linux-kernel - [PATCH v2 02/29] virtio-mem: more precise calculation in virtio_mem_mb_state_prepare_next

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Message-Id: <20201112133815.13332-3-david@redhat.com>
Date:   Thu, 12 Nov 2020 14:37:48 +0100
From:   David Hildenbrand <david@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     virtualization@...ts.linux-foundation.org, linux-mm@...ck.org,
        "Michael S . Tsirkin" <mst@...hat.com>,
        David Hildenbrand <david@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Pankaj Gupta <pankaj.gupta.linux@...il.com>
Subject: [PATCH v2 02/29] virtio-mem: more precise calculation in virtio_mem_mb_state_prepare_next_mb()

We actually need one byte less (next_mb_id is exclusive, first_mb_id is
inclusive). While at it, compact the code.

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 | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c
index a37fd73588da..dee46865bae2 100644
--- a/drivers/virtio/virtio_mem.c
+++ b/drivers/virtio/virtio_mem.c
@@ -257,10 +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;
-	int old_pages = PFN_UP(old_bytes);
-	int new_pages = PFN_UP(new_bytes);
+	int old_pages = PFN_UP(vm->next_mb_id - vm->first_mb_id);
+	int new_pages = PFN_UP(vm->next_mb_id - vm->first_mb_id + 1);
 	uint8_t *new_mb_state;
 
 	if (vm->mb_state && old_pages == new_pages)
-- 
2.26.2