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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Dean Nelson <dnelson@redhat.com>,
        "David S. Miller" <davem@davemloft.net>
Subject: [PATCH 4.14 016/107] thunderx: enable page recycling for non-XDP case
Date:   Mon,  1 Apr 2019 19:01:31 +0200
Message-Id: <20190401170046.976692195@linuxfoundation.org>
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4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Dean Nelson <dnelson@redhat.com>

[ Upstream commit b3e208069477588c06f4d5d986164b435bb06e6d ]

Commit 773225388dae15e72790 ("net: thunderx: Optimize page recycling for XDP")
added code to nicvf_alloc_page() that inadvertently disables receive buffer
page recycling for the non-XDP case by always NULL'ng the page pointer.

This patch corrects two if-conditionals to allow for the recycling of non-XDP
mode pages by only setting the page pointer to NULL when the page is not ready
for recycling.

Fixes: 773225388dae ("net: thunderx: Optimize page recycling for XDP")
Signed-off-by: Dean Nelson <dnelson@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/net/ethernet/cavium/thunder/nicvf_queues.c |   23 ++++++++++-----------
 1 file changed, 11 insertions(+), 12 deletions(-)

--- a/drivers/net/ethernet/cavium/thunder/nicvf_queues.c
+++ b/drivers/net/ethernet/cavium/thunder/nicvf_queues.c
@@ -105,20 +105,19 @@ static inline struct pgcache *nicvf_allo
 	/* Check if page can be recycled */
 	if (page) {
 		ref_count = page_ref_count(page);
-		/* Check if this page has been used once i.e 'put_page'
-		 * called after packet transmission i.e internal ref_count
-		 * and page's ref_count are equal i.e page can be recycled.
+		/* This page can be recycled if internal ref_count and page's
+		 * ref_count are equal, indicating that the page has been used
+		 * once for packet transmission. For non-XDP mode, internal
+		 * ref_count is always '1'.
 		 */
-		if (rbdr->is_xdp && (ref_count == pgcache->ref_count))
-			pgcache->ref_count--;
-		else
-			page = NULL;
-
-		/* In non-XDP mode, page's ref_count needs to be '1' for it
-		 * to be recycled.
-		 */
-		if (!rbdr->is_xdp && (ref_count != 1))
+		if (rbdr->is_xdp) {
+			if (ref_count == pgcache->ref_count)
+				pgcache->ref_count--;
+			else
+				page = NULL;
+		} else if (ref_count != 1) {
 			page = NULL;
+		}
 	}
 
 	if (!page) {