On Mon, Jan 8, 2024 at 1:06 AM Yunsheng Lin <[email protected]> wrote:
>
> On 2024/1/6 0:06, Alexander H Duyck wrote:
> >>
> >> static void handle_tx_copy(struct vhost_net *net, struct socket *sock)
> >> @@ -1353,8 +1318,7 @@ static int vhost_net_open(struct inode *inode, struct file *f)
> >> vqs[VHOST_NET_VQ_RX]);
> >>
> >> f->private_data = n;
> >> - n->page_frag.page = NULL;
> >> - n->refcnt_bias = 0;
> >> + n->pf_cache.va = NULL;
> >>
> >> return 0;
> >> }
> >> @@ -1422,8 +1386,9 @@ static int vhost_net_release(struct inode *inode, struct file *f)
> >> kfree(n->vqs[VHOST_NET_VQ_RX].rxq.queue);
> >> kfree(n->vqs[VHOST_NET_VQ_TX].xdp);
> >> kfree(n->dev.vqs);
> >> - if (n->page_frag.page)
> >> - __page_frag_cache_drain(n->page_frag.page, n->refcnt_bias);
> >> + if (n->pf_cache.va)
> >> + __page_frag_cache_drain(virt_to_head_page(n->pf_cache.va),
> >> + n->pf_cache.pagecnt_bias);
> >> kvfree(n);
> >> return 0;
> >> }
> >
> > I would recommend reordering this patch with patch 5. Then you could
> > remove the block that is setting "n->pf_cache.va = NULL" above and just
> > make use of page_frag_cache_drain in the lower block which would also
> > return the va to NULL.
>
> I am not sure if we can as there is no zeroing for 'struct vhost_net' in
> vhost_net_open().
>
> If we don't have "n->pf_cache.va = NULL", don't we use the uninitialized data
> when calling page_frag_alloc_align() for the first time?
I see. So kvmalloc is used instead of kvzalloc when allocating the
structure. That might be an opportunity to clean things up a bit by
making that change to reduce the risk of some piece of memory
initialization being missed.
That said, I still think reordering the two patches might be useful as
it would help to make it so that the change you make to vhost_net is
encapsulated in one patch to fully enable the use of the new page pool
API.