bcachefs: opts.read_journal_only

Add an option that tells recovery to only read the journal, to be used
by the list_journal command.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>

fs/bcachefs/opts.h

@@ -329,6 +329,11 @@ enum opt_type {
 	  OPT_BOOL(),							\
 	  NO_SB_OPT,			false,				\
 	  NULL,		"Read all journal entries, not just dirty ones")\
+	x(read_journal_only,		u8,				\
+	  0,								\
+	  OPT_BOOL(),							\
+	  NO_SB_OPT,			false,				\
+	  NULL,		"Only read the journal, skip the rest of recovery")\
 	x(journal_transaction_names,	u8,				\
 	  OPT_FS|OPT_FORMAT|OPT_MOUNT|OPT_RUNTIME,			\
 	  OPT_BOOL(),							\

fs/bcachefs/recovery.c

@@ -1072,6 +1072,9 @@ int bch2_fs_recovery(struct bch_fs *c)
 		blacklist_seq = journal_seq = le64_to_cpu(clean->journal_seq) + 1;
 	}
 
+	if (c->opts.read_journal_only)
+		goto out;
+
 	if (c->opts.reconstruct_alloc) {
 		c->sb.compat &= ~(1ULL << BCH_COMPAT_alloc_info);
 		drop_alloc_keys(&c->journal_keys);