// SPDX-License-Identifier: GPL-2.0#include <unistd.h>#include <stdbool.h>#include <errno.h>#include <linux/kernel.h>#include <internal/lib.h> unsigned int page_size; static ssize_t ion(bool is_read, int fd, void *buf, size_t n){	void *buf_start = buf;	size_t left = n; 	while (left) {		/* buf must be treated as const if !is_read. */		ssize_t ret = is_read ? read(fd, buf, left) :					write(fd, buf, left); 		if (ret < 0 && errno == EINTR)			continue;		if (ret <= 0)			return ret; 		left -= ret;		buf  += ret;	} 	BUG_ON((size_t)(buf - buf_start) != n);	return n;} /* * Read exactly 'n' bytes or return an error. */ssize_t readn(int fd, void *buf, size_t n){	return ion(true, fd, buf, n);} ssize_t preadn(int fd, void *buf, size_t n, off_t offs){	size_t left = n; 	while (left) {		ssize_t ret = pread(fd, buf, left, offs); 		if (ret < 0 && errno == EINTR)			continue;		if (ret <= 0)			return ret; 		left -= ret;		buf  += ret;		offs += ret;	} 	return n;} /* * Write exactly 'n' bytes or return an error. */ssize_t writen(int fd, const void *buf, size_t n){	/* ion does not modify buf. */	return ion(false, fd, (void *)buf, n);}