bcachefs: Fix an out-of-bounds shift

roundup_pow_of_two() is undefined for 0 - oops.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

diff --git a/fs/bcachefs/btree_iter.c b/fs/bcachefs/btree_iter.c
index 15bf079e17aba4afa8ee8d0c0e495e2c9d429662..611f7b0ca0146418d0f3bb9aae389642294b0316 100644 (file)
--- a/fs/bcachefs/btree_iter.c
+++ b/fs/bcachefs/btree_iter.c
@@ -2879,7 +2879,7 @@ void __bch2_trans_init(struct btree_trans *trans, struct bch_fs *c, unsigned fn_
        bch2_trans_alloc_paths(trans, c);
 
        s = btree_trans_stats(trans);
-       if (s) {
+       if (s && s->max_mem) {
                unsigned expected_mem_bytes = roundup_pow_of_two(s->max_mem);
 
                trans->mem = kmalloc(expected_mem_bytes, GFP_KERNEL);
@@ -2890,9 +2890,9 @@ void __bch2_trans_init(struct btree_trans *trans, struct bch_fs *c, unsigned fn_
                } else {
                        trans->mem_bytes = expected_mem_bytes;
                }
-
-               trans->nr_max_paths = s->nr_max_paths;
        }
+       if (s)
+               trans->nr_max_paths = s->nr_max_paths;
 
        trans->srcu_idx = srcu_read_lock(&c->btree_trans_barrier);