block.c

   1 /*
   2  * QEMU System Emulator block driver
   3  *
   4  * Copyright (c) 2003 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 #include <stdlib.h>
  25 #include <stdio.h>
  26 #include <stdarg.h>
  27 #include <string.h>
  28 #include <getopt.h>
  29 #include <inttypes.h>
  30 #include <unistd.h>
  31 #include <sys/mman.h>
  32 #include <fcntl.h>
  33 #include <signal.h>
  34 #include <time.h>
  35 #include <sys/time.h>
  36 #include <malloc.h>
  37 #include <termios.h>
  38 #include <sys/poll.h>
  39 #include <errno.h>
  40 #include <sys/wait.h>
  41 #include <netinet/in.h>
  42
  43 #include "vl.h"
  44
  45 #define NO_THUNK_TYPE_SIZE
  46 #include "thunk.h"
  47
  48 struct BlockDriverState {
  49     int fd; /* if -1, only COW mappings */
  50     int64_t total_sectors;
  51     int read_only;
  52
  53     uint8_t *cow_bitmap; /* if non NULL, COW mappings are used first */
  54     uint8_t *cow_bitmap_addr; /* mmap address of cow_bitmap */
  55     int cow_bitmap_size;
  56     int cow_fd;
  57     int64_t cow_sectors_offset;
  58     char filename[1024];
  59 };
  60
  61 BlockDriverState *bdrv_open(const char *filename, int snapshot)
  62 {
  63     BlockDriverState *bs;
  64     int fd, cow_fd;
  65     int64_t size;
  66     char template[] = "/tmp/vl.XXXXXX";
  67     struct cow_header_v2 cow_header;
  68     struct stat st;
  69
  70     bs = malloc(sizeof(BlockDriverState));
  71     if(!bs)
  72         return NULL;
  73     bs->read_only = 0;
  74     bs->fd = -1;
  75     bs->cow_fd = -1;
  76     bs->cow_bitmap = NULL;
  77     strcpy(bs->filename, filename);
  78
  79     /* open standard HD image */
  80     fd = open(filename, O_RDWR | O_LARGEFILE);
  81     if (fd < 0) {
  82         /* read only image on disk */
  83         fd = open(filename, O_RDONLY | O_LARGEFILE);
  84         if (fd < 0) {
  85             perror(filename);
  86             goto fail;
  87         }
  88         if (!snapshot)
  89             bs->read_only = 1;
  90     }
  91     bs->fd = fd;
  92
  93     /* see if it is a cow image */
  94     if (read(fd, &cow_header, sizeof(cow_header)) != sizeof(cow_header)) {
  95         fprintf(stderr, "%s: could not read header\n", filename);
  96         goto fail;
  97     }
  98     if (cow_header.magic == htonl(COW_MAGIC) &&
  99         cow_header.version == htonl(COW_VERSION)) {
 100         /* cow image found */
 101         size = cow_header.size;
 102 #ifndef WORDS_BIGENDIAN
 103         size = bswap64(size);
 104 #endif
 105         bs->total_sectors = size / 512;
 106
 107         bs->cow_fd = fd;
 108         bs->fd = -1;
 109         if (cow_header.backing_file[0] != '\0') {
 110             if (stat(cow_header.backing_file, &st) != 0) {
 111                 fprintf(stderr, "%s: could not find original disk image '%s'\n", filename, cow_header.backing_file);
 112                 goto fail;
 113             }
 114             if (st.st_mtime != htonl(cow_header.mtime)) {
 115                 fprintf(stderr, "%s: original raw disk image '%s' does not match saved timestamp\n", filename, cow_header.backing_file);
 116                 goto fail;
 117             }
 118             fd = open(cow_header.backing_file, O_RDONLY | O_LARGEFILE);
 119             if (fd < 0)
 120                 goto fail;
 121             bs->fd = fd;
 122         }
 123         /* mmap the bitmap */
 124         bs->cow_bitmap_size = ((bs->total_sectors + 7) >> 3) + sizeof(cow_header);
 125         bs->cow_bitmap_addr = mmap(get_mmap_addr(bs->cow_bitmap_size),
 126                                    bs->cow_bitmap_size,
 127                                    PROT_READ | PROT_WRITE,
 128                                    MAP_SHARED, bs->cow_fd, 0);
 129         if (bs->cow_bitmap_addr == MAP_FAILED)
 130             goto fail;
 131         bs->cow_bitmap = bs->cow_bitmap_addr + sizeof(cow_header);
 132         bs->cow_sectors_offset = (bs->cow_bitmap_size + 511) & ~511;
 133         snapshot = 0;
 134     } else {
 135         /* standard raw image */
 136         size = lseek64(fd, 0, SEEK_END);
 137         bs->total_sectors = size / 512;
 138         bs->fd = fd;
 139     }
 140
 141     if (snapshot) {
 142         /* create a temporary COW file */
 143         cow_fd = mkstemp(template);
 144         if (cow_fd < 0)
 145             goto fail;
 146         bs->cow_fd = cow_fd;
 147         unlink(template);
 148
 149         /* just need to allocate bitmap */
 150         bs->cow_bitmap_size = (bs->total_sectors + 7) >> 3;
 151         bs->cow_bitmap_addr = mmap(get_mmap_addr(bs->cow_bitmap_size),
 152                                    bs->cow_bitmap_size,
 153                                    PROT_READ | PROT_WRITE,
 154                                    MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
 155         if (bs->cow_bitmap_addr == MAP_FAILED)
 156             goto fail;
 157         bs->cow_bitmap = bs->cow_bitmap_addr;
 158         bs->cow_sectors_offset = 0;
 159     }
 160
 161     return bs;
 162  fail:
 163     bdrv_close(bs);
 164     return NULL;
 165 }
 166
 167 void bdrv_close(BlockDriverState *bs)
 168 {
 169     /* we unmap the mapping so that it is written to the COW file */
 170     if (bs->cow_bitmap_addr)
 171         munmap(bs->cow_bitmap_addr, bs->cow_bitmap_size);
 172     if (bs->cow_fd >= 0)
 173         close(bs->cow_fd);
 174     if (bs->fd >= 0)
 175         close(bs->fd);
 176     free(bs);
 177 }
 178
 179 static inline void set_bit(uint8_t *bitmap, int64_t bitnum)
 180 {
 181     bitmap[bitnum / 8] |= (1 << (bitnum%8));
 182 }
 183
 184 static inline int is_bit_set(const uint8_t *bitmap, int64_t bitnum)
 185 {
 186     return !!(bitmap[bitnum / 8] & (1 << (bitnum%8)));
 187 }
 188
 189
 190 /* Return true if first block has been changed (ie. current version is
 191  * in COW file).  Set the number of continuous blocks for which that
 192  * is true. */
 193 static int is_changed(uint8_t *bitmap,
 194                       int64_t sector_num, int nb_sectors,
 195                       int *num_same)
 196 {
 197     int changed;
 198
 199     if (!bitmap || nb_sectors == 0) {
 200         *num_same = nb_sectors;
 201         return 0;
 202     }
 203
 204     changed = is_bit_set(bitmap, sector_num);
 205     for (*num_same = 1; *num_same < nb_sectors; (*num_same)++) {
 206         if (is_bit_set(bitmap, sector_num + *num_same) != changed)
 207             break;
 208     }
 209
 210     return changed;
 211 }
 212
 213 /* commit COW file into the raw image */
 214 int bdrv_commit(BlockDriverState *bs)
 215 {
 216     int64_t i;
 217     uint8_t *cow_bitmap;
 218
 219     if (!bs->cow_bitmap) {
 220         fprintf(stderr, "Already committed to %s\n", bs->filename);
 221         return 0;
 222     }
 223
 224     if (bs->read_only) {
 225         fprintf(stderr, "Can't commit to %s: read-only\n", bs->filename);
 226         return -1;
 227     }
 228
 229     cow_bitmap = bs->cow_bitmap;
 230     for (i = 0; i < bs->total_sectors; i++) {
 231         if (is_bit_set(cow_bitmap, i)) {
 232             unsigned char sector[512];
 233             if (bdrv_read(bs, i, sector, 1) != 0) {
 234                 fprintf(stderr, "Error reading sector %lli: aborting commit\n",
 235                         (long long)i);
 236                 return -1;
 237             }
 238
 239             /* Make bdrv_write write to real file for a moment. */
 240             bs->cow_bitmap = NULL;
 241             if (bdrv_write(bs, i, sector, 1) != 0) {
 242                 fprintf(stderr, "Error writing sector %lli: aborting commit\n",
 243                         (long long)i);
 244                 bs->cow_bitmap = cow_bitmap;
 245                 return -1;
 246             }
 247             bs->cow_bitmap = cow_bitmap;
 248         }
 249     }
 250     fprintf(stderr, "Committed snapshot to %s\n", bs->filename);
 251     return 0;
 252 }
 253
 254 /* return -1 if error */
 255 int bdrv_read(BlockDriverState *bs, int64_t sector_num,
 256               uint8_t *buf, int nb_sectors)
 257 {
 258     int ret, n, fd;
 259     int64_t offset;
 260
 261     while (nb_sectors > 0) {
 262         if (is_changed(bs->cow_bitmap, sector_num, nb_sectors, &n)) {
 263             fd = bs->cow_fd;
 264             offset = bs->cow_sectors_offset;
 265         } else {
 266             fd = bs->fd;
 267             offset = 0;
 268         }
 269
 270         if (fd < 0) {
 271             /* no file, just return empty sectors */
 272             memset(buf, 0, n * 512);
 273         } else {
 274             offset += sector_num * 512;
 275             lseek64(fd, offset, SEEK_SET);
 276             ret = read(fd, buf, n * 512);
 277             if (ret != n * 512) {
 278                 return -1;
 279             }
 280         }
 281         nb_sectors -= n;
 282         sector_num += n;
 283         buf += n * 512;
 284     }
 285     return 0;
 286 }
 287
 288 /* return -1 if error */
 289 int bdrv_write(BlockDriverState *bs, int64_t sector_num,
 290                const uint8_t *buf, int nb_sectors)
 291 {
 292     int ret, fd, i;
 293     int64_t offset, retl;
 294
 295     if (bs->read_only)
 296         return -1;
 297
 298     if (bs->cow_bitmap) {
 299         fd = bs->cow_fd;
 300         offset = bs->cow_sectors_offset;
 301     } else {
 302         fd = bs->fd;
 303         offset = 0;
 304     }
 305
 306     offset += sector_num * 512;
 307     retl = lseek64(fd, offset, SEEK_SET);
 308     if (retl == -1) {
 309         return -1;
 310     }
 311     ret = write(fd, buf, nb_sectors * 512);
 312     if (ret != nb_sectors * 512) {
 313         return -1;
 314     }
 315
 316     if (bs->cow_bitmap) {
 317         for (i = 0; i < nb_sectors; i++)
 318             set_bit(bs->cow_bitmap, sector_num + i);
 319     }
 320     return 0;
 321 }
 322
 323 void bdrv_get_geometry(BlockDriverState *bs, int64_t *nb_sectors_ptr)
 324 {
 325     *nb_sectors_ptr = bs->total_sectors;
 326 }