Am 21.06.2013 18:31, schrieb Paolo Bonzini:
> Il 21/06/2013 13:07, Kevin Wolf ha scritto:
>>>>>> Note that you're blocking here. The preferred way would be something
>>>>>> involving a yield from the coroutine and a reenter as soon as all
>>>>>> requests are done. Maybe a CoRwLock does what you need?
>>>> Is there a document how to use it? Or can you help here?
>> The idea would be to take a read lock while any request is in flight
>> (i.e. qemu_co_rwlock_rdlock() before it's started and
>> qemu_co_rwlock_unlock() when it completes), and to take a write lock
>> (qemu_co_rwlock_wrlock) for the part of iscsi_co_is_allocated() that
>> requires that no other request runs in parallel.
>>
> You can just send the SCSI command asynchronously and wait for the
> result. There is an example in block/qed.c, the same would apply for iscsi.
thanks for the pointer paolo, this was i was looking for. this here seems to
work:
static void
iscsi_co_is_allocated_cb(struct iscsi_context *iscsi, int status,
void *command_data, void *opaque)
{
struct IscsiTask *iTask = opaque;
struct scsi_task *task = command_data;
struct scsi_get_lba_status *lbas = NULL;
iTask->complete = 1;
if (status != 0) {
error_report("iSCSI: Failed to get_lba_status on iSCSI lun. %s",
iscsi_get_error(iscsi));
iTask->status = 1;
goto out;
}
lbas = scsi_datain_unmarshall(task);
if (lbas == NULL) {
iTask->status = 1;
goto out;
}
memcpy(&iTask->lbasd, &lbas->descriptors[0],
sizeof(struct scsi_lba_status_descriptor));
iTask->status = 0;
out:
scsi_free_scsi_task(task);
if (iTask->co) {
qemu_coroutine_enter(iTask->co, NULL);
}
}
static int coroutine_fn iscsi_co_is_allocated(BlockDriverState *bs,
int64_t sector_num,
int nb_sectors, int *pnum)
{
IscsiLun *iscsilun = bs->opaque;
struct IscsiTask iTask;
int ret;
*pnum = nb_sectors;
if (iscsilun->lbpme == 0) {
return 1;
}
iTask.iscsilun = iscsilun;
iTask.status = 0;
iTask.complete = 0;
iTask.bs = bs;
if (iscsi_get_lba_status_task(iscsilun->iscsi, iscsilun->lun,
sector_qemu2lun(sector_num, iscsilun),
8 + 16, iscsi_co_is_allocated_cb,
&iTask) == NULL) {
*pnum = 0;
return 0;
}
while (!iTask.complete) {
iscsi_set_events(iscsilun);
iTask.co = qemu_coroutine_self();
qemu_coroutine_yield();
}
if (iTask.status != 0) {
/* in case the get_lba_status_callout fails (i.e.
* because the device is busy or the cmd is not
* supported) we pretend all blocks are allocated
* for backwards compatiblity */
return 1;
}
if (sector_qemu2lun(sector_num, iscsilun) != iTask.lbasd.lba) {
*pnum = 0;
return 0;
}
*pnum = iTask.lbasd.num_blocks * (iscsilun->block_size / BDRV_SECTOR_SIZE);
if (*pnum > nb_sectors) {
*pnum = nb_sectors;
}
return (iTask.lbasd.provisioning == SCSI_PROVISIONING_TYPE_MAPPED) ? 1 : 0;
return ret;
}
