jbd2: Use tracepoints for history file

The /proc/fs/jbd2/<dev>/history was maintained manually; by using
tracepoints, we can get all of the existing functionality of the /proc
file plus extra capabilities thanks to the ftrace infrastructure.  We
save memory as a bonus.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

fs/jbd2/checkpoint.c

@@ -643,6 +643,7 @@ int __jbd2_journal_clean_checkpoint_list(journal_t *journal)
 
 int __jbd2_journal_remove_checkpoint(struct journal_head *jh)
 {
+	struct transaction_chp_stats_s *stats;
 	transaction_t *transaction;
 	journal_t *journal;
 	int ret = 0;
@@ -679,6 +680,12 @@ int __jbd2_journal_remove_checkpoint(struct journal_head *jh)
 
 	/* OK, that was the last buffer for the transaction: we can now
 	   safely remove this transaction from the log */
+	stats = &transaction->t_chp_stats;
+	if (stats->cs_chp_time)
+		stats->cs_chp_time = jbd2_time_diff(stats->cs_chp_time,
+						    jiffies);
+	trace_jbd2_checkpoint_stats(journal->j_fs_dev->bd_dev,
+				    transaction->t_tid, stats);
 
 	__jbd2_journal_drop_transaction(journal, transaction);
 	kfree(transaction);

fs/jbd2/commit.c

@@ -410,10 +410,10 @@ void jbd2_journal_commit_transaction(journal_t *journal)
 	if (commit_transaction->t_synchronous_commit)
 		write_op = WRITE_SYNC_PLUG;
 	trace_jbd2_commit_locking(journal, commit_transaction);
-	stats.u.run.rs_wait = commit_transaction->t_max_wait;
-	stats.u.run.rs_locked = jiffies;
-	stats.u.run.rs_running = jbd2_time_diff(commit_transaction->t_start,
-						stats.u.run.rs_locked);
+	stats.run.rs_wait = commit_transaction->t_max_wait;
+	stats.run.rs_locked = jiffies;
+	stats.run.rs_running = jbd2_time_diff(commit_transaction->t_start,
+					      stats.run.rs_locked);
 
 	spin_lock(&commit_transaction->t_handle_lock);
 	while (commit_transaction->t_updates) {
@@ -486,9 +486,9 @@ void jbd2_journal_commit_transaction(journal_t *journal)
 	jbd2_journal_switch_revoke_table(journal);
 
 	trace_jbd2_commit_flushing(journal, commit_transaction);
-	stats.u.run.rs_flushing = jiffies;
-	stats.u.run.rs_locked = jbd2_time_diff(stats.u.run.rs_locked,
-					       stats.u.run.rs_flushing);
+	stats.run.rs_flushing = jiffies;
+	stats.run.rs_locked = jbd2_time_diff(stats.run.rs_locked,
+					     stats.run.rs_flushing);
 
 	commit_transaction->t_state = T_FLUSH;
 	journal->j_committing_transaction = commit_transaction;
@@ -523,11 +523,11 @@ void jbd2_journal_commit_transaction(journal_t *journal)
 	spin_unlock(&journal->j_state_lock);
 
 	trace_jbd2_commit_logging(journal, commit_transaction);
-	stats.u.run.rs_logging = jiffies;
-	stats.u.run.rs_flushing = jbd2_time_diff(stats.u.run.rs_flushing,
-						 stats.u.run.rs_logging);
-	stats.u.run.rs_blocks = commit_transaction->t_outstanding_credits;
-	stats.u.run.rs_blocks_logged = 0;
+	stats.run.rs_logging = jiffies;
+	stats.run.rs_flushing = jbd2_time_diff(stats.run.rs_flushing,
+					       stats.run.rs_logging);
+	stats.run.rs_blocks = commit_transaction->t_outstanding_credits;
+	stats.run.rs_blocks_logged = 0;
 
 	J_ASSERT(commit_transaction->t_nr_buffers <=
 		 commit_transaction->t_outstanding_credits);
@@ -695,7 +695,7 @@ void jbd2_journal_commit_transaction(journal_t *journal)
 				submit_bh(write_op, bh);
 			}
 			cond_resched();
-			stats.u.run.rs_blocks_logged += bufs;
+			stats.run.rs_blocks_logged += bufs;
 
 			/* Force a new descriptor to be generated next
                            time round the loop. */
@@ -988,33 +988,30 @@ void jbd2_journal_commit_transaction(journal_t *journal)
 	J_ASSERT(commit_transaction->t_state == T_COMMIT);
 
 	commit_transaction->t_start = jiffies;
-	stats.u.run.rs_logging = jbd2_time_diff(stats.u.run.rs_logging,
+	stats.run.rs_logging = jbd2_time_diff(stats.run.rs_logging,
 					      commit_transaction->t_start);
 
 	/*
-	 * File the transaction for history
+	 * File the transaction statistics
 	 */
-	stats.ts_type = JBD2_STATS_RUN;
 	stats.ts_tid = commit_transaction->t_tid;
-	stats.u.run.rs_handle_count = commit_transaction->t_handle_count;
-	spin_lock(&journal->j_history_lock);
-	memcpy(journal->j_history + journal->j_history_cur, &stats,
-			sizeof(stats));
-	if (++journal->j_history_cur == journal->j_history_max)
-		journal->j_history_cur = 0;
+	stats.run.rs_handle_count = commit_transaction->t_handle_count;
+	trace_jbd2_run_stats(journal->j_fs_dev->bd_dev,
+			     commit_transaction->t_tid, &stats.run);
 
 	/*
 	 * Calculate overall stats
 	 */
+	spin_lock(&journal->j_history_lock);
 	journal->j_stats.ts_tid++;
-	journal->j_stats.u.run.rs_wait += stats.u.run.rs_wait;
-	journal->j_stats.u.run.rs_running += stats.u.run.rs_running;
-	journal->j_stats.u.run.rs_locked += stats.u.run.rs_locked;
-	journal->j_stats.u.run.rs_flushing += stats.u.run.rs_flushing;
-	journal->j_stats.u.run.rs_logging += stats.u.run.rs_logging;
-	journal->j_stats.u.run.rs_handle_count += stats.u.run.rs_handle_count;
-	journal->j_stats.u.run.rs_blocks += stats.u.run.rs_blocks;
-	journal->j_stats.u.run.rs_blocks_logged += stats.u.run.rs_blocks_logged;
+	journal->j_stats.run.rs_wait += stats.run.rs_wait;
+	journal->j_stats.run.rs_running += stats.run.rs_running;
+	journal->j_stats.run.rs_locked += stats.run.rs_locked;
+	journal->j_stats.run.rs_flushing += stats.run.rs_flushing;
+	journal->j_stats.run.rs_logging += stats.run.rs_logging;
+	journal->j_stats.run.rs_handle_count += stats.run.rs_handle_count;
+	journal->j_stats.run.rs_blocks += stats.run.rs_blocks;
+	journal->j_stats.run.rs_blocks_logged += stats.run.rs_blocks_logged;
 	spin_unlock(&journal->j_history_lock);
 
 	commit_transaction->t_state = T_FINISHED;

fs/jbd2/journal.c

@@ -676,153 +676,6 @@ struct jbd2_stats_proc_session {
 	int max;
 };
 
-static void *jbd2_history_skip_empty(struct jbd2_stats_proc_session *s,
-					struct transaction_stats_s *ts,
-					int first)
-{
-	if (ts == s->stats + s->max)
-		ts = s->stats;
-	if (!first && ts == s->stats + s->start)
-		return NULL;
-	while (ts->ts_type == 0) {
-		ts++;
-		if (ts == s->stats + s->max)
-			ts = s->stats;
-		if (ts == s->stats + s->start)
-			return NULL;
-	}
-	return ts;
-
-}
-
-static void *jbd2_seq_history_start(struct seq_file *seq, loff_t *pos)
-{
-	struct jbd2_stats_proc_session *s = seq->private;
-	struct transaction_stats_s *ts;
-	int l = *pos;
-
-	if (l == 0)
-		return SEQ_START_TOKEN;
-	ts = jbd2_history_skip_empty(s, s->stats + s->start, 1);
-	if (!ts)
-		return NULL;
-	l--;
-	while (l) {
-		ts = jbd2_history_skip_empty(s, ++ts, 0);
-		if (!ts)
-			break;
-		l--;
-	}
-	return ts;
-}
-
-static void *jbd2_seq_history_next(struct seq_file *seq, void *v, loff_t *pos)
-{
-	struct jbd2_stats_proc_session *s = seq->private;
-	struct transaction_stats_s *ts = v;
-
-	++*pos;
-	if (v == SEQ_START_TOKEN)
-		return jbd2_history_skip_empty(s, s->stats + s->start, 1);
-	else
-		return jbd2_history_skip_empty(s, ++ts, 0);
-}
-
-static int jbd2_seq_history_show(struct seq_file *seq, void *v)
-{
-	struct transaction_stats_s *ts = v;
-	if (v == SEQ_START_TOKEN) {
-		seq_printf(seq, "%-4s %-5s %-5s %-5s %-5s %-5s %-5s %-6s %-5s "
-				"%-5s %-5s %-5s %-5s %-5s\n", "R/C", "tid",
-				"wait", "run", "lock", "flush", "log", "hndls",
-				"block", "inlog", "ctime", "write", "drop",
-				"close");
-		return 0;
-	}
-	if (ts->ts_type == JBD2_STATS_RUN)
-		seq_printf(seq, "%-4s %-5lu %-5u %-5u %-5u %-5u %-5u "
-				"%-6lu %-5lu %-5lu\n", "R", ts->ts_tid,
-				jiffies_to_msecs(ts->u.run.rs_wait),
-				jiffies_to_msecs(ts->u.run.rs_running),
-				jiffies_to_msecs(ts->u.run.rs_locked),
-				jiffies_to_msecs(ts->u.run.rs_flushing),
-				jiffies_to_msecs(ts->u.run.rs_logging),
-				ts->u.run.rs_handle_count,
-				ts->u.run.rs_blocks,
-				ts->u.run.rs_blocks_logged);
-	else if (ts->ts_type == JBD2_STATS_CHECKPOINT)
-		seq_printf(seq, "%-4s %-5lu %48s %-5u %-5lu %-5lu %-5lu\n",
-				"C", ts->ts_tid, " ",
-				jiffies_to_msecs(ts->u.chp.cs_chp_time),
-				ts->u.chp.cs_written, ts->u.chp.cs_dropped,
-				ts->u.chp.cs_forced_to_close);
-	else
-		J_ASSERT(0);
-	return 0;
-}
-
-static void jbd2_seq_history_stop(struct seq_file *seq, void *v)
-{
-}
-
-static const struct seq_operations jbd2_seq_history_ops = {
-	.start  = jbd2_seq_history_start,
-	.next   = jbd2_seq_history_next,
-	.stop   = jbd2_seq_history_stop,
-	.show   = jbd2_seq_history_show,
-};
-
-static int jbd2_seq_history_open(struct inode *inode, struct file *file)
-{
-	journal_t *journal = PDE(inode)->data;
-	struct jbd2_stats_proc_session *s;
-	int rc, size;
-
-	s = kmalloc(sizeof(*s), GFP_KERNEL);
-	if (s == NULL)
-		return -ENOMEM;
-	size = sizeof(struct transaction_stats_s) * journal->j_history_max;
-	s->stats = kmalloc(size, GFP_KERNEL);
-	if (s->stats == NULL) {
-		kfree(s);
-		return -ENOMEM;
-	}
-	spin_lock(&journal->j_history_lock);
-	memcpy(s->stats, journal->j_history, size);
-	s->max = journal->j_history_max;
-	s->start = journal->j_history_cur % s->max;
-	spin_unlock(&journal->j_history_lock);
-
-	rc = seq_open(file, &jbd2_seq_history_ops);
-	if (rc == 0) {
-		struct seq_file *m = file->private_data;
-		m->private = s;
-	} else {
-		kfree(s->stats);
-		kfree(s);
-	}
-	return rc;
-
-}
-
-static int jbd2_seq_history_release(struct inode *inode, struct file *file)
-{
-	struct seq_file *seq = file->private_data;
-	struct jbd2_stats_proc_session *s = seq->private;
-
-	kfree(s->stats);
-	kfree(s);
-	return seq_release(inode, file);
-}
-
-static struct file_operations jbd2_seq_history_fops = {
-	.owner		= THIS_MODULE,
-	.open           = jbd2_seq_history_open,
-	.read           = seq_read,
-	.llseek         = seq_lseek,
-	.release        = jbd2_seq_history_release,
-};
-
 static void *jbd2_seq_info_start(struct seq_file *seq, loff_t *pos)
 {
 	return *pos ? NULL : SEQ_START_TOKEN;
@@ -839,29 +692,29 @@ static int jbd2_seq_info_show(struct seq_file *seq, void *v)
 
 	if (v != SEQ_START_TOKEN)
 		return 0;
-	seq_printf(seq, "%lu transaction, each upto %u blocks\n",
+	seq_printf(seq, "%lu transaction, each up to %u blocks\n",
 			s->stats->ts_tid,
 			s->journal->j_max_transaction_buffers);
 	if (s->stats->ts_tid == 0)
 		return 0;
 	seq_printf(seq, "average: \n  %ums waiting for transaction\n",
-	    jiffies_to_msecs(s->stats->u.run.rs_wait / s->stats->ts_tid));
+	    jiffies_to_msecs(s->stats->run.rs_wait / s->stats->ts_tid));
 	seq_printf(seq, "  %ums running transaction\n",
-	    jiffies_to_msecs(s->stats->u.run.rs_running / s->stats->ts_tid));
+	    jiffies_to_msecs(s->stats->run.rs_running / s->stats->ts_tid));
 	seq_printf(seq, "  %ums transaction was being locked\n",
-	    jiffies_to_msecs(s->stats->u.run.rs_locked / s->stats->ts_tid));
+	    jiffies_to_msecs(s->stats->run.rs_locked / s->stats->ts_tid));
 	seq_printf(seq, "  %ums flushing data (in ordered mode)\n",
-	    jiffies_to_msecs(s->stats->u.run.rs_flushing / s->stats->ts_tid));
+	    jiffies_to_msecs(s->stats->run.rs_flushing / s->stats->ts_tid));
 	seq_printf(seq, "  %ums logging transaction\n",
-	    jiffies_to_msecs(s->stats->u.run.rs_logging / s->stats->ts_tid));
+	    jiffies_to_msecs(s->stats->run.rs_logging / s->stats->ts_tid));
 	seq_printf(seq, "  %lluus average transaction commit time\n",
 		   div_u64(s->journal->j_average_commit_time, 1000));
 	seq_printf(seq, "  %lu handles per transaction\n",
-	    s->stats->u.run.rs_handle_count / s->stats->ts_tid);
+	    s->stats->run.rs_handle_count / s->stats->ts_tid);
 	seq_printf(seq, "  %lu blocks per transaction\n",
-	    s->stats->u.run.rs_blocks / s->stats->ts_tid);
+	    s->stats->run.rs_blocks / s->stats->ts_tid);
 	seq_printf(seq, "  %lu logged blocks per transaction\n",
-	    s->stats->u.run.rs_blocks_logged / s->stats->ts_tid);
+	    s->stats->run.rs_blocks_logged / s->stats->ts_tid);
 	return 0;
 }
 
@@ -931,8 +784,6 @@ static void jbd2_stats_proc_init(journal_t *journal)
 {
 	journal->j_proc_entry = proc_mkdir(journal->j_devname, proc_jbd2_stats);
 	if (journal->j_proc_entry) {
-		proc_create_data("history", S_IRUGO, journal->j_proc_entry,
-				 &jbd2_seq_history_fops, journal);
 		proc_create_data("info", S_IRUGO, journal->j_proc_entry,
 				 &jbd2_seq_info_fops, journal);
 	}
@@ -941,27 +792,9 @@ static void jbd2_stats_proc_init(journal_t *journal)
 static void jbd2_stats_proc_exit(journal_t *journal)
 {
 	remove_proc_entry("info", journal->j_proc_entry);
-	remove_proc_entry("history", journal->j_proc_entry);
 	remove_proc_entry(journal->j_devname, proc_jbd2_stats);
 }
 
-static void journal_init_stats(journal_t *journal)
-{
-	int size;
-
-	if (!proc_jbd2_stats)
-		return;
-
-	journal->j_history_max = 100;
-	size = sizeof(struct transaction_stats_s) * journal->j_history_max;
-	journal->j_history = kzalloc(size, GFP_KERNEL);
-	if (!journal->j_history) {
-		journal->j_history_max = 0;
-		return;
-	}
-	spin_lock_init(&journal->j_history_lock);
-}
-
 /*
  * Management for journal control blocks: functions to create and
  * destroy journal_t structures, and to initialise and read existing
@@ -1006,7 +839,7 @@ static journal_t * journal_init_common (void)
 		goto fail;
 	}
 
-	journal_init_stats(journal);
+	spin_lock_init(&journal->j_history_lock);
 
 	return journal;
 fail:

include/linux/jbd2.h

@@ -464,9 +464,9 @@ struct handle_s
  */
 struct transaction_chp_stats_s {
 	unsigned long		cs_chp_time;
-	unsigned long		cs_forced_to_close;
-	unsigned long		cs_written;
-	unsigned long		cs_dropped;
+	__u32			cs_forced_to_close;
+	__u32			cs_written;
+	__u32			cs_dropped;
 };
 
 /* The transaction_t type is the guts of the journaling mechanism.  It
@@ -668,23 +668,16 @@ struct transaction_run_stats_s {
 	unsigned long		rs_flushing;
 	unsigned long		rs_logging;
 
-	unsigned long		rs_handle_count;
-	unsigned long		rs_blocks;
-	unsigned long		rs_blocks_logged;
+	__u32			rs_handle_count;
+	__u32			rs_blocks;
+	__u32			rs_blocks_logged;
 };
 
 struct transaction_stats_s {
-	int 			ts_type;
 	unsigned long		ts_tid;
-	union {
 	struct transaction_run_stats_s run;
-		struct transaction_chp_stats_s chp;
-	} u;
 };
 
-#define JBD2_STATS_RUN		1
-#define JBD2_STATS_CHECKPOINT	2
-
 static inline unsigned long
 jbd2_time_diff(unsigned long start, unsigned long end)
 {
@@ -988,12 +981,6 @@ struct journal_s
 	/*
 	 * Journal statistics
 	 */
-	struct transaction_stats_s *j_history;
-	int			j_history_max;
-	int			j_history_cur;
-	/*
-	 * Protect the transactions statistics history
-	 */
 	spinlock_t		j_history_lock;
 	struct proc_dir_entry	*j_proc_entry;
 	struct transaction_stats_s j_stats;

include/trace/events/jbd2.h

@@ -7,6 +7,9 @@
 #include <linux/jbd2.h>
 #include <linux/tracepoint.h>
 
+struct transaction_chp_stats_s;
+struct transaction_run_stats_s;
+
 TRACE_EVENT(jbd2_checkpoint,
 
 	TP_PROTO(journal_t *journal, int result),
@@ -162,6 +165,81 @@ TRACE_EVENT(jbd2_submit_inode_data,
 		  jbd2_dev_to_name(__entry->dev), (unsigned long) __entry->ino)
 );
 
+TRACE_EVENT(jbd2_run_stats,
+	TP_PROTO(dev_t dev, unsigned long tid,
+		 struct transaction_run_stats_s *stats),
+
+	TP_ARGS(dev, tid, stats),
+
+	TP_STRUCT__entry(
+		__field(		dev_t,	dev		)
+		__field(	unsigned long,	tid		)
+		__field(	unsigned long,	wait		)
+		__field(	unsigned long,	running		)
+		__field(	unsigned long,	locked		)
+		__field(	unsigned long,	flushing	)
+		__field(	unsigned long,	logging		)
+		__field(		__u32,	handle_count	)
+		__field(		__u32,	blocks		)
+		__field(		__u32,	blocks_logged	)
+	),
+
+	TP_fast_assign(
+		__entry->dev		= dev;
+		__entry->tid		= tid;
+		__entry->wait		= stats->rs_wait;
+		__entry->running	= stats->rs_running;
+		__entry->locked		= stats->rs_locked;
+		__entry->flushing	= stats->rs_flushing;
+		__entry->logging	= stats->rs_logging;
+		__entry->handle_count	= stats->rs_handle_count;
+		__entry->blocks		= stats->rs_blocks;
+		__entry->blocks_logged	= stats->rs_blocks_logged;
+	),
+
+	TP_printk("dev %s tid %lu wait %u running %u locked %u flushing %u "
+		  "logging %u handle_count %u blocks %u blocks_logged %u",
+		  jbd2_dev_to_name(__entry->dev), __entry->tid,
+		  jiffies_to_msecs(__entry->wait),
+		  jiffies_to_msecs(__entry->running),
+		  jiffies_to_msecs(__entry->locked),
+		  jiffies_to_msecs(__entry->flushing),
+		  jiffies_to_msecs(__entry->logging),
+		  __entry->handle_count, __entry->blocks,
+		  __entry->blocks_logged)
+);
+
+TRACE_EVENT(jbd2_checkpoint_stats,
+	TP_PROTO(dev_t dev, unsigned long tid,
+		 struct transaction_chp_stats_s *stats),
+
+	TP_ARGS(dev, tid, stats),
+
+	TP_STRUCT__entry(
+		__field(		dev_t,	dev		)
+		__field(	unsigned long,	tid		)
+		__field(	unsigned long,	chp_time	)
+		__field(		__u32,	forced_to_close	)
+		__field(		__u32,	written		)
+		__field(		__u32,	dropped		)
+	),
+
+	TP_fast_assign(
+		__entry->dev		= dev;
+		__entry->tid		= tid;
+		__entry->chp_time	= stats->cs_chp_time;
+		__entry->forced_to_close= stats->cs_forced_to_close;
+		__entry->written	= stats->cs_written;
+		__entry->dropped	= stats->cs_dropped;
+	),
+
+	TP_printk("dev %s tid %lu chp_time %u forced_to_close %u "
+		  "written %u dropped %u",
+		  jbd2_dev_to_name(__entry->dev), __entry->tid,
+		  jiffies_to_msecs(__entry->chp_time),
+		  __entry->forced_to_close, __entry->written, __entry->dropped)
+);
+
 #endif /* _TRACE_JBD2_H */
 
 /* This part must be outside protection */