debuggers.hg

view tools/ioemu/block-cow.c @ 10969:3ea0a6847198

[qemu] Make sure disk writes really made it to disk before we report I/O
completion to the guest domain. The DMA_MULTI_THREAD functionality
from the qemu-dm IDE emulation should make the performance overhead
of synchronous writes bearable, or at least comparable to native
hardware.

Signed-off-by: Rik van Riel <riel@redhat.com>
author chris@kneesaa.uk.xensource.com
date Fri Aug 04 10:28:51 2006 +0100 (2006-08-04)
parents b450f21472a0
children 08a11694b109
line source
1 /*
2 * Block driver for the COW format
3 *
4 * Copyright (c) 2004 Fabrice Bellard
5 *
6 * Permission is hereby granted, free of charge, to any person obtaining a copy
7 * of this software and associated documentation files (the "Software"), to deal
8 * in the Software without restriction, including without limitation the rights
9 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
10 * copies of the Software, and to permit persons to whom the Software is
11 * furnished to do so, subject to the following conditions:
12 *
13 * The above copyright notice and this permission notice shall be included in
14 * all copies or substantial portions of the Software.
15 *
16 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
17 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
18 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
19 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
20 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
21 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
22 * THE SOFTWARE.
23 */
24 #ifndef _WIN32
25 #include "vl.h"
26 #include "block_int.h"
27 #include <sys/mman.h>
29 /**************************************************************/
30 /* COW block driver using file system holes */
32 /* user mode linux compatible COW file */
33 #define COW_MAGIC 0x4f4f4f4d /* MOOO */
34 #define COW_VERSION 2
36 struct cow_header_v2 {
37 uint32_t magic;
38 uint32_t version;
39 char backing_file[1024];
40 int32_t mtime;
41 uint64_t size;
42 uint32_t sectorsize;
43 };
45 typedef struct BDRVCowState {
46 int fd;
47 uint8_t *cow_bitmap; /* if non NULL, COW mappings are used first */
48 uint8_t *cow_bitmap_addr; /* mmap address of cow_bitmap */
49 int cow_bitmap_size;
50 int64_t cow_sectors_offset;
51 } BDRVCowState;
53 static int cow_probe(const uint8_t *buf, int buf_size, const char *filename)
54 {
55 const struct cow_header_v2 *cow_header = (const void *)buf;
57 if (buf_size >= sizeof(struct cow_header_v2) &&
58 be32_to_cpu(cow_header->magic) == COW_MAGIC &&
59 be32_to_cpu(cow_header->version) == COW_VERSION)
60 return 100;
61 else
62 return 0;
63 }
65 static int cow_open(BlockDriverState *bs, const char *filename)
66 {
67 BDRVCowState *s = bs->opaque;
68 int fd;
69 struct cow_header_v2 cow_header;
70 int64_t size;
72 fd = open(filename, O_RDWR | O_BINARY | O_LARGEFILE | O_SYNC);
73 if (fd < 0) {
74 fd = open(filename, O_RDONLY | O_BINARY | O_LARGEFILE);
75 if (fd < 0)
76 return -1;
77 }
78 s->fd = fd;
79 /* see if it is a cow image */
80 if (read(fd, &cow_header, sizeof(cow_header)) != sizeof(cow_header)) {
81 goto fail;
82 }
84 if (be32_to_cpu(cow_header.magic) != COW_MAGIC ||
85 be32_to_cpu(cow_header.version) != COW_VERSION) {
86 goto fail;
87 }
89 /* cow image found */
90 size = be64_to_cpu(cow_header.size);
91 bs->total_sectors = size / 512;
93 pstrcpy(bs->backing_file, sizeof(bs->backing_file),
94 cow_header.backing_file);
96 #if 0
97 if (cow_header.backing_file[0] != '\0') {
98 if (stat(cow_header.backing_file, &st) != 0) {
99 fprintf(stderr, "%s: could not find original disk image '%s'\n", filename, cow_header.backing_file);
100 goto fail;
101 }
102 if (st.st_mtime != be32_to_cpu(cow_header.mtime)) {
103 fprintf(stderr, "%s: original raw disk image '%s' does not match saved timestamp\n", filename, cow_header.backing_file);
104 goto fail;
105 }
106 fd = open(cow_header.backing_file, O_RDONLY | O_LARGEFILE);
107 if (fd < 0)
108 goto fail;
109 bs->fd = fd;
110 }
111 #endif
112 /* mmap the bitmap */
113 s->cow_bitmap_size = ((bs->total_sectors + 7) >> 3) + sizeof(cow_header);
114 s->cow_bitmap_addr = mmap(get_mmap_addr(s->cow_bitmap_size),
115 s->cow_bitmap_size,
116 PROT_READ | PROT_WRITE,
117 MAP_SHARED, s->fd, 0);
118 if (s->cow_bitmap_addr == MAP_FAILED)
119 goto fail;
120 s->cow_bitmap = s->cow_bitmap_addr + sizeof(cow_header);
121 s->cow_sectors_offset = (s->cow_bitmap_size + 511) & ~511;
122 return 0;
123 fail:
124 close(fd);
125 return -1;
126 }
128 static inline void cow_set_bit(uint8_t *bitmap, int64_t bitnum)
129 {
130 bitmap[bitnum / 8] |= (1 << (bitnum%8));
131 }
133 static inline int is_bit_set(const uint8_t *bitmap, int64_t bitnum)
134 {
135 return !!(bitmap[bitnum / 8] & (1 << (bitnum%8)));
136 }
139 /* Return true if first block has been changed (ie. current version is
140 * in COW file). Set the number of continuous blocks for which that
141 * is true. */
142 static inline int is_changed(uint8_t *bitmap,
143 int64_t sector_num, int nb_sectors,
144 int *num_same)
145 {
146 int changed;
148 if (!bitmap || nb_sectors == 0) {
149 *num_same = nb_sectors;
150 return 0;
151 }
153 changed = is_bit_set(bitmap, sector_num);
154 for (*num_same = 1; *num_same < nb_sectors; (*num_same)++) {
155 if (is_bit_set(bitmap, sector_num + *num_same) != changed)
156 break;
157 }
159 return changed;
160 }
162 static int cow_is_allocated(BlockDriverState *bs, int64_t sector_num,
163 int nb_sectors, int *pnum)
164 {
165 BDRVCowState *s = bs->opaque;
166 return is_changed(s->cow_bitmap, sector_num, nb_sectors, pnum);
167 }
169 static int cow_read(BlockDriverState *bs, int64_t sector_num,
170 uint8_t *buf, int nb_sectors)
171 {
172 BDRVCowState *s = bs->opaque;
173 int ret, n;
175 while (nb_sectors > 0) {
176 if (is_changed(s->cow_bitmap, sector_num, nb_sectors, &n)) {
177 lseek(s->fd, s->cow_sectors_offset + sector_num * 512, SEEK_SET);
178 ret = read(s->fd, buf, n * 512);
179 if (ret != n * 512)
180 return -1;
181 } else {
182 memset(buf, 0, n * 512);
183 }
184 nb_sectors -= n;
185 sector_num += n;
186 buf += n * 512;
187 }
188 return 0;
189 }
191 static int cow_write(BlockDriverState *bs, int64_t sector_num,
192 const uint8_t *buf, int nb_sectors)
193 {
194 BDRVCowState *s = bs->opaque;
195 int ret, i;
197 lseek(s->fd, s->cow_sectors_offset + sector_num * 512, SEEK_SET);
198 ret = write(s->fd, buf, nb_sectors * 512);
199 if (ret != nb_sectors * 512)
200 return -1;
201 for (i = 0; i < nb_sectors; i++)
202 cow_set_bit(s->cow_bitmap, sector_num + i);
203 return 0;
204 }
206 static void cow_close(BlockDriverState *bs)
207 {
208 BDRVCowState *s = bs->opaque;
209 munmap(s->cow_bitmap_addr, s->cow_bitmap_size);
210 close(s->fd);
211 }
213 static int cow_create(const char *filename, int64_t image_sectors,
214 const char *image_filename, int flags)
215 {
216 int fd, cow_fd;
217 struct cow_header_v2 cow_header;
218 struct stat st;
220 if (flags)
221 return -ENOTSUP;
223 cow_fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC | O_BINARY | O_LARGEFILE,
224 0644);
225 if (cow_fd < 0)
226 return -1;
227 memset(&cow_header, 0, sizeof(cow_header));
228 cow_header.magic = cpu_to_be32(COW_MAGIC);
229 cow_header.version = cpu_to_be32(COW_VERSION);
230 if (image_filename) {
231 fd = open(image_filename, O_RDONLY | O_BINARY);
232 if (fd < 0) {
233 close(cow_fd);
234 return -1;
235 }
236 if (fstat(fd, &st) != 0) {
237 close(fd);
238 return -1;
239 }
240 close(fd);
241 cow_header.mtime = cpu_to_be32(st.st_mtime);
242 realpath(image_filename, cow_header.backing_file);
243 }
244 cow_header.sectorsize = cpu_to_be32(512);
245 cow_header.size = cpu_to_be64(image_sectors * 512);
246 write(cow_fd, &cow_header, sizeof(cow_header));
247 /* resize to include at least all the bitmap */
248 ftruncate(cow_fd, sizeof(cow_header) + ((image_sectors + 7) >> 3));
249 close(cow_fd);
250 return 0;
251 }
253 BlockDriver bdrv_cow = {
254 "cow",
255 sizeof(BDRVCowState),
256 cow_probe,
257 cow_open,
258 cow_read,
259 cow_write,
260 cow_close,
261 cow_create,
262 cow_is_allocated,
263 };
264 #endif