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vhost: switch to use vhost_add_used_n() 

Let vhost_add_used() to use vhost_add_used_n() to reduce the code
duplication. To avoid the overhead brought by __copy_to_user(). We will use
put_user() when one used need to be added.

Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Jason Wang 2013-09-02 16:40:58 +08:00 committed by David S. Miller
parent c92112aed3
commit c49e4e573b
1 changed files with 12 additions and 42 deletions
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54
drivers/vhost/vhost.c
View File

@ -1332,48 +1332,9 @@ EXPORT_SYMBOL_GPL(vhost_discard_vq_desc);
* want to notify the guest, using eventfd. */
int vhost_add_used(struct vhost_virtqueue *vq, unsigned int head, int len)
{
struct vring_used_elem __user *used;
struct vring_used_elem heads = { head, len };
/* The virtqueue contains a ring of used buffers. Get a pointer to the
* next entry in that used ring. */
used = &vq->used->ring[vq->last_used_idx % vq->num];
if (__put_user(head, &used->id)) {
vq_err(vq, "Failed to write used id");
return -EFAULT;
}
if (__put_user(len, &used->len)) {
vq_err(vq, "Failed to write used len");
return -EFAULT;
}
/* Make sure buffer is written before we update index. */
smp_wmb();
if (__put_user(vq->last_used_idx + 1, &vq->used->idx)) {
vq_err(vq, "Failed to increment used idx");
return -EFAULT;
}
if (unlikely(vq->log_used)) {
/* Make sure data is seen before log. */
smp_wmb();
/* Log used ring entry write. */
log_write(vq->log_base,
vq->log_addr +
((void __user *)used - (void __user *)vq->used),
sizeof *used);
/* Log used index update. */
log_write(vq->log_base,
vq->log_addr + offsetof(struct vring_used, idx),
sizeof vq->used->idx);
if (vq->log_ctx)
eventfd_signal(vq->log_ctx, 1);
}
vq->last_used_idx++;
/* If the driver never bothers to signal in a very long while,
* used index might wrap around. If that happens, invalidate
* signalled_used index we stored. TODO: make sure driver
* signals at least once in 2^16 and remove this. */
if (unlikely(vq->last_used_idx == vq->signalled_used))
vq->signalled_used_valid = false;
return 0;
return vhost_add_used_n(vq, &heads, 1);
}
EXPORT_SYMBOL_GPL(vhost_add_used);
@ -1387,7 +1348,16 @@ static int __vhost_add_used_n(struct vhost_virtqueue *vq,
start = vq->last_used_idx % vq->num;
used = vq->used->ring + start;
if (__copy_to_user(used, heads, count * sizeof *used)) {
if (count == 1) {
if (__put_user(heads[0].id, &used->id)) {
vq_err(vq, "Failed to write used id");
return -EFAULT;
}
if (__put_user(heads[0].len, &used->len)) {
vq_err(vq, "Failed to write used len");
return -EFAULT;
}
} else if (__copy_to_user(used, heads, count * sizeof *used)) {
vq_err(vq, "Failed to write used");
return -EFAULT;
}