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: Be more aggressive when allocating below protection limit
Date: Tue, 03 Mar 2026 13:29:39 +1000
Message-ID: <review-patch5-20260302-dmemcg-aggressive-protect-v5-5-ffd3a2602309@gmx.de>
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Patch Review

**Purpose:** The core behavioral change. When an allocation is covered by c=
group protection (below min/low), attempt eviction of unprotected buffers i=
nstead of backing off to GTT.

**Logic analysis:**
```c
	may_evict |=3D dmem_cgroup_below_min(NULL, alloc_state->charge_pool);
	below_low =3D dmem_cgroup_below_low(NULL, alloc_state->charge_pool);
	alloc_state->only_evict_unprotected =3D !may_evict && below_low;
```

This creates three tiers:
1. **Below min** (strongest): `may_evict` is forced true =E2=86=92 full evi=
ction including low-protected BOs
2. **Below low but not min**: `only_evict_unprotected =3D true` =E2=86=92 e=
vict only unprotected BOs
3. **Not protected**: No change from current behavior

The `only_evict_unprotected` flag prevents the retry-with-low path:
```c
	if (!lret && evict_walk.hit_low && !state->only_evict_unprotected) {
```
This is correct =E2=80=94 when we're in "protected allocator" mode, we shou=
ld not escalate to evicting low-protected BOs because those are peers that =
deserve their protection.

The extended comment block explaining the protection model is excellent and=
 makes the reasoning very clear.

The condition `(may_evict || below_low)` for converting `-ENOSPC` to `-EBUS=
Y`:
```c
		if (ret =3D=3D -ENOSPC && (may_evict || below_low))
			ret =3D -EBUSY;
```
ensures eviction is attempted for any protected allocation.

Note: `dmem_cgroup_below_min/low(NULL, ...)` uses global root for protectio=
n calculation. This is correct for determining if the *allocator* is protec=
ted. Patch 6 then handles the per-evictee calculation correctly using commo=
n ancestors.

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