Huang, Shaoqin
2022-Oct-22 12:31 UTC
[PATCH 2/2] virtio_ring: use helper function is_power_of_2()
On 10/21/2022 4:53 PM, Philippe Mathieu-Daud? wrote:> On 21/10/22 08:27, shaoqin.huang at intel.com wrote: >> From: Shaoqin Huang <shaoqin.huang at intel.com> >> >> Use helper function is_power_of_2() to check if num is power of two. >> Minor readability improvement. >> >> Signed-off-by: Shaoqin Huang <shaoqin.huang at intel.com> >> --- >> ? drivers/virtio/virtio_ring.c | 2 +- >> ? 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c >> index 2e7689bb933b..723c4e29e1d3 100644 >> --- a/drivers/virtio/virtio_ring.c >> +++ b/drivers/virtio/virtio_ring.c >> @@ -1052,7 +1052,7 @@ static int vring_alloc_queue_split(struct >> vring_virtqueue_split *vring_split, >> ????? dma_addr_t dma_addr; >> ????? /* We assume num is a power of 2. */ >> -??? if (num & (num - 1)) { >> +??? if (!is_power_of_2(num)) { >> ????????? dev_warn(&vdev->dev, "Bad virtqueue length %u\n", num); >> ????????? return -EINVAL; >> ????? } > > This makes the following code unreachable: > > ????if (!num) > ??????? return -ENOMEM; > > Do we want to move it earlier or remove it? >I think the following code can still be executed if num > 0, and if there if no enough memory, the allocation of the vring will failed and will decrease the num by divide 2, this will makes num equal to 0. And then trigger the check and return -ENOMEM.> Regards, > > Phil.