On Fri, May 22, 2015 at 11:33:48PM +0800, Anand Jain wrote:
> +void btrfs_free_stale_device(struct btrfs_device *cur_dev)
> +{
> + int del = 0;
> + struct btrfs_fs_devices *fs_devs;
> + struct btrfs_device *dev;
> +
> + if (!rcu_str_deref(cur_dev->name))
> + return;
This looks like rcu-unprotected access, though there's an outer mutext
held in device_list_add that calls btrfs_free_stale_device. I'm not sure
that the device name should be used to do any sorts of checks at all.
> + list_for_each_entry(fs_devs, &fs_uuids, list) {
> + if (fs_devs->opened)
> + continue;
> + if (fs_devs->seeding)
> + continue;
> + list_for_each_entry(dev, &fs_devs->devices, dev_list) {
> + if (dev == cur_dev)
> + continue;
> +
> + /*
> + * Todo: This won't be enough. What if same device
> + * comes back with new uuid and with its mapper path?
> + * But for now, this does helps as mostly an admin will
> + * use either mapper or non mapper path throughout.
> + */
> + if (!rcu_str_deref(dev->name))
> + continue;
> + if (!strcmp(rcu_str_deref(dev->name),
> + rcu_str_deref(cur_dev->name))) {
> + del = 1;
> + break;
> + }
> + }
> + if (del) {
> + /* delete the stale */
> + if (fs_devs->num_devices == 1) {
> + btrfs_sysfs_remove_fsid(fs_devs);
> + list_del(&fs_devs->list);
> + free_fs_devices(fs_devs);
> + } else {
> + fs_devs->num_devices--;
> + list_del(&dev->dev_list);
> + rcu_string_free(dev->name);
> + kfree(dev);
Devices are normally freed by the rcu through free_device, this looks
suspicious to mix both approaches.
> + }
> + break;
> + }
> + }
> + return;
Unnecessary return
> +}
> +
> /*
> * Add new device to list of registered devices
> *
> @@ -560,6 +609,8 @@ static noinline int device_list_add(const char *path,
> if (!fs_devices->opened)
> device->generation = found_transid;
>
> + btrfs_free_stale_device(device);
It might be safe to do that in the end, but it should be explained
somewhere.
> +
> *fs_devices_ret = fs_devices;
>
> return ret;
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