[mszeredi-fuse:extent-map-v4 26/29] fs/fuse/backing.c:159:undefined reference to `fsdev_dax_from_file'

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

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse.git extent-map-v4
head:   4b2887a36cd547c2e59952e0a202094c82d9c6a9
commit: 70cf1c0aef205f9384095f2536c61b945d320ef6 [26/29] fuse: add support for opening dax device as backing
config: x86_64-rhel-9.4-bpf (https://download.01.org/0day-ci/archive/20261009/202610090144.uLZlv2nF-lkp@intel.com/config)
compiler: gcc-14 (Debian 14.2.0-19) 14.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20261009/202610090144.uLZlv2nF-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/202610090144.uLZlv2nF-lkp@intel.com/

All errors (new ones prefixed by >>):

   ld: vmlinux.o: in function `fuse_backing_open_file':
>> fs/fuse/backing.c:159:(.text+0xc0259d): undefined reference to `fsdev_dax_from_file'


vim +159 fs/fuse/backing.c

   130	
   131	static int fuse_backing_open_file(struct fuse_conn *fc, struct fuse_backing *fb, struct file *file)
   132	{
   133		struct inode *inode = file_inode(file);
   134		struct dax_device *daxdev;
   135		int err;
   136	
   137		switch (inode->i_mode & S_IFMT) {
   138		case S_IFREG:
   139			/* TODO: relax CAP_SYS_ADMIN once backing files are visible to lsof */
   140			if (!fc->passthrough || !capable(CAP_SYS_ADMIN))
   141				return -EPERM;
   142	
   143			if (inode->i_sb->s_stack_depth >= fc->max_stack_depth)
   144				return -ELOOP;
   145	
   146			fb->type = FUSE_BACKING_PATH;
   147			fb->path = file->f_path;
   148			path_get(&fb->path);
   149			fb->cred = get_current_cred();
   150			return 0;
   151	
   152		case S_IFCHR:
   153			if (!fc->passthrough || !fc->backing_id_64)
   154				return -EINVAL;
   155	
   156			if (!IS_ENABLED(CONFIG_DEV_DAX_FSDEV))
   157				return -EINVAL;
   158	
 > 159			daxdev = fsdev_dax_from_file(file);
   160			if (!daxdev)
   161				return -EINVAL;
   162	
   163			err = -EPERM;
   164			if (capable(CAP_SYS_RAWIO)) {
   165				err = fs_dax_get(daxdev, fb, &fuse_dax_holder_ops);
   166				if (!err) {
   167					fb->type = FUSE_BACKING_DAXDEV;
   168					fb->dax_dev = daxdev;
   169				}
   170			}
   171			put_dax(daxdev);
   172			return err;
   173	
   174		case S_IFDIR:
   175			return -EISDIR;
   176	
   177		default:
   178			return -EINVAL;
   179		}
   180	}
   181	

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