bcachefs: Improve trans_blocked_journal_reclaim tracepoint

include information about the state of the btree key cache
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/btree_key_cache.h

@@ -11,13 +11,18 @@ static inline size_t bch2_nr_btree_keys_need_flush(struct bch_fs *c)
 	return max_t(ssize_t, 0, nr_dirty - max_dirty);
 }
 
-static inline bool bch2_btree_key_cache_must_wait(struct bch_fs *c)
+static inline ssize_t __bch2_btree_key_cache_must_wait(struct bch_fs *c)
 {
 	size_t nr_dirty = atomic_long_read(&c->btree_key_cache.nr_dirty);
 	size_t nr_keys = atomic_long_read(&c->btree_key_cache.nr_keys);
 	size_t max_dirty = 4096 + (nr_keys * 3) / 4;
 
-	return nr_dirty > max_dirty;
+	return nr_dirty - max_dirty;
+}
+
+static inline bool bch2_btree_key_cache_must_wait(struct bch_fs *c)
+{
+	return __bch2_btree_key_cache_must_wait(c) > 0;
 }
 
 static inline bool bch2_btree_key_cache_wait_done(struct bch_fs *c)

fs/bcachefs/trace.c

@@ -4,6 +4,7 @@
 #include "buckets.h"
 #include "btree_cache.h"
 #include "btree_iter.h"
+#include "btree_key_cache.h"
 #include "btree_locking.h"
 #include "btree_update_interior.h"
 #include "keylist.h"

fs/bcachefs/trace.h

@@ -988,10 +988,33 @@ TRACE_EVENT(trans_restart_split_race,
 		  __entry->u64s_remaining)
 );
 
-DEFINE_EVENT(transaction_event,	trans_blocked_journal_reclaim,
+TRACE_EVENT(trans_blocked_journal_reclaim,
 	TP_PROTO(struct btree_trans *trans,
 		 unsigned long caller_ip),
-	TP_ARGS(trans, caller_ip)
+	TP_ARGS(trans, caller_ip),
+
+	TP_STRUCT__entry(
+		__array(char,			trans_fn, 32	)
+		__field(unsigned long,		caller_ip	)
+
+		__field(unsigned long,		key_cache_nr_keys	)
+		__field(unsigned long,		key_cache_nr_dirty	)
+		__field(long,			must_wait		)
+	),
+
+	TP_fast_assign(
+		strscpy(__entry->trans_fn, trans->fn, sizeof(__entry->trans_fn));
+		__entry->caller_ip		= caller_ip;
+		__entry->key_cache_nr_keys	= atomic_long_read(&trans->c->btree_key_cache.nr_keys);
+		__entry->key_cache_nr_dirty	= atomic_long_read(&trans->c->btree_key_cache.nr_dirty);
+		__entry->must_wait		= __bch2_btree_key_cache_must_wait(trans->c);
+	),
+
+	TP_printk("%s %pS key cache keys %lu dirty %lu must_wait %li",
+		  __entry->trans_fn, (void *) __entry->caller_ip,
+		  __entry->key_cache_nr_keys,
+		  __entry->key_cache_nr_dirty,
+		  __entry->must_wait)
 );
 
 TRACE_EVENT(trans_restart_journal_preres_get,