1 files changed, 35 insertions, 34 deletions

diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
index 3eec82d32fd4..2d7109414cdd 100644
--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -30,6 +30,7 @@
 #include <linux/module.h>
 
 static void __jbd2_journal_temp_unlink_buffer(struct journal_head *jh);
+static void __jbd2_journal_unfile_buffer(struct journal_head *jh);
 
 /*
  * jbd2_get_transaction: obtain a new transaction_t object.
@@ -764,7 +765,6 @@ repeat:
         if (!jh->b_transaction) {
                 JBUFFER_TRACE(jh, "no transaction");
                 J_ASSERT_JH(jh, !jh->b_next_transaction);
-                jh->b_transaction = transaction;
                 JBUFFER_TRACE(jh, "file as BJ_Reserved");
                 spin_lock(&journal->j_list_lock);
                 __jbd2_journal_file_buffer(jh, transaction, BJ_Reserved);
@@ -814,7 +814,6 @@ out:
  * int jbd2_journal_get_write_access() - notify intent to modify a buffer for metadata (not data) update.
  * @handle: transaction to add buffer modifications to
  * @bh:     bh to be used for metadata writes
- * @credits: variable that will receive credits for the buffer
  *
  * Returns an error code or 0 on success.
  *
@@ -896,8 +895,6 @@ int jbd2_journal_get_create_access(handle_t *handle, struct buffer_head *bh)
                  * committed and so it's safe to clear the dirty bit.
                  */
                 clear_buffer_dirty(jh2bh(jh));
-                jh->b_transaction = transaction;
-
                 /* first access by this transaction */
                 jh->b_modified = 0;
 
@@ -932,7 +929,6 @@ out:
  *     non-rewindable consequences
  * @handle: transaction
  * @bh: buffer to undo
- * @credits: store the number of taken credits here (if not NULL)
  *
  * Sometimes there is a need to distinguish between metadata which has
  * been committed to disk and that which has not.  The ext3fs code uses
@@ -1232,8 +1228,6 @@ int jbd2_journal_forget (handle_t *handle, struct buffer_head *bh)
                         __jbd2_journal_file_buffer(jh, transaction, BJ_Forget);
                 } else {
                         __jbd2_journal_unfile_buffer(jh);
-                        jbd2_journal_remove_journal_head(bh);
-                        __brelse(bh);
                         if (!buffer_jbd(bh)) {
                                 spin_unlock(&journal->j_list_lock);
                                 jbd_unlock_bh_state(bh);
@@ -1556,19 +1550,32 @@ void __jbd2_journal_temp_unlink_buffer(struct journal_head *jh)
                 mark_buffer_dirty(bh);  /* Expose it to the VM */
 }
 
-void __jbd2_journal_unfile_buffer(struct journal_head *jh)
+/*
+ * Remove buffer from all transactions.
+ *
+ * Called with bh_state lock and j_list_lock
+ *
+ * jh and bh may be already freed when this function returns.
+ */
+static void __jbd2_journal_unfile_buffer(struct journal_head *jh)
 {
         __jbd2_journal_temp_unlink_buffer(jh);
         jh->b_transaction = NULL;
+        jbd2_journal_put_journal_head(jh);
 }
 
 void jbd2_journal_unfile_buffer(journal_t *journal, struct journal_head *jh)
 {
-        jbd_lock_bh_state(jh2bh(jh));
+        struct buffer_head *bh = jh2bh(jh);
+
+        /* Get reference so that buffer cannot be freed before we unlock it */
+        get_bh(bh);
+        jbd_lock_bh_state(bh);
         spin_lock(&journal->j_list_lock);
         __jbd2_journal_unfile_buffer(jh);
         spin_unlock(&journal->j_list_lock);
-        jbd_unlock_bh_state(jh2bh(jh));
+        jbd_unlock_bh_state(bh);
+        __brelse(bh);
 }
 
 /*
@@ -1595,8 +1602,6 @@ __journal_try_to_free_buffer(journal_t *journal, struct buffer_head *bh)
                 if (jh->b_jlist == BJ_None) {
                         JBUFFER_TRACE(jh, "remove from checkpoint list");
                         __jbd2_journal_remove_checkpoint(jh);
-                        jbd2_journal_remove_journal_head(bh);
-                        __brelse(bh);
                 }
         }
         spin_unlock(&journal->j_list_lock);
@@ -1659,7 +1664,6 @@ int jbd2_journal_try_to_free_buffers(journal_t *journal,
                 /*
                  * We take our own ref against the journal_head here to avoid
                  * having to add tons of locking around each instance of
-                 * jbd2_journal_remove_journal_head() and
                  * jbd2_journal_put_journal_head().
                  */
                 jh = jbd2_journal_grab_journal_head(bh);
@@ -1697,10 +1701,9 @@ static int __dispose_buffer(struct journal_head *jh, transaction_t *transaction)
         int may_free = 1;
         struct buffer_head *bh = jh2bh(jh);
 
-        __jbd2_journal_unfile_buffer(jh);
-
         if (jh->b_cp_transaction) {
                 JBUFFER_TRACE(jh, "on running+cp transaction");
+                __jbd2_journal_temp_unlink_buffer(jh);
                 /*
                  * We don't want to write the buffer anymore, clear the
                  * bit so that we don't confuse checks in
@@ -1711,8 +1714,7 @@ static int __dispose_buffer(struct journal_head *jh, transaction_t *transaction)
                 may_free = 0;
         } else {
                 JBUFFER_TRACE(jh, "on running transaction");
-                jbd2_journal_remove_journal_head(bh);
-                __brelse(bh);
+                __jbd2_journal_unfile_buffer(jh);
         }
         return may_free;
 }
@@ -1990,6 +1992,8 @@ void __jbd2_journal_file_buffer(struct journal_head *jh,
 
         if (jh->b_transaction)
                 __jbd2_journal_temp_unlink_buffer(jh);
+        else
+                jbd2_journal_grab_journal_head(bh);
         jh->b_transaction = transaction;
 
         switch (jlist) {
@@ -2041,9 +2045,10 @@ void jbd2_journal_file_buffer(struct journal_head *jh,
  * already started to be used by a subsequent transaction, refile the
  * buffer on that transaction's metadata list.
  *
- * Called under journal->j_list_lock
- *
+ * Called under j_list_lock
  * Called under jbd_lock_bh_state(jh2bh(jh))
+ *
+ * jh and bh may be already free when this function returns
  */
 void __jbd2_journal_refile_buffer(struct journal_head *jh)
 {
@@ -2067,6 +2072,11 @@ void __jbd2_journal_refile_buffer(struct journal_head *jh)
 
         was_dirty = test_clear_buffer_jbddirty(bh);
         __jbd2_journal_temp_unlink_buffer(jh);
+        /*
+         * We set b_transaction here because b_next_transaction will inherit
+         * our jh reference and thus __jbd2_journal_file_buffer() must not
+         * take a new one.
+         */
         jh->b_transaction = jh->b_next_transaction;
         jh->b_next_transaction = NULL;
         if (buffer_freed(bh))
@@ -2083,30 +2093,21 @@ void __jbd2_journal_refile_buffer(struct journal_head *jh)
 }
 
 /*
- * For the unlocked version of this call, also make sure that any
- * hanging journal_head is cleaned up if necessary.
- *
- * __jbd2_journal_refile_buffer is usually called as part of a single locked
- * operation on a buffer_head, in which the caller is probably going to
- * be hooking the journal_head onto other lists.  In that case it is up
- * to the caller to remove the journal_head if necessary.  For the
- * unlocked jbd2_journal_refile_buffer call, the caller isn't going to be
- * doing anything else to the buffer so we need to do the cleanup
- * ourselves to avoid a jh leak.
- *
- * *** The journal_head may be freed by this call! ***
+ * __jbd2_journal_refile_buffer() with necessary locking added. We take our
+ * bh reference so that we can safely unlock bh.
+ *
+ * The jh and bh may be freed by this call.
  */
 void jbd2_journal_refile_buffer(journal_t *journal, struct journal_head *jh)
 {
         struct buffer_head *bh = jh2bh(jh);
 
+        /* Get reference so that buffer cannot be freed before we unlock it */
+        get_bh(bh);
         jbd_lock_bh_state(bh);
         spin_lock(&journal->j_list_lock);
-
         __jbd2_journal_refile_buffer(jh);
         jbd_unlock_bh_state(bh);
-        jbd2_journal_remove_journal_head(bh);
-
         spin_unlock(&journal->j_list_lock);
         __brelse(bh);
 }