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

[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 <address@hidden>
> >> ---
> >>  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.

Kevin