[PATCH RFC 4/9] migration/rdma: Change io_create_watch() to return immediately

[Peter Xu <peterx@redhat.com>]

The old RDMA's io_create_watch() isn't really doing much work anyway.  For
G_IO_OUT, it already does return immediately.  For G_IO_IN, it will try to
detect some RDMA context length however normally nobody will be able to set
it at all.

Simplify the code so that RDMA iochannels simply always rely on synchronous
reads and writes.  It is highly likely what 6ddd2d76ca6f86f was talking
about, that the async model isn't really working well.

This helps because this is almost the only dependency that the migration
core would need a coroutine for rdma channels.

Signed-off-by: Peter Xu <peterx@redhat.com>
---
 migration/rdma.c | 69 +++---------------------------------------------
 1 file changed, 3 insertions(+), 66 deletions(-)

diff --git a/migration/rdma.c b/migration/rdma.c
index ed4e20b988..bcd7aae2f2 100644
--- a/migration/rdma.c
+++ b/migration/rdma.c
@@ -2789,56 +2789,14 @@ static gboolean
 qio_channel_rdma_source_prepare(GSource *source,
                                 gint *timeout)
 {
-    QIOChannelRDMASource *rsource = (QIOChannelRDMASource *)source;
-    RDMAContext *rdma;
-    GIOCondition cond = 0;
     *timeout = -1;
-
-    RCU_READ_LOCK_GUARD();
-    if (rsource->condition == G_IO_IN) {
-        rdma = qatomic_rcu_read(&rsource->rioc->rdmain);
-    } else {
-        rdma = qatomic_rcu_read(&rsource->rioc->rdmaout);
-    }
-
-    if (!rdma) {
-        error_report("RDMAContext is NULL when prepare Gsource");
-        return FALSE;
-    }
-
-    if (rdma->wr_data[0].control_len) {
-        cond |= G_IO_IN;
-    }
-    cond |= G_IO_OUT;
-
-    return cond & rsource->condition;
+    return TRUE;
 }
 
 static gboolean
 qio_channel_rdma_source_check(GSource *source)
 {
-    QIOChannelRDMASource *rsource = (QIOChannelRDMASource *)source;
-    RDMAContext *rdma;
-    GIOCondition cond = 0;
-
-    RCU_READ_LOCK_GUARD();
-    if (rsource->condition == G_IO_IN) {
-        rdma = qatomic_rcu_read(&rsource->rioc->rdmain);
-    } else {
-        rdma = qatomic_rcu_read(&rsource->rioc->rdmaout);
-    }
-
-    if (!rdma) {
-        error_report("RDMAContext is NULL when check Gsource");
-        return FALSE;
-    }
-
-    if (rdma->wr_data[0].control_len) {
-        cond |= G_IO_IN;
-    }
-    cond |= G_IO_OUT;
-
-    return cond & rsource->condition;
+    return TRUE;
 }
 
 static gboolean
@@ -2848,29 +2806,8 @@ qio_channel_rdma_source_dispatch(GSource *source,
 {
     QIOChannelFunc func = (QIOChannelFunc)callback;
     QIOChannelRDMASource *rsource = (QIOChannelRDMASource *)source;
-    RDMAContext *rdma;
-    GIOCondition cond = 0;
-
-    RCU_READ_LOCK_GUARD();
-    if (rsource->condition == G_IO_IN) {
-        rdma = qatomic_rcu_read(&rsource->rioc->rdmain);
-    } else {
-        rdma = qatomic_rcu_read(&rsource->rioc->rdmaout);
-    }
-
-    if (!rdma) {
-        error_report("RDMAContext is NULL when dispatch Gsource");
-        return FALSE;
-    }
-
-    if (rdma->wr_data[0].control_len) {
-        cond |= G_IO_IN;
-    }
-    cond |= G_IO_OUT;
 
-    return (*func)(QIO_CHANNEL(rsource->rioc),
-                   (cond & rsource->condition),
-                   user_data);
+    return (*func)(QIO_CHANNEL(rsource->rioc), rsource->condition, user_data);
 }
 
 static void
-- 
2.50.1