[SRU][n:azure][PATCH 3/3] net: mana: Improve mana_set_channels() in low mem conditions

[Vinicius Peixoto]

From: Shradha Gupta <shradhagupta at linux.microsoft.com>

BugLink: https://bugs.launchpad.net/bugs/2086863

The mana_set_channels() function requires detaching the mana
driver and reattaching it with changed channel values.
During this operation if the system is low on memory, the reattach
might fail, causing the network device being down.
To avoid this we pre-allocate buffers at the beginning of set operation,
to prevent complete network loss

Signed-off-by: Shradha Gupta <shradhagupta at linux.microsoft.com>
Reviewed-by: Gerhard Engleder <gerhard at engleder-embedded.com>
Reviewed-by: Haiyang Zhang <haiyangz at microsoft.com>
Link: https://patch.msgid.link/1725248734-21760-1-git-send-email-shradhagupta@linux.microsoft.com
Signed-off-by: Jakub Kicinski <kuba at kernel.org>
(cherry picked from commit 1705341485ff1eec097dfa26891d03afe5907e16)
Signed-off-by: Vinicius Peixoto <vinicius.peixoto at canonical.com>
---
 drivers/net/ethernet/microsoft/mana/mana_en.c |  6 ++--
 .../ethernet/microsoft/mana/mana_ethtool.c    | 28 ++++++++++---------
 include/net/mana/mana.h                       |  2 +-
 3 files changed, 19 insertions(+), 17 deletions(-)

diff --git a/drivers/net/ethernet/microsoft/mana/mana_en.c b/drivers/net/ethernet/microsoft/mana/mana_en.c
index c8bcc37f1347..d28b315c8b6f 100644
--- a/drivers/net/ethernet/microsoft/mana/mana_en.c
+++ b/drivers/net/ethernet/microsoft/mana/mana_en.c
@@ -608,7 +608,7 @@ static void mana_get_rxbuf_cfg(int mtu, u32 *datasize, u32 *alloc_size,
 	*datasize = mtu + ETH_HLEN;
 }
 
-int mana_pre_alloc_rxbufs(struct mana_port_context *mpc, int new_mtu)
+int mana_pre_alloc_rxbufs(struct mana_port_context *mpc, int new_mtu, int num_queues)
 {
 	struct device *dev;
 	struct page *page;
@@ -622,7 +622,7 @@ int mana_pre_alloc_rxbufs(struct mana_port_context *mpc, int new_mtu)
 
 	dev = mpc->ac->gdma_dev->gdma_context->dev;
 
-	num_rxb = mpc->num_queues * mpc->rx_queue_size;
+	num_rxb = num_queues * mpc->rx_queue_size;
 
 	WARN(mpc->rxbufs_pre, "mana rxbufs_pre exists\n");
 	mpc->rxbufs_pre = kmalloc_array(num_rxb, sizeof(void *), GFP_KERNEL);
@@ -682,7 +682,7 @@ static int mana_change_mtu(struct net_device *ndev, int new_mtu)
 	int err;
 
 	/* Pre-allocate buffers to prevent failure in mana_attach later */
-	err = mana_pre_alloc_rxbufs(mpc, new_mtu);
+	err = mana_pre_alloc_rxbufs(mpc, new_mtu, mpc->num_queues);
 	if (err) {
 		netdev_err(ndev, "Insufficient memory for new MTU\n");
 		return err;
diff --git a/drivers/net/ethernet/microsoft/mana/mana_ethtool.c b/drivers/net/ethernet/microsoft/mana/mana_ethtool.c
index 5bee461b5e78..f23eb4a8deac 100644
--- a/drivers/net/ethernet/microsoft/mana/mana_ethtool.c
+++ b/drivers/net/ethernet/microsoft/mana/mana_ethtool.c
@@ -334,27 +334,29 @@ static int mana_set_channels(struct net_device *ndev,
 	struct mana_port_context *apc = netdev_priv(ndev);
 	unsigned int new_count = channels->combined_count;
 	unsigned int old_count = apc->num_queues;
-	int err, err2;
+	int err;
+
+	err = mana_pre_alloc_rxbufs(apc, ndev->mtu, new_count);
+	if (err) {
+		netdev_err(ndev, "Insufficient memory for new allocations");
+		return err;
+	}
 
 	err = mana_detach(ndev, false);
 	if (err) {
 		netdev_err(ndev, "mana_detach failed: %d\n", err);
-		return err;
+		goto out;
 	}
 
 	apc->num_queues = new_count;
 	err = mana_attach(ndev);
-	if (!err)
-		return 0;
-
-	netdev_err(ndev, "mana_attach failed: %d\n", err);
-
-	/* Try to roll it back to the old configuration. */
-	apc->num_queues = old_count;
-	err2 = mana_attach(ndev);
-	if (err2)
-		netdev_err(ndev, "mana re-attach failed: %d\n", err2);
+	if (err) {
+		apc->num_queues = old_count;
+		netdev_err(ndev, "mana_attach failed: %d\n", err);
+	}
 
+out:
+	mana_pre_dealloc_rxbufs(apc);
 	return err;
 }
 
@@ -403,7 +405,7 @@ static int mana_set_ringparam(struct net_device *ndev,
 
 	/* pre-allocating new buffers to prevent failures in mana_attach() later */
 	apc->rx_queue_size = new_rx;
-	err = mana_pre_alloc_rxbufs(apc, ndev->mtu);
+	err = mana_pre_alloc_rxbufs(apc, ndev->mtu, apc->num_queues);
 	apc->rx_queue_size = old_rx;
 	if (err) {
 		netdev_err(ndev, "Insufficient memory for new allocations\n");
diff --git a/include/net/mana/mana.h b/include/net/mana/mana.h
index 4eff4acb930a..b6324219876f 100644
--- a/include/net/mana/mana.h
+++ b/include/net/mana/mana.h
@@ -487,7 +487,7 @@ struct bpf_prog *mana_xdp_get(struct mana_port_context *apc);
 void mana_chn_setxdp(struct mana_port_context *apc, struct bpf_prog *prog);
 int mana_bpf(struct net_device *ndev, struct netdev_bpf *bpf);
 void mana_query_gf_stats(struct mana_port_context *apc);
-int mana_pre_alloc_rxbufs(struct mana_port_context *apc, int mtu);
+int mana_pre_alloc_rxbufs(struct mana_port_context *apc, int mtu, int num_queues);
 void mana_pre_dealloc_rxbufs(struct mana_port_context *apc);
 
 extern const struct ethtool_ops mana_ethtool_ops;
-- 
2.43.0