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Message-ID: <73971895-6fa7-a5e1-542d-3faccbc4a830@kernel.org>
Date: Sun, 16 Jul 2023 16:57:07 -0700
From: Andy Lutomirski <luto@...nel.org>
To: Mina Almasry <almasrymina@...gle.com>,
linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
dri-devel@...ts.freedesktop.org, linaro-mm-sig@...ts.linaro.org,
netdev@...r.kernel.org, linux-arch@...r.kernel.org,
linux-kselftest@...r.kernel.org
Cc: Sumit Semwal <sumit.semwal@...aro.org>,
Christian König <christian.koenig@....com>,
"David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>,
Jesper Dangaard Brouer <hawk@...nel.org>,
Ilias Apalodimas <ilias.apalodimas@...aro.org>,
Arnd Bergmann <arnd@...db.de>,
David Ahern <dsahern@...nel.org>,
Willem de Bruijn <willemdebruijn.kernel@...il.com>,
Shuah Khan <shuah@...nel.org>, jgg@...pe.ca
Subject: Re: [RFC PATCH 06/10] net: add SO_DEVMEM_DONTNEED setsockopt to
release RX pages
On 7/10/23 15:32, Mina Almasry wrote:
> Add an interface for the user to notify the kernel that it is done reading
> the NET_RX dmabuf pages returned as cmsg. The kernel will drop the
> reference on the NET_RX pages to make them available for re-use.
>
> Signed-off-by: Mina Almasry <almasrymina@...gle.com>
> ---
> + for (i = 0; i < num_tokens; i++) {
> + for (j = 0; j < tokens[i].token_count; j++) {
> + struct page *pg = xa_erase(&sk->sk_pagepool,
> + tokens[i].token_start + j);
> +
> + if (pg)
> + put_page(pg);
> + else
> + /* -EINTR here notifies the userspace
> + * that not all tokens passed to it have
> + * been freed.
> + */
> + ret = -EINTR;
Unless I'm missing something, this type of error reporting is
unrecoverable -- userspace doesn't know how many tokens have been freed.
I think you should either make it explicitly unrecoverable (somehow shut
down dmabuf handling entirely) or tell userspace how many tokens were
successfully freed.
--Andy
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