fs: fix build error with CONFIG_EXPORTFS=m or not defined

Many of the filesystems that call the generic exportfs helpers do not
select the EXPORTFS config.

Move generic_encode_ino32_fh() to libfs.c, same as generic_fh_to_*()
to avoid having to fix all those config dependencies.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202310262151.renqMvme-lkp@intel.com/
Fixes: dfaf653dc415 ("exportfs: make ->encode_fh() a mandatory method for NFS export")
Suggested-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Link: https://lore.kernel.org/r/20231026204540.143217-1-amir73il@gmail.com
Tested-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Christian Brauner <brauner@kernel.org>

fs/exportfs/expfs.c

@@ -342,47 +342,6 @@ static int get_name(const struct path *path, char *name, struct dentry *child)
 	return error;
 }
 
-/**
- * generic_encode_ino32_fh - generic export_operations->encode_fh function
- * @inode:   the object to encode
- * @fh:      where to store the file handle fragment
- * @max_len: maximum length to store there (in 4 byte units)
- * @parent:  parent directory inode, if wanted
- *
- * This generic encode_fh function assumes that the 32 inode number
- * is suitable for locating an inode, and that the generation number
- * can be used to check that it is still valid.  It places them in the
- * filehandle fragment where export_decode_fh expects to find them.
- */
-int generic_encode_ino32_fh(struct inode *inode, __u32 *fh, int *max_len,
-			    struct inode *parent)
-{
-	struct fid *fid = (void *)fh;
-	int len = *max_len;
-	int type = FILEID_INO32_GEN;
-
-	if (parent && (len < 4)) {
-		*max_len = 4;
-		return FILEID_INVALID;
-	} else if (len < 2) {
-		*max_len = 2;
-		return FILEID_INVALID;
-	}
-
-	len = 2;
-	fid->i32.ino = inode->i_ino;
-	fid->i32.gen = inode->i_generation;
-	if (parent) {
-		fid->i32.parent_ino = parent->i_ino;
-		fid->i32.parent_gen = parent->i_generation;
-		len = 4;
-		type = FILEID_INO32_GEN_PARENT;
-	}
-	*max_len = len;
-	return type;
-}
-EXPORT_SYMBOL_GPL(generic_encode_ino32_fh);
-
 #define FILEID_INO64_GEN_LEN 3
 
 /**

fs/libfs.c

@@ -1310,6 +1310,47 @@ ssize_t simple_attr_write_signed(struct file *file, const char __user *buf,
 }
 EXPORT_SYMBOL_GPL(simple_attr_write_signed);
 
+/**
+ * generic_encode_ino32_fh - generic export_operations->encode_fh function
+ * @inode:   the object to encode
+ * @fh:      where to store the file handle fragment
+ * @max_len: maximum length to store there (in 4 byte units)
+ * @parent:  parent directory inode, if wanted
+ *
+ * This generic encode_fh function assumes that the 32 inode number
+ * is suitable for locating an inode, and that the generation number
+ * can be used to check that it is still valid.  It places them in the
+ * filehandle fragment where export_decode_fh expects to find them.
+ */
+int generic_encode_ino32_fh(struct inode *inode, __u32 *fh, int *max_len,
+			    struct inode *parent)
+{
+	struct fid *fid = (void *)fh;
+	int len = *max_len;
+	int type = FILEID_INO32_GEN;
+
+	if (parent && (len < 4)) {
+		*max_len = 4;
+		return FILEID_INVALID;
+	} else if (len < 2) {
+		*max_len = 2;
+		return FILEID_INVALID;
+	}
+
+	len = 2;
+	fid->i32.ino = inode->i_ino;
+	fid->i32.gen = inode->i_generation;
+	if (parent) {
+		fid->i32.parent_ino = parent->i_ino;
+		fid->i32.parent_gen = parent->i_generation;
+		len = 4;
+		type = FILEID_INO32_GEN_PARENT;
+	}
+	*max_len = len;
+	return type;
+}
+EXPORT_SYMBOL_GPL(generic_encode_ino32_fh);
+
 /**
  * generic_fh_to_dentry - generic helper for the fh_to_dentry export operation
  * @sb:		filesystem to do the file handle conversion on

include/linux/exportfs.h

@@ -294,17 +294,12 @@ extern struct dentry *exportfs_decode_fh(struct vfsmount *mnt, struct fid *fid,
 /*
  * Generic helpers for filesystems.
  */
-#ifdef CONFIG_EXPORTFS
 int generic_encode_ino32_fh(struct inode *inode, __u32 *fh, int *max_len,
 			    struct inode *parent);
-#else
-#define generic_encode_ino32_fh NULL
-#endif
-
-extern struct dentry *generic_fh_to_dentry(struct super_block *sb,
+struct dentry *generic_fh_to_dentry(struct super_block *sb,
 	struct fid *fid, int fh_len, int fh_type,
 	struct inode *(*get_inode) (struct super_block *sb, u64 ino, u32 gen));
-extern struct dentry *generic_fh_to_parent(struct super_block *sb,
+struct dentry *generic_fh_to_parent(struct super_block *sb,
 	struct fid *fid, int fh_len, int fh_type,
 	struct inode *(*get_inode) (struct super_block *sb, u64 ino, u32 gen));