bcachefs: Clamp replicas_required to replicas

This prevents going emergency read only when the user has specified
replicas_required > replicas.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/bcachefs.h

@@ -1249,6 +1249,18 @@ static inline struct stdio_redirect *bch2_fs_stdio_redirect(struct bch_fs *c)
 	return stdio;
 }
 
+static inline unsigned metadata_replicas_required(struct bch_fs *c)
+{
+	return min(c->opts.metadata_replicas,
+		   c->opts.metadata_replicas_required);
+}
+
+static inline unsigned data_replicas_required(struct bch_fs *c)
+{
+	return min(c->opts.data_replicas,
+		   c->opts.data_replicas_required);
+}
+
 #define BKEY_PADDED_ONSTACK(key, pad)				\
 	struct { struct bkey_i key; __u64 key ## _pad[pad]; }
 

fs/bcachefs/btree_update_interior.c

@@ -280,7 +280,8 @@ static struct btree *__bch2_btree_node_alloc(struct btree_trans *trans,
 				      writepoint_ptr(&c->btree_write_point),
 				      &devs_have,
 				      res->nr_replicas,
-				      c->opts.metadata_replicas_required,
+				      min(res->nr_replicas,
+					  c->opts.metadata_replicas_required),
 				      watermark, 0, cl, &wp);
 	if (unlikely(ret))
 		return ERR_PTR(ret);

fs/bcachefs/io_write.c

@@ -1564,6 +1564,7 @@ CLOSURE_CALLBACK(bch2_write)
 	BUG_ON(!op->write_point.v);
 	BUG_ON(bkey_eq(op->pos, POS_MAX));
 
+	op->nr_replicas_required = min_t(unsigned, op->nr_replicas_required, op->nr_replicas);
 	op->start_time = local_clock();
 	bch2_keylist_init(&op->insert_keys, op->inline_keys);
 	wbio_init(bio)->put_bio = false;

fs/bcachefs/journal_io.c

@@ -1478,6 +1478,8 @@ static int journal_write_alloc(struct journal *j, struct journal_buf *w)
 		c->opts.foreground_target;
 	unsigned i, replicas = 0, replicas_want =
 		READ_ONCE(c->opts.metadata_replicas);
+	unsigned replicas_need = min_t(unsigned, replicas_want,
+				       READ_ONCE(c->opts.metadata_replicas_required));
 
 	rcu_read_lock();
 retry:
@@ -1526,7 +1528,7 @@ static int journal_write_alloc(struct journal *j, struct journal_buf *w)
 
 	BUG_ON(bkey_val_u64s(&w->key.k) > BCH_REPLICAS_MAX);
 
-	return replicas >= c->opts.metadata_replicas_required ? 0 : -EROFS;
+	return replicas >= replicas_need ? 0 : -EROFS;
 }
 
 static void journal_buf_realloc(struct journal *j, struct journal_buf *buf)

fs/bcachefs/journal_reclaim.c

@@ -205,7 +205,7 @@ void bch2_journal_space_available(struct journal *j)
 
 	j->can_discard = can_discard;
 
-	if (nr_online < c->opts.metadata_replicas_required) {
+	if (nr_online < metadata_replicas_required(c)) {
 		ret = JOURNAL_ERR_insufficient_devices;
 		goto out;
 	}

fs/bcachefs/super.c

@@ -1428,10 +1428,10 @@ bool bch2_dev_state_allowed(struct bch_fs *c, struct bch_dev *ca,
 
 		required = max(!(flags & BCH_FORCE_IF_METADATA_DEGRADED)
 			       ? c->opts.metadata_replicas
-			       : c->opts.metadata_replicas_required,
+			       : metadata_replicas_required(c),
 			       !(flags & BCH_FORCE_IF_DATA_DEGRADED)
 			       ? c->opts.data_replicas
-			       : c->opts.data_replicas_required);
+			       : data_replicas_required(c));
 
 		return nr_rw >= required;
 	case BCH_MEMBER_STATE_failed: