On Thu, Oct 16, 2025 at 05:42:02AM +0000, Tzung-Bi Shih wrote:
> Introduce fs_revocable_replace() to simplify the use of the revocable
> API with file_operations.
>
> The function, should be called from a driver's ->open(), replaces the
> fops with a wrapper that automatically handles the `try_access` and
> `withdraw_access`.
>
> When the file is closed, the wrapper's ->release() restores the original
> fops and cleanups. This centralizes the revocable logic, making drivers
> cleaner and easier to maintain.
>
> Signed-off-by: Tzung-Bi Shih <[email protected]>
> ---
> PoC patch.
>
> Known issues:
> - All file operations call revocable_try_access() for guaranteeing the
> resource even if the resource may be unused in the fops.
Why is this so complicated??
You already added a per-flip struct:
> +struct fs_revocable_replacement {
> + const struct fs_revocable_operations *frops;
> + const struct file_operations *orig_fops;
> + struct file_operations fops;
> + struct revocable **revs;
> + size_t num_revs;
> +};
Why does it need so much junk in it?
struct fs_revocable_replacement {
struct srcu_struct srcu;
bool *alive;
};
That's it. When the caller sets this up it provides a bool * pointer
from it's own private struct that is kept krefcounted to life cycle of
the struct file.
Then the ops wrapers are a simple thing - generate them with a macro:
srcu_read_lock(&f_rr->srcu);
if (*f_rr_>alive)
ret = f_rr->orig_fops->XX(...)
else
ret = -ENODEV;
srcu_read_unlock(&f_rr->srcu);
return ret;
No need for all this revokable maze to do somethinig so simple.
Also, I don't think srcu is a good idea for this use case, maybe as an
option, but the default should be to use rwsem.
Jason
