// SPDX-License-Identifier: GPL-2.0
/*
 * Author(s)......: Holger Smolinski <Holger.Smolinski@de.ibm.com>
 *                  Horst Hummel <Horst.Hummel@de.ibm.com>
 *                  Carsten Otte <Cotte@de.ibm.com>
 *                  Martin Schwidefsky <schwidefsky@de.ibm.com>
 * Bugreports.to..: <Linux390@de.ibm.com>
 * Copyright IBM Corp. 1999, 2001
 *
 * gendisk related functions for the dasd driver.
 *
 */

#include <linux/interrupt.h>
#include <linux/major.h>
#include <linux/fs.h>
#include <linux/blkpg.h>

#include <linux/uaccess.h>

#include "dasd_int.h"

static unsigned int queue_depth = 32;
static unsigned int nr_hw_queues = 4;
static void dasd_gd_free(struct gendisk *gdp);

module_param(queue_depth, uint, 0444);
MODULE_PARM_DESC(queue_depth, "Default queue depth for new DASD devices");

module_param(nr_hw_queues, uint, 0444);
MODULE_PARM_DESC(nr_hw_queues, "Default number of hardware queues for new DASD devices");

/*
 * Set device name.
 *   dasda - dasdz : 26 devices
 *   dasdaa - dasdzz : 676 devices, added up = 702
 *   dasdaaa - dasdzzz : 17576 devices, added up = 18278
 *   dasdaaaa - dasdzzzz : 456976 devices, added up = 475252
 */
static int dasd_name_format(char *prefix, int index, char *buf, int buflen)
{
        const int base = 'z' - 'a' + 1;
        char *begin = buf + strlen(prefix);
        char *end = buf + buflen;
        char *p;
        int unit;

        p = end - 1;
        *p = '\0';
        unit = base;
        do {
                if (p == begin)
                        return -EINVAL;
                *--p = 'a' + (index % unit);
                index = (index / unit) - 1;
        } while (index >= 0);

        memmove(begin, p, end - p);
        memcpy(buf, prefix, strlen(prefix));

        return 0;
}

/*
 * Allocate and register gendisk structure for device.
 */
int dasd_gendisk_alloc(struct dasd_block *block)
{
        struct queue_limits lim = {
                /*
                 * With page sized segments, each segment can be translated into
                 * one idaw/tidaw.
                 */
                .max_segment_size = PAGE_SIZE,
                .seg_boundary_mask = PAGE_SIZE - 1,
                .max_segments = USHRT_MAX,
        };
        struct gendisk *gdp;
        struct dasd_device *base;
        unsigned int devindex;
        int rc;

        /* Make sure the minor for this device exists. */
        base = block->base;
        devindex = base->devindex;
        if (devindex >= DASD_PER_MAJOR)
                return -EBUSY;

        block->tag_set.ops = &dasd_mq_ops;
        block->tag_set.cmd_size = sizeof(struct dasd_ccw_req);
        block->tag_set.nr_hw_queues = nr_hw_queues;
        block->tag_set.queue_depth = queue_depth;
        block->tag_set.numa_node = NUMA_NO_NODE;
        rc = blk_mq_alloc_tag_set(&block->tag_set);
        if (rc)
                return rc;

        gdp = blk_mq_alloc_disk(&block->tag_set, &lim, block);
        if (IS_ERR(gdp)) {
                blk_mq_free_tag_set(&block->tag_set);
                return PTR_ERR(gdp);
        }

        /* Initialize gendisk structure. */
        gdp->major = DASD_MAJOR;
        gdp->first_minor = devindex << DASD_PARTN_BITS;
        gdp->minors = 1 << DASD_PARTN_BITS;
        gdp->fops = &dasd_device_operations;

        rc = dasd_name_format("dasd", devindex, gdp->disk_name, sizeof(gdp->disk_name));
        if (rc) {
                DBF_DEV_EVENT(DBF_ERR, block->base,
                              "setting disk name failed, rc %d", rc);
                dasd_gd_free(gdp);
                return rc;
        }

        if (base->features & DASD_FEATURE_READONLY ||
            test_bit(DASD_FLAG_DEVICE_RO, &base->flags))
                set_disk_ro(gdp, 1);
        dasd_add_link_to_gendisk(gdp, base);
        block->gdp = gdp;
        set_capacity(block->gdp, 0);

        rc = device_add_disk(&base->cdev->dev, block->gdp, NULL);
        if (rc) {
                dasd_gendisk_free(block);
                return rc;
        }

        return 0;
}

/*
 * Free gendisk structure
 */
static void dasd_gd_free(struct gendisk *gd)
{
        del_gendisk(gd);
        gd->private_data = NULL;
        put_disk(gd);
}

/*
 * Unregister and free gendisk structure for device.
 */
void dasd_gendisk_free(struct dasd_block *block)
{
        if (block->gdp) {
                dasd_gd_free(block->gdp);
                block->gdp = NULL;
                blk_mq_free_tag_set(&block->tag_set);
        }
}

/*
 * Trigger a partition detection.
 */
int dasd_scan_partitions(struct dasd_block *block)
{
        struct file *bdev_file;
        int rc;

        bdev_file = bdev_file_open_by_dev(disk_devt(block->gdp), BLK_OPEN_READ,
                                       NULL, NULL);
        if (IS_ERR(bdev_file)) {
                DBF_DEV_EVENT(DBF_ERR, block->base,
                              "scan partitions error, blkdev_get returned %ld",
                              PTR_ERR(bdev_file));
                return -ENODEV;
        }

        mutex_lock(&block->gdp->open_mutex);
        rc = bdev_disk_changed(block->gdp, false);
        mutex_unlock(&block->gdp->open_mutex);
        if (rc)
                DBF_DEV_EVENT(DBF_ERR, block->base,
                                "scan partitions error, rc %d", rc);

        /*
         * Since the matching fput() call to the
         * bdev_file_open_by_path() in this function is not called before
         * dasd_destroy_partitions the offline open_count limit needs to be
         * increased from 0 to 1. This is done by setting device->bdev_file
         * (see dasd_generic_set_offline). As long as the partition detection
         * is running no offline should be allowed. That is why the assignment
         * to block->bdev_file is done AFTER the BLKRRPART ioctl.
         */
        block->bdev_file = bdev_file;
        return 0;
}

/*
 * Remove all inodes in the system for a device, delete the
 * partitions and make device unusable by setting its size to zero.
 */
void dasd_destroy_partitions(struct dasd_block *block)
{
        struct file *bdev_file;

        /*
         * Get the bdev_file pointer from the device structure and clear
         * device->bdev_file to lower the offline open_count limit again.
         */
        bdev_file = block->bdev_file;
        block->bdev_file = NULL;

        mutex_lock(&file_bdev(bdev_file)->bd_disk->open_mutex);
        bdev_disk_changed(file_bdev(bdev_file)->bd_disk, true);
        mutex_unlock(&file_bdev(bdev_file)->bd_disk->open_mutex);

        /* Matching blkdev_put to the blkdev_get in dasd_scan_partitions. */
        fput(bdev_file);
}

int dasd_gendisk_init(void)
{
        int rc;

        /* Register to static dasd major 94 */
        rc = register_blkdev(DASD_MAJOR, "dasd");
        if (rc != 0) {
                pr_warn("Registering the device driver with major number %d failed\n",
                        DASD_MAJOR);
                return rc;
        }
        return 0;
}

void dasd_gendisk_exit(void)
{
        unregister_blkdev(DASD_MAJOR, "dasd");
}