netdev - Re: [PATCH] net: Revert tx queue length on partial failure in dev_qdisc_change_tx_queue

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Message-ID: <CAO9wTFiGCrAOkZSPr1N6W_8yacyUUcZanvXdQ-FQaphpnWe5DA@mail.gmail.com>
Date: Wed, 23 Jul 2025 23:47:09 +0530
From: Suchit K <suchitkarunakaran@...il.com>
To: Eric Dumazet <edumazet@...gle.com>
Cc: davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com, horms@...nel.org, 
	jhs@...atatu.com, xiyou.wangcong@...il.com, jiri@...nulli.us, sdf@...ichev.me, 
	kuniyu@...gle.com, aleksander.lobakin@...el.com, netdev@...r.kernel.org, 
	skhan@...uxfoundation.org, linux-kernel-mentees@...ts.linux.dev, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: Revert tx queue length on partial failure in dev_qdisc_change_tx_queue_len()

>
> WRITE_ONCE() is missing.
>
> > +               while (i >= 0) {
> > +                       qdisc_change_tx_queue_len(dev, &dev->_tx[i]);
>
> What happens if one of these calls fails ?
>
> I think a fix will be more complicated...

Hi Eric,
Given that pfifo_fast_change_tx_queue_len is currently the only
implementation of change_tx_queue_len, would it be reasonable to
handle partial failures solely within pfifo_fast_change_tx_queue_len
(which in turn leads to skb_array_resize_multiple_bh)? In other words,
is it sufficient to modify only the underlying low level
implementation of pfifo_fast_change_tx_queue_len for partial failures,
given that it's the sole implementation of change_tx_queue_len?