[openeuler:OLK-6.6 3195/3195] fs/mfs/data.c:185:24: warning: default initialization of an object of type 'struct vm_area_struct' with const member leaves the object uninitialized

[openeuler:OLK-6.6 3195/3195] fs/mfs/data.c:185:24: warning: default initialization of an object of type 'struct vm_area_struct' with const member leaves the object uninitialized

[kernel test robot]

tree:   https://gitee.com/openeuler/kernel.git OLK-6.6
head:   3abd440f300fe9312974a2d65499ca4ff872363a
commit: 693388489ac5689392e98cf86f58f115ffa9c9ce [3195/3195] mfs: Add basic data operation for MFS
config: loongarch-allyesconfig (https://download.01.org/0day-ci/archive/20251116/202511160338.SRwmoKy5-lkp@intel.com/config)
compiler: clang version 22.0.0git (https://github.com/llvm/llvm-project 0bba1e76581bad04e7d7f09f5115ae5e2989e0d9)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251116/202511160338.SRwmoKy5-lkp@intel.com/reproduce)

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 <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202511160338.SRwmoKy5-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> fs/mfs/data.c:185:24: warning: default initialization of an object of type 'struct vm_area_struct' with const member leaves the object uninitialized [-Wdefault-const-init-field-unsafe]
     185 |         struct vm_area_struct cvma, *vma, **vma_;
         |                               ^
   include/linux/mm_types.h:659:20: note: member 'vm_flags' declared 'const' here
     659 |                 const vm_flags_t vm_flags;
         |                                  ^
   fs/mfs/data.c:220:24: warning: default initialization of an object of type 'struct vm_area_struct' with const member leaves the object uninitialized [-Wdefault-const-init-field-unsafe]
     220 |         struct vm_area_struct cvma, *vma, **vma_;
         |                               ^
   include/linux/mm_types.h:659:20: note: member 'vm_flags' declared 'const' here
     659 |                 const vm_flags_t vm_flags;
         |                                  ^
   fs/mfs/data.c:214:12: warning: no previous prototype for function 'mfs_filemap_map_pages' [-Wmissing-prototypes]
     214 | vm_fault_t mfs_filemap_map_pages(struct vm_fault *vmf,
         |            ^
   fs/mfs/data.c:214:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
     214 | vm_fault_t mfs_filemap_map_pages(struct vm_fault *vmf,
         | ^
         | static 
   3 warnings generated.


vim +185 fs/mfs/data.c

   179	
   180	static vm_fault_t mfs_filemap_fault(struct vm_fault *vmf)
   181	{
   182		struct file *cfile, *file = vmf->vma->vm_file;
   183		struct mfs_file_info *fi = file->private_data;
   184		const struct vm_operations_struct *cvm_ops;
 > 185		struct vm_area_struct cvma, *vma, **vma_;
   186		vm_fault_t ret;
   187	
   188		vma = vmf->vma;
   189		memcpy(&cvma, vma, sizeof(struct vm_area_struct));
   190		cfile = fi->cache;
   191		cvm_ops = fi->cache_vm_ops;
   192		cvma.vm_file = cfile;
   193	
   194		if (unlikely(!cvm_ops->fault))
   195			return VM_FAULT_SIGBUS;
   196	
   197		(void)get_file(cfile);
   198	
   199		/*
   200		 * Dealing fault in mfs will call cachefile's fault eventually,
   201		 * hence we will change vmf->vma->vm_file to cachefile.
   202		 * When faulting concurrently, changing vmf->vma->vm_file is
   203		 * visible to other threads. Hence we use cvma to narrow the
   204		 * visibility. vmf->vma is const, so we use **vma_ to change.
   205		 */
   206		vma_ = (struct vm_area_struct **)&vmf->vma;
   207		*vma_ = &cvma;
   208		ret = cvm_ops->fault(vmf);
   209		*vma_ = vma;
   210		fput(cfile);
   211		return ret;
   212	}
   213	

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