ext4: export iov_shorten from kernel for ext4's use

Export iov_shorten() from kernel so that ext4 can
truncate too-large writes to bitmapped files.
Signed-off-by: NEric Sandeen <sandeen@redhat.com>

fs/read_write.c

@@ -446,6 +446,7 @@ unsigned long iov_shorten(struct iovec *iov, unsigned long nr_segs, size_t to)
 	}
 	return seg;
 }
+EXPORT_SYMBOL(iov_shorten);
 
 ssize_t do_sync_readv_writev(struct file *filp, const struct iovec *iov,
 		unsigned long nr_segs, size_t len, loff_t *ppos, iov_fn_t fn)