linux-kernel - Re: [PATCH v1 02/29] virtio-mem: simplify calculation in virtio_mem_mb_state_prepare_next

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Message-ID: <09e63b8a-fb46-c8ae-7512-84b1dd234075@redhat.com>
Date:   Fri, 16 Oct 2020 11:00:17 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Pankaj Gupta <pankaj.gupta.linux@...il.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, Linux MM <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>
Subject: Re: [PATCH v1 02/29] virtio-mem: simplify calculation in
 virtio_mem_mb_state_prepare_next_mb()

On 15.10.20 22:24, Pankaj Gupta wrote:
>> We actually need one byte less (next_mb_id is exclusive, first_mb_id is
>> inclusive). Simplify.
>>
>> 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 | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c
>> index a1f5bf7a571a..670b3faf412d 100644
>> --- a/drivers/virtio/virtio_mem.c
>> +++ b/drivers/virtio/virtio_mem.c
>> @@ -257,8 +257,8 @@ static enum virtio_mem_mb_state virtio_mem_mb_get_state(struct virtio_mem *vm,
>>   */
>>  static int virtio_mem_mb_state_prepare_next_mb(struct virtio_mem *vm)
>>  {
>> -       unsigned long old_bytes = vm->next_mb_id - vm->first_mb_id + 1;
>> -       unsigned long new_bytes = vm->next_mb_id - vm->first_mb_id + 2;
>> +       unsigned long old_bytes = vm->next_mb_id - vm->first_mb_id;
>> +       unsigned long new_bytes = old_bytes + 1;
> 
> Maybe we can avoid new_bytes & old_bytes variables, instead use single
> variable. Can later be used with PFN_UP/PFN_DOWN.

I'll see if it fits into a single line now - if it does, I'll move it
there. Thanks!

-- 
Thanks,

David / dhildenb