[PATCH 3.2 106/107] jbd2: avoid infinite loop when destroying aborted journal

[Ben Hutchings <ben@decadent.org.uk>]

3.2.72-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Jan Kara <jack@suse.com>

commit 841df7df196237ea63233f0f9eaa41db53afd70f upstream.

Commit 6f6a6fda2945 "jbd2: fix ocfs2 corrupt when updating journal
superblock fails" changed jbd2_cleanup_journal_tail() to return EIO
when the journal is aborted. That makes logic in
jbd2_log_do_checkpoint() bail out which is fine, except that
jbd2_journal_destroy() expects jbd2_log_do_checkpoint() to always make
a progress in cleaning the journal. Without it jbd2_journal_destroy()
just loops in an infinite loop.

Fix jbd2_journal_destroy() to cleanup journal checkpoint lists of
jbd2_log_do_checkpoint() fails with error.

Reported-by: Eryu Guan <guaneryu@gmail.com>
Tested-by: Eryu Guan <guaneryu@gmail.com>
Fixes: 6f6a6fda294506dfe0e3e0a253bb2d2923f28f0a
Signed-off-by: Jan Kara <jack@suse.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Cc: Roland Dreier <roland@kernel.org>
---
--- a/fs/jbd2/checkpoint.c
+++ b/fs/jbd2/checkpoint.c
@@ -509,14 +509,15 @@ int jbd2_cleanup_journal_tail(journal_t
  * journal_clean_one_cp_list
  *
  * Find all the written-back checkpoint buffers in the given list and
- * release them.
+ * release them. If 'destroy' is set, clean all buffers unconditionally.
  *
  * Called with the journal locked.
  * Called with j_list_lock held.
  * Returns number of bufers reaped (for debug)
  */
 
-static int journal_clean_one_cp_list(struct journal_head *jh, int *released)
+static int journal_clean_one_cp_list(struct journal_head *jh, bool destroy,
+				     int *released)
 {
 	struct journal_head *last_jh;
 	struct journal_head *next_jh = jh;
@@ -532,7 +533,10 @@ static int journal_clean_one_cp_list(str
 		next_jh = jh->b_cpnext;
 		/* Use trylock because of the ranking */
 		if (jbd_trylock_bh_state(jh2bh(jh))) {
-			ret = __try_to_free_cp_buf(jh);
+			if (!destroy)
+				ret = __try_to_free_cp_buf(jh);
+			else
+				ret = __jbd2_journal_remove_checkpoint(jh) + 1;
 			if (ret) {
 				freed++;
 				if (ret == 2) {
@@ -558,13 +562,14 @@ static int journal_clean_one_cp_list(str
  * journal_clean_checkpoint_list
  *
  * Find all the written-back checkpoint buffers in the journal and release them.
+ * If 'destroy' is set, release all buffers unconditionally.
  *
  * Called with the journal locked.
  * Called with j_list_lock held.
  * Returns number of buffers reaped (for debug)
  */
 
-int __jbd2_journal_clean_checkpoint_list(journal_t *journal)
+int __jbd2_journal_clean_checkpoint_list(journal_t *journal, bool destroy)
 {
 	transaction_t *transaction, *last_transaction, *next_transaction;
 	int ret = 0;
@@ -580,7 +585,7 @@ int __jbd2_journal_clean_checkpoint_list
 		transaction = next_transaction;
 		next_transaction = transaction->t_cpnext;
 		ret += journal_clean_one_cp_list(transaction->
-				t_checkpoint_list, &released);
+				t_checkpoint_list, destroy, &released);
 		/*
 		 * This function only frees up some memory if possible so we
 		 * dont have an obligation to finish processing. Bail out if
@@ -596,7 +601,7 @@ int __jbd2_journal_clean_checkpoint_list
 		 * we can possibly see not yet submitted buffers on io_list
 		 */
 		ret += journal_clean_one_cp_list(transaction->
-				t_checkpoint_io_list, &released);
+				t_checkpoint_io_list, destroy, &released);
 		if (need_resched())
 			goto out;
 	} while (transaction != last_transaction);
@@ -605,6 +610,28 @@ out:
 }
 
 /*
+ * Remove buffers from all checkpoint lists as journal is aborted and we just
+ * need to free memory
+ */
+void jbd2_journal_destroy_checkpoint(journal_t *journal)
+{
+	/*
+	 * We loop because __jbd2_journal_clean_checkpoint_list() may abort
+	 * early due to a need of rescheduling.
+	 */
+	while (1) {
+		spin_lock(&journal->j_list_lock);
+		if (!journal->j_checkpoint_transactions) {
+			spin_unlock(&journal->j_list_lock);
+			break;
+		}
+		__jbd2_journal_clean_checkpoint_list(journal, true);
+		spin_unlock(&journal->j_list_lock);
+		cond_resched();
+	}
+}
+
+/*
  * journal_remove_checkpoint: called after a buffer has been committed
  * to disk (either by being write-back flushed to disk, or being
  * committed to the log).
--- a/fs/jbd2/commit.c
+++ b/fs/jbd2/commit.c
@@ -435,7 +435,7 @@ void jbd2_journal_commit_transaction(jou
 	 * frees some memory
 	 */
 	spin_lock(&journal->j_list_lock);
-	__jbd2_journal_clean_checkpoint_list(journal);
+	__jbd2_journal_clean_checkpoint_list(journal, false);
 	spin_unlock(&journal->j_list_lock);
 
 	jbd_debug(3, "JBD2: commit phase 1\n");
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -1571,8 +1571,17 @@ int jbd2_journal_destroy(journal_t *jour
 	while (journal->j_checkpoint_transactions != NULL) {
 		spin_unlock(&journal->j_list_lock);
 		mutex_lock(&journal->j_checkpoint_mutex);
-		jbd2_log_do_checkpoint(journal);
+		err = jbd2_log_do_checkpoint(journal);
 		mutex_unlock(&journal->j_checkpoint_mutex);
+		/*
+		 * If checkpointing failed, just free the buffers to avoid
+		 * looping forever
+		 */
+		if (err) {
+			jbd2_journal_destroy_checkpoint(journal);
+			spin_lock(&journal->j_list_lock);
+			break;
+		}
 		spin_lock(&journal->j_list_lock);
 	}
 
--- a/include/linux/jbd2.h
+++ b/include/linux/jbd2.h
@@ -980,8 +980,9 @@ int __jbd2_update_log_tail(journal_t *jo
 extern void jbd2_journal_commit_transaction(journal_t *);
 
 /* Checkpoint list management */
-int __jbd2_journal_clean_checkpoint_list(journal_t *journal);
+int __jbd2_journal_clean_checkpoint_list(journal_t *journal, bool destroy);
 int __jbd2_journal_remove_checkpoint(struct journal_head *);
+void jbd2_journal_destroy_checkpoint(journal_t *journal);
 void __jbd2_journal_insert_checkpoint(struct journal_head *, transaction_t *);