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eventpoll: Add epoll ioctl for epoll_params

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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: Joe Damato <jdamato@fastly.com>
Acked-by: Stanislav Fomichev <sdf@google.com>
Reviewed-by: Jiri Slaby <jirislaby@kernel.org>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Joe Damato 2024-02-13 06:16:45 +00:00 committed by David S. Miller
parent de57a25108
commit 18e2bf0edf
3 changed files with 87 additions and 0 deletions
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1
Documentation/userspace-api/ioctl/ioctl-number.rst
View file

@ -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/>

73
fs/eventpoll.c
View file

@ -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,
};
/*

13
include/uapi/linux/eventpoll.h
View file

@ -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 */