[bug report] bcachefs: bch_err_throw()

[Dan Carpenter <dan.carpenter@linaro.org>]

Hello Kent Overstreet,

Commit 09b9c72bd4b7 ("bcachefs: bch_err_throw()") from May 28, 2025
(linux-next), leads to the following (unpublished) Smatch static checker
warning:

	fs/bcachefs/super.c:2546 bch2_fs_open()
	warn: pointer dereferenced without being set 'c'

fs/bcachefs/super.c
    2515 struct bch_fs *bch2_fs_open(darray_const_str *devices,
    2516                             struct bch_opts *opts)
    2517 {
    2518         bch_sb_handles sbs = {};
    2519         struct bch_fs *c = NULL;
                               ^^^^^^^^^
c is NULL

    2520         struct bch_sb_handle *best = NULL;
    2521         int ret = 0;
    2522 
    2523         if (!try_module_get(THIS_MODULE))
    2524                 return ERR_PTR(-ENODEV);
    2525 
    2526         if (!devices->nr) {
    2527                 ret = -EINVAL;
    2528                 goto err;
    2529         }
    2530 
    2531         ret = darray_make_room(&sbs, devices->nr);
    2532         if (ret)
    2533                 goto err;
    2534 
    2535         darray_for_each(*devices, i) {
    2536                 struct bch_sb_handle sb = { NULL };
    2537 
    2538                 ret = bch2_read_super(*i, opts, &sb);
    2539                 if (ret)
    2540                         goto err;
    2541 
    2542                 BUG_ON(darray_push(&sbs, sb));
    2543         }
    2544 
    2545         if (opts->nochanges && !opts->read_only) {
--> 2546                 ret = bch_err_throw(c, erofs_nochanges);
                                             ^
It hasn't been set yet.

    2547                 goto err_print;
    2548         }
    2549 
    2550         darray_for_each(sbs, sb)
    2551                 if (!best || sb_cmp(sb->sb, best->sb) > 0)
    2552                         best = sb;
    2553 
    2554         darray_for_each_reverse(sbs, sb) {
    2555                 ret = bch2_dev_in_fs(best, sb, opts);
    2556 
    2557                 if (ret == -BCH_ERR_device_has_been_removed ||
    2558                     ret == -BCH_ERR_device_splitbrain) {
    2559                         bch2_free_super(sb);
    2560                         darray_remove_item(&sbs, sb);
    2561                         best -= best > sb;
    2562                         ret = 0;
    2563                         continue;
    2564                 }
    2565 
    2566                 if (ret)
    2567                         goto err_print;
    2568         }
    2569 
    2570         c = bch2_fs_alloc(best->sb, opts, &sbs);
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
set here.

    2571         ret = PTR_ERR_OR_ZERO(c);
    2572         if (ret)
    2573                 goto err;
    2574 
    2575         scoped_guard(rwsem_write, &c->state_lock)
    2576                 darray_for_each(sbs, sb) {
    2577                         ret = bch2_dev_attach_bdev(c, sb);
    2578                         if (ret)
    2579                                 goto err;
    2580                 }
    2581 
    2582         if (!c->opts.nostart) {
    2583                 ret = bch2_fs_start(c);
    2584                 if (ret)
    2585                         goto err;
    2586         }
    2587 out:
    2588         darray_for_each(sbs, sb)
    2589                 bch2_free_super(sb);
    2590         darray_exit(&sbs);
    2591         module_put(THIS_MODULE);
    2592         return c;
    2593 err_print:
    2594         pr_err("bch_fs_open err opening %s: %s",
    2595                devices->data[0], bch2_err_str(ret));
    2596 err:
    2597         if (!IS_ERR_OR_NULL(c))
    2598                 bch2_fs_stop(c);
    2599         c = ERR_PTR(ret);
    2600         goto out;
    2601 }

regards,
dan carpenter