* 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>
> ---
> 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);
> +}
> +
> /*
> * 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;
Wouldnt it be *much* simpler to add it as a magic1 variant:
#define LINUX_REBOOT_UMOUNT_RO 0xfee1deaf
Used as a 'also remount ro please' flag?
That way the whole patch would literally be 2 lines:
if (magic1 == LINUX_REBOOT_UMOUNT_RO)
emergency_remount_synchronous();
Note that this also has the advantage that both kexec and suspend reboots could be
done with emergency umounts, if so desired - and any future reboot variant would be
supported as well. Your patch left out those other reboot methods.
Thanks,
Ingo
--
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
