Re: [akpm-mm:mm-new 418/422] fs/orangefs/file.c:414:9: sparse: sparse: dereference of noderef expression

[Lorenzo Stoakes <lorenzo.stoakes@oracle.com>]

On Tue, Jan 20, 2026 at 05:10:47PM +0800, kernel test robot wrote:
> Hi Lorenzo,
>
> FYI, the error/warning was bisected to this commit, please ignore it if it's irrelevant.
>
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-new
> head:   e4348a62bb1acacafcdeb149c9363291fae08c0c
> commit: ccbdd8044f13617fe9f2bce61aed556314544664 [418/422] mm: update all remaining mmap_prepare users to use vma_flags_t
> config: arm-randconfig-r131-20260120 (https://download.01.org/0day-ci/archive/20260120/202601201701.IhxeGffs-lkp@intel.com/config)
> compiler: arm-linux-gnueabi-gcc (GCC) 11.5.0
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260120/202601201701.IhxeGffs-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/202601201701.IhxeGffs-lkp@intel.com/
>
> sparse warnings: (new ones prefixed by >>)
> >> fs/orangefs/file.c:414:9: sparse: sparse: dereference of noderef expression
>    fs/orangefs/file.c: note: in included file (through arch/arm/include/asm/cacheflush.h, include/linux/cacheflush.h, include/linux/highmem.h, ...):
>    include/linux/mm.h:1048:16: sparse: sparse: dereference of noderef expression
>    include/linux/mm.h:1048:16: sparse: sparse: dereference of noderef expression
>    include/linux/mm.h:1199:46: sparse: sparse: dereference of noderef expression
>    include/linux/mm.h:1199:46: sparse: sparse: dereference of noderef expression
>    fs/orangefs/file.c:415:9: sparse: sparse: dereference of noderef expression
>    include/linux/mm.h:1048:16: sparse: sparse: dereference of noderef expression
>    include/linux/mm.h:1048:16: sparse: sparse: dereference of noderef expression
>    include/linux/mm.h:1216:48: sparse: sparse: dereference of noderef expression
>    include/linux/mm.h:1216:48: sparse: sparse: dereference of noderef expression
> --
> >> fs/ramfs/file-nommu.c:267:40: sparse: sparse: dereference of noderef expression
> >> fs/ramfs/file-nommu.c:267:40: sparse: sparse: dereference of noderef expression
>    fs/ramfs/file-nommu.c: note: in included file:
>    include/linux/mm.h:1954:16: sparse: sparse: dereference of noderef expression
>    include/linux/mm.h:1954:16: sparse: sparse: dereference of noderef expression
>    include/linux/mm.h:1048:16: sparse: sparse: dereference of noderef expression
>    include/linux/mm.h:1954:16: sparse: sparse: dereference of noderef expression
>    include/linux/mm.h:1048:16: sparse: sparse: dereference of noderef expression
>
> vim +414 fs/orangefs/file.c
>
>    397
>    398	/*
>    399	 * Memory map a region of a file.
>    400	 */
>    401	static int orangefs_file_mmap_prepare(struct vm_area_desc *desc)
>    402	{
>    403		struct file *file = desc->file;
>    404		int ret;
>    405
>    406		ret = orangefs_revalidate_mapping(file_inode(file));
>    407		if (ret)
>    408			return ret;
>    409
>    410		gossip_debug(GOSSIP_FILE_DEBUG,
>    411			     "orangefs_file_mmap: called on %pD\n", file);
>    412
>    413		/* set the sequential readahead hint */
>  > 414		vma_desc_set_flags(desc, VMA_SEQ_READ_BIT);

This is totally valid? vma_flags_set_mask() (which is ultimately invoked) uses
ACCESS_PRIVATE() consistently.

I wonder if mk_vma_flags() is an issue as it ultimately does (const vma_flag_t
[]){ VMA_SEQ_READ_BIT } here that then gets 'dereferenced' by array access in
__mk_vma_flags().

Nothing is accessing __vma_flags in vma_flags_t directly however, it's all via
ACCESS_PRIVATE() as far as I can tell?

>    415		vma_desc_clear_flags(desc, VMA_RAND_READ_BIT);
>    416
>    417		file_accessed(file);
>    418		desc->vm_ops = &orangefs_file_vm_ops;
>    419		return 0;
>    420	}
>    421
>
> --
> 0-DAY CI Kernel Test Service
> https://github.com/intel/lkp-tests/wiki

Thanks, Lorenzo