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 tzungbi@kernel.org
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