Claude review: gpu/buddy: Track per-order free blocks with a scoreboard

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

Patch Review

**Verdict: Looks good overall.**

The free_scoreboard is maintained at all the right transition points:

1. `mark_free()` — increment (block enters free state)
2. `mark_allocated()` — decrement (block leaves free state)
3. `mark_split()` — decrement (block leaves free state to become split)
4. `__gpu_buddy_free()` coalescing loop — decrement for `buddy` being removed from rbtree before `gpu_block_free()`
5. `__force_merge()` — decrement for `block` being removed from rbtree before merging

All five sites are correct and pair up properly.

**Init/fini:** The allocation and error-handling are correct. `free_scoreboard` is allocated with `kcalloc` (zero-initialized), freed in `gpu_buddy_fini()`, and the error path in `gpu_buddy_init()` has a proper `out_free_scoreboard` label.

**Minor nit — label naming foreshadowing:** The error label is named `out_free_scoreboard`, which works for this patch. However, patch 2 renames it to `out_free_free_scoreboard` to disambiguate from `out_free_scoreboard` (which becomes the used_scoreboard label). This creates a somewhat awkward label name. Consider using something like `out_free_sb` / `out_used_sb` instead, or `out_scoreboard` / `out_used_scoreboard`. But this is cosmetic.

**No issues found.**

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Generated by Claude Code Patch Reviewer