• Mikulas Patocka's avatar
    dm: wait until embedded kobject is released before destroying a device · be35f486
    Mikulas Patocka authored
    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/2014/1/4/83Signed-off-by: default avatarMikulas Patocka <mpatocka@redhat.com>
    Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
    Cc: stable@vger.kernel.org
    be35f486
dm-sysfs.c 2.38 KB