* [Qemu-devel] [PATCH v2] nbd/server: attach client channel to the export's AioContext
@ 2019-09-12 11:00 Sergio Lopez
2019-09-20 12:38 ` Eric Blake
2019-09-20 18:12 ` [Qemu-block] " John Snow
0 siblings, 2 replies; 6+ messages in thread
From: Sergio Lopez @ 2019-09-12 11:00 UTC (permalink / raw)
To: qemu-block; +Cc: kwolf, qemu-devel, Sergio Lopez
On creation, the export's AioContext is set to the same one as the
BlockBackend, while the AioContext in the client QIOChannel is left
untouched.
As a result, when using data-plane, nbd_client_receive_next_request()
schedules coroutines in the IOThread AioContext, while the client's
QIOChannel is serviced from the main_loop, potentially triggering the
assertion at qio_channel_restart_[read|write].
To fix this, as soon we have the export corresponding to the client,
we call qio_channel_attach_aio_context() to attach the QIOChannel
context to the export's AioContext. This matches with the logic at
blk_aio_attached().
RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=1748253
Signed-off-by: Sergio Lopez <slp@redhat.com>
---
Changelog
v2:
- Attach the channel once after negotiation completes, avoiding
duplication. (thanks Kevin Wolf).
---
nbd/server.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/nbd/server.c b/nbd/server.c
index 28c3c8be85..31d624e146 100644
--- a/nbd/server.c
+++ b/nbd/server.c
@@ -1297,6 +1297,11 @@ static coroutine_fn int nbd_negotiate(NBDClient *client, Error **errp)
return ret;
}
+ /* Attach the channel to the same AioContext as the export */
+ if (client->exp && client->exp->ctx) {
+ qio_channel_attach_aio_context(client->ioc, client->exp->ctx);
+ }
+
assert(!client->optlen);
trace_nbd_negotiate_success();
--
2.21.0
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH v2] nbd/server: attach client channel to the export's AioContext
2019-09-12 11:00 [Qemu-devel] [PATCH v2] nbd/server: attach client channel to the export's AioContext Sergio Lopez
@ 2019-09-20 12:38 ` Eric Blake
2019-09-20 18:12 ` [Qemu-block] " John Snow
1 sibling, 0 replies; 6+ messages in thread
From: Eric Blake @ 2019-09-20 12:38 UTC (permalink / raw)
To: Sergio Lopez, qemu-block; +Cc: kwolf, qemu-devel
[-- Attachment #1.1: Type: text/plain, Size: 1798 bytes --]
On 9/12/19 6:00 AM, Sergio Lopez wrote:
> On creation, the export's AioContext is set to the same one as the
> BlockBackend, while the AioContext in the client QIOChannel is left
> untouched.
>
> As a result, when using data-plane, nbd_client_receive_next_request()
> schedules coroutines in the IOThread AioContext, while the client's
> QIOChannel is serviced from the main_loop, potentially triggering the
> assertion at qio_channel_restart_[read|write].
>
> To fix this, as soon we have the export corresponding to the client,
> we call qio_channel_attach_aio_context() to attach the QIOChannel
> context to the export's AioContext. This matches with the logic at
> blk_aio_attached().
>
> RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=1748253
> Signed-off-by: Sergio Lopez <slp@redhat.com>
> ---
> Changelog
>
> v2:
> - Attach the channel once after negotiation completes, avoiding
> duplication. (thanks Kevin Wolf).
> ---
> nbd/server.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/nbd/server.c b/nbd/server.c
> index 28c3c8be85..31d624e146 100644
> --- a/nbd/server.c
> +++ b/nbd/server.c
> @@ -1297,6 +1297,11 @@ static coroutine_fn int nbd_negotiate(NBDClient *client, Error **errp)
> return ret;
> }
>
> + /* Attach the channel to the same AioContext as the export */
> + if (client->exp && client->exp->ctx) {
> + qio_channel_attach_aio_context(client->ioc, client->exp->ctx);
> + }
> +
Reviewed-by: Eric Blake <eblake@redhat.com>
Will queue through my NBD tree.
> assert(!client->optlen);
> trace_nbd_negotiate_success();
>
>
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3226
Virtualization: qemu.org | libvirt.org
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [Qemu-block] [PATCH v2] nbd/server: attach client channel to the export's AioContext
2019-09-12 11:00 [Qemu-devel] [PATCH v2] nbd/server: attach client channel to the export's AioContext Sergio Lopez
2019-09-20 12:38 ` Eric Blake
@ 2019-09-20 18:12 ` John Snow
2019-09-20 18:49 ` John Snow
1 sibling, 1 reply; 6+ messages in thread
From: John Snow @ 2019-09-20 18:12 UTC (permalink / raw)
To: Sergio Lopez, qemu-block; +Cc: kwolf, qemu-devel
On 9/12/19 7:00 AM, Sergio Lopez wrote:
> On creation, the export's AioContext is set to the same one as the
> BlockBackend, while the AioContext in the client QIOChannel is left
> untouched.
>
> As a result, when using data-plane, nbd_client_receive_next_request()
> schedules coroutines in the IOThread AioContext, while the client's
> QIOChannel is serviced from the main_loop, potentially triggering the
> assertion at qio_channel_restart_[read|write].
>
> To fix this, as soon we have the export corresponding to the client,
> we call qio_channel_attach_aio_context() to attach the QIOChannel
> context to the export's AioContext. This matches with the logic at
> blk_aio_attached().
>
> RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=1748253
> Signed-off-by: Sergio Lopez <slp@redhat.com>
> ---
> Changelog
>
> v2:
> - Attach the channel once after negotiation completes, avoiding
> duplication. (thanks Kevin Wolf).
> ---
> nbd/server.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/nbd/server.c b/nbd/server.c
> index 28c3c8be85..31d624e146 100644
> --- a/nbd/server.c
> +++ b/nbd/server.c
> @@ -1297,6 +1297,11 @@ static coroutine_fn int nbd_negotiate(NBDClient *client, Error **errp)
> return ret;
> }
>
> + /* Attach the channel to the same AioContext as the export */
> + if (client->exp && client->exp->ctx) {
> + qio_channel_attach_aio_context(client->ioc, client->exp->ctx);
> + }
> +
> assert(!client->optlen);
> trace_nbd_negotiate_success();
>
>
I assume this patch has been superseded by Eric's later patches?
--js
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [Qemu-block] [PATCH v2] nbd/server: attach client channel to the export's AioContext
2019-09-20 18:12 ` [Qemu-block] " John Snow
@ 2019-09-20 18:49 ` John Snow
2019-09-20 19:11 ` Eric Blake
0 siblings, 1 reply; 6+ messages in thread
From: John Snow @ 2019-09-20 18:49 UTC (permalink / raw)
To: Sergio Lopez, qemu-block; +Cc: kwolf, qemu-devel
On 9/20/19 2:12 PM, John Snow wrote:
>
>
> On 9/12/19 7:00 AM, Sergio Lopez wrote:
>> On creation, the export's AioContext is set to the same one as the
>> BlockBackend, while the AioContext in the client QIOChannel is left
>> untouched.
>>
>> As a result, when using data-plane, nbd_client_receive_next_request()
>> schedules coroutines in the IOThread AioContext, while the client's
>> QIOChannel is serviced from the main_loop, potentially triggering the
>> assertion at qio_channel_restart_[read|write].
>>
>> To fix this, as soon we have the export corresponding to the client,
>> we call qio_channel_attach_aio_context() to attach the QIOChannel
>> context to the export's AioContext. This matches with the logic at
>> blk_aio_attached().
>>
>> RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=1748253
>> Signed-off-by: Sergio Lopez <slp@redhat.com>
>> ---
>> Changelog
>>
>> v2:
>> - Attach the channel once after negotiation completes, avoiding
>> duplication. (thanks Kevin Wolf).
>> ---
>> nbd/server.c | 5 +++++
>> 1 file changed, 5 insertions(+)
>>
>> diff --git a/nbd/server.c b/nbd/server.c
>> index 28c3c8be85..31d624e146 100644
>> --- a/nbd/server.c
>> +++ b/nbd/server.c
>> @@ -1297,6 +1297,11 @@ static coroutine_fn int nbd_negotiate(NBDClient *client, Error **errp)
>> return ret;
>> }
>>
>> + /* Attach the channel to the same AioContext as the export */
>> + if (client->exp && client->exp->ctx) {
>> + qio_channel_attach_aio_context(client->ioc, client->exp->ctx);
>> + }
>> +
>> assert(!client->optlen);
>> trace_nbd_negotiate_success();
>>
>>
>
> I assume this patch has been superseded by Eric's later patches?
Nevermind -- my filtering got messed up slightly and I missed the
followup. I see that Eric staged this.
--js
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [Qemu-block] [PATCH v2] nbd/server: attach client channel to the export's AioContext
2019-09-20 18:49 ` John Snow
@ 2019-09-20 19:11 ` Eric Blake
2019-09-20 22:03 ` Eric Blake
0 siblings, 1 reply; 6+ messages in thread
From: Eric Blake @ 2019-09-20 19:11 UTC (permalink / raw)
To: John Snow, Sergio Lopez, qemu-block; +Cc: kwolf, qemu-devel
[-- Attachment #1.1: Type: text/plain, Size: 878 bytes --]
On 9/20/19 1:49 PM, John Snow wrote:
>
>>> To fix this, as soon we have the export corresponding to the client,
>>> we call qio_channel_attach_aio_context() to attach the QIOChannel
>>> context to the export's AioContext. This matches with the logic at
>>> blk_aio_attached().
>>>
>>
>> I assume this patch has been superseded by Eric's later patches?
>
> Nevermind -- my filtering got messed up slightly and I missed the
> followup. I see that Eric staged this.
I actually think both patches are needed: this one covers transactions,
while my later patch was on top of this to protect shutdown. But now
you've made me curious; I'll see if my patch hoisted in front still
solves everything, or if we really do need both.
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3226
Virtualization: qemu.org | libvirt.org
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [Qemu-block] [PATCH v2] nbd/server: attach client channel to the export's AioContext
2019-09-20 19:11 ` Eric Blake
@ 2019-09-20 22:03 ` Eric Blake
0 siblings, 0 replies; 6+ messages in thread
From: Eric Blake @ 2019-09-20 22:03 UTC (permalink / raw)
To: John Snow, Sergio Lopez, qemu-block; +Cc: kwolf, qemu-devel
[-- Attachment #1.1: Type: text/plain, Size: 1253 bytes --]
On 9/20/19 2:11 PM, Eric Blake wrote:
> On 9/20/19 1:49 PM, John Snow wrote:
>>
>
>>>> To fix this, as soon we have the export corresponding to the client,
>>>> we call qio_channel_attach_aio_context() to attach the QIOChannel
>>>> context to the export's AioContext. This matches with the logic at
>>>> blk_aio_attached().
>>>>
>
>>>
>>> I assume this patch has been superseded by Eric's later patches?
>>
>> Nevermind -- my filtering got messed up slightly and I missed the
>> followup. I see that Eric staged this.
>
> I actually think both patches are needed: this one covers transactions,
> while my later patch was on top of this to protect shutdown. But now
> you've made me curious; I'll see if my patch hoisted in front still
> solves everything, or if we really do need both.
>
Nope, both patches are still needed. Sergio's fixes the assertion:
(qemu) qemu-kvm: io/channel.c:411: qio_channel_restart_read:
Assertion `qemu_get_current_aio_context() ==
qemu_coroutine_get_aio_context(co)' failed.
while mine fixes:
+qemu: qemu_mutex_unlock_impl: Operation not permitted
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3226
Virtualization: qemu.org | libvirt.org
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^ permalink raw reply [flat|nested] 6+ messages in thread
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2019-09-12 11:00 [Qemu-devel] [PATCH v2] nbd/server: attach client channel to the export's AioContext Sergio Lopez
2019-09-20 12:38 ` Eric Blake
2019-09-20 18:12 ` [Qemu-block] " John Snow
2019-09-20 18:49 ` John Snow
2019-09-20 19:11 ` Eric Blake
2019-09-20 22:03 ` Eric Blake
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