linux.git/drivers/md/dm-sysfs.c, branch v3.17

dm sysfs: fix a module unload race

2014-01-15T04:23:04+00:00

This reverts commit be35f48610 ("dm: wait until embedded kobject is
released before destroying a device") and provides an improved fix.

The kobject release code that calls the completion must be placed in a
non-module file, otherwise there is a module unload race (if the process
calling dm_kobject_release is preempted and the DM module unloaded after
the completion is triggered, but before dm_kobject_release returns).

To fix this race, this patch moves the completion code to dm-builtin.c
which is always compiled directly into the kernel if BLK_DEV_DM is
selected.

The patch introduces a new dm_kobject_holder structure, its purpose is
to keep the completion and kobject in one place, so that it can be
accessed from non-module code without the need to export the layout of
struct mapped_device to that code.

Signed-off-by: Mikulas Patocka 
Signed-off-by: Mike Snitzer 
Cc: stable@vger.kernel.org

dm: wait until embedded kobject is released before destroying a device

2014-01-08T02:01:43+00:00

There may be other parts of the kernel holding a reference on the dm
kobject.  We must wait until all references are dropped before
deallocating the mapped_device structure.

The dm_kobject_release method signals that all references are dropped
via completion.  But dm_kobject_release doesn't free the kobject (which
is embedded in the mapped_device structure).

This is the sequence of operations:
* when destroying a DM device, call kobject_put from dm_sysfs_exit
* wait until all users stop using the kobject, when it happens the
  release method is called
* the release method signals the completion and should return without
  delay
* the dm device removal code that waits on the completion continues
* the dm device removal code drops the dm_mod reference the device had
* the dm device removal code frees the mapped_device structure that
  contains the kobject

Using kobject this way should avoid the module unload race that was
mentioned at the beginning of this thread:
https://lkml.org/lkml/2014/1/4/83

Signed-off-by: Mikulas Patocka 
Signed-off-by: Mike Snitzer 
Cc: stable@vger.kernel.org

Driver core: Constify struct sysfs_ops in struct kobj_type

2010-03-08T01:04:49+00:00

Constify struct sysfs_ops.

This is part of the ops structure constification
effort started by Arjan van de Ven et al.

Benefits of this constification:

 * prevents modification of data that is shared
   (referenced) by many other structure instances
   at runtime

 * detects/prevents accidental (but not intentional)
   modification attempts on archs that enforce
   read-only kernel data at runtime

 * potentially better optimized code as the compiler
   can assume that the const data cannot be changed

 * the compiler/linker move const data into .rodata
   and therefore exclude them from false sharing

Signed-off-by: Emese Revfy 
Acked-by: David Teigland 
Acked-by: Matt Domsch 
Acked-by: Maciej Sosnowski 
Acked-by: Hans J. Koch 
Acked-by: Pekka Enberg 
Acked-by: Jens Axboe 
Acked-by: Stephen Hemminger 
Signed-off-by: Greg Kroah-Hartman

dm: sysfs revert add empty release function to avoid debug warning

2010-02-16T18:43:04+00:00

Revert commit d2bb7df8cac647b92f51fb84ae735771e7adbfa7 at Greg's request.

    Author: Milan Broz 
    Date:   Thu Dec 10 23:51:53 2009 +0000

    dm: sysfs add empty release function to avoid debug warning

    This patch just removes an unnecessary warning:
     kobject: 'dm': does not have a release() function,
     it is broken and must be fixed.

    The kobject is embedded in mapped device struct, so
    code does not need to release memory explicitly here.

Cc: Greg KH 
Signed-off-by: Alasdair G Kergon

dm: rename dm_suspended to dm_suspended_md

2009-12-10T23:52:26+00:00

This patch renames dm_suspended() to dm_suspended_md() and
keeps it internal to dm.
No functional change.

Signed-off-by: Kiyoshi Ueda 
Signed-off-by: Jun'ichi Nomura 
Cc: Mike Anderson 
Signed-off-by: Alasdair G Kergon

dm: sysfs add empty release function to avoid debug warning

2009-12-10T23:51:53+00:00

This patch just removes an unnecessary warning:
 kobject: 'dm': does not have a release() function,
 it is broken and must be fixed.

The kobject is embedded in mapped device struct, so
code does not need to release memory explicitly here.

Cc: stable@kernel.org
Signed-off-by: Milan Broz 
Signed-off-by: Alasdair G Kergon

dm: sysfs add suspended attribute

2009-06-22T09:12:29+00:00

Add a file named 'suspended' to each device-mapper device directory in
sysfs.  It holds the value 1 while the device is suspended.  Otherwise
it holds 0.

Signed-off-by: Peter Rajnoha 
Signed-off-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