[PATCH] Add documentation about /proc/sys/vm/laptop_mode to various docs.

From: Bart Samwel <bart@samwel.tk>

A bunch of small laptop mode updates:

* Mention the laptop_mode and block_dump sysctls in the relevant docs,
  referring to the laptop-mode.txt. Improve description of what the
  laptop_mode knob means (i.e. seconds between last I/O and automatic
  sync).

* Document the most relevant config file options.

* Change the installation instructions in the laptop mode doc to describe
  the ACPI-bound version first, because this is the easiest. Explain
  the non-ACPI version afterwards. Added a reference to my "packaged
  version" of the scripts.

* Move the setting of hdparm and cpu frequency out of the ACPI script
  and into the core laptop mode script. Add config option DO_HD to
  enable hdparm. Add config setting HD to set device to do hdparm on.
  Rename Dax's CPU_MANAGE to DO_CPU, with 0/1 instead of yes/no, to
  improve consistency.

* Fix a problem where the root filesystem wouln't be remounted when
  /etc/mtab listed its type as "unknown". Deduce the type of "unknown"
  filesystems from /etc/fstab.

This depends on the patch that adds config files, which was submitted
to Linus by Dax Kelson on July 10.
Signed-off-by: Bart Samwel <bart@samwel.tk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

Documentation/filesystems/proc.txt

@@ -1232,6 +1232,18 @@ nr_hugepages configures number of hugetlb page reserved for the system.
 hugetlb_shm_group contains group id that is allowed to create SysV shared
 memory segment using hugetlb page.
 
+laptop_mode
+-----------
+
+laptop_mode is a knob that controls "laptop mode". All the things that are
+controlled by this knob are discussed in Documentation/laptop-mode.txt.
+
+block_dump
+----------
+
+block_dump enables block I/O debugging when set to a nonzero value. More
+information on block I/O debugging is in Documentation/laptop-mode.txt.
+
 2.5 /proc/sys/dev - Device specific parameters
 ----------------------------------------------
 

Documentation/sysctl/vm.txt

@@ -24,11 +24,14 @@ Currently, these files are in /proc/sys/vm:
 - dirty_writeback_centisecs
 - max_map_count
 - min_free_kbytes
+- laptop_mode
+- block_dump
 
 ==============================================================
 
 dirty_ratio, dirty_background_ratio, dirty_expire_centisecs,
-dirty_writeback_centisecs, vfs_cache_pressure:
+dirty_writeback_centisecs, vfs_cache_pressure, laptop_mode,
+block_dump:
 
 See Documentation/filesystems/proc.txt