linux-kernel - Re: [PATCH net-next v19 1/1] mctp pcc: Implement MCTP over PCC Transport

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Message-ID: <b254a359-0ca8-463b-b666-e34ba357bd09@amperemail.onmicrosoft.com>
Date: Wed, 23 Apr 2025 14:25:57 -0400
From: Adam Young <admiyo@...eremail.onmicrosoft.com>
To: Jeremy Kerr <jk@...econstruct.com.au>, admiyo@...amperecomputing.com,
 Matt Johnston <matt@...econstruct.com.au>,
 Andrew Lunn <andrew+netdev@...n.ch>, "David S. Miller"
 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
 Sudeep Holla <sudeep.holla@....com>,
 Jonathan Cameron <Jonathan.Cameron@...wei.com>,
 Huisong Li <lihuisong@...wei.com>
Subject: Re: [PATCH net-next v19 1/1] mctp pcc: Implement MCTP over PCC
 Transport

On 4/22/25 10:15, Jeremy Kerr wrote:
> > +       spin_lock_irqsave(&mpnd->lock, flags);
> > +       rc = skb_cow_head(skb, sizeof(struct mctp_pcc_hdr));
> > +       if (rc)
> > +               return rc;
> This will return with mpdn->lock still held.
> And should this return the raw rc value? Or NETDEV_TX_OK?

I based my code off the other drivers in the same directory:

         rc = skb_cow_head(skb, sizeof(struct mctp_i2c_hdr));
         if (rc)
                 return rc;

         rc = skb_cow_head(skb, sizeof(struct mctp_i3c_internal_hdr));
         if (rc)
                 return rc;

However, I just noticed the USB one, that went in last release, does 
this (using a goto)

err_drop:
         dev_dstats_tx_dropped(dev);
         kfree_skb(skb);
         return NETDEV_TX_OK;

Seems strange to returning NETDEV_TX_OK for what is essentially a memory 
allocation failure?  However, I am going to assume that this most recent 
one represents the current wisdom, and will follow suit.