libfstools/overlay.c

   1 /*
   2  * Copyright (C) 2014 John Crispin <blogic@openwrt.org>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU Lesser General Public License version 2.1
   6  * as published by the Free Software Foundation
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11  * GNU General Public License for more details.
  12  */
  13
  14 #include <sys/stat.h>
  15 #include <sys/types.h>
  16 #include <sys/mount.h>
  17
  18 #include <asm/byteorder.h>
  19
  20 #include <errno.h>
  21 #include <string.h>
  22 #include <stdio.h>
  23 #include <unistd.h>
  24 #include <stdlib.h>
  25 #include <glob.h>
  26 #include <errno.h>
  27 #include <dirent.h>
  28 #include <fcntl.h>
  29
  30 #include "libfstools.h"
  31 #include "volume.h"
  32
  33 #define SWITCH_JFFS2 "/tmp/.switch_jffs2"
  34
  35 static bool keep_sysupgrade;
  36
  37 static int
  38 handle_rmdir(const char *dir)
  39 {
  40         struct dirent *dt;
  41         struct stat st;
  42         DIR *d;
  43         int fd;
  44
  45         d = opendir(dir);
  46         if (!d)
  47                 return -1;
  48
  49         fd = dirfd(d);
  50
  51         while ((dt = readdir(d)) != NULL) {
  52                 if (fstatat(fd, dt->d_name, &st, AT_SYMLINK_NOFOLLOW) || S_ISDIR(st.st_mode))
  53                         continue;
  54
  55                 if (keep_sysupgrade && !strcmp(dt->d_name, "sysupgrade.tgz"))
  56                         continue;
  57
  58                 unlinkat(fd, dt->d_name, 0);
  59         }
  60
  61         closedir(d);
  62         rmdir(dir);
  63
  64         return 0;
  65 }
  66
  67 void
  68 foreachdir(const char *dir, int (*cb)(const char*))
  69 {
  70         static char *globdir = NULL;
  71         static size_t globdirlen = 0;
  72         struct stat s = { 0 };
  73         size_t dirlen = strlen(dir);
  74         glob_t gl;
  75         int j;
  76
  77         if (dirlen + sizeof("/*") > globdirlen) {
  78                 /* Alloc extra 256 B to avoid too many reallocs */
  79                 size_t len = dirlen + sizeof("/*") + 256;
  80                 char *tmp;
  81
  82                 tmp = realloc(globdir, len);
  83                 if (!tmp)
  84                         return;
  85                 globdir = tmp;
  86                 globdirlen = len;
  87         }
  88
  89         sprintf(globdir, "%s/*", dir);
  90
  91         /* Include GLOB_MARK as callbacks expect a trailing slash */
  92         if (!glob(globdir, GLOB_NOESCAPE | GLOB_MARK | GLOB_ONLYDIR, NULL, &gl))
  93                 for (j = 0; j < gl.gl_pathc; j++) {
  94                         char *dir = gl.gl_pathv[j];
  95                         int len = strlen(gl.gl_pathv[j]);
  96                         int err;
  97
  98                         /* Quick way of skipping files */
  99                         if (dir[len - 1] != '/')
 100                                 continue;
 101
 102                         /* lstat needs path without a trailing slash */
 103                         if (len > 1)
 104                                 dir[len - 1] = '\0';
 105                         err = lstat(gl.gl_pathv[j], &s);
 106                         if (len > 1)
 107                                 dir[len - 1] = '/';
 108
 109                         if (!err && !S_ISLNK(s.st_mode))
 110                                 foreachdir(gl.gl_pathv[j], cb);
 111         }
 112         cb(dir);
 113 }
 114
 115 static void foreach_mount(int (*cb)(const char *, const char *))
 116 {
 117         FILE *fp = fopen("/proc/mounts", "r");
 118         static char line[256];
 119
 120         if (!fp)
 121                 return;
 122
 123         while (fgets(line, sizeof(line), fp)) {
 124                 char device[32], mount_point[32];
 125
 126                 if (sscanf(line, "%31s %31s %*s %*s %*u %*u", device, mount_point) == 2)
 127                         cb(device, mount_point);
 128         }
 129
 130         fclose(fp);
 131 }
 132
 133 void
 134 overlay_delete(const char *dir, bool _keep_sysupgrade)
 135 {
 136         keep_sysupgrade = _keep_sysupgrade;
 137         foreachdir(dir, handle_rmdir);
 138 }
 139
 140 static int
 141 overlay_mount(struct volume *v, char *fs)
 142 {
 143         if (mkdir("/tmp/overlay", 0755)) {
 144                 ULOG_ERR("failed to mkdir /tmp/overlay: %m\n");
 145                 return -1;
 146         }
 147
 148         if (mount(v->blk, "/tmp/overlay", fs, MS_NOATIME, NULL)) {
 149                 ULOG_ERR("failed to mount -t %s %s /tmp/overlay: %m\n", fs, v->blk);
 150                 return -1;
 151         }
 152
 153         return 0;
 154 }
 155
 156 /**
 157  * move_mount - move mount point to the new root
 158  */
 159 static int move_mount(const char *device, const char *mount_point)
 160 {
 161         static const char *prefix = "/tmp/root/";
 162
 163         if (strncmp(mount_point, prefix, strlen(prefix)))
 164                 return 0;
 165
 166         return mount_move(prefix, "/", mount_point + strlen(prefix));
 167 }
 168
 169 static int
 170 switch2jffs(struct volume *v)
 171 {
 172         struct stat s;
 173         int ret;
 174
 175         if (!stat(SWITCH_JFFS2, &s)) {
 176                 ULOG_ERR("jffs2 switch already running\n");
 177                 return -1;
 178         }
 179
 180         creat("/tmp/.switch_jffs2", 0600);
 181         ret = mount(v->blk, "/rom/overlay", "jffs2", MS_NOATIME, NULL);
 182         unlink("/tmp/.switch_jffs2");
 183         if (ret) {
 184                 ULOG_ERR("failed - mount -t jffs2 %s /rom/overlay: %m\n", v->blk);
 185                 return -1;
 186         }
 187
 188         if (mount("none", "/", NULL, MS_NOATIME | MS_REMOUNT, 0)) {
 189                 ULOG_ERR("failed - mount -o remount,ro none: %m\n");
 190                 return -1;
 191         }
 192
 193         if (system("cp -a /tmp/root/* /rom/overlay")) {
 194                 ULOG_ERR("failed - cp -a /tmp/root/* /rom/overlay: %m\n");
 195                 return -1;
 196         }
 197
 198         if (pivot("/rom", "/mnt")) {
 199                 ULOG_ERR("failed - pivot /rom /mnt: %m\n");
 200                 return -1;
 201         }
 202
 203         if (mount_move("/mnt", "/tmp/root", "")) {
 204                 ULOG_ERR("failed - mount -o move /mnt /tmp/root %m\n");
 205                 return -1;
 206         }
 207
 208         ret = fopivot("/overlay", "/rom");
 209
 210         /*
 211          * Besides copying overlay data from "tmpfs" to "jffs2" we should also
 212          * move mount points that user could create during JFFS2 formatting.
 213          * This has to happen after fopivot call because:
 214          * 1) It's trivial to find mount points to move then (/tmp/root/...).
 215          * 2) We can't do that earlier using /rom/overlay/upper/ as overlay(fs)
 216          *    doesn't support mounts. Mounting to upper dir don't make overlay
 217          *    /propagate/ files to the target dir.
 218          */
 219         foreach_mount(move_mount);
 220
 221         return ret;
 222 }
 223
 224 int
 225 handle_whiteout(const char *dir)
 226 {
 227         struct stat s;
 228         char link[256];
 229         ssize_t sz;
 230         struct dirent **namelist;
 231         int n;
 232
 233         n = scandir(dir, &namelist, NULL, NULL);
 234
 235         if (n < 1)
 236                 return -1;
 237
 238         while (n--) {
 239                 char file[256];
 240
 241                 snprintf(file, sizeof(file), "%s%s", dir, namelist[n]->d_name);
 242                 if (!lstat(file, &s) && S_ISLNK(s.st_mode)) {
 243                         sz = readlink(file, link, sizeof(link) - 1);
 244                         if (sz > 0) {
 245                                 char *orig;
 246
 247                                 link[sz] = '\0';
 248                                 orig = strstr(&file[1], "/");
 249                                 if (orig && !strcmp(link, "(overlay-whiteout)"))
 250                                         unlink(orig);
 251                         }
 252                 }
 253                 free(namelist[n]);
 254         }
 255         free(namelist);
 256
 257         return 0;
 258 }
 259
 260 static char *overlay_fs_name(int type)
 261 {
 262         switch (type) {
 263                 case FS_EXT4:
 264                         return "ext4";
 265                 case FS_F2FS:
 266                         return "f2fs";
 267                 case FS_UBIFS:
 268                         return "ubifs";
 269                 case FS_JFFS2:
 270                 default:
 271                         return "jffs2";
 272         }
 273 }
 274
 275 int
 276 jffs2_switch(struct volume *v)
 277 {
 278         char *mp, *fs_name;
 279         int type;
 280
 281         if (find_overlay_mount("overlayfs:/tmp/root"))
 282                 return -1;
 283
 284         if (find_filesystem("overlay")) {
 285                 ULOG_ERR("overlayfs not supported by kernel\n");
 286                 return -1;
 287         }
 288
 289         volume_init(v);
 290         mp = find_mount_point(v->blk, 0);
 291         if (mp) {
 292                 ULOG_ERR("rootfs_data:%s is already mounted as %s\n", v->blk, mp);
 293                 return -1;
 294         }
 295
 296         type = volume_identify(v);
 297         fs_name = overlay_fs_name(type);
 298
 299         switch (type) {
 300         case FS_NONE:
 301                 ULOG_ERR("no jffs2 marker found\n");
 302                 /* fall through */
 303
 304         case FS_DEADCODE:
 305                 if (switch2jffs(v))
 306                         return -1;
 307
 308                 ULOG_INFO("performing overlay whiteout\n");
 309                 umount2("/tmp/root", MNT_DETACH);
 310                 foreachdir("/overlay/", handle_whiteout);
 311
 312                 /* try hard to be in sync */
 313                 ULOG_INFO("syncronizing overlay\n");
 314                 if (system("cp -a /tmp/root/upper/* / 2>/dev/null"))
 315                         ULOG_ERR("failed to sync jffs2 overlay\n");
 316                 break;
 317
 318         case FS_EXT4:
 319         case FS_F2FS:
 320         case FS_UBIFS:
 321                 if (overlay_mount(v, fs_name))
 322                         return -1;
 323                 if (mount_move("/tmp", "", "/overlay") || fopivot("/overlay", "/rom")) {
 324                         ULOG_ERR("switching to %s failed\n", fs_name);
 325                         return -1;
 326                 }
 327                 break;
 328         }
 329
 330         sync();
 331         fs_state_set("/overlay", FS_STATE_READY);
 332         return 0;
 333 }
 334
 335 static int overlay_mount_fs(struct volume *v)
 336 {
 337         char *fstype = overlay_fs_name(volume_identify(v));
 338
 339         if (mkdir("/tmp/overlay", 0755)) {
 340                 ULOG_ERR("failed to mkdir /tmp/overlay: %m\n");
 341                 return -1;
 342         }
 343
 344         if (mount(v->blk, "/tmp/overlay", fstype,
 345 #ifdef OVL_MOUNT_FULL_ACCESS_TIME
 346                 MS_RELATIME,
 347 #else
 348                 MS_NOATIME,
 349 #endif
 350 #ifdef OVL_MOUNT_COMPRESS_ZLIB
 351                 "compr=zlib"
 352 #else
 353                 NULL
 354 #endif
 355                 )) {
 356                 ULOG_ERR("failed to mount -t %s %s /tmp/overlay: %m\n",
 357                          fstype, v->blk);
 358                 return -1;
 359         }
 360
 361         return 0;
 362 }
 363
 364 enum fs_state fs_state_get(const char *dir)
 365 {
 366         char *path;
 367         char valstr[16];
 368         uint32_t val;
 369         ssize_t len;
 370
 371         path = alloca(strlen(dir) + 1 + sizeof("/.fs_state"));
 372         sprintf(path, "%s/.fs_state", dir);
 373         len = readlink(path, valstr, sizeof(valstr) - 1);
 374         if (len < 0)
 375                 return FS_STATE_UNKNOWN;
 376
 377         valstr[len] = 0;
 378         val = atoi(valstr);
 379
 380         if (val > __FS_STATE_LAST)
 381                 return FS_STATE_UNKNOWN;
 382
 383         return val;
 384 }
 385
 386
 387 int fs_state_set(const char *dir, enum fs_state state)
 388 {
 389         char valstr[16];
 390         char *path;
 391
 392         if (fs_state_get(dir) == state)
 393                 return 0;
 394
 395         path = alloca(strlen(dir) + 1 + sizeof("/.fs_state"));
 396         sprintf(path, "%s/.fs_state", dir);
 397         unlink(path);
 398         snprintf(valstr, sizeof(valstr), "%d", state);
 399
 400         return symlink(valstr, path);
 401 }
 402
 403
 404 int mount_overlay(struct volume *v)
 405 {
 406         char *mp, *fs_name;
 407
 408         if (!v)
 409                 return -1;
 410
 411         mp = find_mount_point(v->blk, 0);
 412         if (mp) {
 413                 ULOG_ERR("rootfs_data:%s is already mounted as %s\n", v->blk, mp);
 414                 return -1;
 415         }
 416
 417         overlay_mount_fs(v);
 418
 419         extroot_prefix = "/tmp/overlay";
 420         if (!mount_extroot()) {
 421                 ULOG_INFO("switched to extroot\n");
 422                 return 0;
 423         }
 424
 425         switch(fs_state_get("/tmp/overlay")) {
 426         case FS_STATE_UNKNOWN:
 427                 fs_state_set("/tmp/overlay", FS_STATE_PENDING);
 428                 if (fs_state_get("/tmp/overlay") != FS_STATE_PENDING) {
 429                         ULOG_ERR("unable to set filesystem state\n");
 430                         break;
 431                 }
 432         case FS_STATE_PENDING:
 433                 ULOG_INFO("overlay filesystem has not been fully initialized yet\n");
 434                 overlay_delete("/tmp/overlay", true);
 435                 break;
 436         case FS_STATE_READY:
 437                 break;
 438         }
 439
 440         fs_name = overlay_fs_name(volume_identify(v));
 441         ULOG_INFO("switching to %s overlay\n", fs_name);
 442         if (mount_move("/tmp", "", "/overlay") || fopivot("/overlay", "/rom")) {
 443                 ULOG_ERR("switching to %s failed - fallback to ramoverlay\n", fs_name);
 444                 return ramoverlay();
 445         }
 446
 447         return -1;
 448 }