Re: [PATCH] nvme: fix reconnection fail due to reserved tag allocation

[Sagi Grimberg]

On 07/03/2024 12:32, 许春光 wrote:
> Thanks for review, seems that we should revert this patch
> ed01fee283a0, ed01fee283a0 seems just a alone 'optimization'.  If no
> double, I will send another patch.

Not a revert, but a fix with a Fixes tag. Just use 
NVMF_ADMIN_RESERVED_TAGS and NVMF_IO_RESERVED_TAGS.


> Thanks
>
> Sagi Grimberg <sagi@xxxxxxxxxxx> 于2024年3月7日周四 17:36写道：
> > On 28/02/2024 11:14, brookxu.cn wrote:
> > > From: Chunguang Xu <chunguang.xu@xxxxxxxxxx>
> > >
> > > We found a issue on production environment while using NVMe
> > > over RDMA, admin_q reconnect failed forever while remote
> > > target and network is ok. After dig into it, we found it
> > > may caused by a ABBA deadlock due to tag allocation. In my
> > > case, the tag was hold by a keep alive request waiting
> > > inside admin_q, as we quiesced admin_q while reset ctrl,
> > > so the request maked as idle and will not process before
> > > reset success. As fabric_q shares tagset with admin_q,
> > > while reconnect remote target, we need a tag for connect
> > > command, but the only one reserved tag was held by keep
> > > alive command which waiting inside admin_q. As a result,
> > > we failed to reconnect admin_q forever.
> > >
> > > In order to workaround this issue, I think we should not
> > > retry keep alive request while controller reconnecting,
> > > as we have stopped keep alive while resetting controller,
> > > and will start it again while init finish, so it maybe ok
> > > to drop it.
> > This is the wrong fix.
> > First we should note that this is a regression caused by:
> > ed01fee283a0 ("nvme-fabrics: only reserve a single tag")
> >
> > Then, you need to restore reserving two tags for the admin
> > tagset.