From: Maneesh Soni <maneesh@in.ibm.com>

o This patch introduces the new sysfs_dirent data structure. The sysfs_dirent
  is added to the dentry corresponding to each of the element which can be
  represented in sysfs like, kobject (directory), text or binary attributes
  (files), attribute groups (directory) and symlinks.

o It uses dentry's d_fsdata field to attach the corresponding sysfs_dirent.

o The sysfs_dirents are maintained in a tree of all the sysfs entries using the
  s_children and s_sibling list pointers.

o This patch also changes how we access attributes and kobjects in
  file_operations from a given dentry, basically introducing one more level of
  indirection.

o The sysfs_dirents are freed and the sysfs_dirent tree is updated accordingly
  upon the deletion of corresponding dentry. The sysfs dirents are kept alive
  as long as there is corresponding dentry around. The are freed when the
  dentry is finally out of dcache using the ->d_iput() method.

o This also fixes the dentry leaks in case of error paths after sysfs has
  got a newly alocated (and hashed) dentry from sysfs_get_dentry() by
  d_drop()'ing the dentry.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>