linux-kernel - Re: [PATCH v6 3/3] mm/gup: disallow FOLL_LONGTERM GUP-fast writing to file-backed mappings

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Message-ID: <db733020-c6c7-43f9-9cbf-0e5fb18b2f01@lucifer.local>
Date:   Tue, 2 May 2023 08:46:33 +0100
From:   Lorenzo Stoakes <lstoakes@...il.com>
To:     kernel test robot <lkp@...el.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        llvm@...ts.linux.dev, oe-kbuild-all@...ts.linux.dev,
        Jason Gunthorpe <jgg@...pe.ca>, Jens Axboe <axboe@...nel.dk>,
        Matthew Wilcox <willy@...radead.org>,
        Dennis Dalessandro <dennis.dalessandro@...nelisnetworks.com>,
        Leon Romanovsky <leon@...nel.org>,
        Christian Benvenuti <benve@...co.com>,
        Nelson Escobar <neescoba@...co.com>,
        Bernard Metzler <bmt@...ich.ibm.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Ian Rogers <irogers@...gle.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Bjorn Topel <bjorn@...nel.org>,
        Magnus Karlsson <magnus.karlsson@...el.com>,
        Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
        Jonathan Lemon <jonathan.lemon@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Christian Brauner <brauner@...nel.org>
Subject: Re: [PATCH v6 3/3] mm/gup: disallow FOLL_LONGTERM GUP-fast writing
 to file-backed mappings

On Tue, May 02, 2023 at 11:33:29AM +0800, kernel test robot wrote:
> Hi Lorenzo,
>
> kernel test robot noticed the following build warnings:
>
> [auto build test WARNING on akpm-mm/mm-everything]
>
> url:    https://github.com/intel-lab-lkp/linux/commits/Lorenzo-Stoakes/mm-mmap-separate-writenotify-and-dirty-tracking-logic/20230502-071520
> base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
> patch link:    https://lore.kernel.org/r/dee4f4ad6532b0f94d073da263526de334d5d7e0.1682981880.git.lstoakes%40gmail.com
> patch subject: [PATCH v6 3/3] mm/gup: disallow FOLL_LONGTERM GUP-fast writing to file-backed mappings
> config: arm-randconfig-r013-20230502 (https://download.01.org/0day-ci/archive/20230502/202305021142.vBYXxxEh-lkp@intel.com/config)
> compiler: clang version 17.0.0 (https://github.com/llvm/llvm-project b1465cd49efcbc114a75220b153f5a055ce7911f)
> reproduce (this is a W=1 build):
>         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>         chmod +x ~/bin/make.cross
>         # install arm cross compiling tool for clang build
>         # apt-get install binutils-arm-linux-gnueabi
>         # https://github.com/intel-lab-lkp/linux/commit/602bb9fab888bd9176b8eeb80a0da68499c343ed
>         git remote add linux-review https://github.com/intel-lab-lkp/linux
>         git fetch --no-tags linux-review Lorenzo-Stoakes/mm-mmap-separate-writenotify-and-dirty-tracking-logic/20230502-071520
>         git checkout 602bb9fab888bd9176b8eeb80a0da68499c343ed
>         # save the config file
>         mkdir build_dir && cp config build_dir/.config
>         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=arm olddefconfig
>         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=arm SHELL=/bin/bash
>
> If you fix the issue, kindly add following tag where applicable
> | Reported-by: kernel test robot <lkp@...el.com>
> | Link: https://lore.kernel.org/oe-kbuild-all/202305021142.vBYXxxEh-lkp@intel.com/
>
> All warnings (new ones prefixed by >>):
>
> >> mm/gup.c:114:49: warning: omitting the parameter name in a function definition is a C2x extension [-Wc2x-extensions]
>    static bool stabilise_mapping_rcu(struct folio *)
>                                                    ^
>    1 warning generated.
>
>
> vim +114 mm/gup.c
>
>    108
>    109	static void unlock_rcu(void)
>    110	{
>    111		rcu_read_unlock();
>    112	}
>    113	#else
>  > 114	static bool stabilise_mapping_rcu(struct folio *)
>    115	{
>    116		return true;
>    117	}
>    118
>
> --
> 0-DAY CI Kernel Test Service
> https://github.com/intel/lkp-tests

Am slightly surprised that's a C2x extension :)

-fix patch attached

----8<----
>From 829cb87ddd84e4496310b12d26e65de11d5b9e53 Mon Sep 17 00:00:00 2001
From: Lorenzo Stoakes <lstoakes@...il.com>
Date: Tue, 2 May 2023 08:40:48 +0100
Subject: [PATCH] mm/gup: disallow FOLL_LONGTERM GUP-fast writing to
 file-backed mappings

Fix compiler warning.

Signed-off-by: Lorenzo Stoakes <lstoakes@...il.com>
---
 mm/gup.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/gup.c b/mm/gup.c
index 431618048a03..ffc3caf120fc 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -111,7 +111,7 @@ static void unlock_rcu(void)
 	rcu_read_unlock();
 }
 #else
-static bool stabilise_mapping_rcu(struct folio *)
+static bool stabilise_mapping_rcu(struct folio *folio)
 {
 	return true;
 }
--
2.40.1