page->buffers is a bit of a layering violation.  Not all address_spaces
have pages which are backed by buffers.

The exclusive use of page->buffers for buffers means that a piece of
prime real estate in struct page is unavailable to other forms of
address_space.

This patch turns page->buffers into `unsigned long page->private' and
sets in place all the infrastructure which is needed to allow other
address_spaces to use this storage.

This change alows the multipage-bio-writeout patches to use
page->private to cache the results of an earlier get_block(), so
repeated calls into the filesystem are not needed in the case of file
overwriting.

Devlopers should think carefully before calling try_to_free_buffers()
or block_flushpage() or writeout_one_page() or waitfor_one_page()
against a page.  It's only legal to do this if you *know* that the page
is buffer-backed.  And only the address_space knows that.
Arguably, we need new a_ops for writeout_one_page() and
waitfor_one_page().  But I have more patches on the boil which
obsolete these functions in favour of ->writepage() and wait_on_page().

The new PG_private page bit is used to indicate that there
is something at page->private.  The core kernel does not
know what that object actually is, just that it's there.
The kernel must call a_ops->releasepage() to try to make
page->private go away.  And a_ops->flushpage() at truncate
time.

I'd like to be able to claim amazing speedups, but
the best benchmark I could find was diffing two
256 megabyte files, which is about 10% quicker.  And
that is probably due to the window size being effectively
50% larger.

Fact is, any disk worth owning nowadays has a segmented
2-megabyte cache, and OS-level readahead mainly seems
to save on CPU cycles rather than overall throughput.
Once you start reading more streams than there are segments
in the disk cache we start to win.

Still.  The main motivation for this work is to
clean the code up, and to create a central point at
which many pages are marshalled together so that
they can all be encapsulated into the smallest possible
number of BIOs, and injected into the request layer.

A number of filesystems were poking around inside the
readahead state variables.  I'm not really sure what they
were up to, but I took all that out.  The readahead
code manages its own state autonomously and should not
need any hints.

- Unifies the current three readahead functions (mmap reads, read(2)
  and sys_readhead) into a single implementation.

- More aggressive in building up the readahead windows.

- More conservative in tearing them down.

- Special start-of-file heuristics.

- Preallocates the readahead pages, to avoid the (never demonstrated,
  but potentially catastrophic) scenario where allocation of readahead
  pages causes the allocator to perform VM writeout.

- Gets all the readahead pages gathered together in
  one spot, so they can be marshalled into big BIOs.

- reinstates the readahead ioctls, so hdparm(8) and blockdev(8)
  are working again.  The readahead settings are now per-request-queue,
  and the drivers never have to know about it.  I use blockdev(8).
  It works in units of 512 bytes.

- Identifies readahead thrashing.

  Also attempts to handle it.  Certainly the changes here
  delay the onset of catastrophic readahead thrashing by
  quite a lot, and decrease it seriousness as we get more
  deeply into it, but it's still pretty bad.

Before the mempool was added, the VM was getting many, many
0-order allocation failures due to the atomic ratnode
allocations inside swap_out.  That monster mempool is
doing its job - drove a 256meg machine a gigabyte into
swap with no ratnode allocation failures at all.

So we do need to trim that pool a bit, and also handle
the case where swap_out fails, and not just keep
pointlessly calling it.

This changes everything arch specific PPC and i386 which should have
been unsigned long (it doesn't *matter*, but bad habits get copied to
where it does matter).

No object code changes

This removes gratuitous & operators in front of tty->process_char_map
and tty->read_flags.

No object code changes

This changes over some bogus casts, and converts the ext2, hfs and
minix set-bit macros.  Also changes pte and open_fds to hand the
actual bitfield rather than whole structure.

No object code changes

This patch implements the following calls to set and retrieve a task's
CPU affinity:

    int sched_setaffinity(pid_t pid, unsigned int len,
    				      unsigned long *new_mask_ptr)
    int ched_getaffinity(pid_t pid, unsigned int len,
    				      unsigned long *user_mask_ptr)

	a) part of open_namei() done after we'd found vfsmount/dentry of
the object we want to open had been split into a helper - may_open().

	b) do_open() in fs/nfsctl.c didn't do any permission checks on
the nfsd file it was opening - sudden idiocy attack on my part (I missed
the fact that dentry_open() doesn't do permission checks - open_namei()
does).  Fixed by adding obvious may_open() calls.

As per David Mosberger's request, splits into per-arch files (solves the
#include mess), and fixes my "was not an lvalue" bug.

Cosmetic change: x86_capability.  Makes it an unsigned long, and
removes the gratuitous & operators (it is already an array).  These
produce warnings when set_bit() etc. takes an unsigned long * instead
of a void *.

Originally from Rusty Russell

i810_rng: add support for other i8xx chipsets to the Random Number Generator module.
This is being done by adding the detection of the 82801BA(M) and 82801CA(M) I/O Controller Hub's.

- Eliminate the mate member of the ata_channel structure. The information
   provided by it is already present. This patch may have undesirable
   effects on the ns87415.c and trm290.c host chip drivers, but it's worth
   for structural reasons to have it.

- Kill unused code, which was "fixing" interrupt routing from ide-pci.c Don't
   pass any "mate" between the functions there.

- Don't define SUPPORT_VLB_SYNC unconditionally in ide-taskfile.c

- Apply Vojtech Pavliks fix for piix host-chip driver crashes.

- Add linux/types.h to ide-pnp.c.

- Apply latest sis5513 host chip driver patch from by Lionel Bouton by hand.

- Apply patch by Paul Macerras for power-mac.

- Try to make the ns87415 driver a bit more reentrant.

into penguin.transmeta.com:/home/penguin/torvalds/repositories/kernel/linux

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

cleaned up the comments to put them in proper docbook format.

sanity checking and cleanup on device disconnect.
  
    - Splits apart usb_dec_dev_use(), for driver use, and
      usb_free_dev(), for hub/hcd use.  Both now have
      kerneldoc, and will BUG() if the refcount and the
      device tree get out of sync.  (Except for cleanup of
      root hub init errors, refcount must go to zero only
      at the instant disconnect processing completes.)
  
    - More usbcore-internal function declarations are
      now moved out of <linux/usb.h> into hcd.h
  
    - Driver-accessible refcounting is now inlined; minor
      code shrinkage, it's using atomic inc/dec instructions
      not function calls.

<note from greg k-h, there is still some work to be done with USB device
 reference counting, but this patch is a step in the right direction.>

This fixes some kerneldoc bugs for USB.  It catches up with
the recent rename, and includes a couple minor tweaks/fixes
I happened to notice.

- Documentation updates
- BKL removal (devfs doesn't need the BKL)
- Changed <devfs_rmdir> to allow later additions if not yet empty
- Added calls to <devfs_register_partitions> in drivers/block/blkpc.c
  <add_partition> and <del_partition>
- Bug fixes in unique number and devnum allocators.

This patch moves the generation of the asm interrupt entry stubs from
i8259.c to entry.S.  This allows it to be done with less code and
without needing duplicate definitions of SAVE_ALL, GET_CURRENT, etc.

It is a step on the road to removal of the arrays.
It also solves other things, like the fact that Linux
is unable to read the last sector of a disk or partition
with an odd number of sectors.

Unfortunately the proc filesystem has a limit on the number of dynamic
proc entries it can create. On large systems we can exhaust the default
(4096) very quickly. The following patch increases the default to
something more reasonable.

We forgot to include linux/init.h in fs/nfsd/nfsctl.c.

Since we do not set the task state to TASK_INTERRUPTIBLE, we busy loop.

On larger SMP this can actually result in a lockup due to the way
migration thread initalisation is done (nr_cpus threads are created
and they all busy loop until the scheduler evenly distributes them,
one on each cpu. With this rogue thread busy looping things can become
unbalanced and the migration threads never distribute themselves onto
all cpus).

include/linux/seq_file.h uses memcpy and struct semaphore and so should
include the relevant files.

renamed the bluetooth.c file to bluettty.c to help prevent user confusion
between this driver and the bluez bluetooth stack in the kernel.

This was originally created by David many months ago and posted to the
list, but not put into the kernel.

I modified the original patch to:
-patch against the 2.5.7 kernel
-use the 'real' interface number, not position (to do this I added 2
 methods in usb.c)

Here is an updated patch using kmalloc that removes the page limit
on bulk transfers in usbfs.  I've tested it and it seems to work OK.

(eg ppc64) where foo points to a function descriptor and .foo is
the address of the actual function.

optimisations on some architectures.

ppc64: remove local_flush_* functions, just define them directly