diff mbox

[net-next,1/3] nfp: free buffers before changing MTU

Message ID 1451923395-24533-2-git-send-email-jakub.kicinski@netronome.com
State Changes Requested, archived
Delegated to: David Miller
Headers show

Commit Message

Jakub Kicinski Jan. 4, 2016, 4:03 p.m. UTC 
For freeing DMA buffers we depend on nfp_net.fl_bufsz having the same
value as during allocation therefore in .ndo_change_mtu we must first
free the buffers and then change the setting.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Rolf Neugebauer <rolf.neugebauer@netronome.com>
---
 drivers/net/ethernet/netronome/nfp/nfp_net_common.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

Comments

David Miller Jan. 5, 2016, 3:46 a.m. UTC | #1 
From: Jakub Kicinski <jakub.kicinski@netronome.com>
Date: Mon,  4 Jan 2016 16:03:13 +0000

> For freeing DMA buffers we depend on nfp_net.fl_bufsz having the same
> value as during allocation therefore in .ndo_change_mtu we must first
> free the buffers and then change the setting.
> 
> Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
> Reviewed-by: Rolf Neugebauer <rolf.neugebauer@netronome.com>

The behavior implemented by this patch is not acceptable.

If an error occurs reopenning the device after the MTU
change, the user is left with an inoperable interface and
zero feedback about what happened or why.

You MUST, therefore, specifically try to allocate the new memory and
resources that correspond to the new MTU value.

And if you can successfully allocate everything and be guarateed to
succeed, only then can you change the MTU and commit to the new
resources.

Otherwise you must leave the interface in exactly the state it was
in prior to the MTU change call and return an error to the caller.
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diff mbox

Patch

diff --git a/drivers/net/ethernet/netronome/nfp/nfp_net_common.c b/drivers/net/ethernet/netronome/nfp/nfp_net_common.c
index 43c618bafdb6..2826166547fd 100644
--- a/drivers/net/ethernet/netronome/nfp/nfp_net_common.c
+++ b/drivers/net/ethernet/netronome/nfp/nfp_net_common.c
@@ -1920,17 +1920,17 @@  static int nfp_net_change_mtu(struct net_device *netdev, int new_mtu)
 		return -EINVAL;
 	}
 
+	if (netif_running(netdev))
+		nfp_net_netdev_close(netdev);
+
 	netdev->mtu = new_mtu;
 
 	/* Freelist buffer size rounded up to the nearest 1K */
 	tmp = new_mtu + ETH_HLEN + VLAN_HLEN + NFP_NET_MAX_PREPEND;
 	nn->fl_bufsz = roundup(tmp, 1024);
 
-	/* restart if running */
-	if (netif_running(netdev)) {
-		nfp_net_netdev_close(netdev);
+	if (netif_running(netdev))
 		nfp_net_netdev_open(netdev);
-	}
 
 	return 0;
 }