Re: [PATCH 1/4] exportfs: add flag to indicate local file handles

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

Hi Christian,

kernel test robot noticed the following build warnings:

[auto build test WARNING on 74e20c5946ab3f8ad959ea34f63f21e157d3ebae]

url:    https://github.com/intel-lab-lkp/linux/commits/Christian-Brauner/exportfs-add-flag-to-indicate-local-file-handles/20241201-211528
base:   74e20c5946ab3f8ad959ea34f63f21e157d3ebae
patch link:    https://lore.kernel.org/r/20241201-work-exportfs-v1-1-b850dda4502a%40kernel.org
patch subject: [PATCH 1/4] exportfs: add flag to indicate local file handles
config: arm-footbridge_defconfig (https://download.01.org/0day-ci/archive/20241201/202412012337.HpTm35G5-lkp@intel.com/config)
compiler: clang version 20.0.0git (https://github.com/llvm/llvm-project 592c0fe55f6d9a811028b5f3507be91458ab2713)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20241201/202412012337.HpTm35G5-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/202412012337.HpTm35G5-lkp@intel.com/

All warnings (new ones prefixed by >>):

   In file included from fs/nfsd/export.c:19:
   In file included from include/linux/sunrpc/svc_xprt.h:11:
   In file included from include/linux/sunrpc/svc.h:17:
   In file included from include/linux/sunrpc/xdr.h:17:
   In file included from include/linux/scatterlist.h:8:
   In file included from include/linux/mm.h:2223:
   include/linux/vmstat.h:518:36: warning: arithmetic between different enumeration types ('enum node_stat_item' and 'enum lru_list') [-Wenum-enum-conversion]
     518 |         return node_stat_name(NR_LRU_BASE + lru) + 3; // skip "nr_"
         |                               ~~~~~~~~~~~ ^ ~~~
>> fs/nfsd/export.c:458:6: warning: variable 'nop' is uninitialized when used here [-Wuninitialized]
     458 |         if (nop && nop->flags & EXPORT_OP_LOCAL_FILE_HANDLE) {
         |             ^~~
   fs/nfsd/export.c:420:37: note: initialize the variable 'nop' to silence this warning
     420 |         const struct export_operations *nop;
         |                                            ^
         |                                             = NULL
   fs/nfsd/export.c:1045:17: warning: variable 'inode' set but not used [-Wunused-but-set-variable]
    1045 |         struct inode            *inode;
         |                                  ^
   3 warnings generated.


vim +/nop +458 fs/nfsd/export.c

   416	
   417	static int check_export(struct path *path, int *flags, unsigned char *uuid)
   418	{
   419		struct inode *inode = d_inode(path->dentry);
   420		const struct export_operations *nop;
   421	
   422		/*
   423		 * We currently export only dirs, regular files, and (for v4
   424		 * pseudoroot) symlinks.
   425		 */
   426		if (!S_ISDIR(inode->i_mode) &&
   427		    !S_ISLNK(inode->i_mode) &&
   428		    !S_ISREG(inode->i_mode))
   429			return -ENOTDIR;
   430	
   431		/*
   432		 * Mountd should never pass down a writeable V4ROOT export, but,
   433		 * just to make sure:
   434		 */
   435		if (*flags & NFSEXP_V4ROOT)
   436			*flags |= NFSEXP_READONLY;
   437	
   438		/* There are two requirements on a filesystem to be exportable.
   439		 * 1:  We must be able to identify the filesystem from a number.
   440		 *       either a device number (so FS_REQUIRES_DEV needed)
   441		 *       or an FSID number (so NFSEXP_FSID or ->uuid is needed).
   442		 * 2:  We must be able to find an inode from a filehandle.
   443		 *       This means that s_export_op must be set.
   444		 * 3: We must not currently be on an idmapped mount.
   445		 */
   446		if (!(inode->i_sb->s_type->fs_flags & FS_REQUIRES_DEV) &&
   447		    !(*flags & NFSEXP_FSID) &&
   448		    uuid == NULL) {
   449			dprintk("exp_export: export of non-dev fs without fsid\n");
   450			return -EINVAL;
   451		}
   452	
   453		if (!exportfs_can_decode_fh(nop)) {
   454			dprintk("exp_export: export of invalid fs type.\n");
   455			return -EINVAL;
   456		}
   457	
 > 458		if (nop && nop->flags & EXPORT_OP_LOCAL_FILE_HANDLE) {
   459			dprintk("exp_export: filesystem only supports non-exportable file handles.\n");
   460			return -EINVAL;
   461		}
   462	
   463		if (is_idmapped_mnt(path->mnt)) {
   464			dprintk("exp_export: export of idmapped mounts not yet supported.\n");
   465			return -EINVAL;
   466		}
   467	
   468		if (inode->i_sb->s_export_op->flags & EXPORT_OP_NOSUBTREECHK &&
   469		    !(*flags & NFSEXP_NOSUBTREECHECK)) {
   470			dprintk("%s: %s does not support subtree checking!\n",
   471				__func__, inode->i_sb->s_type->name);
   472			return -EINVAL;
   473		}
   474		return 0;
   475	}
   476	

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