Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Tue, 18 Oct 2022 10:54:58 -0700
From:   Dan Williams <dan.j.williams@intel.com>
To:     Nathan Chancellor <nathan@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Dan Williams <dan.j.williams@intel.com>
CC:     Nick Desaulniers <ndesaulniers@google.com>,
        Tom Rix <trix@redhat.com>, <linux-mm@kvack.org>,
        <linux-kernel@vger.kernel.org>, <llvm@lists.linux.dev>,
        <patches@lists.linux.dev>, Nathan Chancellor <nathan@kernel.org>
Subject: RE: [PATCH] mm/memremap: Mark folio_span_valid() as __maybe_unused
Message-ID: <634ee87229a37_6be129430@dwillia2-xfh.jf.intel.com.notmuch>
References: <20221018152645.3195108-1-nathan@kernel.org>
Content-Type: text/plain; charset="us-ascii"
Content-Disposition: inline
In-Reply-To: <20221018152645.3195108-1-nathan@kernel.org>
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?0JuR4NIrlJCuPLWHJmcM7y/NogaFBL1A+IFPnk0kBxFQFlYZYYOh3fwrFZdA?=
 =?us-ascii?Q?Y4a42tKkpfrFo0bC/iE8PT8ocpggIQEk/3rS4Zh1NAVIDMvdxpl6UTMDuNkV?=
 =?us-ascii?Q?hc/ViSQwulzwJCLxKtHRflkEWus7mnQlUeZS5PjDcFI3Rjfw3+MavUSPv/Z/?=
 =?us-ascii?Q?bXUCcDRHMbw5FRlknLiWHw7e3Zxv22fHweQsl/KdiPNsxmQrOKEPSUz6tCar?=
 =?us-ascii?Q?x+rGSWrovebqDzvU3Mos+Wh/25XJx1M86VlkwbFt11CuWzEi2hG53CZ+hUZ4?=
 =?us-ascii?Q?NigCPHx1+G5O6wE5t1u6a/doW1V6nNNEo1azjGj9lx7C92qlLKbTqQB+koSg?=
 =?us-ascii?Q?8g9RmpKOEQNJYpe348p/jVn71OrOvOu8ZpPpuV6DzCtpjtOAKJdjDZyb5NVu?=
 =?us-ascii?Q?gM8T8r402TVjDClIKvamdimPAw4zs0TFgrWcpfvRlcObamCrP1JwtmzJhGBv?=
 =?us-ascii?Q?05KgdkKjgjk0gZ8lxuR3a7+pywSocRD/eXzbHtOrqablrhDG8jslpm6YKGir?=
 =?us-ascii?Q?8/PWPLt61epsiLkRmxbUmoN+ZHdsWpv1TkACcFoSg97ICz1PyUT1+VhWg6vk?=
 =?us-ascii?Q?MHmHNs9c2MocAohLNf5lk0tldJWBxYMiWmZjgjy+xnx4cee6DC+Ki1cnqAAX?=
 =?us-ascii?Q?H0fDhSwIngYpCdsMG9jA90HFMbnrhdcc4hqurMnPNoz/q+EYvA92O6YMYaZ4?=
 =?us-ascii?Q?LY1iE/TDrhFF49RZ1sD9VMR7j0EpGyRxGYMvuutsx+nhasgmSdwMYKEn8oS/?=
 =?us-ascii?Q?xENw01Itky8tOuCz4x4XiNWq6zE7mUxMJVNr9FRR3w0G+w2jI9fmUqyPndH7?=
 =?us-ascii?Q?Gr6jK3oGaFuDmc8EATnxK/agU1624tX6vBQIOjQ4D5FGzHDZN58nBvQe2ua+?=
 =?us-ascii?Q?Pm+OB7EezkoNEJu4+2ypsEzJIFJI6M2i2zeSjaLN+1BmXTR5aE3ZxtwpqcE8?=
 =?us-ascii?Q?8Ga9zfchTWrxXYPFwiDgwXyK6cg3RfOOU/dTJ3N3VLuYO+UB5qs484ciQj/v?=
 =?us-ascii?Q?vVjybWJzL+tRI86lRYW/XdxuLwQd2abPLnZ+yVZlpUNy65GLjTXQHVq9+Ig/?=
 =?us-ascii?Q?oT6mPGNxmbqbKrYTcM5+7E3cmbtRPWgFunmItGgAA1Ihp6Yqz2/xlL14OYZx?=
 =?us-ascii?Q?k8lHvtKXrBVcEuL0d26OBR3sOjqtjMSYBfoNHvYrCbK/s3C8ffkdbmxuGNhA?=
 =?us-ascii?Q?BykmZwtVgHaB8WJdpD9C8X5quNcjN7XyrN558kgXrbTYAEKuS8sXUjBy8+XU?=
 =?us-ascii?Q?8wDKUPmMs9jP1mXjPgnhIasEbUqXoUTRsvnnf+OxOWL7CaR4EdVfLR4apgny?=
 =?us-ascii?Q?28lTBUjbkxS3lOlB2rS04tv3KGxPW/7CELtWIY6LSvwMzl51gugEWmm/4kTW?=
 =?us-ascii?Q?WwqJQXs3/WwIpj6pFKI0htM1lX7EaTrAWkx0Ai5frxpy9QpDjrXx+zYFyLta?=
 =?us-ascii?Q?2wVvycUBuNqtxn0AbcO8UOfMWg8OXDIBr6K9MUYhO0qYe6KmDkEKRDZxO1xo?=
 =?us-ascii?Q?7KF77StTo+rjGcKPSqqmgyAaIpgjEQYOWveMwEKBvaUGfnAm2nEGSdaBOFMW?=
 =?us-ascii?Q?3mZeiESif2QFG5zLtOTUXFzCz8BeMmhp1qKTy15aodMqQJz4+RrwwoGHOxXx?=
 =?us-ascii?Q?RA=3D=3D?=
X-MS-Exchange-CrossTenant-Network-Message-Id: 9e795933-45e7-446c-98df-08dab131e0ba
X-MS-Exchange-CrossTenant-AuthSource: MWHPR1101MB2126.namprd11.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 18 Oct 2022 17:55:00.9591
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 46c98d88-e344-4ed4-8496-4ed7712e255d
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: yN+jTToiz2MNEG7WZwPvLMkxjd1/WVbHPX1XHOk/3WhgVLLrMqtz6hSVUzMWNKKZvrP3tnlQKZgxcAoq8pZu/GurYb6osyZ33BUxyorsSd0=
X-MS-Exchange-Transport-CrossTenantHeadersStamped: SJ0PR11MB6695
X-OriginatorOrg: intel.com
X-Spam-Status: No, score=-4.7 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,
        DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_MED,
        SPF_HELO_NONE,SPF_NONE autolearn=ham autolearn_force=no version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on
        lindbergh.monkeyblade.net
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

Nathan Chancellor wrote:
> When building without CONFIG_DEBUG_VM, clang warns:
> 
>   mm/memremap.c:495:13: error: function 'folio_span_valid' is not needed and will not be emitted [-Werror,-Wunneeded-internal-declaration]
>   static bool folio_span_valid(struct dev_pagemap *pgmap, struct folio *folio,
>               ^
>   1 error generated.
> 
> folio_span_valid() is only used within a instance of VM_WARN_ON_ONCE(),
> which evaluates to BUILD_BUG_ON_INVALID() with CONFIG_DEBUG_VM=n, which
> ultimately resolves to sizeof(), which is fully resolved at compile
> time. Basically, the warning is flagging that folio_span_valid() is
> only used in a compile time context and will not be called at run time.
> 
> Since this is expected given the configuration, mark folio_span_valid()
> as __maybe_unused so that there is no warning.
> 
> Fixes: 07108d5bfeeb ("fsdax: introduce pgmap_request_folios()")
> Link: https://github.com/ClangBuiltLinux/linux/issues/1739
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>
> ---
> 
> I am aware the Fixes SHA is probably not stable but I figured I would
> include it anyways.

This fix looks good to me, but I assume commit-ids are not stable until
the patch moves from mm-unstable to mm-stable. Andrew, do I have that
right?