Re: [PATCH v2] btrfs-progs: receive: fix unused variable warning without LZO

[liuh <liuhuan01@kylinos.cn>]

在 2026/9/30 12:59, Qu Wenruo 写道:
>
>
> 在 2026/9/30 11:51, liuh0329 写道:
>> When btrfs-progs is built without LZO support, sector_shift is still
>> declared in decompress_and_write(), while all its uses are guarded by
>> COMPRESSION_LZO. This results in an unused variable warning.
>>
>> Move the sector_shift declaration to the LZO-specific code path so it is
>> only declared when LZO support is enabled.
>>
>> Fixes: 345731fff32d ("btrfs-progs: receive: optional build for lzo, 
>> zstd")
>> Signed-off-by: liuh0329 <liuhuan01@kylinos.cn>
>>
>> ---
>> Changes in v2:
>> - Move sector_shift declaration to its only usage, as suggested by Qu 
>> Wenruo.
>> - Add a local scope for sector_shift.
>>
>>   cmds/receive.c | 18 ++++++++++--------
>>   1 file changed, 10 insertions(+), 8 deletions(-)
>>
>> diff --git a/cmds/receive.c b/cmds/receive.c
>> index 49103ea3..02c864a6 100644
>> --- a/cmds/receive.c
>> +++ b/cmds/receive.c
>> @@ -1186,7 +1186,6 @@ static int decompress_and_write(struct 
>> btrfs_receive *rctx,
>>   {
>>       int ret = 0;
>>       char *unencoded_data;
>> -    int sector_shift = 0;
>>       u64 written = 0;
>>         unencoded_data = calloc(unencoded_len, 1);
>> @@ -1220,13 +1219,16 @@ static int decompress_and_write(struct 
>> btrfs_receive *rctx,
>>       case BTRFS_ENCODED_IO_COMPRESSION_LZO_32K:
>>       case BTRFS_ENCODED_IO_COMPRESSION_LZO_64K:
>>   #if COMPRESSION_LZO
>> -        sector_shift =
>> -            compression - BTRFS_ENCODED_IO_COMPRESSION_LZO_4K + 12;
>> -        ret = decompress_lzo(encoded_data, encoded_len, unencoded_data,
>> -                     unencoded_len, 1U << sector_shift);
>> -        if (ret)
>> -            goto out;
>> -        break;
>> +        {
>
> Why? Why not just simply do the following?

Thanks, that is simpler. I'll drop the extra scope and move the 
declaration directly to its only usage in v3.

> diff --git a/cmds/receive.c b/cmds/receive.c
> index 49103ea3eeea..f592a044801d 100644
> --- a/cmds/receive.c
> +++ b/cmds/receive.c
> @@ -1186,7 +1186,6 @@ static int decompress_and_write(struct 
> btrfs_receive *rctx,
>  {
>         int ret = 0;
>         char *unencoded_data;
> -       int sector_shift = 0;
>         u64 written = 0;
>
>         unencoded_data = calloc(unencoded_len, 1);
> @@ -1220,7 +1219,7 @@ static int decompress_and_write(struct 
> btrfs_receive *rctx,
>         case BTRFS_ENCODED_IO_COMPRESSION_LZO_32K:
>         case BTRFS_ENCODED_IO_COMPRESSION_LZO_64K:
>  #if COMPRESSION_LZO
> -               sector_shift =
> +               int sector_shift =
>                         compression - 
> BTRFS_ENCODED_IO_COMPRESSION_LZO_4K + 12;
>                 ret = decompress_lzo(encoded_data, encoded_len, 
> unencoded_data,
>                                      unencoded_len, 1U << sector_shift);
>
>
>> +            int sector_shift =
>> +                compression - BTRFS_ENCODED_IO_COMPRESSION_LZO_4K + 12;
>> +
>> +            ret = decompress_lzo(encoded_data, encoded_len, 
>> unencoded_data,
>> +                         unencoded_len, 1U << sector_shift);
>> +            if (ret)
>> +                goto out;
>> +            break;
>> +        }
>>   #else
>>           error("LZO compression for stream not compiled in");
>>           ret = -EOPNOTSUPP;
>