alinux: jbd2: add new "stats" proc file

/proc/fs/jbd2/${device}/info only shows whole average statistical
info about jbd2's life cycle, but it can not show jbd2 info in
specified time interval and sometimes this capability is very useful
for trouble shooting. For example, we can not see how rs_locked and
rs_flushing grows in specified time interval, but these two indexes
can explain some reasons for app's behaviours.

Here we add a new "stats" proc file like /proc/diskstats, then we can
implement a simple tool jbd2_stats which'll display detailed jbd2 info
in specified time interval. Like below(time interval 5s):

[lege@localhost ~]$ cat /proc/fs/jbd2/vdb1-8/stats
51 30 8192 0 1 241616 0 0 22 0 47158 891 942 1000 1000

[lege@localhost ~]$ gcc -o jbd2_stat jbd2_stat.c ; ./jbd2_stat

Device              tid     trans   handles    locked  flushing
logging
vdb1-8             1861       158       359     13.00      0.00
2.00

Device              tid     trans   handles    locked  flushing
logging
vdb1-8             1974       113       389     26.00      0.00
5.00

Device              tid     trans   handles    locked  flushing
logging
vdb1-8             2188       214       308     10.00      0.00
7.00

Device              tid     trans   handles    locked  flushing
logging
vdb1-8             2344       156       332     19.00      0.00
4.00
Reviewed-by: NJoseph Qi <joseph.qi@linux.alibaba.com>
Reviewed-by: NLiu Bo <bo.liu@linux.alibaba.com>
Signed-off-by: NXiaoguang Wang <xiaoguang.wang@linux.alibaba.com>
Signed-off-by: NJoseph Qi <joseph.qi@linux.alibaba.com>
Acked-by: NCaspar Zhang <caspar@linux.alibaba.com>

fs/jbd2/journal.c

@@ -1105,25 +1105,77 @@ static const struct seq_operations jbd2_seq_info_ops = {
 	.show   = jbd2_seq_info_show,
 };
 
-static int jbd2_seq_info_open(struct inode *inode, struct file *file)
+static void *jbd2_seq_stats_start(struct seq_file *seq, loff_t *pos)
+{
+	return *pos ? NULL : SEQ_START_TOKEN;
+}
+
+static void *jbd2_seq_stats_next(struct seq_file *seq, void *v, loff_t *pos)
+{
+	return NULL;
+}
+
+static int jbd2_seq_stats_show(struct seq_file *seq, void *v)
+{
+	struct jbd2_stats_proc_session *s = seq->private;
+
+	if (v != SEQ_START_TOKEN)
+		return 0;
+
+	seq_printf(seq, "%lu %lu %d %lu %lu %lu %lu %lu %lu %llu %u %u %u %d %d\n",
+		s->stats->ts_tid, s->stats->ts_requested,
+		s->journal->j_max_transaction_buffers, s->stats->run.rs_wait,
+		s->stats->run.rs_request_delay, s->stats->run.rs_running,
+		s->stats->run.rs_locked, s->stats->run.rs_flushing,
+		s->stats->run.rs_logging,
+		s->journal->j_average_commit_time / NSEC_PER_MSEC,
+		s->stats->run.rs_handle_count, s->stats->run.rs_blocks,
+		s->stats->run.rs_blocks_logged, HZ, jiffies_to_msecs(HZ));
+	return 0;
+}
+
+static void jbd2_seq_stats_stop(struct seq_file *seq, void *v)
+{
+}
+
+static const struct seq_operations jbd2_seq_stats_ops = {
+	.start  = jbd2_seq_stats_start,
+	.next   = jbd2_seq_stats_next,
+	.stop   = jbd2_seq_stats_stop,
+	.show   = jbd2_seq_stats_show,
+};
+
+static struct jbd2_stats_proc_session *__jbd2_seq_open(struct inode *inode,
+			struct file *file)
 {
 	journal_t *journal = PDE_DATA(inode);
 	struct jbd2_stats_proc_session *s;
-	int rc, size;
+	int size;
 
 	s = kmalloc(sizeof(*s), GFP_KERNEL);
 	if (s == NULL)
-		return -ENOMEM;
+		return ERR_PTR(-ENOMEM);
 	size = sizeof(struct transaction_stats_s);
 	s->stats = kmalloc(size, GFP_KERNEL);
 	if (s->stats == NULL) {
 		kfree(s);
-		return -ENOMEM;
+		return ERR_PTR(-ENOMEM);
 	}
 	spin_lock(&journal->j_history_lock);
 	memcpy(s->stats, &journal->j_stats, size);
 	s->journal = journal;
 	spin_unlock(&journal->j_history_lock);
+	return s;
+}
+
+static int jbd2_seq_info_open(struct inode *inode, struct file *file)
+{
+	struct jbd2_stats_proc_session *s;
+	int rc;
+
+	s = __jbd2_seq_open(inode, file);
+	if (IS_ERR(s))
+		return PTR_ERR(s);
 
 	rc = seq_open(file, &jbd2_seq_info_ops);
 	if (rc == 0) {
@@ -1134,7 +1186,6 @@ static int jbd2_seq_info_open(struct inode *inode, struct file *file)
 		kfree(s);
 	}
 	return rc;
-
 }
 
 static int jbd2_seq_info_release(struct inode *inode, struct file *file)
@@ -1154,6 +1205,45 @@ static const struct file_operations jbd2_seq_info_fops = {
 	.release        = jbd2_seq_info_release,
 };
 
+static int jbd2_seq_stats_open(struct inode *inode, struct file *file)
+{
+	struct jbd2_stats_proc_session *s;
+	int rc;
+
+	s = __jbd2_seq_open(inode, file);
+	if (IS_ERR(s))
+		return PTR_ERR(s);
+
+	rc = seq_open(file, &jbd2_seq_stats_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_stats_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 const struct file_operations jbd2_seq_stats_fops = {
+	.owner		= THIS_MODULE,
+	.open		= jbd2_seq_stats_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= jbd2_seq_stats_release,
+};
+
 static struct proc_dir_entry *proc_jbd2_stats;
 
 static void jbd2_stats_proc_init(journal_t *journal)
@@ -1162,12 +1252,15 @@ static void jbd2_stats_proc_init(journal_t *journal)
 	if (journal->j_proc_entry) {
 		proc_create_data("info", S_IRUGO, journal->j_proc_entry,
 				 &jbd2_seq_info_fops, journal);
+		proc_create_data("stats", S_IRUGO, journal->j_proc_entry,
+				 &jbd2_seq_stats_fops, journal);
 	}
 }
 
 static void jbd2_stats_proc_exit(journal_t *journal)
 {
 	remove_proc_entry("info", journal->j_proc_entry);
+	remove_proc_entry("stats", journal->j_proc_entry);
 	remove_proc_entry(journal->j_devname, proc_jbd2_stats);
 }