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Wed, 09 Apr 2025 18:45:54 -0400 X-MC-Unique: PrFDpZr2ND-Vh4XOVp0KLg-1 X-Mimecast-MFC-AGG-ID: PrFDpZr2ND-Vh4XOVp0KLg_1744238752 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 5B0CD1801A1A; Wed, 9 Apr 2025 22:45:52 +0000 (UTC) Received: from localhost (unknown [10.72.112.38]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 3A4EF180174E; Wed, 9 Apr 2025 22:45:49 +0000 (UTC) Date: Thu, 10 Apr 2025 06:45:45 +0800 From: Baoquan He To: SeongJae Park , kernel test robot Cc: Andrew Morton , Kemeng Shi , llvm@lists.linux.dev, oe-kbuild-all@lists.linux.dev, Linux Memory Management List , Tim Chen Subject: Re: [linux-next:master 1753/1936] mm/swapfile.c:1517:20: warning: function 'swap_is_last_ref' is not needed and will not be emitted Message-ID: References: <20250408173959.f501f65ec5d5e52cefe6b129@linux-foundation.org> <20250409165452.305371-1-sj@kernel.org> Precedence: bulk X-Mailing-List: llvm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: <20250409165452.305371-1-sj@kernel.org> X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: NorojRoyMqlnmAbi3HXtSkAmWOVaGo5KCZ8-A_xubUA_1744238752 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit On 04/09/25 at 09:54am, SeongJae Park wrote: > Hello, > > On Tue, 8 Apr 2025 17:39:59 -0700 Andrew Morton wrote: > > > On Tue, 8 Apr 2025 18:06:11 +0800 kernel test robot wrote: > > > > > tree: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master > > > head: 7702d0130dc002bab2c3571ddb6ff68f82d99aea > > > commit: 6bb001b6b64ec20d900d0d81294a0f031af59c3e [1753/1936] mm: swap: enable swap_entry_range_free() to drop any kind of last ref > > > config: hexagon-randconfig-001-20250408 (https://download.01.org/0day-ci/archive/20250408/202504081841.jbL7yL0r-lkp@intel.com/config) > > > compiler: clang version 21.0.0git (https://github.com/llvm/llvm-project 92c93f5286b9ff33f27ff694d2dc33da1c07afdd) > > > reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250408/202504081841.jbL7yL0r-lkp@intel.com/reproduce) > > > Hi lkp team, When I tried to reproduce, I got below failure. Please help check what's wrong with it. Thanks in advance. [~]# COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-21 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=hexagon olddefconfig Compiler will be installed in /root/0day Cannot find clang-21 under https://cdn.kernel.org/pub/tools/llvm/files Please set new URL env variable and rerun * crosstool provided by kernel org: export URL=https://cdn.kernel.org/pub/tools/llvm/files * crosstool provided by 0-Day CI: export URL=https://download.01.org/0day-ci/cross-package clang crosstool install failed Install clang compiler failed setup_crosstool failed > > > If you fix the issue in a separate patch/commit (i.e. not just a new version of > > > the same patch/commit), kindly add following tags > > > | Reported-by: kernel test robot > > > | Closes: https://lore.kernel.org/oe-kbuild-all/202504081841.jbL7yL0r-lkp@intel.com/ > > > > > > All warnings (new ones prefixed by >>): > > > > > > >> mm/swapfile.c:1517:20: warning: function 'swap_is_last_ref' is not needed and will not be emitted [-Wunneeded-internal-declaration] > > > > It's annoying that gcc warns about this. > > > > > 1517 | static inline bool swap_is_last_ref(unsigned char count) > > > | ^~~~~~~~~~~~~~~~ > > > 1 warning generated. > > > > > > > > > vim +/swap_is_last_ref +1517 mm/swapfile.c > > > > > > 1512 > > > 1513 /* > > > 1514 * Drop the last ref(1, SWAP_HAS_CACHE or SWAP_MAP_SHMEM) of swap entries, > > > 1515 * caller have to ensure all entries belong to the same cgroup and cluster. > > > 1516 */ > > > > 1517 static inline bool swap_is_last_ref(unsigned char count) > > > 1518 { > > > 1519 return (count == SWAP_HAS_CACHE) || (count == 1) || > > > 1520 (count == SWAP_MAP_SHMEM); > > > 1521 } > > > 1522 > > > > : static inline bool swap_is_last_ref(unsigned char count) > > : { > > : return (count == SWAP_HAS_CACHE) || (count == 1) || > > : (count == SWAP_MAP_SHMEM); > > : } > > : > > : static void swap_entries_free(struct swap_info_struct *si, > > : struct swap_cluster_info *ci, > > : swp_entry_t entry, unsigned int nr_pages) > > : { > > : unsigned long offset = swp_offset(entry); > > : unsigned char *map = si->swap_map + offset; > > : unsigned char *map_end = map + nr_pages; > > : > > : /* It should never free entries across different clusters */ > > : VM_BUG_ON(ci != offset_to_cluster(si, offset + nr_pages - 1)); > > : VM_BUG_ON(cluster_is_empty(ci)); > > : VM_BUG_ON(ci->count < nr_pages); > > : > > : ci->count -= nr_pages; > > : do { > > : VM_BUG_ON(!swap_is_last_ref(*map)); > > > > > > And it's annoying that VM_BUG_ON() doesn't reference its arg when > > CONFIG_DEBUG_VM=n. > > > > I'll add this: > > > > --- a/mm/swapfile.c~mm-swap-enable-swap_entry_range_free-to-drop-any-kind-of-last-ref-fix > > +++ a/mm/swapfile.c > > @@ -1514,11 +1514,13 @@ fallback: > > * Drop the last ref(1, SWAP_HAS_CACHE or SWAP_MAP_SHMEM) of swap entries, > > * caller have to ensure all entries belong to the same cgroup and cluster. > > */ > > +#ifdef CONFIG_DEBUG_VM > > static inline bool swap_is_last_ref(unsigned char count) > > { > > return (count == SWAP_HAS_CACHE) || (count == 1) || > > (count == SWAP_MAP_SHMEM); > > } > > +#endif > > > > static void swap_entries_free(struct swap_info_struct *si, > > struct swap_cluster_info *ci, > > _ > > This makes my build fails when CONFIG_DEBUG_VM is unset as below. > > linux/mm/swapfile.c: In function ‘swap_entries_free’: > linux/mm/swapfile.c:1565:28: error: implicit declaration of function ‘swap_is_last_ref’; did you mean ‘swap_is_last_map’? [-Werror=implicit-function-declaration] > 1565 | VM_BUG_ON(!swap_is_last_ref(*map)); > | ^~~~~~~~~~~~~~~~ > linux/include/linux/build_bug.h:30:63: note: in definition of macro ‘BUILD_BUG_ON_INVALID’ > 30 | #define BUILD_BUG_ON_INVALID(e) ((void)(sizeof((__force long)(e)))) > | ^ > linux/mm/swapfile.c:1565:17: note: in expansion of macro ‘VM_BUG_ON’ > 1565 | VM_BUG_ON(!swap_is_last_ref(*map)); > | ^~~~~~~~~ > cc1: some warnings being treated as errors > > Maybe we can open-code the condition, or add a macro implementation of > swap_is_last_ref() for !CONFIG_DEBUG_VM case? I think we shold do the similar thing as this commit does: 6e8e04291d81 mm/zsmalloc: add __maybe_unused attribute for is_first_zpdesc() Just add a __maybe_unused attribute to mute the warning. I haven't tested it because the reproducer failed in my side. diff --git a/mm/swapfile.c b/mm/swapfile.c index 2887ed5d34cc..08b52346cc39 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -1539,7 +1539,7 @@ static bool swap_entries_put_map_nr(struct swap_info_struct *si, * Drop the last ref(1, SWAP_HAS_CACHE or SWAP_MAP_SHMEM) of swap entries, * caller have to ensure all entries belong to the same cgroup and cluster. */ -static inline bool swap_is_last_ref(unsigned char count) +static inline bool __maybe_unused swap_is_last_ref(unsigned char count) { return (count == SWAP_HAS_CACHE) || (count == 1) || (count == SWAP_MAP_SHMEM);