Merge tag 'drm-msm-fixes-2021-05-09' of https://gitlab.freedesktop.org/drm/msm into...

[mirror_ubuntu-jammy-kernel.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/genhd.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/mutex.h>
#include <linux/idr.h>
#include <linux/log2.h>
#include <linux/pm_runtime.h>
#include <linux/badblocks.h>

#include "blk.h"

static struct kobject *block_depr;

DECLARE_RWSEM(bdev_lookup_sem);

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

static void disk_check_events(struct disk_events *ev,
                              unsigned int *clearing_ptr);
static void disk_alloc_events(struct gendisk *disk);
static void disk_add_events(struct gendisk *disk);
static void disk_del_events(struct gendisk *disk);
static void disk_release_events(struct gendisk *disk);

void set_capacity(struct gendisk *disk, sector_t sectors)
{
        struct block_device *bdev = disk->part0;

        spin_lock(&bdev->bd_size_lock);
        i_size_write(bdev->bd_inode, (loff_t)sectors << SECTOR_SHIFT);
        spin_unlock(&bdev->bd_size_lock);
}
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->flags & (GENHD_FL_UP | GENHD_FL_HIDDEN)) != GENHD_FL_UP)
                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);

/*
 * Format the device name of the indicated disk into the supplied buffer and
 * return a pointer to that same buffer for convenience.
 */
char *disk_name(struct gendisk *hd, int partno, char *buf)
{
        if (!partno)
                snprintf(buf, BDEVNAME_SIZE, "%s", hd->disk_name);
        else if (isdigit(hd->disk_name[strlen(hd->disk_name)-1]))
                snprintf(buf, BDEVNAME_SIZE, "%sp%d", hd->disk_name, partno);
        else
                snprintf(buf, BDEVNAME_SIZE, "%s%d", hd->disk_name, partno);

        return buf;
}

const char *bdevname(struct block_device *bdev, char *buf)
{
        return disk_name(bdev->bd_disk, bdev->bd_partno, buf);
}
EXPORT_SYMBOL(bdevname);

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 unsigned int part_in_flight(struct block_device *part)
{
        unsigned int inflight = 0;
        int cpu;

        for_each_possible_cpu(cpu) {
                inflight += part_stat_local_read_cpu(part, in_flight[0], cpu) +
                            part_stat_local_read_cpu(part, in_flight[1], cpu);
        }
        if ((int)inflight < 0)
                inflight = 0;

        return inflight;
}

static void part_in_flight_rw(struct block_device *part,
                unsigned int inflight[2])
{
        int cpu;

        inflight[0] = 0;
        inflight[1] = 0;
        for_each_possible_cpu(cpu) {
                inflight[0] += part_stat_local_read_cpu(part, in_flight[0], cpu);
                inflight[1] += part_stat_local_read_cpu(part, in_flight[1], cpu);
        }
        if ((int)inflight[0] < 0)
                inflight[0] = 0;
        if ((int)inflight[1] < 0)
                inflight[1] = 0;
}

/*
 * 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];
        void (*probe)(dev_t devt);
} *major_names[BLKDEV_MAJOR_HASH_SIZE];
static DEFINE_MUTEX(major_names_lock);

/* 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;

        mutex_lock(&major_names_lock);
        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);
        mutex_unlock(&major_names_lock);
}
#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: allback that is called on access to any minor number of @major
 *
 * 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;
        p->probe = probe;
        strlcpy(p->name, name, sizeof(p->name));
        p->next = NULL;
        index = major_to_index(major);

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

        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);
        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;
        }
        mutex_unlock(&major_names_lock);
        kfree(p);
}

EXPORT_SYMBOL(unregister_blkdev);

/**
 * blk_mangle_minor - scatter minor numbers apart
 * @minor: minor number to mangle
 *
 * Scatter consecutively allocated @minor number apart if MANGLE_DEVT
 * is enabled.  Mangling twice gives the original value.
 *
 * RETURNS:
 * Mangled value.
 *
 * CONTEXT:
 * Don't care.
 */
static int blk_mangle_minor(int minor)
{
#ifdef CONFIG_DEBUG_BLOCK_EXT_DEVT
        int i;

        for (i = 0; i < MINORBITS / 2; i++) {
                int low = minor & (1 << i);
                int high = minor & (1 << (MINORBITS - 1 - i));
                int distance = MINORBITS - 1 - 2 * i;

                minor ^= low | high;    /* clear both bits */
                low <<= distance;       /* swap the positions */
                high >>= distance;
                minor |= low | high;    /* and set */
        }
#endif
        return minor;
}

/**
 * blk_alloc_devt - allocate a dev_t for a block device
 * @bdev: block device to allocate dev_t for
 * @devt: out parameter for resulting dev_t
 *
 * Allocate a dev_t for block device.
 *
 * RETURNS:
 * 0 on success, allocated dev_t is returned in *@devt.  -errno on
 * failure.
 *
 * CONTEXT:
 * Might sleep.
 */
int blk_alloc_devt(struct block_device *bdev, dev_t *devt)
{
        struct gendisk *disk = bdev->bd_disk;
        int idx;

        /* in consecutive minor range? */
        if (bdev->bd_partno < disk->minors) {
                *devt = MKDEV(disk->major, disk->first_minor + bdev->bd_partno);
                return 0;
        }

        idx = ida_alloc_range(&ext_devt_ida, 0, NR_EXT_DEVT, GFP_KERNEL);
        if (idx < 0)
                return idx == -ENOSPC ? -EBUSY : idx;

        *devt = MKDEV(BLOCK_EXT_MAJOR, blk_mangle_minor(idx));
        return 0;
}

/**
 * blk_free_devt - free a dev_t
 * @devt: dev_t to free
 *
 * Free @devt which was allocated using blk_alloc_devt().
 *
 * CONTEXT:
 * Might sleep.
 */
void blk_free_devt(dev_t devt)
{
        if (MAJOR(devt) == BLOCK_EXT_MAJOR)
                ida_free(&ext_devt_ida, blk_mangle_minor(MINOR(devt)));
}

static char *bdevt_str(dev_t devt, char *buf)
{
        if (MAJOR(devt) <= 0xff && MINOR(devt) <= 0xff) {
                char tbuf[BDEVT_SIZE];
                snprintf(tbuf, BDEVT_SIZE, "%02x%02x", MAJOR(devt), MINOR(devt));
                snprintf(buf, BDEVT_SIZE, "%-9s", tbuf);
        } else
                snprintf(buf, BDEVT_SIZE, "%03x:%05x", MAJOR(devt), MINOR(devt));

        return buf;
}

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 (!bdgrab(part))
                        continue;

                rcu_read_unlock();
                kobject_uevent(bdev_kobj(part), action);
                bdput(part);
                rcu_read_lock();
        }
        rcu_read_unlock();
}
EXPORT_SYMBOL_GPL(disk_uevent);

static void disk_scan_partitions(struct gendisk *disk)
{
        struct block_device *bdev;

        if (!get_capacity(disk) || !disk_part_scan_enabled(disk))
                return;

        set_bit(GD_NEED_PART_SCAN, &disk->state);
        bdev = blkdev_get_by_dev(disk_devt(disk), FMODE_READ, NULL);
        if (!IS_ERR(bdev))
                blkdev_put(bdev, FMODE_READ);
}

static void register_disk(struct device *parent, struct gendisk *disk,
                          const struct attribute_group **groups)
{
        struct device *ddev = disk_to_dev(disk);
        int err;

        ddev->parent = parent;

        dev_set_name(ddev, "%s", disk->disk_name);

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

        if (groups) {
                WARN_ON(ddev->groups);
                ddev->groups = groups;
        }
        if (device_add(ddev))
                return;
        if (!sysfs_deprecated) {
                err = sysfs_create_link(block_depr, &ddev->kobj,
                                        kobject_name(&ddev->kobj));
                if (err) {
                        device_del(ddev);
                        return;
                }
        }

        /*
         * 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);
        disk->slave_dir = kobject_create_and_add("slaves", &ddev->kobj);

        if (disk->flags & GENHD_FL_HIDDEN)
                return;

        disk_scan_partitions(disk);

        /* announce the disk and partitions after all partitions are created */
        dev_set_uevent_suppress(ddev, 0);
        disk_uevent(disk, KOBJ_ADD);

        if (disk->queue->backing_dev_info->dev) {
                err = sysfs_create_link(&ddev->kobj,
                          &disk->queue->backing_dev_info->dev->kobj,
                          "bdi");
                WARN_ON(err);
        }
}

/**
 * __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
 * @register_queue: register the queue if set to true
 *
 * This function registers the partitioning information in @disk
 * with the kernel.
 *
 * FIXME: error handling
 */
static void __device_add_disk(struct device *parent, struct gendisk *disk,
                              const struct attribute_group **groups,
                              bool register_queue)
{
        dev_t devt;
        int retval;

        /*
         * The disk queue should now be all set with enough information about
         * the device for the elevator code to pick an adequate default
         * elevator if one is needed, that is, for devices requesting queue
         * registration.
         */
        if (register_queue)
                elevator_init_mq(disk->queue);

        /* minors == 0 indicates to use ext devt from part0 and should
         * be accompanied with EXT_DEVT flag.  Make sure all
         * parameters make sense.
         */
        WARN_ON(disk->minors && !(disk->major || disk->first_minor));
        WARN_ON(!disk->minors &&
                !(disk->flags & (GENHD_FL_EXT_DEVT | GENHD_FL_HIDDEN)));

        disk->flags |= GENHD_FL_UP;

        retval = blk_alloc_devt(disk->part0, &devt);
        if (retval) {
                WARN_ON(1);
                return;
        }
        disk->major = MAJOR(devt);
        disk->first_minor = MINOR(devt);

        disk_alloc_events(disk);

        if (disk->flags & GENHD_FL_HIDDEN) {
                /*
                 * Don't let hidden disks show up in /proc/partitions,
                 * and don't bother scanning for partitions either.
                 */
                disk->flags |= GENHD_FL_SUPPRESS_PARTITION_INFO;
                disk->flags |= GENHD_FL_NO_PART_SCAN;
        } else {
                struct backing_dev_info *bdi = disk->queue->backing_dev_info;
                struct device *dev = disk_to_dev(disk);
                int ret;

                /* Register BDI before referencing it from bdev */
                dev->devt = devt;
                ret = bdi_register(bdi, "%u:%u", MAJOR(devt), MINOR(devt));
                WARN_ON(ret);
                bdi_set_owner(bdi, dev);
                bdev_add(disk->part0, devt);
        }
        register_disk(parent, disk, groups);
        if (register_queue)
                blk_register_queue(disk);

        /*
         * Take an extra ref on queue which will be put on disk_release()
         * so that it sticks around as long as @disk is there.
         */
        WARN_ON_ONCE(!blk_get_queue(disk->queue));

        disk_add_events(disk);
        blk_integrity_add(disk);
}

void device_add_disk(struct device *parent, struct gendisk *disk,
                     const struct attribute_group **groups)

{
        __device_add_disk(parent, disk, groups, true);
}
EXPORT_SYMBOL(device_add_disk);

void device_add_disk_no_queue_reg(struct device *parent, struct gendisk *disk)
{
        __device_add_disk(parent, disk, NULL, false);
}
EXPORT_SYMBOL(device_add_disk_no_queue_reg);

/**
 * 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)
{
        might_sleep();

        if (WARN_ON_ONCE(!disk->queue))
                return;

        blk_integrity_del(disk);
        disk_del_events(disk);

        /*
         * Block lookups of the disk until all bdevs are unhashed and the
         * disk is marked as dead (GENHD_FL_UP cleared).
         */
        down_write(&bdev_lookup_sem);

        mutex_lock(&disk->part0->bd_mutex);
        blk_drop_partitions(disk);
        mutex_unlock(&disk->part0->bd_mutex);

        fsync_bdev(disk->part0);
        __invalidate_device(disk->part0, true);

        /*
         * Unhash the bdev inode for this device so that it can't be looked
         * up any more even if openers still hold references to it.
         */
        remove_inode_hash(disk->part0->bd_inode);

        set_capacity(disk, 0);
        disk->flags &= ~GENHD_FL_UP;
        up_write(&bdev_lookup_sem);

        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->queue->backing_dev_info);
        }

        blk_unregister_queue(disk);

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

        part_stat_set_all(disk->part0, 0);
        disk->part0->bd_stamp = 0;
        if (!sysfs_deprecated)
                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));
}
EXPORT_SYMBOL(del_gendisk);

/* 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 sprintf(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);
}

void blk_request_module(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;
                }
        }
        mutex_unlock(&major_names_lock);

        if (request_module("block-major-%d-%d", MAJOR(devt), MINOR(devt)) > 0)
                /* Make old-style 2.4 aliases work */
                request_module("block-major-%d", MAJOR(devt));
}

/**
 * bdget_disk - do bdget() by gendisk and partition number
 * @disk: gendisk of interest
 * @partno: partition number
 *
 * Find partition @partno from @disk, do bdget() on it.
 *
 * CONTEXT:
 * Don't care.
 *
 * RETURNS:
 * Resulting block_device on success, NULL on failure.
 */
struct block_device *bdget_disk(struct gendisk *disk, int partno)
{
        struct block_device *bdev = NULL;

        rcu_read_lock();
        bdev = xa_load(&disk->part_tbl, partno);
        if (bdev && !bdgrab(bdev))
                bdev = NULL;
        rcu_read_unlock();

        return bdev;
}

/*
 * print a full list of all partitions - intended for places where the root
 * filesystem can't be mounted and thus to give the victim some idea of what
 * went wrong
 */
void __init printk_all_partitions(void)
{
        struct class_dev_iter iter;
        struct device *dev;

        class_dev_iter_init(&iter, &block_class, NULL, &disk_type);
        while ((dev = class_dev_iter_next(&iter))) {
                struct gendisk *disk = dev_to_disk(dev);
                struct block_device *part;
                char name_buf[BDEVNAME_SIZE];
                char devt_buf[BDEVT_SIZE];
                unsigned long idx;

                /*
                 * Don't show empty devices or things that have been
                 * suppressed
                 */
                if (get_capacity(disk) == 0 ||
                    (disk->flags & GENHD_FL_SUPPRESS_PARTITION_INFO))
                        continue;

                /*
                 * Note, unlike /proc/partitions, I am showing the numbers in
                 * hex - the same format as the root= option takes.
                 */
                rcu_read_lock();
                xa_for_each(&disk->part_tbl, idx, part) {
                        if (!bdev_nr_sectors(part))
                                continue;
                        printk("%s%s %10llu %s %s",
                               bdev_is_partition(part) ? "  " : "",
                               bdevt_str(part->bd_dev, devt_buf),
                               bdev_nr_sectors(part) >> 1,
                               disk_name(disk, part->bd_partno, name_buf),
                               part->bd_meta_info ?
                                        part->bd_meta_info->uuid : "");
                        if (bdev_is_partition(part))
                                printk("\n");
                        else if (dev->parent && dev->parent->driver)
                                printk(" driver: %s\n",
                                        dev->parent->driver->name);
                        else
                                printk(" (driver?)\n");
                }
                rcu_read_unlock();
        }
        class_dev_iter_exit(&iter);
}

#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;
        char buf[BDEVNAME_SIZE];

        /* Don't show non-partitionable removeable devices or empty devices */
        if (!get_capacity(sgp) || (!disk_max_parts(sgp) &&
                                   (sgp->flags & GENHD_FL_REMOVABLE)))
                return 0;
        if (sgp->flags & GENHD_FL_SUPPRESS_PARTITION_INFO)
                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 %s\n",
                           MAJOR(part->bd_dev), MINOR(part->bd_dev),
                           bdev_nr_sectors(part) >> 1,
                           disk_name(sgp, part->bd_partno, buf));
        }
        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;

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

        register_blkdev(BLOCK_EXT_MAJOR, "blkext");

        /* create top-level block dir */
        if (!sysfs_deprecated)
                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 sprintf(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 sprintf(buf, "%d\n", disk_max_parts(disk));
}

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

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

ssize_t part_size_show(struct device *dev,
                       struct device_attribute *attr, char *buf)
{
        return sprintf(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 request_queue *q = bdev->bd_disk->queue;
        struct disk_stats stat;
        unsigned int inflight;

        part_stat_read_all(bdev, &stat);
        if (queue_is_mq(q))
                inflight = blk_mq_in_flight(q, bdev);
        else
                inflight = part_in_flight(bdev);

        return sprintf(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));
}

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->bd_disk->queue;
        unsigned int inflight[2];

        if (queue_is_mq(q))
                blk_mq_in_flight_rw(q, bdev, inflight);
        else
                part_in_flight_rw(bdev, inflight);

        return sprintf(buf, "%8u %8u\n", inflight[0], inflight[1]);
}

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

        return sprintf(buf, "%x\n", disk->flags);
}

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

        return sprintf(buf, "%d\n", queue_alignment_offset(disk->queue));
}

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

        return sprintf(buf, "%d\n", queue_discard_alignment(disk->queue));
}

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);

#ifdef CONFIG_FAIL_MAKE_REQUEST
ssize_t part_fail_show(struct device *dev,
                       struct device_attribute *attr, char *buf)
{
        return sprintf(buf, "%d\n", 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)
                dev_to_bdev(dev)->bd_make_it_fail = i;

        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,
#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,
        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();

        blk_free_devt(dev->devt);
        disk_release_events(disk);
        kfree(disk->random);
        xa_destroy(&disk->part_tbl);
        bdput(disk->part0);
        if (disk->queue)
                blk_put_queue(disk->queue);
        kfree(disk);
}
struct class block_class = {
        .name           = "block",
};

static char *block_devnode(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;
        char buf[BDEVNAME_SIZE];
        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;
                part_stat_read_all(hd, &stat);
                if (queue_is_mq(gp->queue))
                        inflight = blk_mq_in_flight(gp->queue, hd);
                else
                        inflight = part_in_flight(hd);

                seq_printf(seqf, "%4d %7d %s "
                           "%lu %lu %lu %u "
                           "%lu %lu %lu %u "
                           "%u %u %u "
                           "%lu %lu %lu %u "
                           "%lu %u"
                           "\n",
                           MAJOR(hd->bd_dev), MINOR(hd->bd_dev),
                           disk_name(gp, hd->bd_partno, buf),
                           stat.ios[STAT_READ],
                           stat.merges[STAT_READ],
                           stat.sectors[STAT_READ],
                           (unsigned int)div_u64(stat.nsecs[STAT_READ],
                                                        NSEC_PER_MSEC),
                           stat.ios[STAT_WRITE],
                           stat.merges[STAT_WRITE],
                           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],
                           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)
                        );
        }
        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 blk_lookup_devt(const char *name, int partno)
{
        dev_t devt = MKDEV(0, 0);
        struct class_dev_iter iter;
        struct device *dev;

        class_dev_iter_init(&iter, &block_class, NULL, &disk_type);
        while ((dev = class_dev_iter_next(&iter))) {
                struct gendisk *disk = dev_to_disk(dev);
                struct block_device *part;

                if (strcmp(dev_name(dev), name))
                        continue;

                if (partno < disk->minors) {
                        /* We need to return the right devno, even
                         * if the partition doesn't exist yet.
                         */
                        devt = MKDEV(MAJOR(dev->devt),
                                     MINOR(dev->devt) + partno);
                        break;
                }
                part = bdget_disk(disk, partno);
                if (part) {
                        devt = part->bd_dev;
                        bdput(part);
                        break;
                }
        }
        class_dev_iter_exit(&iter);
        return devt;
}

struct gendisk *__alloc_disk_node(int minors, int node_id)
{
        struct gendisk *disk;

        if (minors > DISK_MAX_PARTS) {
                printk(KERN_ERR
                        "block: can't allocate more than %d partitions\n",
                        DISK_MAX_PARTS);
                minors = DISK_MAX_PARTS;
        }

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

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

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

        disk->minors = minors;
        rand_initialize_disk(disk);
        disk_to_dev(disk)->class = &block_class;
        disk_to_dev(disk)->type = &disk_type;
        device_initialize(disk_to_dev(disk));
        return disk;

out_destroy_part_tbl:
        xa_destroy(&disk->part_tbl);
        bdput(disk->part0);
out_free_disk:
        kfree(disk);
        return NULL;
}
EXPORT_SYMBOL(__alloc_disk_node);

/**
 * 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.
 *
 * 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);

int bdev_read_only(struct block_device *bdev)
{
        return bdev->bd_read_only || get_disk_ro(bdev->bd_disk);
}
EXPORT_SYMBOL(bdev_read_only);

/*
 * Disk events - monitor disk events like media change and eject request.
 */
struct disk_events {
        struct list_head        node;           /* all disk_event's */
        struct gendisk          *disk;          /* the associated disk */
        spinlock_t              lock;

        struct mutex            block_mutex;    /* protects blocking */
        int                     block;          /* event blocking depth */
        unsigned int            pending;        /* events already sent out */
        unsigned int            clearing;       /* events being cleared */

        long                    poll_msecs;     /* interval, -1 for default */
        struct delayed_work     dwork;
};

static const char *disk_events_strs[] = {
        [ilog2(DISK_EVENT_MEDIA_CHANGE)]        = "media_change",
        [ilog2(DISK_EVENT_EJECT_REQUEST)]       = "eject_request",
};

static char *disk_uevents[] = {
        [ilog2(DISK_EVENT_MEDIA_CHANGE)]        = "DISK_MEDIA_CHANGE=1",
        [ilog2(DISK_EVENT_EJECT_REQUEST)]       = "DISK_EJECT_REQUEST=1",
};

/* list of all disk_events */
static DEFINE_MUTEX(disk_events_mutex);
static LIST_HEAD(disk_events);

/* disable in-kernel polling by default */
static unsigned long disk_events_dfl_poll_msecs;

static unsigned long disk_events_poll_jiffies(struct gendisk *disk)
{
        struct disk_events *ev = disk->ev;
        long intv_msecs = 0;

        /*
         * If device-specific poll interval is set, always use it.  If
         * the default is being used, poll if the POLL flag is set.
         */
        if (ev->poll_msecs >= 0)
                intv_msecs = ev->poll_msecs;
        else if (disk->event_flags & DISK_EVENT_FLAG_POLL)
                intv_msecs = disk_events_dfl_poll_msecs;

        return msecs_to_jiffies(intv_msecs);
}

/**
 * disk_block_events - block and flush disk event checking
 * @disk: disk to block events for
 *
 * On return from this function, it is guaranteed that event checking
 * isn't in progress and won't happen until unblocked by
 * disk_unblock_events().  Events blocking is counted and the actual
 * unblocking happens after the matching number of unblocks are done.
 *
 * Note that this intentionally does not block event checking from
 * disk_clear_events().
 *
 * CONTEXT:
 * Might sleep.
 */
void disk_block_events(struct gendisk *disk)
{
        struct disk_events *ev = disk->ev;
        unsigned long flags;
        bool cancel;

        if (!ev)
                return;

        /*
         * Outer mutex ensures that the first blocker completes canceling
         * the event work before further blockers are allowed to finish.
         */
        mutex_lock(&ev->block_mutex);

        spin_lock_irqsave(&ev->lock, flags);
        cancel = !ev->block++;
        spin_unlock_irqrestore(&ev->lock, flags);

        if (cancel)
                cancel_delayed_work_sync(&disk->ev->dwork);

        mutex_unlock(&ev->block_mutex);
}

static void __disk_unblock_events(struct gendisk *disk, bool check_now)
{
        struct disk_events *ev = disk->ev;
        unsigned long intv;
        unsigned long flags;

        spin_lock_irqsave(&ev->lock, flags);

        if (WARN_ON_ONCE(ev->block <= 0))
                goto out_unlock;

        if (--ev->block)
                goto out_unlock;

        intv = disk_events_poll_jiffies(disk);
        if (check_now)
                queue_delayed_work(system_freezable_power_efficient_wq,
                                &ev->dwork, 0);
        else if (intv)
                queue_delayed_work(system_freezable_power_efficient_wq,
                                &ev->dwork, intv);
out_unlock:
        spin_unlock_irqrestore(&ev->lock, flags);
}

/**
 * disk_unblock_events - unblock disk event checking
 * @disk: disk to unblock events for
 *
 * Undo disk_block_events().  When the block count reaches zero, it
 * starts events polling if configured.
 *
 * CONTEXT:
 * Don't care.  Safe to call from irq context.
 */
void disk_unblock_events(struct gendisk *disk)
{
        if (disk->ev)
                __disk_unblock_events(disk, false);
}

/**
 * disk_flush_events - schedule immediate event checking and flushing
 * @disk: disk to check and flush events for
 * @mask: events to flush
 *
 * Schedule immediate event checking on @disk if not blocked.  Events in
 * @mask are scheduled to be cleared from the driver.  Note that this
 * doesn't clear the events from @disk->ev.
 *
 * CONTEXT:
 * If @mask is non-zero must be called with bdev->bd_mutex held.
 */
void disk_flush_events(struct gendisk *disk, unsigned int mask)
{
        struct disk_events *ev = disk->ev;

        if (!ev)
                return;

        spin_lock_irq(&ev->lock);
        ev->clearing |= mask;
        if (!ev->block)
                mod_delayed_work(system_freezable_power_efficient_wq,
                                &ev->dwork, 0);
        spin_unlock_irq(&ev->lock);
}

/**
 * disk_clear_events - synchronously check, clear and return pending events
 * @disk: disk to fetch and clear events from
 * @mask: mask of events to be fetched and cleared
 *
 * Disk events are synchronously checked and pending events in @mask
 * are cleared and returned.  This ignores the block count.
 *
 * CONTEXT:
 * Might sleep.
 */
static unsigned int disk_clear_events(struct gendisk *disk, unsigned int mask)
{
        struct disk_events *ev = disk->ev;
        unsigned int pending;
        unsigned int clearing = mask;

        if (!ev)
                return 0;

        disk_block_events(disk);

        /*
         * store the union of mask and ev->clearing on the stack so that the
         * race with disk_flush_events does not cause ambiguity (ev->clearing
         * can still be modified even if events are blocked).
         */
        spin_lock_irq(&ev->lock);
        clearing |= ev->clearing;
        ev->clearing = 0;
        spin_unlock_irq(&ev->lock);

        disk_check_events(ev, &clearing);
        /*
         * if ev->clearing is not 0, the disk_flush_events got called in the
         * middle of this function, so we want to run the workfn without delay.
         */
        __disk_unblock_events(disk, ev->clearing ? true : false);

        /* then, fetch and clear pending events */
        spin_lock_irq(&ev->lock);
        pending = ev->pending & mask;
        ev->pending &= ~mask;
        spin_unlock_irq(&ev->lock);
        WARN_ON_ONCE(clearing & mask);

        return pending;
}

/**
 * bdev_check_media_change - check if a removable media has been changed
 * @bdev: block device to check
 *
 * Check whether a removable media has been changed, and attempt to free all
 * dentries and inodes and invalidates all block device page cache entries in
 * that case.
 *
 * Returns %true if the block device changed, or %false if not.
 */
bool bdev_check_media_change(struct block_device *bdev)
{
        unsigned int events;

        events = disk_clear_events(bdev->bd_disk, DISK_EVENT_MEDIA_CHANGE |
                                   DISK_EVENT_EJECT_REQUEST);
        if (!(events & DISK_EVENT_MEDIA_CHANGE))
                return false;

        if (__invalidate_device(bdev, true))
                pr_warn("VFS: busy inodes on changed media %s\n",
                        bdev->bd_disk->disk_name);
        set_bit(GD_NEED_PART_SCAN, &bdev->bd_disk->state);
        return true;
}
EXPORT_SYMBOL(bdev_check_media_change);

/*
 * Separate this part out so that a different pointer for clearing_ptr can be
 * passed in for disk_clear_events.
 */
static void disk_events_workfn(struct work_struct *work)
{
        struct delayed_work *dwork = to_delayed_work(work);
        struct disk_events *ev = container_of(dwork, struct disk_events, dwork);

        disk_check_events(ev, &ev->clearing);
}

static void disk_check_events(struct disk_events *ev,
                              unsigned int *clearing_ptr)
{
        struct gendisk *disk = ev->disk;
        char *envp[ARRAY_SIZE(disk_uevents) + 1] = { };
        unsigned int clearing = *clearing_ptr;
        unsigned int events;
        unsigned long intv;
        int nr_events = 0, i;

        /* check events */
        events = disk->fops->check_events(disk, clearing);

        /* accumulate pending events and schedule next poll if necessary */
        spin_lock_irq(&ev->lock);

        events &= ~ev->pending;
        ev->pending |= events;
        *clearing_ptr &= ~clearing;

        intv = disk_events_poll_jiffies(disk);
        if (!ev->block && intv)
                queue_delayed_work(system_freezable_power_efficient_wq,
                                &ev->dwork, intv);

        spin_unlock_irq(&ev->lock);

        /*
         * Tell userland about new events.  Only the events listed in
         * @disk->events are reported, and only if DISK_EVENT_FLAG_UEVENT
         * is set. Otherwise, events are processed internally but never
         * get reported to userland.
         */
        for (i = 0; i < ARRAY_SIZE(disk_uevents); i++)
                if ((events & disk->events & (1 << i)) &&
                    (disk->event_flags & DISK_EVENT_FLAG_UEVENT))
                        envp[nr_events++] = disk_uevents[i];

        if (nr_events)
                kobject_uevent_env(&disk_to_dev(disk)->kobj, KOBJ_CHANGE, envp);
}

/*
 * A disk events enabled device has the following sysfs nodes under
 * its /sys/block/X/ directory.
 *
 * events               : list of all supported events
 * events_async         : list of events which can be detected w/o polling
 *                        (always empty, only for backwards compatibility)
 * events_poll_msecs    : polling interval, 0: disable, -1: system default
 */
static ssize_t __disk_events_show(unsigned int events, char *buf)
{
        const char *delim = "";
        ssize_t pos = 0;
        int i;

        for (i = 0; i < ARRAY_SIZE(disk_events_strs); i++)
                if (events & (1 << i)) {
                        pos += sprintf(buf + pos, "%s%s",
                                       delim, disk_events_strs[i]);
                        delim = " ";
                }
        if (pos)
                pos += sprintf(buf + pos, "\n");
        return pos;
}

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

        if (!(disk->event_flags & DISK_EVENT_FLAG_UEVENT))
                return 0;

        return __disk_events_show(disk->events, buf);
}

static ssize_t disk_events_async_show(struct device *dev,
                                      struct device_attribute *attr, char *buf)
{
        return 0;
}

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

        if (!disk->ev)
                return sprintf(buf, "-1\n");

        return sprintf(buf, "%ld\n", disk->ev->poll_msecs);
}

static ssize_t disk_events_poll_msecs_store(struct device *dev,
                                            struct device_attribute *attr,
                                            const char *buf, size_t count)
{
        struct gendisk *disk = dev_to_disk(dev);
        long intv;

        if (!count || !sscanf(buf, "%ld", &intv))
                return -EINVAL;

        if (intv < 0 && intv != -1)
                return -EINVAL;

        if (!disk->ev)
                return -ENODEV;

        disk_block_events(disk);
        disk->ev->poll_msecs = intv;
        __disk_unblock_events(disk, true);

        return count;
}

static const DEVICE_ATTR(events, 0444, disk_events_show, NULL);
static const DEVICE_ATTR(events_async, 0444, disk_events_async_show, NULL);
static const DEVICE_ATTR(events_poll_msecs, 0644,
                         disk_events_poll_msecs_show,
                         disk_events_poll_msecs_store);

static const struct attribute *disk_events_attrs[] = {
        &dev_attr_events.attr,
        &dev_attr_events_async.attr,
        &dev_attr_events_poll_msecs.attr,
        NULL,
};

/*
 * The default polling interval can be specified by the kernel
 * parameter block.events_dfl_poll_msecs which defaults to 0
 * (disable).  This can also be modified runtime by writing to
 * /sys/module/block/parameters/events_dfl_poll_msecs.
 */
static int disk_events_set_dfl_poll_msecs(const char *val,
                                          const struct kernel_param *kp)
{
        struct disk_events *ev;
        int ret;

        ret = param_set_ulong(val, kp);
        if (ret < 0)
                return ret;

        mutex_lock(&disk_events_mutex);

        list_for_each_entry(ev, &disk_events, node)
                disk_flush_events(ev->disk, 0);

        mutex_unlock(&disk_events_mutex);

        return 0;
}

static const struct kernel_param_ops disk_events_dfl_poll_msecs_param_ops = {
        .set    = disk_events_set_dfl_poll_msecs,
        .get    = param_get_ulong,
};

#undef MODULE_PARAM_PREFIX
#define MODULE_PARAM_PREFIX     "block."

module_param_cb(events_dfl_poll_msecs, &disk_events_dfl_poll_msecs_param_ops,
                &disk_events_dfl_poll_msecs, 0644);

/*
 * disk_{alloc|add|del|release}_events - initialize and destroy disk_events.
 */
static void disk_alloc_events(struct gendisk *disk)
{
        struct disk_events *ev;

        if (!disk->fops->check_events || !disk->events)
                return;

        ev = kzalloc(sizeof(*ev), GFP_KERNEL);
        if (!ev) {
                pr_warn("%s: failed to initialize events\n", disk->disk_name);
                return;
        }

        INIT_LIST_HEAD(&ev->node);
        ev->disk = disk;
        spin_lock_init(&ev->lock);
        mutex_init(&ev->block_mutex);
        ev->block = 1;
        ev->poll_msecs = -1;
        INIT_DELAYED_WORK(&ev->dwork, disk_events_workfn);

        disk->ev = ev;
}

static void disk_add_events(struct gendisk *disk)
{
        /* FIXME: error handling */
        if (sysfs_create_files(&disk_to_dev(disk)->kobj, disk_events_attrs) < 0)
                pr_warn("%s: failed to create sysfs files for events\n",
                        disk->disk_name);

        if (!disk->ev)
                return;

        mutex_lock(&disk_events_mutex);
        list_add_tail(&disk->ev->node, &disk_events);
        mutex_unlock(&disk_events_mutex);

        /*
         * Block count is initialized to 1 and the following initial
         * unblock kicks it into action.
         */
        __disk_unblock_events(disk, true);
}

static void disk_del_events(struct gendisk *disk)
{
        if (disk->ev) {
                disk_block_events(disk);

                mutex_lock(&disk_events_mutex);
                list_del_init(&disk->ev->node);
                mutex_unlock(&disk_events_mutex);
        }

        sysfs_remove_files(&disk_to_dev(disk)->kobj, disk_events_attrs);
}

static void disk_release_events(struct gendisk *disk)
{
        /* the block count should be 1 from disk_del_events() */
        WARN_ON_ONCE(disk->ev && disk->ev->block != 1);
        kfree(disk->ev);
}