Commit 18e2bf0e authored by Joe Damato's avatar Joe Damato Committed by David S. Miller
Browse files

eventpoll: Add epoll ioctl for epoll_params 



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 <= s32_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: default avatarJoe Damato <jdamato@fastly.com>
Acked-by: default avatarStanislav Fomichev <sdf@google.com>
Reviewed-by: default avatarJiri Slaby <jirislaby@kernel.org>
Reviewed-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent de57a251

Documentation/userspace-api/ioctl/ioctl-number.rst

+1 −0
Original line number Diff line number Diff line
@@ -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/>

fs/eventpoll.c

+73 −0
Original line number Diff line number Diff line
@@ -37,6 +37,7 @@ 
#include <linux/seq_file.h>

#include <linux/compat.h>

#include <linux/rculist.h>

#include <linux/capability.h>

#include <net/busy_poll.h>



/*
@@ -494,6 +495,49 @@ 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 = file->private_data;

	void __user *uarg = (void __user *)arg;

	struct epoll_params epoll_params;



	switch (cmd) {

	case EPIOCSPARAMS:

		if (copy_from_user(&epoll_params, uarg, sizeof(epoll_params)))

			return -EFAULT;



		/* pad byte must be zero */

		if (epoll_params.__pad)

			return -EINVAL;



		if (epoll_params.busy_poll_usecs > S32_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;



		WRITE_ONCE(ep->busy_poll_usecs, epoll_params.busy_poll_usecs);

		WRITE_ONCE(ep->busy_poll_budget, epoll_params.busy_poll_budget);

		WRITE_ONCE(ep->prefer_busy_poll, epoll_params.prefer_busy_poll);

		return 0;

	case EPIOCGPARAMS:

		memset(&epoll_params, 0, sizeof(epoll_params));

		epoll_params.busy_poll_usecs = READ_ONCE(ep->busy_poll_usecs);

		epoll_params.busy_poll_budget = READ_ONCE(ep->busy_poll_budget);

		epoll_params.prefer_busy_poll = READ_ONCE(ep->prefer_busy_poll);

		if (copy_to_user(uarg, &epoll_params, sizeof(epoll_params)))

			return -EFAULT;

		return 0;

	default:

		return -ENOIOCTLCMD;

	}

}



#else



static inline bool ep_busy_loop(struct eventpoll *ep, int nonblock)
@@ -505,6 +549,12 @@ static inline void ep_set_busy_poll_napi_id(struct epitem *epi) 
{

}



static long ep_eventpoll_bp_ioctl(struct file *file, unsigned int cmd,

				  unsigned long arg)

{

	return -EOPNOTSUPP;

}



#endif /* CONFIG_NET_RX_BUSY_POLL */



/*
@@ -864,6 +914,27 @@ 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;



	if (!is_file_epoll(file))

		return -EINVAL;



	switch (cmd) {

	case EPIOCSPARAMS:

	case EPIOCGPARAMS:

		ret = ep_eventpoll_bp_ioctl(file, cmd, arg);

		break;

	default:

		ret = -EINVAL;

		break;

	}



	return ret;

}



static int ep_eventpoll_release(struct inode *inode, struct file *file)

{

	struct eventpoll *ep = file->private_data;
@@ -970,6 +1041,8 @@ 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,

};



/*

include/uapi/linux/eventpoll.h

+13 −0
Original line number Diff line number Diff line
@@ -85,4 +85,17 @@ struct epoll_event { 
	__u64 data;

} EPOLL_PACKED;



struct epoll_params {

	__u32 busy_poll_usecs;

	__u16 busy_poll_budget;

	__u8 prefer_busy_poll;



	/* pad the struct to a multiple of 64bits */

	__u8 __pad;

};



#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 */