On Mon, Jan 8, 2024 at 1:06 AM Yunsheng Lin <linyunsheng@xxxxxxxxxx> 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.
