Claude review: ttm/pool: Use sentinels in debugfs

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

Patch Review

**Correctness: Good.** The sentinel checks match exactly what the underlying functions can return:

- `ttm_pool_shrinker_count()` at line 1222 returns `SHRINK_EMPTY` when `num_pages` is 0 — the patch correctly checks `count == SHRINK_EMPTY`.
- `ttm_pool_shrinker_scan()` at line 1213 returns `SHRINK_STOP` when `num_freed` is 0 — the patch correctly checks `scanned == SHRINK_STOP`.

**Minor observations:**

1. **Scan is unconditional even when count shows empty.** The code calls `ttm_pool_shrinker_scan()` even when `count == SHRINK_EMPTY` (i.e., there are zero pages on this node). The scan will iterate and find nothing to free, returning `SHRINK_STOP`. This is harmless since this is a debugfs path (not performance-critical), and the pre-existing code had the same behavior. Not a blocking concern, but a `if (count != SHRINK_EMPTY)` guard could avoid the pointless scan call.

2. **The comment is reasonable.** The inline comment `/* Convert shrinker API sentinel values to 0 for debugfs output */` explains the *why* clearly enough.

3. **The variable split is good practice.** Separating `scanned = ttm_pool_shrinker_scan(...)` out of the `seq_printf` call improves readability and enables the sentinel checks without evaluating side effects in a printf argument list.

**No correctness issues found.** The patch is a clean, minimal fix for a real debugfs output bug.

Reviewed-by: looks appropriate.

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Generated by Claude Code Patch Reviewer