• Tejun Heo's avatar
    kernfs: remove KERNFS_REMOVED · ae34372e
    Tejun Heo authored
    KERNFS_REMOVED is used to mark half-initialized and dying nodes so
    that they don't show up in lookups and deny adding new nodes under or
    renaming it; however, its role overlaps those of deactivation and
    removal from rbtree.
    
    It's necessary to deny addition of new children while removal is in
    progress; however, this role considerably intersects with deactivation
    - KERNFS_REMOVED prevents new children while deactivation prevents new
    file operations.  There's no reason to have them separate making
    things more complex than necessary.
    
    KERNFS_REMOVED is also used to decide whether a node is still visible
    to vfs layer, which is rather redundant as equivalent determination
    can be made by testing whether the node is on its parent's children
    rbtree or not.
    
    This patch removes KERNFS_REMOVED.
    
    * Instead of KERNFS_REMOVED, each node now starts its life
      deactivated.  This means that we now use both atomic_add() and
      atomic_sub() on KN_DEACTIVATED_BIAS, which is INT_MIN.  The compiler
      generates an overflow warnings when negating INT_MIN as the negation
      can't be represented as a positive number.  Nothing is actually
      broken but let's bump BIAS by one to avoid the warnings for archs
      which negates the subtrahend..
    
    * KERNFS_REMOVED tests in add and rename paths are replaced with
      kernfs_get/put_active() of the target nodes.  Due to the way the add
      path is structured now, active ref handling is done in the callers
      of kernfs_add_one().  This will be consolidated up later.
    
    * kernfs_remove_one() is updated to deactivate instead of setting
      KERNFS_REMOVED.  This removes deactivation from kernfs_deactivate(),
      which is now renamed to kernfs_drain().
    
    * kernfs_dop_revalidate() now tests RB_EMPTY_NODE(&kn->rb) instead of
      KERNFS_REMOVED and KERNFS_REMOVED test in kernfs_dir_pos() is
      dropped.  A node which is removed from the children rbtree is not
      included in the iteration in the first place.  This means that a
      node may be visible through vfs a bit longer - it's now also visible
      after deactivation until the actual removal.  This slightly enlarged
      window difference doesn't make any difference to the userland.
    
    * Sanity check on KERNFS_REMOVED in kernfs_put() is replaced with
      checks on the active ref.
    
    * Some comment style updates in the affected area.
    
    v2: Reordered before removal path restructuring.  kernfs_active()
        dropped and kernfs_get/put_active() used instead.  RB_EMPTY_NODE()
        used in the lookup paths.
    Signed-off-by: default avatarTejun Heo <tj@kernel.org>
    Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    ae34372e
kernfs.h 10.4 KB