@@ -4,6 +4,7 @@
* Copyright (C) 2001,...,2009 Davide Libenzi
*
* Davide Libenzi <davidel@xmailserver.org>
+ * Polling from userspace support by Roman Penyaev <rpenyaev@suse.de>
*/
#include <linux/init.h>
@@ -104,6 +105,16 @@
#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.
+ *
+ * Before increasing the value see add_event_to_uring() and especially
+ * cnt_to_advance() functions and change them accordingly.
+ */
+#define EP_USERPOLL_MAX_ITEMS_NR 65536
+
struct epoll_filefd {
struct file *file;
int fd;
@@ -79,4 +79,33 @@ struct epoll_event {
__u64 data;
} EPOLL_PACKED;
+#define EPOLL_USERPOLL_HEADER_MAGIC 0xeb01eb01
+#define EPOLL_USERPOLL_HEADER_SIZE 128
+
+/*
+ * Item, shared with userspace. Unfortunately we can't embed epoll_event
+ * structure, because it is badly aligned on all 64-bit archs, except
+ * x86-64 (see EPOLL_PACKED). sizeof(epoll_uitem) == 16
+ */
+struct epoll_uitem {
+ __poll_t ready_events;
+ __poll_t events;
+ __u64 data;
+};
+
+/*
+ * Header, shared with userspace. sizeof(epoll_uheader) == 128
+ */
+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[]
+ __attribute__((__aligned__(EPOLL_USERPOLL_HEADER_SIZE)));
+};
+
#endif /* _UAPI_LINUX_EVENTPOLL_H */
This one introduces structures of user items array: struct epoll_uheader - describes inserted epoll items. struct epoll_uitem - single epoll item visible to userspace. Signed-off-by: Roman Penyaev <rpenyaev@suse.de> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: linux-fsdevel@vger.kernel.org Cc: linux-kernel@vger.kernel.org --- fs/eventpoll.c | 11 +++++++++++ include/uapi/linux/eventpoll.h | 29 +++++++++++++++++++++++++++++ 2 files changed, 40 insertions(+)