> > +/*
> > + * Return true if 'path' is reachable from 'root' + */
> > +static bool is_path_reachable(const struct path *path, const struct
> > path *root) +{
> > + struct dentry *dentry = path->dentry; + struct vfsmount *mnt =
> > path->mnt;
> > + bool res = false;
> > +
> > + spin_lock(&dcache_lock);
> > + for (;;) {
> > + if (dentry == root->dentry && mnt == root->mnt)
> { + res = true;
> > + break;
> > + }
> > + if (dentry == mnt->mnt_root || IS_ROOT(dentry))
> { + /* Global root?
> > */
> > + spin_lock(&vfsmount_lock);
> > + if (mnt->mnt_parent == mnt) {
> > + spin_unlock(&vfsmount_lock);
> > + break;
> > + }
> > + dentry = mnt->mnt_mountpoint;
> > + mnt = mnt->mnt_parent;
> > + spin_unlock(&vfsmount_lock);
> > + continue;
> > + }
> > + dentry = dentry->d_parent;
> > + }
> > + spin_unlock(&dcache_lock);
> > +
> > + return res;
> > +}
> > +
>
> Hmm, this may hold dcache_lock for some time. Isn't it enough to use
> rcu_readlock() and read_seqbegin(&rename_lock) ?
Maybe. I just blindly copied the d_path() code without thinking much.
Is this worth optimizing? I mean, getting RCU wrong is easy, and it
makes my head hurt to think about it. And dcache_lock shouldn't be
used in any performance critical code paths anyway.
Thanks,
Miklos
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