bcachefs: added lock held time stats

We now record the length of time btree locks are held and expose this in debugfs.

Enabled via CONFIG_BCACHEFS_LOCK_TIME_STATS.

Signed-off-by: Daniel Hill <daniel@gluo.nz>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

1 files changed, 74 insertions, 0 deletions

diff --git a/fs/bcachefs/debug.c b/fs/bcachefs/debug.c
index 0f25b75e3de7..45f5229f20eb 100644
--- a/fs/bcachefs/debug.c
+++ b/fs/bcachefs/debug.c
@@ -638,6 +638,75 @@ static const struct file_operations journal_pins_ops = {
 	.read		= bch2_journal_pins_read,
 };
 
+static int lock_held_stats_open(struct inode *inode, struct file *file)
+{
+	struct bch_fs *c = inode->i_private;
+	struct dump_iter *i;
+
+	i = kzalloc(sizeof(struct dump_iter), GFP_KERNEL);
+
+	if (!i)
+		return -ENOMEM;
+
+	i->iter = 0;
+	i->c    = c;
+	i->buf  = PRINTBUF;
+	file->private_data = i;
+
+	return 0;
+}
+
+static int lock_held_stats_release(struct inode *inode, struct file *file)
+{
+	struct dump_iter *i = file->private_data;
+
+	printbuf_exit(&i->buf);
+	kfree(i);
+
+	return 0;
+}
+
+static ssize_t lock_held_stats_read(struct file *file, char __user *buf,
+				      size_t size, loff_t *ppos)
+{
+	struct dump_iter        *i = file->private_data;
+	struct lock_held_stats *lhs = &i->c->lock_held_stats;
+	int err;
+
+	i->ubuf = buf;
+	i->size = size;
+	i->ret  = 0;
+
+	while (lhs->names[i->iter] != 0 && i->iter < BCH_LOCK_TIME_NR) {
+		err = flush_buf(i);
+		if (err)
+			return err;
+
+		if (!i->size)
+			break;
+
+		prt_printf(&i->buf, "%s:", lhs->names[i->iter]);
+		prt_newline(&i->buf);
+		printbuf_indent_add(&i->buf, 8);
+		bch2_time_stats_to_text(&i->buf, &lhs->times[i->iter]);
+		printbuf_indent_sub(&i->buf, 8);
+		prt_newline(&i->buf);
+		i->iter++;
+	}
+
+	if (i->buf.allocation_failure)
+		return -ENOMEM;
+
+	return i->ret;
+}
+
+static const struct file_operations lock_held_stats_op = {
+	.owner = THIS_MODULE,
+	.open = lock_held_stats_open,
+	.release = lock_held_stats_release,
+	.read = lock_held_stats_read,
+};
+
 void bch2_fs_debug_exit(struct bch_fs *c)
 {
 	if (!IS_ERR_OR_NULL(c->fs_debug_dir))
@@ -668,6 +737,11 @@ void bch2_fs_debug_init(struct bch_fs *c)
 	debugfs_create_file("journal_pins", 0400, c->fs_debug_dir,
 			    c->btree_debug, &journal_pins_ops);
 
+	if (IS_ENABLED(CONFIG_BCACHEFS_LOCK_TIME_STATS)) {
+		debugfs_create_file("lock_held_stats", 0400, c->fs_debug_dir,
+				c, &lock_held_stats_op);
+	}
+
 	c->btree_debug_dir = debugfs_create_dir("btrees", c->fs_debug_dir);
 	if (IS_ERR_OR_NULL(c->btree_debug_dir))
 		return;