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: cgroup/dmem: return error when failing to set dmem.max
Date: Sun, 22 Mar 2026 05:01:52 +1000
Message-ID: <review-patch1-20260318-dmem_max_ebusy-v1-1-b7e461157b29@igalia.com>
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Patch Review

**Correctness of the core fix:** The key change at line 121 of the diff is =
correct:

```c
-	page_counter_set_max(&pool->cnt, val);
+	return page_counter_set_max(&pool->cnt, val);
```

`page_counter_set_max()` returns `int` (confirmed at `include/linux/page_co=
unter.h:86`), and can return `-EBUSY`. Propagating this is the right thing =
to do.

**Signature change is appropriate:** Changing the `apply` callback from `vo=
id (*apply)(...)` to `int (*apply)(...)` and updating `set_resource_min`/`s=
et_resource_low` to return `0` is a clean way to handle this uniformly.

**Potential issue =E2=80=94 partial application on multi-region writes:** L=
ooking at the loop in `dmemcg_limit_write()` (line 734 of the existing code=
: `while (buf && !err)`), when a user writes multiple region limits in a si=
ngle write (multiple lines), an error from `apply()` on one region will sto=
p processing subsequent regions. The commit message acknowledges this ("Ret=
urn as soon as setting one of the regions max limit fails"). However, consi=
der that **regions processed before the failing one have already been commi=
tted** =E2=80=94 the function does not roll back previously applied limits.=
 This is a pre-existing pattern (same happens for parse errors), but worth =
noting that the semantics are "apply until first failure" with no rollback.

**Minor note =E2=80=94 `err` after `apply` vs `goto out_put`:** Looking at =
the patched code:

```c
		err =3D apply(pool, new_limit);
		dmemcg_pool_put(pool);

out_put:
		kref_put(&region->ref, dmemcg_free_region);
```

When `apply()` returns an error, the code still correctly calls `dmemcg_poo=
l_put(pool)` and `kref_put()` before the `while` loop condition `!err` term=
inates the loop. This is correct =E2=80=94 no resource leak.

**Nit =E2=80=94 `set_resource_min` and `set_resource_low`:** `page_counter_=
set_min()` and `page_counter_set_low()` are `void` functions, so wrapping t=
hem with `return 0` is fine. If these ever gain error returns in the future=
, this patch has already set up the plumbing to handle it. No issue here.

**Verdict:** The patch looks correct and ready to apply. The fix is minimal=
 and appropriate.=20

Reviewed-by quality: **Good to go**, no blocking issues.

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