[patch] The patch which I used

laptop-mode-for-2.6.3.patch (text/plain), 22.37 KB, created by Johannes Ballé on 2004-03-24 05:18:12 UTC

diff -Naur linux-2.6.3/Documentation/laptop-mode.txt linux-2.6.3-withlaptopmode/Documentation/laptop-mode.txt
--- linux-2.6.3/Documentation/laptop-mode.txt	1970-01-01 01:00:00.000000000 +0100
+++ linux-2.6.3-withlaptopmode/Documentation/laptop-mode.txt	2004-03-07 11:21:30.000000000 +0100
@@ -0,0 +1,480 @@
+How to conserve battery power using laptop-mode
+-----------------------------------------------
+
+Document Author: Bart Samwel ([e-mail])
+Date created: January 2, 2004
+
+Introduction
+------------
+
+Laptopmode is used to minimize the time that the hard disk needs to be spun up,
+to conserve battery power on laptops. It has been reported to cause significant
+power savings.
+
+Contents
+--------
+
+* Introduction
+* The short story
+* Caveats
+* The details
+* Tips & Tricks
+* Control script
+* ACPI integration
+* Monitoring tool
+
+
+The short story
+---------------
+
+If you just want to use it, run the laptop_mode control script (which is included
+at the end of this document) as follows:
+
+# laptop_mode start
+
+Then set your harddisk spindown time to a relatively low value with hdparm:
+
+hdparm -S 4 /dev/hda
+
+The value -S 4 means 20 seconds idle time before spindown. Your harddisk will
+now only spin up when a disk cache miss occurs, or at least once every 10
+minutes to write back any pending changes.
+
+To stop laptop_mode, remount your filesystems with regular commit intervals
+(e.g., 5 seconds), and run "laptop_mode stop".
+
+
+Caveats
+-------
+
+* The downside of laptop mode is that you have a chance of losing up
+  to 10 minutes of work. If you cannot afford this, don't use it!
+
+* Most desktop hard drives have a very limited lifetime measured in spindown
+  cycles, typically about 50.000 times (it's usually listed on the spec sheet).
+  Check your drive's rating, and don't wear down your drive's lifetime if you
+  don't need to.
+
+* If you mount some of your ext3/reiserfs filesystems with the -n option, then
+  the control script will not be able to remount them correctly. You must set
+  DO_REMOUNTS=0 in the control script, otherwise it will remount them with the
+  wrong options -- or it will fail because it cannot write to /etc/mtab.
+
+* If you have your filesystems listed as type "auto" in fstab, like I did, then
+  the control script will not recognize them as filesystems that need remounting.
+
+The details
+-----------
+
+Laptop-mode is controlled by the flag /proc/sys/vm/laptop_mode. When this
+flag is set, any physical disk read operation (that might have caused the
+hard disk to spin up) causes Linux to flush all dirty blocks. The result
+of this is that after a disk has spun down, it will not be spun up anymore
+to write dirty blocks, because those blocks had already been written
+immediately after the most recent read operation
+
+To increase the effectiveness of the laptop_mode strategy, the laptop_mode
+control script increases dirty_expire_centisecs and dirty_writeback_centisecs in
+/proc/sys/vm to about 10 minutes (by default), which means that pages that are
+dirtied are not forced to be written to disk as often. The control script also
+changes the dirty background ratio, so that background writeback of dirty pages
+is not done anymore. Combined with a higher commit value (also 10 minutes) for
+ext3 or ReiserFS filesystems (also done automatically by the control script),
+this results in concentration of disk activity in a small time interval which
+occurs only once every 10 minutes, or whenever the disk is forced to spin up by
+a cache miss. The disk can then be spun down in the periods of inactivity.
+
+If you want to find out which process caused the disk to spin up, you can
+gather information by setting the flag /proc/sys/vm/block_dump. When this flag
+is set, Linux reports all disk read and write operations that take place, and
+all block dirtyings done to files. This makes it possible to debug why a disk
+needs to spin up, and to increase battery life even more.
+
+If 10 minutes is too much or too little downtime for you, you can configure
+this downtime as follows. In the control script, set the MAX_AGE value to the
+maximum number of seconds of disk downtime that you would like. You should
+then set your filesystem's commit interval to the same value. The dirty ratio
+is also configurable from the control script.
+
+If you don't like the idea of the control script remounting your filesystems
+for you, you can change DO_REMOUNTS to 0 in the script.
+
+Thanks to Kiko Piris, the control script can be used to enable laptop mode on
+both the Linux 2.4 and 2.6 series.
+
+
+Tips & Tricks
+-------------
+
+* Bartek Kania reports getting up to 50 minutes of extra battery life (on top
+  of his regular 3 to 3.5 hours) using very aggressive power management (hdparm
+  -B1) and a spindown time of 5 seconds (hdparm -S1).
+
+* You can spin down the disk while playing MP3, by setting the disk readahead
+  to 8MB (hdparm -a 16384). Effectively, the disk will read a complete MP3 at
+  once, and will then spin down while the MP3 is playing. (Thanks to Bartek
+  Kania.)
+
+* Drew Scott Daniels observed: "I don't know why, but when I decrease the number
+  of colours that my display uses it consumes less battery power. I've seen
+  this on powerbooks too. I hope that this is a piece of information that
+  might be useful to the Laptop Mode patch or it's users."
+
+
+Control script
+--------------
+
+Please note that this control script works for the Linux 2.4 and 2.6 series.
+
+--------------------CONTROL SCRIPT BEGIN------------------------------------------
+#!/bin/sh
+
+# start or stop laptop_mode, best run by a power management daemon when
+# ac gets connected/disconnected from a laptop
+#
+# install as /sbin/laptop_mode
+#
+# Contributors to this script:   Kiko Piris
+#				 Bart Samwel
+#				 Dax Kelson
+# Original Linux 2.4 version by: Jens Axboe
+
+parse_mount_opts () {
+	echo "$*"			| \
+	sed 's/commit=[0-9]*//g'	| \
+	sed 's/,,*/,/g'			| \
+	sed 's/^,//'			| \
+	sed 's/,$//'			| \
+	cat -
+}
+
+KLEVEL="$(uname -r | cut -c1-3)"
+case "$KLEVEL" in
+	"2.4")
+		true
+		;;
+	"2.6")
+		true
+		;;
+	*)
+		echo "Unhandled kernel level: $KLEVEL ('uname -r' = '$(uname -r)')"
+		exit 1
+		;;
+esac
+
+# Shall we remount journaled fs. with appropiate commit interval? (1=yes)
+DO_REMOUNTS=1
+
+# age time, in seconds. should be put into a sysconfig file
+MAX_AGE=600
+
+# Allowed dirty ratio, in pct. should be put into a sysconfig file as well.
+DIRTY_RATIO=40
+
+# kernel default dirty buffer age
+DEF_AGE=30
+DEF_UPDATE=5
+DEF_DIRTY_BACKGROUND_RATIO=10
+DEF_DIRTY_RATIO=40
+
+
+if [ ! -e /proc/sys/vm/laptop_mode ]; then
+	echo "Kernel is not patched with laptop_mode patch."
+	exit 1
+fi
+
+if [ ! -w /proc/sys/vm/laptop_mode ]; then
+	echo "You do not have enough privileges to enable laptop_mode."
+	exit 1
+fi
+
+case "$1" in
+	start)
+		AGE=$((100*$MAX_AGE))
+		echo -n "Starting laptop_mode"
+		case "$KLEVEL" in
+			"2.4")
+				echo "1"				> /proc/sys/vm/laptop_mode
+				echo "30 500 0 0 $AGE $AGE 60 20 0"	> /proc/sys/vm/bdflush
+				;;
+			"2.6")
+				echo "1"				> /proc/sys/vm/laptop_mode
+				echo "$AGE"				> /proc/sys/vm/dirty_writeback_centisecs
+				echo "$AGE"				> /proc/sys/vm/dirty_expire_centisecs
+				echo "$DIRTY_RATIO"			> /proc/sys/vm/dirty_ratio
+				echo "$DIRTY_RATIO"			> /proc/sys/vm/dirty_background_ratio
+				;;
+		esac
+		if [ $DO_REMOUNTS -eq 1 ]; then
+			cat /etc/mtab | while read DEV MP FST OPTS DUMP PASS ; do
+				PARSEDOPTS="$(parse_mount_opts "$OPTS")"
+				case "$FST" in
+					"ext3")		mount $DEV -t $FST $MP -o remount,$PARSEDOPTS,commit=$MAX_AGE ;;
+					"reiserfs")	mount $DEV -t $FST $MP -o remount,$PARSEDOPTS,commit=$MAX_AGE ;;
+					"xfs")		mount $DEV -t $FST $MP -o remount,$PARSEDOPTS,commit=$MAX_AGE ;;
+				esac
+			done
+		fi
+		echo "."
+		;;
+	stop)
+		U_AGE=$((100*$DEF_UPDATE))
+		B_AGE=$((100*$DEF_AGE))
+		echo -n "Stopping laptop_mode"
+		case "$KLEVEL" in
+			"2.4")
+				echo "0"				> /proc/sys/vm/laptop_mode
+				echo "30 500 0 0 $U_AGE $B_AGE 60 20 0"	> /proc/sys/vm/bdflush
+				;;
+			"2.6")
+				echo "0"				> /proc/sys/vm/laptop_mode
+				echo "$U_AGE"				> /proc/sys/vm/dirty_writeback_centisecs
+				echo "$B_AGE"				> /proc/sys/vm/dirty_expire_centisecs
+				echo "$DEF_DIRTY_RATIO"			> /proc/sys/vm/dirty_ratio
+				echo "$DEF_DIRTY_BACKGROUND_RATIO"	> /proc/sys/vm/dirty_background_ratio
+				;;
+		esac
+		if [ $DO_REMOUNTS -eq 1 ]; then
+			cat /etc/mtab | while read DEV MP FST OPTS DUMP PASS ; do
+				PARSEDOPTS="$(parse_mount_opts "$OPTS")"
+				case "$FST" in
+					"ext3")		mount $DEV -t $FST $MP -o remount,$PARSEDOPTS ;;
+					"reiserfs")	mount $DEV -t $FST $MP -o remount,$PARSEDOPTS ;;
+					"xfs")		mount $DEV -t $FST $MP -o remount,$PARSEDOPTS ;;
+				esac
+			done
+		fi
+		echo "."
+		;;
+	*)
+		echo "$0 {start|stop}"
+		;;
+
+esac
+
+exit 0
+
+--------------------CONTROL SCRIPT END--------------------------------------------
+
+
+ACPI integration
+----------------
+
+Dax Kelson submitted this so that the ACPI acpid daemon will
+kick off the laptop_mode script and run hdparm.
+
+---------------------------/etc/acpi/events/ac_adapter BEGIN-------------------------------------------
+event=ac_adapter
+action=/etc/acpi/actions/battery.sh
+---------------------------/etc/acpi/events/ac_adapter END-------------------------------------------
+
+---------------------------/etc/acpi/actions/battery.sh BEGIN-------------------------------------------
+#!/bin/sh
+
+# cpu throttling
+# cat /proc/acpi/processor/CPU0/throttling for more info
+ACAD_THR=0
+BATT_THR=2
+
+# spindown time for HD (man hdparm for valid values)
+# I prefer 2 hours for acad and 20 seconds for batt
+ACAD_HD=244
+BATT_HD=4
+
+# ac/battery event handler
+
+status=`awk '/^state: / { print $2 }' /proc/acpi/ac_adapter/AC/state`
+
+case $status in
+        "on-line")
+                echo "Setting HD spindown to 2 hours"
+                /sbin/laptop-mode stop
+                /sbin/hdparm -S $ACAD_HD /dev/hda > /dev/null 2>&1
+                /sbin/hdparm -B 255 /dev/hda > /dev/null 2>&1
+                #echo -n $ACAD_CPU:$ACAD_THR > /proc/acpi/processor/CPU0/limit
+                exit 0
+        ;;
+        "off-line")
+                echo "Setting HD spindown to 20 seconds"
+                /sbin/laptop-mode start
+                /sbin/hdparm -S $BATT_HD /dev/hda > /dev/null 2>&1
+                /sbin/hdparm -B 1 /dev/hda > /dev/null 2>&1
+                #echo -n $BATT_CPU:$BATT_THR > /proc/acpi/processor/CPU0/limit
+                exit 0
+        ;;
+esac
+---------------------------/etc/acpi/actions/battery.sh END-------------------------------------------
+
+Monitoring tool
+---------------
+
+Bartek Kania submitted this, it can be used to measure how much time your disk
+spends spun up/down.
+
+---------------------------dslm.c BEGIN-------------------------------------------
+/*
+ * Simple Disk SLeep Monitor
+ *  by Bartek Kania
+ * Licenced under the GPL
+ */
+#include <unistd.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <time.h>
+#include <string.h>
+#include <signal.h>
+#include <sys/ioctl.h>
+#include <linux/hdreg.h>
+
+#ifdef DEBUG
+#define D(x) x
+#else
+#define D(x)
+#endif
+
+int endit = 0;
+
+/* Check if the disk is in powersave-mode
+ * Most of the code is stolen from hdparm.
+ * 1 = active, 0 = standby/sleep, -1 = unknown */
+int check_powermode(int fd)
+{
+    unsigned char args[4] = {WIN_CHECKPOWERMODE1,0,0,0};
+    int state;
+
+    if (ioctl(fd, HDIO_DRIVE_CMD, &args)
+	&& (args[0] = WIN_CHECKPOWERMODE2) /* try again with 0x98 */
+	&& ioctl(fd, HDIO_DRIVE_CMD, &args)) {
+	if (errno != EIO || args[0] != 0 || args[1] != 0) {
+	    state = -1; /* "unknown"; */
+	} else
+	    state = 0; /* "sleeping"; */
+    } else {
+	state = (args[2] == 255) ? 1 : 0;
+    }
+    D(printf(" drive state is:  %s\n", state));
+
+    return state;
+}
+
+char *state_name(int i)
+{
+    if (i == -1) return "unknown";
+    if (i == 0) return "sleeping";
+    if (i == 1) return "active";
+
+    return "internal error";
+}
+
+char *myctime(time_t time)
+{
+    char *ts = ctime(&time);
+    ts[strlen(ts) - 1] = 0;
+
+    return ts;
+}
+
+void measure(int fd)
+{
+    time_t start_time;
+    int last_state;
+    time_t last_time;
+    int curr_state;
+    time_t curr_time = 0;
+    time_t time_diff;
+    time_t active_time = 0;
+    time_t sleep_time = 0;
+    time_t unknown_time = 0;
+    time_t total_time = 0;
+    int changes = 0;
+    float tmp;
+
+    printf("Starting measurements\n");
+
+    last_state = check_powermode(fd);
+    start_time = last_time = time(0);
+    printf("  System is in state %s\n\n", state_name(last_state));
+
+    while(!endit) {
+	sleep(1);
+	curr_state = check_powermode(fd);
+
+	if (curr_state != last_state || endit) {
+	    changes++;
+	    curr_time = time(0);
+	    time_diff = curr_time - last_time;
+
+	    if (last_state == 1) active_time += time_diff;
+	    else if (last_state == 0) sleep_time += time_diff;
+	    else unknown_time += time_diff;
+
+	    last_state = curr_state;
+	    last_time = curr_time;
+
+	    printf("%s: State-change to %s\n", myctime(curr_time),
+		   state_name(curr_state));
+	}
+    }
+    changes--; /* Compensate for SIGINT */
+
+    total_time = time(0) - start_time;
+    printf("\nTotal running time:  %lus\n", curr_time - start_time);
+    printf(" State changed %d times\n", changes);
+
+    tmp = (float)sleep_time / (float)total_time * 100;
+    printf(" Time in sleep state:   %lus (%.2f%%)\n", sleep_time, tmp);
+    tmp = (float)active_time / (float)total_time * 100;
+    printf(" Time in active state:  %lus (%.2f%%)\n", active_time, tmp);
+    tmp = (float)unknown_time / (float)total_time * 100;
+    printf(" Time in unknown state: %lus (%.2f%%)\n", unknown_time, tmp);
+}
+
+void ender(int s)
+{
+    endit = 1;
+}
+
+void usage()
+{
+    puts("usage: dslm [-w <time>] <disk>");
+    exit(0);
+}
+
+int main(int ac, char **av)
+{
+    int fd;
+    char *disk = 0;
+    int settle_time = 60;
+
+    /* Parse the simple command-line */
+    if (ac == 2)
+	disk = av[1];
+    else if (ac == 4) {
+	settle_time = atoi(av[2]);
+	disk = av[3];
+    } else
+	usage();
+
+    if (!(fd = open(disk, O_RDONLY|O_NONBLOCK))) {
+	printf("Can't open %s, because: %s\n", disk, strerror(errno));
+	exit(-1);
+    }
+
+    if (settle_time) {
+	printf("Waiting %d seconds for the system to settle down to "
+	       "'normal'\n", settle_time);
+	sleep(settle_time);
+    } else
+	puts("Not waiting for system to settle down");
+
+    signal(SIGINT, ender);
+
+    measure(fd);
+
+    close(fd);
+
+    return 0;
+}
+---------------------------dslm.c END---------------------------------------------
diff -Naur linux-2.6.3/drivers/block/ll_rw_blk.c linux-2.6.3-withlaptopmode/drivers/block/ll_rw_blk.c
--- linux-2.6.3/drivers/block/ll_rw_blk.c	2004-03-07 11:39:01.000000000 +0100
+++ linux-2.6.3-withlaptopmode/drivers/block/ll_rw_blk.c	2004-03-07 11:32:40.000000000 +0100
@@ -27,6 +27,7 @@
 #include <linux/completion.h>
 #include <linux/slab.h>
 #include <linux/swap.h>
+#include <linux/writeback.h>
 
 static void blk_unplug_work(void *data);
 static void blk_unplug_timeout(unsigned long data);
@@ -2305,6 +2306,15 @@
 		mod_page_state(pgpgout, count);
 	else
 		mod_page_state(pgpgin, count);
+
+	if (unlikely(block_dump)) {
+		char b[BDEVNAME_SIZE];
+		printk("%s(%d): %s block %Lu on %s\n",
+			current->comm, current->pid,
+			(rw & WRITE) ? "WRITE" : "READ",
+			(unsigned long long)bio->bi_sector, bdevname(bio->bi_bdev,b));
+	}
+
 	generic_make_request(bio);
 	return 1;
 }
@@ -2592,10 +2602,22 @@
 		unsigned long duration = jiffies - req->start_time;
 		switch (rq_data_dir(req)) {
 		    case WRITE:
+			/*
+			 * schedule the writeout of pending dirty data when the disk is idle.
+			 * (Writeback is not postponed by writes, only by reads.)
+			 */
+			if (unlikely(laptop_mode))
+				disk_is_spun_up(0);
 			disk_stat_inc(disk, writes);
 			disk_stat_add(disk, write_ticks, duration);
 			break;
 		    case READ:
+			/*
+			 * schedule the writeout of pending dirty data when the disk is idle.
+			 * (postpone writeback until system is quiescent again.)
+			 */
+			if (unlikely(laptop_mode))
+				disk_is_spun_up(1);
 			disk_stat_inc(disk, reads);
 			disk_stat_add(disk, read_ticks, duration);
 			break;
diff -Naur linux-2.6.3/fs/buffer.c linux-2.6.3-withlaptopmode/fs/buffer.c
--- linux-2.6.3/fs/buffer.c	2004-03-07 11:39:16.000000000 +0100
+++ linux-2.6.3-withlaptopmode/fs/buffer.c	2004-03-07 11:21:30.000000000 +0100
@@ -857,10 +857,13 @@
 		struct buffer_head *bh = head;
 
 		do {
-			if (buffer_uptodate(bh))
+			if (buffer_uptodate(bh)) {
 				set_buffer_dirty(bh);
-			else
+				if (unlikely(block_dump))
+					printk("%s(%d): dirtied buffer\n", current->comm, current->pid);
+			} else {
 				buffer_error();
+			}
 			bh = bh->b_this_page;
 		} while (bh != head);
 	}
diff -Naur linux-2.6.3/include/linux/sysctl.h linux-2.6.3-withlaptopmode/include/linux/sysctl.h
--- linux-2.6.3/include/linux/sysctl.h	2004-03-07 11:41:35.000000000 +0100
+++ linux-2.6.3-withlaptopmode/include/linux/sysctl.h	2004-03-07 11:21:30.000000000 +0100
@@ -156,6 +156,8 @@
 	VM_SWAPPINESS=19,	/* Tendency to steal mapped memory */
 	VM_LOWER_ZONE_PROTECTION=20,/* Amount of protection of lower zones */
 	VM_MIN_FREE_KBYTES=21,	/* Minimum free kilobytes to maintain */
+	VM_LAPTOP_MODE=22,      /* vm laptop mode */
+	VM_BLOCK_DUMP=23,       /* block dump mode */
 };
 
 
diff -Naur linux-2.6.3/include/linux/writeback.h linux-2.6.3-withlaptopmode/include/linux/writeback.h
--- linux-2.6.3/include/linux/writeback.h	2004-01-09 07:59:09.000000000 +0100
+++ linux-2.6.3-withlaptopmode/include/linux/writeback.h	2004-03-07 11:21:30.000000000 +0100
@@ -71,12 +71,15 @@
  * mm/page-writeback.c
  */
 int wakeup_bdflush(long nr_pages);
+void disk_is_spun_up(int postpone_writeback);
 
-/* These 5 are exported to sysctl. */
+/* These are exported to sysctl. */
 extern int dirty_background_ratio;
 extern int vm_dirty_ratio;
 extern int dirty_writeback_centisecs;
 extern int dirty_expire_centisecs;
+extern int block_dump;
+extern int laptop_mode;
 
 struct ctl_table;
 struct file;
diff -Naur linux-2.6.3/kernel/sysctl.c linux-2.6.3-withlaptopmode/kernel/sysctl.c
--- linux-2.6.3/kernel/sysctl.c	2004-03-07 11:41:36.000000000 +0100
+++ linux-2.6.3-withlaptopmode/kernel/sysctl.c	2004-03-07 11:21:30.000000000 +0100
@@ -714,6 +714,26 @@
 		.strategy	= &sysctl_intvec,
 		.extra1		= &zero,
 	},
+	{
+		.ctl_name	= VM_LAPTOP_MODE,
+		.procname	= "laptop_mode",
+		.data		= &laptop_mode,
+		.maxlen		= sizeof(laptop_mode),
+		.mode		= 0644,
+		.proc_handler	= &proc_dointvec,
+		.strategy	= &sysctl_intvec,
+		.extra1		= &zero,
+	},
+	{
+		.ctl_name	= VM_BLOCK_DUMP,
+		.procname	= "block_dump",
+		.data		= &block_dump,
+		.maxlen		= sizeof(block_dump),
+		.mode		= 0644,
+		.proc_handler	= &proc_dointvec,
+		.strategy	= &sysctl_intvec,
+		.extra1		= &zero,
+	},
 	{ .ctl_name = 0 }
 };
 
diff -Naur linux-2.6.3/mm/page-writeback.c linux-2.6.3-withlaptopmode/mm/page-writeback.c
--- linux-2.6.3/mm/page-writeback.c	2004-03-07 11:39:34.000000000 +0100
+++ linux-2.6.3-withlaptopmode/mm/page-writeback.c	2004-03-07 12:27:50.000000000 +0100
@@ -28,6 +28,7 @@
 #include <linux/smp.h>
 #include <linux/sysctl.h>
 #include <linux/cpu.h>
+#include <linux/quotaops.h>
 
 /*
  * The maximum number of pages to writeout in a single bdflush/kupdate
@@ -81,6 +82,16 @@
  */
 int dirty_expire_centisecs = 30 * 100;
 
+/*
+ * Flag that makes the machine dump writes/reads and block dirtyings.
+ */
+int block_dump;
+
+/*
+ * Flag that puts the machine in "laptop mode".
+ */
+int laptop_mode;
+
 /* End of sysctl-exported parameters */
 
 
@@ -195,7 +206,7 @@
 	if (nr_reclaimable + ps.nr_writeback <= dirty_thresh)
 		dirty_exceeded = 0;
 
-	if (!writeback_in_progress(bdi) && nr_reclaimable > background_thresh)
+	if (!unlikely(laptop_mode) && !writeback_in_progress(bdi) && nr_reclaimable > background_thresh)
 		pdflush_operation(background_writeout, 0);
 }
 
@@ -289,7 +300,17 @@
 	return pdflush_operation(background_writeout, nr_pages);
 }
 
-static struct timer_list wb_timer;
+
+static void wb_timer_fn(unsigned long unused);
+
+/*
+ * Both timers share the same handler
+ */
+static struct timer_list wb_timer =
+			TIMER_INITIALIZER(wb_timer_fn, 0, 0);
+static struct timer_list laptop_mode_wb_timer =
+			TIMER_INITIALIZER(wb_timer_fn, 0, 0);
+
 
 /*
  * Periodic writeback of "old" data.
@@ -328,6 +349,8 @@
 	oldest_jif = jiffies - (dirty_expire_centisecs * HZ) / 100;
 	start_jif = jiffies;
 	next_jif = start_jif + (dirty_writeback_centisecs * HZ) / 100;
+	if (laptop_mode)
+		wbc.older_than_this = NULL;
 	nr_to_write = ps.nr_dirty + ps.nr_unstable +
 			(inodes_stat.nr_inodes - inodes_stat.nr_unused);
 	while (nr_to_write > 0) {
@@ -346,8 +369,10 @@
 		next_jif = jiffies + HZ;
 	if (dirty_writeback_centisecs)
 		mod_timer(&wb_timer, next_jif);
+	del_timer(&laptop_mode_wb_timer); /* May have been set as a result of our writes. */
 }
 
+
 /*
  * sysctl handler for /proc/sys/vm/dirty_writeback_centisecs
  */
@@ -364,13 +389,38 @@
 	return 0;
 }
 
+static struct timer_list laptop_mode_wb_timer;
+
+static void laptop_mode_wb_timer_fn(unsigned long unused)
+{
+	mod_timer(&wb_timer, jiffies);
+}
+
+/*
+ * We've spun up the disk and we're in laptop mode: schedule writeback
+ * of all dirty data in 5 seconds.
+ *
+ * Laptop mode writeback will be delayed if it has previously been
+ * scheduled to occur within 5 seconds. That way, the writeback will
+ * only be triggered if the system is truly quiet again.
+ */
+void disk_is_spun_up(int postpone_writeback)
+{
+	if (postpone_writeback || !timer_pending(&laptop_mode_wb_timer))
+		mod_timer(&laptop_mode_wb_timer, jiffies + 5 * HZ);
+}
+
+
+/*
+ * Handler for wb_timer and laptop_mode_wb_timer.
+ */
 static void wb_timer_fn(unsigned long unused)
 {
 	if (pdflush_operation(wb_kupdate, 0) < 0)
 		mod_timer(&wb_timer, jiffies + HZ); /* delay 1 second */
-
 }
 
+
 /*
  * If ratelimit_pages is too high then we can get into dirty-data overload
  * if a large number of processes all perform writes at the same time.
@@ -430,11 +480,13 @@
 		vm_dirty_ratio /= 100;
 	}
 
-	init_timer(&wb_timer);
 	wb_timer.expires = jiffies + (dirty_writeback_centisecs * HZ) / 100;
-	wb_timer.data = 0;
-	wb_timer.function = wb_timer_fn;
 	add_timer(&wb_timer);
+
+	init_timer(&laptop_mode_wb_timer);
+	laptop_mode_wb_timer.data = 0;
+	laptop_mode_wb_timer.function = laptop_mode_wb_timer_fn;
+
 	set_ratelimit();
 	register_cpu_notifier(&ratelimit_nb);
 }
@@ -526,6 +578,8 @@
 				__mark_inode_dirty(mapping->host,
 							I_DIRTY_PAGES);
 		}
+		if (unlikely(block_dump))
+			printk("%s(%d): dirtied page\n", current->comm, current->pid);
 	}
 	return ret;
 }