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Sources/fstools/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 #ifndef GLOB_ONLYDIR
 34 #define GLOB_ONLYDIR 0x100
 35 #endif
 36 
 37 #define SWITCH_JFFS2 "/tmp/.switch_jffs2"
 38 #define OVERLAYDIR "/rom/overlay"
 39 
 40 static bool keep_sysupgrade;
 41 
 42 static int
 43 handle_rmdir(const char *dir)
 44 {
 45         struct dirent *dt;
 46         struct stat st;
 47         DIR *d;
 48         int fd;
 49 
 50         d = opendir(dir);
 51         if (!d)
 52                 return -1;
 53 
 54         fd = dirfd(d);
 55 
 56         while ((dt = readdir(d)) != NULL) {
 57                 if (fstatat(fd, dt->d_name, &st, AT_SYMLINK_NOFOLLOW) || S_ISDIR(st.st_mode))
 58                         continue;
 59 
 60                 if (keep_sysupgrade && !strcmp(dt->d_name, "sysupgrade.tgz"))
 61                         continue;
 62 
 63                 unlinkat(fd, dt->d_name, 0);
 64         }
 65 
 66         closedir(d);
 67         rmdir(dir);
 68 
 69         return 0;
 70 }
 71 
 72 void
 73 foreachdir(const char *dir, int (*cb)(const char*))
 74 {
 75         static char *globdir = NULL;
 76         static size_t globdirlen = 0;
 77         struct stat s = { 0 };
 78         size_t dirlen = strlen(dir);
 79         glob_t gl;
 80         int j;
 81 
 82         if (dirlen + sizeof("/*") > globdirlen) {
 83                 /* Alloc extra 256 B to avoid too many reallocs */
 84                 size_t len = dirlen + sizeof("/*") + 256;
 85                 char *tmp;
 86 
 87                 tmp = realloc(globdir, len);
 88                 if (!tmp)
 89                         return;
 90                 globdir = tmp;
 91                 globdirlen = len;
 92         }
 93 
 94         sprintf(globdir, "%s/*", dir);
 95 
 96         /* Include GLOB_MARK as callbacks expect a trailing slash */
 97         if (!glob(globdir, GLOB_NOESCAPE | GLOB_MARK | GLOB_ONLYDIR, NULL, &gl))
 98                 for (j = 0; j < gl.gl_pathc; j++) {
 99                         char *dir = gl.gl_pathv[j];
100                         int len = strlen(gl.gl_pathv[j]);
101                         int err;
102 
103                         /* Quick way of skipping files */
104                         if (dir[len - 1] != '/')
105                                 continue;
106 
107                         /* lstat needs path without a trailing slash */
108                         if (len > 1)
109                                 dir[len - 1] = '\0';
110                         err = lstat(gl.gl_pathv[j], &s);
111                         if (len > 1)
112                                 dir[len - 1] = '/';
113 
114                         if (!err && !S_ISLNK(s.st_mode))
115                                 foreachdir(gl.gl_pathv[j], cb);
116         }
117         cb(dir);
118 }
119 
120 static void foreach_mount(int (*cb)(const char *, const char *))
121 {
122         FILE *fp = fopen("/proc/mounts", "r");
123         static char line[256];
124 
125         if (!fp)
126                 return;
127 
128         while (fgets(line, sizeof(line), fp)) {
129                 char device[32], mount_point[32];
130 
131                 if (sscanf(line, "%31s %31s %*s %*s %*u %*u", device, mount_point) == 2)
132                         cb(device, mount_point);
133         }
134 
135         fclose(fp);
136 }
137 
138 void
139 overlay_delete(const char *dir, bool _keep_sysupgrade)
140 {
141         keep_sysupgrade = _keep_sysupgrade;
142         foreachdir(dir, handle_rmdir);
143 }
144 
145 static int
146 overlay_mount(struct volume *v, char *fs)
147 {
148         if (mkdir("/tmp/overlay", 0755)) {
149                 ULOG_ERR("failed to mkdir /tmp/overlay: %m\n");
150                 return -1;
151         }
152 
153         if (mount(v->blk, "/tmp/overlay", fs, MS_NOATIME, NULL)) {
154                 ULOG_ERR("failed to mount -t %s %s /tmp/overlay: %m\n", fs, v->blk);
155                 return -1;
156         }
157 
158         return 0;
159 }
160 
161 /**
162  * move_mount - move mount point to the new root
163  */
164 static int move_mount(const char *device, const char *mount_point)
165 {
166         static const char *prefix = "/tmp/root/";
167 
168         if (strncmp(mount_point, prefix, strlen(prefix)))
169                 return 0;
170 
171         return mount_move(prefix, "/", mount_point + strlen(prefix));
172 }
173 
174 static int
175 switch2jffs(struct volume *v)
176 {
177         struct stat s;
178         int ret, fd;
179 
180         if (!stat(SWITCH_JFFS2, &s)) {
181                 ULOG_ERR("jffs2 switch already running\n");
182                 return -1;
183         }
184 
185         fd = creat(SWITCH_JFFS2, 0600);
186         if (fd == -1) {
187                 ULOG_ERR("failed - cannot create jffs2 switch mark: %m\n");
188                 return -1;
189         }
190         close(fd);
191 
192         ret = mount(v->blk, OVERLAYDIR, "jffs2", MS_NOATIME, NULL);
193         unlink(SWITCH_JFFS2);
194         if (ret) {
195                 ULOG_ERR("failed - mount -t jffs2 %s %s: %m\n", v->blk, OVERLAYDIR);
196                 return -1;
197         }
198 
199         if (mount("none", "/", NULL, MS_NOATIME | MS_REMOUNT, 0)) {
200                 ULOG_ERR("failed - mount -o remount,ro none: %m\n");
201                 return -1;
202         }
203 
204         if (system("cp -a /tmp/root/* /rom/overlay")) {
205                 ULOG_ERR("failed - cp -a /tmp/root/* /rom/overlay: %m\n");
206                 return -1;
207         }
208 
209         if (pivot("/rom", "/mnt")) {
210                 ULOG_ERR("failed - pivot /rom /mnt: %m\n");
211                 return -1;
212         }
213 
214         if (mount_move("/mnt", "/tmp/root", "")) {
215                 ULOG_ERR("failed - mount -o move /mnt /tmp/root %m\n");
216                 return -1;
217         }
218 
219         ret = fopivot("/overlay", "/rom");
220 
221         /*
222          * Besides copying overlay data from "tmpfs" to "jffs2" we should also
223          * move mount points that user could create during JFFS2 formatting.
224          * This has to happen after fopivot call because:
225          * 1) It's trivial to find mount points to move then (/tmp/root/...).
226          * 2) We can't do that earlier using /rom/overlay/upper/ as overlay(fs)
227          *    doesn't support mounts. Mounting to upper dir don't make overlay
228          *    /propagate/ files to the target dir.
229          */
230         foreach_mount(move_mount);
231 
232         return ret;
233 }
234 
235 int
236 handle_whiteout(const char *dir)
237 {
238         struct stat s;
239         char link[256];
240         ssize_t sz;
241         struct dirent **namelist;
242         int n;
243 
244         n = scandir(dir, &namelist, NULL, NULL);
245 
246         if (n < 1)
247                 return -1;
248 
249         while (n--) {
250                 char file[256];
251 
252                 snprintf(file, sizeof(file), "%s%s", dir, namelist[n]->d_name);
253                 if (!lstat(file, &s) && S_ISLNK(s.st_mode)) {
254                         sz = readlink(file, link, sizeof(link) - 1);
255                         if (sz > 0) {
256                                 char *orig;
257 
258                                 link[sz] = '\0';
259                                 orig = strstr(&file[1], "/");
260                                 if (orig && !strcmp(link, "(overlay-whiteout)"))
261                                         unlink(orig);
262                         }
263                 }
264                 free(namelist[n]);
265         }
266         free(namelist);
267 
268         return 0;
269 }
270 
271 static char *overlay_fs_name(int type)
272 {
273         switch (type) {
274                 case FS_EXT4:
275                         return "ext4";
276                 case FS_F2FS:
277                         return "f2fs";
278                 case FS_UBIFS:
279                         return "ubifs";
280                 case FS_JFFS2:
281                 default:
282                         return "jffs2";
283         }
284 }
285 
286 int
287 jffs2_switch(struct volume *v)
288 {
289         char *mp, *fs_name;
290         int type;
291 
292         if (find_overlay_mount("overlayfs:/tmp/root"))
293                 return -1;
294 
295         if (find_filesystem("overlay")) {
296                 ULOG_ERR("overlayfs not supported by kernel\n");
297                 return -1;
298         }
299 
300         volume_init(v);
301         mp = find_mount_point(v->blk, 0);
302         if (mp) {
303                 ULOG_ERR("rootfs_data:%s is already mounted as %s\n", v->blk, mp);
304                 return -1;
305         }
306 
307         type = volume_identify(v);
308         fs_name = overlay_fs_name(type);
309 
310         switch (type) {
311         case FS_NONE:
312                 ULOG_ERR("no jffs2 marker found\n");
313                 /* fall through */
314 
315         case FS_DEADCODE:
316                 if (switch2jffs(v))
317                         return -1;
318 
319                 ULOG_INFO("performing overlay whiteout\n");
320                 umount2("/tmp/root", MNT_DETACH);
321                 foreachdir("/overlay/", handle_whiteout);
322 
323                 /* try hard to be in sync */
324                 ULOG_INFO("synchronizing overlay\n");
325                 if (system("cp -a /tmp/root/upper/* / 2>/dev/null"))
326                         ULOG_ERR("failed to sync jffs2 overlay\n");
327                 break;
328 
329         case FS_EXT4:
330         case FS_F2FS:
331         case FS_UBIFS:
332                 if (overlay_mount(v, fs_name))
333                         return -1;
334                 if (mount_move("/tmp", "", "/overlay") || fopivot("/overlay", "/rom")) {
335                         ULOG_ERR("switching to %s failed\n", fs_name);
336                         return -1;
337                 }
338                 break;
339         }
340 
341         sync();
342         fs_state_set("/overlay", FS_STATE_READY);
343         return 0;
344 }
345 
346 static int overlay_mount_fs(struct volume *v, const char *overlay_mp)
347 {
348         char *fstype = overlay_fs_name(volume_identify(v));
349 
350         if (mkdir(overlay_mp, 0755)) {
351                 ULOG_ERR("failed to mkdir /tmp/overlay: %m\n");
352                 return -1;
353         }
354 
355         if (mount(v->blk, overlay_mp, fstype,
356 #ifdef OVL_MOUNT_FULL_ACCESS_TIME
357                 MS_RELATIME,
358 #else
359                 MS_NOATIME,
360 #endif
361 #ifdef OVL_MOUNT_COMPRESS_ZLIB
362                 "compr=zlib"
363 #else
364                 NULL
365 #endif
366                 )) {
367                 ULOG_ERR("failed to mount -t %s %s /tmp/overlay: %m\n",
368                          fstype, v->blk);
369                 return -1;
370         }
371 
372         return 0;
373 }
374 
375 enum fs_state fs_state_get(const char *dir)
376 {
377         char *path;
378         char valstr[16];
379         uint32_t val;
380         ssize_t len;
381 
382         path = alloca(strlen(dir) + 1 + sizeof("/.fs_state"));
383         sprintf(path, "%s/.fs_state", dir);
384         len = readlink(path, valstr, sizeof(valstr) - 1);
385         if (len < 0)
386                 return FS_STATE_UNKNOWN;
387 
388         valstr[len] = 0;
389         val = atoi(valstr);
390 
391         if (val > __FS_STATE_LAST)
392                 return FS_STATE_UNKNOWN;
393 
394         return val;
395 }
396 
397 
398 int fs_state_set(const char *dir, enum fs_state state)
399 {
400         char valstr[16];
401         char *path;
402 
403         if (fs_state_get(dir) == state)
404                 return 0;
405 
406         path = alloca(strlen(dir) + 1 + sizeof("/.fs_state"));
407         sprintf(path, "%s/.fs_state", dir);
408         unlink(path);
409         snprintf(valstr, sizeof(valstr), "%d", state);
410 
411         return symlink(valstr, path);
412 }
413 
414 
415 int mount_overlay(struct volume *v)
416 {
417         const char *overlay_mp = "/tmp/overlay";
418         char *mp, *fs_name;
419         int err;
420 
421         if (!v)
422                 return -1;
423 
424         mp = find_mount_point(v->blk, 0);
425         if (mp) {
426                 ULOG_ERR("rootfs_data:%s is already mounted as %s\n", v->blk, mp);
427                 return -1;
428         }
429 
430         err = overlay_mount_fs(v, overlay_mp);
431         if (err)
432                 return err;
433 
434         /*
435          * Check for extroot config in overlay (rootfs_data) and if present then
436          * prefer it over rootfs_data.
437          */
438         if (!mount_extroot(overlay_mp)) {
439                 ULOG_INFO("switched to extroot\n");
440                 return 0;
441         }
442 
443         switch (fs_state_get(overlay_mp)) {
444         case FS_STATE_UNKNOWN:
445                 fs_state_set(overlay_mp, FS_STATE_PENDING);
446                 if (fs_state_get(overlay_mp) != FS_STATE_PENDING) {
447                         ULOG_ERR("unable to set filesystem state\n");
448                         break;
449                 }
450         case FS_STATE_PENDING:
451                 ULOG_INFO("overlay filesystem has not been fully initialized yet\n");
452                 overlay_delete(overlay_mp, true);
453                 break;
454         case FS_STATE_READY:
455                 break;
456         }
457 
458         fs_name = overlay_fs_name(volume_identify(v));
459         ULOG_INFO("switching to %s overlay\n", fs_name);
460         if (mount_move("/tmp", "", "/overlay") || fopivot("/overlay", "/rom")) {
461                 ULOG_ERR("switching to %s failed - fallback to ramoverlay\n", fs_name);
462                 return ramoverlay();
463         }
464 
465         return -1;
466 }
467 

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