Make people use the proper cli/sti replacements

a number of drivers)

So the fix for our problems is:

 a) in fs/namei.c replace d_unhash() with a safe version.
 b) in fs/nfs/dir.c replace d_drop(dentry) in beginning of nfs_unlink()
 with list_del_init(&dentry->d_hash);

Ugh.  nfs_unlink() is actually racy as hell - look what happens if
we enter it with ->d_count == 1, see that nfs_sillyrename() doesn't
need to do anything and call nfs_safe_remove().  In the meanwhile
somebody does dcache lookup (without going into NFS code - plain
and simple cache hit) and increments ->d_count.  nfs_safe_remove()
decides that something is very rotten and fails.

AFAICS we should take the test for ->d_count + d_drop if it's 1
under dcache_lock (and in one place).  Comments?

Proposed fix follows:
	* dget/dput killed in vfs_unlink() (safely)
	* nfs_unlink() starts with check for ->d_count (under dcache_lock)
	* if it's > 1 - sillyrename
	* if it is 1 - immediately unhash, then drop dcache_lock.
		after that we do as in old variant, except that
		rehashing is done in nfs_unlink() and only if there
		was an error - if there was none we simply leave
		d_delete() to vfs_unlink().

confused the NFS client code wrt the exclusiveness of
a dentry getting removed.

One more doc correction while we are at it...

i've done a minor comment update in softirq.c, plus i've written a
cli-sti-removal.txt guide to help driver writers do the transition.

The serial layer is restructured to allow less code duplication (and
hence bug duplication) across various serial drivers.  Since ARM adds
six extra serial drivers, maintaining six copies of serial.c was not
my idea of fun.

Therefore, we've ended up with a core serial driver, which knows about
the interactions with the tty layer, and low-level hardware drivers,
which know all about the hardware.  The interface between the two is
described in "Documentation/serial/driver".

This patch completely removes the old serial.c driver and its associated
configuration options, as you requested at KS2002.  We keep a certain
amount of configuration compatibility with the per-architecture serial.h
file for the moment; this *will* be killed in the next round of patches.
The biggest user of this is x86, and since I don't have an x86 box to
test this stuff on, I think the changes are best kept separate.

This is a massive cleanup of the IRQ subsystem.  It's losely based on
Linus' original idea and DaveM's original implementation, to fold our
various irq, softirq and bh counters into the preemption counter.

with this approach it was possible:

 - to remove the 'big IRQ lock' on SMP - on which sti() and cli() relied.

 - to streamline/simplify arch/i386/kernel/irq.c significantly.

 - to simplify the softirq code.

 - to remove the preemption count increase/decrease code from the lowlevel
   IRQ assembly code.

 - to speed up schedule() a bit.

Global sti() and cli() is gone forever on SMP, there is no more globally
synchronizing irq-disabling capability.  All code that relied on sti()
and cli() and restore_flags() must use other locking mechanisms from now
on (spinlocks and __cli()/__sti()).

obviously this patch breaks massive amounts of code, so only limited
.configs are working at the moment (UP is expected to be unaffected, but
SMP will require various driver updates).

The patch was developed and tested on SMP systems, and while the code is
still a bit rough in places, the base IRQ code appears to be pretty
robust and clean.

while it boots already so the worst is over, there is lots of work left:
eg. to fix the serial layer to not use cli()/sti() and bhs ...

In the /proc/fs/jffs/* code we switch to passing number of mtd device
(as an integer) instead of messing with kdev_t (which would always be
mk_kdev(MTD_BLOCK_MAJOR, device_number) anyway).

Removed prototypes of several functions that do not exist...

->bios_param() switched from kdev_t to struct block_device *.

Caller and all instances updated.

somewhat related to the above - drivers/block/paride/* switched to
module_init()/module_exit(), pd.c taught to use LBA if disks support
it (needed for paride disks >8Gb; change is fairly trivial and I've
got 40Gb one ;-)

blk_ioctl() not exported anymore; calls moved from drivers to block_dev.c.

Horrors with open/reread_partition exclusion are starting to get fixed.

It's not the final variant, but at least we are getting the logics into
one place; switch to final variant will happen once we get per-disk
analog of gendisks.  New fields - ->bd_part_sem and ->bd_part_count.

The latter counts the amount of opened partitions.  The former protects
said count _and_ is held while we are rereading partition tables.
Helpers - dev_part_lock()/dev_part_unlock() (currently taking kdev_t; that
will change pretty soon).  No more ->open() and ->release() for partitions,
all that logics went to generic code.  Lock hierachy is currently messy:

  ->bd_sem for partitions -> ->bd_part_sem -> ->bd_sem for entire disks

Ugly, but that'll go away and to get the final variant of locking right
now would take _really_ big patch - with a lot of steps glued together.
The damn thing is large as it is...

for partitioned devices we use ->nr_sect to find the size; blk_size[] is
still used for things like floppy.c, etc.; that will go away later.

There was only one place (do_open()) that needed it - the rest uses
->bd_inode->i_size now.  So blkdev_size_in_bytes() is gone - it's
expanded in its only caller.  Same place (do_open()) finds the partition
offset and stores it in new field ->bd_offset.  As the result, call of
get_gendisk() is gone from the IO path - in blk_partition_remap() we
just add ->bd_offset.

Additionally, we take driver probing (get_blkfops()) outside of ->bd_sem
(again, do_open()) - that will allow to kill ad-hackery in check_partitions()
(opening bdev by hand).

struct gendisk and partition parsers divorced; all these parsers (IBM style,
disklabel, etc.) just fill the structure they get from check_partitions().

Actual setting the things up (filling hd_struct arrays, telling RAID that
we had found partitions worth a look, etc.) is taken into check_partitions()
and done only when we are done with parsing.  Parsers don't know (or care)
what majors/minors they are dealing with; that knowledge also went to
check_partitions().

a bunch of places doing invalidate_device() either didn't need it at all
or actually wanted wipe_partitions().  Switched.