Re: [Qemu-devel] [PATCH v4 2/8] Add socket_writev_buffer function

[Orit Wasserman <owasserm@redhat.com>]

On 03/21/2013 09:35 PM, Eric Blake wrote:
> On 03/21/2013 12:34 PM, Orit Wasserman wrote:
>> Signed-off-by: Orit Wasserman <owasserm@redhat.com>
>> ---
>>  savevm.c | 15 +++++++++++++++
>>  1 file changed, 15 insertions(+)
>>
>> diff --git a/savevm.c b/savevm.c
>> index 35c8d1e..6608b6e 100644
>> --- a/savevm.c
>> +++ b/savevm.c
>> @@ -39,6 +39,7 @@
>>  #include "qmp-commands.h"
>>  #include "trace.h"
>>  #include "qemu/bitops.h"
>> +#include "qemu/iov.h"
>>  
>>  #define SELF_ANNOUNCE_ROUNDS 5
>>  
>> @@ -171,6 +172,19 @@ static void coroutine_fn yield_until_fd_readable(int fd)
>>      qemu_coroutine_yield();
>>  }
>>  
>> +static int socket_writev_buffer(void *opaque, struct iovec *iov, int iovcnt)
> 
> Returning int...
> 
>> +{
>> +    QEMUFileSocket *s = opaque;
>> +    ssize_t len;
>> +    ssize_t size = iov_size(iov, iovcnt);
>> +
>> +    len = iov_send(s->fd, iov, iovcnt, 0, size);
>> +    if (len < size) {
>> +        len = -socket_error();
>> +    }
>> +    return len;
> 
> ...but len is an ssize_t.  If we send an iov with 2 gigabytes of data,
> this can wrap around to a negative int even though we send a positive
> amount of data.  Why not make the callback be typed to return ssize_t
> from the beginning (affects patch 1/8)?
At the moment it is not an issue but for the future we need to switch to ssize_t 
instead on int, I will change it.
We actually need to replace it all around the migration code but this should
be done in a different patch series.

Orit

>