ia64/xen-unstable

view tools/blktap2/drivers/tapdisk-ring.h @ 19647:1c627434605e

blktap2: a completely rewritten blktap implementation

Benefits to blktap2 over the old version of blktap:

* Isolation from xenstore - Blktap devices are now created directly on
the linux dom0 command line, rather than being spawned in response
to XenStore events. This is handy for debugging, makes blktap
generally easier to work with, and is a step toward a generic
user-level block device implementation that is not Xen-specific.

* Improved tapdisk infrastructure: simpler request forwarding, new
request scheduler, request merging, more efficient use of AIO.

* Improved tapdisk error handling and memory management. No
allocations on the block data path, IO retry logic to protect
guests
transient block device failures. This has been tested and is known
to work on weird environments such as NFS soft mounts.

* Pause and snapshot of live virtual disks (see xmsnap script).

* VHD support. The VHD code in this release has been rigorously
tested, and represents a very mature implementation of the VHD
image
format.

* No more duplication of mechanism with blkback. The blktap kernel
module has changed dramatically from the original blktap. Blkback
is now always used to talk to Xen guests, blktap just presents a
Linux gendisk that blkback can export. This is done while
preserving the zero-copy data path from domU to physical device.

These patches deprecate the old blktap code, which can hopefully be
removed from the tree completely at some point in the future.

Signed-off-by: Jake Wires <jake.wires@citrix.com>
Signed-off-by: Dutch Meyer <dmeyer@cs.ubc.ca>
author Keir Fraser <keir.fraser@citrix.com>
date Tue May 26 11:52:31 2009 +0100 (2009-05-26)
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1 /*
2 * Copyright (c) 2008, XenSource Inc.
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions are met:
7 * * Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * * Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
12 * * Neither the name of XenSource Inc. nor the names of its contributors
13 * may be used to endorse or promote products derived from this software
14 * without specific prior written permission.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
17 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
18 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
19 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
20 * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
21 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
22 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
23 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
24 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
25 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
26 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 */
28 #ifndef _TAPDISK_RING_H_
29 #define _TAPDISK_RING_H_
31 #include <inttypes.h>
33 #include <xenctrl.h>
34 #include <xen/io/ring.h>
36 typedef struct td_uring td_uring_t;
37 typedef struct td_uring_header td_uring_header_t;
38 typedef struct td_uring_request td_uring_request_t;
39 typedef struct td_uring_response td_uring_response_t;
41 struct td_uring {
42 int ctlfd;
44 char *shmem_path;
45 char *ctlfd_path;
47 void *shmem;
48 void *ring_area;
49 void *data_area;
50 };
52 struct td_uring_header {
53 char cookie[8];
54 uint32_t version;
55 uint32_t shmem_size;
56 uint32_t ring_size;
57 uint32_t data_size;
58 char reserved[4064];
59 };
61 struct td_uring_request {
62 uint8_t op;
63 uint64_t id;
64 uint64_t sec;
65 uint32_t secs;
66 uint32_t offset;
67 };
69 struct td_uring_response {
70 uint8_t op;
71 uint64_t id;
72 uint8_t status;
73 };
75 DEFINE_RING_TYPES(td_uring, td_uring_request_t, td_uring_response_t);
77 int tapdisk_uring_create(td_uring_t *, const char *location,
78 uint32_t ring_size, uint32_t data_size);
79 int tapdisk_uring_destroy(td_uring_t *);
81 int tapdisk_uring_connect(td_uring_t *, const char *location);
82 int tapdisk_uring_disconnect(td_uring_t *);
84 int tapdisk_uring_poll(td_uring_t *);
85 int tapdisk_uring_kick(td_uring_t *);
87 #endif