Re: [PATCH v4 13/16] block/io: support int64_t bytes in bdrv_aligned_preadv()

[Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>]

22.01.2021 19:54, Eric Blake wrote:
> On 12/11/20 12:39 PM, Vladimir Sementsov-Ogievskiy wrote:
>> We are generally moving to int64_t for both offset and bytes parameters
>> on all io paths.
>>
>> Main motivation is realization of 64-bit write_zeroes operation for
>> fast zeroing large disk chunks, up to the whole disk.
>>
>> We chose signed type, to be consistent with off_t (which is signed) and
>> with possibility for signed return type (where negative value means
>> error).
>>
>> So, prepare bdrv_aligned_preadv() now.
>>
>> Make byte variable in bdrv_padding_rmw_read() int64_t, as it defined
>> only to be passed to bdrv_aligned_preadv().
> 
> Reads awkwardly, how about:
> 
> Make the byte variable in bdrv_padding_rmw_read() int64_t, as it is only
> used for pass-through to bdrv_aligned_preadv().

and also s/byte/bytes/

> 
>>
>> All bdrv_aligned_preadv() callers are safe as type is widening. Let's
>> look inside:
>>
>>   - add a new-style assertion that request is good.
>>   - callees bdrv_is_allocated(), bdrv_co_do_copy_on_readv() supports
>>     int64_t bytes
>>   - conversion of bytes_remaining is OK, as we never has requests
> 
> have
> 
>>     overflowing BDRV_MAX_LENGTH
>>   - looping through bytes_remaining is ok, num is updated to int64_t
>>     - for bdrv_driver_preadv we have same limit of max_transfer
>>     - qemu_iovec_memset is OK, as bytes+qiov_offset should not overflow
>>       qiov->size anyway (thanks to bdrv_check_qiov_request())
>>
>> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
>> ---
>>   block/io.c | 9 +++++----
>>   1 file changed, 5 insertions(+), 4 deletions(-)
>>
> 
> Reviewed-by: Eric Blake <eblake@redhat.com>
> 


-- 
Best regards,
Vladimir