This patch moves some basic per-CPU static information (minimum frequency,
maximum frequency and maximum transition latency) into a struct
cpufreq_cpuinfo. This offers a much cleaner struct cpufreq_driver and
struct cpufreq_policy.

Kill unused variable and simplify assembly portion a bit...

gcc3.2 is a bit more pedantic...

sr_ioctl.c uses virt_to_phys, which is defined in asm/io.h.
On x86, this accidentally works, due to other indirect includes,
but on Alpha results in a link error.

This fixes one more threaded-coredumps detail reported by the glibc
people: all threads taken down by the coredump code should report the
proper exit code.  We can do this rather easily via the group_exit
mechanism.  'Other' threads used to report SIGKILL, which was highly
confusing as the shell often displayed the 'Killed' message instead of a
'Segmentation fault' message.

Another missing bit was the 0x80 bit set in the exit status for all
threads, if the coredump was successful.  (it's safe to set this bit in
->sig->group_exit_code in an unlocked way because all threads are
artificially descheduled by the coredump code.)

Moves console_loglevel & friends to an array, as sysctl expects.

Makefiles no longer need to include Rules.make, which is currently an
empty file.  This patch removes it from the remaining Makefiles, and
removes the empty Rules.make file.

Makefiles no longer need to include Rules.make, which is currently an
empty file.  This patch removes it from the drivers tree Makefiles.

Makefiles no longer need to include Rules.make, which is currently an
empty file.  This patch removes it from the arch tree Makefiles.

This contains the following changes for the SCSI tape driver in 2.5.51:
- fix module bugs that prevent finding any devices
- allow opening a device with O_NONBLOCK | O_RDWR even if the tape in drive
  is write protected

Remove the unused vm_area_struct.vm_raend.

If someone wants to tune per-VMA readaround then they can alter
vma->vm_file->f_ra.ra_pages.

It is missing a brelse() on an error path.

Fetch the next cacheline as we're counting up the fields in this one.

The optimisation for synchronous mounts was only correct for S_ISREG
files.  Directories do not pass through generic_osync_inode() and we
still need to synchronously write out their indirect blocks.

In PAE mode there is a 4-byte gap and they're not aligning correctly.

From Hugh.

Be consistent in deciding when we are below the zone allocation
thresholds.

From Hugh.

Be more explicit in the "can we sleep" test.  It doesn't change
anything unless someone is performing __GFP_IO && !__GFP_WAIT
allocations, which is nonsensical.

A little cleanup suggested by Chris Mason or Al Viro.

Quite a number of codepaths are testing whether a superblock has a
non-null ->s_op pointer.  We can remove all those by making sure that
all superblocks have a valid ->s_op.

madvise_willneed() currently has a very strange check on how much readahead
it is prepared to do.

  It is based on the user's rss limit.  But this is usually enormous, and
  the user isn't necessarily going to map all that memory at the same time
  anyway.

  And the logic is wrong - it is comparing rss (which is in bytes) with
  `end - start', which is in pages.

  And it returns -EIO on error, which is not mentioned in the Open Group
  spec and doesn't make sense.


This patch takes it all out and applies the same upper limit as is used in
sys_readahead() - half the inactive list.

This ad-hoc assertion is no longer true.  If all zones are in the `all
unreclaimable' state it can trigger.  When testing with a tiny amount
of physical memory.

readahead allocates all the pages before starting I/O.  Potentially bad
if someone is performing huge reads with madvise or sys_readahead().

So the patch just busts that up into two-megabyte units.

generic_file_write()'s rlimit checks are preventing writes to large
offsets into blockdevs:

# ulimit -f 10000
# dd if=/dev/zero of=/dev/sde5 bs=1k count=1 seek=1000000
zsh: file size limit exceeded

So don't apply that check if it's a blockdev.

The patch also caches the S_ISBLK result in a local.

From Andreas Dilger.

Additional sanity checks in the ext2 and ext3 block allocators: if
someone tries to free a negative number of blocks, detect and handle
that rather than wrecking the fs.

Patch from "Juan M. de la Torre" <jmtorre@gmx.net>

If the requested align is PAGE_SIZE, it is impossible to merge with the
previous allocation request, because the allocated area must begin in a
page boundary.

Prevents children from inheriting mlockall(MCL_FUTURE).
Standards-friendly, and 2.4 has it.

current->flags:PF_SYNC was a hack I added because I didn't want to
change all ->writepage implementations.

It's foul.  And it means that if someone happens to run direct page
reclaim within the context of (say) sys_sync, the writepage invokations
from the VM will be treated as "data integrity" operations, not "memory
cleansing" operations, which would cause latency.

So the patch removes PF_SYNC and adds an extra arg to a_ops->writepage.
 It is the `writeback_control' structure which contains the full context
information about why writepage was called.

The initial version of this patch just passed in a bare `int sync', but
the XFS team need more info so they can perform writearound from within
page reclaim.

The patch also adds writeback_control.for_reclaim, so writepage
implementations can inspect that to work out the call context rather
than peeking at current->flags:PF_MEMALLOC.

Under rare conditions (filesystem corruption, really) it is possible
for ext3_dirty_inode() to require _two_ blocks for the transaction: one
for the inode and one to update the superblock - to set
EXT3_FEATURE_RO_COMPAT_LARGE_FILE.  This causes the filesystem to go
BUG.

So reserve an additional block for that eventuality.

Fixes the problem identified by Miles Bader on extremely small zones:
calling hash_long with `bits = 0' is treated as `bits = 32'.

So don't permit the zone to have a one-slot waitqueue hashtable.

This allows us to control the aggressiveness of the lower-zone defense
algorithm.  The `incremental min'.  For workloads which are using a
serious amount of mlocked memory, a few megabytes is not enough.

So the `lower_zone_protection' tunable allows the administrator to
increase the amount of protection which lower zones receive against
allocations which _could_ use higher zones.

The default value of lower_zone_protection is zero, giving unchanged
behaviour.  We should not normally make large amounts of memory
unavailable for pagecache just in case someone mlocks many hundreds of
megabytes.

I've revisited all the superblock->inode->page writeback paths.  There
were several silly things in there, and things were not as clear as they
could be.

scenario 1: create and dirty a MAP_SHARED segment over a sparse file,
then exit.

  All the memory turns into dirty pagecache, but the kupdate function
  only writes it out at a trickle - 4 megabytes every thirty seconds.
  We should sync it all within 30 seconds.

  What's happening is that when writeback tries to write those pages,
  the filesystem needs to instantiate new blocks for them (they're over
  holes).  The filesystem runs mark_inode_dirty() within the writeback
  function.

  This redirtying of the inode while we're writing it out triggers
  some livelock avoidance code in __sync_single_inode().  That function
  says "ah, someone redirtied the file while I was writing it.  Let's
  move the file to the new end of the superblock dirty list and write
  it out later." Problem is, writeback dirtied the inode itself.

  (It is rather silly that mark_inode_dirty() sets I_DIRTY_PAGES when
  clearly no pages have been dirtied.  Fixing that up would be a
  largish work, so work around it here).

  So this patch just removes the livelock avoidance from
  __sync_single_inode().  It is no longer needed anyway - writeback
  livelock is now avoided (in all writeback paths) by writing a finite
  number of pages.

scenario 2: an application is continuously dirtying a 200 megabyte
file, and your disk has a bandwidth of less than 40 megabytes/sec.

  What happens is that once 30 seconds passes, pdflush starts writing
  out the file.  And because that writeout will take more than five
  seconds (a `kupdate' interval), pdflush just keeps writing it out
  forever - continuous I/O.

  What we _want_ to happen is that the 200 megabytes gets written,
  and then IO stops for thirty seconds (minus the writeout period).  So
  the file is fully synced every thirty seconds.

The patch solves this by using mapping->io_pages more intelligently.
When the time comes to write the file out, move all the dirty pages
onto io_pages.  That is a "batch of pages for this kupdate round".
When io_pages is empty, we know we're done.

The address_space_operations.writepages() API is changed!  It now only
needs to write the pages which the caller placed on mapping->io_pages.

This conceptually cleans things up a bit, by more clearly defining the
role of ->io_pages, and the motion between the various mapping lists.

The treatment of sb->s_dirty and sb->s_io is now conceptually identical
to mapping->dirty_pages and mapping->io_pages: move the items-to-be
written onto ->s_io/io_pages, alk walk that list.  As inodes (or pages)
are written, move them over to the clean/locked/dirty lists.

Oh, scenario 3: start an app whcih continuously overwrites a 5 meg
file.  Wait five seconds, start another, wait 5 seconds, start another.
 What we _should_ see is three 5-meg writes, five seconds apart, every
thirty seconds.  That did all sorts of odd things.  It now does the
right thing.

From Rohit

1) hugetlbfs_zero_setup returns ENOMEM in case the request size can
   not be easily handleed.

2) Preference is given to LOW_MEM while freeing the pages from
   hugetlbpage free list.

- /proc/vmstat:pageoutrun and /proc/vmstat:allocstall are always
  identical.  Rework this so that

  - "allocstall" is the number of times a page allocator ran diect reclaim

  - "pageoutrun" is the number of times kswapd ran page reclaim

- Add a new stat: "pgrotated".  The number of pages which were
  rotated to the tail of the LRU for immediate reclaim by
  rotate_reclaimable_page().

- Document things a bit.

Check for usercopy faults in filldir().

ext3_sync_fs will start a commit and will wait on that commit.  This
means that on its return, all journalled file data has been dirtied and
exposed to sync_inodes_sb().  Which is sufficient to fix the umount
data loss problem.

This is infrastructure for fixing the journalled-data ext3 unmount data
loss problem. It was sent for comment to linux-fsdevel a week ago; there
was none.

Add a `sync_fs' superblock operation whose mandate is to perform
filesystem-specific operations to ensure a successful sync.

It is called in two places:

1: fsync_super() - for umount.

2: sys_sync() - for global sync.

In the sys_sync() case we call all the ->write_super() methods first.
write_super() is an async flushing operation.  It should not block.

After that, we call all the ->sync_fs functions.  This is independent
of the state of s_dirt!  That was all confused up before, and in this
patch ->write_super() and ->sync_fs() are quite separate.

With ext3 as an example, the initial ->write_super() will start a
transaction, but will not wait on it.  (But only if s_dirt was set!)

The first ->sync_fs() call will get the IO underway.

The second ->sync_fs() call will wait on the IO.

And we really do need to be this elaborate, because all the testing of
s_dirt in there makes ->write_super() an unreliable way of detecting
when the VFS is trying to sync the filesystem.

Fix a radix-tree bug spotted by Vladimir Saveliev <vs@namesys.com>.

Each step in the radix tree spans six address bits.  So a height=6 tree
spans 36-bits worth of nodes.

On 32-bit machines radix_tree_gang_lookup() doesn't handle this right -
at the 12TB mark it wraps back to zero, and returns pages at quite
wrong indices.

The patch fixes all that up, and tidies a couple of things.

A user-space test harness was developed so that the code can be sanely
tested.  It is at

	http://www.zip.com.au/~akpm/linux/patches/stuff/rtth.tar.gz

Patch from Martin Bligh and Dave Hansen

If a PAE machine has 1G of memory and you set PAGE_OFFSET to 2G, the
kernel will only instantiate a PMD to cover the 2G-3G region.  But
another PMD is needed for the 3G-4G region for the APIC and possibly an
extended vmalloc region.

So the patch changes the code to instantiate PMDs out to the end of
physical memory.

It's a no-op for PAGE_OFFSET=3G, and _could_ be part of the
CONFIG_PAGE_OFFSET patch.  But it seems a reasonable generalisation
anyway.

Ancient patch From Bill Irwin

The patch is intended to show improved information about where the
memory went during OOM-killing events.

- when the OOM killer fails and the system panics, calls
  show_free_areas()

- reorganize show_free_areas() to use for_each_zone()

- add per-cpu stats to show_free_areas()

- tags output from show_free_areas() with node and zone information

fail_writepage() does not work.  Its activate_page() call cannot
activate the page because it is not on the LRU.

So perform that function (more efficiently) in the VM.  Remove
fail_writepage() and, if the filesystem does not implement
->writepage() then activate the page from shrink_list().

A special case is tmpfs, which does have a writepage, but which
sometimes wants to activate the pages anyway.  The most important case
is when there is no swap online and we don't want to keep all those
pages on the inactive list.  So just as a tmpfs special-case, allow
writepage() to return WRITEPAGE_ACTIVATE, and handle that in the VM.

Also, the whole idea of allowing ->writepage() to return -EAGAIN, and
handling that in the caller has been reverted.  If a writepage()
implementation wants to back out and not write the page, it must
redirty the page, unlock it and return zero.  (This is Hugh's preferred
way).

And remove the now-unneeded shmem_writepages() - shmem inodes are
marked as `memory backed' so it will not be called.

And remove the test for non-null ->writepage() in generic_file_mmap().
Memory-backed files _are_ mmappable, and they do not have a
writepage().  It just isn't called.

So the locking rules for writepage() are unchanged.  They are:

- Called with the page locked
- Returns with the page unlocked
- Must redirty the page itself if it wasn't all written.

But there is a new, special, hidden, undocumented, secret hack for
tmpfs: writepage may return WRITEPAGE_ACTIVATE to tell the VM to move
the page to the active list.  The page must be kept locked in this one
case.

There's nopoint in walking through a lot of tmpfs or ramdisk pages when
we're trying to clean memory.  So if a memory-backed inode is
discovered during writeback, skip the entire superblock.