Re: [PATCH v3 18/30] liveupdate: luo_files: luo_ioctl: Add ioctls for per-file state management

[Pasha Tatashin]

On Thu, Aug 14, 2025 at 10:02 AM Jason Gunthorpe <jgg@xxxxxxxxxx> wrote:
>
> On Thu, Aug 07, 2025 at 01:44:24AM +0000, Pasha Tatashin wrote:
> > +struct liveupdate_ioctl_get_fd_state {
> > +     __u32           size;
> > +     __u8            incoming;
> > +     __aligned_u64   token;
> > +     __u32           state;
> > +};
>
> Same remark about explicit padding and checking padding for 0

Done

> > + * luo_file_get_state - Get the preservation state of a specific file.
> > + * @token: The token of the file to query.
> > + * @statep: Output pointer to store the file's current live update state.
> > + * @incoming: If true, query the state of a restored file from the incoming
> > + *            (previous kernel's) set. If false, query a file being prepared
> > + *            for preservation in the current set.
> > + *
> > + * Finds the file associated with the given @token in either the incoming
> > + * or outgoing tracking arrays and returns its current LUO state
> > + * (NORMAL, PREPARED, FROZEN, UPDATED).
> > + *
> > + * Return: 0 on success, -ENOENT if the token is not found.
> > + */
> > +int luo_file_get_state(u64 token, enum liveupdate_state *statep, bool incoming)
> > +{
> > +     struct luo_file *luo_file;
> > +     struct xarray *target_xa;
> > +     int ret = 0;
> > +
> > +     luo_state_read_enter();
>
> Less globals, at this point everything should be within memory
> attached to the file descriptor and not in globals. Doing this will
> promote good maintainable structure and not a spaghetti
>
> Also I think a BKL design is not a good idea for new code. We've had
> so many bad experiences with this pattern promoting uncontrolled
> incomprehensible locking.
>
> The xarray already has a lock, why not have reasonable locking inside
> the luo_file? Probably just a refcount?
>
> > +     target_xa = incoming ? &luo_files_xa_in : &luo_files_xa_out;
> > +     luo_file = xa_load(target_xa, token);
> > +
> > +     if (!luo_file) {
> > +             ret = -ENOENT;
> > +             goto out_unlock;
> > +     }
> > +
> > +     scoped_guard(mutex, &luo_file->mutex)
> > +             *statep = luo_file->state;
> > +
> > +out_unlock:
> > +     luo_state_read_exit();
>
> If we are using cleanup.h then use it for this too..
>
> But it seems kind of weird, why not just
>
> xa_lock()
> xa_load()
> *statep = READ_ONCE(luo_file->state);
> xa_unlock()
>
> ?

Yes, we can simplify with xa_lock(), thank you for your suggestion.

>
> > +static int luo_ioctl_set_fd_event(struct luo_ucmd *ucmd)
> > +{
> > +     struct liveupdate_ioctl_set_fd_event *argp = ucmd->cmd;
> > +     int ret;
> > +
> > +     switch (argp->event) {
> > +     case LIVEUPDATE_PREPARE:
> > +             ret = luo_file_prepare(argp->token);
> > +             break;
> > +     case LIVEUPDATE_FREEZE:
> > +             ret = luo_file_freeze(argp->token);
> > +             break;
> > +     case LIVEUPDATE_FINISH:
> > +             ret = luo_file_finish(argp->token);
> > +             break;
> > +     case LIVEUPDATE_CANCEL:
> > +             ret = luo_file_cancel(argp->token);
> > +             break;
>
> The token should be converted to a file here instead of duplicated in
> each function

struct luo_file is preivate to luo_file.c, and I think it makes sense
to keep it that way, amount of duplicated code is trivial.00

> >  static int luo_open(struct inode *inodep, struct file *filep)
> >  {
> >       if (atomic_cmpxchg(&luo_device_in_use, 0, 1))
> > @@ -149,6 +191,8 @@ union ucmd_buffer {
> >       struct liveupdate_ioctl_fd_restore      restore;
> >       struct liveupdate_ioctl_get_state       state;
> >       struct liveupdate_ioctl_set_event       event;
> > +     struct liveupdate_ioctl_get_fd_state    fd_state;
> > +     struct liveupdate_ioctl_set_fd_event    fd_event;
> >  };
> >
> >  struct luo_ioctl_op {
> > @@ -179,6 +223,10 @@ static const struct luo_ioctl_op luo_ioctl_ops[] = {
> >                struct liveupdate_ioctl_get_state, state),
> >       IOCTL_OP(LIVEUPDATE_IOCTL_SET_EVENT, luo_ioctl_set_event,
> >                struct liveupdate_ioctl_set_event, event),
> > +     IOCTL_OP(LIVEUPDATE_IOCTL_GET_FD_STATE, luo_ioctl_get_fd_state,
> > +              struct liveupdate_ioctl_get_fd_state, token),
> > +     IOCTL_OP(LIVEUPDATE_IOCTL_SET_FD_EVENT, luo_ioctl_set_fd_event,
> > +              struct liveupdate_ioctl_set_fd_event, token),
> >  };
>
> Keep sorted

Done