Claude review: Fix missing fops.owner in Rust DRM/misc abstractions

[Claude Code Review Bot <claude-review@example.com>]

Overall Series Review

Subject: Fix missing fops.owner in Rust DRM/misc abstractions
Author: Alvin Sun <alvin.sun@linux.dev>
Patches: 8
Reviewed: 2026-05-25T20:45:42.806892

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This is a well-motivated fix for a real use-after-free bug in Rust DRM/miscdevice drivers. When `fops.owner` is NULL, the kernel cannot take a module reference when a file descriptor is opened, allowing `rmmod` to proceed while userspace still holds an open fd — leading to the NULL pointer dereference shown in the cover letter's backtrace.

The design is clean: move `THIS_MODULE` into the existing `ModuleMetadata` trait, have the `#[vtable]` macro auto-inject a `ThisModule` associated type (trait side) and auto-set it to `crate::LocalModule` (impl side), then thread that through to `fops.owner` in DRM and miscdevice. Patches 6-7 are straightforward usage-site updates for configfs and rnull.

The series is logically ordered: infrastructure first (patches 1-3), then the actual bug fixes (patches 4-5), then mechanical updates (patches 6-7). The approach of encoding the module identity as a type-level associated type is a reasonable Rust-idiomatic choice that avoids runtime parameters.

**Overall assessment: Good series that fixes a real security/stability bug. A few minor observations below, but nothing blocking.**

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