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From: Roman Penyaev <rpenyaev@suse.de>
To: unlisted-recipients:; (no To-header on input)
Cc: Azat Khuzhin <azat@libevent.org>,
	Roman Penyaev <rpenyaev@suse.de>,
	Andrew Morton <akpm@linux-foundation.org>,
	Al Viro <viro@zeniv.linux.org.uk>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH v3 02/13] epoll: introduce user structures for polling from userspace
Date: Thu, 16 May 2019 10:57:59 +0200
Message-ID: <20190516085810.31077-3-rpenyaev@suse.de> (raw)
In-Reply-To: <20190516085810.31077-1-rpenyaev@suse.de>

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

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@xmailserver.org>
  *
+ *  Polling from userspace support by Roman Penyaev <rpenyaev@suse.de>
+ *  (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..161dfcbcf3b5 100644
--- a/include/uapi/linux/eventpoll.h
+++ b/include/uapi/linux/eventpoll.h
@@ -79,4 +79,32 @@ 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[] __aligned(EPOLL_USERPOLL_HEADER_SIZE);
+};
+
 #endif /* _UAPI_LINUX_EVENTPOLL_H */
-- 
2.21.0


  parent reply index

Thread overview: 50+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-16  8:57 [PATCH v3 00/13] epoll: support pollable epoll " Roman Penyaev
2019-05-16  8:57 ` [PATCH v3 01/13] epoll: move private helpers from a header to the source Roman Penyaev
2019-05-16  8:57 ` Roman Penyaev [this message]
2019-05-16  8:58 ` [PATCH v3 03/13] epoll: allocate user header and user events ring for polling from userspace Roman Penyaev
2019-05-16  8:58 ` [PATCH v3 04/13] epoll: some sanity flags checks for epoll syscalls " Roman Penyaev
2019-05-16  8:58 ` [PATCH v3 05/13] epoll: offload polling to a work in case of epfd polled " Roman Penyaev
2019-05-21  7:51   ` Eric Wong
2019-05-22 12:54     ` Roman Penyaev
2019-05-16  8:58 ` [PATCH v3 06/13] epoll: introduce helpers for adding/removing events to uring Roman Penyaev
2019-05-31  9:55   ` Peter Zijlstra
2019-05-31 11:24     ` Roman Penyaev
2019-05-31 13:11       ` Peter Zijlstra
2019-05-31  9:56   ` Peter Zijlstra
2019-05-31 11:15     ` Roman Penyaev
2019-05-31 12:53       ` Peter Zijlstra
2019-05-31 14:28         ` Roman Penyaev
2019-05-31 16:53           ` Peter Zijlstra
2019-05-31 12:56       ` Peter Zijlstra
2019-05-31 14:21         ` Roman Penyaev
2019-05-31 16:51           ` Peter Zijlstra
2019-05-31 18:58             ` Roman Penyaev
2019-06-03  9:09               ` Peter Zijlstra
2019-06-03 10:02                 ` Roman Penyaev
2019-05-16  8:58 ` [PATCH v3 07/13] epoll: call ep_add_event_to_uring() from ep_poll_callback() Roman Penyaev
2019-05-31  9:56   ` Peter Zijlstra
2019-05-31 11:22     ` Roman Penyaev
2019-05-31 13:05       ` Peter Zijlstra
2019-05-31 15:05         ` Roman Penyaev
2019-05-16  8:58 ` [PATCH v3 08/13] epoll: support polling from userspace for ep_insert() Roman Penyaev
2019-05-16  8:58 ` [PATCH v3 09/13] epoll: support polling from userspace for ep_remove() Roman Penyaev
2019-05-16  8:58 ` [PATCH v3 10/13] epoll: support polling from userspace for ep_modify() Roman Penyaev
2019-05-16  8:58 ` [PATCH v3 11/13] epoll: support polling from userspace for ep_poll() Roman Penyaev
2019-05-16  8:58 ` [PATCH v3 12/13] epoll: support mapping for epfd when polled from userspace Roman Penyaev
2019-05-16  8:58 ` [PATCH v3 13/13] epoll: implement epoll_create2() syscall Roman Penyaev
2019-05-16 10:03   ` Arnd Bergmann
2019-05-16 10:20     ` Roman Penyaev
2019-05-16 10:57       ` Arnd Bergmann
2019-05-22  2:33       ` Andrew Morton
2019-05-22  9:11         ` Roman Penyaev
2019-05-22 11:14         ` Arnd Bergmann
2019-05-22 18:36           ` Andrew Morton
2019-05-31  9:55 ` [PATCH v3 00/13] epoll: support pollable epoll from userspace Peter Zijlstra
2019-05-31 14:48 ` Jens Axboe
2019-05-31 16:02   ` Roman Penyaev
2019-05-31 16:54     ` Jens Axboe
2019-05-31 19:45       ` Roman Penyaev
2019-05-31 21:09         ` Jens Axboe
2019-06-05  6:17           ` Roman Penyaev
2019-05-31 16:33 ` Peter Zijlstra
2019-05-31 18:50   ` Roman Penyaev

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