Claude review: drm/ttm/pool: back up at native page order

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

Overall Series Review

Subject: drm/ttm/pool: back up at native page order
Author: Matthew Brost <matthew.brost@intel.com>
Patches: 5
Reviewed: 2026-05-05T08:38:59.897610

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This is a single patch that modifies TTM pool backup to preserve compound page integrity during the shrinker backup path, avoiding memory fragmentation caused by unconditionally splitting higher-order allocations to order-0 before writing to shmem. The motivation is sound and well-documented: under kswapd pressure, the existing `split_page()` approach shatters higher-order blocks, amplifying fragmentation and preventing the system from recovering.

The core approach — back up each sub-page to shmem but free the allocation atomically at native order — is clean. The rollback logic for partial failures is correct and ensures compound-level atomicity. However, there is one significant issue: the patch uses `__free_pages_gpu_account()`, which does not exist in the current drm-next tree. This is an unstated build dependency on another pending series (likely [1] referenced in the cover notes). The patch cannot compile standalone against drm-next.

The commit message is thorough, and the `Cc: stable` tag is present, but the stable backport would also need the dependency or an adaptation.

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