[dpdk-stable] patch 'kni: fix mbuf allocation for kernel side use' has been queued to stable release 19.11.10

[christian.ehrhardt@canonical.com]

Hi,

FYI, your patch has been queued to stable release 19.11.10

Note it hasn't been pushed to http://dpdk.org/browse/dpdk-stable yet.
It will be pushed if I get no objections before 08/12/21. So please
shout if anyone has objections.

Also note that after the patch there's a diff of the upstream commit vs the
patch applied to the branch. This will indicate if there was any rebasing
needed to apply to the stable branch. If there were code changes for rebasing
(ie: not only metadata diffs), please double check that the rebase was
correctly done.

Queued patches are on a temporary branch at:
https://github.com/cpaelzer/dpdk-stable-queue

This queued commit can be viewed at:
https://github.com/cpaelzer/dpdk-stable-queue/commit/4b9355f4d0fa3a07fc2f601fc826facec95a004f

Thanks.

Christian Ehrhardt <christian.ehrhardt@canonical.com>

---
From 4b9355f4d0fa3a07fc2f601fc826facec95a004f Mon Sep 17 00:00:00 2001
From: Yunjian Wang <wangyunjian@huawei.com>
Date: Tue, 22 Jun 2021 20:44:29 +0800
Subject: [PATCH] kni: fix mbuf allocation for kernel side use

[ upstream commit 0db3d5551abe94bb8a7030c1b90496b290ddb7f4 ]

In kni_allocate_mbufs(), we alloc mbuf for alloc_q as this code.
allocq_free = (kni->alloc_q->read - kni->alloc_q->write - 1) \
		& (MAX_MBUF_BURST_NUM - 1);
The value of allocq_free maybe zero, for example :
The ring size is 1024. After init, write = read = 0. Then we fill
kni->alloc_q to full. At this time, write = 1023, read = 0.

Then the kernel send 32 packets to userspace. At this time, write
= 1023, read = 32. And then the userspace receive this 32 packets.
Then fill the kni->alloc_q, (32 - 1023 - 1) & 31 = 0, fill nothing.
...
Then the kernel send 32 packets to userspace. At this time, write
= 1023, read = 992. And then the userspace receive this 32 packets.
Then fill the kni->alloc_q, (992 - 1023 - 1) & 31 = 0, fill nothing.

Then the kernel send 32 packets to userspace. The kni->alloc_q only
has 31 mbufs and will drop one packet.

Absolutely, this is a special scene. Normally, it will fill some
mbufs everytime, but may not enough for the kernel to use.

In this patch, we always keep the kni->alloc_q to full for the kernel
to use.

Fixes: 49da4e82cf94 ("kni: allocate no more mbuf than empty slots in queue")

Signed-off-by: Cheng Liu <liucheng11@huawei.com>
Signed-off-by: Yunjian Wang <wangyunjian@huawei.com>
Acked-by: Ferruh Yigit <ferruh.yigit@intel.com>
Acked-by: Ajit Khaparde <ajit.khaparde@broadcom.com>
---
 lib/librte_kni/rte_kni.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/lib/librte_kni/rte_kni.c b/lib/librte_kni/rte_kni.c
index bcf82cc2d5..e96adc14b5 100644
--- a/lib/librte_kni/rte_kni.c
+++ b/lib/librte_kni/rte_kni.c
@@ -674,8 +674,9 @@ kni_allocate_mbufs(struct rte_kni *kni)
 		return;
 	}
 
-	allocq_free = (kni->alloc_q->read - kni->alloc_q->write - 1)
-			& (MAX_MBUF_BURST_NUM - 1);
+	allocq_free = kni_fifo_free_count(kni->alloc_q);
+	allocq_free = (allocq_free > MAX_MBUF_BURST_NUM) ?
+		MAX_MBUF_BURST_NUM : allocq_free;
 	for (i = 0; i < allocq_free; i++) {
 		pkts[i] = rte_pktmbuf_alloc(kni->pktmbuf_pool);
 		if (unlikely(pkts[i] == NULL)) {
-- 
2.32.0

---
  Diff of the applied patch vs upstream commit (please double-check if non-empty:
---
--- -	2021-08-10 15:11:13.672319693 +0200
+++ 0015-kni-fix-mbuf-allocation-for-kernel-side-use.patch	2021-08-10 15:11:12.914637350 +0200
@@ -1 +1 @@
-From 0db3d5551abe94bb8a7030c1b90496b290ddb7f4 Mon Sep 17 00:00:00 2001
+From 4b9355f4d0fa3a07fc2f601fc826facec95a004f Mon Sep 17 00:00:00 2001
@@ -5,0 +6,2 @@
+[ upstream commit 0db3d5551abe94bb8a7030c1b90496b290ddb7f4 ]
+
@@ -31 +32,0 @@
-Cc: stable@dpdk.org
@@ -38 +39 @@
- lib/kni/rte_kni.c | 5 +++--
+ lib/librte_kni/rte_kni.c | 5 +++--
@@ -41,5 +42,5 @@
-diff --git a/lib/kni/rte_kni.c b/lib/kni/rte_kni.c
-index 9dae6a8d7c..eb24b0d0ae 100644
---- a/lib/kni/rte_kni.c
-+++ b/lib/kni/rte_kni.c
-@@ -677,8 +677,9 @@ kni_allocate_mbufs(struct rte_kni *kni)
+diff --git a/lib/librte_kni/rte_kni.c b/lib/librte_kni/rte_kni.c
+index bcf82cc2d5..e96adc14b5 100644
+--- a/lib/librte_kni/rte_kni.c
++++ b/lib/librte_kni/rte_kni.c
+@@ -674,8 +674,9 @@ kni_allocate_mbufs(struct rte_kni *kni)