When doing large parallel file creates on a 16p machines, large amounts of
time is being spent in _xfs_buf_find(). A system wide profile with perf top
shows this:

          1134740.00 19.3% _xfs_buf_find
           733142.00 12.5% __ticket_spin_lock

The problem is that the hash contains 45,000 buffers, and the hash table width
is only 256 buffers. That means we've got around 200 buffers per chain, and
searching it is quite expensive. The hash table size needs to increase.

Secondly, every time we do a lookup, we promote the buffer we find to the head
of the hash chain. This is causing cachelines to be dirtied and causes
invalidation of cachelines across all CPUs that may have walked the hash chain
recently. hence every walk of the hash chain is effectively a cold cache walk.
Remove the promotion to avoid this invalidation.

The results are:

          1045043.00 21.2% __ticket_spin_lock
           326184.00  6.6% _xfs_buf_find

A 70% drop in the CPU usage when looking up buffers. Unfortunately that does
not result in an increase in performance underthis workload as contention on
the inode_lock soaks up most of the reduction in CPU usage.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>

The b_strat callback is used by xfs_buf_iostrategy to perform additional
checks before submitting a buffer.  It is used in xfs_bwrite and when
writing out delayed buffers.  In xfs_bwrite it we can de-virtualize the
call easily as b_strat is set a few lines above the call to
xfs_buf_iostrategy.  For the delayed buffers the rationale is a bit
more complicated:

 - there are three callers of xfs_buf_delwri_queue, which places buffers
   on the delwri list:
    (1) xfs_bdwrite - this sets up b_strat, so it's fine
    (2) xfs_buf_iorequest.  None of the callers can have XBF_DELWRI set:
	- xlog_bdstrat is only used for log buffers, which are never delwri
	- _xfs_buf_read explicitly clears the delwri flag
	- xfs_buf_iodone_work retries log buffers only
	- xfsbdstrat - only used for reads, superblock writes without the
	  delwri flag, log I/O and file zeroing with explicitly allocated
	  buffers.
	- xfs_buf_iostrategy - only calls xfs_buf_iorequest if b_strat is
	  not set
    (3) xfs_buf_unlock
	- only puts the buffer on the delwri list if the DELWRI flag is
	  already set.  The DELWRI flag is only ever set in xfs_bwrite,
	  xfs_buf_iodone_callbacks, or xfs_trans_log_buf.  For
	  xfs_buf_iodone_callbacks and xfs_trans_log_buf we require
	  an initialized buf item, which means b_strat was set to
	  xfs_bdstrat_cb in xfs_buf_item_init.

Conclusion: we can just get rid of the callback and replace it with
explicit calls to xfs_bdstrat_cb.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDave Chinner <dchinner@redhat.com>
Signed-off-by: NDave Chinner <david@fromorbit.com>

The tracing code can't print flags defined as enums.  Most flags that
we want to print are defines as macros already, but move the few remaining
ones over to make the trace output more useful.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDave Chinner <dchinner@redhat.com>

Get rid of the xfs_buf_pin/xfs_buf_unpin/xfs_buf_ispin helpers and opencode
them in their only callers, just like we did for the inode pinning a while
ago.  Also remove duplicate trace points - the bufitem tracepoints cover
all the information that is present in a buffer tracepoint.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDave Chinner <dchinner@redhat.com>

This allows to see in `ps` and similar tools which kthreads are
allotted to which block device/filesystem, similar to what jbd2
does. As the process name is a fixed 16-char array, no extra
space is needed in tasks.

  PID TTY      STAT   TIME COMMAND
    2 ?        S      0:00 [kthreadd]
  197 ?        S      0:00  \_ [jbd2/sda2-8]
  198 ?        S      0:00  \_ [ext4-dio-unwrit]
  204 ?        S      0:00  \_ [flush-8:0]
 2647 ?        S      0:00  \_ [xfs_mru_cache]
 2648 ?        S      0:00  \_ [xfslogd/0]
 2649 ?        S      0:00  \_ [xfsdatad/0]
 2650 ?        S      0:00  \_ [xfsconvertd/0]
 2651 ?        S      0:00  \_ [xfsbufd/ram0]
 2652 ?        S      0:00  \_ [xfsaild/ram0]
 2653 ?        S      0:00  \_ [xfssyncd/ram0]
Signed-off-by: NJan Engelhardt <jengelh@medozas.de>
Reviewed-by: NDave Chinner <david@fromorbit.com>

There are no more users of this function left in the XFS code
now that we've switched everything to delayed write flushing.
Remove it.
Signed-off-by: NDave Chinner <david@fromorbit.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>

All buffers logged into the AIL are marked as delayed write.
When the AIL needs to push the buffer out, it issues an async write of the
buffer. This means that IO patterns are dependent on the order of
buffers in the AIL.

Instead of flushing the buffer, promote the buffer in the delayed
write list so that the next time the xfsbufd is run the buffer will
be flushed by the xfsbufd. Return the state to the xfsaild that the
buffer was promoted so that the xfsaild knows that it needs to cause
the xfsbufd to run to flush the buffers that were promoted.

Using the xfsbufd for issuing the IO allows us to dispatch all
buffer IO from the one queue. This means that we can make much more
enlightened decisions on what order to flush buffers to disk as
we don't have multiple places issuing IO. Optimisations to xfsbufd
will be in a future patch.

Version 2
- kill XFS_ITEM_FLUSHING as it is now unused.
Signed-off-by: NDave Chinner <david@fromorbit.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>

Currently we define aliases for the buffer flags in various
namespaces, which only adds confusion.  Remove all but the XBF_
flags to clean this up a bit.

Note that we still abuse XFS_B_ASYNC/XBF_ASYNC for some non-buffer
uses, but I'll clean that up later.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDave Chinner <david@fromorbit.com>
Signed-off-by: NAlex Elder <aelder@sgi.com>

xfs_buf_iomove() uses xfs_caddr_t as it's parameter types, but it doesn't
care about the signedness of the variables as it is just copying the
data. Change the prototype to use void * so that we don't get sign
warnings at call sites.
Signed-off-by: NDave Chinner <david@fromorbit.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>

Move xfsbdstrat and xfs_bdstrat_cb from xfs_lrw.c and xfs_bioerror
and xfs_bioerror_relse from xfs_rw.c into xfs_buf.c.  This also
means xfs_bioerror and xfs_bioerror_relse can be marked static now.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NAlex Elder <aelder@sgi.com>

Fold XFS_bwrite into it's only caller, xfs_bwrite and move it into
xfs_buf.c instead of leaving it as a fairly large inline function.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NAlex Elder <aelder@sgi.com>

Don't bother using XFS_bwrite as it doesn't provide much code for
our use case.  Instead opencode it and fold xlog_bdstrat_cb into the
new xlog_bdstrat helper.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NAlex Elder <aelder@sgi.com>

Change all async metadata buffers to use [READ|WRITE]_META I/O types
so that the I/O doesn't get issued immediately. This allows merging of
adjacent metadata requests but still prioritises them over bulk data.
This shows a 10-15% improvement in sequential create speed of small
files.

Don't include the log buffers in this classification - leave them as
sync types so they are issued immediately.
Signed-off-by: NDave Chinner <dgc@sgi.com>
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NAlex Elder <aelder@sgi.com>

Convert the old xfs tracing support that could only be used with the
out of tree kdb and xfsidbg patches to use the generic event tracer.

To use it make sure CONFIG_EVENT_TRACING is enabled and then enable
all xfs trace channels by:

   echo 1 > /sys/kernel/debug/tracing/events/xfs/enable

or alternatively enable single events by just doing the same in one
event subdirectory, e.g.

   echo 1 > /sys/kernel/debug/tracing/events/xfs/xfs_ihold/enable

or set more complex filters, etc. In Documentation/trace/events.txt
all this is desctribed in more detail.  To reads the events do a

   cat /sys/kernel/debug/tracing/trace

Compared to the last posting this patch converts the tracing mostly to
the one tracepoint per callsite model that other users of the new
tracing facility also employ.  This allows a very fine-grained control
of the tracing, a cleaner output of the traces and also enables the
perf tool to use each tracepoint as a virtual performance counter,
     allowing us to e.g. count how often certain workloads git various
     spots in XFS.  Take a look at

    http://lwn.net/Articles/346470/

for some examples.

Also the btree tracing isn't included at all yet, as it will require
additional core tracing features not in mainline yet, I plan to
deliver it later.

And the really nice thing about this patch is that it actually removes
many lines of code while adding this nice functionality:

 fs/xfs/Makefile                |    8
 fs/xfs/linux-2.6/xfs_acl.c     |    1
 fs/xfs/linux-2.6/xfs_aops.c    |   52 -
 fs/xfs/linux-2.6/xfs_aops.h    |    2
 fs/xfs/linux-2.6/xfs_buf.c     |  117 +--
 fs/xfs/linux-2.6/xfs_buf.h     |   33
 fs/xfs/linux-2.6/xfs_fs_subr.c |    3
 fs/xfs/linux-2.6/xfs_ioctl.c   |    1
 fs/xfs/linux-2.6/xfs_ioctl32.c |    1
 fs/xfs/linux-2.6/xfs_iops.c    |    1
 fs/xfs/linux-2.6/xfs_linux.h   |    1
 fs/xfs/linux-2.6/xfs_lrw.c     |   87 --
 fs/xfs/linux-2.6/xfs_lrw.h     |   45 -
 fs/xfs/linux-2.6/xfs_super.c   |  104 ---
 fs/xfs/linux-2.6/xfs_super.h   |    7
 fs/xfs/linux-2.6/xfs_sync.c    |    1
 fs/xfs/linux-2.6/xfs_trace.c   |   75 ++
 fs/xfs/linux-2.6/xfs_trace.h   | 1369 +++++++++++++++++++++++++++++++++++++++++
 fs/xfs/linux-2.6/xfs_vnode.h   |    4
 fs/xfs/quota/xfs_dquot.c       |  110 ---
 fs/xfs/quota/xfs_dquot.h       |   21
 fs/xfs/quota/xfs_qm.c          |   40 -
 fs/xfs/quota/xfs_qm_syscalls.c |    4
 fs/xfs/support/ktrace.c        |  323 ---------
 fs/xfs/support/ktrace.h        |   85 --
 fs/xfs/xfs.h                   |   16
 fs/xfs/xfs_ag.h                |   14
 fs/xfs/xfs_alloc.c             |  230 +-----
 fs/xfs/xfs_alloc.h             |   27
 fs/xfs/xfs_alloc_btree.c       |    1
 fs/xfs/xfs_attr.c              |  107 ---
 fs/xfs/xfs_attr.h              |   10
 fs/xfs/xfs_attr_leaf.c         |   14
 fs/xfs/xfs_attr_sf.h           |   40 -
 fs/xfs/xfs_bmap.c              |  507 +++------------
 fs/xfs/xfs_bmap.h              |   49 -
 fs/xfs/xfs_bmap_btree.c        |    6
 fs/xfs/xfs_btree.c             |    5
 fs/xfs/xfs_btree_trace.h       |   17
 fs/xfs/xfs_buf_item.c          |   87 --
 fs/xfs/xfs_buf_item.h          |   20
 fs/xfs/xfs_da_btree.c          |    3
 fs/xfs/xfs_da_btree.h          |    7
 fs/xfs/xfs_dfrag.c             |    2
 fs/xfs/xfs_dir2.c              |    8
 fs/xfs/xfs_dir2_block.c        |   20
 fs/xfs/xfs_dir2_leaf.c         |   21
 fs/xfs/xfs_dir2_node.c         |   27
 fs/xfs/xfs_dir2_sf.c           |   26
 fs/xfs/xfs_dir2_trace.c        |  216 ------
 fs/xfs/xfs_dir2_trace.h        |   72 --
 fs/xfs/xfs_filestream.c        |    8
 fs/xfs/xfs_fsops.c             |    2
 fs/xfs/xfs_iget.c              |  111 ---
 fs/xfs/xfs_inode.c             |   67 --
 fs/xfs/xfs_inode.h             |   76 --
 fs/xfs/xfs_inode_item.c        |    5
 fs/xfs/xfs_iomap.c             |   85 --
 fs/xfs/xfs_iomap.h             |    8
 fs/xfs/xfs_log.c               |  181 +----
 fs/xfs/xfs_log_priv.h          |   20
 fs/xfs/xfs_log_recover.c       |    1
 fs/xfs/xfs_mount.c             |    2
 fs/xfs/xfs_quota.h             |    8
 fs/xfs/xfs_rename.c            |    1
 fs/xfs/xfs_rtalloc.c           |    1
 fs/xfs/xfs_rw.c                |    3
 fs/xfs/xfs_trans.h             |   47 +
 fs/xfs/xfs_trans_buf.c         |   62 -
 fs/xfs/xfs_vnodeops.c          |    8
 70 files changed, 2151 insertions(+), 2592 deletions(-)
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NAlex Elder <aelder@sgi.com>

Currently the low-level buffer cache interfaces are highly confusing
as we have a _flags variant of each that does actually respect the
flags, and one without _flags which has a flags argument that gets
ignored and overriden with a default set.  Given that very few places
use the default arguments get rid of the duplication and convert all
callers to pass the flags explicitly.  Also remove the now confusing
_flags postfix.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDave Chinner <david@fromorbit.com>
Signed-off-by: NAlex Elder <aelder@sgi.com>

Currently we unconditionally issue a flush from xfs_free_buftarg, but
since 2.6.29-rc1 this gives a warning in the style of

	end_request: I/O error, dev vdb, sector 0
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NEric Sandeen <sandeen@sandeen.net>
Signed-off-by: NFelix Blyakher <felixb@sgi.com>

Currently we unconditionally issue a flush from xfs_free_buftarg, but
since 2.6.29-rc1 this gives a warning in the style of

	end_request: I/O error, dev vdb, sector 0
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NEric Sandeen <sandeen@sandeen.net>
Signed-off-by: NFelix Blyakher <felixb@sgi.com>

Code does nothing so remove it.
Reviewed-by: NChristoph Hellwig <hch@infradead.org>
Signed-off-by: NLachlan McIlroy <lachlan@sgi.com>

Replace the b_fspriv pointer and it's ugly accessors with a properly types
xfs_mount pointer.  Also switch log reocvery over to it instead of using
b_fspriv for the mount pointer.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDave Chinner <david@fromorbit.com>
Signed-off-by: NLachlan McIlroy <lachlan@sgi.com>

xfs_buf_iostart is a "shared" helper for xfs_buf_read_flags,
xfs_bawrite, and xfs_bdwrite - except that there isn't much shared
code but rather special cases for each caller.

So remove this function and move the functionality to the caller.
xfs_bawrite and xfs_bdwrite are now big enough to be moved out of
line and the xfs_buf_read_flags is moved into a new helper called
_xfs_buf_read.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDave Chinner <david@fromorbit.com>
Signed-off-by: NNiv Sardi <xaiki@sgi.com>

Currently we disable barriers as soon as we get a buffer in xlog_iodone
that has the XBF_ORDERED flag cleared.  But this can be the case not only
for buffers where the barrier failed, but also the first buffer of a
split log write in case of a log wraparound.  Due to the disabled
barriers we can easily get directory corruption on unclean shutdowns.
So instead of using this check add a new buffer flag for failed barrier
writes.

This is a regression vs 2.6.26 caused by patch to use the right macro
to check for the ORDERED flag, as we previously got true returned for
every buffer.

Thanks to Toei Rei for reporting the bug.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NEric Sandeen <sandeen@sandeen.net>
Reviewed-by: NDavid Chinner <david@fromorbit.com>
Signed-off-by: NTim Shimmin <tes@sgi.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The xfs_buf_t b_iodonesema is really just a semaphore that wants to be a
completion. Change it to a completion and remove the last user of the
sema_t from XFS.

SGI-PV: 981498

SGI-Modid: xfs-linux-melb:xfs-kern:31815a
Signed-off-by: NDavid Chinner <david@fromorbit.com>
Signed-off-by: NLachlan McIlroy <lachlan@sgi.com>

Currently closing the rt/log block device is done in the wrong spot, and
far too early. So revampt it:

- xfs_blkdev_put moved out of xfs_free_buftarg into the caller so that

it is done after tearing down the buftarg completely.

- call to xfs_unmountfs_close moved from xfs_mountfs into caller so

that it's done after tearing down the filesystem completely.

- xfs_unmountfs_close is renamed to xfs_close_devices and made static

in xfs_super.c

- opening of the block devices is split into a helper xfs_open_devices

that is symetric in use to xfs_close_devices

- xfs_unmountfs can now lose struct cred

- error handling around device opening sanitized in xfs_fs_fill_super

SGI-PV: 981951
SGI-Modid: xfs-linux-melb:xfs-kern:31193a
Signed-off-by: NChristoph Hellwig <hch@infradead.org>
Signed-off-by: NDavid Chinner <dgc@sgi.com>
Signed-off-by: NLachlan McIlroy <lachlan@sgi.com>

When we have multiple buffers in a single page for a blocksize == pagesize
filesystem we might overwrite the page contents if two callers hit it
shortly after each other. To prevent that we need to keep the page locked
until I/O is completed and the page marked uptodate.

Thanks to Eric Sandeen for triaging this bug and finding a reproducible
testcase and Dave Chinner for additional advice.

This should fix kernel.org bz #10421.
Tested-by: NEric Sandeen <sandeen@sandeen.net>

SGI-PV: 981813
SGI-Modid: xfs-linux-melb:xfs-kern:31173a
Signed-off-by: NChristoph Hellwig <hch@infradead.org>
Signed-off-by: NDavid Chinner <dgc@sgi.com>
Signed-off-by: NLachlan McIlroy <lachlan@sgi.com>

xfs_bdwrite() cannot return an error; it only queues buffers to the
delayed write list and as such never encounters anything that can fail.
Mark it void.

SGI-PV: 980084
SGI-Modid: xfs-linux-melb:xfs-kern:30825a
Signed-off-by: NDavid Chinner <dgc@sgi.com>
Signed-off-by: NNiv Sardi <xaiki@sgi.com>
Signed-off-by: NLachlan McIlroy <lachlan@sgi.com>

There is no need to lock any page in xfs_buf.c because we operate on our
own address_space and all locking is covered by the buffer semaphore. If
we ever switch back to main blockdeive address_space as suggested e.g. for
fsblock with a similar scheme the locking will have to be totally revised
anyway because the current scheme is neither correct nor coherent with
itself.

SGI-PV: 971186
SGI-Modid: xfs-linux-melb:xfs-kern:30156a
Signed-off-by: NChristoph Hellwig <hch@infradead.org>
Signed-off-by: NLachlan McIlroy <lachlan@sgi.com>

SGI-PV: 971596
SGI-Modid: xfs-linux-melb:xfs-kern:29902a
Signed-off-by: NLachlan McIlroy <lachlan@sgi.com>

There is no need to lock any page in xfs_buf.c because we operate on our
own address_space and all locking is covered by the buffer semaphore. If
we ever switch back to main blockdeive address_space as suggested e.g. for
fsblock with a similar scheme the locking will have to be totally revised
anyway because the current scheme is neither correct nor coherent with
itself.

SGI-PV: 971186
SGI-Modid: xfs-linux-melb:xfs-kern:29845a
Signed-off-by: NChristoph Hellwig <hch@infradead.org>
Signed-off-by: NLachlan McIlroy <lachlan@sgi.com>
Signed-off-by: NTim Shimmin <tes@sgi.com>

Many block drivers (aoe, iscsi) really want refcountable pages in bios,
which is what almost everyone send down. XFS unfortunately has a few
places where it sends down buffers that may come from kmalloc, which
breaks them.

Fix the places that use kmalloc()d buffers.

SGI-PV: 964546
SGI-Modid: xfs-linux-melb:xfs-kern:28562a
Signed-Off-By: NChristoph Hellwig <hch@infradead.org>
Signed-off-by: NDavid Chinner <dgc@sgi.com>
Signed-off-by: NTim Shimmin <tes@sgi.com>

SGI-PV: 963465
SGI-Modid: xfs-linux-melb:xfs-kern:28414a
Signed-off-by: NTim Shimmin <tes@sgi.com>
Signed-off-by: NLachlan McIlroy <lachlan@sgi.com>

The {test,set,clear}_bit() operations take a bit index for the bit to
operate on. The XBT_* flags are defined as bit fields which is incorrect,
not to mention the way the bit fields are enumerated is broken too. This
was only working by chance.

Fix the definitions of the flags and make the code using them use the
{test,set,clear}_bit() operations correctly.

SGI-PV: 958639
SGI-Modid: xfs-linux-melb:xfs-kern:27565a
Signed-off-by: NDavid Chinner <dgc@sgi.com>
Signed-off-by: NTim Shimmin <tes@sgi.com>

SGI-PV: 955302
SGI-Modid: xfs-linux-melb:xfs-kern:26749a
Signed-off-by: NEric Sandeen <sandeen@sandeen.net>
Signed-off-by: NNathan Scott <nathans@sgi.com>
Signed-off-by: NTim Shimmin <tes@sgi.com>

SGI-PV: 955302
SGI-Modid: xfs-linux-melb:xfs-kern:26746a
Signed-off-by: NEric Sandeen <sandeen@sandeen.net>
Signed-off-by: NNathan Scott <nathans@sgi.com>
Signed-off-by: NTim Shimmin <tes@sgi.com>

flags from iclog buffers before submitting them for writing.

SGI-PV: 954772
SGI-Modid: xfs-linux-melb:xfs-kern:26605a
Signed-off-by: NNathan Scott <nathans@sgi.com>

Signed-off-by: NJörn Engel <joern@wohnheim.fh-wedel.de>
Signed-off-by: NAdrian Bunk <bunk@stusta.de>

finally.

SGI-PV: 947038
SGI-Modid: xfs-linux-melb:xfs-kern:24866a
Signed-off-by: NNathan Scott <nathans@sgi.com>

contention between filesystems and prevent deadlocks between filesystems
when a flush dependency exists between them.

SGI-PV: 947098
SGI-Modid: xfs-linux-melb:xfs-kern:24844a
Signed-off-by: NDavid Chinner <dgc@sgi.com>
Signed-off-by: NNathan Scott <nathans@sgi.com>

boilerplate.

SGI-PV: 913862
SGI-Modid: xfs-linux:xfs-kern:23903a
Signed-off-by: NNathan Scott <nathans@sgi.com>

replace PBF_NONE with an inverted PBF_DONE, so it's like all the other
flags.

SGI-PV: 942609
SGI-Modid: xfs-linux:xfs-kern:199136a
Signed-off-by: NChristoph Hellwig <hch@sgi.com>
Signed-off-by: NNathan Scott <nathans@sgi.com>

writes.  In addition flush the disk cache on fsync if the sync cached
operation didn't sync the log to disk (this requires some additional
bookeping in the transaction and log code). If the device doesn't claim to
support barriers, the filesystem has an extern log volume or the trial
superblock write with barriers enabled failed we disable barriers and
print a warning.  We should probably fail the mount completely, but that
could lead to nasty boot failures for the root filesystem.  Not enabled by
default yet, needs more destructive testing first.

SGI-PV: 912426
SGI-Modid: xfs-linux:xfs-kern:198723a
Signed-off-by: NChristoph Hellwig <hch@sgi.com>
Signed-off-by: NNathan Scott <nathans@sgi.com>