1 files changed, 87 insertions, 0 deletions

diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index 8b3f5bbd65f9..7c52feb6f753 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -2051,6 +2051,91 @@ recovery_error:
 }
 
 /**
+ * jbd2_journal_shrink_scan()
+ *
+ * Scan the checkpointed buffer on the checkpoint list and release the
+ * journal_head.
+ */
+static unsigned long jbd2_journal_shrink_scan(struct shrinker *shrink,
+					      struct shrink_control *sc)
+{
+	journal_t *journal = container_of(shrink, journal_t, j_shrinker);
+	unsigned long nr_to_scan = sc->nr_to_scan;
+	unsigned long nr_shrunk;
+	unsigned long count;
+
+	count = percpu_counter_read_positive(&journal->j_jh_shrink_count);
+	trace_jbd2_shrink_scan_enter(journal, sc->nr_to_scan, count);
+
+	nr_shrunk = jbd2_journal_shrink_checkpoint_list(journal, &nr_to_scan);
+
+	count = percpu_counter_read_positive(&journal->j_jh_shrink_count);
+	trace_jbd2_shrink_scan_exit(journal, nr_to_scan, nr_shrunk, count);
+
+	return nr_shrunk;
+}
+
+/**
+ * jbd2_journal_shrink_count()
+ *
+ * Count the number of checkpoint buffers on the checkpoint list.
+ */
+static unsigned long jbd2_journal_shrink_count(struct shrinker *shrink,
+					       struct shrink_control *sc)
+{
+	journal_t *journal = container_of(shrink, journal_t, j_shrinker);
+	unsigned long count;
+
+	count = percpu_counter_read_positive(&journal->j_jh_shrink_count);
+	trace_jbd2_shrink_count(journal, sc->nr_to_scan, count);
+
+	return count;
+}
+
+/**
+ * jbd2_journal_register_shrinker()
+ * @journal: Journal to act on.
+ *
+ * Init a percpu counter to record the checkpointed buffers on the checkpoint
+ * list and register a shrinker to release their journal_head.
+ */
+int jbd2_journal_register_shrinker(journal_t *journal)
+{
+	int err;
+
+	journal->j_shrink_transaction = NULL;
+
+	err = percpu_counter_init(&journal->j_jh_shrink_count, 0, GFP_KERNEL);
+	if (err)
+		return err;
+
+	journal->j_shrinker.scan_objects = jbd2_journal_shrink_scan;
+	journal->j_shrinker.count_objects = jbd2_journal_shrink_count;
+	journal->j_shrinker.seeks = DEFAULT_SEEKS;
+	journal->j_shrinker.batch = journal->j_max_transaction_buffers;
+
+	err = register_shrinker(&journal->j_shrinker);
+	if (err) {
+		percpu_counter_destroy(&journal->j_jh_shrink_count);
+		return err;
+	}
+
+	return 0;
+}
+
+/**
+ * jbd2_journal_unregister_shrinker()
+ * @journal: Journal to act on.
+ *
+ * Unregister the checkpointed buffer shrinker and destroy the percpu counter.
+ */
+void jbd2_journal_unregister_shrinker(journal_t *journal)
+{
+	percpu_counter_destroy(&journal->j_jh_shrink_count);
+	unregister_shrinker(&journal->j_shrinker);
+}
+
+/**
  * jbd2_journal_destroy() - Release a journal_t structure.
  * @journal: Journal to act on.
  *
@@ -2122,6 +2207,8 @@ int jbd2_journal_destroy(journal_t *journal)
 		brelse(journal->j_sb_buffer);
 	}
 
+	jbd2_journal_unregister_shrinker(journal);
+
 	if (journal->j_proc_entry)
 		jbd2_stats_proc_exit(journal);
 	iput(journal->j_inode);