Messages in this thread Patch in this message | | | From | Roman Penyaev <> | Subject | [PATCH v4 02/14] epoll: introduce user structures for polling from userspace | Date | Tue, 11 Jun 2019 16:54:46 +0200 |
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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(+)
diff --git a/fs/eventpoll.c b/fs/eventpoll.c index 50bb99e98872..90dc75ad4144 100644 --- a/fs/eventpoll.c +++ b/fs/eventpoll.c @@ -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; diff --git a/include/uapi/linux/eventpoll.h b/include/uapi/linux/eventpoll.h index 39dfc29f0f52..3317901b19c4 100644 --- a/include/uapi/linux/eventpoll.h +++ b/include/uapi/linux/eventpoll.h @@ -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 */ -- 2.21.0
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