Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757458Ab1CCITH (ORCPT ); Thu, 3 Mar 2011 03:19:07 -0500 Received: from mx3.mail.elte.hu ([157.181.1.138]:55215 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756310Ab1CCITE (ORCPT ); Thu, 3 Mar 2011 03:19:04 -0500 Date: Thu, 3 Mar 2011 09:18:41 +0100 From: Ingo Molnar To: Ken Sumrall , Linus Torvalds Cc: linux-kernel@vger.kernel.org, Alexander Viro , Christoph Hellwig , Andrew Morton , Jan Kara , Jens Axboe , Matthew Wilcox , Eric Paris , Dave Young , Jiri Slaby , James Morris , linux-fsdevel@vger.kernel.org Subject: Re: [PATCH] Syscalls: reboot: Add options to the reboot syscall to remount filesystems ro Message-ID: <20110303081841.GA14854@elte.hu> References: <1299137483-10975-1-git-send-email-ksumrall@android.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1299137483-10975-1-git-send-email-ksumrall@android.com> User-Agent: Mutt/1.5.20 (2009-08-17) X-ELTE-SpamScore: -2.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.0 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.3.1 -2.0 BAYES_00 BODY: Bayes spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4757 Lines: 140 * Ken Sumrall 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 > --- > 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-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/