[v2] nbd/server: attach client channel to the export's AioContext
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Message ID 20190912110032.26395-1-slp@redhat.com
State New
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Series
  • [v2] nbd/server: attach client channel to the export's AioContext
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Commit Message

Sergio Lopez Sept. 12, 2019, 11 a.m. UTC
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(+)

Patch
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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();