[bug report] btrfs: scan but don't register device on single device filesystem

[bug report] btrfs: scan but don't register device on single device filesystem

[Dan Carpenter]

Hello Anand Jain,

The patch d41f57d15a90: "btrfs: scan but don't register device on
single device filesystem" from Sep 9, 2023 (linux-next), leads to the
following Smatch static checker warning:

	fs/btrfs/volumes.c:1420 btrfs_scan_one_device()
	error: uninitialized symbol 'devt'.

fs/btrfs/volumes.c
    1411         if (!mount_arg_dev && btrfs_super_num_devices(disk_super) == 1 &&
    1412             !(btrfs_super_flags(disk_super) & BTRFS_SUPER_FLAG_SEEDING)) {
    1413                 dev_t        devt;
    1414 
    1415                 ret = lookup_bdev(path, &devt);
    1416                 if (ret) {
    1417                         btrfs_warn(NULL, "lookup bdev failed for path %s: %d",
    1418                         path, ret);

Should this goto?

    1419                 }
--> 1420                 btrfs_free_stale_devices(devt, NULL);
                                                  ^^^^
Uninitialized if lookup_bdev() fails.

    1421 
    1422                 pr_debug("BTRFS (%s) skip registering single non seed device\n",
    1423                          path);
    1424                 device = NULL;
    1425                 goto free_disk_super;
    1426         }
    1427 
    1428         device = device_list_add(path, disk_super, &new_device_added);
    1429         if (!IS_ERR(device) && new_device_added)
    1430                 btrfs_free_stale_devices(device->devt, device);
    1431 
    1432 free_disk_super:
    1433         btrfs_release_disk_super(disk_super);
    1434 
    1435 error_bdev_put:
    1436         blkdev_put(bdev, NULL);
    1437 
    1438         return device;
    1439 }

regards,
dan carpenter

Re: [bug report] btrfs: scan but don't register device on single device filesystem

[Anand Jain]

Thanks for the report.

> 
> fs/btrfs/volumes.c
>      1411         if (!mount_arg_dev && btrfs_super_num_devices(disk_super) == 1 &&
>      1412             !(btrfs_super_flags(disk_super) & BTRFS_SUPER_FLAG_SEEDING)) {
>      1413                 dev_t        devt;
>      1414
>      1415                 ret = lookup_bdev(path, &devt);
>      1416                 if (ret) {
>      1417                         btrfs_warn(NULL, "lookup bdev failed for path %s: %d",
>      1418                         path, ret);
> 
> Should this goto?
> 
>      1419                 }
> --> 1420                 btrfs_free_stale_devices(devt, NULL);
>                                                    ^^^^
> Uninitialized if lookup_bdev() fails.

  We have to call btrfs_free_stale_devices() under the 'else' part;
  its the only one using devt.

  I have sent out the fix.

[PATCH] btrfs: fix smatch static checker warning in btrfs_scan_one_device


-Anand