From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ej1-f48.google.com (mail-ej1-f48.google.com [209.85.218.48]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8D45726FA6F for ; Mon, 1 Sep 2025 14:51:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.218.48 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756738266; cv=none; b=NBWYcNDtZmMorPfyklg5E7wX7uqSJXLiAfHEWc5E5eUwJvDscLkcIyN0FaBLZrBZlSXD9RhKQFj4bX3jBZOLJ0Q93KCKU3vb6p3kJ5vyu/3V81ehuq2f1i8pJxNh9CT5HuZsmz0CihPuBma4xqowIwifSO1sITfsc3PAvUcKr2c= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756738266; c=relaxed/simple; bh=JMFdiHPLwPv1+gLtBINWH78t6YBFk5g7hlH1uky4h3g=; h=MIME-Version:References:In-Reply-To:From:Date:Message-ID:Subject: To:Cc:Content-Type; b=JbGn8lxlR6WBpevHw1EVpy59f8S9h+WOV+pIbAu1fxewSbDF7N5toerZR7DXj8ym2khsf4lBvBh6sIEBVXQjtqwXpB4UOeZzhE9DDa2YgOVyq/H4xvtR3AklgSeipy6gytIddTPYt74RR3SVhZmNMTYdIMLdJJHp30MFvyAU0qU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=ionos.com; spf=pass smtp.mailfrom=ionos.com; dkim=pass (2048-bit key) header.d=ionos.com header.i=@ionos.com header.b=N6IgICCA; arc=none smtp.client-ip=209.85.218.48 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=ionos.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=ionos.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=ionos.com header.i=@ionos.com header.b="N6IgICCA" Received: by mail-ej1-f48.google.com with SMTP id a640c23a62f3a-afefc7be9d4so490788666b.1 for ; Mon, 01 Sep 2025 07:51:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ionos.com; s=google; t=1756738263; x=1757343063; darn=vger.kernel.org; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:from:to:cc:subject:date :message-id:reply-to; bh=Ou2wtlN8PDWTGj+LZ1aCRhABiZ7uTVFHZhzB51NR+RA=; b=N6IgICCAmvICqyz1QZVXwn9zdAPkQ3RxYExpHMX7aHn04rvBwoMvru7QwcAsqxf6tH h+egZ8BcufnW55evIN76YXIirKK1LGiLx5FPt/6vrAWk82Sc34Zlv51UgU9tGOiTpgsk +3M2IuLcSNH0UkFcyeg/BOTpMAojqqIkQ9LdZQ1FtUGgy4PhD0BdrS5Im87V/nA5eSYo DEjCCEG9GxEaQT/oMCVRufvirj044CI6tA9DlQTQlV0d48wIpI7S0Yaj7V7wo7BOT52d YL/cfpu4Jph4Pcr3Q2W7cbAeJLzna3z5IeX5/5YT1N8fSAM0ShN+4EZa/YtzoxoUY4A5 0rIw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1756738263; x=1757343063; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=Ou2wtlN8PDWTGj+LZ1aCRhABiZ7uTVFHZhzB51NR+RA=; b=sqQqVtmtWa2GkaIlOSYXL9UGVHTmgSwn+61Inc53PFf+WlhEoKVbG3z8GJ7/HHSwYJ /7blIbe53YiSof2U+Osl/D060XJtvAgfAFrXX91tHV5sXnfHR6sDu17HIXFwR1yFKpVo +uibm/OVEi/0eJyqNF9vA7AiYU5P/HKbba/vcvrg+OSBNuDkuvqz3W0LZXnY33FN7nmH c68QuaO3MNE9rmaXm2SlX/TvD49815bpk5b1UEpesn43Ega48bPIKNZctSo1buKTWdfk vGdL0WO4LcT/QrsfGVaeyZK/i90J1p19lBszcj8tzIMh81sU+viXAVxtfhtYG+CQ0IVv wD3A== X-Forwarded-Encrypted: i=1; AJvYcCWmJpMnAKG3q3t1VnwHJfEnVDio0j2r8Wf7+bO8Uqsheh1vWqkWX6r0Wrdd2bKEEwLMRRepnBuJJJzw@vger.kernel.org X-Gm-Message-State: AOJu0YwCOSiLblg8IkfO1YFXe9ZUqhRXmKQLbXawhC9+epEmYH7VlzIW t8okx7UyNanLa4q2N4v/phgLy+x8oGAn1zEHH0NNBJPJu9YDKyAKeXxEloYE5LWj6nESuCbfF02 8sxLfmwOV7FBuOrttvpd+zBK9v1avQcWmneTPH6qpkQ== X-Gm-Gg: ASbGncu+4xzh/pS0r27Jy2ePJ36BkwmCvWDWI/NwB6AahFVOUww9Wtg7OYC3RzU/rN0 aZF4DQzncexFgoHytuNS/Q2ZUK5fr4KP3tE2VFKhbPv04ztHPxwImK5FmCdJmHPfbHHJzfmtcac qtDlokxqh+hOU9mrWyLbkcLH4BYEy99dUW9sR03hY6zhW1gQBIV/LWzC0+hm57vaSs7eIgLiqoF cgijvoSwRBimy3yFmIRoMRG7eDmO49RG2/DeIvg7C+VMw== X-Google-Smtp-Source: AGHT+IFqo0rWyO2Tzcdh9OXq9LZuz+iBrgY4hQc2106202QGZ76zZ9E9VZRcm0Gdr2Fju1hLpDpwI4qcelZS2+NEezM= X-Received: by 2002:a17:907:60d3:b0:afe:8d25:770f with SMTP id a640c23a62f3a-b01d8a26de5mr847287566b.3.1756738262736; Mon, 01 Sep 2025 07:51:02 -0700 (PDT) Precedence: bulk X-Mailing-List: sparclinux@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <20250901123028.3383461-1-max.kellermann@ionos.com> <20250901123028.3383461-3-max.kellermann@ionos.com> <26cb47bb-df98-4bda-a101-3c27298e4452@lucifer.local> In-Reply-To: <26cb47bb-df98-4bda-a101-3c27298e4452@lucifer.local> From: Max Kellermann Date: Mon, 1 Sep 2025 16:50:50 +0200 X-Gm-Features: Ac12FXzHZvMcadklQ3Hi-QaCR2-dPItzNryZ7uqKCm4rMw8McLpdl959UlJ37Wg Message-ID: Subject: Re: [PATCH v5 02/12] mm: constify pagemap related test functions for improved const-correctness To: Lorenzo Stoakes Cc: akpm@linux-foundation.org, david@redhat.com, axelrasmussen@google.com, yuanchu@google.com, willy@infradead.org, hughd@google.com, mhocko@suse.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, vishal.moola@gmail.com, linux@armlinux.org.uk, James.Bottomley@hansenpartnership.com, deller@gmx.de, agordeev@linux.ibm.com, gerald.schaefer@linux.ibm.com, hca@linux.ibm.com, gor@linux.ibm.com, borntraeger@linux.ibm.com, svens@linux.ibm.com, davem@davemloft.net, andreas@gaisler.com, dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com, chris@zankel.net, jcmvbkbc@gmail.com, viro@zeniv.linux.org.uk, brauner@kernel.org, jack@suse.cz, weixugc@google.com, baolin.wang@linux.alibaba.com, rientjes@google.com, shakeel.butt@linux.dev, thuth@redhat.com, broonie@kernel.org, osalvador@suse.de, jfalempe@redhat.com, mpe@ellerman.id.au, nysal@linux.ibm.com, linux-arm-kernel@lists.infradead.org, linux-parisc@vger.kernel.org, linux-s390@vger.kernel.org, sparclinux@vger.kernel.org, linux-fsdevel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Mon, Sep 1, 2025 at 4:25=E2=80=AFPM Lorenzo Stoakes wrote: > 1. (most useful) Const pointer (const *) means that the der= effed > value is const, so * =3D or -> =3D ar= e prohibited. Only this was what my initial patch was about. > 2. (less useful) We can't modify the actual pointer value either, so > e.g. =3D is prohibited. This wasn't my idea, it was Andrew Morton's idea, supported by Yuanchu Xie: https://lore.kernel.org/lkml/CAJj2-QHVC0QW_4X95LLAnM=3D1g6apH=3D=3D-OXZu65= SVeBj0tSUcBg@mail.gmail.com/ You know that because you participated in the discussion. In that thread, nobody objected, so I took the time and adjusted all of my patches. There is some value, but of course it's very small. Note that I added the value-level "const" only to the implementation, never to prototypes, because it would have no effect there.