Re: [PATCH v4 3/4] btrfs: add force_chunk_alloc sysfs entry to force allocation

[Stefan Roesch <shr@fb.com>]

On 11/5/21 3:04 AM, Nikolay Borisov wrote:
> 
> 
> On 29.10.21 г. 21:39, Stefan Roesch wrote:
>> This adds the force_chunk_alloc sysfs entry to be able to force a
>> storage allocation. This is a debugging and test feature and is
>> enabled with the CONFIG_BTRFS_DEBUG configuration option.
>>
>> It is stored at
>> /sys/fs/btrfs/<uuid>/allocation/<block_type>/force_chunk_alloc.
>> ---
>>  fs/btrfs/sysfs.c | 65 ++++++++++++++++++++++++++++++++++++++++++++++++
>>  1 file changed, 65 insertions(+)
>>
>> diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
>> index 3b0bcbc2ed2e..983c53b76aa6 100644
>> --- a/fs/btrfs/sysfs.c
>> +++ b/fs/btrfs/sysfs.c
>> @@ -771,6 +771,64 @@ static ssize_t btrfs_chunk_size_store(struct kobject *kobj,
>>  	return val;
>>  }
>>  
>> +#ifdef CONFIG_BTRFS_DEBUG
>> +/*
>> + * Return if space info force allocation chunk flag is set.
> 
> nit: Well this is a dummy function which simply returns 0. I guess what
> makes sense is to simply make the show op a NULL, i wonder if sysfs can
> handle this gracefully though.
> 
> <snip>
>

This is possible however I need to also change the file mask, so the user can
only write to the file. I'll make the change.