bcachefs: Lock ordering fix

Can't take btree node locks while holding btree_reserve_cache_lock - it
would be nice if we could check this with lockdep.

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>

diff --git a/fs/bcachefs/btree_update_interior.c b/fs/bcachefs/btree_update_interior.c
index 27ab1cde22170a8827487328facc41ad91fe8543..9696eb2b91e71d2c523d67377bbfea5be44130bd 100644 (file)
--- a/fs/bcachefs/btree_update_interior.c
+++ b/fs/bcachefs/btree_update_interior.c
@@ -383,16 +383,13 @@ static void bch2_btree_reserve_put(struct btree_update *as)
        struct bch_fs *c = as->c;
        struct prealloc_nodes *p;
 
-       mutex_lock(&c->btree_reserve_cache_lock);
-
        for (p = as->prealloc_nodes;
             p < as->prealloc_nodes + ARRAY_SIZE(as->prealloc_nodes);
             p++) {
                while (p->nr) {
                        struct btree *b = p->b[--p->nr];
 
-                       six_lock_intent(&b->c.lock, NULL, NULL);
-                       six_lock_write(&b->c.lock, NULL, NULL);
+                       mutex_lock(&c->btree_reserve_cache_lock);
 
                        if (c->btree_reserve_cache_nr <
                            ARRAY_SIZE(c->btree_reserve_cache)) {
@@ -406,13 +403,15 @@ static void bch2_btree_reserve_put(struct btree_update *as)
                                bch2_open_buckets_put(c, &b->ob);
                        }
 
+                       mutex_unlock(&c->btree_reserve_cache_lock);
+
+                       six_lock_intent(&b->c.lock, NULL, NULL);
+                       six_lock_write(&b->c.lock, NULL, NULL);
                        __btree_node_free(c, b);
                        six_unlock_write(&b->c.lock);
                        six_unlock_intent(&b->c.lock);
                }
        }
-
-       mutex_unlock(&c->btree_reserve_cache_lock);
 }
 
 static int bch2_btree_reserve_get(struct btree_trans *trans,