bcachefs: Improve trans_restart_split_race tracepoint

Seeing occasional test failures where we get stuck in a livelock that
involves this event - this will help track it down.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/btree_update_interior.c

@@ -1680,7 +1680,7 @@ static int bch2_btree_insert_node(struct btree_update *as, struct btree_trans *t
 	BUG_ON(!as || as->b);
 	bch2_verify_keylist_sorted(keys);
 
-	if (!(local_clock() & 63))
+	if ((local_clock() & 63) == 63)
 		return btree_trans_restart(trans, BCH_ERR_transaction_restart_split_race);
 
 	ret = bch2_btree_node_lock_write(trans, path, &b->c);
@@ -1720,7 +1720,7 @@ static int bch2_btree_insert_node(struct btree_update *as, struct btree_trans *t
 	 * bch2_btree_path_upgrade() and allocating more nodes:
 	 */
 	if (b->c.level >= as->update_level) {
-		trace_and_count(c, trans_restart_split_race, trans, _THIS_IP_);
+		trace_and_count(c, trans_restart_split_race, trans, _THIS_IP_, b);
 		return btree_trans_restart(trans, BCH_ERR_transaction_restart_split_race);
 	}
 

fs/bcachefs/trace.c

@@ -2,8 +2,10 @@
 #include "bcachefs.h"
 #include "alloc_types.h"
 #include "buckets.h"
+#include "btree_cache.h"
 #include "btree_iter.h"
 #include "btree_locking.h"
+#include "btree_update_interior.h"
 #include "keylist.h"
 #include "opts.h"
 #include "six.h"

fs/bcachefs/trace.h

@@ -831,10 +831,35 @@ DEFINE_EVENT(transaction_event,	trans_restart_injected,
 	TP_ARGS(trans, caller_ip)
 );
 
-DEFINE_EVENT(transaction_event,	trans_restart_split_race,
+TRACE_EVENT(trans_restart_split_race,
 	TP_PROTO(struct btree_trans *trans,
-		 unsigned long caller_ip),
-	TP_ARGS(trans, caller_ip)
+		 unsigned long caller_ip,
+		 struct btree *b),
+	TP_ARGS(trans, caller_ip, b),
+
+	TP_STRUCT__entry(
+		__array(char,			trans_fn, 32	)
+		__field(unsigned long,		caller_ip	)
+		__field(u8,			level		)
+		__field(u16,			written		)
+		__field(u16,			blocks		)
+		__field(u16,			u64s_remaining	)
+	),
+
+	TP_fast_assign(
+		strscpy(__entry->trans_fn, trans->fn, sizeof(__entry->trans_fn));
+		__entry->caller_ip		= caller_ip;
+		__entry->level		= b->c.level;
+		__entry->written	= b->written;
+		__entry->blocks		= btree_blocks(trans->c);
+		__entry->u64s_remaining	= bch_btree_keys_u64s_remaining(trans->c, b);
+	),
+
+	TP_printk("%s %pS l=%u written %u/%u u64s remaining %u",
+		  __entry->trans_fn, (void *) __entry->caller_ip,
+		  __entry->level,
+		  __entry->written, __entry->blocks,
+		  __entry->u64s_remaining)
 );
 
 DEFINE_EVENT(transaction_event,	trans_blocked_journal_reclaim,