Re: [PATCH 2/4] btrfs: lzo: Add comment about the how btrfs records its lzo compressed data

[Qu Wenruo <quwenruo.btrfs@gmx.com>]

On 2018年05月17日 15:48, Nikolay Borisov wrote:
> 
> 
> On 17.05.2018 09:27, Qu Wenruo wrote:
>> Signed-off-by: Qu Wenruo <wqu@suse.com>
> 
> Overall it looks good and useful just a couple of nits below.
>> ---
>>  fs/btrfs/lzo.c | 23 +++++++++++++++++++++++
>>  1 file changed, 23 insertions(+)
>>
>> diff --git a/fs/btrfs/lzo.c b/fs/btrfs/lzo.c
>> index 0667ea07f766..3d2ae4c08876 100644
>> --- a/fs/btrfs/lzo.c
>> +++ b/fs/btrfs/lzo.c
>> @@ -17,6 +17,29 @@
>>  
>>  #define LZO_LEN	4
>>  
>> +/*
>> + * Btrfs LZO compression format
>> + *
>> + * Regular LZO compressed data extent is consist of:
> nit: s/is consist/consists
>> + * 1.  Header
>> + *     Fixed size. LZO_LEN (4) bytes long, LE16.
>> + *     Records the total size (*includes* the header) of real compressed data.
>> + *
>> + * 2.  Segment(s)
>> + *     Variable size. Includes one segment header, and then data payload.
>> + *     One btrfs compressed data can have one or more segments.
> 
> So "one btrfs compressed data" should really mean "one btrfs compressed
> extent" I guess?

Oh, yes, one btrfs compressed extent.

Thanks,
Qu

> 
>> + *
>> + * 2.1 Segment header
>> + *     Fixed size. LZO_LEN (4) bytes long, LE16.
>> + *     Records the total size of the segment (*excludes* the header).
>> + *
>> + * 2.2 Data Payload
>> + *     Variable size. Size up limit should be lzo1x_worst_compress(PAGE_SIZE).
>> + *
>> + * While for inlined LZO compressed data extent, it doesn't have Header, just
>> + * one Segment.
> 
> 
> 
>> + */
>> +
>>  struct workspace {
>>  	void *mem;
>>  	void *buf;	/* where decompressed data goes */
>>
> --
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