fs: convert simple fs to new truncate

Convert simple filesystems: ramfs, configfs, sysfs, block_dev to new truncate
sequence.

Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/sysfs/inode.c

@@ -117,13 +117,11 @@ int sysfs_setattr(struct dentry *dentry, struct iattr *iattr)
 	if (error)
 		goto out;
 
-	iattr->ia_valid &= ~ATTR_SIZE; /* ignore size changes */
-
-	error = inode_setattr(inode, iattr);
-	if (error)
-		goto out;
+	/* this ignores size changes */
+	generic_setattr(inode, iattr);
 
 	error = sysfs_sd_setattr(sd, iattr);
+
 out:
 	mutex_unlock(&sysfs_mutex);
 	return error;