Hi guys,

Here's an updated version of the laptop-mode patch. The previous version 
had some corner cases that it didn't handle gracefully; this version 
should fix that. Also, thanks to Kiko Piris, the control script has been 
much improved, now featuring linux 2.4 backward compatibility and 
automatic remounts of filesystems. If you have any problems (or no 
problems) with it, please let me know.

-- Bart

List of changes:

* Control script moved into a section of Documentation/laptop-mode.txt.

* Format string problem fixed.

* Control script is now able to remount all ext3/reiserfs filesystems 
with commit=$MAX_AGE. It also removes the commit option when laptop mode 
is stopped. If you don't want this, change DO_REMOUNTS to 0.

* Control script now works for Linux 2.4 as well, to facilitate 
dual-booting.

* Reinstated the timer that I removed in the previous version. In
version 5, frequent reads could postpone writeback indefinitely, because
the kupdate writeback timer was updated to jiffies+5*HZ every time a
read was performed. Now the only thing that is postponed is laptop 
mode's scheduling of writeback, and the normal writeback timer is not 
touched.

* A situation that could arise in version 5 was that a process would 
reach dirty_ratio dirty pages, and that it would stay at that level, 
postponing writeback of all data every time balance_dirty_pages was run 
(by resetting the timer to jiffies+5*HZ). In the attached patch, 
previously scheduled writebacks are not postponed anymore.

* balance_dirty_pages doesn't trigger background writebacks anymore when
laptop mode is active. Version 5 disabled writebacks by setting
dirty_background_ratio to the same value as dirty_ratio, but as it turns 
out this doesn't work: the kernel checks if dirty_background_ratio >= 
dirty_ratio and if so, sets dirty_background_ratio = dirty_ratio/2.