Re: [PATCH] btrfs: fix a possible umount deadlock

[Anand Jain <anand.jain@oracle.com>]

On 09/09/2016 08:53 PM, David Sterba wrote:
> On Fri, Sep 09, 2016 at 04:31:04PM +0800, Anand Jain wrote:
>>  static int __btrfs_close_devices(struct btrfs_fs_devices *fs_devices)
>>  {
>>  	struct btrfs_device *device, *tmp;
>> +	static LIST_HEAD(pending_put);
>
> Why is it static?

  sorry my mistake its typo. v2 is sent out.

Thanks, Anand


>> +	INIT_LIST_HEAD(&pending_put);
>>
>>  	if (--fs_devices->opened > 0)
>>  		return 0;
>> @@ -906,9 +904,24 @@ static int __btrfs_close_devices(struct btrfs_fs_devices *fs_devices)
>>  	mutex_lock(&fs_devices->device_list_mutex);
>>  	list_for_each_entry_safe(device, tmp, &fs_devices->devices, dev_list) {
>>  		btrfs_close_one_device(device);
>> +		list_add(&device->dev_list, &pending_put);
>>  	}
>>  	mutex_unlock(&fs_devices->device_list_mutex);
>>
>> +	/*
>> +	 * btrfs_show_devname() is using the device_list_mutex,
>> +	 * sometimes a call to blkdev_put() leads vfs calling
>> +	 * into this func. So do put outside of device_list_mutex,
>> +	 * as of now.
>> +	 */
>> +	while (!list_empty(&pending_put)) {
>> +		device = list_entry(pending_put.next,
>> +					struct btrfs_device, dev_list);
>> +		list_del(&device->dev_list);
>> +		btrfs_close_bdev(device);
>> +		call_rcu(&device->rcu, free_device);
>> +	}
>> +
>>  	WARN_ON(fs_devices->open_devices);
>>  	WARN_ON(fs_devices->rw_devices);
>>  	fs_devices->opened = 0;
> --
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