[Fwd: Re: Automatically mount or remount EXT3 partitions with EXT2 when alaptop is powered by a battery?]

[Miles Lane <miles megapathdsl net>]

-----Forwarded Message-----

> From: Andrew Morton <akpm zip com au>
> To: Miles Lane <miles megapathdsl net>
> Cc: LKML <linux-kernel vger kernel org>
> Subject: Re: Automatically mount or remount EXT3 partitions with EXT2 when  alaptop is powered by a battery?
> Date: 25 Jun 2002 10:03:47 -0700
> 
> Miles Lane wrote:
> > 
> > Hi,
> > 
> > Is there any possibility we could:
> > 
> > 1)  Add support to the boot/mounting process
> >     so that, if a machine is being powered by
> >     battery, EXT3 partitions are mounted with
> >     EXT2, instead?
> > 
> > 2)  While the machine is running, notice when the
> >     power source switches between AC and battery
> >     or vice versa and remount partitions EXT3
> >     partitions to use EXT2 whenever a battery is
> >     being used?
> > 
> 
> umm, why?
> 
> If it's because of the disk-spins-up-too-much problem then
> that can be addressed by allowing the commit interval to be
> set to larger values.
> 
> --- 2.4.19-pre10/fs/jbd/journal.c~ext3-commit-interval	Fri Jun  7 22:56:37 2002
> +++ 2.4.19-pre10-akpm/fs/jbd/journal.c	Sat Jun  8 00:30:32 2002
> @@ -34,6 +34,7 @@
>  #include <linux/init.h>
>  #include <linux/mm.h>
>  #include <linux/slab.h>
> +#include <linux/sysctl.h>
>  #include <asm/uaccess.h>
>  #include <linux/proc_fs.h>
>  
> @@ -85,6 +86,8 @@ EXPORT_SYMBOL(journal_force_commit);
>  
>  static int journal_convert_superblock_v1(journal_t *, journal_superblock_t *);
>  
> +int jbd_commit_interval = 5;	/* /proc/sys/fs/jbd_commit_interval */
> +
>  /*
>   * journal_datalist_lock is used to protect data buffers:
>   *
> @@ -223,8 +226,8 @@ int kjournald(void *arg)
>  	journal->j_task = current;
>  	wake_up(&journal->j_wait_done_commit);
>  
> -	printk(KERN_INFO "kjournald starting.  Commit interval %ld seconds\n",
> -			journal->j_commit_interval / HZ);
> +	printk(KERN_INFO "kjournald starting.  Commit interval %d seconds\n",
> +			jbd_commit_interval);
>  	list_add(&journal->j_all_journals, &all_journals);
>  
>  	/* And now, wait forever for commit wakeup events. */
> @@ -708,8 +711,6 @@ static journal_t * journal_init_common (
>  	init_MUTEX(&journal->j_checkpoint_sem);
>  	init_MUTEX(&journal->j_sem);
>  
> -	journal->j_commit_interval = (HZ * 5);
> -
>  	/* The journal is marked for error until we succeed with recovery! */
>  	journal->j_flags = JFS_ABORT;
>  
> @@ -1775,59 +1776,41 @@ int journal_enable_debug;
>  EXPORT_SYMBOL(journal_enable_debug);
>  #endif
>  
> -#if defined(CONFIG_JBD_DEBUG) && defined(CONFIG_PROC_FS)
> -
> -static struct proc_dir_entry *proc_jbd_debug;
> -
> -int read_jbd_debug(char *page, char **start, off_t off,
> -			  int count, int *eof, void *data)
> -{
> -	int ret;
> -
> -	ret = sprintf(page + off, "%d\n", journal_enable_debug);
> -	*eof = 1;
> -	return ret;
> -}
> +static ctl_table jbd_table[] = {
> +	{ 1, "jbd-commit-interval", &jbd_commit_interval,
> +		sizeof(jbd_commit_interval), 0644, NULL,
> +		&proc_dointvec, NULL, },
> +#ifdef CONFIG_JBD_DEBUG
> +	{ 2, "jbd-debug", &journal_enable_debug,
> +		sizeof(journal_enable_debug), 0644, NULL,
> +		&proc_dointvec, NULL, },
> +#endif
> +	{ 0, },
> +};
>  
> -int write_jbd_debug(struct file *file, const char *buffer,
> -			   unsigned long count, void *data)
> -{
> -	char buf[32];
> +static ctl_table jbd_root[] = {
> +	{ FS_JBD, "jbd", NULL, 0, 0755, jbd_table, },
> +	{ 0, },
> +};
>  
> -	if (count > ARRAY_SIZE(buf) - 1)
> -		count = ARRAY_SIZE(buf) - 1;
> -	if (copy_from_user(buf, buffer, count))
> -		return -EFAULT;
> -	buf[ARRAY_SIZE(buf) - 1] = '\0';
> -	journal_enable_debug = simple_strtoul(buf, NULL, 10);
> -	return count;
> -}
> +static ctl_table fs_root[] = {
> +	{ CTL_FS, "fs", NULL, 0, 0755, jbd_root, },
> +	{ 0, },
> +};
>  
> -#define JBD_PROC_NAME "sys/fs/jbd-debug"
> +static struct ctl_table_header *sysctl_header;
>  
> -static void __init create_jbd_proc_entry(void)
> +static void __init create_jbd_sysctls(void)
>  {
> -	proc_jbd_debug = create_proc_entry(JBD_PROC_NAME, 0644, NULL);
> -	if (proc_jbd_debug) {
> -		/* Why is this so hard? */
> -		proc_jbd_debug->read_proc = read_jbd_debug;
> -		proc_jbd_debug->write_proc = write_jbd_debug;
> -	}
> +	sysctl_header = register_sysctl_table(fs_root, 0);
>  }
>  
> -static void __exit remove_jbd_proc_entry(void)
> +static void __exit remove_jbd_sysctls(void)
>  {
> -	if (proc_jbd_debug)
> -		remove_proc_entry(JBD_PROC_NAME, NULL);
> +	if (sysctl_header)
> +		unregister_sysctl_table(sysctl_header);
>  }
>  
> -#else
> -
> -#define create_jbd_proc_entry() do {} while (0)
> -#define remove_jbd_proc_entry() do {} while (0)
> -
> -#endif
> -
>  /*
>   * Module startup and shutdown
>   */
> @@ -1856,7 +1839,7 @@ static int __init journal_init(void)
>  	ret = journal_init_caches();
>  	if (ret != 0)
>  		journal_destroy_caches();
> -	create_jbd_proc_entry();
> +	create_jbd_sysctls();
>  	return ret;
>  }
>  
> @@ -1867,7 +1850,7 @@ static void __exit journal_exit(void)
>  	if (n)
>  		printk(KERN_EMERG "JBD: leaked %d journal_heads!\n", n);
>  #endif
> -	remove_jbd_proc_entry();
> +	remove_jbd_sysctls();
>  	journal_destroy_caches();
>  }
>  
> --- 2.4.19-pre10/fs/jbd/transaction.c~ext3-commit-interval	Fri Jun  7 22:56:37 2002
> +++ 2.4.19-pre10-akpm/fs/jbd/transaction.c	Fri Jun  7 22:56:37 2002
> @@ -56,7 +56,7 @@ static transaction_t * get_transaction (
>  	transaction->t_journal = journal;
>  	transaction->t_state = T_RUNNING;
>  	transaction->t_tid = journal->j_transaction_sequence++;
> -	transaction->t_expires = jiffies + journal->j_commit_interval;
> +	transaction->t_expires = jiffies + jbd_commit_interval * HZ;
>  
>  	/* Set up the commit timer for the new transaction. */
>  	J_ASSERT (!journal->j_commit_timer_active);
> --- 2.4.19-pre10/include/linux/ext3_fs_sb.h~ext3-commit-interval	Fri Jun  7 22:56:37 2002
> +++ 2.4.19-pre10-akpm/include/linux/ext3_fs_sb.h	Fri Jun  7 22:57:32 2002
> @@ -67,7 +67,6 @@ struct ext3_sb_info {
>  	struct inode * s_journal_inode;
>  	struct journal_s * s_journal;
>  	struct list_head s_orphan;
> -	unsigned long s_commit_interval;
>  	struct block_device *journal_bdev;
>  #ifdef CONFIG_JBD_DEBUG
>  	struct timer_list turn_ro_timer;	/* For turning read-only (crash simulation) */
> --- 2.4.19-pre10/include/linux/jbd.h~ext3-commit-interval	Fri Jun  7 22:56:37 2002
> +++ 2.4.19-pre10-akpm/include/linux/jbd.h	Fri Jun  7 22:58:07 2002
> @@ -522,10 +522,6 @@ struct journal_s
>  	 * compound commit transaction */
>  	int			j_max_transaction_buffers;
>  
> -	/* What is the maximum transaction lifetime before we begin a
> -	 * commit? */
> -	unsigned long		j_commit_interval;
> -
>  	/* The timer used to wakeup the commit thread: */
>  	struct timer_list *	j_commit_timer;
>  	int			j_commit_timer_active;
> @@ -864,6 +860,8 @@ static inline int buffer_jbd_data(struct
>  
>  #endif	/* CONFIG_JBD || CONFIG_JBD_MODULE || !__KERNEL__ */
>  
> +extern int jbd_commit_interval;
> +
>  /*
>   * Compatibility no-ops which allow the kernel to compile without CONFIG_JBD
>   * go here.
> --- 2.4.19-pre10/include/linux/sysctl.h~ext3-commit-interval	Sat Jun  8 00:03:48 2002
> +++ 2.4.19-pre10-akpm/include/linux/sysctl.h	Sat Jun  8 00:04:22 2002
> @@ -546,6 +546,7 @@ enum
>  	FS_LEASES=13,	/* int: leases enabled */
>  	FS_DIR_NOTIFY=14,	/* int: directory notification enabled */
>  	FS_LEASE_TIME=15,	/* int: maximum time to wait for a lease break */
> +	FS_JBD,		/* JBD subdir */
>  };
>  
>  /* CTL_DEBUG names: */
> --- 2.4.19-pre10/Documentation/sysctl/fs.txt~ext3-commit-interval	Sat Jun  8 00:30:58 2002
> +++ 2.4.19-pre10-akpm/Documentation/sysctl/fs.txt	Sat Jun  8 00:39:50 2002
> @@ -27,6 +27,7 @@ Currently, these files are in /proc/sys/
>  - overflowgid
>  - super-max
>  - super-nr
> +- jbd/
>  
>  Documentation for the files in /proc/sys/fs/binfmt_misc is
>  in Documentation/binfmt_misc.txt.
> @@ -138,3 +139,40 @@ thus the maximum number of mounted files
>  can have. You only need to increase super-max if you need to
>  mount more filesystems than the current value in super-max
>  allows you to.
> +
> +==============================================================
> +
> +jbd/jbd-commit-interval:
> +
> +Defines, in seconds, the largest period of time for which the
> +Journalled Block Device driver (JBD) will allow dirty data to remain in
> +memory.  JBD is used by the ext3 filesystem.
> +
> +The default value is five seconds.  Increasing this value will provide
> +"longer" transactions, and may be used to avoid repetitive spinup of
> +disk drives.
> +
> +Note that `kupdate' activity will also cause a JBD commit, so it is
> +necessary to also increase the bdflush `interval' parameter.  This is
> +the fifth field in /proc/sys/vm/bdflush.
> +
> +It should be noted that increasing the value of `jbd-commit-interval'
> +will increase the potential for data loss in the event of a system
> +crash.  ext3 recovery will only restore the filesystem state to that
> +which pertained at the time of the last commit.  So setting this to
> +five minutes means that you can lose up to five minute's worth of data.
> +
> +==============================================================
> +
> +jbd/jbd-debug:
> +
> +If the kernel was compiled for JBD debugging then this sysctl will
> +cause status information to be generated by the JBD driver.  The
> +default value is zero (no debugging).  Larger values cause ore
> +information to be emitted into the system logs.
> +
> +Note that system logging messages can themselves generate disk activity
> +which will trigger more JBD debug messages.  So this option can cause a
> +rapid growth in logfile usage if it is used while a kernel logging
> +daemon is in operation.
> +
> 
> -
> -
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-- 
Miles Lane <miles megapathdsl net>