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/nouveau: Wire up dmem cgroups
Date: Sun, 12 Apr 2026 10:21:18 +1000
Message-ID: <review-patch1-20260410081322.5577-1-natalie.vock@gmx.de>
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Patch Review

**Concept: Correct.** The registration is placed in the right location with=
in `nouveau_ttm_init_vram()`, on the Tesla+ path where `man` is dynamically=
 allocated. The header for `drmm_cgroup_register_region` is available trans=
itively via `nouveau_drv.h` -> `drm/drm_drv.h`. The region name `"vram"` an=
d size `drm->gem.vram_available` are appropriate and consistent with what a=
mdgpu/xe do.

**Bug: Memory leak of `man` on cgroup registration failure.**

Looking at the patched code (lines 183=E2=80=93194):

```c
if (drm->client.device.info.family >=3D NV_DEVICE_INFO_V0_TESLA) {
    struct ttm_resource_manager *man =3D kzalloc_obj(*man);

    if (!man)
        return -ENOMEM;

    man->func =3D &nouveau_vram_manager;

    man->cg =3D drmm_cgroup_register_region(drm->dev, "vram",
                          drm->gem.vram_available);
    if (IS_ERR(man->cg))
        return PTR_ERR(man->cg);
```

If `drmm_cgroup_register_region()` fails, the function returns immediately =
via `return PTR_ERR(man->cg)` without freeing `man`, which was allocated wi=
th `kzalloc_obj()` at line 184. This is a memory leak.

By contrast, in the amdgpu driver (`amdgpu_vram_mgr.c:917-923`), `man` is e=
mbedded within `struct amdgpu_vram_mgr` (not separately heap-allocated), so=
 there's no analogous leak. The nouveau code allocates `man` on the heap an=
d must free it on all error paths.

**Fix:** Add `kfree(man)` before the error return:

```c
    if (IS_ERR(man->cg)) {
        kfree(man);
        return PTR_ERR(man->cg);
    }
```

Note: there is a subtlety =E2=80=94 `man->cg` is read after `kfree(man)` in=
 `PTR_ERR(man->cg)`. To be safe, this should use a local variable:

```c
    if (IS_ERR(man->cg)) {
        int ret =3D PTR_ERR(man->cg);
        kfree(man);
        return ret;
    }
```

**Pre-Tesla path:** The `else` branch (line 201=E2=80=93203) uses `ttm_rang=
e_man_init()` which handles its own allocation internally. There is no cgro=
up registration for this path, which seems intentional and reasonable (pre-=
Tesla hardware is quite old).

**No-op when cgroups disabled:** `drmm_cgroup_register_region()` should ret=
urn a non-error value when `CONFIG_CGROUP_DMEM` is not enabled (a stub), so=
 this won't break builds without cgroup support. This is fine.

**Summary:** The patch is the right approach but needs the `kfree(man)` lea=
k fix on the error path. With that addressed, this is a clean, minimal addi=
tion. Worth also considering whether a `Cc: stable` tag is warranted (proba=
bly not =E2=80=94 this is new functionality, not a fix).

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