This one introduces structures of user items array:
struct user_epheader -
describes inserted epoll items.
struct user_epitem -
single epoll item, visible to userspace.
Signed-off-by: Roman Penyaev <rpenyaev@xxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Davidlohr Bueso <dbueso@xxxxxxx>
Cc: Jason Baron <jbaron@xxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Andrea Parri <andrea.parri@xxxxxxxxxxxxxxxxxxxx>
Cc: linux-fsdevel@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
---
fs/eventpoll.c | 9 +++++++++
include/uapi/linux/eventpoll.h | 19 +++++++++++++++++++
2 files changed, 28 insertions(+)
diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 2cc183e86a29..f598442512f3 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -9,6 +9,8 @@
*
* Davide Libenzi <davidel@xxxxxxxxxxxxxxx>
*
+ * Polling from userspace support by Roman Penyaev <rpenyaev@xxxxxxx>
+ * (C) Copyright 2019 SUSE, All Rights Reserved
*/
#include <linux/init.h>
@@ -109,6 +111,13 @@
#define EP_ITEM_COST (sizeof(struct epitem) + sizeof(struct eppoll_entry))
+/*
+ * That is around 1.3mb of allocated memory for one epfd. What is more
+ * important is ->index_length, which should be ^2, so do not increase
+ * max items number to avoid size doubling of user index.
+ */
+#define EP_USERPOLL_MAX_ITEMS_NR 65536
+
struct epoll_filefd {
struct file *file;
int fd;
diff --git a/include/uapi/linux/eventpoll.h b/include/uapi/linux/eventpoll.h
index 39dfc29f0f52..690a625ddeb2 100644
--- a/include/uapi/linux/eventpoll.h
+++ b/include/uapi/linux/eventpoll.h
@@ -79,4 +79,23 @@ struct epoll_event {
__u64 data;
} EPOLL_PACKED;
+struct epoll_uitem {
+ __poll_t ready_events;
+ struct epoll_event event;
+};
+
+#define EPOLL_USERPOLL_HEADER_SIZE 128
+#define EPOLL_USERPOLL_HEADER_MAGIC 0xeb01eb01
+
+struct epoll_uheader {
+ u32 magic; /* epoll user header magic */
+ u32 header_length; /* length of the header + items */
+ u32 index_length; /* length of the index ring, always pow2 */
+ u32 max_items_nr; /* max number of items */
+ u32 head; /* updated by userland */
+ u32 tail; /* updated by kernel */
+
+ struct epoll_uitem items[] __aligned(EPOLL_USERPOLL_HEADER_SIZE);
+};
+
#endif /* _UAPI_LINUX_EVENTPOLL_H */
--
2.19.1
