linux-kernel - Re: [PATCH v1 21/29] virtio-mem: memory notifier callbacks are specific to Sub Block Mode (SBM)

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Date:   Mon, 19 Oct 2020 12:22:43 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Wei Yang <richard.weiyang@...ux.alibaba.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        virtualization@...ts.linux-foundation.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Michael S . Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Pankaj Gupta <pankaj.gupta.linux@...il.com>
Subject: Re: [PATCH v1 21/29] virtio-mem: memory notifier callbacks are
 specific to Sub Block Mode (SBM)

On 19.10.20 03:57, Wei Yang wrote:
> On Mon, Oct 12, 2020 at 02:53:15PM +0200, David Hildenbrand wrote:
>> Let's rename accordingly.
>>
>> Cc: "Michael S. Tsirkin" <mst@...hat.com>
>> Cc: Jason Wang <jasowang@...hat.com>
>> Cc: Pankaj Gupta <pankaj.gupta.linux@...il.com>
>> Signed-off-by: David Hildenbrand <david@...hat.com>
>> ---
>> drivers/virtio/virtio_mem.c | 29 +++++++++++++++--------------
>> 1 file changed, 15 insertions(+), 14 deletions(-)
>>
>> diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c
>> index 3a772714fec9..d06c8760b337 100644
>> --- a/drivers/virtio/virtio_mem.c
>> +++ b/drivers/virtio/virtio_mem.c
>> @@ -589,8 +589,8 @@ static bool virtio_mem_contains_range(struct virtio_mem *vm, uint64_t start,
>> 	return start >= vm->addr && start + size <= vm->addr + vm->region_size;
>> }
>>
>> -static int virtio_mem_notify_going_online(struct virtio_mem *vm,
>> -					  unsigned long mb_id)
>> +static int virtio_mem_sbm_notify_going_online(struct virtio_mem *vm,
>> +					      unsigned long mb_id)
> 
> Look into this patch with "virtio-mem: Big Block Mode (BBM) memory hotplug"
> together, I thought the code is a little "complex".
> 
> The final logic of virtio_mem_memory_notifier_cb() looks like this:
> 
>     virtio_mem_memory_notifier_cb()
>         if (vm->in_sbm)
> 	    notify_xxx()
>         if (vm->in_sbm)
> 	    notify_xxx()
> 
> Can we adjust this like
> 
>     virtio_mem_memory_notifier_cb()
> 	notify_xxx()
>             if (vm->in_sbm)
>                 return
> 	notify_xxx()
>             if (vm->in_sbm)
>                 return
> 
> This style looks a little better to me.

Then we lose all the shared code after any of the mode-specific
handling? Like we have in MEM_OFFLINE, MEM_ONLINE, MEM_CANCEL_OFFLINE, ...

Don't think this will improve the situation.

-- 
Thanks,

David / dhildenb