[Libguestfs] [libnbd PATCH 4/6] states: Prepare for aio notify callback

[Eric Blake]

On 7/18/19 9:22 AM, Eric Blake wrote:
> On 6/29/19 8:28 AM, Eric Blake wrote:
> 
>>
>> We also want the client to be aware of any issued/in-flight commands
>> that failed because they were stranded when the state machine moved to
>> CLOSED or DEAD.  Previously, nbd_aio_command_completed() would never
>> locate such stranded commands, but adding a common point to fire the
>> notifier for such commands makes it also possible to move those
>> commands to the completion queue.
>>
> 
>> +++ b/generator/states.c
>> @@ -111,6 +111,31 @@ send_from_wbuf (struct nbd_handle *h)
>>    return 0;                     /* move to next state */
>>  }
>>
>> +/* Forcefully fail any remaining in-flight commands in list */
>> +void abort_commands (struct nbd_handle *h,
>> +                     struct command_in_flight **list)
>> +{
>> +  struct command_in_flight *prev_cmd, *cmd;
>> +
>> +  for (cmd = *list, prev_cmd = NULL;
>> +       cmd != NULL;
>> +       prev_cmd = cmd, cmd = cmd->next) {
>> +    if (cmd->cb.notify && cmd->type != NBD_CMD_DISC) {
>> +      int error = cmd->error ? cmd->error : ENOTCONN;
>> +
>> +      if (cmd->cb.notify (cmd->cb.opaque, cmd->handle, &error) == -1 && error)
>> +        cmd->error = error;
>> +    }
>> +    if (cmd->error == 0)
>> +      cmd->error = ENOTCONN;
>> +  }
>> +  if (prev_cmd) {
>> +    prev_cmd->next = h->cmds_done;
>> +    h->cmds_done = *list;
>> +    *list = NULL;
>> +  }
> 
> This inserts the list to the head of cmds_done, which breaks its use as
> a FIFO queue for clients using nbd_aio_peek_command_completed to process
> messages in server order. I'll post a fix that keeps things in order.

It also failed to keep in_flight up-to-date.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org

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