>>> Mike Christie <michael.chris...@oracle.com> schrieb am 08.10.2020 um 22:54
>>> in
Nachricht <47eca384-b54e-63cc-0f84-7ed6501f4...@oracle.com>:
> On 10/8/20 12:11 PM, Mike Christie wrote:
>> On 9/25/20 1:41 PM, ldun...@suse.com wrote:
>>> From: Lee Duncan <ldun...@suse.com>
>>>
>>> iSCSI NOPs are sometimes "lost", mistakenly sent to the
>>> user-land iscsid daemon instead of handled in the kernel,
>>> as they should be, resulting in a message from the daemon like:
>>>
>>>> iscsid: Got nop in, but kernel supports nop handling.
>>>
>>> This can occur because of the forward- and back-locks
>>> in the kernel iSCSI code, and the fact that an iSCSI NOP
>>> response can be processed before processing of the NOP send
>>> is complete. This can result in "conn->ping_task" being NULL
>>> in iscsi_nop_out_rsp(), when the pointer is actually in
>>> the process of being set.
>>>
>>> To work around this, we add a new state to the "ping_task"
>>> pointer. In addition to NULL (not assigned) and a pointer
>>> (assigned), we add the state "being set", which is signaled
>>> with an INVALID pointer (using "-1").
>>>
>>> Signed-off-by: Lee Duncan <ldun...@suse.com>
>>> ---
>>> drivers/scsi/libiscsi.c | 13 ++++++++++---
>>> include/scsi/libiscsi.h | 3 +++
>>> 2 files changed, 13 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/scsi/libiscsi.c b/drivers/scsi/libiscsi.c
>>> index 1e9c3171fa9f..cade108c33b6 100644
>>> --- a/drivers/scsi/libiscsi.c
>>> +++ b/drivers/scsi/libiscsi.c
>>> @@ -738,6 +738,9 @@ __iscsi_conn_send_pdu(struct iscsi_conn *conn, struct
> iscsi_hdr *hdr,
>>> task->conn->session->age);
>>> }
>>>
>>> + if (unlikely(READ_ONCE(conn->ping_task) == INVALID_SCSI_TASK))
>>> + WRITE_ONCE(conn->ping_task, task);
>>> +
>>> if (!ihost->workq) {
>>> if (iscsi_prep_mgmt_task(conn, task))
>>> goto free_task;
>>
>> I think the API gets a little weird now where in some cases
>> __iscsi_conn_send_pdu checks the opcode to see what type of request
>> it is but above we the caller sets the ping_task.
>>
>> For login, tmfs and passthrough, we assume the __iscsi_conn_send_pdu
>> has sent or cleaned up everything. I think it might be nicer to just
>> have __iscsi_conn_send_pdu set the ping_task field before doing the
>> xmit/queue call. It would then work similar to the conn->login_task
>> case where that function knows about that special task too.
>>
>> So in __iscsi_conn_send_pdu add a "if (opcode == ISCSI_OP_NOOP_OUT)",
>> and check if it's a nop we need to track. If so set conn->ping_task.
>>
> Ignore this. It won't work nicely either. To figure out if the nop is
> our internal transport test ping vs a userspace ping that also needs
> a reply, we would need to do something like you did above so there is
> no point.
I don't know the implementation details, but if ICMP package data would contain
some "unlikely" value for iSCSI pings, you could use the packet data to decide.
I guess 32 random bits could be "unlikely enough".
>
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