Re: [PATCH] Syscalls: reboot: Add options to the reboot syscall toremount filesystems ro

[Dave Young]

On Thu, Mar 3, 2011 at 4:46 PM, Dave Young <hidave.darkstar@xxxxxxxxx> wrote:
> On Thu, Mar 3, 2011 at 3:31 PM, Ken Sumrall <ksumrall@xxxxxxxxxxx> 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@xxxxxxxxxxx>
>> ---
>> Âfs/super.c       |  Â9 +++++++++
>> Âinclude/linux/fs.h   |  Â1 +
>> Âinclude/linux/reboot.h | Â Â4 ++++
>> Âkernel/sys.c      |  12 ++++++++++++
>> Â4 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)
>> Â Â Â Â}
>> Â}
>>
>> +void emergency_remount_synchronous(void)
>> +{
>> + Â Â Â struct work_struct *work;
>> +
>> + Â Â Â work = kmalloc(sizeof(*work), GFP_ATOMIC);
>> + Â Â Â if (work)
>> + Â Â Â Â Â Â Â do_emergency_remount(work);
>
> work is not needed here? just call do_mergency_remount()

fix above comment: still need a null pointer

>
>> +}
>> +
>> Â/*
>> Â* Unnamed block devices are dummy devices used by virtual
>> Â* filesystems which don't use real block-devices. Â-- 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);
>> Âextern void sync_supers(void);
>> Âextern void emergency_sync(void);
>> Âextern void emergency_remount(void);
>> +extern void emergency_remount_synchronous(void);
>> Â#ifdef CONFIG_BLOCK
>> Âextern sector_t bmap(struct inode *, sector_t);
>> Â#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 @@
>> Â*/
>>
>> Â#define    ÂLINUX_REBOOT_CMD_RESTART    Â0x01234567
>> +#define    ÂLINUX_REBOOT_CMD_RMNT_RESTART  0x12345670
>> Â#define    ÂLINUX_REBOOT_CMD_HALT      0xCDEF0123
>> +#define    ÂLINUX_REBOOT_CMD_RMNT_HALT   Â0xDEF0123C
>> Â#define    ÂLINUX_REBOOT_CMD_CAD_ON     0x89ABCDEF
>> Â#define    ÂLINUX_REBOOT_CMD_CAD_OFF    Â0x00000000
>> Â#define    ÂLINUX_REBOOT_CMD_POWER_OFF   Â0x4321FEDC
>> +#define    ÂLINUX_REBOOT_CMD_RMNT_POWER_OFF 0x321FEDC4
>> Â#define    ÂLINUX_REBOOT_CMD_RESTART2    0xA1B2C3D4
>> +#define    ÂLINUX_REBOOT_CMD_RMNT_RESTART2 Â0x1B2C3D4A
>> Â#define    ÂLINUX_REBOOT_CMD_SW_SUSPEND   0xD000FCE2
>> Â#define    ÂLINUX_REBOOT_CMD_KEXEC     Â0x45584543
>>
>> 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,
>> Â Â Â Âmutex_lock(&reboot_mutex);
>> Â Â Â Âswitch (cmd) {
>> Â Â Â Âcase LINUX_REBOOT_CMD_RESTART:
>> + Â Â Â case LINUX_REBOOT_CMD_RMNT_RESTART:
>> + Â Â Â Â Â Â Â if (cmd == LINUX_REBOOT_CMD_RMNT_RESTART)
>> + Â Â Â Â Â Â Â Â Â Â Â emergency_remount_synchronous();
>> Â Â Â Â Â Â Â Âkernel_restart(NULL);
>> Â Â Â Â Â Â Â Âbreak;
>>
>> @@ -404,22 +407,31 @@ SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd,
>> Â Â Â Â Â Â Â Âbreak;
>>
>> Â Â Â Âcase LINUX_REBOOT_CMD_HALT:
>> + Â Â Â case LINUX_REBOOT_CMD_RMNT_HALT:
>> + Â Â Â Â Â Â Â if (cmd == LINUX_REBOOT_CMD_RMNT_HALT)
>> + Â Â Â Â Â Â Â Â Â Â Â emergency_remount_synchronous();
>> Â Â Â Â Â Â Â Âkernel_halt();
>> Â Â Â Â Â Â Â Âdo_exit(0);
>> Â Â Â Â Â Â Â Âpanic("cannot halt");
>>
>> Â Â Â Âcase LINUX_REBOOT_CMD_POWER_OFF:
>> + Â Â Â case LINUX_REBOOT_CMD_RMNT_POWER_OFF:
>> + Â Â Â Â Â Â Â if (cmd == LINUX_REBOOT_CMD_RMNT_POWER_OFF)
>> + Â Â Â Â Â Â Â Â Â Â Â emergency_remount_synchronous();
>> Â Â Â Â Â Â Â Âkernel_power_off();
>> Â Â Â Â Â Â Â Âdo_exit(0);
>> Â Â Â Â Â Â Â Âbreak;
>>
>> Â Â Â Âcase LINUX_REBOOT_CMD_RESTART2:
>> + Â Â Â case LINUX_REBOOT_CMD_RMNT_RESTART2:
>> Â Â Â Â Â Â Â Âif (strncpy_from_user(&buffer[0], arg, sizeof(buffer) - 1) < 0) {
>> Â Â Â Â Â Â Â Â Â Â Â Âret = -EFAULT;
>> Â Â Â Â Â Â Â Â Â Â Â Âbreak;
>> Â Â Â Â Â Â Â Â}
>> Â Â Â Â Â Â Â Âbuffer[sizeof(buffer) - 1] = '\0';
>>
>> + Â Â Â Â Â Â Â if (cmd == LINUX_REBOOT_CMD_RMNT_RESTART2)
>> + Â Â Â Â Â Â Â Â Â Â Â emergency_remount_synchronous();
>> Â Â Â Â Â Â Â Âkernel_restart(buffer);
>> Â Â Â Â Â Â Â Âbreak;
>>
>> --
>> 1.7.3.1
>>
>>
>
>
>
> --
> Regards
> dave
>



-- 
Regards
dave
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