> On Jun 16, 2015, at 7:18 PM, Josh Durgin <jdurgin@xxxxxxxxxx> wrote:
>
> On 06/12/2015 08:56 AM, Douglas Fuller wrote:
>>
>> @@ -3132,6 +3132,26 @@ static void rbd_watch_cb(u64 ver, u64 notify_id, u8 opcode, s32 return_code,
>> rbd_warn(rbd_dev, "notify_ack ret %d", ret);
>> }
>>
>> +static void rbd_watch_error_cb(void *arg, u64 cookie, int err)
>> +{
>> + struct rbd_device *rbd_dev = (struct rbd_device *)arg;
>> + int ret;
>> +
>> + dout("%s: watch error %d on cookie %llu\n", rbd_dev->header_name,
>> + err, cookie);
>> + rbd_warn(rbd_dev, "%s: watch error %d on cookie %llu\n",
>> + rbd_dev->header_name, err, cookie);
>> +
>> + /* reset watch */
>> + rbd_dev_refresh(rbd_dev);
>> + rbd_dev_header_unwatch_sync(rbd_dev);
>> + ret = rbd_dev_header_watch_sync(rbd_dev);
>> + BUG_ON(ret); /* XXX: was the image deleted? can we be more graceful? */
>> + rbd_dev_refresh(rbd_dev);
>
> Why refresh before and after unwatching? Only the second one seems
> necessary.
The first one isn’t strictly necessary; I can remove it if you want.
If we get a watch error, we may very well have a situation in which we need to stop I/O to the device because the underlying image has been deleted or its features have changed. We don’t actually do that yet (we just print a warning message), but the extra refresh was to handle that case early, even before we bothered trying to re-establish the watch.--
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