linux-toradex.git/drivers/md/dm.h, branch v2.6.30-rc5

dm: remove limited barrier support

2009-04-08T23:27:13+00:00

Prepare for full barrier implementation: first remove the restricted support.

Signed-off-by: Mikulas Patocka 
Signed-off-by: Alasdair G Kergon

dm target: remove struct tt_internal

2009-04-02T18:55:28+00:00

The tt_internal is really just a list_head to manage registered target_type
in a double linked list,

Here embed the list_head into target_type directly,
1. to avoid kmalloc/kfree;
2. then tt_internal is really unneeded;

Cc: stable@kernel.org
Signed-off-by: Cheng Renquan 
Signed-off-by: Alasdair G Kergon 
Reviewed-by: Alasdair G Kergon

dm: add name and uuid to sysfs

2009-01-06T03:05:12+00:00

Implement simple read-only sysfs entry for device-mapper block device.

This patch adds a simple sysfs directory named "dm" under block device
properties and implements
	- name attribute (string containing mapped device name)
	- uuid attribute (string containing UUID, or empty string if not set)

The kobject is embedded in mapped_device struct, so no additional
memory allocation is needed for initializing sysfs entry.

During the processing of sysfs attribute we need to lock mapped device
which is done by a new function dm_get_from_kobj, which returns the md
associated with kobject and increases the usage count.

Each 'show attribute' function is responsible for its own locking.

Signed-off-by: Milan Broz 
Signed-off-by: Alasdair G Kergon

dm table: rework reference counting

2009-01-06T03:05:10+00:00

Rework table reference counting.

The existing code uses a reference counter. When the last reference is
dropped and the counter reaches zero, the table destructor is called.
Table reference counters are acquired/released from upcalls from other
kernel code (dm_any_congested, dm_merge_bvec, dm_unplug_all).
If the reference counter reaches zero in one of the upcalls, the table
destructor is called from almost random kernel code.

This leads to various problems:
* dm_any_congested being called under a spinlock, which calls the
  destructor, which calls some sleeping function.
* the destructor attempting to take a lock that is already taken by the
  same process.
* stale reference from some other kernel code keeps the table
  constructed, which keeps some devices open, even after successful
  return from "dmsetup remove". This can confuse lvm and prevent closing
  of underlying devices or reusing device minor numbers.

The patch changes reference counting so that the table destructor can be
called only at predetermined places.

The table has always exactly one reference from either mapped_device->map
or hash_cell->new_map. After this patch, this reference is not counted
in table->holders.  A pair of dm_create_table/dm_destroy_table functions
is used for table creation/destruction.

Temporary references from the other code increase table->holders. A pair
of dm_table_get/dm_table_put functions is used to manipulate it.

When the table is about to be destroyed, we wait for table->holders to
reach 0. Then, we call the table destructor.  We use active waiting with
msleep(1), because the situation happens rarely (to one user in 5 years)
and removing the device isn't performance-critical task: the user doesn't
care if it takes one tick more or not.

This way, the destructor is called only at specific points
(dm_table_destroy function) and the above problems associated with lazy
destruction can't happen.

Finally remove the temporary protection added to dm_any_congested().

Signed-off-by: Mikulas Patocka 
Signed-off-by: Alasdair G Kergon

dm: support barriers on simple devices

2009-01-06T03:05:09+00:00

Implement barrier support for single device DM devices

This patch implements barrier support in DM for the common case of dm linear
just remapping a single underlying device. In this case we can safely
pass the barrier through because there can be no reordering between
devices.

 NB. Any DM device might cease to support barriers if it gets
     reconfigured so code must continue to allow for a possible
     -EOPNOTSUPP on every barrier bio submitted.  - agk

Signed-off-by: Andi Kleen 
Signed-off-by: Mikulas Patocka 
Signed-off-by: Alasdair G Kergon

dm: publish array_too_big

2008-10-21T16:44:57+00:00

Move array_too_big to include/linux/device-mapper.h because it is
used by targets.

Remove the test from dm-raid1 as the number of mirror legs is limited
such that it can never fail.  (Even for stripes it seems rather
unlikely.)

Signed-off-by: Mikulas Patocka 
Signed-off-by: Alasdair G Kergon

dm: publish dm_vcalloc

2008-10-10T12:37:12+00:00

Publish dm_vcalloc in include/linux/device-mapper.h because this function is
used by targets.

Signed-off-by: Mikulas Patocka 
Signed-off-by: Alasdair G Kergon

dm: publish dm_table_unplug_all

2008-10-10T12:37:11+00:00

Publish dm_table_unplug_all in include/linux/device-mapper.h because this
function is used by targets.

Signed-off-by: Mikulas Patocka 
Signed-off-by: Alasdair G Kergon

dm: publish dm_get_mapinfo

2008-10-10T12:37:10+00:00

Publish dm_get_mapinfo in include/linux/device-mapper.h because this function
is used by targets.

Signed-off-by: Mikulas Patocka 
Signed-off-by: Alasdair G Kergon

dm: export struct dm_dev

2008-10-10T12:37:09+00:00

Split struct dm_dev in two and publish the part that other targets need in
include/linux/device-mapper.h.

Signed-off-by: Mikulas Patocka 
Signed-off-by: Alasdair G Kergon