diff mbox series

[net-next,v2,3/4] eventpoll: Add epoll ioctl for epoll_params

Message ID 20240125003014.43103-4-jdamato@fastly.com
State New
Headers
Series Per epoll context busy poll support |

Commit Message

Joe Damato Jan. 25, 2024, 12:30 a.m. UTC 
  Add an ioctl for getting and setting epoll_params. User programs can use
this ioctl to get and set the busy poll usec time or packet budget
params for a specific epoll context.

Signed-off-by: Joe Damato <jdamato@fastly.com>
---
 .../userspace-api/ioctl/ioctl-number.rst      |  1 +
 fs/eventpoll.c                                | 47 +++++++++++++++++++
 include/uapi/linux/eventpoll.h                | 12 +++++
 3 files changed, 60 insertions(+)

Comments

Willem de Bruijn Jan. 25, 2024, 2:46 a.m. UTC | #1 
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 or packet budget
> params for a specific epoll context.
> 
> Signed-off-by: Joe Damato <jdamato@fastly.com>

Please be sure to include the lists and people suggested by
`get_maintainer.pl -f fs/eventpoll.c`.

Adding ioctls is generally discouraged.

As this affects the behavior of epoll_wait, should this just be a
flag to (a new variant of) epoll_wait?

Speaking from some experience with adding epoll_pwait2. I initially
there added a stateful change that would affect wait behavior. The
sensible feedback as the time was to just change the behavior of the
syscall it affected. Even if that requires a syscall (which is not
that different from an ioctl, if better defined).

The discussion in that thread may be informative to decide on API:
https://lwn.net/ml/linux-kernel/20201116161001.1606608-1-willemdebruijn.kernel@gmail.com/

Agreed on the overall principle that it is preferable to be able to
enable busypolling selectively. We already do for SO_BUSY_POLL and
sysctl busy_read.

> ---
>  .../userspace-api/ioctl/ioctl-number.rst      |  1 +
>  fs/eventpoll.c                                | 47 +++++++++++++++++++
>  include/uapi/linux/eventpoll.h                | 12 +++++
>  3 files changed, 60 insertions(+)
> 
> diff --git a/Documentation/userspace-api/ioctl/ioctl-number.rst b/Documentation/userspace-api/ioctl/ioctl-number.rst
> index 457e16f06e04..b33918232f78 100644
> --- a/Documentation/userspace-api/ioctl/ioctl-number.rst
> +++ b/Documentation/userspace-api/ioctl/ioctl-number.rst
> @@ -309,6 +309,7 @@ Code  Seq#    Include File                                           Comments
>  0x89  0B-DF  linux/sockios.h
>  0x89  E0-EF  linux/sockios.h                                         SIOCPROTOPRIVATE range
>  0x89  F0-FF  linux/sockios.h                                         SIOCDEVPRIVATE range
> +0x8A  00-1F  linux/eventpoll.h
>  0x8B  all    linux/wireless.h
>  0x8C  00-3F                                                          WiNRADiO driver
>                                                                       <http://www.winradio.com.au/>
> diff --git a/fs/eventpoll.c b/fs/eventpoll.c
> index 40bd97477b91..c1ee0fe01da1 100644
> --- a/fs/eventpoll.c
> +++ b/fs/eventpoll.c
> @@ -6,6 +6,8 @@
>   *  Davide Libenzi <davidel@xmailserver.org>
>   */
>  
> +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
> +
>  #include <linux/init.h>
>  #include <linux/kernel.h>
>  #include <linux/sched/signal.h>
> @@ -869,6 +871,49 @@ static void ep_clear_and_put(struct eventpoll *ep)
>  		ep_free(ep);
>  }
>  
> +static long ep_eventpoll_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
> +{
> +	int ret;
> +	struct eventpoll *ep;
> +	struct epoll_params epoll_params;
> +	void __user *uarg = (void __user *) arg;
> +
> +	if (!is_file_epoll(file))
> +		return -EINVAL;
> +
> +	ep = file->private_data;
> +
> +	switch (cmd) {
> +#ifdef CONFIG_NET_RX_BUSY_POLL
> +	case EPIOCSPARAMS:
> +		if (copy_from_user(&epoll_params, uarg, sizeof(epoll_params)))
> +			return -EFAULT;
> +
> +		if (epoll_params.busy_poll_budget > NAPI_POLL_WEIGHT)
> +			pr_err("busy poll budget %u exceeds suggested maximum %u\n",
> +					epoll_params.busy_poll_budget, NAPI_POLL_WEIGHT);
> +
> +		ep->busy_poll_usecs = epoll_params.busy_poll_usecs;
> +		ep->busy_poll_budget = epoll_params.busy_poll_budget;
> +		return 0;
> +
> +	case EPIOCGPARAMS:
> +		memset(&epoll_params, 0, sizeof(epoll_params));
> +		epoll_params.busy_poll_usecs = ep->busy_poll_usecs;
> +		epoll_params.busy_poll_budget = ep->busy_poll_budget;
> +		if (copy_to_user(uarg, &epoll_params, sizeof(epoll_params)))
> +			return -EFAULT;
> +
> +		return 0;
> +#endif
> +	default:
> +		ret = -EINVAL;
> +		break;
> +	}
> +
> +	return ret;
> +}
> +
>  static int ep_eventpoll_release(struct inode *inode, struct file *file)
>  {
>  	struct eventpoll *ep = file->private_data;
> @@ -975,6 +1020,8 @@ static const struct file_operations eventpoll_fops = {
>  	.release	= ep_eventpoll_release,
>  	.poll		= ep_eventpoll_poll,
>  	.llseek		= noop_llseek,
> +	.unlocked_ioctl	= ep_eventpoll_ioctl,
> +	.compat_ioctl   = compat_ptr_ioctl,
>  };
>  
>  /*
> diff --git a/include/uapi/linux/eventpoll.h b/include/uapi/linux/eventpoll.h
> index cfbcc4cc49ac..8eb0fdbce995 100644
> --- a/include/uapi/linux/eventpoll.h
> +++ b/include/uapi/linux/eventpoll.h
> @@ -85,4 +85,16 @@ struct epoll_event {
>  	__u64 data;
>  } EPOLL_PACKED;
>  
> +struct epoll_params {
> +	u64 busy_poll_usecs;
> +	u16 busy_poll_budget;
> +
> +	/* for future fields */
> +	u8 data[118];
> +} EPOLL_PACKED;
> +
> +#define EPOLL_IOC_TYPE 0x8A
> +#define EPIOCSPARAMS _IOW(EPOLL_IOC_TYPE, 0x01, struct epoll_params)
> +#define EPIOCGPARAMS _IOR(EPOLL_IOC_TYPE, 0x02, struct epoll_params)
> +
>  #endif /* _UAPI_LINUX_EVENTPOLL_H */
> -- 
> 2.25.1
>
Joe Damato Jan. 25, 2024, 4:27 a.m. UTC | #2 
On Wed, Jan 24, 2024 at 09:46:23PM -0500, Willem de Bruijn wrote:
> 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 or packet budget
> > params for a specific epoll context.
> > 
> > Signed-off-by: Joe Damato <jdamato@fastly.com>
> 
> Please be sure to include the lists and people suggested by
> `get_maintainer.pl -f fs/eventpoll.c`.

Thanks - I must have done something wrong when trying to get the maintainer
list.

Should I resend this v2? Not sure what the appropriate thing to do is in
this case. My apologies.

> Adding ioctls is generally discouraged.
> 
> As this affects the behavior of epoll_wait, should this just be a
> flag to (a new variant of) epoll_wait?

I have no strong preference either way. It seems to me that adding a new
system call is a fairly significant change vs adding an ioctl, but I am
open to whatever is preferred by the maintainers.

I have no idea who would need to weigh-in to make this decision.

> Speaking from some experience with adding epoll_pwait2. I initially
> there added a stateful change that would affect wait behavior. The
> sensible feedback as the time was to just change the behavior of the
> syscall it affected. Even if that requires a syscall (which is not
> that different from an ioctl, if better defined).
> 
> The discussion in that thread may be informative to decide on API:
> https://lwn.net/ml/linux-kernel/20201116161001.1606608-1-willemdebruijn.kernel@gmail.com/

Interesting thread, thanks for sending.

> Agreed on the overall principle that it is preferable to be able to
> enable busypolling selectively. We already do for SO_BUSY_POLL and
> sysctl busy_read.

Thanks for taking a look and providing feedback.

>
> > ---
> >  .../userspace-api/ioctl/ioctl-number.rst      |  1 +
> >  fs/eventpoll.c                                | 47 +++++++++++++++++++
> >  include/uapi/linux/eventpoll.h                | 12 +++++
> >  3 files changed, 60 insertions(+)
> > 
> > diff --git a/Documentation/userspace-api/ioctl/ioctl-number.rst b/Documentation/userspace-api/ioctl/ioctl-number.rst
> > index 457e16f06e04..b33918232f78 100644
> > --- a/Documentation/userspace-api/ioctl/ioctl-number.rst
> > +++ b/Documentation/userspace-api/ioctl/ioctl-number.rst
> > @@ -309,6 +309,7 @@ Code  Seq#    Include File                                           Comments
> >  0x89  0B-DF  linux/sockios.h
> >  0x89  E0-EF  linux/sockios.h                                         SIOCPROTOPRIVATE range
> >  0x89  F0-FF  linux/sockios.h                                         SIOCDEVPRIVATE range
> > +0x8A  00-1F  linux/eventpoll.h
> >  0x8B  all    linux/wireless.h
> >  0x8C  00-3F                                                          WiNRADiO driver
> >                                                                       <http://www.winradio.com.au/>
> > diff --git a/fs/eventpoll.c b/fs/eventpoll.c
> > index 40bd97477b91..c1ee0fe01da1 100644
> > --- a/fs/eventpoll.c
> > +++ b/fs/eventpoll.c
> > @@ -6,6 +6,8 @@
> >   *  Davide Libenzi <davidel@xmailserver.org>
> >   */
> >  
> > +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
> > +
> >  #include <linux/init.h>
> >  #include <linux/kernel.h>
> >  #include <linux/sched/signal.h>
> > @@ -869,6 +871,49 @@ static void ep_clear_and_put(struct eventpoll *ep)
> >  		ep_free(ep);
> >  }
> >  
> > +static long ep_eventpoll_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
> > +{
> > +	int ret;
> > +	struct eventpoll *ep;
> > +	struct epoll_params epoll_params;
> > +	void __user *uarg = (void __user *) arg;
> > +
> > +	if (!is_file_epoll(file))
> > +		return -EINVAL;
> > +
> > +	ep = file->private_data;
> > +
> > +	switch (cmd) {
> > +#ifdef CONFIG_NET_RX_BUSY_POLL
> > +	case EPIOCSPARAMS:
> > +		if (copy_from_user(&epoll_params, uarg, sizeof(epoll_params)))
> > +			return -EFAULT;
> > +
> > +		if (epoll_params.busy_poll_budget > NAPI_POLL_WEIGHT)
> > +			pr_err("busy poll budget %u exceeds suggested maximum %u\n",
> > +					epoll_params.busy_poll_budget, NAPI_POLL_WEIGHT);
> > +
> > +		ep->busy_poll_usecs = epoll_params.busy_poll_usecs;
> > +		ep->busy_poll_budget = epoll_params.busy_poll_budget;
> > +		return 0;
> > +
> > +	case EPIOCGPARAMS:
> > +		memset(&epoll_params, 0, sizeof(epoll_params));
> > +		epoll_params.busy_poll_usecs = ep->busy_poll_usecs;
> > +		epoll_params.busy_poll_budget = ep->busy_poll_budget;
> > +		if (copy_to_user(uarg, &epoll_params, sizeof(epoll_params)))
> > +			return -EFAULT;
> > +
> > +		return 0;
> > +#endif
> > +	default:
> > +		ret = -EINVAL;
> > +		break;
> > +	}
> > +
> > +	return ret;
> > +}
> > +
> >  static int ep_eventpoll_release(struct inode *inode, struct file *file)
> >  {
> >  	struct eventpoll *ep = file->private_data;
> > @@ -975,6 +1020,8 @@ static const struct file_operations eventpoll_fops = {
> >  	.release	= ep_eventpoll_release,
> >  	.poll		= ep_eventpoll_poll,
> >  	.llseek		= noop_llseek,
> > +	.unlocked_ioctl	= ep_eventpoll_ioctl,
> > +	.compat_ioctl   = compat_ptr_ioctl,
> >  };
> >  
> >  /*
> > diff --git a/include/uapi/linux/eventpoll.h b/include/uapi/linux/eventpoll.h
> > index cfbcc4cc49ac..8eb0fdbce995 100644
> > --- a/include/uapi/linux/eventpoll.h
> > +++ b/include/uapi/linux/eventpoll.h
> > @@ -85,4 +85,16 @@ struct epoll_event {
> >  	__u64 data;
> >  } EPOLL_PACKED;
> >  
> > +struct epoll_params {
> > +	u64 busy_poll_usecs;
> > +	u16 busy_poll_budget;
> > +
> > +	/* for future fields */
> > +	u8 data[118];
> > +} EPOLL_PACKED;
> > +
> > +#define EPOLL_IOC_TYPE 0x8A
> > +#define EPIOCSPARAMS _IOW(EPOLL_IOC_TYPE, 0x01, struct epoll_params)
> > +#define EPIOCGPARAMS _IOR(EPOLL_IOC_TYPE, 0x02, struct epoll_params)
> > +
> >  #endif /* _UAPI_LINUX_EVENTPOLL_H */
> > -- 
> > 2.25.1
> > 
> 
>
kernel test robot Jan. 25, 2024, 1:12 p.m. UTC | #3 
Hi Joe,

kernel test robot noticed the following build warnings:

[auto build test WARNING on net-next/main]

url:    https://github.com/intel-lab-lkp/linux/commits/Joe-Damato/eventpoll-support-busy-poll-per-epoll-instance/20240125-083418
base:   net-next/main
patch link:    https://lore.kernel.org/r/20240125003014.43103-4-jdamato%40fastly.com
patch subject: [net-next v2 3/4] eventpoll: Add epoll ioctl for epoll_params
config: openrisc-allnoconfig (https://download.01.org/0day-ci/archive/20240125/202401252141.eUlgsF08-lkp@intel.com/config)
compiler: or1k-linux-gcc (GCC) 13.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240125/202401252141.eUlgsF08-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202401252141.eUlgsF08-lkp@intel.com/

All warnings (new ones prefixed by >>):

   fs/eventpoll.c: In function 'ep_eventpoll_ioctl':
>> fs/eventpoll.c:879:22: warning: unused variable 'uarg' [-Wunused-variable]
     879 |         void __user *uarg = (void __user *) arg;
         |                      ^~~~
>> fs/eventpoll.c:878:29: warning: unused variable 'epoll_params' [-Wunused-variable]
     878 |         struct epoll_params epoll_params;
         |                             ^~~~~~~~~~~~
   fs/eventpoll.c:877:27: warning: variable 'ep' set but not used [-Wunused-but-set-variable]
     877 |         struct eventpoll *ep;
         |                           ^~


vim +/uarg +879 fs/eventpoll.c

   873	
   874	static long ep_eventpoll_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
   875	{
   876		int ret;
   877		struct eventpoll *ep;
 > 878		struct epoll_params epoll_params;
 > 879		void __user *uarg = (void __user *) arg;
   880	
   881		if (!is_file_epoll(file))
   882			return -EINVAL;
   883	
   884		ep = file->private_data;
   885	
   886		switch (cmd) {
   887	#ifdef CONFIG_NET_RX_BUSY_POLL
   888		case EPIOCSPARAMS:
   889			if (copy_from_user(&epoll_params, uarg, sizeof(epoll_params)))
   890				return -EFAULT;
   891	
   892			if (epoll_params.busy_poll_budget > NAPI_POLL_WEIGHT)
   893				pr_err("busy poll budget %u exceeds suggested maximum %u\n",
   894						epoll_params.busy_poll_budget, NAPI_POLL_WEIGHT);
   895	
   896			ep->busy_poll_usecs = epoll_params.busy_poll_usecs;
   897			ep->busy_poll_budget = epoll_params.busy_poll_budget;
   898			return 0;
   899	
   900		case EPIOCGPARAMS:
   901			memset(&epoll_params, 0, sizeof(epoll_params));
   902			epoll_params.busy_poll_usecs = ep->busy_poll_usecs;
   903			epoll_params.busy_poll_budget = ep->busy_poll_budget;
   904			if (copy_to_user(uarg, &epoll_params, sizeof(epoll_params)))
   905				return -EFAULT;
   906	
   907			return 0;
   908	#endif
   909		default:
   910			ret = -EINVAL;
   911			break;
   912		}
   913	
   914		return ret;
   915	}
   916
Willem de Bruijn Jan. 25, 2024, 2:11 p.m. UTC | #4 
Joe Damato wrote:
> On Wed, Jan 24, 2024 at 09:46:23PM -0500, Willem de Bruijn wrote:
> > 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 or packet budget
> > > params for a specific epoll context.
> > > 
> > > Signed-off-by: Joe Damato <jdamato@fastly.com>
> > 
> > Please be sure to include the lists and people suggested by
> > `get_maintainer.pl -f fs/eventpoll.c`.
> 
> Thanks - I must have done something wrong when trying to get the maintainer
> list.
> 
> Should I resend this v2? Not sure what the appropriate thing to do is in
> this case. My apologies.

If you don't get additional feedback in a few days and still prefer
this option that might be an approach.

After reading the below thread, compare the different possible APIs
and either revise the code or perhaps add a small paragraph why you
think this is the preferred path.
 
> > Adding ioctls is generally discouraged.
> > 
> > As this affects the behavior of epoll_wait, should this just be a
> > flag to (a new variant of) epoll_wait?
> 
> I have no strong preference either way. It seems to me that adding a new
> system call is a fairly significant change vs adding an ioctl, but I am
> open to whatever is preferred by the maintainers.
> 
> I have no idea who would need to weigh-in to make this decision.
> 
> > Speaking from some experience with adding epoll_pwait2. I initially
> > there added a stateful change that would affect wait behavior. The
> > sensible feedback as the time was to just change the behavior of the
> > syscall it affected. Even if that requires a syscall (which is not
> > that different from an ioctl, if better defined).
> > 
> > The discussion in that thread may be informative to decide on API:
> > https://lwn.net/ml/linux-kernel/20201116161001.1606608-1-willemdebruijn.kernel@gmail.com/
> 
> Interesting thread, thanks for sending.
> 
> > Agreed on the overall principle that it is preferable to be able to
> > enable busypolling selectively. We already do for SO_BUSY_POLL and
> > sysctl busy_read.
> 
> Thanks for taking a look and providing feedback.
> 
> >
> > > ---
> > >  .../userspace-api/ioctl/ioctl-number.rst      |  1 +
> > >  fs/eventpoll.c                                | 47 +++++++++++++++++++
> > >  include/uapi/linux/eventpoll.h                | 12 +++++
> > >  3 files changed, 60 insertions(+)
> > > 
> > > diff --git a/Documentation/userspace-api/ioctl/ioctl-number.rst b/Documentation/userspace-api/ioctl/ioctl-number.rst
> > > index 457e16f06e04..b33918232f78 100644
> > > --- a/Documentation/userspace-api/ioctl/ioctl-number.rst
> > > +++ b/Documentation/userspace-api/ioctl/ioctl-number.rst
> > > @@ -309,6 +309,7 @@ Code  Seq#    Include File                                           Comments
> > >  0x89  0B-DF  linux/sockios.h
> > >  0x89  E0-EF  linux/sockios.h                                         SIOCPROTOPRIVATE range
> > >  0x89  F0-FF  linux/sockios.h                                         SIOCDEVPRIVATE range
> > > +0x8A  00-1F  linux/eventpoll.h
> > >  0x8B  all    linux/wireless.h
> > >  0x8C  00-3F                                                          WiNRADiO driver
> > >                                                                       <http://www.winradio.com.au/>
> > > diff --git a/fs/eventpoll.c b/fs/eventpoll.c
> > > index 40bd97477b91..c1ee0fe01da1 100644
> > > --- a/fs/eventpoll.c
> > > +++ b/fs/eventpoll.c
> > > @@ -6,6 +6,8 @@
> > >   *  Davide Libenzi <davidel@xmailserver.org>
> > >   */
> > >  
> > > +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
> > > +
> > >  #include <linux/init.h>
> > >  #include <linux/kernel.h>
> > >  #include <linux/sched/signal.h>
> > > @@ -869,6 +871,49 @@ static void ep_clear_and_put(struct eventpoll *ep)
> > >  		ep_free(ep);
> > >  }
> > >  
> > > +static long ep_eventpoll_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
> > > +{
> > > +	int ret;
> > > +	struct eventpoll *ep;
> > > +	struct epoll_params epoll_params;
> > > +	void __user *uarg = (void __user *) arg;
> > > +
> > > +	if (!is_file_epoll(file))
> > > +		return -EINVAL;
> > > +
> > > +	ep = file->private_data;
> > > +
> > > +	switch (cmd) {
> > > +#ifdef CONFIG_NET_RX_BUSY_POLL
> > > +	case EPIOCSPARAMS:
> > > +		if (copy_from_user(&epoll_params, uarg, sizeof(epoll_params)))
> > > +			return -EFAULT;
> > > +
> > > +		if (epoll_params.busy_poll_budget > NAPI_POLL_WEIGHT)
> > > +			pr_err("busy poll budget %u exceeds suggested maximum %u\n",
> > > +					epoll_params.busy_poll_budget, NAPI_POLL_WEIGHT);
> > > +
> > > +		ep->busy_poll_usecs = epoll_params.busy_poll_usecs;
> > > +		ep->busy_poll_budget = epoll_params.busy_poll_budget;
> > > +		return 0;
> > > +
> > > +	case EPIOCGPARAMS:
> > > +		memset(&epoll_params, 0, sizeof(epoll_params));
> > > +		epoll_params.busy_poll_usecs = ep->busy_poll_usecs;
> > > +		epoll_params.busy_poll_budget = ep->busy_poll_budget;
> > > +		if (copy_to_user(uarg, &epoll_params, sizeof(epoll_params)))
> > > +			return -EFAULT;
> > > +
> > > +		return 0;
> > > +#endif
> > > +	default:
> > > +		ret = -EINVAL;
> > > +		break;
> > > +	}
> > > +
> > > +	return ret;
> > > +}
> > > +
> > >  static int ep_eventpoll_release(struct inode *inode, struct file *file)
> > >  {
> > >  	struct eventpoll *ep = file->private_data;
> > > @@ -975,6 +1020,8 @@ static const struct file_operations eventpoll_fops = {
> > >  	.release	= ep_eventpoll_release,
> > >  	.poll		= ep_eventpoll_poll,
> > >  	.llseek		= noop_llseek,
> > > +	.unlocked_ioctl	= ep_eventpoll_ioctl,
> > > +	.compat_ioctl   = compat_ptr_ioctl,
> > >  };
> > >  
> > >  /*
> > > diff --git a/include/uapi/linux/eventpoll.h b/include/uapi/linux/eventpoll.h
> > > index cfbcc4cc49ac..8eb0fdbce995 100644
> > > --- a/include/uapi/linux/eventpoll.h
> > > +++ b/include/uapi/linux/eventpoll.h
> > > @@ -85,4 +85,16 @@ struct epoll_event {
> > >  	__u64 data;
> > >  } EPOLL_PACKED;
> > >  
> > > +struct epoll_params {
> > > +	u64 busy_poll_usecs;
> > > +	u16 busy_poll_budget;
> > > +
> > > +	/* for future fields */
> > > +	u8 data[118];
> > > +} EPOLL_PACKED;
> > > +
> > > +#define EPOLL_IOC_TYPE 0x8A
> > > +#define EPIOCSPARAMS _IOW(EPOLL_IOC_TYPE, 0x01, struct epoll_params)
> > > +#define EPIOCGPARAMS _IOR(EPOLL_IOC_TYPE, 0x02, struct epoll_params)
> > > +
> > >  #endif /* _UAPI_LINUX_EVENTPOLL_H */
> > > -- 
> > > 2.25.1
> > > 
> > 
> >
diff mbox series

Patch

diff --git a/Documentation/userspace-api/ioctl/ioctl-number.rst b/Documentation/userspace-api/ioctl/ioctl-number.rst
index 457e16f06e04..b33918232f78 100644
--- a/Documentation/userspace-api/ioctl/ioctl-number.rst
+++ b/Documentation/userspace-api/ioctl/ioctl-number.rst
@@ -309,6 +309,7 @@  Code  Seq#    Include File                                           Comments
 0x89  0B-DF  linux/sockios.h
 0x89  E0-EF  linux/sockios.h                                         SIOCPROTOPRIVATE range
 0x89  F0-FF  linux/sockios.h                                         SIOCDEVPRIVATE range
+0x8A  00-1F  linux/eventpoll.h
 0x8B  all    linux/wireless.h
 0x8C  00-3F                                                          WiNRADiO driver
                                                                      <http://www.winradio.com.au/>
diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 40bd97477b91..c1ee0fe01da1 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -6,6 +6,8 @@ 
  *  Davide Libenzi <davidel@xmailserver.org>
  */
 
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
 #include <linux/init.h>
 #include <linux/kernel.h>
 #include <linux/sched/signal.h>
@@ -869,6 +871,49 @@  static void ep_clear_and_put(struct eventpoll *ep)
 		ep_free(ep);
 }
 
+static long ep_eventpoll_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+	int ret;
+	struct eventpoll *ep;
+	struct epoll_params epoll_params;
+	void __user *uarg = (void __user *) arg;
+
+	if (!is_file_epoll(file))
+		return -EINVAL;
+
+	ep = file->private_data;
+
+	switch (cmd) {
+#ifdef CONFIG_NET_RX_BUSY_POLL
+	case EPIOCSPARAMS:
+		if (copy_from_user(&epoll_params, uarg, sizeof(epoll_params)))
+			return -EFAULT;
+
+		if (epoll_params.busy_poll_budget > NAPI_POLL_WEIGHT)
+			pr_err("busy poll budget %u exceeds suggested maximum %u\n",
+					epoll_params.busy_poll_budget, NAPI_POLL_WEIGHT);
+
+		ep->busy_poll_usecs = epoll_params.busy_poll_usecs;
+		ep->busy_poll_budget = epoll_params.busy_poll_budget;
+		return 0;
+
+	case EPIOCGPARAMS:
+		memset(&epoll_params, 0, sizeof(epoll_params));
+		epoll_params.busy_poll_usecs = ep->busy_poll_usecs;
+		epoll_params.busy_poll_budget = ep->busy_poll_budget;
+		if (copy_to_user(uarg, &epoll_params, sizeof(epoll_params)))
+			return -EFAULT;
+
+		return 0;
+#endif
+	default:
+		ret = -EINVAL;
+		break;
+	}
+
+	return ret;
+}
+
 static int ep_eventpoll_release(struct inode *inode, struct file *file)
 {
 	struct eventpoll *ep = file->private_data;
@@ -975,6 +1020,8 @@  static const struct file_operations eventpoll_fops = {
 	.release	= ep_eventpoll_release,
 	.poll		= ep_eventpoll_poll,
 	.llseek		= noop_llseek,
+	.unlocked_ioctl	= ep_eventpoll_ioctl,
+	.compat_ioctl   = compat_ptr_ioctl,
 };
 
 /*
diff --git a/include/uapi/linux/eventpoll.h b/include/uapi/linux/eventpoll.h
index cfbcc4cc49ac..8eb0fdbce995 100644
--- a/include/uapi/linux/eventpoll.h
+++ b/include/uapi/linux/eventpoll.h
@@ -85,4 +85,16 @@  struct epoll_event {
 	__u64 data;
 } EPOLL_PACKED;
 
+struct epoll_params {
+	u64 busy_poll_usecs;
+	u16 busy_poll_budget;
+
+	/* for future fields */
+	u8 data[118];
+} EPOLL_PACKED;
+
+#define EPOLL_IOC_TYPE 0x8A
+#define EPIOCSPARAMS _IOW(EPOLL_IOC_TYPE, 0x01, struct epoll_params)
+#define EPIOCGPARAMS _IOR(EPOLL_IOC_TYPE, 0x02, struct epoll_params)
+
 #endif /* _UAPI_LINUX_EVENTPOLL_H */