linux-kernel - [PATCH v1 2/5] uapi: Add dm-user structure definition

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Message-Id: <20201203215859.2719888-3-palmer@dabbelt.com>
Date:   Thu,  3 Dec 2020 13:58:56 -0800
From:   Palmer Dabbelt <palmer@...belt.com>
To:     dm-devel@...hat.com, agk@...hat.com, snitzer@...hat.com
Cc:     corbet@....net, song@...nel.org,
        Palmer Dabbelt <palmerdabbelt@...gle.com>, shuah@...nel.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-raid@...r.kernel.org, linux-kselftest@...r.kernel.org,
        kernel-team@...roid.com
Subject: [PATCH v1 2/5] uapi: Add dm-user structure definition

From: Palmer Dabbelt <palmerdabbelt@...gle.com>

dm-user is a device mapper target that allows a userspace process to
handle each incoming BIO.  Communication with userspace consists of a
stream of messages proxied over a misc device, the structure of each
message is defined in this header.

Signed-off-by: Palmer Dabbelt <palmerdabbelt@...gle.com>

---

As it currently stands this isn't really sufficient to be a stable user
ABI.  These are probably best discussed in the context of the dm-user
implementation, though, where they're largely called out as FIXMEs.
---
 include/uapi/linux/dm-user.h | 67 ++++++++++++++++++++++++++++++++++++
 1 file changed, 67 insertions(+)
 create mode 100644 include/uapi/linux/dm-user.h

diff --git a/include/uapi/linux/dm-user.h b/include/uapi/linux/dm-user.h
new file mode 100644
index 000000000000..1806109518f4
--- /dev/null
+++ b/include/uapi/linux/dm-user.h
@@ -0,0 +1,67 @@
+/* SPDX-License-Identifier: LGPL-2.0+ WITH Linux-syscall-note */
+/*
+ * Copyright (C) 2020 Palmer Dabbelt <palmerdabbelt@...gle.com>
+ */
+
+#ifndef _LINUX_DM_USER_H
+#define _LINUX_DM_USER_H
+
+#include <linux/types.h>
+
+/*
+ * dm-user proxies device mapper ops between the kernel and userspace.  It's
+ * essentially just an RPC mechanism: all kernel calls create a request,
+ * userspace handles that with a response.  Userspace obtains requests via
+ * read() and provides responses via write().
+ *
+ * See Documentation/block/dm-user.rst for more information.
+ */
+
+#define DM_USER_REQ_MAP_READ 0
+#define DM_USER_REQ_MAP_WRITE 1
+#define DM_USER_REQ_MAP_FLUSH 2
+#define DM_USER_REQ_MAP_DISCARD 3
+#define DM_USER_REQ_MAP_SECURE_ERASE 4
+#define DM_USER_REQ_MAP_WRITE_SAME 5
+#define DM_USER_REQ_MAP_WRITE_ZEROES 6
+#define DM_USER_REQ_MAP_ZONE_OPEN 7
+#define DM_USER_REQ_MAP_ZONE_CLOSE 8
+#define DM_USER_REQ_MAP_ZONE_FINISH 9
+#define DM_USER_REQ_MAP_ZONE_APPEND 10
+#define DM_USER_REQ_MAP_ZONE_RESET 11
+#define DM_USER_REQ_MAP_ZONE_RESET_ALL 12
+
+#define DM_USER_REQ_MAP_FLAG_FAILFAST_DEV 0x00001
+#define DM_USER_REQ_MAP_FLAG_FAILFAST_TRANSPORT 0x00002
+#define DM_USER_REQ_MAP_FLAG_FAILFAST_DRIVER 0x00004
+#define DM_USER_REQ_MAP_FLAG_SYNC 0x00008
+#define DM_USER_REQ_MAP_FLAG_META 0x00010
+#define DM_USER_REQ_MAP_FLAG_PRIO 0x00020
+#define DM_USER_REQ_MAP_FLAG_NOMERGE 0x00040
+#define DM_USER_REQ_MAP_FLAG_IDLE 0x00080
+#define DM_USER_REQ_MAP_FLAG_INTEGRITY 0x00100
+#define DM_USER_REQ_MAP_FLAG_FUA 0x00200
+#define DM_USER_REQ_MAP_FLAG_PREFLUSH 0x00400
+#define DM_USER_REQ_MAP_FLAG_RAHEAD 0x00800
+#define DM_USER_REQ_MAP_FLAG_BACKGROUND 0x01000
+#define DM_USER_REQ_MAP_FLAG_NOWAIT 0x02000
+#define DM_USER_REQ_MAP_FLAG_CGROUP_PUNT 0x04000
+#define DM_USER_REQ_MAP_FLAG_NOUNMAP 0x08000
+#define DM_USER_REQ_MAP_FLAG_HIPRI 0x10000
+#define DM_USER_REQ_MAP_FLAG_DRV 0x20000
+#define DM_USER_REQ_MAP_FLAG_SWAP 0x40000
+
+#define DM_USER_RESP_SUCCESS 0
+#define DM_USER_RESP_ERROR 1
+#define DM_USER_RESP_UNSUPPORTED 2
+
+struct dm_user_message {
+	__u64 seq;
+	__u64 type;
+	__u64 flags;
+	__u64 sector;
+	__u64 len;
+	__u8 buf[];
+};
+
+#endif
-- 
2.29.2.454.gaff20da3a2-goog