Revision 1:
  2.4 backport, compiles

Revision 2:
  kgdb

Revision 3:
  Fix bugs

Revision 4:
  change dd->dev to a kdev_t

Revision 5:
  Correct devfs_register call.

Revision 6:
  The dm_get_device in the linear constructor was wrong.

Revision 7:
  Change a couple of GFP_KERNEL allocations to GFP_NOIO

Revision 8:
  The locking when leaving __request was broken.
  
  Split off __deferring()

Revision 9:
  s->table wasn't being set in the snapshot contructor

Revision 10:
  I don't know why dm-ioctl.c was including <linux/compatmac.h>
  rather than <asm/uaccess.h>

Revision 11:
  Four constants:
     DM_DIR,
     DM_MAX_TYPE_NAME,
     DM_NAME_LEN,
     DM_UUID_LEN
  
  Were being declared in device-mapper.h, these are all specific to 
  the ioctl interface, so they've been moved to dm-ioctl.h.  Nobody
  in userland should ever include <linux/device-mapper.h> so remove 
  ifdef __KERNEL guards.

Revision 12:
  No need to validate the parameters if we are doing a
  REMOVE_ALL command.

Revision 13:
  Fluff

Revision 14:
  Mempool version by Christoph Hellwig that holds the free objects
  in an array rather than a list.  This prevents the objects getting
  dirtied, eg, people maybe expecting them to come out of a slab with
  a particular state.

Revision 15:
  Return -ENOTBLK if lookup_device() finds the inode, but it
  is not a block device. [Cristoph Hellwig]

Revision 16:
  get_kdev() was locking _minor_lock rather than
  &_minor_lock. [Heinz Mauelshagen]

Revision 17:
  minor change for dm-strip.c. Tests for correct chunksize before it allocates
  the stripe context. [Heinz Mauelshagen]

Revision 18:
  There's a bug in the dm-stripe.c constructor failing top check if enough
  destinations are handed in. [Heinz Mauelshagen]

Revision 19:
  Give each device its own io mempool to avoid a potential
  deadlock with stacked devices.  [HM + EJT]

Revision 20:
  Let the persistent/non persistent arg to the snapshot constructor
  be case insensitive. [Heinz Mauelshagen]

Revision 21:
  queue_io() was checking the DMF_SUSPENDED flag rather than the new
  DMF_BLOCK_IO flag.  This meant suspend could deadlock under load.

Revision 22:
  dm_suspend(): Stop holding the read lock around the while loop that
  waits for pending io to complete.

Revision 23:
  Add a run_task_queue(&tq_disk) to encourage pending io to flush
  when we're doing a dm_suspend().

Revision 24:
  Don't hook the io until after the target->map function has been
  called.

Revision 25:
  Lift the dm_io allocation out of __map_buffer so that it is outside of
  the read lock.
  
  Hook all io, not just simple mappings.

Revision 26:
  change (struct target_type).use to be an atomic_t.

Revision 27:
  forgot to initialise the atomic_t

Revision 28:
  Use a rw_semaphore in dm_target.c rather than a rwlock_t, just to keep
  in line with dm.c

Revision 29:
  Add an endio method to targets.

Revision 30:
  import dm-iostats.c

Revision 31:
  Update Config.in and Makefile to get dm-iostats building.

Revision 32:
  Typedef a suitable jiffies_t rather than using typeof everywhere.

Revision 33:
  Rename variables that have the word 'jiffies' in them.  No hungarian
  please.

Revision 34:
  Get rid of global _io_lock spinlock.

Revision 35:
  Fluff

Revision 36:
  Fluff

Revision 37:
  Fluff

Revision 38:
  We can't have 2 target types in the same module without breaking the
  automatic loading of target modules.  eg, if 'iostat_avg' is requested
  and not registered the kernel will try and load a module called
  'dm-iostat_avg'.
  
  So this changes the code back to a single target, with an extra
  parameter which states whether we want latency info or not.

Revision 39:
  Changes ic->reads and ic->writes to be atomic_t.

Revision 40:
  Change the target->end_io function to take the rw param.
  
  Use target->end_io rather than hooking in dm-iostats.c
  
  Instead of taking the average of the individual io latencies calculate
  the 'average end_io time' - 'average start time'.  This removes the need
  for passing context (ie. start time) between the map function and the
  end_io function.

Revision 41:
  No longer any need for jiffies_t
  
  target->end_io was only being called when there were zero pending ios.
  
  ti->private wasn't being set.

Revision 42:
  Remove divide by zero possibility from calc_latency().

Revision 43:
  Convert to using uint64_t's for everything. (doesn't yet work).

Revision 44:
  uint64_t -> unsigned long long

Revision 45:
  Return the correct value from calc_latency()
  
  Some stray sector_t's -> unsigned long long

Revision 46:
  Don't let the ioctl interface drop a suspended device.

Revision 47:
  Call dm_put_target_type() *after* calling the destructor.

Revision 48:
  In dm_put_target_type(): There's no need for the lock around the
  atomic_dec_and_test().

Revision 49:
  Fluff

Revision 50:
  printk tgt->error if dm_table_add_target() fails.

Revision 51:
  Just return an error from the error targets map function, rather than
  erroring the buffer_head.

Revision 52:
  Export dm_table_get_mode()