Re: [Qemu-devel] [PATCH] block/iscsi: cancel libiscsi task when ABORT TASK TMF completes

[Stefan Hajnoczi]

On Tue, Feb 20, 2018 at 3:12 PM, Peter Lieven  wrote:
> Am 15.02.2018 um 18:27 schrieb Stefan Hajnoczi:
>>
>> On Thu, Feb 15, 2018 at 03:24:54PM +0100, Peter Lieven wrote:
>>>
>>> Am 15.02.2018 um 12:15 schrieb Stefan Hajnoczi:

 The libiscsi iscsi_task_mgmt_async() API documentation says:

 abort_task will also cancel the scsi task. The callback for the scsi
 task will be invoked with SCSI_STATUS_CANCELLED

 The libiscsi implementation does not fulfil this promise.  The task's
 callback is not invoked and its struct iscsi_pdu remains in the internal
 list (effectively leaked).
>>>
>>> If that contract is fixed in libiscsi, will the Qemu iSCSI driver still
>>> work?
>>
>> In
>>
>> +/* If the command callback hasn't been called yet, drop the task */
>> +if (!acb->bh) {
>>
>> and
>>
>> +if (status == SCSI_STATUS_CANCELLED) {
>> +if (!acb->bh) {
>>
>> we're mindful of the fact that the callback may have been invoked by
>> libiscsi already.  There is no risk of double-completion.
>
>
> Hi Stefan,
>
> thanks for the clarification. I am fine with this change. I will check with
> Ronnie for the
> libiscsi fix.

Great, then this patch can go via Paolo's SCSI tree.

Stefan

Re: [Qemu-devel] [PATCH] block/iscsi: cancel libiscsi task when ABORT TASK TMF completes

[Peter Lieven]

Am 15.02.2018 um 18:27 schrieb Stefan Hajnoczi:

On Thu, Feb 15, 2018 at 03:24:54PM +0100, Peter Lieven wrote:

Am 15.02.2018 um 12:15 schrieb Stefan Hajnoczi:

The libiscsi iscsi_task_mgmt_async() API documentation says:

abort_task will also cancel the scsi task. The callback for the scsi
task will be invoked with SCSI_STATUS_CANCELLED

The libiscsi implementation does not fulfil this promise.  The task's
callback is not invoked and its struct iscsi_pdu remains in the internal
list (effectively leaked).

If that contract is fixed in libiscsi, will the Qemu iSCSI driver still work?

In

+/* If the command callback hasn't been called yet, drop the task */
+if (!acb->bh) {

and

+if (status == SCSI_STATUS_CANCELLED) {
+if (!acb->bh) {

we're mindful of the fact that the callback may have been invoked by
libiscsi already.  There is no risk of double-completion.


Hi Stefan,

thanks for the clarification. I am fine with this change. I will check with 
Ronnie for the
libiscsi fix.

Peter

Re: [Qemu-devel] [PATCH] block/iscsi: cancel libiscsi task when ABORT TASK TMF completes

[Stefan Hajnoczi]

On Thu, Feb 15, 2018 at 03:24:54PM +0100, Peter Lieven wrote:
> Am 15.02.2018 um 12:15 schrieb Stefan Hajnoczi:
> > The libiscsi iscsi_task_mgmt_async() API documentation says:
> > 
> >abort_task will also cancel the scsi task. The callback for the scsi
> >task will be invoked with SCSI_STATUS_CANCELLED
> > 
> > The libiscsi implementation does not fulfil this promise.  The task's
> > callback is not invoked and its struct iscsi_pdu remains in the internal
> > list (effectively leaked).
> 
> If that contract is fixed in libiscsi, will the Qemu iSCSI driver still work?

In

+/* If the command callback hasn't been called yet, drop the task */
+if (!acb->bh) {

and

+if (status == SCSI_STATUS_CANCELLED) {
+if (!acb->bh) {

we're mindful of the fact that the callback may have been invoked by
libiscsi already.  There is no risk of double-completion.

Stefan


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Re: [Qemu-devel] [PATCH] block/iscsi: cancel libiscsi task when ABORT TASK TMF completes

[Peter Lieven]

Am 15.02.2018 um 12:15 schrieb Stefan Hajnoczi:

The libiscsi iscsi_task_mgmt_async() API documentation says:

   abort_task will also cancel the scsi task. The callback for the scsi
   task will be invoked with SCSI_STATUS_CANCELLED

The libiscsi implementation does not fulfil this promise.  The task's
callback is not invoked and its struct iscsi_pdu remains in the internal
list (effectively leaked).


If that contract is fixed in libiscsi, will the Qemu iSCSI driver still work?

Peter

[Qemu-devel] [PATCH] block/iscsi: cancel libiscsi task when ABORT TASK TMF completes

[Stefan Hajnoczi]

The libiscsi iscsi_task_mgmt_async() API documentation says:

  abort_task will also cancel the scsi task. The callback for the scsi
  task will be invoked with SCSI_STATUS_CANCELLED

The libiscsi implementation does not fulfil this promise.  The task's
callback is not invoked and its struct iscsi_pdu remains in the internal
list (effectively leaked).

This patch invokes the libiscsi iscsi_scsi_cancel_task() API to force
the task's callback to be invoked with SCSI_STATUS_CANCELLED when the
ABORT TASK TMF completes and the task's callback hasn't been invoked
yet.

Signed-off-by: Stefan Hajnoczi 
---
 block/iscsi.c | 16 ++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/block/iscsi.c b/block/iscsi.c
index 41e67cb371..4cb188ac2b 100644
--- a/block/iscsi.c
+++ b/block/iscsi.c
@@ -292,8 +292,12 @@ iscsi_abort_task_cb(struct iscsi_context *iscsi, int 
status, void *command_data,
 {
 IscsiAIOCB *acb = private_data;
 
-acb->status = -ECANCELED;
-iscsi_schedule_bh(acb);
+/* If the command callback hasn't been called yet, drop the task */
+if (!acb->bh) {
+/* Call iscsi_aio_ioctl_cb() with SCSI_STATUS_CANCELLED */
+iscsi_scsi_cancel_task(iscsi, acb->task);
+}
+
 qemu_aio_unref(acb); /* acquired in iscsi_aio_cancel() */
 }
 
@@ -941,6 +945,14 @@ iscsi_aio_ioctl_cb(struct iscsi_context *iscsi, int status,
 {
 IscsiAIOCB *acb = opaque;
 
+if (status == SCSI_STATUS_CANCELLED) {
+if (!acb->bh) {
+acb->status = -ECANCELED;
+iscsi_schedule_bh(acb);
+}
+return;
+}
+
 acb->status = 0;
 if (status < 0) {
 error_report("Failed to ioctl(SG_IO) to iSCSI lun. %s",
-- 
2.14.3