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* [PATCH v2 1/2] i40e: tweak page counting for XDP_REDIRECT
@ 2018-03-22  9:03 ` =?unknown-8bit?q?Bj=C3=B6rn_T=C3=B6pel?=
  0 siblings, 0 replies; 10+ messages in thread
From: Björn Töpel @ 2018-03-22  9:03 UTC (permalink / raw)
  To: jeffrey.t.kirsher, intel-wired-lan
  Cc: Björn Töpel, magnus.karlsson, netdev,
	alexander.h.duyck, alexander.duyck

From: Björn Töpel <bjorn.topel@intel.com>

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>
---
 drivers/net/ethernet/intel/i40e/i40e_txrx.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/drivers/net/ethernet/intel/i40e/i40e_txrx.c b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
index e8eef9a56b6b..2f817d1466eb 100644
--- a/drivers/net/ethernet/intel/i40e/i40e_txrx.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
@@ -1588,9 +1588,8 @@ static bool i40e_alloc_mapped_page(struct i40e_ring *rx_ring,
 	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;
 }
@@ -1956,8 +1955,8 @@ static bool i40e_can_reuse_rx_page(struct i40e_rx_buffer *rx_buffer)
 	 * 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;
 	}
 
-- 
2.7.4

^ permalink raw reply related	[flat|nested] 10+ messages in thread

end of thread, other threads:[~2018-03-22 14:52 UTC | newest]

Thread overview: 10+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2018-03-22  9:03 [PATCH v2 1/2] i40e: tweak page counting for XDP_REDIRECT Björn Töpel
2018-03-22  9:03 ` [Intel-wired-lan] " =?unknown-8bit?q?Bj=C3=B6rn_T=C3=B6pel?=
2018-03-22  9:03 ` [PATCH v2 2/2] i40e: add support " Björn Töpel
2018-03-22  9:03   ` [Intel-wired-lan] " =?unknown-8bit?q?Bj=C3=B6rn_T=C3=B6pel?=
2018-03-22 11:58   ` Jesper Dangaard Brouer
2018-03-22 11:58     ` [Intel-wired-lan] " Jesper Dangaard Brouer
2018-03-22 12:20     ` Björn Töpel
2018-03-22 12:20       ` [Intel-wired-lan] " =?unknown-8bit?q?Bj=C3=B6rn_T=C3=B6pel?=
2018-03-22 14:52       ` Alexander Duyck
2018-03-22 14:52         ` [Intel-wired-lan] " Alexander Duyck

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