- Eliminate all usages of the obscure QUEUE_EMPTY macro.

 - Eliminate all unneccessary checks for RQ_INACTIVE, this can't happen during
   the time we run the request strategy routine of a single major number block
   device. Perhaps the still remaining usage in scsi and i2o_block.c should be
   killed as well, since the upper ll_rw_blk layer shouldn't pass inactive
   requests down.

Those are all places where we have deeply burried and hidden major number
indexed arrays. Let's deal with them slowly...

Since apparently no body else did care thus far, and since I'm using
this driver, well here it comes:

 - Adjust the airo wireless LAN card driver for the fact that modules
   don't export symbols by default any longer.

 - Make some stuff which obivously should be static there static as well.
   (Plenty of code in Linux actually deserves a review for this
   far too common bug...)

 - Replace ide_delay_50m with mdelay(50). There is absolutely no reason we
   should behave different behaviors whatever IDECS support is enabled or not.

 - Kill last parameter of ide_register_hw(). It should return a pointer to the
   interface registered later.

 - pdc202xx patches by Bartomiej onierkiewicz.

 - ServerWorks chi pset support cleanup by Andrej Panin.

 - Move temporarily ide_setup_ports to main.c unfold it in ide-pnp.c.

This fixes three locations in net/ where per-CPU data could bite us
under preemption.  This is the result of an audit I did and should
constitute all of the unsafe code in net/.

In net/core/skbuff.c I did not have to introduce any code - just
rearrange the grabbing of smp_processor_id() to be in the interrupt off
region.  Pretty clean fixes.

Note in the future we can use put_cpu() and get_cpu() to grab the CPU#
safely.  I will send a patch to Marcelo so we can have a 2.4 version
(which doesn't do the preempt stuff), too...

This adds an optimization to set_cpus_allowed: if the task is not
running, there is no sense in kicking the migration_threads into action,
we just need to update task->cpu.  This was suggested by Mike Kravetz.

Besides being an optimization, this would prevent any future race
between set_cpus_allowed and the migration_threads.

This adds documentation about the O(1) scheduler to Documentation/.  The
new scheduler is complicated and providing future scheduler hackers some
background seems a Good Thing to me.

Specifically:

- add Documentation/sched-coding.txt: an overview of the functions,
  magic numbers, and variables in the scheduler as well as (most
  importantly) a review of the locking semantics.

- add Documentation/sched-design.txt: an edited version of Ingo's
  initial email to lkml about his scheduler.  Goes over the design,
  implementation, and goals of the scheduler.  I tried to edit it where
  needed to bring it in line with the scheduler as it is today.

- modify kernel/sched.c: update your copyright and add a change entry
  for the new scheduler.

The attached trivial patch simply changes the printk debug statement in
do_exit when preempt_count!=0 to say "note" instead of "error" and log
at KERN_INFO in lieu of KERN_ERR.

I want to keep the message around a bit, but people get too paranoid
when things like nfsd legitimately exit with a preempt_count=1.

This makes sure that sys_sync() will terminate.  It counts up the
number of dirty pages in the machine and will refuse to write out more
than 1.25 times this number of pages.  This function is called twice
on the sys_sync() path, so the kernel will actually write 2.5x the number
of initially-dirty pages before giving up.

It might reduce pagemap_lru_lock hold times a little, and is more
consistent.  I think all global page accounting is now inside
page_states[].

Factor out some similar code in page_alloc.c

For historical reasons, ext3 has a private BH state bit which has
global scope.  This patch moves it inside ext3.

Patch from Anton Blanchard which replaces

	printk(KERN_FOO __FUNCTION__ ": msg");

with
	printk(KERN_FOO "%s: msg", __FUNCTION__);

in ext3.

Fixes all the goto spaghetti in generic_file_write() and turns it into
something which humans can understand.

Andi tells me that gcc3 does a decent job of relocating blocks out of
line anyway.  This patch gives the compiler a helping hand with
appropriate use of likely() and unlikely().

Random cleanup: remove the mem_map_t typedef.  Just use 'struct page'
everywhere.

An implementation of directory-synchronous mounts.

I sent this out some months ago and it didn't generate a lot of
interest.  Later we had one of the usual cheery exchanges with Wietse
Venema (postfix development) and he agreed that directory synchronous
mounts were something that he could use, and that there was benefit in
implementing them in Linux.  If you choose to apply this I'll push the
2.4 patch.



Patch against e2fsprogs-1.26:
        http://www.zip.com.au/~akpm/linux/dirsync/e2fsprogs-1.26.patch

Patch against util-linux-2.11n:
        http://www.zip.com.au/~akpm/linux/dirsync/util-linux-2.11n.patch


The kernel patch includes implementations for ext2 and ext3. It's
pretty simple.

- When dirsync is in operation against a directory, the following operations
  are synchronous within that directory:  create, link, unlink, symlink,
  mkdir, rmdir, mknod, rename (synchronous if either the source or dest
  directory is dirsync).

- dirsync is a subset of sync.  So `mount -o sync' or `chattr +S'
  give you everything which `mount -o dirsync' or `chattr +D' gives,
  plus synchronous file writes.

- ext2's inode.i_attr_flags is unused, and is removed.

- mount /dev/foo /mnt/bar -o dirsync  works as expected.

- An ext2 or ext3 directory tree can be set dirsync with `chattr +D -R'.

- dirsync is maintained as new directories are created under
  a `chattr +D' directory.  Like `chattr +S'.

- Other filesystems can trivially be taught about dirsync.  It's just
  a matter of replacing `IS_SYNC(inode)' with `IS_DIRSYNC(inode)' in
  the directory update functions.  IS_SYNC will still be honoured when
  IS_DIRSYNC is used.

- Non-directory files do not have their dirsync flag propagated.  So
  an S_ISREG file which is created inside a dirsync directory will not
  have its dirsync bit set.  chattr needs to do this as well.

- There was a bit of version skew between e2fsprogs' idea of the
  inode flags and the kernel's.  That is sorted out here.

- `lsattr' shows the dirsync flag as "D".  The letter "D" was
  previously being used for Compressed_Dirty_File.  I changed
  Compressed_Dirty_File to use "Z".  Is that OK?

The mount(2) manpage needs to be taught about MS_DIRSYNC.

Spot the difference:

aops.readpage
aops.readpages
aops.writepage
aops.writeback_mapping

The patch renames `writeback_mapping' to `writepages'

Turn on multipage no-buffers reads for ext3.

Multipage BIO writeout from the pagecache.

It's pretty much the same as multipage reads.  It falls back to buffers
if things got complex.

The write case is a little more complex because it handles pages which
have buffers and pages which do not.  If the page didn't have buffers
this code does not add them.

Implements BIO-based multipage reads into the pagecache, and turns this
on for ext2.

CPU load for `cat large_file > /dev/null' is reduced by approximately
15%.  Similar reductions for tiobench with a single thread.  (Earlier
claims of 25% were exaggerated - they were measured with slab debug
enabled.  But 15% isn't bad for a load which is dominated by copy_*_user
costs).

With 2, 4 and 8 tiobench threads, throughput is increased as well, which was
unexpected.  It's due to request queue weirdness.  (Generally the
request queueing is doing bad things under certain workloads - that's a
separate issue.)

BIOs of up to 64 kbytes are assembled and submitted for readahead and
for single-page reads.  So the work involved in reading 32 pages has gone
from:

	- allocate and attach 32 buffer_heads
	- submit 32 buffer_heads
	- allocate 32 bios
	- submit 32 bios

to:

	- allocate 2 bios
	- submit 2 bios

These pages never have buffers attached.  Buffers will be attached
later if the application writes to these pages (file overwrite).

The first version of this code (in the "delayed allocation" patches)
tries to handle everything - bios which start mid-page, bios which end
mid-page and pages which are covered by multiple bios.  It is very
complex code and in fact appears to be incorrect: out-of-order BIO
completion could cause a page to come unlocked at the wrong time.

This implementation is much simpler: if things get complex, it just
falls back to the buffer-based block_read_full_page(), which isn't
going away, and which understands all that complexity.  There's no
point in doing this in two places.

This code will bypass the buffer layer for

 - fully-mapped pages which are on-disk contiguous.

 - fully unmapoped pages (holes)

 - partially unmapped pages, where the unmappedness is at the end of
   the page (end-of-file).

and everything else falls back to buffers.

This means that with blocksize == PAGE_CACHE_SIZE, 100% of pages are
handed direct to BIO.  With a heavy 10-minute dbench run on 4k
PAGE_CACHE_SIZE and 1k blocks, 95% of pages were handed direct to BIO.
Almost all of the other 5% were passed to block_read_full_page()
because they were already partially uptodate from an earlier sub-page
write().  This ratio will fall if PAGE_CACHE_SIZE/blocksize is greater
than four.  But if that's the case, CPU efficiency is far from the main
concern - there are significant seek and bandwidth problems just at 4
blocks per page.

This code will stress out the block layer somewhat - RAID0 doesn't like
multipage BIOs, and there are probably others.  RAID0 seems to struggle
along - readahead fails but read falls back to single-page reads, which
succeed.  Such problems may be worked around by setting MPAGE_BIO_MAX_SIZE
to PAGE_CACHE_SIZE in fs/mpage.c.

It is trivial to enable multipage reads for many other filesystems.  We
can do that after completion of external testing of ext2.

Relax the requirements on the writeback_mapping a_op.

This function is passed the number of pages which it should write.  The
current fs-writeback.c code will get confused if the address_space
writes back more pages than it was asked to.

With this change the address_space may write more pages than required
if that is convenient.  Extent-based fileystems may wish to do this.

Pages which are under writeout to swap are locked, and not
PageWriteback().  So page allocators do not throttle against them in
shrink_caches().

This causes enormous list scans and general coma under really heavy
swapout loads.

One fix would be to teach shrink_cache() to wait on PG_locked for swap
pages.  The other approach is to set both PG_locked and PG_writeback
for swap pages so they can be handled in the same manner as file-backed
pages in shrink_cache().

This patch takes the latter approach.

Fix bug in the loop driver.

When presented with a multipage BIO, loop is overindexing the first
page in the BIO rather than advancing to the second page.  It scribbles
on the backing file and/or on kernel memory.

This happens with multipage BIO-based pagecache I/O and presumably with
O_DIRECT also.

The fix is much-needed with the multipage-BIO patches - using that code
on loop-backed filesystems has rather messy results.

The set_page_dirty() in the ext3_writepage() failure path isn't right.
set_page_dirty() will alter buffer states - it's a "whole page"
dirtying.

__set_page_dirty_buffers() is emitting warnings when it refuses to set
dirty a non-uptodate buffer against a partially-mapped page.

All we want to do in there is to move the page back onto
mapping->dirty_pages, without altering the state of its buffers.

Fix bug in block_truncate_page().

When buffers are attached to an uptodate page, they are marked as
being uptodate.  To preserve buffer/page state coherency.  Dirtiness
is handled in the same way.

But block_truncate_page() assumes that a buffer which is unmapped and
uptodate is over a hole.  That's not the case, and the net effect is
that block_truncate_page() is failing to zero the block outside the
truncation point.

This only happens if the page has a disk mapping but has no attached
buffers on entry to block_truncate_page().  That's never the case in
current kernels, so the problem does not exhibit (it _does_ exhibit
with direct-to-BIO bypass-the-buffers I/O).

There are actually three possible states of buffer mappedness:

- Buffer has a disk mapping            (buffer_mapped(bh) == true)

- buffer is over a hole	               (buffer_mapped(bh) == false)

- don't know.  Need to run get_block() (buffer_mapped(bh) == false)

This ambiguity could be resolved by added another buffer state bit
(BH_mapping_state_known?) but given that we already elide the get_block
calls for the common case (buffer outside i_size) it is unlikely that
the complexity is worthwhile.

- Fix the fix to the fix to the sector_t printing in buffer_io_error()

- A few microoptimisations in buffer.c.  Replace:

	set_buffer_foo(bh);

  with

	if (!buffer_foo(bh))
		set_buffer_foo(bh);

  when buffer_fooness is likely.  To avoid the buslocked rmw, and to
  avoid dirtying a cacheline.


- export write_mapping_buffers() - filesystems which put buffers on
  mapping->private_list need this function for I/O scheduling reasons.

I'm sick of searching my mail archives to find that email addr.

Hello all,
    The following patch fixes two compile warnings 'defined but not used'.
Since the label and int are only used for IPCONFIG_DYNAMIC, appropriate
fixes were made to remove the warnings.

johnpol@2ka.mipt.ru: 40) request_region check, 31-40:
  You say, i'm frezy :)

  	Evgeniy Polyakov ( s0mbre )

johnpol@2ka.mipt.ru: 30) request_region check, 21-30:
  here is one more trivial check.

  	Evgeniy Polyakov ( s0mbre )

Tim Schmielau <tim@physik3.uni-rostock.de>: trivial irq.h comment fix:

  Now THIS is a trivial patch: (though admittedly quite useless;-)

  include/linux/irq.h starts with
    #ifndef __irq_h
  but ends with a comment
    #endif /* __asm_h */

  Tim

Tim Schmielau <tim@physik3.uni-rostock.de>: provide HZ from jiffies.h:
  Most files that include <jiffies.h> also need HZ defined, which is
  quite reasonable. So don't require the to include <asm/param.h>
  themselves.

Rusty Russell <rusty@rustcorp.com.au>: Trivial ALPHA patch to remove minmax macros:
  Change over to standard max and ALIGN macros.

Rusty Russell <rusty@rustcorp.com.au>: Finally squish those chrp_start.c warnings:
  They finally irritated me enough to patch.  2.5, should apply against 2.4.

Peter Chubb <peter@chubb.wattle.id.au>: Fix compilation warning in do_mounts.c:

  	change_floppy() is unused if you don't have the floppy device
  compiled into the kernel --- so why not #ifdef it out?

Rusty Russell <rusty@rustcorp.com.au>: 2.5.17 Warning removal for ppc:
  test_and_set_bit now expect an "unsigned long", so we want
  &spinlock->lock rather than &spinlock (even though they are
  equivalent).

  Rusty.

(Included in 2.4)
Pavel Machek <pavel@ucw.cz>: trivial: vmscan extra {}s:
  Hi!

  Extra { } look ugly, too, they are not consistant with rest of code and I introduced them :-(

(Included in 2.2)
Pavel Machek <pavel@ucw.cz>: CREDITS not sorted properly:
  Hi!

  Please apply,
  									Pavel

Dan Aloni <da-x@gmx.net>: fs_dcache.c - typo:

Christopher Yeoh <cyeoh@samba.org>: (Made -p1 compliant by rusty) SUSv2 semctl compliance:

  The semctl call with SETVAL currently does not set sempid (at the
  moment sempid is only set during a successful semop call). An
  explanation from Geoff Clare of the Open Group regarding why sempid
  should be set during the semctl call:

  "The spec isn't very clear, but there is a statement on the semget()
  page which I think justifies the assumption made by the test.  It says
  that upon creation, the data structure associated with each semaphore
  in the set is not initialised, and that the semctl() function with
  SETVAL or SETALL can be used to initialise each semaphore.

  Therefore semctl() with SETVAL has to set sempid to *something*, and
  since sempid contains the "process ID of the last operation", setting
  it to anything other than the pid of the calling process would mean
  that sempid contained misleading information.  It could be argued that
  setting it to zero would not be misleading, but zero cannot be the
  process ID of a process, and so is not a valid value for sempid anyway."

  The following patch changes semctl so when called with SETVAL
  sempid is set to the pid of the calling process: