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SubjectRe: [PATCH] Syscalls: reboot: Add options to the reboot syscall to remount filesystems ro
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On Thu, Mar 3, 2011 at 4:46 PM, Dave Young <hidave.darkstar@gmail.com> wrote:
> On Thu, Mar 3, 2011 at 3:31 PM, Ken Sumrall <ksumrall@android.com> wrote:
>> Add 4 new commands to the reboot system call, that do the same thing as the
>> RESTART, HALT, POWER_OFF, and RESTART2 commands, but also remount writable
>> filesystems as read-only just before doing what the command normally does.
>> Now that Android is using EXT4, and since we don't have a standard init
>> setup to unmount filesystems before rebooting, this allows the system to
>> reboot with clean filesystems, and also improves boot time as the journal
>> does not need to be replayed when mounting the filesystem.
>>
>> Signed-off-by: Ken Sumrall <ksumrall@android.com>
>> ---
>>  fs/super.c             |    9 +++++++++
>>  include/linux/fs.h     |    1 +
>>  include/linux/reboot.h |    4 ++++
>>  kernel/sys.c           |   12 ++++++++++++
>>  4 files changed, 26 insertions(+), 0 deletions(-)
>>
>> diff --git a/fs/super.c b/fs/super.c
>> index 8819e3a..3f39a16 100644
>> --- a/fs/super.c
>> +++ b/fs/super.c
>> @@ -638,6 +638,15 @@ void emergency_remount(void)
>>        }
>>  }
>>
>> +void emergency_remount_synchronous(void)
>> +{
>> +       struct work_struct *work;
>> +
>> +       work = kmalloc(sizeof(*work), GFP_ATOMIC);
>> +       if (work)
>> +               do_emergency_remount(work);
>
> work is not needed here? just call do_mergency_remount()

fix above comment: still need a null pointer

>
>> +}
>> +
>>  /*
>>  * Unnamed block devices are dummy devices used by virtual
>>  * filesystems which don't use real block-devices.  -- jrs
>> diff --git a/include/linux/fs.h b/include/linux/fs.h
>> index 63d069b..e48ef0d 100644
>> --- a/include/linux/fs.h
>> +++ b/include/linux/fs.h
>> @@ -2110,6 +2110,7 @@ extern int generic_write_sync(struct file *file, loff_t pos, loff_t count);
>>  extern void sync_supers(void);
>>  extern void emergency_sync(void);
>>  extern void emergency_remount(void);
>> +extern void emergency_remount_synchronous(void);
>>  #ifdef CONFIG_BLOCK
>>  extern sector_t bmap(struct inode *, sector_t);
>>  #endif
>> diff --git a/include/linux/reboot.h b/include/linux/reboot.h
>> index 3005d5a..24b185d 100644
>> --- a/include/linux/reboot.h
>> +++ b/include/linux/reboot.h
>> @@ -26,11 +26,15 @@
>>  */
>>
>>  #define        LINUX_REBOOT_CMD_RESTART        0x01234567
>> +#define        LINUX_REBOOT_CMD_RMNT_RESTART   0x12345670
>>  #define        LINUX_REBOOT_CMD_HALT           0xCDEF0123
>> +#define        LINUX_REBOOT_CMD_RMNT_HALT      0xDEF0123C
>>  #define        LINUX_REBOOT_CMD_CAD_ON         0x89ABCDEF
>>  #define        LINUX_REBOOT_CMD_CAD_OFF        0x00000000
>>  #define        LINUX_REBOOT_CMD_POWER_OFF      0x4321FEDC
>> +#define        LINUX_REBOOT_CMD_RMNT_POWER_OFF 0x321FEDC4
>>  #define        LINUX_REBOOT_CMD_RESTART2       0xA1B2C3D4
>> +#define        LINUX_REBOOT_CMD_RMNT_RESTART2  0x1B2C3D4A
>>  #define        LINUX_REBOOT_CMD_SW_SUSPEND     0xD000FCE2
>>  #define        LINUX_REBOOT_CMD_KEXEC          0x45584543
>>
>> diff --git a/kernel/sys.c b/kernel/sys.c
>> index 7f5a0cd..3f474e6 100644
>> --- a/kernel/sys.c
>> +++ b/kernel/sys.c
>> @@ -392,6 +392,9 @@ SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd,
>>        mutex_lock(&reboot_mutex);
>>        switch (cmd) {
>>        case LINUX_REBOOT_CMD_RESTART:
>> +       case LINUX_REBOOT_CMD_RMNT_RESTART:
>> +               if (cmd == LINUX_REBOOT_CMD_RMNT_RESTART)
>> +                       emergency_remount_synchronous();
>>                kernel_restart(NULL);
>>                break;
>>
>> @@ -404,22 +407,31 @@ SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd,
>>                break;
>>
>>        case LINUX_REBOOT_CMD_HALT:
>> +       case LINUX_REBOOT_CMD_RMNT_HALT:
>> +               if (cmd == LINUX_REBOOT_CMD_RMNT_HALT)
>> +                       emergency_remount_synchronous();
>>                kernel_halt();
>>                do_exit(0);
>>                panic("cannot halt");
>>
>>        case LINUX_REBOOT_CMD_POWER_OFF:
>> +       case LINUX_REBOOT_CMD_RMNT_POWER_OFF:
>> +               if (cmd == LINUX_REBOOT_CMD_RMNT_POWER_OFF)
>> +                       emergency_remount_synchronous();
>>                kernel_power_off();
>>                do_exit(0);
>>                break;
>>
>>        case LINUX_REBOOT_CMD_RESTART2:
>> +       case LINUX_REBOOT_CMD_RMNT_RESTART2:
>>                if (strncpy_from_user(&buffer[0], arg, sizeof(buffer) - 1) < 0) {
>>                        ret = -EFAULT;
>>                        break;
>>                }
>>                buffer[sizeof(buffer) - 1] = '\0';
>>
>> +               if (cmd == LINUX_REBOOT_CMD_RMNT_RESTART2)
>> +                       emergency_remount_synchronous();
>>                kernel_restart(buffer);
>>                break;
>>
>> --
>> 1.7.3.1
>>
>>
>
>
>
> --
> Regards
> dave
>



--
Regards
dave
--
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