Am 09.03.2012 12:42, schrieb Stefan Hajnoczi:
> On Thu, Mar 8, 2012 at 10:15 PM, Leonardo E. Reiter
> <[email protected]> wrote:
>> +#ifndef _WIN32
>> +#include <sys/mman.h>
>
> I recommend writing this in a platform-independent way using bdrv_*()
> APIs to access the image file. This has been a requirement for all
> block drivers. Legacy drivers have been updated too. The chance of
> merging a new image format that uses platform-specific I/O APIs is low
> IMO.
Let's be clear here: It's not just low, it's zero.
Maybe the qcow2-cache should be generalised so that replacing an mmap in
other image formats becomes easier?
>> +BlockDriver bdrv_gow1 = {
>> + .format_name = "gow1",
>> + .instance_size = sizeof(gow1_state_t),
>> + .bdrv_probe = gow1_probe,
>> + .bdrv_file_open = gow1_open,
>> + .bdrv_close = gow1_close,
>> + .bdrv_read = gow1_read,
>> + .bdrv_write = gow1_write,
>
> Please implement .bdrv_co_readv()/.bdrv_co_writev() instead. They
> work along the same lines - except they allow parallel requests. If
> you don't want to handle parallel requests you can use a CoMutex to
> serialize these functions.
.bdrv_read/write allow parallel requests as well. The difference is that
bdrv_co_readv/writev is vectored and therefore preferable.
Kevin
