Re: [PATCH 2/2] btrfs: fix vanished compression property after failed set

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

On 3/13/19 6:33 PM, Anand Jain wrote:
> 
> 
> 
> On 3/13/19 1:36 PM, Anand Jain wrote:
>> The compression property resets to NULL, instead of the old value if we
>> fail to set the new compression parameter.
>>
>> btrfs prop get /btrfs compression
>>    compression=lzo
>> btrfs prop set /btrfs compression zli
>>    ERROR: failed to set compression for /btrfs: Invalid argument
>> btrfs prop get /btrfs compression
>>
>> This is because the compression property ->validate() is successful for
>> 'zli' as the strncmp() used the len passed from the userland.
>>
>> Fix it by using the expected string length in strncmp().
>>
>> Signed-off-by: Anand Jain <anand.jain@oracle.com>
>> ---
>>   fs/btrfs/props.c | 6 +++---
>>   1 file changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/fs/btrfs/props.c b/fs/btrfs/props.c
>> index ef6502a94712..7aa362c2fbcf 100644
>> --- a/fs/btrfs/props.c
>> +++ b/fs/btrfs/props.c
>> @@ -277,11 +277,11 @@ static int prop_compression_validate(struct 
>> inode *inode, const char *value,
>>       if (!value)
>>           return 0;
>> -    if (!strncmp("lzo", value, len))
>> +    if (!strncmp("lzo", value, 3))
>>           return 0;
>> -    else if (!strncmp("zlib", value, len))
>> +    else if (!strncmp("zlib", value, 4))
>>           return 0;
>> -    else if (!strncmp("zstd", value, len))
>> +    else if (!strncmp("zstd", value, 4))
>>           return 0;
>>
> 
> 
>    Nack.
> Now some junk value after expected string is not an error.
> such as..
> 
> btrfs prop set /btrfs compression lzo110

  mount(8) compression and the property compression parameter have
  diverged, the compression levels are set able only from
  mount(8) option? We should rather make it consistent?

Thanks, Anand


> Thanks, Anand
> 
>>       return -EINVAL;
>>