[linux-next:master 6850/7915] mm/nommu.c:554:32: warning: variable 'prev' set but not used

[kernel test robot <lkp@intel.com>]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
head:   d4a0ae62a277377de396850ed4b709b6bd9b7326
commit: b3d7ba3cdf23cae36715a695c7569f617e57d39d [6850/7915] mm: Remove the vma linked list
config: h8300-buildonly-randconfig-r003-20220224 (https://download.01.org/0day-ci/archive/20220224/202202241525.pbzn4rHq-lkp@intel.com/config)
compiler: h8300-linux-gcc (GCC) 11.2.0
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/next/linux-next.git/commit/?id=b3d7ba3cdf23cae36715a695c7569f617e57d39d
        git remote add linux-next https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
        git fetch --no-tags linux-next master
        git checkout b3d7ba3cdf23cae36715a695c7569f617e57d39d
        # save the config file to linux build tree
        mkdir build_dir
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross O=build_dir ARCH=h8300 SHELL=/bin/bash

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All warnings (new ones prefixed by >>):

   In file included from arch/h8300/include/asm/page.h:5,
                    from arch/h8300/include/asm/thread_info.h:12,
                    from include/linux/thread_info.h:60,
                    from include/asm-generic/preempt.h:5,
                    from ./arch/h8300/include/generated/asm/preempt.h:1,
                    from include/linux/preempt.h:78,
                    from include/linux/spinlock.h:55,
                    from include/linux/mmzone.h:8,
                    from include/linux/gfp.h:6,
                    from include/linux/mm.h:10,
                    from mm/nommu.c:20:
   mm/nommu.c: In function 'kobjsize':
   include/asm-generic/page.h:89:51: warning: ordered comparison of pointer with null pointer [-Wextra]
      89 | #define virt_addr_valid(kaddr)  (((void *)(kaddr) >= (void *)PAGE_OFFSET) && \
         |                                                   ^~
   mm/nommu.c:79:23: note: in expansion of macro 'virt_addr_valid'
      79 |         if (!objp || !virt_addr_valid(objp))
         |                       ^~~~~~~~~~~~~~~
   mm/nommu.c: In function 'add_vma_to_mm':
>> mm/nommu.c:554:32: warning: variable 'prev' set but not used [-Wunused-but-set-variable]
     554 |         struct vm_area_struct *prev;
         |                                ^~~~


vim +/prev +554 mm/nommu.c

^1da177e4c3f41 Linus Torvalds    2005-04-16  544  
3034097a5017dd David Howells     2006-09-27  545  /*
8feae13110d60c David Howells     2009-01-08  546   * add a VMA into a process's mm_struct in the appropriate place in the list
8feae13110d60c David Howells     2009-01-08  547   * and tree and add to the address space's page tree also if not an anonymous
8feae13110d60c David Howells     2009-01-08  548   * page
c1e8d7c6a7a682 Michel Lespinasse 2020-06-08  549   * - should be called with mm->mmap_lock held writelocked
3034097a5017dd David Howells     2006-09-27  550   */
8feae13110d60c David Howells     2009-01-08  551  static void add_vma_to_mm(struct mm_struct *mm, struct vm_area_struct *vma)
^1da177e4c3f41 Linus Torvalds    2005-04-16  552  {
^1da177e4c3f41 Linus Torvalds    2005-04-16  553  	struct address_space *mapping;
4b662c6ba9aa9e Liam R. Howlett   2020-07-24 @554  	struct vm_area_struct *prev;
4b662c6ba9aa9e Liam R. Howlett   2020-07-24  555  	MA_STATE(mas, &mm->mm_mt, vma->vm_start, vma->vm_end);
8feae13110d60c David Howells     2009-01-08  556  
8feae13110d60c David Howells     2009-01-08  557  	BUG_ON(!vma->vm_region);
8feae13110d60c David Howells     2009-01-08  558  
8feae13110d60c David Howells     2009-01-08  559  	mm->map_count++;
8feae13110d60c David Howells     2009-01-08  560  	vma->vm_mm = mm;
^1da177e4c3f41 Linus Torvalds    2005-04-16  561  
^1da177e4c3f41 Linus Torvalds    2005-04-16  562  	/* add the VMA to the mapping */
^1da177e4c3f41 Linus Torvalds    2005-04-16  563  	if (vma->vm_file) {
^1da177e4c3f41 Linus Torvalds    2005-04-16  564  		mapping = vma->vm_file->f_mapping;
^1da177e4c3f41 Linus Torvalds    2005-04-16  565  
83cde9e8ba95d1 Davidlohr Bueso   2014-12-12  566  		i_mmap_lock_write(mapping);
^1da177e4c3f41 Linus Torvalds    2005-04-16  567  		flush_dcache_mmap_lock(mapping);
6b2dbba8b6ac4d Michel Lespinasse 2012-10-08  568  		vma_interval_tree_insert(vma, &mapping->i_mmap);
^1da177e4c3f41 Linus Torvalds    2005-04-16  569  		flush_dcache_mmap_unlock(mapping);
83cde9e8ba95d1 Davidlohr Bueso   2014-12-12  570  		i_mmap_unlock_write(mapping);
^1da177e4c3f41 Linus Torvalds    2005-04-16  571  	}
^1da177e4c3f41 Linus Torvalds    2005-04-16  572  
4b662c6ba9aa9e Liam R. Howlett   2020-07-24  573  	prev = mas_prev(&mas, 0);
4b662c6ba9aa9e Liam R. Howlett   2020-07-24  574  	mas_reset(&mas);
8feae13110d60c David Howells     2009-01-08  575  	/* add the VMA to the tree */
4b662c6ba9aa9e Liam R. Howlett   2020-07-24  576  	vma_mas_store(vma, &mas);
^1da177e4c3f41 Linus Torvalds    2005-04-16  577  }
^1da177e4c3f41 Linus Torvalds    2005-04-16  578  

:::::: The code at line 554 was first introduced by commit
:::::: 4b662c6ba9aa9ed30b302eade5a79e857fc881b4 mm: Remove rb tree.

:::::: TO: Liam R. Howlett <Liam.Howlett@Oracle.com>
:::::: CC: Liam R. Howlett <Liam.Howlett@oracle.com>

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org