Re: [Qemu-devel] [PATCHv2 03/11] iscsi: add bdrv_co_is_allocated

[Peter Lieven <pl@kamp.de>]

Am 10.07.2013 16:43, schrieb Kevin Wolf:
> Am 10.07.2013 um 15:49 hat Peter Lieven geschrieben:
>> Am 10.07.2013 11:41, schrieb Kevin Wolf:
>>> Am 27.06.2013 um 15:11 hat Peter Lieven geschrieben:
>>>> this patch adds a coroutine for .bdrv_co_is_allocated as well as
>>>> a generic framework that can be used to build coroutines in block/iscsi.
>>>>
>>>> Signed-off-by: Peter Lieven <pl@kamp.de>
>>>> ---
>>>>  block/iscsi.c |  123 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>>>>  1 file changed, 123 insertions(+)
>>>>
>>>> diff --git a/block/iscsi.c b/block/iscsi.c
>>>> index 2e2455d..d31ee95 100644
>>>> --- a/block/iscsi.c
>>>> +++ b/block/iscsi.c
>>>> @@ -58,6 +58,15 @@ typedef struct IscsiLun {
>>>>      uint32_t max_unmap_bdc;
>>>>  } IscsiLun;
>>>>  
>>>> +typedef struct IscsiTask {
>>>> +    int status;
>>>> +    int complete;
>>>> +    int retries;
>>>> +    int do_retry;
>>>> +    struct scsi_task *task;
>>>> +    Coroutine *co;
>>>> +} IscsiTask;
>>>> +
>>>>  typedef struct IscsiAIOCB {
>>>>      BlockDriverAIOCB common;
>>>>      QEMUIOVector *qiov;
>>>> @@ -113,6 +122,45 @@ iscsi_schedule_bh(IscsiAIOCB *acb)
>>>>      qemu_bh_schedule(acb->bh);
>>>>  }
>>>>  
>>>> +static void
>>>> +iscsi_co_generic_cb(struct iscsi_context *iscsi, int status,
>>>> +                        void *command_data, void *opaque)
>>>> +{
>>>> +    struct IscsiTask *iTask = opaque;
>>>> +    struct scsi_task *task = command_data;
>>>> +
>>>> +    iTask->complete = 1;
>>>> +    iTask->status = status;
>>>> +    iTask->do_retry = 0;
>>>> +    iTask->task = task;
>>>> +
>>>> +    if (iTask->retries-- > 0 && status == SCSI_STATUS_CHECK_CONDITION
>>>> +        && task->sense.key == SCSI_SENSE_UNIT_ATTENTION) {
>>>> +        iTask->do_retry = 1;
>>>> +        goto out;
>>>> +    }
>>>> +
>>>> +    if (status != SCSI_STATUS_GOOD) {
>>>> +        error_report("iSCSI: Failure. %s", iscsi_get_error(iscsi));
>>>> +        goto out;
>>>> +    }
>>>> +
>>>> +out:
>>>> +    if (iTask->status != SCSI_STATUS_GOOD) {
>>>> +        scsi_free_scsi_task(iTask->task);
>>>> +        iTask->task = NULL;
>>>> +    }
>>>> +    if (iTask->co) {
>>>> +        qemu_coroutine_enter(iTask->co, NULL);
>>>> +    }
>>>> +}
>>> In which context does this callback run? If this is from a separate
>>> thread, you may not do all of this (without even holding the QBL). You
>>> should probably use a BH to switch to the I/O thread.
>> good question. the callbacks can only be fired when iscsi_service() is invoked.
>> this is currently done by registereing iscsi_process_read/write/flush via qemu_aio_set_fd_handler().
>>
>> so the callbacks are invoked in the aio context it seems. can this be right?
> Yes, I took another look and I think it's fine.
Would this still be true if all aio routines are replaced by coroutines?

Peter