bcachefs: Add an option for rebuilding the replicas section

There is a bug where we cnan end up clearing the data_has field in the
superblock members section, which causes us to skip reading the journal
and thus journal replay fails. This option tells the recovery path to
not trust those fields.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/opts.h

@@ -260,6 +260,11 @@ enum opt_type {
 	  OPT_BOOL(),							\
 	  NO_SB_OPT,			false,				\
 	  NULL,		"Don't replay the journal")			\
+	x(rebuild_replicas,		u8,				\
+	  OPT_MOUNT,							\
+	  OPT_BOOL(),							\
+	  NO_SB_OPT,			false,				\
+	  NULL,		"Rebuild the superblock replicas section")	\
 	x(keep_journal,			u8,				\
 	  OPT_MOUNT,							\
 	  OPT_BOOL(),							\

fs/bcachefs/recovery.c

@@ -974,7 +974,8 @@ int bch2_fs_recovery(struct bch_fs *c)
 		bch_info(c, "recovering from clean shutdown, journal seq %llu",
 			 le64_to_cpu(clean->journal_seq));
 
-	if (!c->replicas.entries) {
+	if (!c->replicas.entries ||
+	    c->opts.rebuild_replicas) {
 		bch_info(c, "building replicas info");
 		set_bit(BCH_FS_REBUILD_REPLICAS, &c->flags);
 	}