[PATCH net-next v3 3/3] eventpoll: Add epoll ioctl for epoll_params

Joe Damato
2024-01-25T22:57:54Z

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 | 64 +++++++++++++++++++
include/uapi/linux/eventpoll.h | 12 ++++
3 files changed, 77 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..73ae886efb8a 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>
@@ -37,6 +39,7 @@
#include <linux/seq_file.h>
#include <linux/compat.h>
#include <linux/rculist.h>
+#include <linux/capability.h>
#include <net/busy_poll.h>

/*
@@ -495,6 +498,39 @@ 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;
+
+ switch (cmd) {
+ case EPIOCSPARAMS:
+ if (copy_from_user(&epoll_params, uarg, sizeof(epoll_params)))
+ return -EFAULT;
+
+ 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;
+ 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;
+ default:
+ return -ENOIOCTLCMD;
+ }
+}
+
#else

static inline bool ep_busy_loop(struct eventpoll *ep, int nonblock)
@@ -510,6 +546,12 @@ static inline bool ep_busy_loop_on(struct eventpoll *ep)
{
return false;
}
+
+static long ep_eventpoll_bp_ioctl(struct file *file, unsigned int cmd,
+ unsigned long arg)
+{
+ return -EOPNOTSUPP;
+}
#endif /* CONFIG_NET_RX_BUSY_POLL */

/*
@@ -869,6 +911,26 @@ 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;
@@ -975,6 +1037,8 @@ 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