On Tue, Feb 22, 2022 at 11:49 PM Christoph Hellwig <hch@xxxxxx> wrote:
>
> Using local kmaps slightly reduces the chances to stray writes, and
> the bvec interface cleans up the code a little bit.
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Acked-by: Jason Wang <jasowang@xxxxxxxxxx>
> ---
> drivers/vhost/vringh.c | 18 ++++++++----------
> 1 file changed, 8 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/vhost/vringh.c b/drivers/vhost/vringh.c
> index 14e2043d76852..0f22a83fd09af 100644
> --- a/drivers/vhost/vringh.c
> +++ b/drivers/vhost/vringh.c
> @@ -1173,7 +1173,7 @@ static inline int getu16_iotlb(const struct vringh *vrh,
> u16 *val, const __virtio16 *p)
> {
> struct bio_vec iov;
> - void *kaddr, *from;
> + void *kaddr;
> int ret;
>
> /* Atomic read is needed for getu16 */
> @@ -1182,10 +1182,9 @@ static inline int getu16_iotlb(const struct vringh *vrh,
> if (ret < 0)
> return ret;
>
> - kaddr = kmap_atomic(iov.bv_page);
> - from = kaddr + iov.bv_offset;
> - *val = vringh16_to_cpu(vrh, READ_ONCE(*(__virtio16 *)from));
> - kunmap_atomic(kaddr);
> + kaddr = bvec_kmap_local(&iov);
> + *val = vringh16_to_cpu(vrh, READ_ONCE(*(__virtio16 *)kaddr));
> + kunmap_local(kaddr);
>
> return 0;
> }
> @@ -1194,7 +1193,7 @@ static inline int putu16_iotlb(const struct vringh *vrh,
> __virtio16 *p, u16 val)
> {
> struct bio_vec iov;
> - void *kaddr, *to;
> + void *kaddr;
> int ret;
>
> /* Atomic write is needed for putu16 */
> @@ -1203,10 +1202,9 @@ static inline int putu16_iotlb(const struct vringh *vrh,
> if (ret < 0)
> return ret;
>
> - kaddr = kmap_atomic(iov.bv_page);
> - to = kaddr + iov.bv_offset;
> - WRITE_ONCE(*(__virtio16 *)to, cpu_to_vringh16(vrh, val));
> - kunmap_atomic(kaddr);
> + kaddr = bvec_kmap_local(&iov);
> + WRITE_ONCE(*(__virtio16 *)kaddr, cpu_to_vringh16(vrh, val));
> + kunmap_local(kaddr);
>
> return 0;
> }
> --
> 2.30.2
>
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