2021-06-18 12:53:06

by Guangbin Huang

Subject: [PATCH net-next] net: hns3: fix reuse conflict of the rx page

From: Yunsheng Lin <[email protected]>

In the current rx page reuse handling process, the rx page buffer may
have conflict between driver and stack in high-pressure scenario.

To fix this problem, we need to check whether the page is only owned
by driver at the begin and at the end of a page to make sure there is
no reuse conflict between driver and stack when desc_cb->page_offset
is rollbacked to zero or increased.

Fixes: fa7711b888f2 ("net: hns3: optimize the rx page reuse handling process")
Signed-off-by: Yunsheng Lin <[email protected]>
Signed-off-by: Guangbin Huang <[email protected]>
---
drivers/net/ethernet/hisilicon/hns3/hns3_enet.c | 26 ++++++++++++++++++-------
1 file changed, 19 insertions(+), 7 deletions(-)

diff --git a/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c b/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c
index 51bbf5f760c5..cdb5f14fb6bc 100644
--- a/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c
+++ b/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c
@@ -3537,21 +3537,33 @@ static void hns3_nic_reuse_page(struct sk_buff *skb, int i,
int size = le16_to_cpu(desc->rx.size);
u32 truesize = hns3_buf_size(ring);
u32 frag_size = size - pull_len;
+ bool reused;

/* Avoid re-using remote or pfmem page */
if (unlikely(!dev_page_is_reusable(desc_cb->priv)))
goto out;

- /* Stack is not using and current page_offset is non-zero, we can
- * reuse from the zero offset.
+ reused = hns3_can_reuse_page(desc_cb);
+
+ /* Rx page can be reused when:
+ * 1. Rx page is only owned by the driver when page_offset
+ * is zero, which means 0 @ truesize will be used by
+ * stack after skb_add_rx_frag() is called, and the rest
+ * of rx page can be reused by driver.
+ * Or
+ * 2. Rx page is only owned by the driver when page_offset
+ * is non-zero, which means page_offset @ truesize will
+ * be used by stack after skb_add_rx_frag() is called,
+ * and 0 @ truesize can be reused by driver.
*/
- if (desc_cb->page_offset && hns3_can_reuse_page(desc_cb)) {
- desc_cb->page_offset = 0;
- desc_cb->reuse_flag = 1;
- } else if (desc_cb->page_offset + truesize * 2 <=
- hns3_page_size(ring)) {
+ if ((!desc_cb->page_offset && reused) ||
+ ((desc_cb->page_offset + truesize + truesize) <=
+ hns3_page_size(ring) && desc_cb->page_offset)) {
desc_cb->page_offset += truesize;
desc_cb->reuse_flag = 1;
+ } else if (desc_cb->page_offset && reused) {
+ desc_cb->page_offset = 0;
+ desc_cb->reuse_flag = 1;
} else if (frag_size <= ring->rx_copybreak) {
void *frag = napi_alloc_frag(frag_size);

--
2.8.1

2021-06-18 19:59:14

by patchwork-bot+netdevbpf

Subject: Re: [PATCH net-next] net: hns3: fix reuse conflict of the rx page

Hello:

This patch was applied to netdev/net-next.git (refs/heads/master):

On Fri, 18 Jun 2021 20:09:45 +0800 you wrote:
> From: Yunsheng Lin <[email protected]>
>
> In the current rx page reuse handling process, the rx page buffer may
> have conflict between driver and stack in high-pressure scenario.
>
> To fix this problem, we need to check whether the page is only owned
> by driver at the begin and at the end of a page to make sure there is
> no reuse conflict between driver and stack when desc_cb->page_offset
> is rollbacked to zero or increased.
>
> [...]

Here is the summary with links:
- [net-next] net: hns3: fix reuse conflict of the rx page
https://git.kernel.org/netdev/net-next/c/961045004b77

You are awesome, thank you!
--
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