bcachefs: BCH_JSET_ENTRY_log

Add a journal entry type for logging messages, and add an option to use
it to log the transaction name - this makes for a very handy debugging
tool, as with it we can use the 'bcachefs list_journal' command to see
not only what updates were done, but what was doing them.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>

fs/bcachefs/bcachefs_format.h

@@ -1430,6 +1430,7 @@ LE64_BITMASK(BCH_SB_INODES_USE_KEY_CACHE,struct bch_sb, flags[3], 29, 30);
 LE64_BITMASK(BCH_SB_JOURNAL_FLUSH_DELAY,struct bch_sb, flags[3], 30, 62);
 LE64_BITMASK(BCH_SB_JOURNAL_FLUSH_DISABLED,struct bch_sb, flags[3], 62, 63);
 LE64_BITMASK(BCH_SB_JOURNAL_RECLAIM_DELAY,struct bch_sb, flags[4], 0, 32);
+LE64_BITMASK(BCH_SB_JOURNAL_TRANSACTION_NAMES,struct bch_sb, flags[4], 32, 33);
 
 /*
  * Features:
@@ -1667,7 +1668,8 @@ static inline __u64 __bset_magic(struct bch_sb *sb)
 	x(usage,		5)		\
 	x(data_usage,		6)		\
 	x(clock,		7)		\
-	x(dev_usage,		8)
+	x(dev_usage,		8)		\
+	x(log,			9)
 
 enum {
 #define x(f, nr)	BCH_JSET_ENTRY_##f	= nr,
@@ -1739,6 +1741,11 @@ struct jset_entry_dev_usage {
 	struct jset_entry_dev_usage_type d[];
 } __attribute__((packed));
 
+struct jset_entry_log {
+	struct jset_entry	entry;
+	u8			d[];
+} __attribute__((packed));
+
 /*
  * On disk format for a journal entry:
  * seq is monotonically increasing; every journal entry has its own unique

fs/bcachefs/btree_types.h

@@ -380,6 +380,7 @@ struct btree_trans {
 	bool			in_traverse_all:1;
 	bool			restarted:1;
 	bool			paths_sorted:1;
+	bool			journal_transaction_names:1;
 	/*
 	 * For when bch2_trans_update notices we'll be splitting a compressed
 	 * extent:

fs/bcachefs/btree_update_leaf.c

@@ -290,6 +290,31 @@ static inline int bch2_trans_journal_res_get(struct btree_trans *trans,
 	return ret == -EAGAIN ? BTREE_INSERT_NEED_JOURNAL_RES : ret;
 }
 
+#define JSET_ENTRY_LOG_U64s		4
+
+static noinline void journal_transaction_name(struct btree_trans *trans)
+{
+	struct bch_fs *c = trans->c;
+	struct jset_entry *entry = journal_res_entry(&c->journal, &trans->journal_res);
+	struct jset_entry_log *l = container_of(entry, struct jset_entry_log, entry);
+	unsigned u64s = JSET_ENTRY_LOG_U64s - 1;
+	unsigned b, buflen = u64s * sizeof(u64);
+
+	l->entry.u64s		= cpu_to_le16(u64s);
+	l->entry.btree_id	= 0;
+	l->entry.level		= 0;
+	l->entry.type		= BCH_JSET_ENTRY_log;
+	l->entry.pad[0]		= 0;
+	l->entry.pad[1]		= 0;
+	l->entry.pad[2]		= 0;
+	b = snprintf(l->d, buflen, "%ps", (void *) trans->ip);
+	while (b < buflen)
+		l->d[b++] = '\0';
+
+	trans->journal_res.offset	+= JSET_ENTRY_LOG_U64s;
+	trans->journal_res.u64s		-= JSET_ENTRY_LOG_U64s;
+}
+
 static inline enum btree_insert_ret
 btree_key_can_insert(struct btree_trans *trans,
 		     struct btree *b,
@@ -451,6 +476,9 @@ bch2_trans_commit_write_locked(struct btree_trans *trans,
 				JOURNAL_RES_GET_NONBLOCK);
 		if (ret)
 			return ret;
+
+		if (unlikely(trans->journal_transaction_names))
+			journal_transaction_name(trans);
 	} else {
 		trans->journal_res.seq = c->journal.replay_journal_seq;
 	}
@@ -911,6 +939,7 @@ static int bch2_trans_commit_run_triggers(struct btree_trans *trans)
 
 int __bch2_trans_commit(struct btree_trans *trans)
 {
+	struct bch_fs *c = trans->c;
 	struct btree_insert_entry *i = NULL;
 	unsigned u64s;
 	int ret = 0;
@@ -920,15 +949,20 @@ int __bch2_trans_commit(struct btree_trans *trans)
 		goto out_reset;
 
 	if (trans->flags & BTREE_INSERT_GC_LOCK_HELD)
-		lockdep_assert_held(&trans->c->gc_lock);
+		lockdep_assert_held(&c->gc_lock);
 
 	memset(&trans->journal_preres, 0, sizeof(trans->journal_preres));
 
 	trans->journal_u64s		= trans->extra_journal_entry_u64s;
 	trans->journal_preres_u64s	= 0;
 
+	trans->journal_transaction_names = READ_ONCE(c->opts.journal_transaction_names);
+
+	if (trans->journal_transaction_names)
+		trans->journal_u64s += JSET_ENTRY_LOG_U64s;
+
 	if (!(trans->flags & BTREE_INSERT_NOCHECK_RW) &&
-	    unlikely(!percpu_ref_tryget(&trans->c->writes))) {
+	    unlikely(!percpu_ref_tryget(&c->writes))) {
 		ret = bch2_trans_commit_get_rw_cold(trans);
 		if (ret)
 			goto out_reset;
@@ -972,7 +1006,7 @@ int __bch2_trans_commit(struct btree_trans *trans)
 	}
 
 	if (trans->extra_journal_res) {
-		ret = bch2_disk_reservation_add(trans->c, trans->disk_res,
+		ret = bch2_disk_reservation_add(c, trans->disk_res,
 				trans->extra_journal_res,
 				(trans->flags & BTREE_INSERT_NOFAIL)
 				? BCH_DISK_RESERVATION_NOFAIL : 0);
@@ -991,10 +1025,10 @@ int __bch2_trans_commit(struct btree_trans *trans)
 	if (ret)
 		goto err;
 out:
-	bch2_journal_preres_put(&trans->c->journal, &trans->journal_preres);
+	bch2_journal_preres_put(&c->journal, &trans->journal_preres);
 
 	if (likely(!(trans->flags & BTREE_INSERT_NOCHECK_RW)))
-		percpu_ref_put(&trans->c->writes);
+		percpu_ref_put(&c->writes);
 out_reset:
 	trans_for_each_update(trans, i)
 		bch2_path_put(trans, i->path, true);

fs/bcachefs/journal_io.c

@@ -478,6 +478,14 @@ static int journal_entry_validate_dev_usage(struct bch_fs *c,
 	return ret;
 }
 
+static int journal_entry_validate_log(struct bch_fs *c,
+				      const char *where,
+				      struct jset_entry *entry,
+				      unsigned version, int big_endian, int write)
+{
+	return 0;
+}
+
 struct jset_entry_ops {
 	int (*validate)(struct bch_fs *, const char *,
 			struct jset_entry *, unsigned, int, int);

fs/bcachefs/opts.h

@@ -327,6 +327,11 @@ enum opt_type {
 	  OPT_BOOL(),							\
 	  NO_SB_OPT,			false,				\
 	  NULL,		"Read all journal entries, not just dirty ones")\
+	x(journal_transaction_names,	u8,				\
+	  OPT_FS|OPT_FORMAT|OPT_MOUNT|OPT_RUNTIME,			\
+	  OPT_BOOL(),							\
+	  BCH_SB_JOURNAL_TRANSACTION_NAMES, true,			\
+	  NULL,		"Log transaction function names in journal")	\
 	x(noexcl,			u8,				\
 	  OPT_FS|OPT_MOUNT,						\
 	  OPT_BOOL(),							\