Re: [PATCH v6 2/3] btrfs: remove unused device_list_mutex for seed fs_devices

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

On 21/09/2021 14:44, Nikolay Borisov wrote:
> 
> 
> On 21.09.21 г. 7:33, Anand Jain wrote:
>> The btrfs_fs_devices::seed_list is of type btrfs_fs_devices as well and,
> 
> seed_list is in fact a list_head which points to btrfs_fs_devices, so
> that sentence is somewhat misleading.
> 
>> it is a pointer to the seed btrfs_fs_device in a btrfs created from a
>> seed devices.
>> In this struct, when it points to seed, the device_list_mutex is not
>> used. So drop its initialize.
> 
> Even if the device_list_mutex is not used in the seed_devices it will
> have whatever is the state from the original fs_devices so
> re-initializing it to a sane state is the right thing to do.
> 
> We don't need this.

  I agree. Maybe at some point, we should have a separate new struct for 
the seed's fs_devices, as few members in it aren't in use.

  We can drop this patch.

Thanks, Anand

> 
>>
>> Signed-off-by: Anand Jain <anand.jain@oracle.com>
>> ---
>> v6: new
>>   fs/btrfs/volumes.c | 1 -
>>   1 file changed, 1 deletion(-)
>>
>> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
>> index c4bc49e58b69..e4079e25db70 100644
>> --- a/fs/btrfs/volumes.c
>> +++ b/fs/btrfs/volumes.c
>> @@ -2418,7 +2418,6 @@ static int btrfs_prepare_sprout(struct btrfs_fs_info *fs_info)
>>   	seed_devices->opened = 1;
>>   	INIT_LIST_HEAD(&seed_devices->devices);
>>   	INIT_LIST_HEAD(&seed_devices->alloc_list);
>> -	mutex_init(&seed_devices->device_list_mutex);
>>   
>>   	mutex_lock(&fs_devices->device_list_mutex);
>>   	list_splice_init_rcu(&fs_devices->devices, &seed_devices->devices,
>>