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:

Alexander.Riesen@synopsys.com: xconfig for tulip subsection:
  fixes broken xconfig for tulip drivers.

  P.S. Why the double quotes in comment break it?

Anton Blanchard <anton@samba.org>: Fix autofs on ppc64:

  Define autofs_wqt_t to be an int on ppc64, just like the other mixed
  32/64 bit archs do.

 - Rewritten Artop host chip driver by Vojtech Pavlik. His log entries are:

   Cleanup whitespace.

   Remove superfluous chip entries in chip table.  Remove global variables to
   allow more than one controller.  Remove other forgotten stuff.

   This is a new driver for the Artop (Acard) controllers. It's completely
   untested, as I have never seen the hardware. However, I suspect it is much
   less broken than the previous one ...

   UDMA33 controller cannot detect 80-wire cable.

 - Separate ioctl handling out from ide.c. It's big enough.

 - Move atapi_read and atapi_write to the new atapi module.  Fix the declaration
   of those functions. The data buffer did have the void * type!

 - Separate module handling code out from actual transfer handling code in to a
   new module called main.c. Slowly we are at the stage where the code indeed
   has to be organized logically and not just "sporadically" as was the case
   before.

 - Apply patch by Adam Richter for the ide-scsi.c attach method implementation.
   This particular driver is still broken due to generic SCSI layer issues.

 - Apply true modularization patch for qd65xx.c by Samuel Thibault. Here
   are his notes about it:

   Then, patch-modularize-2.[45] is a proposal for modularizing qd65xx.o. As a
   single module, one can choose to insmod it before being able to do some
   hdparm -p /dev/hd[a-d]. But one can't remove it while tuned, since selectproc
   may be needed.

   I am sorry I wasn't able to test it under 2.5 series, lacking a functionning
   kernel for my test computer, but it seemed to work perfectly under 2.4
   series, and patches are almost the same.

 - Move PCI device id's to where they belong. Patch by Vojtech Pavlik.

 - Don't use BH_Lock in ide-tape.c - somehow this driver scares me sometimes.

o Add 'tag' to request.txt doc
o Add bio design etc discussions

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

They're always the same, so no point in using function pointers.

We rather keep it simple, everything we need is in struct
capi_ctr.

The hardware driver needs to alloc mem anyway, and now can
fill in fields before registering with the CAPI layer.

Basically the same way struct net_device is handled.