Quoting Oren Laadan (orenl@xxxxxxxxxxx):
> > + file = alloc_file(nd.path.mnt, ptmxdentry, FMODE_READ|FMODE_WRITE, &tty_fops);
> > + path_put(&nd.path);
> > + if (!file) {
> > + dput(ptmxdentry);
> > + return ERR_PTR(-EINVAL);
> > + }
> > +
> > + ret = security_dentry_open(file, current_cred());
> > + if (ret) {
> > + fput(file);
> > + return ERR_PTR(ret);
> > + }
> > + /* check write access perms to file */
>
> I bet the above can be done by reusing lookup and __dentry_open()
> functions from fs/open.c and fs/namei.c ...
With lookup_create()? Hmm, yeah - I think there are reasons I can't do
that, but I'll just try and see where it gets us.
> > +
> > + lock_kernel(); /* tty_open does it... */
> > + ret = open_create_pty(fdir, h->index, file);
> > + unlock_kernel();
> > + if (ret) {
> > + fput(file);
> > + return ERR_PTR(ret);
> > + }
> > + ckpt_debug("master file %p (obj %d)\n", file, h->file_objref);
> > +
> > + /*
> > + * Add file to objhash to ensure proper cleanup later
> > + * (it isn't referenced elsewhere). Use h->file_objref
> > + * which was explicitly during checkpoint for this.
> > + */
> > + ret = ckpt_obj_insert(ctx, file, h->file_objref, CKPT_OBJ_FILE);
> > + if (ret < 0) {
> > + fput(file);
> > + return ERR_PTR(ret);
> > + }
>
> Can do this in caller. So
>
> > +
> > + tty = file->private_data;
> > + fput(file); /* objhash took a ref */
> > +
> > + return tty;
> > +}
> > +
> > +struct tty_struct *pty_open_by_master(struct ckpt_ctx *ctx,
> > + struct ckpt_hdr_tty *h)
> > +{
> > + struct file *fdir;
> > + struct tty_struct *tty;
> > + /*
> > + * we need to pick a way to specify which devpts
> > + * mountpoint to use. For now, we'll just use
> > + * whatever /dev/ptmx points to
> > + */
> > + fdir = filp_open("/dev/pts", O_RDONLY, 0);
> > + if (IS_ERR(fdir))
> > + return ERR_PTR(PTR_ERR(fdir));
>
> Does this mean that to restore a subtree on a system without
> devpts-ns it won't work ? (no /dev/pts/ptmx)
Yes. I figured once we settle on devpts ns handling, we can
trivially special-case the DEVPTS_MULTIPLE_INSTANCES=n case
to use /dev/ptmx.
Since we're punting on devpts namespaces anyway I guess the
pty_open_by_master() can just open /dev/ptmx directly for
now.
Or, maybe we're better off handling the namespaces. Because
without doing that, we are hard-coding pathnames in the kernel
left and right, and that's Bad(tm).
thanks,
-serge
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