Al Viro <viro@xxxxxxxxxxxxxxxxxx> 于2018年5月27日周日 上午1:12写道： > On Sun, May 27, 2018 at 12:33:40AM +0800, Lei Chen wrote: > > Hello list, > > > > I'm insteresting in how hard link and denry lookup work and their > > implementation. > > > > I know that this interface tries to connect an inode to a dentry, but > > why does it need > > to check whether the inode alias IS_ROOT if the inode represents a directory? > > And the code process in different way according to check result. What > > occasions > > are they used for? > If it's disconnected (and not an ancestor of the place where we want it), > we can just move it in place, no questions asked. If it is *NOT* > disconnected, the only thing we can do is to detach it from where it > is and move it over. Which takes a lot more care wrt locking. Thanks for your reply. But why does it mean "disconnected" if IS_ROOT returns true?? Why not use hlist_unhashed(&entry->d_u.d_alias) or d_is_negative to determine whether a dentry is connected to an inode?? I found that when we allocate a new dentry struct, its parent is not always itself.
