bcachefs: Run fsck if BCH_FEATURE_alloc_v2 isn't set

We're using BCH_FEATURE_alloc_v2 to also gate journalling updates to dev
usage - we don't have the code for reconstructing this from buckets
anymore, so we need to run fsck if it's not set.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/recovery.c

@@ -1088,6 +1088,13 @@ 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->sb.features & (1ULL << BCH_FEATURE_alloc_v2))) {
+		bch_info(c, "alloc_v2 feature bit not set, fsck required");
+		c->opts.fsck = true;
+		c->opts.fix_errors = FSCK_OPT_YES;
+		c->disk_sb.sb->features[0] |= 1ULL << BCH_FEATURE_alloc_v2;
+	}
+
 	if (!c->replicas.entries ||
 	    c->opts.rebuild_replicas) {
 		bch_info(c, "building replicas info");