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Try to unmount writable filesystems when rebooting
Ext4 filesystems like to be unmounted before rebooting. The Android system doesn't have a traditional Linux init setup, and shutting down the system was not much more than calling sync(2) and reboot(2). This adds a new function to libcutils called android_reboot(). By default, it calls sync() and then remounts all writable filesystems as read-only and marks them clean. There is a flag parameter in which the caller can ask for sync() not to be called, or to not remount the filesystems as read-only. Then it will call reboot(2) as directed by the other parameters. This change also updates adb, init and toolbox to call the new android_reboot() function. Fixes bugs 3350709 and 3495575. Change-Id: I16d71ffce3134310d7a260f61ec6f4dd204124a7
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Ken Sumrall
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Mar 11, 2011
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,35 @@ | ||
| /* | ||
| * Copyright 2011, The Android Open Source Project | ||
| * | ||
| * Licensed under the Apache License, Version 2.0 (the "License"); | ||
| * you may not use this file except in compliance with the License. | ||
| * You may obtain a copy of the License at | ||
| * | ||
| * http://www.apache.org/licenses/LICENSE-2.0 | ||
| * | ||
| * Unless required by applicable law or agreed to in writing, software | ||
| * distributed under the License is distributed on an "AS IS" BASIS, | ||
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| * See the License for the specific language governing permissions and | ||
| * limitations under the License. | ||
| */ | ||
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| #ifndef __CUTILS_ANDROID_REBOOT_H__ | ||
| #define __CUTILS_ANDROID_REBOOT_H__ | ||
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| __BEGIN_DECLS | ||
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| /* Commands */ | ||
| #define ANDROID_RB_RESTART 0xDEAD0001 | ||
| #define ANDROID_RB_POWEROFF 0xDEAD0002 | ||
| #define ANDROID_RB_RESTART2 0xDEAD0003 | ||
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| /* Flags */ | ||
| #define ANDROID_RB_FLAG_NO_SYNC 0x1 | ||
| #define ANDROID_RB_FLAG_NO_REMOUNT_RO 0x2 | ||
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| int android_reboot(int cmd, int flags, char *arg); | ||
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| __END_DECLS | ||
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| #endif /* __CUTILS_ANDROID_REBOOT_H__ */ |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,134 @@ | ||
| /* | ||
| * Copyright 2011, The Android Open Source Project | ||
| * | ||
| * Licensed under the Apache License, Version 2.0 (the "License"); | ||
| * you may not use this file except in compliance with the License. | ||
| * You may obtain a copy of the License at | ||
| * | ||
| * http://www.apache.org/licenses/LICENSE-2.0 | ||
| * | ||
| * Unless required by applicable law or agreed to in writing, software | ||
| * distributed under the License is distributed on an "AS IS" BASIS, | ||
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| * See the License for the specific language governing permissions and | ||
| * limitations under the License. | ||
| */ | ||
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| #include <unistd.h> | ||
| #include <sys/reboot.h> | ||
| #include <sys/types.h> | ||
| #include <sys/stat.h> | ||
| #include <fcntl.h> | ||
| #include <stdio.h> | ||
| #include <string.h> | ||
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| #include <cutils/android_reboot.h> | ||
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| /* Check to see if /proc/mounts contains any writeable filesystems | ||
| * backed by a block device. | ||
| * Return true if none found, else return false. | ||
| */ | ||
| static int remount_ro_done(void) | ||
| { | ||
| FILE *f; | ||
| char mount_dev[256]; | ||
| char mount_dir[256]; | ||
| char mount_type[256]; | ||
| char mount_opts[256]; | ||
| int mount_freq; | ||
| int mount_passno; | ||
| int match; | ||
| int found_rw_fs = 0; | ||
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| f = fopen("/proc/mounts", "r"); | ||
| if (! f) { | ||
| /* If we can't read /proc/mounts, just give up */ | ||
| return 1; | ||
| } | ||
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| do { | ||
| match = fscanf(f, "%255s %255s %255s %255s %d %d\n", | ||
| mount_dev, mount_dir, mount_type, | ||
| mount_opts, &mount_freq, &mount_passno); | ||
| mount_dev[255] = 0; | ||
| mount_dir[255] = 0; | ||
| mount_type[255] = 0; | ||
| mount_opts[255] = 0; | ||
| if ((match == 6) && !strncmp(mount_dev, "/dev/block", 10) && strstr(mount_opts, "rw")) { | ||
| found_rw_fs = 1; | ||
| break; | ||
| } | ||
| } while (match != EOF); | ||
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| fclose(f); | ||
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| return !found_rw_fs; | ||
| } | ||
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| /* Remounting filesystems read-only is difficult when there are files | ||
| * opened for writing or pending deletes on the filesystem. There is | ||
| * no way to force the remount with the mount(2) syscall. The magic sysrq | ||
| * 'u' command does an emergency remount read-only on all writable filesystems | ||
| * that have a block device (i.e. not tmpfs filesystems) by calling | ||
| * emergency_remount(), which knows how to force the remount to read-only. | ||
| * Unfortunately, that is asynchronous, and just schedules the work and | ||
| * returns. The best way to determine if it is done is to read /proc/mounts | ||
| * repeatedly until there are no more writable filesystems mounted on | ||
| * block devices. | ||
| */ | ||
| static void remount_ro(void) | ||
| { | ||
| int fd, cnt = 0; | ||
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| /* Trigger the remount of the filesystems as read-only, | ||
| * which also marks them clean. | ||
| */ | ||
| fd = open("/proc/sysrq-trigger", O_WRONLY); | ||
| if (fd < 0) { | ||
| return; | ||
| } | ||
| write(fd, "u", 1); | ||
| close(fd); | ||
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| /* Now poll /proc/mounts till it's done */ | ||
| while (!remount_ro_done() && (cnt < 50)) { | ||
| usleep(100000); | ||
| cnt++; | ||
| } | ||
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| return; | ||
| } | ||
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| int android_reboot(int cmd, int flags, char *arg) | ||
| { | ||
| int ret; | ||
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| if (!(flags & ANDROID_RB_FLAG_NO_SYNC)) | ||
| sync(); | ||
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| if (!(flags & ANDROID_RB_FLAG_NO_REMOUNT_RO)) | ||
| remount_ro(); | ||
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| switch (cmd) { | ||
| case ANDROID_RB_RESTART: | ||
| ret = reboot(RB_AUTOBOOT); | ||
| break; | ||
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| case ANDROID_RB_POWEROFF: | ||
| ret = reboot(RB_POWER_OFF); | ||
| break; | ||
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| case ANDROID_RB_RESTART2: | ||
| ret = __reboot(LINUX_REBOOT_MAGIC1, LINUX_REBOOT_MAGIC2, | ||
| LINUX_REBOOT_CMD_RESTART2, arg); | ||
| break; | ||
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| default: | ||
| ret = -1; | ||
| } | ||
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| return ret; | ||
| } | ||
|
|
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