ia64/xen-unstable

view tools/blktap2/drivers/qcow.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 */
29 #ifndef _QCOW_H_
30 #define _QCOW_H_
32 #include "aes.h"
33 /**************************************************************/
34 /* QEMU COW block driver with compression and encryption support */
36 #define QCOW_MAGIC (('Q' << 24) | ('F' << 16) | ('I' << 8) | 0xfb)
37 #define XEN_MAGIC (('X' << 24) | ('E' << 16) | ('N' << 8) | 0xfb)
38 #define QCOW_VERSION 1
40 #define QCOW_CRYPT_NONE 0x00
41 #define QCOW_CRYPT_AES 0x01
43 #define QCOW_OFLAG_COMPRESSED (1LL << 63)
44 #define SPARSE_FILE 0x01
45 #define EXTHDR_L1_BIG_ENDIAN 0x02
47 #ifndef O_BINARY
48 #define O_BINARY 0
49 #endif
51 #define ROUNDUP(l, s) \
52 ({ \
53 (uint64_t)( \
54 (l + (s - 1)) - ((l + (s - 1)) % s)); \
55 })
57 typedef struct QCowHeader {
58 uint32_t magic;
59 uint32_t version;
60 uint64_t backing_file_offset;
61 uint32_t backing_file_size;
62 uint32_t mtime;
63 uint64_t size; /* in bytes */
64 uint8_t cluster_bits;
65 uint8_t l2_bits;
66 uint32_t crypt_method;
67 uint64_t l1_table_offset;
68 } QCowHeader;
70 /*Extended header for Xen enhancements*/
71 typedef struct QCowHeader_ext {
72 uint32_t xmagic;
73 uint32_t cksum;
74 uint32_t min_cluster_alloc;
75 uint32_t flags;
76 } QCowHeader_ext;
78 uint32_t gen_cksum(char *ptr, int len);
79 int get_filesize(char *filename, uint64_t *size, struct stat *st);
80 int qtruncate(int fd, off_t length, int sparse);
82 #define L2_CACHE_SIZE 16 /*Fixed allocation in Qemu*/
84 struct tdqcow_state {
85 int fd; /*Main Qcow file descriptor */
86 uint64_t fd_end; /*Store a local record of file length */
87 char *name; /*Record of the filename*/
88 uint32_t backing_file_size;
89 uint64_t backing_file_offset;
90 uint8_t extended; /*File contains extended header*/
91 int encrypted; /*File contents are encrypted or plain*/
92 int cluster_bits; /*Determines length of cluster as
93 *indicated by file hdr*/
94 int cluster_size; /*Length of cluster*/
95 int cluster_sectors; /*Number of sectors per cluster*/
96 int cluster_alloc; /*Blktap fix for allocating full
97 *extents*/
98 int min_cluster_alloc; /*Blktap historical extent alloc*/
99 int sparse; /*Indicates whether to preserve sparseness*/
100 int l2_bits; /*Size of L2 table entry*/
101 int l2_size; /*Full table size*/
102 int l1_size; /*L1 table size*/
103 uint64_t cluster_offset_mask;
104 uint64_t l1_table_offset; /*L1 table offset from beginning of
105 *file*/
106 uint64_t *l1_table; /*L1 table entries*/
107 uint64_t *l2_cache; /*We maintain a cache of size
108 *L2_CACHE_SIZE of most read entries*/
109 uint64_t l2_cache_offsets[L2_CACHE_SIZE]; /*L2 cache entries*/
110 uint32_t l2_cache_counts[L2_CACHE_SIZE]; /*Cache access record*/
111 uint8_t *cluster_cache;
112 uint8_t *cluster_data;
113 uint64_t cluster_cache_offset; /**/
114 uint32_t crypt_method; /*current crypt method, 0 if no
115 *key yet */
116 uint32_t crypt_method_header; /**/
117 AES_KEY aes_encrypt_key; /*AES key*/
118 AES_KEY aes_decrypt_key; /*AES key*/
120 /* libaio state */
121 int aio_free_count;
122 int max_aio_reqs;
123 struct qcow_request *aio_requests;
124 struct qcow_request **aio_free_list;
126 };
128 int qcow_create(const char *filename, uint64_t total_size,
129 const char *backing_file, int sparse);
131 #endif //_QCOW_H_