From dd091e18a98538200bc6a9ae8c66f08fd8a6d1df Mon Sep 17 00:00:00 2001
From: Zach Brown <zab@versity.com>
Date: Wed, 18 Apr 2018 09:26:30 -0700
Subject: [PATCH] scoutfs: add trans item tracking trace

Add a trace event that records the changes to a reservation's dirty item
count.

Signed-off-by: Zach Brown <zab@versity.com>
---
 kmod/src/scoutfs_trace.h | 33 +++++++++++++++++++++++++++++++++
 kmod/src/trans.c         | 14 ++++++++++++++
 2 files changed, 47 insertions(+)

diff --git a/kmod/src/scoutfs_trace.h b/kmod/src/scoutfs_trace.h
index 5e480364..5c3178ff 100644
--- a/kmod/src/scoutfs_trace.h
+++ b/kmod/src/scoutfs_trace.h
@@ -660,6 +660,39 @@ TRACE_EVENT(scoutfs_trans_acquired_hold,
 		  __entry->tri_items, __entry->tri_vals)
 );
 
+TRACE_EVENT(scoutfs_trans_track_item,
+	TP_PROTO(struct super_block *sb, int delta_items, int delta_vals,
+		 int act_items, int act_vals, int res_items, int res_vals),
+
+	TP_ARGS(sb, delta_items, delta_vals, act_items, act_vals, res_items,
+		res_vals),
+
+	TP_STRUCT__entry(
+		__field(__u64, fsid)
+		__field(int, delta_items)
+		__field(int, delta_vals)
+		__field(int, act_items)
+		__field(int, act_vals)
+		__field(int, res_items)
+		__field(int, res_vals)
+	),
+
+	TP_fast_assign(
+		__entry->fsid = FSID_ARG(sb);
+		__entry->delta_items = delta_items;
+		__entry->delta_vals = delta_vals;
+		__entry->act_items = act_items;
+		__entry->act_vals = act_vals;
+		__entry->res_items = res_items;
+		__entry->res_vals = res_vals;
+	),
+
+	TP_printk("fsid "FSID_FMT" delta_items %d delta_vals %d act_items %d act_vals %d res_items %d res_vals %d",
+		  __entry->fsid, __entry->delta_items, __entry->delta_vals,
+		  __entry->act_items, __entry->act_vals, __entry->res_items,
+		  __entry->res_vals)
+);
+
 TRACE_EVENT(scoutfs_ioc_release_ret,
 	TP_PROTO(struct super_block *sb, int ret),
 
diff --git a/kmod/src/trans.c b/kmod/src/trans.c
index 2c39951f..9e45b7e2 100644
--- a/kmod/src/trans.c
+++ b/kmod/src/trans.c
@@ -392,6 +392,16 @@ bool scoutfs_trans_held(void)
 	return rsv && rsv->magic == SCOUTFS_RESERVATION_MAGIC;
 }
 
+/*
+ * Record a transaction holder's individual contribution to the dirty
+ * items in the current transaction.  We're making sure that the
+ * reservation matches the possible item manipulations while they hold
+ * the reservation.
+ *
+ * It is possible and legitimate for an individual contribution to be
+ * negative if they delete dirty items.  The item cache makes sure that
+ * the total dirty item count doesn't fall below zero.
+ */
 void scoutfs_trans_track_item(struct super_block *sb, signed items,
 			      signed vals)
 {
@@ -406,6 +416,10 @@ void scoutfs_trans_track_item(struct super_block *sb, signed items,
 	rsv->actual.items += items;
 	rsv->actual.vals += vals;
 
+	trace_scoutfs_trans_track_item(sb, items, vals, rsv->actual.items,
+				       rsv->actual.vals, rsv->reserved.items,
+				       rsv->reserved.vals);
+
 	WARN_ON_ONCE(rsv->actual.items > rsv->reserved.items);
 	WARN_ON_ONCE(rsv->actual.vals > rsv->reserved.vals);
 }