From: Eric Blake <eblake@redhat.com>
To: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Cc: kwolf@redhat.com, pbonzini@redhat.com, qemu-devel@nongnu.org,
qemu-block@nongnu.org, mreitz@redhat.com
Subject: Re: [PATCH v4 20/32] nbd/client-connection: implement connection retry
Date: Mon, 22 Nov 2021 15:51:45 -0600 [thread overview]
Message-ID: <20211122215145.wf2dqyhsc5zt6wbm@redhat.com> (raw)
In-Reply-To: <fca77dff-caba-907b-6ab2-91ed9987760f@virtuozzo.com>
On Mon, Nov 22, 2021 at 08:17:34PM +0300, Vladimir Sementsov-Ogievskiy wrote:
> 22.11.2021 19:30, Eric Blake wrote:
> > Reviving this thread, as a good as place as any for my question:
> >
> > But I can't
> > find anywhere in the code base that ensures that on a reconnect, the
> > new server supplies at least as many extensions as the original
> > server, nor anywhere that we would be able to gracefully handle an
> > in-flight block status command that can no longer be successfully
> > continued because the reconnect landed on a downgraded server.
> >
>
> Yes that's a problem. We previously noted it here https://lists.gnu.org/archive/html/qemu-block/2021-06/msg00458.html
Aha! And oops that we've let it slide this long. But now that we
know the problem was also present in 6.1, and not a new regression in
6.2, it is less urgent to get a fix in. If we get one written in
time, it's still game for inclusion for -rc2 or maybe -rc3, but as we
get further along in the process, it should not hold up the final
release (it would not be -rc4 material, for example).
>
> Honestly, I didn't start any fix for that :(.. I agree, it would be good to fix it somehow in 6.2. I'll try to make something simple this week. Or did you already started doing some fix?
I haven't started writing anything on the topic. I've got some
patches that I hope to post soon targetting 7.0 that allow an
extension for NBD_CMD_BLOCK_STATUS to do a full round-trip 64-bit
operation, which is why I noticed it (if the 64-bit extension is not
present on reconnect, we have a problem - but it's no worse than the
existing problems). But I'm currently so focused on getting the new
feature interoperating between qemu, libnbd, and nbdkit, plus the US
Thanksgiving break this week, that I'm happy to let you take first
shot at client-side validation that a server reconnect does not lose
capabilities.
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
next prev parent reply other threads:[~2021-11-22 21:53 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-10 10:07 [PATCH v4 00/32] block/nbd: rework client connection Vladimir Sementsov-Ogievskiy
2021-06-10 10:07 ` [PATCH v4 01/32] co-queue: drop extra coroutine_fn marks Vladimir Sementsov-Ogievskiy
2021-06-10 17:22 ` Eric Blake
2021-06-10 17:37 ` Vladimir Sementsov-Ogievskiy
2021-06-10 10:07 ` [PATCH v4 02/32] block/nbd: fix channel object leak Vladimir Sementsov-Ogievskiy
2021-06-10 10:07 ` [PATCH v4 03/32] block/nbd: fix how state is cleared on nbd_open() failure paths Vladimir Sementsov-Ogievskiy
2021-06-10 10:07 ` [PATCH v4 04/32] block/nbd: connect_thread_func(): do qio_channel_set_delay(false) Vladimir Sementsov-Ogievskiy
2021-06-10 18:37 ` Eric Blake
2021-06-10 10:07 ` [PATCH v4 05/32] qemu-sockets: introduce socket_address_parse_named_fd() Vladimir Sementsov-Ogievskiy
2021-06-11 13:22 ` Eric Blake
2021-06-11 14:10 ` Vladimir Sementsov-Ogievskiy
2021-06-10 10:07 ` [PATCH v4 06/32] block/nbd: call socket_address_parse_named_fd() in advance Vladimir Sementsov-Ogievskiy
2021-06-11 13:54 ` Eric Blake
2021-06-10 10:07 ` [PATCH v4 07/32] block/nbd: ensure ->connection_thread is always valid Vladimir Sementsov-Ogievskiy
2021-06-10 10:07 ` [PATCH v4 08/32] block/nbd: nbd_client_handshake(): fix leak of s->ioc Vladimir Sementsov-Ogievskiy
2021-06-10 10:07 ` [PATCH v4 09/32] block/nbd: BDRVNBDState: drop unused connect_err and connect_status Vladimir Sementsov-Ogievskiy
2021-06-10 10:07 ` [PATCH v4 10/32] block/nbd: simplify waking of nbd_co_establish_connection() Vladimir Sementsov-Ogievskiy
2021-06-11 14:06 ` Eric Blake
2021-06-10 10:07 ` [PATCH v4 11/32] block/nbd: drop thr->state Vladimir Sementsov-Ogievskiy
2021-06-11 14:25 ` Eric Blake
2021-06-10 10:07 ` [PATCH v4 12/32] block/nbd: bs-independent interface for nbd_co_establish_connection() Vladimir Sementsov-Ogievskiy
2021-06-10 10:07 ` [PATCH v4 13/32] block/nbd: make nbd_co_establish_connection_cancel() bs-independent Vladimir Sementsov-Ogievskiy
2021-06-10 10:07 ` [PATCH v4 14/32] block/nbd: rename NBDConnectThread to NBDClientConnection Vladimir Sementsov-Ogievskiy
2021-06-10 10:07 ` [PATCH v4 15/32] block/nbd: introduce nbd_client_connection_new() Vladimir Sementsov-Ogievskiy
2021-06-10 10:07 ` [PATCH v4 16/32] block/nbd: introduce nbd_client_connection_release() Vladimir Sementsov-Ogievskiy
2021-06-11 14:28 ` Eric Blake
2021-06-10 10:07 ` [PATCH v4 17/32] nbd: move connection code from block/nbd to nbd/client-connection Vladimir Sementsov-Ogievskiy
2021-06-10 10:07 ` [PATCH v4 18/32] nbd/client-connection: use QEMU_LOCK_GUARD Vladimir Sementsov-Ogievskiy
2021-06-11 14:31 ` Eric Blake
2021-06-10 10:07 ` [PATCH v4 19/32] nbd/client-connection: add possibility of negotiation Vladimir Sementsov-Ogievskiy
2021-06-11 15:07 ` Eric Blake
2021-06-10 10:07 ` [PATCH v4 20/32] nbd/client-connection: implement connection retry Vladimir Sementsov-Ogievskiy
2021-06-11 15:12 ` Eric Blake
2021-11-22 16:30 ` Eric Blake
2021-11-22 17:17 ` Vladimir Sementsov-Ogievskiy
2021-11-22 21:51 ` Eric Blake [this message]
2021-06-10 10:07 ` [PATCH v4 21/32] nbd/client-connection: shutdown connection on release Vladimir Sementsov-Ogievskiy
2021-06-11 15:27 ` Eric Blake
2021-06-10 10:07 ` [PATCH v4 22/32] block/nbd: split nbd_handle_updated_info out of nbd_client_handshake() Vladimir Sementsov-Ogievskiy
2021-06-10 10:07 ` [PATCH v4 23/32] block/nbd: use negotiation of NBDClientConnection Vladimir Sementsov-Ogievskiy
2021-06-10 10:07 ` [PATCH v4 24/32] block/nbd: don't touch s->sioc in nbd_teardown_connection() Vladimir Sementsov-Ogievskiy
2021-06-10 10:07 ` [PATCH v4 25/32] block/nbd: drop BDRVNBDState::sioc Vladimir Sementsov-Ogievskiy
2021-06-10 10:07 ` [PATCH v4 26/32] nbd/client-connection: return only one io channel Vladimir Sementsov-Ogievskiy
2021-06-10 10:07 ` [PATCH v4 27/32] block-coroutine-wrapper: allow non bdrv_ prefix Vladimir Sementsov-Ogievskiy
2021-06-10 10:07 ` [PATCH v4 28/32] block/nbd: split nbd_co_do_establish_connection out of nbd_reconnect_attempt Vladimir Sementsov-Ogievskiy
2021-06-11 15:29 ` Eric Blake
2021-06-10 10:07 ` [PATCH v4 29/32] nbd/client-connection: add option for non-blocking connection attempt Vladimir Sementsov-Ogievskiy
2021-06-10 10:08 ` [PATCH v4 30/32] block/nbd: reuse nbd_co_do_establish_connection() in nbd_open() Vladimir Sementsov-Ogievskiy
2021-06-10 10:08 ` [PATCH v4 31/32] block/nbd: add nbd_client_connected() helper Vladimir Sementsov-Ogievskiy
2021-06-10 10:08 ` [PATCH v4 32/32] block/nbd: safer transition to receiving request Vladimir Sementsov-Ogievskiy
2021-06-11 15:55 ` [PATCH v4 00/32] block/nbd: rework client connection Eric Blake
2021-06-11 17:23 ` Vladimir Sementsov-Ogievskiy
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