Writeback/pdflush cleanup patch from Steven Augart

* Exposes nr_pdflush_threads as /proc/sys/vm/nr_pdflush_threads, read-only.

  (I like this - I expect that management of the pdflush thread pool
  will be important for many-spindle machines, and this is a neat way
  of getting at the info).

* Adds minimum and maximum checking to the five writable pdflush
  and fs-writeback  parameters.

* Minor indentation fix in sysctl.c

* mm/pdflush.c now includes linux/writeback.h, which prototypes
  pdflush_operation.  This is so that the compiler can
  automatically check that the prototype matches the definition.

* Adds a few comments to existing code.

- Comment and documentation fixlets

- Remove some unneeded fields from swapper_inode (these are a
  leftover from when I had swap using the filesystem IO functions).

- fix a printk bug in pci/pool.c: when dma_addr_t is 64 bit it
  generates a compile warning, and will print out garbage.  Cast it to
  unsigned long long.

- Convert some writeback #defines into enums (Steven Augart)

Having just fiddled with the refcounts of blockdev buffers, I want some
way of assuring that the code is correct and is not leaking
buffer_heads.

There's no easy way to do this: if a blockdev page has pinned buffers
then truncate_complete_page just cuts it loose and we leak memory.

The patch adds a bit of debug code to catch these leaks.  This code,
PF_RADIX_TREE and buffer_error() need to be removed later on.

Removes ext3's open-coded inode and allocation bitmap LRUs.

This patch includes a cleanup to ext3_new_block().  The local variables
`bh', `bh2', `i', `j', `k' and `tmp' have been renamed to something
more palatable.

Remove ext2's open-coded bitmap LRUs.  Core kernel does this for it now.

ext2 and ext3 implement a custom LRU cache of buffer_heads - the eight
most-recently-used inode bitmap buffers and the eight MRU block bitmap
buffers.

I don't like them, for a number of reasons:

- The code is duplicated between filesystems

- The functionality is unavailable to other filesystems

- The LRU only applies to bitmap buffers.  And not, say, indirects.

- The LRUs are subtly dependent upon lock_super() for protection:
  without lock_super protection a bitmap could be evicted and freed
  while in use.

  And removing this dependence on lock_super() gets us one step on
  the way toward getting that semaphore out of the ext2 block allocator -
  it causes significant contention under some loads and should be a
  spinlock.

- The LRUs pin 64 kbytes per mounted filesystem.

Now, we could just delete those LRUs and rely on the VM to manage the
memory.  But that would introduce significant lock contention in
__find_get_block - the blockdev mapping's private_lock and page_lock
are heavily used.

So this patch introduces a transparent per-CPU bh lru which is hidden
inside __find_get_block(), __getblk() and __bread().  It is designed to
shorten code paths and to reduce lock contention.  It uses a seven-slot
LRU.  It achieves a 99% hit rate in `dbench 64'.  It provides benefit
to all filesystems.

The next patches remove the open-coded LRUs from ext2 and ext3.

Taken together, these patches are a code cleanup (300-400 lines gone),
and they reduce lock contention.  Anton tested these patches on the
32-way and demonstrated a throughput improvement of up to 15% on
RAM-only dbench runs.  See http://samba.org/~anton/linux/2.5.24/dbench/

Most of this benefit is from avoiding find_get_page() on the blockdev
mapping.  Because the generic LRU copes with indirect blocks as well as
bitmaps.

Fix from Rahul Karnik and Donald Becker - some new 3c566B mini-PCI NICs
refuse to power up the transceiver unless we tickle an undocumented bit
in an undocumented register.  They worked this out by before-and-after
diffing of the register contents when it was set up by the Windows
driver.

If allocation of a BIO for swap writeout fails, mark the page dirty
again to save it from eviction.

The last changes did trigger another latent bug in the inline assembly.
akpm noticed it because he compiles his kernels with frame pointers.

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

Uninline elv_next_request() and move it to elevator.c, where it belongs.
Because of CURRENT declaration, this actually saves lots of space.  From
Andrew.

init_rootfs() (from ramfs) doesn't appear in any header file.  I didn't
see any that looked like a good home, so lets put a prototype at the top
of fs/namespace.c.  This only use of this function is in namespace.c.

This patch makes sure the 3c509 module license is always GPL.  Currently
the MODULE_LICENSE() marco is only used when CONFIG_ISAPNP or
CONFIG_ISAPNP_MODULE is defined.  I have moved MODULE_LICENSE() to the
#ifdef MODULE section at the bottom of 3c509.c.

Same is true for the MODULE_DEVICE_TABLE() macro.

Not sure why I forgot to do this, but here is a small bit of tidying up
of some leftover parentheses from the memlist macro removal. The
parentheses are just noise and should go.

page_alloc.c does not use either slab.h or swapctl.h. This removes the
inclusion of those headers from page_alloc.c

nr_free_pages() is overly verbose. The following is perhaps clearer and
gets to the point with fewer lines of code and inside of 80 columns.

14 of our 17 architectures define sys_pause exactly the same
way.  The other three don't define it at all.  I assume glibc
translates pause() into sigsuspend() or something.

In favour of those now in kernel.h..

Three arch-determining symbols in drivers/mtd/maps/Config.in are wrong.
They have apparently been generated using the sensible pattern "CONFIG_FOO"
for an architecture "foo"; unfortunately the architectures are not sensible.

  CONFIG_SPARC should be CONFIG_SPARC32
  CONFIG_I386 should be CONFIG_X86
  CONFIG_SH should be CONFIG_SUPERH

Removed a spurious menu definition which was both a duplicate and
had no matching "endmenu".

Removed an "endmenu" for which there was no opening "mainmenu_option".

The config language is *not* shell.  The construct "[ foo ] || [ bar ]"
is legal in shell but not in the config language, where we should use
the equivalent "[ foo -o bar ]"

The format for the "choice" statement is:

  choice 'prompt' "{sub-prompt sub-symbol}*" default-value

and the following is *not* legal config language (note the
positioning of the closing double quote):

  choice 'prompt' "{sub-prompt sub-symbol}* default-value"

It only happens to work because of a combination of accidental
side effects of the current parsers:

  *   unpaired sub-words inside the 2nd word are silently ignored
  *   the missing last word is silently treated as if empty

Two symbols used in drivers/net/wan/Config.in are misspelled.

CONFIG_PPP_MULTLINK should be CONFIG_PPP_MULTILINK
CONFIG_PPP_SYNCTTY should be CONFIG_PPP_SYNC_TTY

1/2 definitions of CONFIG_PC_KEYB have trivially different banners.

1/3 definitions of CONFIG_PARPORT_1284 have trivially different banners.

1/2 definitions of CONFIG_NUMA have trivially different banners.

1/16 definitions of CONFIG_NETDEVICES have trivially different banners.

1/3 definitions of CONFIG_MODVERSIONS have trivially different banners.

1/11 definitions of CONFIG_HOTPLUG have trivially different banners.

2/10 definitions of CONFIG_CD_NO_IDESCSI have trivially different banners.

1/3 definitions of 64-bit CONFIG_BINFMT_ELF have trivially different banners.
1/3 definitions of CONFIG_BINFMT_ELF32 have trivially different banners.