On Tue, Nov 24, 2015 at 12:16:10PM -0500, Tejun Heo wrote:
> Hello,
>
> On Mon, Nov 16, 2015 at 01:51:44PM -0600, serge@xxxxxxxxxx wrote:
> > +struct dentry *kernfs_obtain_root(struct super_block *sb,
> > + struct kernfs_node *kn)
> > +{
> > + struct dentry *dentry;
> > + struct inode *inode;
> > +
> > + BUG_ON(sb->s_op != &kernfs_sops);
> > +
> > + /* inode for the given kernfs_node should already exist. */
> > + inode = ilookup(sb, kn->ino);
> > + if (!inode) {
> > + pr_debug("kernfs: could not get inode for '");
> > + pr_cont_kernfs_path(kn);
> > + pr_cont("'.\n");
> > + return ERR_PTR(-EINVAL);
> > + }
>
> Hmmm... but inode might not have been instantiated yet. Why not use
> kernfs_get_inode()?
>
> > + /* instantiate and link root dentry */
> > + dentry = d_obtain_root(inode);
> > + if (!dentry) {
> > + pr_debug("kernfs: could not get dentry for '");
> > + pr_cont_kernfs_path(kn);
> > + pr_cont("'.\n");
> > + return ERR_PTR(-ENOMEM);
> > + }
> > +
> > + /* If this is a new dentry, set it up. We need kernfs_mutex because this
> > + * may be called by callers other than kernfs_fill_super. */
>
> Formatting.
>
> > + mutex_lock(&kernfs_mutex);
> > + if (!dentry->d_fsdata) {
> > + kernfs_get(kn);
> > + dentry->d_fsdata = kn;
> > + } else {
> > + WARN_ON(dentry->d_fsdata != kn);
> > + }
> > + mutex_unlock(&kernfs_mutex);
> > +
> > + return dentry;
> > +}
>
> Wouldn't it be simpler to walk dentry from kernfs root than
> duplicating dentry instantiation?
Sorry I don't think I'm following. Are you suggesting walking the
kn->parent chain backward and doing d_lookup() at each point starting
with sb->s_root?
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