The actual problem reported was because there wasn't a corresponding
check on transport_classdev.class in the unregister.

However, on closer inspection I also turned up a nasty thinko in the
reference counting.  For reasons best known to the class code authors,
class devices have to obtain their own references to the devices they're
attached to which they release again in their .release routines, so you
have to remember to do a get_device() in the correct place after the
class_device_add().  I put comments in the code so that, hopefully, we
can avoid the problem in future.

Domain Validation is a fairly essential element to the SCSI Parallel
Interface (although if you look very few drivers actually do it).  The
premise is that the Parallel Bus, being a transmission line, might not
be correctly tuned to the transfers you want do perform.  DV probes the
parameters of the transport until it finds a setting that works (for the
interested, see http://www.t10.org/ftp/t10/drafts/sdv/sdv-r08b.pdf)

The current code employs rather simplistic DV heuristics, although those
can be improved over time.  The change in scsi_scan.c is so that DV may
be done easily from the slave_configure routine, which is the most
natural place to begin.

This patch just brings it up to date with the previous transport
attribute patch, moving it to the model where it sets the min/max of the
attribute if asked for something outside its range.  It also only makes
period and offset visible (it doesn't care about any of the others).

This does three things

- Fix the signedness of the bit attributes (otherwise they show up as -1
when on, not 1)
- Make the period adjust to the closest value rather than ignoring
values it doesn't understand.
- Add a visibility field to attributes, so drivers can get rid of
attributes they're never going to care about

This patch adds the ability to quiesce a SCSI device.  The idea is that
user issued commands (including filesystem ones) would get blocked,
while mid-layer and device issued ones would be allowed to proceed.
This is for things like Domain Validation which like to operate on an
otherwise quiet device.

There is one big change: to get all of this to happen correctly,
scsi_do_req() has to queue on the *head* of the request queue, not the
tail as it was doing previously.  The reason is that deferred requests
block the queue, so anything needing executing after a deferred request
has to go in front of it.  I don't think there are any untoward
consequences of this.

Mark S. said that there was another adapter added, and that they changed
the names of some boards.  Here is the updated version.

 - Correct a typo "mvram" -> "nvram".
 - Re-do the PQS/PDS support which I'd #if 0 out.  Should even work on
   multiple-domain boxes now ;-)
 - Move all the nvram definitions to sym_nvram.h (from Gerard's 2.1.19-pre3)
 - hcb_p -> struct sym_hcb *
 - sdev_p -> struct sym_device *
 - Delete a lot of unused macros from sym_misc.h
 - Move READ_BARRIER and WRITE_BARRIER definitions to sym_glue.h
 - SYM_CONF_NVRAM_WRITE_SUPPORT (from Gerard's 2.1.19-pre3).  Not enabled
   yet.
 - Fix some -W warnings (some courtesy of Adrian Bunk).

I submitted a patch last month for the aacraid driver's reset handler.
I left out setting function pointers in the adapter_ops structure for
the adapter_check_health element.

From: 	Moore, Eric Dean <Emoore@lsil.com>

This is an update for the MPT Fusion drivers 2.6 kernel.
Version 3.01.01.

This is a fix for poor performance in RAID Volumes. 
The dvStatus was being cleared for hidden physical disks
when mptscsih_slave_destroy is called.

Also, I have fixed the warning comming from mptscsih_reset_timeouts.

into ppc970.osdl.org:/home/torvalds/v2.5/linux

into redhat.com:/spare/repo/libata-2.5

into ppc970.osdl.org:/home/torvalds/v2.5/linux

into redhat.com:/spare/repo/netconsole-2.5

into ppc970.osdl.org:/home/torvalds/v2.5/linux

into ppc970.osdl.org:/home/torvalds/v2.5/linux

into ppc970.osdl.org:/home/torvalds/v2.5/linux

Cset exclude: akpm@osdl.org|ChangeSet|20040312161945|47751

From: Manfred Spraul <manfred@colorfullife.com>

At present slab is using 2-order allocations for the size-2048 cache.  Of
course, this can affect networking quite seriously.

The patch ensures that slab will never use more than a 1-order allocation
for objects which have a size of less than 2*PAGE_SIZE.

From: Nick Piggin <piggin@cyberone.com.au>

Add a little helper macro for a common list extraction operation in vmscan.c

The current refill logic in refill_inactive_zone() takes an arbitrarily large
number of pages and chops it down to SWAP_CLUSTER_MAX*4, regardless of the
size of the zone.

This has the effect of reducing the amount of refilling of large zones
proportionately much more than of small zones.

We made this change in may 2003 and I'm damned if I remember why.  let's put
it back so we don't truncate the refill count and see what happens.

- prevent nr_scan_inactive from going negative

- compare `count' with SWAP_CLUSTER_MAX, not `max_scan'

- Use ">= SWAP_CLUSTER_MAX", not "> SWAP_CLUSTER_MAX".

From: Nick Piggin <piggin@cyberone.com.au>

Use a "refill_counter" for inactive list scanning, similar to the one used
for active list scanning.  This batches up scanning now that we precisely
balance ratios, and don't round up the amount to be done.

No observed benefits, but I imagine it would lower the acquisition
frequency of the lru locks in some cases, and make codepaths more efficient
in general due to cache niceness.

This is just a random unsubstantiated tuning tweak: don't immediately
throttle page allocators and kwapd when the going is getting heavier: scan a
bit more of the LRU before throttling.

This removes a vestige of the old algorithm.  We don't want to skip zones if
all_zones_ok is true: we've already precalculated which zones need scanning
and this just stops us from ever performing kswapd reclaim from the DMA zone.

As kswapd is now scanning zones in the highmem->normal->dma direction it can
get into competition with the page allocator: kswapd keep on trying to free
pages from highmem, then kswapd moves onto lowmem.  By the time kswapd has
done proportional scanning in lowmem, someone has come in and allocated a few
pages from highmem.  So kswapd goes back and frees some highmem, then some
lowmem again.  But nobody has allocated any lowmem yet.  So we keep on and on
scanning lowmem in response to highmem page allocations.

With a simple `dd' on a 1G box we get:

 r  b   swpd   free   buff  cache   si   so    bi    bo   in    cs us sy wa id
 0  3      0  59340   4628 922348    0    0     4 28188 1072   808  0 10 46 44
 0  3      0  29932   4660 951760    0    0     0 30752 1078   441  1  6 30 64
 0  3      0  57568   4556 924052    0    0     0 30748 1075   478  0  8 43 49
 0  3      0  29664   4584 952176    0    0     0 30752 1075   472  0  6 34 60
 0  3      0   5304   4620 976280    0    0     4 40484 1073   456  1  7 52 41
 0  3      0 104856   4508 877112    0    0     0 18452 1074    97  0  7 67 26
 0  3      0  70768   4540 911488    0    0     0 35876 1078   746  0  7 34 59
 1  2      0  42544   4568 939680    0    0     0 21524 1073   556  0  5 43 51
 0  3      0   5520   4608 976428    0    0     4 37924 1076   836  0  7 41 51
 0  2      0   4848   4632 976812    0    0    32 12308 1092    94  0  1 33 66

Simple fix: go back to scanning the zones in the dma->normal->highmem
direction so we meet the page allocator in the middle somewhere.

 r  b   swpd   free   buff  cache   si   so    bi    bo   in    cs us sy wa id
 1  3      0   5152   3468 976548    0    0     4 37924 1071   650  0  8 64 28
 1  2      0   4888   3496 976588    0    0     0 23576 1075   726  0  6 66 27
 0  3      0   5336   3532 976348    0    0     0 31264 1072   708  0  8 60 32
 0  3      0   6168   3560 975504    0    0     0 40992 1072   683  0  6 63 31
 0  3      0   4560   3580 976844    0    0     0 18448 1073   233  0  4 59 37
 0  3      0   5840   3624 975712    0    0     4 26660 1072   800  1  8 46 45
 0  3      0   4816   3648 976640    0    0     0 40992 1073   526  0  6 47 47
 0  3      0   5456   3672 976072    0    0     0 19984 1070   320  0  5 60 35

Currently kswapd walks across all zones in dma->normal->highmem order,
performing proportional scanning until all zones are OK.  This means that
pressure against ZONE_NORMAL causes unnecessary reclaim of ZONE_HIGHMEM.

To fix that up we change kswapd so that it walks the zones in the
high->normal->dma direction, skipping zones which are OK.  Once it encounters
a zone which needs some reclaim kswapd will perform proportional scanning
against that zone as well as all the succeeding lower zones.

We scan the lower zones even if they have sufficient free pages.  This is
because

a) the lower zone may be above pages_high, but because of the incremental
   min, the lower zone may still not be eligible for allocations.  That's bad
   because cache in that lower zone will then not be scanned at the correct
   rate.

b) pages in this lower zone are usable for allocations against the higher
   zone.  So we do want to san all the relevant zones at an equal rate.

- If max_scan evaluates to zero due to a very small inactive list and high
  `priority' numbers, we don't want to thrlttle yet.

- In balance_pgdat(), we may end up not scanning any pages because all
  zones happened to be above pages_high.  Avoid throttling in this case too.

When page reclaim is working out how many pages to san in a zone (max-scan)
it presently rounds that number up if it looks too small - for work batching.

Problem is, this can result in excessive scanning against small zones which
have few inactive pages.  So remove it.

Not that it is possible for max_scan to be zero.  That's OK - it'll become
non-zero as the priority increases.

Page reclaim is currently a bit schitzo: sometimes we say "go and scan this
many pages and tell me how many pages were freed" and at other times we say
"go and scan this many pages, but stop if you freed this many".

It makes the logic harder to control and to understand.  This patch coverts
everything into the "go and scan this many pages and tell me how many pages
were freed" model.

It doesn't seem to affect performance much either way.

We currently have a problem with the balancing of reclaim between zones: much
more reclaim happens against highmem than against lowmem.

This patch partially fixes this by changing the direct reclaim path so it
does not bale out of the zone walk after having reclaimed sufficient pages
from highmem: go on to reclaim from lowmem regardless of how many pages we
reclaimed from lowmem.

The patch which went in six months or so back which said "only reclaim slab
if we're scanning lowmem pagecache" was wrong.  I must have been asleep at
the time.

We do need to scan slab in response to highmem page reclaim as well.  Because
all the math is based around the total amount of memory in the machine, and
we know that if we're performing highmem page reclaim then the lower zones
have no free memory.

From: Nick Piggin <piggin@cyberone.com.au>

The logic which calculates the numberof pages which were scanned is mucked
up.  Fix.

From: Nick Piggin <piggin@cyberone.com.au>

In try_to_free_pages(), put even pressure on the slab even if we have
reclaimed enough pages from the LRU.

From: Nick Piggin <piggin@cyberone.com.au>

In shrink_slab(), do the multiply before the divide to avoid losing
precision.

From: Nick Piggin <piggin@cyberone.com.au>

If refill_inactive_zone() is running in its dont-reclaim-mapped-memory mode
we are tossing away the referenced infomation on active mapped pages.

So put that info back if we're not going to deactivate the page.

The logic in balance_pgdat() is all bollixed up.

- the incoming arg `nr_pages' should be used to determine if we're being
  asked to free a specific number of pages, not `to_free'.

- local variable `to_free' is not appropriate for the determination of
  whether we failed to bring all zones to appropriate free pages levels.

  Fix this by correctly calculating `all_zones_ok' and then use
  all_zones_ok to determine whether we need to throttle kswapd.

So the logic now is:


	for (increasing priority) {

		all_zones_ok = 1;

		for (all zones) {
			to_reclaim = number of pages to try to reclaim
				     from this zone;
			max_scan = number of pages to scan in this pass
				   (gets larger as `priority' decreases)
			/*
			 * set `reclaimed' to the number of pages which were
			 * actually freed up
			 */
			reclaimed = scan(max_scan pages);
			reclaimed += shrink_slab();

			to_free -= reclaimed;	/* for the `nr_pages>0' case */

			/*
			 * If this scan failed to reclaim `to_reclaim' or more
			 * pages, we're getting into trouble.  Need to scan
			 * some more, and throttle kswapd.   Note that this
			 * zone may now have sufficient free pages due to
			 * freeing activity by some other process.   That's
			 * OK - we'll pick that info up on the next pass
			 * through the loop.
			 */
			if (reclaimed < to_reclaim)
				all_zones_ok = 0;
		}
		if (to_free > 0)
			continue;	/* swsusp: need to do more work */
		if (all_zones_ok)
			break;		/* kswapd is done */
		/*
		 * OK, kswapd is getting into trouble.  Take a nap, then take
		 * another pass across the zones.
		 */
		blk_congestion_wait();
	}

From: Nikita Danilov <Nikita@Namesys.COM>

Now that decision to reclaim mapped memory is taken on the basis of
zone->prev_priority, priority argument is no longer needed.