From: =?UTF-8?q?Bj=C3=B6rn=20T=C3=B6pel?= <bjorn.topel@intel.com>
Date: Thu, 22 Mar 2018 16:14:33 +0100
Subject: i40e: tweak page counting for XDP_REDIRECT
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Patch-mainline: v4.17-rc1
Git-commit: 8ce29c679a6ecefb88dc794260f4e91a284eed9a
References: bsc#1111981 FATE#326312 FATE#326313
This commit tweaks the page counting for XDP_REDIRECT to function
properly. XDP_REDIRECT support will be added in a future commit.
The current page counting scheme assumes that the reference count
cannot decrease until the received frame is sent to the upper layers
of the networking stack. This assumption does not hold for the
XDP_REDIRECT action, since a page (pointed out by xdp_buff) can have
its reference count decreased via the xdp_do_redirect call.
To work around that, we now start off by a large page count and then
don't allow a refcount less than two.
Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
drivers/net/ethernet/intel/i40e/i40e_txrx.c | 9 ++++-----
1 file changed, 4 insertions(+), 5 deletions(-)
--- a/drivers/net/ethernet/intel/i40e/i40e_txrx.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
@@ -1587,9 +1587,8 @@ static bool i40e_alloc_mapped_page(struc
bi->dma = dma;
bi->page = page;
bi->page_offset = i40e_rx_offset(rx_ring);
-
- /* initialize pagecnt_bias to 1 representing we fully own page */
- bi->pagecnt_bias = 1;
+ page_ref_add(page, USHRT_MAX - 1);
+ bi->pagecnt_bias = USHRT_MAX;
return true;
}
@@ -1955,8 +1954,8 @@ static bool i40e_can_reuse_rx_page(struc
* the pagecnt_bias and page count so that we fully restock the
* number of references the driver holds.
*/
- if (unlikely(!pagecnt_bias)) {
- page_ref_add(page, USHRT_MAX);
+ if (unlikely(pagecnt_bias == 1)) {
+ page_ref_add(page, USHRT_MAX - 1);
rx_buffer->pagecnt_bias = USHRT_MAX;
}