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SubjectRe: Automatically mount or remount EXT3 partitions with EXT2 when alaptop is powered by a battery?
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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