[SCSI] Remove scsi_wait_scan module

scsi_wait_scan was introduced with asynchronous host scanning as a hack
for distributions that weren't using proper udev based wait for root to
appear in their initramfs scripts.  In 2.6.30 Commit

c751085943362143f84346d274e0011419c84202
Author: Rafael J. Wysocki <rjw@sisk.pl>
Date:   Sun Apr 12 20:06:56 2009 +0200

    PM/Hibernate: Wait for SCSI devices scan to complete during resume

Actually broke scsi_wait_scan because it renders
scsi_complete_async_scans() a nop for modular SCSI if you include
scsi_scans.h (which this module does).

The lack of bug reports is sufficient proof that this module is no
longer used.

Cc: Jeff Mahoney <jeffm@suse.de>
Cc: Dave Jones <davej@redhat.com>
Cc: maximilian attems <max@stro.at>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

Conflicts:
	drivers/scsi/scsi_wait_scan.c
victara: Compress kernel with LZO

Signed-off-by: Zhao Wei Liew <zhaoweiliew@gmail.com>
readahead: bump up the default readahead size

Use 512kb max readahead size, and 32kb min readahead size.

The former helps io performance for common workloads.
The latter will be used in the thrashing safe context readahead.

-- Rationals on the 512kb size --

I believe it yields more I/O throughput without noticeably increasing
I/O latency for today's HDD.

For example, for a 100MB/s and 8ms access time HDD, its random IO or
highly concurrent sequential IO would in theory be:

io_size KB  access_time  transfer_time  io_latency   util%   throughput KB/s
4           8             0.04           8.04        0.49%    497.57
8           8             0.08           8.08        0.97%    990.33
16          8             0.16           8.16        1.92%   1961.69
32          8             0.31           8.31        3.76%   3849.62
64          8             0.62           8.62        7.25%   7420.29
128         8             1.25           9.25       13.51%  13837.84
256         8             2.50          10.50       23.81%  24380.95
512         8             5.00          13.00       38.46%  39384.62
1024        8            10.00          18.00       55.56%  56888.89
2048        8            20.00          28.00       71.43%  73142.86
4096        8            40.00          48.00       83.33%  85333.33

The 128KB => 512KB readahead size boosts IO throughput from ~13MB/s to
~39MB/s, while merely increases (minimal) IO latency from 9.25ms to 13ms.

As for SSD, I find that Intel X25-M SSD desires large readahead size
even for sequential reads:

	rasize	1st run		2nd run
	----------------------------------
	  4k	123 MB/s	122 MB/s
	 16k  	153 MB/s	153 MB/s
	 32k	161 MB/s	162 MB/s
	 64k	167 MB/s	168 MB/s
	128k	197 MB/s	197 MB/s
	256k	217 MB/s	217 MB/s
	512k	238 MB/s	234 MB/s
	  1M	251 MB/s	248 MB/s
	  2M	259 MB/s	257 MB/s
   	  4M	269 MB/s	264 MB/s
	  8M	266 MB/s	266 MB/s
The two other impacts of an enlarged readahead size are

- memory footprint (caused by readahead miss)
	Sequential readahead hit ratio is pretty high regardless of max
	readahead size; the extra memory footprint is mainly caused by
	enlarged mmap read-around.
	I measured my desktop:
	- under Xwindow:
		128KB readahead hit ratio = 143MB/230MB = 62%
		512KB readahead hit ratio = 138MB/248MB = 55%
		  1MB readahead hit ratio = 130MB/253MB = 51%
	- under console: (seems more stable than the Xwindow data)
		128KB readahead hit ratio = 30MB/56MB   = 53%
		  1MB readahead hit ratio = 30MB/59MB   = 51%
	So the impact to memory footprint looks acceptable.

- readahead thrashing
	It will now cost 1MB readahead buffer per stream.  Memory tight
	systems typically do not run multiple streams; but if they do
	so, it should help I/O performance as long as we can avoid
	thrashing, which can be achieved with the following patches.

-- Benchmarks by Vivek Goyal --

I have got two paths to the HP EVA and got multipath device setup(dm-3).
I run increasing number of sequential readers. File system is ext3 and
filesize is 1G.
I have run the tests 3 times (3sets) and taken the average of it.

Workload=bsr      iosched=cfq     Filesz=1G   bs=32K
======================================================================
                    2.6.33-rc5                2.6.33-rc5-readahead
job   Set NR  ReadBW(KB/s)   MaxClat(us)    ReadBW(KB/s)   MaxClat(us)
---   --- --  ------------   -----------    ------------   -----------
bsr   3   1   141768         130965         190302         97937.3
bsr   3   2   131979         135402         185636         223286
bsr   3   4   132351         420733         185986         363658
bsr   3   8   133152         455434         184352         428478
bsr   3   16  130316         674499         185646         594311
I ran same test on a different piece of hardware. There are few SATA disks
(5-6) in striped configuration behind a hardware RAID controller.

Workload=bsr      iosched=cfq     Filesz=1G   bs=32K
======================================================================
                    2.6.33-rc5                2.6.33-rc5-readahead
job   Set NR  ReadBW(KB/s)   MaxClat(us)    ReadBW(KB/s)   MaxClat(us)
---   --- --  ------------   -----------    ------------   -----------
bsr   3   1   147569         14369.7        160191         22752
bsr   3   2   124716         243932         149343         184698
bsr   3   4   123451         327665         147183         430875
bsr   3   8   122486         455102         144568         484045
bsr   3   16  117645         1.03957e+06    137485         1.06257e+06
Tested-by: Vivek Goyal <vgoyal@redhat.com>
CC: Jens Axboe <jens.axboe@oracle.com>
CC: Chris Mason <chris.mason@oracle.com>
CC: Peter Zijlstra <a.p.zijlstra@chello.nl>
CC: Martin Schwidefsky <schwidefsky@de.ibm.com>
CC: Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
ARM: 8160/1: drop warning about return_address not using unwind tables

The warning was introduced in 2009 (commit 4bf1fa5a34aa ([ARM] 5613/1:
implement CALLER_ADDRESSx)). The only "problem" here is that
CALLER_ADDRESSx for x > 1 returns NULL which doesn't do much harm.

The drawback of implementing a fix (i.e. use unwind tables to implement CALLER_ADDRESSx) is that much of the unwinder code would need to be marked as not
traceable.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

Conflicts:
	arch/arm/kernel/return_address.c