md: allow a reshape operation to be reversed.

Currently a reshape operation always progresses from the start
of the array to the end unless the number of devices is being
reduced, in which case it progressed in the opposite direction.

To reverse a partial reshape which changes the number of devices
you can stop the array and re-assemble with the raid-disks numbers
reversed and it will undo.

However for a reshape that does not change the number of devices
it is not possible to reverse the reshape in the middle - you have to
wait until it completes.

So add a 'reshape_direction' attribute with is either 'forwards' or
'backwards' and can be explicitly set when delta_disks is zero.

This will become more important when we allow the data_offset to
change in a reshape.  Then the explicit statement of what direction is
being used will be more useful.

This can be enabled in raid5 trivially as it already supports
reverse reshape and just needs to use a different trigger to request it.

Signed-off-by: NeilBrown <neilb@suse.de>
md: add possibility to change data-offset for devices.

When reshaping we can avoid costly intermediate backup by
changing the 'start' address of the array on the device
(if there is enough room).

So as a first step, allow such a change to be requested
through sysfs, and recorded in v1.x metadata.

(As we didn't previous check that all 'pad' fields were zero,
 we need a new FEATURE flag for this.
 A (belatedly) check that all remaining 'pad' fields are
 zero to avoid a repeat of this)

The new data offset must be requested separately for each device.
This allows each to have a different change in the data offset.
This is not likely to be used often but as data_offset can be
set per-device, new_data_offset should be too.

This patch also removes the 'acknowledged' arg to rdev_set_badblocks as
it is never used and never will be.  At the same time we add a new
arg ('in_new') which is currently always zero but will be used more
soon.

When a reshape finishes we will need to update the data_offset
and rdev->sectors.  So provide an exported function to do that.

Signed-off-by: NeilBrown <neilb@suse.de>
md/raid5:  Use correct data_offset for all IO.

As there can now be two different data_offsets - an 'old' and
a 'new' - we need to carefully choose between them.

Signed-off-by: NeilBrown <neilb@suse.de>
md/raid5: allow for change in data_offset while managing a reshape.

The important issue here is incorporating the different in data_offset
into calculations concerning when we might need to over-write data
that is still thought to be valid.

To this end we find the minimum offset difference across all devices
and add that where appropriate.

Signed-off-by: NeilBrown <neilb@suse.de>
md/raid10: collect some geometry fields into a dedicated structure.

We will shortly be adding reshape support for RAID10 which will
require it having 2 concurrent geometries (before and after).
To make that easier, collect most geometry fields into 'struct geom'
and access them from there.  Then we will more easily be able to add
a second set of fields.

Note that 'copies' is not in this struct and so cannot be changed.
There is little need to change this number and doing so is a lot
more difficult as it requires reallocating more things.
So leave it out for now.

Signed-off-by: NeilBrown <neilb@suse.de>
md: teach sync_page_io about new_data_offset.

Some code in raid1 and raid10 use sync_page_io to
read/write pages when responding to read errors.
As we will shortly support changing data_offset for
raid10, this function must understand new_data_offset.

So add that understanding.

Signed-off-by: NeilBrown <neilb@suse.de>
md: use resync_max_sectors for reshape as well as resync.

Some resync type operations need to act on the address space of the
device, others on the address space of the array.

This only affects RAID10, so it sets resync_max_sectors to the array
size (it defaults to the device size), and that is currently used for
resync only.  However reshape of a RAID10 must be done against the
array size, not device size, so change code to use resync_max_sectors
for both the resync and the reshape cases.
This does not affect RAID5 or RAID1, just RAID10.

Signed-off-by: NeilBrown <neilb@suse.de>
md/raid10: Introduce 'prev' geometry to support reshape.

When RAID10 supports reshape it will need a 'previous' and a 'current'
geometry, so introduce that here.
Use the 'prev' geometry when before the reshape_position, and the
current 'geo' when beyond it.  At other times, use both as
appropriate.

For now, both are identical (And reshape_position is never set).

When we use the 'prev' geometry, we must use the old data_offset.
When we use the current (And a reshape is happening) we must use
the new_data_offset.

Signed-off-by: NeilBrown <neilb@suse.de>
md/raid10: split out interpretation of layout to separate function.

We will soon be interpreting the layout (and chunksize etc) from
multiple places to support reshape.  So split it out into separate
function.

Signed-off-by: NeilBrown <neilb@suse.de>
md/raid10: add reshape support

A 'near' or 'offset' lay RAID10 array can be reshaped to a different
'near' or 'offset' layout, a different chunk size, and a different
number of devices.
However the number of copies cannot change.

Unlike RAID5/6, we do not support having user-space backup data that
is being relocated during a 'critical section'.  Rather, the
data_offset of each device must change so that when writing any block
to a new location, it will not over-write any data that is still
'live'.

This means that RAID10 reshape is not supportable on v0.90 metadata.

The different between the old data_offset and the new_offset must be
at least the larger of the chunksize multiplied by offset copies of
each of the old and new layout. (for 'near' mode, offset_copies == 1).

A larger difference of around 64M seems useful for in-place reshapes
as more data can be moved between metadata updates.
Very large differences (e.g. 512M) seem to slow the process down due
to lots of long seeks (on oldish consumer graded devices at least).

Metadata needs to be updated whenever the place we are about to write
to is considered - by the current metadata - to still contain data in
the old layout.

Signed-off-by: NeilBrown <neilb@suse.de>
crypto: wait for a full jiffy in do_xor_speed

In the existing do_xor_speed(), there is no guarantee that we actually
run do_2() for a full jiffy. We get the current jiffy, then run do_2()
until the next jiffy.

Instead, let's get the current jiffy, then wait until the next jiffy
to start our test.

Signed-off-by: Jim Kukunas <james.t.kukunas@linux.intel.com>
Signed-off-by: NeilBrown <neilb@suse.de>
crypto: disable preemption while benchmarking RAID5 xor checksumming

With CONFIG_PREEMPT=y, we need to disable preemption while benchmarking
RAID5 xor checksumming to ensure we're actually measuring what we think
we're measuring.

Signed-off-by: Jim Kukunas <james.t.kukunas@linux.intel.com>
Signed-off-by: NeilBrown <neilb@suse.de>
lib/raid6: fix test program build

<linux/module.h> drags in headers which are not visible to userspace,
thus breaking the build for the test program.

Signed-off-by: Jim Kukunas <james.t.kukunas@linux.intel.com>
Signed-off-by: NeilBrown <neilb@suse.de>