Multipath has a dependancy on MD_SB_DISKS which is no
longer authoritative.  We change it to use a separately
allocated array.

To cope with a raid0 array with differing sized devices,
raid0 divides an array into "strip zones".
The first zone covers the start of all devices, upto an offset
equal to the size of the smallest device.

The second strip zone covers the remaining devices upto the size of the
next smallest size, etc.

In order to determing which strip zone a given address is in,
the array is logically divided into slices the size of the smallest
zone, and a 'hash' table is created listing the first and, if relevant,
second zone in each slice.

As the smallest slice can be very small (imagine an array with a
76G drive and a 75.5G drive) this hash table can be rather large.

With this patch, we limit the size of the hash table to one page,
at the possible cost of making several probes into the zone list
before we find the correct zone.

We also cope with the possibility that a zone could be larger than
a 32bit sector address would allow.

When starting an array fails, we have to tear it down, but
in some circumstances (particularly autostart_array) the
reference count will be 3, so do_md_stop will fail.

With this patch we only worry about the number of users
is the array has been fully started.

raid0 currently uses vmalloc instead of kmalloc.  This patch
changes to kmalloc.
There is one allocation that can occasionally be very large - the hash_table.
A subsequent patch will address this issue.

Instead of testing last_used (which could change in unusual circumstances) we
test against the bdev that we read frmo, and don't write back to there.

If two drives both fail during a write request, raid5 doesn't
cope properly and will eventually oops.

With this patch, blocks that have already been 'written'
are failed when double drive failure is noticed, as well as
blocks that are about to be written.

Sometimes raid0 and linear are required to take a single page bio that
spans two devices.  We use bio_split to split such a bio into two.

The the same time, bio.h is included by linux/raid/md.h so
we don't included it elsewhere anymore.

We also modify the mergeable_bvec functions to allow a bvec
that doesn't fit if it is the first bvec to be added to
the bio, and be careful never to return a negative length from a
bvec_mergable funciton.

OK, that's it - no callout drivers left, so we drop the warning from
tty_open() and kill the code that handles them in /proc/tty/drivers.

misc cleanup - switched to standard constant names for .subtype in the
drivers that had private equivalents, removed unused ->callout_termios
and friends from the last places where they were defined.

callout removal: isdn

callout removal: cris

callout removal: simserial

callout removal: mips

callout removal: vacserial

callout removal: sicc

callout removal: 8260_uart

callout removal: 8xx_uart

callout removal: amiserial

callout removal: cyclades

callout removal: dz

callout removal: epca

callout removal: esp

callout removal: ip2

callout removal: moxa

callout removal: mxser

callout removal: pcxx

callout removal: rocket

callout removal: serial167

callout removal: synclink

callout removal: synclinkmp

callout removal: synclink_cs

callout removal: macserial

callout removal: pc300

callout removal: chdlc

callout removal: 68328

callout removal: isicom

callout removal: generic_serial

callout removal: tx3912