Re: [PATCH 1/2] btrfs-progs: convert: Prevent bit overflow for cctx->total_bytes

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On 2020/7/21 上午12:09, David Sterba wrote:
> On Mon, Jul 20, 2020 at 08:51:08PM +0800, Qu Wenruo wrote:
>> --- a/convert/source-ext2.c
>> +++ b/convert/source-ext2.c
>> @@ -87,7 +87,8 @@ static int ext2_open_fs(struct btrfs_convert_context *cctx, const char *name)
>>  	cctx->fs_data = ext2_fs;
>>  	cctx->blocksize = ext2_fs->blocksize;
>>  	cctx->block_count = ext2_fs->super->s_blocks_count;
>> -	cctx->total_bytes = ext2_fs->blocksize * ext2_fs->super->s_blocks_count;
>> +	cctx->total_bytes = (u64)ext2_fs->blocksize *
>> +			    (u64)ext2_fs->super->s_blocks_count;
> 
> Do you need to cast both? Once one of the types is wide enough for the
> result, there should be no loss.
> 
I just want to be extra safe.

Feel free to reduce one.

Thanks,
Qu

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