linux-kernel - Re: [PATCH NET 1/7] skbuff: introduce pskb_realloc

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Message-ID: <20210712105310.46d265a5@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Mon, 12 Jul 2021 10:53:10 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Vasily Averin <vvs@...tuozzo.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        David Ahern <dsahern@...nel.org>,
        Eric Dumazet <eric.dumazet@...il.com>, netdev@...r.kernel.org,
        Joerg Reuter <jreuter@...na.de>,
        Ralf Baechle <ralf@...ux-mips.org>, linux-hams@...r.kernel.org,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        KP Singh <kpsingh@...nel.org>, bpf@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH NET 1/7] skbuff: introduce pskb_realloc_headroom()

On Mon, 12 Jul 2021 16:26:44 +0300 Vasily Averin wrote:
>  /**
> + *	pskb_realloc_headroom - reallocate header of &sk_buff
> + *	@skb: buffer to reallocate
> + *	@headroom: needed headroom
> + *
> + *	Unlike skb_realloc_headroom, this one does not allocate a new skb
> + *	if possible; copies skb->sk to new skb as needed
> + *	and frees original scb in case of failures.
> + *
> + *	It expect increased headroom, and generates warning otherwise.
> + */
> +
> +struct sk_buff *pskb_realloc_headroom(struct sk_buff *skb, unsigned int headroom)

I saw you asked about naming in a different sub-thread, what do you
mean by "'pskb_expand_head' have different semantic"? AFAIU the 'p'
in pskb stands for "private", meaning not shared. In fact
skb_realloc_headroom() should really be pskb... but it predates the 
'pskb' naming pattern by quite a while. Long story short
skb_expand_head() seems like a good name. With the current patch
pskb_realloc_headroom() vs skb_realloc_headroom() would give people
exactly the opposite intuition of what the code does.