vhost: use bvec_kmap_local in {get,put}u16_iotlb

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@lst.de>

diff --git a/drivers/vhost/vringh.c b/drivers/vhost/vringh.c
index 4af8fa259d65f83ccda6fa2104807f685d075599..cd529fbf83f62dbf0d08e637a599eb2bdba09ddf 100644 (file)
--- 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_loal(kaddr);
 
        return 0;
 }