[linux-block.git] / block / genhd.c

// SPDX-License-Identifier: GPL-2.0
/*
 *  gendisk handling
 *
 * Portions Copyright (C) 2020 Christoph Hellwig
 */

#include <linux/module.h>
#include <linux/ctype.h>
#include <linux/fs.h>
#include <linux/kdev_t.h>
#include <linux/kernel.h>
#include <linux/blkdev.h>
#include <linux/backing-dev.h>
#include <linux/init.h>
#include <linux/spinlock.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/slab.h>
#include <linux/kmod.h>
#include <linux/major.h>
#include <linux/mutex.h>
#include <linux/idr.h>
#include <linux/log2.h>
#include <linux/pm_runtime.h>
#include <linux/badblocks.h>
#include <linux/part_stat.h>
#include <linux/blktrace_api.h>

#include "blk-throttle.h"
#include "blk.h"
#include "blk-mq-sched.h"
#include "blk-rq-qos.h"
#include "blk-cgroup.h"

static struct kobject *block_depr;

/*
 * Unique, monotonically increasing sequential number associated with block
 * devices instances (i.e. incremented each time a device is attached).
 * Associating uevents with block devices in userspace is difficult and racy:
 * the uevent netlink socket is lossy, and on slow and overloaded systems has
 * a very high latency.
 * Block devices do not have exclusive owners in userspace, any process can set
 * one up (e.g. loop devices). Moreover, device names can be reused (e.g. loop0
 * can be reused again and again).
 * A userspace process setting up a block device and watching for its events
 * cannot thus reliably tell whether an event relates to the device it just set
 * up or another earlier instance with the same name.
 * This sequential number allows userspace processes to solve this problem, and
 * uniquely associate an uevent to the lifetime to a device.
 */
static atomic64_t diskseq;

/* for extended dynamic devt allocation, currently only one major is used */
#define NR_EXT_DEVT             (1 << MINORBITS)
static DEFINE_IDA(ext_devt_ida);

void set_capacity(struct gendisk *disk, sector_t sectors)
{
        if (sectors > BLK_DEV_MAX_SECTORS) {
                pr_warn_once("%s: truncate capacity from %lld to %lld\n",
                                disk->disk_name, sectors,
                                BLK_DEV_MAX_SECTORS);
                sectors = BLK_DEV_MAX_SECTORS;
        }

        bdev_set_nr_sectors(disk->part0, sectors);
}
EXPORT_SYMBOL(set_capacity);

/*
 * Set disk capacity and notify if the size is not currently zero and will not
 * be set to zero.  Returns true if a uevent was sent, otherwise false.
 */
bool set_capacity_and_notify(struct gendisk *disk, sector_t size)
{
        sector_t capacity = get_capacity(disk);
        char *envp[] = { "RESIZE=1", NULL };

        set_capacity(disk, size);

        /*
         * Only print a message and send a uevent if the gendisk is user visible
         * and alive.  This avoids spamming the log and udev when setting the
         * initial capacity during probing.
         */
        if (size == capacity ||
            !disk_live(disk) ||
            (disk->flags & GENHD_FL_HIDDEN))
                return false;

        pr_info("%s: detected capacity change from %lld to %lld\n",
                disk->disk_name, capacity, size);

        /*
         * Historically we did not send a uevent for changes to/from an empty
         * device.
         */
        if (!capacity || !size)
                return false;
        kobject_uevent_env(&disk_to_dev(disk)->kobj, KOBJ_CHANGE, envp);
        return true;
}
EXPORT_SYMBOL_GPL(set_capacity_and_notify);

static void part_stat_read_all(struct block_device *part,
                struct disk_stats *stat)
{
        int cpu;

        memset(stat, 0, sizeof(struct disk_stats));
        for_each_possible_cpu(cpu) {
                struct disk_stats *ptr = per_cpu_ptr(part->bd_stats, cpu);
                int group;

                for (group = 0; group < NR_STAT_GROUPS; group++) {
                        stat->nsecs[group] += ptr->nsecs[group];
                        stat->sectors[group] += ptr->sectors[group];
                        stat->ios[group] += ptr->ios[group];
                        stat->merges[group] += ptr->merges[group];
                }

                stat->io_ticks += ptr->io_ticks;
        }
}

static void bdev_count_inflight_rw(struct block_device *part,
                unsigned int inflight[2], bool mq_driver)
{
        int write = 0;
        int read = 0;
        int cpu;

        if (mq_driver) {
                blk_mq_in_driver_rw(part, inflight);
                return;
        }

        for_each_possible_cpu(cpu) {
                read += part_stat_local_read_cpu(part, in_flight[READ], cpu);
                write += part_stat_local_read_cpu(part, in_flight[WRITE], cpu);
        }

        /*
         * While iterating all CPUs, some IOs may be issued from a CPU already
         * traversed and complete on a CPU that has not yet been traversed,
         * causing the inflight number to be negative.
         */
        inflight[READ] = read > 0 ? read : 0;
        inflight[WRITE] = write > 0 ? write : 0;
}

/**
 * bdev_count_inflight - get the number of inflight IOs for a block device.
 *
 * @part: the block device.
 *
 * Inflight here means started IO accounting, from bdev_start_io_acct() for
 * bio-based block device, and from blk_account_io_start() for rq-based block
 * device.
 */
unsigned int bdev_count_inflight(struct block_device *part)
{
        unsigned int inflight[2] = {0};

        bdev_count_inflight_rw(part, inflight, false);

        return inflight[READ] + inflight[WRITE];
}
EXPORT_SYMBOL_GPL(bdev_count_inflight);

/*
 * Can be deleted altogether. Later.
 *
 */
#define BLKDEV_MAJOR_HASH_SIZE 255
static struct blk_major_name {
        struct blk_major_name *next;
        int major;
        char name[16];
#ifdef CONFIG_BLOCK_LEGACY_AUTOLOAD
        void (*probe)(dev_t devt);
#endif
} *major_names[BLKDEV_MAJOR_HASH_SIZE];
static DEFINE_MUTEX(major_names_lock);
static DEFINE_SPINLOCK(major_names_spinlock);

/* index in the above - for now: assume no multimajor ranges */
static inline int major_to_index(unsigned major)
{
        return major % BLKDEV_MAJOR_HASH_SIZE;
}

#ifdef CONFIG_PROC_FS
void blkdev_show(struct seq_file *seqf, off_t offset)
{
        struct blk_major_name *dp;

        spin_lock(&major_names_spinlock);
        for (dp = major_names[major_to_index(offset)]; dp; dp = dp->next)
                if (dp->major == offset)
                        seq_printf(seqf, "%3d %s\n", dp->major, dp->name);
        spin_unlock(&major_names_spinlock);
}
#endif /* CONFIG_PROC_FS */

/**
 * __register_blkdev - register a new block device
 *
 * @major: the requested major device number [1..BLKDEV_MAJOR_MAX-1]. If
 *         @major = 0, try to allocate any unused major number.
 * @name: the name of the new block device as a zero terminated string
 * @probe: pre-devtmpfs / pre-udev callback used to create disks when their
 *         pre-created device node is accessed. When a probe call uses
 *         add_disk() and it fails the driver must cleanup resources. This
 *         interface may soon be removed.
 *
 * The @name must be unique within the system.
 *
 * The return value depends on the @major input parameter:
 *
 *  - if a major device number was requested in range [1..BLKDEV_MAJOR_MAX-1]
 *    then the function returns zero on success, or a negative error code
 *  - if any unused major number was requested with @major = 0 parameter
 *    then the return value is the allocated major number in range
 *    [1..BLKDEV_MAJOR_MAX-1] or a negative error code otherwise
 *
 * See Documentation/admin-guide/devices.txt for the list of allocated
 * major numbers.
 *
 * Use register_blkdev instead for any new code.
 */
int __register_blkdev(unsigned int major, const char *name,
                void (*probe)(dev_t devt))
{
        struct blk_major_name **n, *p;
        int index, ret = 0;

        mutex_lock(&major_names_lock);

        /* temporary */
        if (major == 0) {
                for (index = ARRAY_SIZE(major_names)-1; index > 0; index--) {
                        if (major_names[index] == NULL)
                                break;
                }

                if (index == 0) {
                        printk("%s: failed to get major for %s\n",
                               __func__, name);
                        ret = -EBUSY;
                        goto out;
                }
                major = index;
                ret = major;
        }

        if (major >= BLKDEV_MAJOR_MAX) {
                pr_err("%s: major requested (%u) is greater than the maximum (%u) for %s\n",
                       __func__, major, BLKDEV_MAJOR_MAX-1, name);

                ret = -EINVAL;
                goto out;
        }

        p = kmalloc(sizeof(struct blk_major_name), GFP_KERNEL);
        if (p == NULL) {
                ret = -ENOMEM;
                goto out;
        }

        p->major = major;
#ifdef CONFIG_BLOCK_LEGACY_AUTOLOAD
        p->probe = probe;
#endif
        strscpy(p->name, name, sizeof(p->name));
        p->next = NULL;
        index = major_to_index(major);

        spin_lock(&major_names_spinlock);
        for (n = &major_names[index]; *n; n = &(*n)->next) {
                if ((*n)->major == major)
                        break;
        }
        if (!*n)
                *n = p;
        else
                ret = -EBUSY;
        spin_unlock(&major_names_spinlock);

        if (ret < 0) {
                printk("register_blkdev: cannot get major %u for %s\n",
                       major, name);
                kfree(p);
        }
out:
        mutex_unlock(&major_names_lock);
        return ret;
}
EXPORT_SYMBOL(__register_blkdev);

void unregister_blkdev(unsigned int major, const char *name)
{
        struct blk_major_name **n;
        struct blk_major_name *p = NULL;
        int index = major_to_index(major);

        mutex_lock(&major_names_lock);
        spin_lock(&major_names_spinlock);
        for (n = &major_names[index]; *n; n = &(*n)->next)
                if ((*n)->major == major)
                        break;
        if (!*n || strcmp((*n)->name, name)) {
                WARN_ON(1);
        } else {
                p = *n;
                *n = p->next;
        }
        spin_unlock(&major_names_spinlock);
        mutex_unlock(&major_names_lock);
        kfree(p);
}

EXPORT_SYMBOL(unregister_blkdev);

int blk_alloc_ext_minor(void)
{
        int idx;

        idx = ida_alloc_range(&ext_devt_ida, 0, NR_EXT_DEVT - 1, GFP_KERNEL);
        if (idx == -ENOSPC)
                return -EBUSY;
        return idx;
}

void blk_free_ext_minor(unsigned int minor)
{
        ida_free(&ext_devt_ida, minor);
}

void disk_uevent(struct gendisk *disk, enum kobject_action action)
{
        struct block_device *part;
        unsigned long idx;

        rcu_read_lock();
        xa_for_each(&disk->part_tbl, idx, part) {
                if (bdev_is_partition(part) && !bdev_nr_sectors(part))
                        continue;
                if (!kobject_get_unless_zero(&part->bd_device.kobj))
                        continue;

                rcu_read_unlock();
                kobject_uevent(bdev_kobj(part), action);
                put_device(&part->bd_device);
                rcu_read_lock();
        }
        rcu_read_unlock();
}
EXPORT_SYMBOL_GPL(disk_uevent);

int disk_scan_partitions(struct gendisk *disk, blk_mode_t mode)
{
        struct file *file;
        int ret = 0;

        if (!disk_has_partscan(disk))
                return -EINVAL;
        if (disk->open_partitions)
                return -EBUSY;

        /*
         * If the device is opened exclusively by current thread already, it's
         * safe to scan partitons, otherwise, use bd_prepare_to_claim() to
         * synchronize with other exclusive openers and other partition
         * scanners.
         */
        if (!(mode & BLK_OPEN_EXCL)) {
                ret = bd_prepare_to_claim(disk->part0, disk_scan_partitions,
                                          NULL);
                if (ret)
                        return ret;
        }

        set_bit(GD_NEED_PART_SCAN, &disk->state);
        file = bdev_file_open_by_dev(disk_devt(disk), mode & ~BLK_OPEN_EXCL,
                                     NULL, NULL);
        if (IS_ERR(file))
                ret = PTR_ERR(file);
        else
                fput(file);

        /*
         * If blkdev_get_by_dev() failed early, GD_NEED_PART_SCAN is still set,
         * and this will cause that re-assemble partitioned raid device will
         * creat partition for underlying disk.
         */
        clear_bit(GD_NEED_PART_SCAN, &disk->state);
        if (!(mode & BLK_OPEN_EXCL))
                bd_abort_claiming(disk->part0, disk_scan_partitions);
        return ret;
}

static void add_disk_final(struct gendisk *disk)
{
        struct device *ddev = disk_to_dev(disk);

        if (!(disk->flags & GENHD_FL_HIDDEN)) {
                /* Make sure the first partition scan will be proceed */
                if (get_capacity(disk) && disk_has_partscan(disk))
                        set_bit(GD_NEED_PART_SCAN, &disk->state);

                bdev_add(disk->part0, ddev->devt);
                if (get_capacity(disk))
                        disk_scan_partitions(disk, BLK_OPEN_READ);

                /*
                 * Announce the disk and partitions after all partitions are
                 * created. (for hidden disks uevents remain suppressed forever)
                 */
                dev_set_uevent_suppress(ddev, 0);
                disk_uevent(disk, KOBJ_ADD);
        }

        blk_apply_bdi_limits(disk->bdi, &disk->queue->limits);
        disk_add_events(disk);
        set_bit(GD_ADDED, &disk->state);
}

static int __add_disk(struct device *parent, struct gendisk *disk,
                      const struct attribute_group **groups,
                      struct fwnode_handle *fwnode)

{
        struct device *ddev = disk_to_dev(disk);
        int ret;

        if (WARN_ON_ONCE(bdev_nr_sectors(disk->part0) > BLK_DEV_MAX_SECTORS))
                return -EINVAL;

        if (queue_is_mq(disk->queue)) {
                /*
                 * ->submit_bio and ->poll_bio are bypassed for blk-mq drivers.
                 */
                if (disk->fops->submit_bio || disk->fops->poll_bio)
                        return -EINVAL;
        } else {
                if (!disk->fops->submit_bio)
                        return -EINVAL;
                bdev_set_flag(disk->part0, BD_HAS_SUBMIT_BIO);
        }

        /*
         * If the driver provides an explicit major number it also must provide
         * the number of minors numbers supported, and those will be used to
         * setup the gendisk.
         * Otherwise just allocate the device numbers for both the whole device
         * and all partitions from the extended dev_t space.
         */
        ret = -EINVAL;
        if (disk->major) {
                if (WARN_ON(!disk->minors))
                        goto out;

                if (disk->minors > DISK_MAX_PARTS) {
                        pr_err("block: can't allocate more than %d partitions\n",
                                DISK_MAX_PARTS);
                        disk->minors = DISK_MAX_PARTS;
                }
                if (disk->first_minor > MINORMASK ||
                    disk->minors > MINORMASK + 1 ||
                    disk->first_minor + disk->minors > MINORMASK + 1)
                        goto out;
        } else {
                if (WARN_ON(disk->minors))
                        goto out;

                ret = blk_alloc_ext_minor();
                if (ret < 0)
                        goto out;
                disk->major = BLOCK_EXT_MAJOR;
                disk->first_minor = ret;
        }

        /* delay uevents, until we scanned partition table */
        dev_set_uevent_suppress(ddev, 1);

        ddev->parent = parent;
        ddev->groups = groups;
        dev_set_name(ddev, "%s", disk->disk_name);
        if (fwnode)
                device_set_node(ddev, fwnode);
        if (!(disk->flags & GENHD_FL_HIDDEN))
                ddev->devt = MKDEV(disk->major, disk->first_minor);
        ret = device_add(ddev);
        if (ret)
                goto out_free_ext_minor;

        ret = disk_alloc_events(disk);
        if (ret)
                goto out_device_del;

        ret = sysfs_create_link(block_depr, &ddev->kobj,
                                kobject_name(&ddev->kobj));
        if (ret)
                goto out_device_del;

        /*
         * avoid probable deadlock caused by allocating memory with
         * GFP_KERNEL in runtime_resume callback of its all ancestor
         * devices
         */
        pm_runtime_set_memalloc_noio(ddev, true);

        disk->part0->bd_holder_dir =
                kobject_create_and_add("holders", &ddev->kobj);
        if (!disk->part0->bd_holder_dir) {
                ret = -ENOMEM;
                goto out_del_block_link;
        }
        disk->slave_dir = kobject_create_and_add("slaves", &ddev->kobj);
        if (!disk->slave_dir) {
                ret = -ENOMEM;
                goto out_put_holder_dir;
        }

        ret = blk_register_queue(disk);
        if (ret)
                goto out_put_slave_dir;

        if (!(disk->flags & GENHD_FL_HIDDEN)) {
                ret = bdi_register(disk->bdi, "%u:%u",
                                   disk->major, disk->first_minor);
                if (ret)
                        goto out_unregister_queue;
                bdi_set_owner(disk->bdi, ddev);
                ret = sysfs_create_link(&ddev->kobj,
                                        &disk->bdi->dev->kobj, "bdi");
                if (ret)
                        goto out_unregister_bdi;
        } else {
                /*
                 * Even if the block_device for a hidden gendisk is not
                 * registered, it needs to have a valid bd_dev so that the
                 * freeing of the dynamic major works.
                 */
                disk->part0->bd_dev = MKDEV(disk->major, disk->first_minor);
        }
        return 0;

out_unregister_bdi:
        if (!(disk->flags & GENHD_FL_HIDDEN))
                bdi_unregister(disk->bdi);
out_unregister_queue:
        blk_unregister_queue(disk);
        rq_qos_exit(disk->queue);
out_put_slave_dir:
        kobject_put(disk->slave_dir);
        disk->slave_dir = NULL;
out_put_holder_dir:
        kobject_put(disk->part0->bd_holder_dir);
out_del_block_link:
        sysfs_remove_link(block_depr, dev_name(ddev));
        pm_runtime_set_memalloc_noio(ddev, false);
out_device_del:
        device_del(ddev);
out_free_ext_minor:
        if (disk->major == BLOCK_EXT_MAJOR)
                blk_free_ext_minor(disk->first_minor);
out:
        return ret;
}

/**
 * add_disk_fwnode - add disk information to kernel list with fwnode
 * @parent: parent device for the disk
 * @disk: per-device partitioning information
 * @groups: Additional per-device sysfs groups
 * @fwnode: attached disk fwnode
 *
 * This function registers the partitioning information in @disk
 * with the kernel. Also attach a fwnode to the disk device.
 */
int __must_check add_disk_fwnode(struct device *parent, struct gendisk *disk,
                                 const struct attribute_group **groups,
                                 struct fwnode_handle *fwnode)
{
        struct blk_mq_tag_set *set;
        unsigned int memflags;
        int ret;

        if (queue_is_mq(disk->queue)) {
                set = disk->queue->tag_set;
                memflags = memalloc_noio_save();
                down_read(&set->update_nr_hwq_lock);
                ret = __add_disk(parent, disk, groups, fwnode);
                up_read(&set->update_nr_hwq_lock);
                memalloc_noio_restore(memflags);
        } else {
                ret = __add_disk(parent, disk, groups, fwnode);
        }

        /*
         * add_disk_final() needn't to read `nr_hw_queues`, so move it out
         * of read lock `set->update_nr_hwq_lock` for avoiding unnecessary
         * lock dependency on `disk->open_mutex` from scanning partition.
         */
        if (!ret)
                add_disk_final(disk);
        return ret;
}
EXPORT_SYMBOL_GPL(add_disk_fwnode);

/**
 * device_add_disk - add disk information to kernel list
 * @parent: parent device for the disk
 * @disk: per-device partitioning information
 * @groups: Additional per-device sysfs groups
 *
 * This function registers the partitioning information in @disk
 * with the kernel.
 */
int __must_check device_add_disk(struct device *parent, struct gendisk *disk,
                                 const struct attribute_group **groups)
{
        return add_disk_fwnode(parent, disk, groups, NULL);
}
EXPORT_SYMBOL(device_add_disk);

static void blk_report_disk_dead(struct gendisk *disk, bool surprise)
{
        struct block_device *bdev;
        unsigned long idx;

        /*
         * On surprise disk removal, bdev_mark_dead() may call into file
         * systems below. Make it clear that we're expecting to not hold
         * disk->open_mutex.
         */
        lockdep_assert_not_held(&disk->open_mutex);

        rcu_read_lock();
        xa_for_each(&disk->part_tbl, idx, bdev) {
                if (!kobject_get_unless_zero(&bdev->bd_device.kobj))
                        continue;
                rcu_read_unlock();

                bdev_mark_dead(bdev, surprise);

                put_device(&bdev->bd_device);
                rcu_read_lock();
        }
        rcu_read_unlock();
}

static bool __blk_mark_disk_dead(struct gendisk *disk)
{
        /*
         * Fail any new I/O.
         */
        if (test_and_set_bit(GD_DEAD, &disk->state))
                return false;

        if (test_bit(GD_OWNS_QUEUE, &disk->state))
                blk_queue_flag_set(QUEUE_FLAG_DYING, disk->queue);

        /*
         * Stop buffered writers from dirtying pages that can't be written out.
         */
        set_capacity(disk, 0);

        /*
         * Prevent new I/O from crossing bio_queue_enter().
         */
        return blk_queue_start_drain(disk->queue);
}

/**
 * blk_mark_disk_dead - mark a disk as dead
 * @disk: disk to mark as dead
 *
 * Mark as disk as dead (e.g. surprise removed) and don't accept any new I/O
 * to this disk.
 */
void blk_mark_disk_dead(struct gendisk *disk)
{
        __blk_mark_disk_dead(disk);
        blk_report_disk_dead(disk, true);
}
EXPORT_SYMBOL_GPL(blk_mark_disk_dead);

static void __del_gendisk(struct gendisk *disk)
{
        struct request_queue *q = disk->queue;
        struct block_device *part;
        unsigned long idx;
        bool start_drain;

        might_sleep();

        if (WARN_ON_ONCE(!disk_live(disk) && !(disk->flags & GENHD_FL_HIDDEN)))
                return;

        disk_del_events(disk);

        /*
         * Prevent new openers by unlinked the bdev inode.
         */
        mutex_lock(&disk->open_mutex);
        xa_for_each(&disk->part_tbl, idx, part)
                bdev_unhash(part);
        mutex_unlock(&disk->open_mutex);

        /*
         * Tell the file system to write back all dirty data and shut down if
         * it hasn't been notified earlier.
         */
        if (!test_bit(GD_DEAD, &disk->state))
                blk_report_disk_dead(disk, false);

        /*
         * Drop all partitions now that the disk is marked dead.
         */
        mutex_lock(&disk->open_mutex);
        start_drain = __blk_mark_disk_dead(disk);
        if (start_drain)
                blk_freeze_acquire_lock(q);
        xa_for_each_start(&disk->part_tbl, idx, part, 1)
                drop_partition(part);
        mutex_unlock(&disk->open_mutex);

        if (!(disk->flags & GENHD_FL_HIDDEN)) {
                sysfs_remove_link(&disk_to_dev(disk)->kobj, "bdi");

                /*
                 * Unregister bdi before releasing device numbers (as they can
                 * get reused and we'd get clashes in sysfs).
                 */
                bdi_unregister(disk->bdi);
        }

        blk_unregister_queue(disk);

        kobject_put(disk->part0->bd_holder_dir);
        kobject_put(disk->slave_dir);
        disk->slave_dir = NULL;

        part_stat_set_all(disk->part0, 0);
        disk->part0->bd_stamp = 0;
        sysfs_remove_link(block_depr, dev_name(disk_to_dev(disk)));
        pm_runtime_set_memalloc_noio(disk_to_dev(disk), false);
        device_del(disk_to_dev(disk));

        blk_mq_freeze_queue_wait(q);

        blk_throtl_cancel_bios(disk);

        blk_sync_queue(q);
        blk_flush_integrity();

        if (queue_is_mq(q))
                blk_mq_cancel_work_sync(q);

        rq_qos_exit(q);

        /*
         * If the disk does not own the queue, allow using passthrough requests
         * again.  Else leave the queue frozen to fail all I/O.
         */
        if (!test_bit(GD_OWNS_QUEUE, &disk->state))
                __blk_mq_unfreeze_queue(q, true);
        else if (queue_is_mq(q))
                blk_mq_exit_queue(q);

        if (start_drain)
                blk_unfreeze_release_lock(q);
}

static void disable_elv_switch(struct request_queue *q)
{
        struct blk_mq_tag_set *set = q->tag_set;
        WARN_ON_ONCE(!queue_is_mq(q));

        down_write(&set->update_nr_hwq_lock);
        blk_queue_flag_set(QUEUE_FLAG_NO_ELV_SWITCH, q);
        up_write(&set->update_nr_hwq_lock);
}

/**
 * del_gendisk - remove the gendisk
 * @disk: the struct gendisk to remove
 *
 * Removes the gendisk and all its associated resources. This deletes the
 * partitions associated with the gendisk, and unregisters the associated
 * request_queue.
 *
 * This is the counter to the respective __device_add_disk() call.
 *
 * The final removal of the struct gendisk happens when its refcount reaches 0
 * with put_disk(), which should be called after del_gendisk(), if
 * __device_add_disk() was used.
 *
 * Drivers exist which depend on the release of the gendisk to be synchronous,
 * it should not be deferred.
 *
 * Context: can sleep
 */
void del_gendisk(struct gendisk *disk)
{
        struct blk_mq_tag_set *set;
        unsigned int memflags;

        if (!queue_is_mq(disk->queue)) {
                __del_gendisk(disk);
        } else {
                set = disk->queue->tag_set;

                disable_elv_switch(disk->queue);

                memflags = memalloc_noio_save();
                down_read(&set->update_nr_hwq_lock);
                __del_gendisk(disk);
                up_read(&set->update_nr_hwq_lock);
                memalloc_noio_restore(memflags);
        }
}
EXPORT_SYMBOL(del_gendisk);

/**
 * invalidate_disk - invalidate the disk
 * @disk: the struct gendisk to invalidate
 *
 * A helper to invalidates the disk. It will clean the disk's associated
 * buffer/page caches and reset its internal states so that the disk
 * can be reused by the drivers.
 *
 * Context: can sleep
 */
void invalidate_disk(struct gendisk *disk)
{
        struct block_device *bdev = disk->part0;

        invalidate_bdev(bdev);
        bdev->bd_mapping->wb_err = 0;
        set_capacity(disk, 0);
}
EXPORT_SYMBOL(invalidate_disk);

/* sysfs access to bad-blocks list. */
static ssize_t disk_badblocks_show(struct device *dev,
                                        struct device_attribute *attr,
                                        char *page)
{
        struct gendisk *disk = dev_to_disk(dev);

        if (!disk->bb)
                return sysfs_emit(page, "\n");

        return badblocks_show(disk->bb, page, 0);
}

static ssize_t disk_badblocks_store(struct device *dev,
                                        struct device_attribute *attr,
                                        const char *page, size_t len)
{
        struct gendisk *disk = dev_to_disk(dev);

        if (!disk->bb)
                return -ENXIO;

        return badblocks_store(disk->bb, page, len, 0);
}

#ifdef CONFIG_BLOCK_LEGACY_AUTOLOAD
static bool blk_probe_dev(dev_t devt)
{
        unsigned int major = MAJOR(devt);
        struct blk_major_name **n;

        mutex_lock(&major_names_lock);
        for (n = &major_names[major_to_index(major)]; *n; n = &(*n)->next) {
                if ((*n)->major == major && (*n)->probe) {
                        (*n)->probe(devt);
                        mutex_unlock(&major_names_lock);
                        return true;
                }
        }
        mutex_unlock(&major_names_lock);
        return false;
}

void blk_request_module(dev_t devt)
{
        int error;

        if (blk_probe_dev(devt))
                return;

        error = request_module("block-major-%d-%d", MAJOR(devt), MINOR(devt));
        /* Make old-style 2.4 aliases work */
        if (error > 0)
                error = request_module("block-major-%d", MAJOR(devt));
        if (!error)
                blk_probe_dev(devt);
}
#endif /* CONFIG_BLOCK_LEGACY_AUTOLOAD */

#ifdef CONFIG_PROC_FS
/* iterator */
static void *disk_seqf_start(struct seq_file *seqf, loff_t *pos)
{
        loff_t skip = *pos;
        struct class_dev_iter *iter;
        struct device *dev;

        iter = kmalloc(sizeof(*iter), GFP_KERNEL);
        if (!iter)
                return ERR_PTR(-ENOMEM);

        seqf->private = iter;
        class_dev_iter_init(iter, &block_class, NULL, &disk_type);
        do {
                dev = class_dev_iter_next(iter);
                if (!dev)
                        return NULL;
        } while (skip--);

        return dev_to_disk(dev);
}

static void *disk_seqf_next(struct seq_file *seqf, void *v, loff_t *pos)
{
        struct device *dev;

        (*pos)++;
        dev = class_dev_iter_next(seqf->private);
        if (dev)
                return dev_to_disk(dev);

        return NULL;
}

static void disk_seqf_stop(struct seq_file *seqf, void *v)
{
        struct class_dev_iter *iter = seqf->private;

        /* stop is called even after start failed :-( */
        if (iter) {
                class_dev_iter_exit(iter);
                kfree(iter);
                seqf->private = NULL;
        }
}

static void *show_partition_start(struct seq_file *seqf, loff_t *pos)
{
        void *p;

        p = disk_seqf_start(seqf, pos);
        if (!IS_ERR_OR_NULL(p) && !*pos)
                seq_puts(seqf, "major minor  #blocks  name\n\n");
        return p;
}

static int show_partition(struct seq_file *seqf, void *v)
{
        struct gendisk *sgp = v;
        struct block_device *part;
        unsigned long idx;

        if (!get_capacity(sgp) || (sgp->flags & GENHD_FL_HIDDEN))
                return 0;

        rcu_read_lock();
        xa_for_each(&sgp->part_tbl, idx, part) {
                if (!bdev_nr_sectors(part))
                        continue;
                seq_printf(seqf, "%4d  %7d %10llu %pg\n",
                           MAJOR(part->bd_dev), MINOR(part->bd_dev),
                           bdev_nr_sectors(part) >> 1, part);
        }
        rcu_read_unlock();
        return 0;
}

static const struct seq_operations partitions_op = {
        .start  = show_partition_start,
        .next   = disk_seqf_next,
        .stop   = disk_seqf_stop,
        .show   = show_partition
};
#endif

static int __init genhd_device_init(void)
{
        int error;

        error = class_register(&block_class);
        if (unlikely(error))
                return error;
        blk_dev_init();

        register_blkdev(BLOCK_EXT_MAJOR, "blkext");

        /* create top-level block dir */
        block_depr = kobject_create_and_add("block", NULL);
        return 0;
}

subsys_initcall(genhd_device_init);

static ssize_t disk_range_show(struct device *dev,
                               struct device_attribute *attr, char *buf)
{
        struct gendisk *disk = dev_to_disk(dev);

        return sysfs_emit(buf, "%d\n", disk->minors);
}

static ssize_t disk_ext_range_show(struct device *dev,
                                   struct device_attribute *attr, char *buf)
{
        struct gendisk *disk = dev_to_disk(dev);

        return sysfs_emit(buf, "%d\n",
                (disk->flags & GENHD_FL_NO_PART) ? 1 : DISK_MAX_PARTS);
}

static ssize_t disk_removable_show(struct device *dev,
                                   struct device_attribute *attr, char *buf)
{
        struct gendisk *disk = dev_to_disk(dev);

        return sysfs_emit(buf, "%d\n",
                       (disk->flags & GENHD_FL_REMOVABLE ? 1 : 0));
}

static ssize_t disk_hidden_show(struct device *dev,
                                   struct device_attribute *attr, char *buf)
{
        struct gendisk *disk = dev_to_disk(dev);

        return sysfs_emit(buf, "%d\n",
                       (disk->flags & GENHD_FL_HIDDEN ? 1 : 0));
}

static ssize_t disk_ro_show(struct device *dev,
                                   struct device_attribute *attr, char *buf)
{
        struct gendisk *disk = dev_to_disk(dev);

        return sysfs_emit(buf, "%d\n", get_disk_ro(disk) ? 1 : 0);
}

ssize_t part_size_show(struct device *dev,
                       struct device_attribute *attr, char *buf)
{
        return sysfs_emit(buf, "%llu\n", bdev_nr_sectors(dev_to_bdev(dev)));
}

ssize_t part_stat_show(struct device *dev,
                       struct device_attribute *attr, char *buf)
{
        struct block_device *bdev = dev_to_bdev(dev);
        struct disk_stats stat;
        unsigned int inflight;

        inflight = bdev_count_inflight(bdev);
        if (inflight) {
                part_stat_lock();
                update_io_ticks(bdev, jiffies, true);
                part_stat_unlock();
        }
        part_stat_read_all(bdev, &stat);
        return sysfs_emit(buf,
                "%8lu %8lu %8llu %8u "
                "%8lu %8lu %8llu %8u "
                "%8u %8u %8u "
                "%8lu %8lu %8llu %8u "
                "%8lu %8u"
                "\n",
                stat.ios[STAT_READ],
                stat.merges[STAT_READ],
                (unsigned long long)stat.sectors[STAT_READ],
                (unsigned int)div_u64(stat.nsecs[STAT_READ], NSEC_PER_MSEC),
                stat.ios[STAT_WRITE],
                stat.merges[STAT_WRITE],
                (unsigned long long)stat.sectors[STAT_WRITE],
                (unsigned int)div_u64(stat.nsecs[STAT_WRITE], NSEC_PER_MSEC),
                inflight,
                jiffies_to_msecs(stat.io_ticks),
                (unsigned int)div_u64(stat.nsecs[STAT_READ] +
                                      stat.nsecs[STAT_WRITE] +
                                      stat.nsecs[STAT_DISCARD] +
                                      stat.nsecs[STAT_FLUSH],
                                                NSEC_PER_MSEC),
                stat.ios[STAT_DISCARD],
                stat.merges[STAT_DISCARD],
                (unsigned long long)stat.sectors[STAT_DISCARD],
                (unsigned int)div_u64(stat.nsecs[STAT_DISCARD], NSEC_PER_MSEC),
                stat.ios[STAT_FLUSH],
                (unsigned int)div_u64(stat.nsecs[STAT_FLUSH], NSEC_PER_MSEC));
}

/*
 * Show the number of IOs issued to driver.
 * For bio-based device, started from bdev_start_io_acct();
 * For rq-based device, started from blk_mq_start_request();
 */
ssize_t part_inflight_show(struct device *dev, struct device_attribute *attr,
                           char *buf)
{
        struct block_device *bdev = dev_to_bdev(dev);
        struct request_queue *q = bdev_get_queue(bdev);
        unsigned int inflight[2] = {0};

        bdev_count_inflight_rw(bdev, inflight, queue_is_mq(q));

        return sysfs_emit(buf, "%8u %8u\n", inflight[READ], inflight[WRITE]);
}

static ssize_t disk_capability_show(struct device *dev,
                                    struct device_attribute *attr, char *buf)
{
        dev_warn_once(dev, "the capability attribute has been deprecated.\n");
        return sysfs_emit(buf, "0\n");
}

static ssize_t disk_alignment_offset_show(struct device *dev,
                                          struct device_attribute *attr,
                                          char *buf)
{
        struct gendisk *disk = dev_to_disk(dev);

        return sysfs_emit(buf, "%d\n", bdev_alignment_offset(disk->part0));
}

static ssize_t disk_discard_alignment_show(struct device *dev,
                                           struct device_attribute *attr,
                                           char *buf)
{
        struct gendisk *disk = dev_to_disk(dev);

        return sysfs_emit(buf, "%d\n", bdev_alignment_offset(disk->part0));
}

static ssize_t diskseq_show(struct device *dev,
                            struct device_attribute *attr, char *buf)
{
        struct gendisk *disk = dev_to_disk(dev);

        return sysfs_emit(buf, "%llu\n", disk->diskseq);
}

static ssize_t partscan_show(struct device *dev,
                struct device_attribute *attr, char *buf)
{
        return sysfs_emit(buf, "%u\n", disk_has_partscan(dev_to_disk(dev)));
}

static DEVICE_ATTR(range, 0444, disk_range_show, NULL);
static DEVICE_ATTR(ext_range, 0444, disk_ext_range_show, NULL);
static DEVICE_ATTR(removable, 0444, disk_removable_show, NULL);
static DEVICE_ATTR(hidden, 0444, disk_hidden_show, NULL);
static DEVICE_ATTR(ro, 0444, disk_ro_show, NULL);
static DEVICE_ATTR(size, 0444, part_size_show, NULL);
static DEVICE_ATTR(alignment_offset, 0444, disk_alignment_offset_show, NULL);
static DEVICE_ATTR(discard_alignment, 0444, disk_discard_alignment_show, NULL);
static DEVICE_ATTR(capability, 0444, disk_capability_show, NULL);
static DEVICE_ATTR(stat, 0444, part_stat_show, NULL);
static DEVICE_ATTR(inflight, 0444, part_inflight_show, NULL);
static DEVICE_ATTR(badblocks, 0644, disk_badblocks_show, disk_badblocks_store);
static DEVICE_ATTR(diskseq, 0444, diskseq_show, NULL);
static DEVICE_ATTR(partscan, 0444, partscan_show, NULL);

#ifdef CONFIG_FAIL_MAKE_REQUEST
ssize_t part_fail_show(struct device *dev,
                       struct device_attribute *attr, char *buf)
{
        return sysfs_emit(buf, "%d\n",
                       bdev_test_flag(dev_to_bdev(dev), BD_MAKE_IT_FAIL));
}

ssize_t part_fail_store(struct device *dev,
                        struct device_attribute *attr,
                        const char *buf, size_t count)
{
        int i;

        if (count > 0 && sscanf(buf, "%d", &i) > 0) {
                if (i)
                        bdev_set_flag(dev_to_bdev(dev), BD_MAKE_IT_FAIL);
                else
                        bdev_clear_flag(dev_to_bdev(dev), BD_MAKE_IT_FAIL);
        }
        return count;
}

static struct device_attribute dev_attr_fail =
        __ATTR(make-it-fail, 0644, part_fail_show, part_fail_store);
#endif /* CONFIG_FAIL_MAKE_REQUEST */

#ifdef CONFIG_FAIL_IO_TIMEOUT
static struct device_attribute dev_attr_fail_timeout =
        __ATTR(io-timeout-fail, 0644, part_timeout_show, part_timeout_store);
#endif

static struct attribute *disk_attrs[] = {
        &dev_attr_range.attr,
        &dev_attr_ext_range.attr,
        &dev_attr_removable.attr,
        &dev_attr_hidden.attr,
        &dev_attr_ro.attr,
        &dev_attr_size.attr,
        &dev_attr_alignment_offset.attr,
        &dev_attr_discard_alignment.attr,
        &dev_attr_capability.attr,
        &dev_attr_stat.attr,
        &dev_attr_inflight.attr,
        &dev_attr_badblocks.attr,
        &dev_attr_events.attr,
        &dev_attr_events_async.attr,
        &dev_attr_events_poll_msecs.attr,
        &dev_attr_diskseq.attr,
        &dev_attr_partscan.attr,
#ifdef CONFIG_FAIL_MAKE_REQUEST
        &dev_attr_fail.attr,
#endif
#ifdef CONFIG_FAIL_IO_TIMEOUT
        &dev_attr_fail_timeout.attr,
#endif
        NULL
};

static umode_t disk_visible(struct kobject *kobj, struct attribute *a, int n)
{
        struct device *dev = container_of(kobj, typeof(*dev), kobj);
        struct gendisk *disk = dev_to_disk(dev);

        if (a == &dev_attr_badblocks.attr && !disk->bb)
                return 0;
        return a->mode;
}

static struct attribute_group disk_attr_group = {
        .attrs = disk_attrs,
        .is_visible = disk_visible,
};

static const struct attribute_group *disk_attr_groups[] = {
        &disk_attr_group,
#ifdef CONFIG_BLK_DEV_IO_TRACE
        &blk_trace_attr_group,
#endif
#ifdef CONFIG_BLK_DEV_INTEGRITY
        &blk_integrity_attr_group,
#endif
        NULL
};

/**
 * disk_release - releases all allocated resources of the gendisk
 * @dev: the device representing this disk
 *
 * This function releases all allocated resources of the gendisk.
 *
 * Drivers which used __device_add_disk() have a gendisk with a request_queue
 * assigned. Since the request_queue sits on top of the gendisk for these
 * drivers we also call blk_put_queue() for them, and we expect the
 * request_queue refcount to reach 0 at this point, and so the request_queue
 * will also be freed prior to the disk.
 *
 * Context: can sleep
 */
static void disk_release(struct device *dev)
{
        struct gendisk *disk = dev_to_disk(dev);

        might_sleep();
        WARN_ON_ONCE(disk_live(disk));

        blk_trace_remove(disk->queue);

        /*
         * To undo the all initialization from blk_mq_init_allocated_queue in
         * case of a probe failure where add_disk is never called we have to
         * call blk_mq_exit_queue here. We can't do this for the more common
         * teardown case (yet) as the tagset can be gone by the time the disk
         * is released once it was added.
         */
        if (queue_is_mq(disk->queue) &&
            test_bit(GD_OWNS_QUEUE, &disk->state) &&
            !test_bit(GD_ADDED, &disk->state))
                blk_mq_exit_queue(disk->queue);

        blkcg_exit_disk(disk);

        bioset_exit(&disk->bio_split);

        disk_release_events(disk);
        kfree(disk->random);
        disk_free_zone_resources(disk);
        xa_destroy(&disk->part_tbl);

        disk->queue->disk = NULL;
        blk_put_queue(disk->queue);

        if (test_bit(GD_ADDED, &disk->state) && disk->fops->free_disk)
                disk->fops->free_disk(disk);

        bdev_drop(disk->part0); /* frees the disk */
}

static int block_uevent(const struct device *dev, struct kobj_uevent_env *env)
{
        const struct gendisk *disk = dev_to_disk(dev);

        return add_uevent_var(env, "DISKSEQ=%llu", disk->diskseq);
}

const struct class block_class = {
        .name           = "block",
        .dev_uevent     = block_uevent,
};

static char *block_devnode(const struct device *dev, umode_t *mode,
                           kuid_t *uid, kgid_t *gid)
{
        struct gendisk *disk = dev_to_disk(dev);

        if (disk->fops->devnode)
                return disk->fops->devnode(disk, mode);
        return NULL;
}

const struct device_type disk_type = {
        .name           = "disk",
        .groups         = disk_attr_groups,
        .release        = disk_release,
        .devnode        = block_devnode,
};

#ifdef CONFIG_PROC_FS
/*
 * aggregate disk stat collector.  Uses the same stats that the sysfs
 * entries do, above, but makes them available through one seq_file.
 *
 * The output looks suspiciously like /proc/partitions with a bunch of
 * extra fields.
 */
static int diskstats_show(struct seq_file *seqf, void *v)
{
        struct gendisk *gp = v;
        struct block_device *hd;
        unsigned int inflight;
        struct disk_stats stat;
        unsigned long idx;

        /*
        if (&disk_to_dev(gp)->kobj.entry == block_class.devices.next)
                seq_puts(seqf,  "major minor name"
                                "     rio rmerge rsect ruse wio wmerge "
                                "wsect wuse running use aveq"
                                "\n\n");
        */

        rcu_read_lock();
        xa_for_each(&gp->part_tbl, idx, hd) {
                if (bdev_is_partition(hd) && !bdev_nr_sectors(hd))
                        continue;

                inflight = bdev_count_inflight(hd);
                if (inflight) {
                        part_stat_lock();
                        update_io_ticks(hd, jiffies, true);
                        part_stat_unlock();
                }
                part_stat_read_all(hd, &stat);
                seq_put_decimal_ull_width(seqf, "",  MAJOR(hd->bd_dev), 4);
                seq_put_decimal_ull_width(seqf, " ", MINOR(hd->bd_dev), 7);
                seq_printf(seqf, " %pg", hd);
                seq_put_decimal_ull(seqf, " ", stat.ios[STAT_READ]);
                seq_put_decimal_ull(seqf, " ", stat.merges[STAT_READ]);
                seq_put_decimal_ull(seqf, " ", stat.sectors[STAT_READ]);
                seq_put_decimal_ull(seqf, " ", (unsigned int)div_u64(stat.nsecs[STAT_READ],
                                                                     NSEC_PER_MSEC));
                seq_put_decimal_ull(seqf, " ", stat.ios[STAT_WRITE]);
                seq_put_decimal_ull(seqf, " ", stat.merges[STAT_WRITE]);
                seq_put_decimal_ull(seqf, " ", stat.sectors[STAT_WRITE]);
                seq_put_decimal_ull(seqf, " ", (unsigned int)div_u64(stat.nsecs[STAT_WRITE],
                                                                     NSEC_PER_MSEC));
                seq_put_decimal_ull(seqf, " ", inflight);
                seq_put_decimal_ull(seqf, " ", jiffies_to_msecs(stat.io_ticks));
                seq_put_decimal_ull(seqf, " ", (unsigned int)div_u64(stat.nsecs[STAT_READ] +
                                                                     stat.nsecs[STAT_WRITE] +
                                                                     stat.nsecs[STAT_DISCARD] +
                                                                     stat.nsecs[STAT_FLUSH],
                                                                     NSEC_PER_MSEC));
                seq_put_decimal_ull(seqf, " ", stat.ios[STAT_DISCARD]);
                seq_put_decimal_ull(seqf, " ", stat.merges[STAT_DISCARD]);
                seq_put_decimal_ull(seqf, " ", stat.sectors[STAT_DISCARD]);
                seq_put_decimal_ull(seqf, " ", (unsigned int)div_u64(stat.nsecs[STAT_DISCARD],
                                                                     NSEC_PER_MSEC));
                seq_put_decimal_ull(seqf, " ", stat.ios[STAT_FLUSH]);
                seq_put_decimal_ull(seqf, " ", (unsigned int)div_u64(stat.nsecs[STAT_FLUSH],
                                                                     NSEC_PER_MSEC));
                seq_putc(seqf, '\n');
        }
        rcu_read_unlock();

        return 0;
}

static const struct seq_operations diskstats_op = {
        .start  = disk_seqf_start,
        .next   = disk_seqf_next,
        .stop   = disk_seqf_stop,
        .show   = diskstats_show
};

static int __init proc_genhd_init(void)
{
        proc_create_seq("diskstats", 0, NULL, &diskstats_op);
        proc_create_seq("partitions", 0, NULL, &partitions_op);
        return 0;
}
module_init(proc_genhd_init);
#endif /* CONFIG_PROC_FS */

dev_t part_devt(struct gendisk *disk, u8 partno)
{
        struct block_device *part;
        dev_t devt = 0;

        rcu_read_lock();
        part = xa_load(&disk->part_tbl, partno);
        if (part)
                devt = part->bd_dev;
        rcu_read_unlock();

        return devt;
}

struct gendisk *__alloc_disk_node(struct request_queue *q, int node_id,
                struct lock_class_key *lkclass)
{
        struct gendisk *disk;

        disk = kzalloc_node(sizeof(struct gendisk), GFP_KERNEL, node_id);
        if (!disk)
                return NULL;

        if (bioset_init(&disk->bio_split, BIO_POOL_SIZE, 0, 0))
                goto out_free_disk;

        disk->bdi = bdi_alloc(node_id);
        if (!disk->bdi)
                goto out_free_bioset;

        /* bdev_alloc() might need the queue, set before the first call */
        disk->queue = q;

        disk->part0 = bdev_alloc(disk, 0);
        if (!disk->part0)
                goto out_free_bdi;

        disk->node_id = node_id;
        mutex_init(&disk->open_mutex);
        xa_init(&disk->part_tbl);
        if (xa_insert(&disk->part_tbl, 0, disk->part0, GFP_KERNEL))
                goto out_destroy_part_tbl;

        if (blkcg_init_disk(disk))
                goto out_erase_part0;

        disk_init_zone_resources(disk);
        rand_initialize_disk(disk);
        disk_to_dev(disk)->class = &block_class;
        disk_to_dev(disk)->type = &disk_type;
        device_initialize(disk_to_dev(disk));
        inc_diskseq(disk);
        q->disk = disk;
        lockdep_init_map(&disk->lockdep_map, "(bio completion)", lkclass, 0);
#ifdef CONFIG_BLOCK_HOLDER_DEPRECATED
        INIT_LIST_HEAD(&disk->slave_bdevs);
#endif
        mutex_init(&disk->rqos_state_mutex);
        return disk;

out_erase_part0:
        xa_erase(&disk->part_tbl, 0);
out_destroy_part_tbl:
        xa_destroy(&disk->part_tbl);
        disk->part0->bd_disk = NULL;
        bdev_drop(disk->part0);
out_free_bdi:
        bdi_put(disk->bdi);
out_free_bioset:
        bioset_exit(&disk->bio_split);
out_free_disk:
        kfree(disk);
        return NULL;
}

struct gendisk *__blk_alloc_disk(struct queue_limits *lim, int node,
                struct lock_class_key *lkclass)
{
        struct queue_limits default_lim = { };
        struct request_queue *q;
        struct gendisk *disk;

        q = blk_alloc_queue(lim ? lim : &default_lim, node);
        if (IS_ERR(q))
                return ERR_CAST(q);

        disk = __alloc_disk_node(q, node, lkclass);
        if (!disk) {
                blk_put_queue(q);
                return ERR_PTR(-ENOMEM);
        }
        set_bit(GD_OWNS_QUEUE, &disk->state);
        return disk;
}
EXPORT_SYMBOL(__blk_alloc_disk);

/**
 * put_disk - decrements the gendisk refcount
 * @disk: the struct gendisk to decrement the refcount for
 *
 * This decrements the refcount for the struct gendisk. When this reaches 0
 * we'll have disk_release() called.
 *
 * Note: for blk-mq disk put_disk must be called before freeing the tag_set
 * when handling probe errors (that is before add_disk() is called).
 *
 * Context: Any context, but the last reference must not be dropped from
 *          atomic context.
 */
void put_disk(struct gendisk *disk)
{
        if (disk)
                put_device(disk_to_dev(disk));
}
EXPORT_SYMBOL(put_disk);

static void set_disk_ro_uevent(struct gendisk *gd, int ro)
{
        char event[] = "DISK_RO=1";
        char *envp[] = { event, NULL };

        if (!ro)
                event[8] = '0';
        kobject_uevent_env(&disk_to_dev(gd)->kobj, KOBJ_CHANGE, envp);
}

/**
 * set_disk_ro - set a gendisk read-only
 * @disk:       gendisk to operate on
 * @read_only:  %true to set the disk read-only, %false set the disk read/write
 *
 * This function is used to indicate whether a given disk device should have its
 * read-only flag set. set_disk_ro() is typically used by device drivers to
 * indicate whether the underlying physical device is write-protected.
 */
void set_disk_ro(struct gendisk *disk, bool read_only)
{
        if (read_only) {
                if (test_and_set_bit(GD_READ_ONLY, &disk->state))
                        return;
        } else {
                if (!test_and_clear_bit(GD_READ_ONLY, &disk->state))
                        return;
        }
        set_disk_ro_uevent(disk, read_only);
}
EXPORT_SYMBOL(set_disk_ro);

void inc_diskseq(struct gendisk *disk)
{
        disk->diskseq = atomic64_inc_return(&diskseq);
}