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From: Mike Christie <mchristi@redhat.com>
To: Yao Liu <yotta.liu@ucloud.cn>, Josef Bacik <josef@toxicpanda.com>
Cc: Jens Axboe <axboe@kernel.dk>,
	linux-block@vger.kernel.org, nbd@other.debian.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/3] nbd: notify userland even if nbd has already disconnected
Date: Tue, 28 May 2019 11:36:21 -0500	[thread overview]
Message-ID: <5CED6385.3000802@redhat.com> (raw)
In-Reply-To: <20190527182323.GB20702@192-168-150-246.7~>

On 05/27/2019 01:23 PM, Yao Liu wrote:
> On Fri, May 24, 2019 at 09:08:58AM -0400, Josef Bacik wrote:
>> On Fri, May 24, 2019 at 05:43:55PM +0800, Yao Liu wrote:
>>> Some nbd client implementations have a userland's daemon, so we should
>>> inform client daemon to clean up and exit.
>>>
>>> Signed-off-by: Yao Liu <yotta.liu@ucloud.cn>
>>
>> Except the nbd_disconnected() check is for the case that the client told us
>> specifically to disconnect, so we don't want to send the notification to
>> re-connect because we've already been told we want to tear everything down.
>> Nack to this as well.  Thanks,
>>
>> Josef
>>
> 
> But in userland, client daemon process and process which send disconnect
> command are not same process, so they are not clear to each other, so
> client daemon expect driver inform it to exit.
> In addition, client daemon will get nbd status with nbd_genl_status interface
> after it get notified and it should not re-connect if status connected == 0
> 

When using the netlink interface you get the NBD_CMD_LINK_DEAD first
then the configs_refs goes to zero right?

nbd_disconnect_and_put -> sock_shutdown -> nbd_mark_nsock_dead

then later we do the final nbd_config_put?

Maybe it would be best to add a new netlink event to signal what has
happened, because the above nl and stat algorithm seems like a pain. The
NBD_CMD_LINK_DEAD will be sent, then userspace has to possibly poll the
status to check if this was caused due to nbd_genl_disconnect instead of
a downed link due to something like a command timeout, because the
refcount may not be down when userspace gets the NL event.

Or, I guess the admin/tool process could just send a msg to the daemon
process to tell it to do the netlink disconnect request.

  reply	other threads:[~2019-05-28 16:36 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-24  9:43 [PATCH 1/3] nbd: fix connection timed out error after reconnecting to server Yao Liu
2019-05-24  9:43 ` [PATCH 2/3] nbd: notify userland even if nbd has already disconnected Yao Liu
2019-05-24 13:08   ` Josef Bacik
2019-05-27 18:23     ` Yao Liu
2019-05-28 16:36       ` Mike Christie [this message]
2019-05-28 20:05         ` Yao Liu
2019-05-28 16:54       ` Josef Bacik
2019-05-24  9:43 ` [PATCH 3/3] nbd: mark sock as dead even if it's the last one Yao Liu
2019-05-24 13:17   ` Josef Bacik
2019-05-27 18:29     ` Yao Liu
2019-05-24 13:07 ` [PATCH 1/3] nbd: fix connection timed out error after reconnecting to server Josef Bacik
2019-05-27 18:07   ` Yao Liu
2019-05-28 16:57     ` Josef Bacik
2019-05-28 19:04       ` Yao Liu
2019-05-29 13:49         ` Josef Bacik

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