linux-kernel - Re: [rcu:willy-maple 189/202] mm/mmap.c:2830:18: warning: variable 'ma

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Message-ID: <20210203154043.gapbdfft2kahirm2@revolver>
Date:   Wed, 3 Feb 2021 15:42:23 +0000
From:   Liam Howlett <liam.howlett@...cle.com>
To:     kernel test robot <lkp@...el.com>
CC:     "kbuild-all@...ts.01.org" <kbuild-all@...ts.01.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [rcu:willy-maple 189/202] mm/mmap.c:2830:18: warning: variable
 'ma_lock' set but not used

* kernel test robot <lkp@...el.com> [210202 22:08]:
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git willy-maple
> head:   7e346d2845b4bd77663394f39fa70456e0084c86
> commit: e40a951e09ed0e66dbd646f938df19c876915b9d [189/202] mm: Remove vma linked list.
> config: alpha-defconfig (attached as .config)
> compiler: alpha-linux-gcc (GCC) 9.3.0
> 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
>         # https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git/commit/?id=e40a951e09ed0e66dbd646f938df19c876915b9d
>         git remote add rcu https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git
>         git fetch --no-tags rcu willy-maple
>         git checkout e40a951e09ed0e66dbd646f938df19c876915b9d
>         # save the attached .config to linux build tree
>         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=alpha 
> 
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@...el.com>
> 

Hello!

Yes, this can be safely dropped.  I will fix this in my next patch
revision.

Thank you,
Liam


> All warnings (new ones prefixed by >>):
> 
>    mm/mmap.c:2366:5: warning: no previous prototype for 'do_mas_align_munmap' [-Wmissing-prototypes]
>     2366 | int do_mas_align_munmap(struct ma_state *mas, struct vm_area_struct *vma,
>          |     ^~~~~~~~~~~~~~~~~~~
>    mm/mmap.c: In function '__do_sys_remap_file_pages':
> >> mm/mmap.c:2830:18: warning: variable 'ma_lock' set but not used [-Wunused-but-set-variable]
>     2830 |  struct ma_state ma_lock;
>          |                  ^~~~~~~
> 
> 
> vim +/ma_lock +2830 mm/mmap.c
> 
>   2824	
>   2825		struct mm_struct *mm = current->mm;
>   2826		struct vm_area_struct *vma;
>   2827		unsigned long populate = 0;
>   2828		unsigned long ret = -EINVAL;
>   2829		struct file *file;
> > 2830		struct ma_state ma_lock;
>   2831		MA_STATE(mas, &mm->mm_mt, start, start);
>   2832	
>   2833		pr_warn_once("%s (%d) uses deprecated remap_file_pages() syscall. See Documentation/vm/remap_file_pages.rst.\n",
>   2834			     current->comm, current->pid);
>   2835	
>   2836		if (prot)
>   2837			return ret;
>   2838	
>   2839		start = start & PAGE_MASK;
>   2840		size = size & PAGE_MASK;
>   2841		if (start + size <= start)
>   2842			return ret;
>   2843	
>   2844		/* Does pgoff wrap? */
>   2845		if (pgoff + (size >> PAGE_SHIFT) < pgoff)
>   2846			return ret;
>   2847	
>   2848		if (mmap_write_lock_killable(mm))
>   2849			return -EINTR;
>   2850	
>   2851		mas_set(&mas, start);
>   2852		vma = mas_walk(&mas);
>   2853		ma_lock = mas;
>   2854	
>   2855		if (!vma || !(vma->vm_flags & VM_SHARED))
>   2856			goto out;
>   2857	
>   2858		if (!vma->vm_file)
>   2859			goto out;
>   2860	
>   2861		if (start + size > vma->vm_end) {
>   2862			struct vm_area_struct *prev, *next;
>   2863	
>   2864			prev = vma;
>   2865			mas_for_each(&mas, next, start + size) {
>   2866				/* hole between vmas ? */
>   2867				if (next->vm_start != prev->vm_end)
>   2868					goto out;
>   2869	
>   2870				if (next->vm_file != vma->vm_file)
>   2871					goto out;
>   2872	
>   2873				if (next->vm_flags != vma->vm_flags)
>   2874					goto out;
>   2875	
>   2876				if (start + size <= next->vm_end)
>   2877					break;
>   2878	
>   2879				prev = next;
>   2880			}
>   2881	
>   2882			if (!next)
>   2883				goto out;
>   2884		}
>   2885	
>   2886		prot |= vma->vm_flags & VM_READ ? PROT_READ : 0;
>   2887		prot |= vma->vm_flags & VM_WRITE ? PROT_WRITE : 0;
>   2888		prot |= vma->vm_flags & VM_EXEC ? PROT_EXEC : 0;
>   2889	
>   2890		flags &= MAP_NONBLOCK;
>   2891		flags |= MAP_SHARED | MAP_FIXED | MAP_POPULATE;
>   2892	
>   2893		file = get_file(vma->vm_file);
>   2894		ret = do_mmap(vma->vm_file, start, size,
>   2895				prot, flags, pgoff, &populate, NULL);
>   2896		fput(file);
>   2897	out:
>   2898		mmap_write_unlock(mm);
>   2899		if (populate)
>   2900			mm_populate(ret, populate);
>   2901		if (!IS_ERR_VALUE(ret))
>   2902			ret = 0;
>   2903		return ret;
>   2904	}
>   2905	
> 
> ---
> 0-DAY CI Kernel Test Service, Intel Corporation
> https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org