERT_JH(jh, jh->b_cp_transaction == NULL);
 
+        /* Get reference for checkpointing transaction */
+        jbd2_journal_grab_journal_head(jh2bh(jh));
         jh->b_cp_transaction = transaction;
 
         if (!transaction->t_checkpoint_list) {