Re: [Qemu-devel] [PATCH 1/2] iscsi: add support for bdrv_co_is_allocated()

[Peter Lieven]

Am 21.06.2013 11:18, schrieb Kevin Wolf:
> Am 20.06.2013 um 20:20 hat Peter Lieven geschrieben:
>> Signed-off-by: Peter Lieven <address@hidden>
>> ---
>>  block/iscsi.c |   57 
>> +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>>  1 file changed, 57 insertions(+)
>>
>> diff --git a/block/iscsi.c b/block/iscsi.c
>> index 0bbf0b1..e6b966d 100644
>> --- a/block/iscsi.c
>> +++ b/block/iscsi.c
>> @@ -49,6 +49,7 @@ typedef struct IscsiLun {
>>      uint64_t num_blocks;
>>      int events;
>>      QEMUTimer *nop_timer;
>> +    uint8_t lbpme;
>>  } IscsiLun;
>>  
>>  typedef struct IscsiAIOCB {
>> @@ -800,6 +801,60 @@ iscsi_getlength(BlockDriverState *bs)
>>      return len;
>>  }
>>  
>> +static int coroutine_fn iscsi_co_is_allocated(BlockDriverState *bs,
>> +                                              int64_t sector_num,
>> +                                              int nb_sectors, int *pnum)
>> +{
>> +    IscsiLun *iscsilun = bs->opaque;
>> +    struct scsi_task *task = NULL;
>> +    struct scsi_get_lba_status *lbas = NULL;
>> +    struct scsi_lba_status_descriptor *lbasd = NULL;
>> +    int ret;
>> +
>> +    *pnum = nb_sectors;
>> +
>> +    if (iscsilun->lbpme == 0) {
>> +        return 1;
>> +    }
>> +
>> +    /* in-flight requests could invalidate the lba status result */
>> +    while (iscsi_process_flush(iscsilun)) {
>> +        qemu_aio_wait();
>> +    }
> 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?
>
>> +
>> +    task = iscsi_get_lba_status_sync(iscsilun->iscsi, iscsilun->lun,
>> +                                     sector_qemu2lun(sector_num, iscsilun),
>> +                                     8+16);
> Spacing around operators (8 + 16)
Thanks, the checkpatch script didn't catch this.
>
>> +
>> +    if (task == NULL || task->status != SCSI_STATUS_GOOD) {
>> +        scsi_free_scsi_task(task);
>> +        return 1;
> Error cases should set *pnum = 0 and return 0.
In this special case, the target might not implement get_lba_status
or it might return SCSI_STATUS_BUSY. We shouldn't generate an
error or should we?

Peter