Claude review: Add reclaim to the dmem cgroup controller

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

Overall Series Review

Subject: Add reclaim to the dmem cgroup controller
Author: =?UTF-8?q?Thomas=20Hellstr=C3=B6m?= <thomas.hellstrom@linux.intel.com>
Patches: 6
Reviewed: 2026-05-16T14:03:59.614912

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This is a well-structured v4 series that adds reclaim support to the dmem cgroup controller, enabling `dmem.max` writes below current usage to trigger TTM eviction rather than silently failing. The layering is clean: patch 1 is a standalone bug fix, patch 2 adds the core cgroup infrastructure, patch 3 provides the TTM eviction machinery, and patches 4-5 wire up xe and amdgpu respectively.

The locking design (rwsem protecting reclaim callbacks against concurrent unregister) is sound, signal handling is proper, and the O_NONBLOCK support is a nice touch. The multi-pass eviction strategy in `ttm_bo_evict_cgroup()` correctly mirrors the existing `ttm_bo_evict_alloc()` approach. The series is generally in good shape for v4.

One design consideration worth flagging: partial reclaim progress currently terminates the retry loop rather than retrying with a smaller target, which is conservative but may leave reclaimable memory on the table. This is discussed further in patch 2/3 below.

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