On 28/08/2025 04:59, Peter Xu wrote:
> 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.
> 


First, RDMA migration works well with this patch applied.

Tested-by: Li Zhijian <[email protected]>


I have a small question. While testing, I didn't observe any callers to
qio_channel_rdma_create_watch() during a complete RDMA migration using
the default capabilities and parameters.
I was wondering in which case this function is expected to be called?
(I see io_create_watch() is mandatory for QIOChannelClass)


Thanks
Zhijian


> 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 <[email protected]>
> ---
>   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

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