bcache: wait for buckets when allocating new btree root

Tested:
- sometimes bcache_tier test would hang on startup with a failure
  to allocate the btree root -- no longer seeing this

Signed-off-by: Kent Overstreet <kmo@daterainc.com>

3 files changed, 12 insertions, 5 deletions

diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
index 7347b6100961..9dd9f1c4d0d9 100644
--- a/drivers/md/bcache/btree.c
+++ b/drivers/md/bcache/btree.c
@@ -1060,15 +1060,15 @@ static void btree_node_free(struct btree *b)
         mutex_unlock(&b->c->bucket_lock);
 }
 
-struct btree *bch_btree_node_alloc(struct cache_set *c, struct btree_op *op,
-                                   int level)
+struct btree *__bch_btree_node_alloc(struct cache_set *c, struct btree_op *op,
+                                     int level, bool wait)
 {
         BKEY_PADDED(key) k;
         struct btree *b = ERR_PTR(-EAGAIN);
 
         mutex_lock(&c->bucket_lock);
 retry:
-        if (__bch_bucket_alloc_set(c, RESERVE_BTREE, &k.key, 1, op != NULL))
+        if (__bch_bucket_alloc_set(c, RESERVE_BTREE, &k.key, 1, wait))
                 goto err;
 
         bkey_put(c, &k.key);
@@ -1100,6 +1100,12 @@ err:
         return b;
 }
 
+static struct btree *bch_btree_node_alloc(struct cache_set *c,
+                                          struct btree_op *op, int level)
+{
+        return __bch_btree_node_alloc(c, op, level, op != NULL);
+}
+
 static struct btree *btree_node_alloc_replacement(struct btree *b,
                                                   struct btree_op *op)
 {
diff --git a/drivers/md/bcache/btree.h b/drivers/md/bcache/btree.h
index 91dfa5e69685..00441821f5ad 100644
--- a/drivers/md/bcache/btree.h
+++ b/drivers/md/bcache/btree.h
@@ -242,7 +242,8 @@ void __bch_btree_node_write(struct btree *, struct closure *);
 void bch_btree_node_write(struct btree *, struct closure *);
 
 void bch_btree_set_root(struct btree *);
-struct btree *bch_btree_node_alloc(struct cache_set *, struct btree_op *, int);
+struct btree *__bch_btree_node_alloc(struct cache_set *, struct btree_op *,
+                                     int, bool);
 struct btree *bch_btree_node_get(struct cache_set *, struct btree_op *,
                                  struct bkey *, int, bool);
 
diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index 6ceaec35b871..3b043a04d9bd 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -1669,7 +1669,7 @@ static void run_cache_set(struct cache_set *c)
                         goto err;
 
                 err = "cannot allocate new btree root";
-                c->root = bch_btree_node_alloc(c, NULL, 0);
+                c->root = __bch_btree_node_alloc(c, NULL, 0, true);
                 if (IS_ERR_OR_NULL(c->root))
                         goto err;