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Update 2.6.x-xfs to 2.6.23-rc4.

Also update fs/xfs with external mainline changes.
There were 12 such missing commits that I detected:

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commit ad690ef9e690f6c31f7d310b09ef1314bcec9033
Author: Al Viro <viro@ftp.linux.org.uk>
    xfs ioctl __user annotations

commit 20c2df83d25c6a95affe6157a4c9cac4cf5ffaac
Author: Paul Mundt <lethal@linux-sh.org>
    mm: Remove slab destructors from kmem_cache_create().

commit d0217ac04ca6591841e5665f518e38064f4e65bd
Author: Nick Piggin <npiggin@suse.de>
    mm: fault feedback #1

commit 54cb8821de07f2ffcd28c380ce9b93d5784b40d7
Author: Nick Piggin <npiggin@suse.de>
    mm: merge populate and nopage into fault (fixes nonlinear)

commit d00806b183152af6d24f46f0c33f14162ca1262a
Author: Nick Piggin <npiggin@suse.de>
    mm: fix fault vs invalidate race for linear mappings

commit a569425512253992cc64ebf8b6d00a62f986db3e
Author: Christoph Hellwig <hch@infradead.org>
    knfsd: exportfs: add exportfs.h header

commit 831441862956fffa17b9801db37e6ea1650b0f69
Author: Rafael J. Wysocki <rjw@sisk.pl>
    Freezer: make kernel threads nonfreezable by default

commit 8e1f936b73150f5095448a0fee6d4f30a1f9001d
Author: Rusty Russell <rusty@rustcorp.com.au>
    mm: clean up and kernelify shrinker registration

commit 5ffc4ef45b3b0a57872f631b4e4ceb8ace0d7496
Author: Jens Axboe <jens.axboe@oracle.com>
    sendfile: remove .sendfile from filesystems that use generic_file_sendfile()

commit 8bb7844286fb8c9fce6f65d8288aeb09d03a5e0d
Author: Rafael J. Wysocki <rjw@sisk.pl>
    Add suspend-related notifications for CPU hotplug

commit 59c51591a0ac7568824f541f57de967e88adaa07
Author: Michael Opdenacker <michael@free-electrons.com>
    Fix occurrences of "the the "

commit 0ceb331433e8aad9c5f441a965d7c681f8b9046f
Author: Dmitriy Monakhov <dmonakhov@openvz.org>
    mm: move common segment checks to separate helper function
--------
Merge of 2.6.x-xfs-melb:linux:29656b by kenmcd.

Console Drivers
===============

The linux kernel has 2 general types of console drivers.  The first type is
assigned by the kernel to all the virtual consoles during the boot process.
This type will be called 'system driver', and only one system driver is allowed
to exist. The system driver is persistent and it can never be unloaded, though
it may become inactive.

The second type has to be explicitly loaded and unloaded. This will be called
'modular driver' by this document. Multiple modular drivers can coexist at
any time with each driver sharing the console with other drivers including
the system driver. However, modular drivers cannot take over the console
that is currently occupied by another modular driver. (Exception: Drivers that
call take_over_console() will succeed in the takeover regardless of the type
of driver occupying the consoles.) They can only take over the console that is
occupied by the system driver. In the same token, if the modular driver is
released by the console, the system driver will take over.

Modular drivers, from the programmer's point of view, has to call:

	 take_over_console() - load and bind driver to console layer
	 give_up_console() - unbind and unload driver

In newer kernels, the following are also available:

	 register_con_driver()
	 unregister_con_driver()

If sysfs is enabled, the contents of /sys/class/vtconsole can be
examined. This shows the console backends currently registered by the
system which are named vtcon<n> where <n> is an integer from 0 to 15. Thus:

       ls /sys/class/vtconsole
       .  ..  vtcon0  vtcon1

Each directory in /sys/class/vtconsole has 3 files:

     ls /sys/class/vtconsole/vtcon0
     .  ..  bind  name  uevent

What do these files signify?

     1. bind - this is a read/write file. It shows the status of the driver if
        read, or acts to bind or unbind the driver to the virtual consoles
        when written to. The possible values are:

	0 - means the driver is not bound and if echo'ed, commands the driver
	    to unbind

        1 - means the driver is bound and if echo'ed, commands the driver to
	    bind

     2. name - read-only file. Shows the name of the driver in this format:

	cat /sys/class/vtconsole/vtcon0/name
	(S) VGA+

	    '(S)' stands for a (S)ystem driver, ie, it cannot be directly
	    commanded to bind or unbind

	    'VGA+' is the name of the driver

	cat /sys/class/vtconsole/vtcon1/name
	(M) frame buffer device

	    In this case, '(M)' stands for a (M)odular driver, one that can be
	    directly commanded to bind or unbind.

     3. uevent - ignore this file

When unbinding, the modular driver is detached first, and then the system
driver takes over the consoles vacated by the driver. Binding, on the other
hand, will bind the driver to the consoles that are currently occupied by a
system driver.

NOTE1: Binding and binding must be selected in Kconfig. It's under:

Device Drivers -> Character devices -> Support for binding and unbinding
console drivers

NOTE2: If any of the virtual consoles are in KD_GRAPHICS mode, then binding or
unbinding will not succeed. An example of an application that sets the console
to KD_GRAPHICS is X.

How useful is this feature? This is very useful for console driver
developers. By unbinding the driver from the console layer, one can unload the
driver, make changes, recompile, reload and rebind the driver without any need
for rebooting the kernel. For regular users who may want to switch from
framebuffer console to VGA console and vice versa, this feature also makes
this possible. (NOTE NOTE NOTE: Please read fbcon.txt under Documentation/fb
for more details).

Notes for developers:
=====================

take_over_console() is now broken up into:

     register_con_driver()
     bind_con_driver() - private function

give_up_console() is a wrapper to unregister_con_driver(), and a driver must
be fully unbound for this call to succeed. con_is_bound() will check if the
driver is bound or not.

Guidelines for console driver writers:
=====================================

In order for binding to and unbinding from the console to properly work,
console drivers must follow these guidelines:

1. All drivers, except system drivers, must call either register_con_driver()
   or take_over_console(). register_con_driver() will just add the driver to
   the console's internal list. It won't take over the
   console. take_over_console(), as it name implies, will also take over (or
   bind to) the console.

2. All resources allocated during con->con_init() must be released in
   con->con_deinit().

3. All resources allocated in con->con_startup() must be released when the
   driver, which was previously bound, becomes unbound.  The console layer
   does not have a complementary call to con->con_startup() so it's up to the
   driver to check when it's legal to release these resources. Calling
   con_is_bound() in con->con_deinit() will help.  If the call returned
   false(), then it's safe to release the resources.  This balance has to be
   ensured because con->con_startup() can be called again when a request to
   rebind the driver to the console arrives.

4. Upon exit of the driver, ensure that the driver is totally unbound. If the
   condition is satisfied, then the driver must call unregister_con_driver()
   or give_up_console().

5. unregister_con_driver() can also be called on conditions which make it
   impossible for the driver to service console requests.  This can happen
   with the framebuffer console that suddenly lost all of its drivers.

The current crop of console drivers should still work correctly, but binding
and unbinding them may cause problems. With minimal fixes, these drivers can
be made to work correctly.

==========================
Antonino Daplas <adaplas@pol.net>