From mboxrd@z Thu Jan  1 00:00:00 1970
From: Claude Code Review Bot <claude-review@example.com>
To: dri-devel-reviews@example.com
Subject: Claude review: drm/ttm: Use common ancestor of evictor and evictee as limit pool
Date: Tue, 03 Mar 2026 13:29:39 +1000
Message-ID: <review-patch6-20260302-dmemcg-aggressive-protect-v5-6-ffd3a2602309@gmx.de>
In-Reply-To: <20260302-dmemcg-aggressive-protect-v5-6-ffd3a2602309@gmx.de>
References: <20260302-dmemcg-aggressive-protect-v5-0-ffd3a2602309@gmx.de> <20260302-dmemcg-aggressive-protect-v5-6-ffd3a2602309@gmx.de>
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Patch Review

**Purpose:** Uses the common ancestor of evictor and evictee as the root fo=
r protection calculation, enabling correct behavior for sibling cgroup prio=
ritization.

**Self-eviction guard:**
```c
	if (evict_walk->alloc_state->only_evict_unprotected &&
			bo->resource->css =3D=3D evict_walk->alloc_state->charge_pool)
		return 0;
```
This prevents a protected cgroup from evicting its own buffers during the "=
only unprotected" pass. The pointer comparison checks for exact same pool =
=E2=80=94 not parent/child relationships. This is intentional: a cgroup sho=
uld be allowed to evict from its own children, but not from itself when it'=
s trying to enforce protection.

**Common ancestor logic:** Well-motivated by the comment:
```c
	/*
	 * ...Recursive protection distributes cgroup protection afforded
	 * to a parent cgroup but not used explicitly by a child cgroup between
	 * all child cgroups...
	 */
```
Without this, two sibling cgroups where one is protected and the other isn'=
t would both appear equally protected (due to recursive distribution from t=
heir common parent), preventing the protected one from stealing from the un=
protected one.

**Reference management:**
```c
	ancestor =3D dmem_cgroup_common_ancestor(bo->resource->css,
					       evict_walk->alloc_state->charge_pool);
	limit_pool =3D ancestor;
	...
	evict_valuable =3D dmem_cgroup_state_evict_valuable(limit_pool, ...);
	if (ancestor)
		dmem_cgroup_pool_state_put(ancestor);
```
The `put` after use is correct, but relies on `dmem_cgroup_common_ancestor(=
)` returning a referenced pool (see concern in patch 2 review).

**Formatting nit:** The self-eviction check uses non-standard indentation:
```c
	if (evict_walk->alloc_state->only_evict_unprotected &&
			bo->resource->css =3D=3D evict_walk->alloc_state->charge_pool)
```
Kernel style typically aligns continuation lines to the opening parenthesis=
, or uses a single tab indent. The double-tab here is inconsistent with the=
 rest of the series.

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