Spinlocks don't have a buslocked unlock and are faster.

On a P4, time to write a 4M file with 4M one-byte-write()s:

Before:
	0.72s user 5.47s system 99% cpu 6.227 total
	0.76s user 5.40s system 100% cpu 6.154 total
	0.77s user 5.38s system 100% cpu 6.146 total

After:
	1.09s user 4.92s system 99% cpu 6.014 total
	0.74s user 5.28s system 99% cpu 6.023 total
	1.03s user 4.97s system 100% cpu 5.991 total

Even a BUG_ON() makes a measurable difference.  So remove some gratuitous
ones which will just trigger a null pointer deref anyway.

Also remove some debug code which isn't really being maintained any more.

Also replace (effectively):

	test_bit(N, foo);
	set_bit(N, foo);

with

	set_bit(N, foo);
	test_bit(N, foo);

In the first case we'll go onto the bus twice: once for the cache miss and
once to get exclusive write access.  In the second case we only go on the bus
once.  I think.  Certainly this trick chaved 40% off the cost of
shrink_list() when I did it there...

This patch is worth 1% or so on the bash script testing.

several functions in rmap.c are searching the ptes[] array fo find the first
non-null entry.

Despite the fact tha the whole lot is in L1 cache, it is expensive,
especially on 128-byte cacheline machines.

We can encode the index of the first non-null pte entry inside the
pte_chain's `next' field and remove those searches altogether.

This reduces the rmap CPU tax by about 25% on a P4.  For a total runtime
reduction of around 5% in the bash-script intensive test which I use.

Maintaining the `nr_reverse_maps' provides makes a small but
measurable decrease in page_add_rmap() overhead.

I don't think it's a very useful metric, and it can be sort-of inferred from
slabinfo.

From: David Mosberger <davidm@napali.hpl.hp.com>

The cache_sizes array needs to be NULL terminated, otherwise an oversized
kmalloc request runs off the end of the table.

Now that sparc64 is using gcc-3.x we can disallow gcc-2.91, etc.

Documentation/Changes already says 2.95.3, which is working fine for me.

With this change, we no longer require that per-cpu data definitions be
initialised.  That was a workaround for a bug in older gccs.  So remove the
build infrastructure which was checking for that.

Also, mention that nfs-utils-1.0.3 is required.  It isn't required yet, but
will be once we enable larger dev_t: there is an interface for exportfs which
passes dev_t's into the kernel which breaks with larger dev_t.  That
interface is old, deprecated and is not used in nfs-utils-1.0.3.

The wait_on_buffer() debug code is generating false warnings when called from
__block_prepare_write().  It is legal to wait on a zero-ref buffer when its
page is locked.  The page lock keeps try_to_free_buffers() away.

This debug code hasn't found any bugs yet.

into home.transmeta.com:/home/torvalds/v2.5/linux

must never be dereferenced directly. Make that clear in the
attribute.

magic C promotion to silently do so for us.

was the first file tested with my type checker with the anal
pointer attribute checking turned on.

user space access functions. This allows the type checker
to check proper usage.

checking, these end up being no-ops, but they get enabled
by the type checker as special address_space attributes.

There is a stunning bug.

Previously, it was done automatically by the `reti' isntruction upon
returning from the kernel, but that doesn't do the correct thing in
various cases, for instance if there's a context switch, or a softirq.

Allows for the non standard cascade