[PATCH 15/17] bcachefs: Improve btree write buffer tracepoints

[Kent Overstreet <kent.overstreet@linux.dev>]

 - add a tracepoint for write_buffer_flush_sync; this is expensive
 - fix the write_buffer_flush_slowpath tracepoint

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
---
 fs/bcachefs/btree_write_buffer.c |  4 +++-
 fs/bcachefs/trace.h              | 31 ++++++++++++++++++++++++-------
 2 files changed, 27 insertions(+), 8 deletions(-)

diff --git a/fs/bcachefs/btree_write_buffer.c b/fs/bcachefs/btree_write_buffer.c
index be8308789477..74d864715b39 100644
--- a/fs/bcachefs/btree_write_buffer.c
+++ b/fs/bcachefs/btree_write_buffer.c
@@ -236,7 +236,7 @@ int bch2_btree_write_buffer_flush_locked(struct btree_trans *trans)
 	bch2_journal_pin_drop(j, &pin);
 	return ret;
 slowpath:
-	trace_write_buffer_flush_slowpath(trans, i - keys, nr);
+	trace_write_buffer_flush_slowpath(trans, slowpath, nr);
 
 	/*
 	 * Now sort the rest by journal seq and bump the journal pin as we go.
@@ -275,6 +275,8 @@ int bch2_btree_write_buffer_flush_sync(struct btree_trans *trans)
 	if (!bch2_write_ref_tryget(c, BCH_WRITE_REF_btree_write_buffer))
 		return -BCH_ERR_erofs_no_writes;
 
+	trace_write_buffer_flush_sync(trans, _RET_IP_);
+
 	bch2_trans_unlock(trans);
 	mutex_lock(&c->btree_write_buffer.flush_lock);
 	int ret = bch2_btree_write_buffer_flush_locked(trans);
diff --git a/fs/bcachefs/trace.h b/fs/bcachefs/trace.h
index 7857671159b4..8fadf06c7dbf 100644
--- a/fs/bcachefs/trace.h
+++ b/fs/bcachefs/trace.h
@@ -1298,21 +1298,38 @@ TRACE_EVENT(write_buffer_flush,
 		  __entry->nr, __entry->size, __entry->skipped, __entry->fast)
 );
 
+TRACE_EVENT(write_buffer_flush_sync,
+	TP_PROTO(struct btree_trans *trans, unsigned long caller_ip),
+	TP_ARGS(trans, caller_ip),
+
+	TP_STRUCT__entry(
+		__array(char,			trans_fn, 32	)
+		__field(unsigned long,		caller_ip	)
+	),
+
+	TP_fast_assign(
+		strscpy(__entry->trans_fn, trans->fn, sizeof(__entry->trans_fn));
+		__entry->caller_ip		= caller_ip;
+	),
+
+	TP_printk("%s %pS", __entry->trans_fn, (void *) __entry->caller_ip)
+);
+
 TRACE_EVENT(write_buffer_flush_slowpath,
-	TP_PROTO(struct btree_trans *trans, size_t nr, size_t size),
-	TP_ARGS(trans, nr, size),
+	TP_PROTO(struct btree_trans *trans, size_t slowpath, size_t total),
+	TP_ARGS(trans, slowpath, total),
 
 	TP_STRUCT__entry(
-		__field(size_t,		nr		)
-		__field(size_t,		size		)
+		__field(size_t,		slowpath	)
+		__field(size_t,		total		)
 	),
 
 	TP_fast_assign(
-		__entry->nr	= nr;
-		__entry->size	= size;
+		__entry->slowpath	= slowpath;
+		__entry->total		= total;
 	),
 
-	TP_printk("%zu/%zu", __entry->nr, __entry->size)
+	TP_printk("%zu/%zu", __entry->slowpath, __entry->total)
 );
 
 #endif /* _TRACE_BCACHEFS_H */
-- 
2.42.0