Provided by: linux-doc-2.6.15_2.6.15-23.39_all bug

NAME

       d_lookup - search for a dentry

SYNOPSIS

       struct dentry * d_lookup  (struct dentry * parent, struct qstr * name);

ARGUMENTS

       parent parent dentry

       name   qstr of name we wish to find

DESCRIPTION

       Searches the children of the parent dentry for the name in question. If
       the  dentry  is found its reference count is incremented and the dentry
       is returned. The caller must use d_put to free the entry  when  it  has
       finished using it. NULL is returned on failure.

       __d_lookup  is  dcache_lock free. The hash list is protected using RCU.
       Memory barriers are used while updating and doing  lockless  traversal.
       To avoid races with d_move while rename is happening, d_lock is used.

       Overflows  in  memcmp,  while d_move, are avoided by keeping the length
       and name pointer in one structure pointed by d_qstr.

        rcu_read_lock and rcu_read_unlock are used to disable preemption while
       lookup is going on.

       dentry_unused  list  is  not  updated even if lookup finds the required
       dentry in  there.  It  is  updated  in  places  such  as  prune_dcache,
       shrink_dcache_sb,  select_parent and __dget_locked. This laziness saves
       lookup from dcache_lock acquisition.

        d_lookup is protected against the concurrent renames in some unrelated
       directory using the seqlockt_t rename_lock.