path: root/drivers/s390/block/dcssblk.c

// SPDX-License-Identifier: GPL-2.0
/*
 * dcssblk.c -- the S/390 block driver for dcss memory
 *
 * Authors: Carsten Otte, Stefan Weinhuber, Gerald Schaefer
 */

#define pr_fmt(fmt) "dcssblk: " fmt

#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/ctype.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/blkdev.h>
#include <linux/completion.h>
#include <linux/interrupt.h>
#include <linux/uio.h>
#include <linux/dax.h>
#include <linux/io.h>
#include <asm/extmem.h>

#define DCSSBLK_NAME "dcssblk"
#define DCSSBLK_MINORS_PER_DISK 1
#define DCSSBLK_PARM_LEN 400
#define DCSS_BUS_ID_SIZE 20

static int dcssblk_open(struct gendisk *disk, blk_mode_t mode);
static void dcssblk_release(struct gendisk *disk);
static void dcssblk_submit_bio(struct bio *bio);
static long dcssblk_dax_direct_access(struct dax_device *dax_dev, pgoff_t pgoff,
		long nr_pages, enum dax_access_mode mode, void **kaddr,
		unsigned long *pfn);

static char dcssblk_segments[DCSSBLK_PARM_LEN] = "\0";

static int dcssblk_major;
static const struct block_device_operations dcssblk_devops = {
	.owner   	= THIS_MODULE,
	.submit_bio	= dcssblk_submit_bio,
	.open    	= dcssblk_open,
	.release 	= dcssblk_release,
};

static int dcssblk_dax_zero_page_range(struct dax_device *dax_dev,
				       pgoff_t pgoff, size_t nr_pages)
{
	long rc;
	void *kaddr;

	rc = dax_direct_access(dax_dev, pgoff, nr_pages, DAX_ACCESS,
			&kaddr, NULL);
	if (rc < 0)
		return dax_mem2blk_err(rc);

	memset(kaddr, 0, nr_pages << PAGE_SHIFT);
	dax_flush(dax_dev, kaddr, nr_pages << PAGE_SHIFT);
	return 0;
}

static const struct dax_operations dcssblk_dax_ops = {
	.direct_access = dcssblk_dax_direct_access,
	.zero_page_range = dcssblk_dax_zero_page_range,
};

struct dcssblk_dev_info {
	struct list_head lh;
	struct device dev;
	char segment_name[DCSS_BUS_ID_SIZE];
	atomic_t use_count;
	struct gendisk *gd;
	unsigned long start;
	unsigned long end;
	int segment_type;
	unsigned char save_pending;
	unsigned char is_shared;
	int num_of_segments;
	struct list_head seg_list;
	struct dax_device *dax_dev;
	struct dev_pagemap pgmap;
	void *pgmap_addr;
};

struct segment_info {
	struct list_head lh;
	char segment_name[DCSS_BUS_ID_SIZE];
	unsigned long start;
	unsigned long end;
	int segment_type;
};

static ssize_t dcssblk_add_store(struct device * dev, struct device_attribute *attr, const char * buf,
				  size_t count);
static ssize_t dcssblk_remove_store(struct device * dev, struct device_attribute *attr, const char * buf,
				  size_t count);

static DEVICE_ATTR(add, S_IWUSR, NULL, dcssblk_add_store);
static DEVICE_ATTR(remove, S_IWUSR, NULL, dcssblk_remove_store);

static struct device *dcssblk_root_dev;

static LIST_HEAD(dcssblk_devices);
static struct rw_semaphore dcssblk_devices_sem;

/*
 * release function for segment device.
 */
static void
dcssblk_release_segment(struct device *dev)
{
	struct dcssblk_dev_info *dev_info;
	struct segment_info *entry, *temp;

	dev_info = container_of(dev, struct dcssblk_dev_info, dev);
	list_for_each_entry_safe(entry, temp, &dev_info->seg_list, lh) {
		list_del(&entry->lh);
		kfree(entry);
	}
	kfree(dev_info);
	module_put(THIS_MODULE);
}

/*
 * get a minor number. needs to be called with
 * down_write(&dcssblk_devices_sem) and the
 * device needs to be enqueued before the semaphore is
 * freed.