linux-kernel - Re: [PATCH net-next v6 4/4] eventpoll: Add epoll ioctl for epoll

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Date: Wed, 7 Feb 2024 10:50:15 -0800
From: Joe Damato <jdamato@...tly.com>
To: kuba@...nel.org, netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	chuck.lever@...cle.com, jlayton@...nel.org,
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	amritha.nambiar@...el.com, Jonathan Corbet <corbet@....net>,
	Alexander Viro <viro@...iv.linux.org.uk>, Jan Kara <jack@...e.cz>,
	Nathan Lynch <nathanl@...ux.ibm.com>,
	Michael Ellerman <mpe@...erman.id.au>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Namjae Jeon <linkinjeon@...nel.org>,
	Steve French <stfrench@...rosoft.com>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	Julien Panis <jpanis@...libre.com>,
	Andrew Waterman <waterman@...s.berkeley.edu>,
	Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>,
	"open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
	"open list:FILESYSTEMS (VFS and infrastructure)" <linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH net-next v6 4/4] eventpoll: Add epoll ioctl for
 epoll_params

On Wed, Feb 07, 2024 at 09:37:14AM +0100, Jiri Slaby wrote:
> On 05. 02. 24, 22:04, Joe Damato wrote:
> >Add an ioctl for getting and setting epoll_params. User programs can use
> >this ioctl to get and set the busy poll usec time, packet budget, and
> >prefer busy poll params for a specific epoll context.
> >
> >Parameters are limited:
> >   - busy_poll_usecs is limited to <= u32_max
> >   - busy_poll_budget is limited to <= NAPI_POLL_WEIGHT by unprivileged
> >     users (!capable(CAP_NET_ADMIN))
> >   - prefer_busy_poll must be 0 or 1
> >   - __pad must be 0
> >
> >Signed-off-by: Joe Damato <jdamato@...tly.com>
> ...
> >--- a/fs/eventpoll.c
> >+++ b/fs/eventpoll.c
> ...
> >@@ -497,6 +498,50 @@ static inline void ep_set_busy_poll_napi_id(struct epitem *epi)
> >  	ep->napi_id = napi_id;
> >  }
> >+static long ep_eventpoll_bp_ioctl(struct file *file, unsigned int cmd,
> >+				  unsigned long arg)
> >+{
> >+	struct eventpoll *ep;
> >+	struct epoll_params epoll_params;
> >+	void __user *uarg = (void __user *) arg;
> >+
> >+	ep = file->private_data;
> 
> This might have been on the ep declaration line.
> 
> >+	switch (cmd) {
> >+	case EPIOCSPARAMS:
> >+		if (copy_from_user(&epoll_params, uarg, sizeof(epoll_params)))
> >+			return -EFAULT;
> >+
> >+		if (memchr_inv(epoll_params.__pad, 0, sizeof(epoll_params.__pad)))
> >+			return -EINVAL;
> >+
> >+		if (epoll_params.busy_poll_usecs > U32_MAX)
> >+			return -EINVAL;
> >+
> >+		if (epoll_params.prefer_busy_poll > 1)
> >+			return -EINVAL;
> >+
> >+		if (epoll_params.busy_poll_budget > NAPI_POLL_WEIGHT &&
> >+		    !capable(CAP_NET_ADMIN))
> >+			return -EPERM;
> >+
> >+		ep->busy_poll_usecs = epoll_params.busy_poll_usecs;
> >+		ep->busy_poll_budget = epoll_params.busy_poll_budget;
> >+		ep->prefer_busy_poll = !!epoll_params.prefer_busy_poll;
> 
> This !! is unnecessary. Nonzero values shall be "converted" to true.
> 
> But FWIW, the above is nothing which should be blocking, so:
"> 
> Reviewed-by: Jiri Slaby <jirislaby@...nel.org>

netdev maintainers: Jiri marked this with Reviewed-by, but was this review
what caused "Changes Requested" to be the status set for this patch set in
patchwork?

If needed, I'll send a v7 with the changes Jiri suggested and add the
"Reviewed-by" since the changes are cosmetic, but I wanted to make sure
this was the reason.

Thanks.