Re: Why does d_splice_alias need to check IS_ROOT?
From: Lei Chen
Date: Sun May 27 2018 - 07:09:45 EST
Al Viro <viro@xxxxxxxxxxxxxxxxxx> ä2018å5æ27æåæ äå1:12åéï
> 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.