ACPI: processor: Move arch_init_invariance_cppc() call later

[pf-kernel.git] / block / blk-zoned.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Zoned block device handling
 *
 * Copyright (c) 2015, Hannes Reinecke
 * Copyright (c) 2015, SUSE Linux GmbH
 *
 * Copyright (c) 2016, Damien Le Moal
 * Copyright (c) 2016, Western Digital
 * Copyright (c) 2024, Western Digital Corporation or its affiliates.
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/blkdev.h>
#include <linux/blk-mq.h>
#include <linux/mm.h>
#include <linux/vmalloc.h>
#include <linux/sched/mm.h>
#include <linux/spinlock.h>
#include <linux/atomic.h>
#include <linux/mempool.h>

#include "blk.h"
#include "blk-mq-sched.h"
#include "blk-mq-debugfs.h"

#define ZONE_COND_NAME(name) [BLK_ZONE_COND_##name] = #name
static const char *const zone_cond_name[] = {
        ZONE_COND_NAME(NOT_WP),
        ZONE_COND_NAME(EMPTY),
        ZONE_COND_NAME(IMP_OPEN),
        ZONE_COND_NAME(EXP_OPEN),
        ZONE_COND_NAME(CLOSED),
        ZONE_COND_NAME(READONLY),
        ZONE_COND_NAME(FULL),
        ZONE_COND_NAME(OFFLINE),
};
#undef ZONE_COND_NAME

/*
 * Per-zone write plug.
 * @node: hlist_node structure for managing the plug using a hash table.
 * @link: To list the plug in the zone write plug error list of the disk.
 * @ref: Zone write plug reference counter. A zone write plug reference is
 *       always at least 1 when the plug is hashed in the disk plug hash table.
 *       The reference is incremented whenever a new BIO needing plugging is
 *       submitted and when a function needs to manipulate a plug. The
 *       reference count is decremented whenever a plugged BIO completes and
 *       when a function that referenced the plug returns. The initial
 *       reference is dropped whenever the zone of the zone write plug is reset,
 *       finished and when the zone becomes full (last write BIO to the zone
 *       completes).
 * @lock: Spinlock to atomically manipulate the plug.
 * @flags: Flags indicating the plug state.
 * @zone_no: The number of the zone the plug is managing.
 * @wp_offset: The zone write pointer location relative to the start of the zone
 *             as a number of 512B sectors.
 * @bio_list: The list of BIOs that are currently plugged.
 * @bio_work: Work struct to handle issuing of plugged BIOs
 * @rcu_head: RCU head to free zone write plugs with an RCU grace period.
 * @disk: The gendisk the plug belongs to.
 */
struct blk_zone_wplug {
        struct hlist_node       node;
        struct list_head        link;
        atomic_t                ref;
        spinlock_t              lock;
        unsigned int            flags;
        unsigned int            zone_no;
        unsigned int            wp_offset;
        struct bio_list         bio_list;
        struct work_struct      bio_work;
        struct rcu_head         rcu_head;
        struct gendisk          *disk;
};

/*
 * Zone write plug flags bits:
 *  - BLK_ZONE_WPLUG_PLUGGED: Indicates that the zone write plug is plugged,
 *    that is, that write BIOs are being throttled due to a write BIO already
 *    being executed or the zone write plug bio list is not empty.
 *  - BLK_ZONE_WPLUG_ERROR: Indicates that a write error happened which will be
 *    recovered with a report zone to update the zone write pointer offset.
 *  - BLK_ZONE_WPLUG_UNHASHED: Indicates that the zone write plug was removed
 *    from the disk hash table and that the initial reference to the zone
 *    write plug set when the plug was first added to the hash table has been
 *    dropped. This flag is set when a zone is reset, finished or become full,
 *    to prevent new references to the zone write plug to be taken for
 *    newly incoming BIOs. A zone write plug flagged with this flag will be
 *    freed once all remaining references from BIOs or functions are dropped.
 */
#define BLK_ZONE_WPLUG_PLUGGED          (1U << 0)
#define BLK_ZONE_WPLUG_ERROR            (1U << 1)
#define BLK_ZONE_WPLUG_UNHASHED         (1U << 2)

#define BLK_ZONE_WPLUG_BUSY     (BLK_ZONE_WPLUG_PLUGGED | BLK_ZONE_WPLUG_ERROR)

/**
 * blk_zone_cond_str - Return string XXX in BLK_ZONE_COND_XXX.
 * @zone_cond: BLK_ZONE_COND_XXX.
 *
 * Description: Centralize block layer function to convert BLK_ZONE_COND_XXX
 * into string format. Useful in the debugging and tracing zone conditions. For
 * invalid BLK_ZONE_COND_XXX it returns string "UNKNOWN".
 */
const char *blk_zone_cond_str(enum blk_zone_cond zone_cond)
{
        static const char *zone_cond_str = "UNKNOWN";

        if (zone_cond < ARRAY_SIZE(zone_cond_name) && zone_cond_name[zone_cond])
                zone_cond_str = zone_cond_name[zone_cond];

        return zone_cond_str;
}
EXPORT_SYMBOL_GPL(blk_zone_cond_str);

/**
 * blkdev_report_zones - Get zones information
 * @bdev:       Target block device
 * @sector:     Sector from which to report zones
 * @nr_zones:   Maximum number of zones to report
 * @cb:         Callback function called for each reported zone
 * @data:       Private data for the callback
 *
 * Description:
 *    Get zone information starting from the zone containing @sector for at most
 *    @nr_zones, and call @cb for each zone reported by the device.
 *    To report all zones in a device starting from @sector, the BLK_ALL_ZONES
 *    constant can be passed to @nr_zones.
 *    Returns the number of zones reported by the device, or a negative errno
 *    value in case of failure.
 *
 *    Note: The caller must use memalloc_noXX_save/restore() calls to control
 *    memory allocations done within this function.
 */
int blkdev_report_zones(struct block_device *bdev, sector_t sector,
                        unsigned int nr_zones, report_zones_cb cb, void *data)
{
        struct gendisk *disk = bdev->bd_disk;
        sector_t capacity = get_capacity(disk);

        if (!bdev_is_zoned(bdev) || WARN_ON_ONCE(!disk->fops->report_zones))
                return -EOPNOTSUPP;

        if (!nr_zones || sector >= capacity)
                return 0;

        return disk->fops->report_zones(disk, sector, nr_zones, cb, data);
}
EXPORT_SYMBOL_GPL(blkdev_report_zones);

static int blkdev_zone_reset_all(struct block_device *bdev)
{
        struct bio bio;

        bio_init(&bio, bdev, NULL, 0, REQ_OP_ZONE_RESET_ALL | REQ_SYNC);
        return submit_bio_wait(&bio);
}

/**
 * blkdev_zone_mgmt - Execute a zone management operation on a range of zones
 * @bdev:       Target block device
 * @op:         Operation to be performed on the zones
 * @sector:     Start sector of the first zone to operate on
 * @nr_sectors: Number of sectors, should be at least the length of one zone and
 *              must be zone size aligned.
 *
 * Description:
 *    Perform the specified operation on the range of zones specified by
 *    @sector..@sector+@nr_sectors. Specifying the entire disk sector range
 *    is valid, but the specified range should not contain conventional zones.
 *    The operation to execute on each zone can be a zone reset, open, close
 *    or finish request.
 */
int blkdev_zone_mgmt(struct block_device *bdev, enum req_op op,
                     sector_t sector, sector_t nr_sectors)
{
        sector_t zone_sectors = bdev_zone_sectors(bdev);
        sector_t capacity = bdev_nr_sectors(bdev);
        sector_t end_sector = sector + nr_sectors;
        struct bio *bio = NULL;
        int ret = 0;

        if (!bdev_is_zoned(bdev))
                return -EOPNOTSUPP;

        if (bdev_read_only(bdev))
                return -EPERM;

        if (!op_is_zone_mgmt(op))
                return -EOPNOTSUPP;

        if (end_sector <= sector || end_sector > capacity)
                /* Out of range */
                return -EINVAL;

        /* Check alignment (handle eventual smaller last zone) */
        if (!bdev_is_zone_start(bdev, sector))
                return -EINVAL;

        if (!bdev_is_zone_start(bdev, nr_sectors) && end_sector != capacity)
                return -EINVAL;

        /*
         * In the case of a zone reset operation over all zones, use
         * REQ_OP_ZONE_RESET_ALL.
         */
        if (op == REQ_OP_ZONE_RESET && sector == 0 && nr_sectors == capacity)
                return blkdev_zone_reset_all(bdev);

        while (sector < end_sector) {
                bio = blk_next_bio(bio, bdev, 0, op | REQ_SYNC, GFP_KERNEL);
                bio->bi_iter.bi_sector = sector;
                sector += zone_sectors;

                /* This may take a while, so be nice to others */
                cond_resched();
        }

        ret = submit_bio_wait(bio);
        bio_put(bio);

        return ret;
}
EXPORT_SYMBOL_GPL(blkdev_zone_mgmt);

struct zone_report_args {
        struct blk_zone __user *zones;
};

static int blkdev_copy_zone_to_user(struct blk_zone *zone, unsigned int idx,
                                    void *data)
{
        struct zone_report_args *args = data;

        if (copy_to_user(&args->zones[idx], zone, sizeof(struct blk_zone)))
                return -EFAULT;
        return 0;
}

/*
 * BLKREPORTZONE ioctl processing.
 * Called from blkdev_ioctl.
 */
int blkdev_report_zones_ioctl(struct block_device *bdev, unsigned int cmd,
                unsigned long arg)
{
        void __user *argp = (void __user *)arg;
        struct zone_report_args args;
        struct blk_zone_report rep;
        int ret;

        if (!argp)
                return -EINVAL;

        if (!bdev_is_zoned(bdev))
                return -ENOTTY;

        if (copy_from_user(&rep, argp, sizeof(struct blk_zone_report)))
                return -EFAULT;

        if (!rep.nr_zones)
                return -EINVAL;

        args.zones = argp + sizeof(struct blk_zone_report);
        ret = blkdev_report_zones(bdev, rep.sector, rep.nr_zones,
                                  blkdev_copy_zone_to_user, &args);
        if (ret < 0)
                return ret;

        rep.nr_zones = ret;
        rep.flags = BLK_ZONE_REP_CAPACITY;
        if (copy_to_user(argp, &rep, sizeof(struct blk_zone_report)))
                return -EFAULT;
        return 0;
}

static int blkdev_truncate_zone_range(struct block_device *bdev,
                blk_mode_t mode, const struct blk_zone_range *zrange)
{
        loff_t start, end;

        if (zrange->sector + zrange->nr_sectors <= zrange->sector ||
            zrange->sector + zrange->nr_sectors > get_capacity(bdev->bd_disk))
                /* Out of range */
                return -EINVAL;

        start = zrange->sector << SECTOR_SHIFT;
        end = ((zrange->sector + zrange->nr_sectors) << SECTOR_SHIFT) - 1;

        return truncate_bdev_range(bdev, mode, start, end);
}

/*
 * BLKRESETZONE, BLKOPENZONE, BLKCLOSEZONE and BLKFINISHZONE ioctl processing.
 * Called from blkdev_ioctl.
 */
int blkdev_zone_mgmt_ioctl(struct block_device *bdev, blk_mode_t mode,
                           unsigned int cmd, unsigned long arg)
{
        void __user *argp = (void __user *)arg;
        struct blk_zone_range zrange;
        enum req_op op;
        int ret;

        if (!argp)
                return -EINVAL;

        if (!bdev_is_zoned(bdev))
                return -ENOTTY;

        if (!(mode & BLK_OPEN_WRITE))
                return -EBADF;

        if (copy_from_user(&zrange, argp, sizeof(struct blk_zone_range)))
                return -EFAULT;

        switch (cmd) {
        case BLKRESETZONE:
                op = REQ_OP_ZONE_RESET;

                /* Invalidate the page cache, including dirty pages. */
                filemap_invalidate_lock(bdev->bd_mapping);
                ret = blkdev_truncate_zone_range(bdev, mode, &zrange);
                if (ret)
                        goto fail;
                break;
        case BLKOPENZONE:
                op = REQ_OP_ZONE_OPEN;
                break;
        case BLKCLOSEZONE:
                op = REQ_OP_ZONE_CLOSE;
                break;
        case BLKFINISHZONE:
                op = REQ_OP_ZONE_FINISH;
                break;
        default:
                return -ENOTTY;
        }

        ret = blkdev_zone_mgmt(bdev, op, zrange.sector, zrange.nr_sectors);

fail:
        if (cmd == BLKRESETZONE)
                filemap_invalidate_unlock(bdev->bd_mapping);

        return ret;
}

static inline bool disk_zone_is_conv(struct gendisk *disk, sector_t sector)
{
        if (!disk->conv_zones_bitmap)
                return false;
        return test_bit(disk_zone_no(disk, sector), disk->conv_zones_bitmap);
}

static bool disk_zone_is_last(struct gendisk *disk, struct blk_zone *zone)
{
        return zone->start + zone->len >= get_capacity(disk);
}

static bool disk_zone_is_full(struct gendisk *disk,
                              unsigned int zno, unsigned int offset_in_zone)
{
        if (zno < disk->nr_zones - 1)
                return offset_in_zone >= disk->zone_capacity;
        return offset_in_zone >= disk->last_zone_capacity;
}

static bool disk_zone_wplug_is_full(struct gendisk *disk,
                                    struct blk_zone_wplug *zwplug)
{
        return disk_zone_is_full(disk, zwplug->zone_no, zwplug->wp_offset);
}

static bool disk_insert_zone_wplug(struct gendisk *disk,
                                   struct blk_zone_wplug *zwplug)
{
        struct blk_zone_wplug *zwplg;
        unsigned long flags;
        unsigned int idx =
                hash_32(zwplug->zone_no, disk->zone_wplugs_hash_bits);

        /*
         * Add the new zone write plug to the hash table, but carefully as we
         * are racing with other submission context, so we may already have a
         * zone write plug for the same zone.
         */
        spin_lock_irqsave(&disk->zone_wplugs_lock, flags);
        hlist_for_each_entry_rcu(zwplg, &disk->zone_wplugs_hash[idx], node) {
                if (zwplg->zone_no == zwplug->zone_no) {
                        spin_unlock_irqrestore(&disk->zone_wplugs_lock, flags);
                        return false;
                }
        }
        hlist_add_head_rcu(&zwplug->node, &disk->zone_wplugs_hash[idx]);
        spin_unlock_irqrestore(&disk->zone_wplugs_lock, flags);

        return true;
}

static struct blk_zone_wplug *disk_get_zone_wplug(struct gendisk *disk,
                                                  sector_t sector)
{
        unsigned int zno = disk_zone_no(disk, sector);
        unsigned int idx = hash_32(zno, disk->zone_wplugs_hash_bits);
        struct blk_zone_wplug *zwplug;

        rcu_read_lock();

        hlist_for_each_entry_rcu(zwplug, &disk->zone_wplugs_hash[idx], node) {
                if (zwplug->zone_no == zno &&
                    atomic_inc_not_zero(&zwplug->ref)) {
                        rcu_read_unlock();
                        return zwplug;
                }
        }

        rcu_read_unlock();

        return NULL;
}

static void disk_free_zone_wplug_rcu(struct rcu_head *rcu_head)
{
        struct blk_zone_wplug *zwplug =
                container_of(rcu_head, struct blk_zone_wplug, rcu_head);

        mempool_free(zwplug, zwplug->disk->zone_wplugs_pool);
}

static inline void disk_put_zone_wplug(struct blk_zone_wplug *zwplug)
{
        if (atomic_dec_and_test(&zwplug->ref)) {
                WARN_ON_ONCE(!bio_list_empty(&zwplug->bio_list));
                WARN_ON_ONCE(!list_empty(&zwplug->link));
                WARN_ON_ONCE(!(zwplug->flags & BLK_ZONE_WPLUG_UNHASHED));

                call_rcu(&zwplug->rcu_head, disk_free_zone_wplug_rcu);
        }
}

static inline bool disk_should_remove_zone_wplug(struct gendisk *disk,
                                                 struct blk_zone_wplug *zwplug)
{
        /* If the zone write plug was already removed, we are done. */
        if (zwplug->flags & BLK_ZONE_WPLUG_UNHASHED)
                return false;

        /* If the zone write plug is still busy, it cannot be removed. */
        if (zwplug->flags & BLK_ZONE_WPLUG_BUSY)
                return false;

        /*
         * Completions of BIOs with blk_zone_write_plug_bio_endio() may
         * happen after handling a request completion with
         * blk_zone_write_plug_finish_request() (e.g. with split BIOs
         * that are chained). In such case, disk_zone_wplug_unplug_bio()
         * should not attempt to remove the zone write plug until all BIO
         * completions are seen. Check by looking at the zone write plug
         * reference count, which is 2 when the plug is unused (one reference
         * taken when the plug was allocated and another reference taken by the
         * caller context).
         */
        if (atomic_read(&zwplug->ref) > 2)
                return false;

        /* We can remove zone write plugs for zones that are empty or full. */
        return !zwplug->wp_offset || disk_zone_wplug_is_full(disk, zwplug);
}

static void disk_remove_zone_wplug(struct gendisk *disk,
                                   struct blk_zone_wplug *zwplug)
{
        unsigned long flags;

        /* If the zone write plug was already removed, we have nothing to do. */
        if (zwplug->flags & BLK_ZONE_WPLUG_UNHASHED)
                return;

        /*
         * Mark the zone write plug as unhashed and drop the extra reference we
         * took when the plug was inserted in the hash table.
         */
        zwplug->flags |= BLK_ZONE_WPLUG_UNHASHED;
        spin_lock_irqsave(&disk->zone_wplugs_lock, flags);
        hlist_del_init_rcu(&zwplug->node);
        spin_unlock_irqrestore(&disk->zone_wplugs_lock, flags);
        disk_put_zone_wplug(zwplug);
}

static void blk_zone_wplug_bio_work(struct work_struct *work);

/*
 * Get a reference on the write plug for the zone containing @sector.
 * If the plug does not exist, it is allocated and hashed.
 * Return a pointer to the zone write plug with the plug spinlock held.
 */
static struct blk_zone_wplug *disk_get_and_lock_zone_wplug(struct gendisk *disk,
                                        sector_t sector, gfp_t gfp_mask,
                                        unsigned long *flags)
{
        unsigned int zno = disk_zone_no(disk, sector);
        struct blk_zone_wplug *zwplug;

again:
        zwplug = disk_get_zone_wplug(disk, sector);
        if (zwplug) {
                /*
                 * Check that a BIO completion or a zone reset or finish
                 * operation has not already removed the zone write plug from
                 * the hash table and dropped its reference count. In such case,
                 * we need to get a new plug so start over from the beginning.
                 */
                spin_lock_irqsave(&zwplug->lock, *flags);
                if (zwplug->flags & BLK_ZONE_WPLUG_UNHASHED) {
                        spin_unlock_irqrestore(&zwplug->lock, *flags);
                        disk_put_zone_wplug(zwplug);
                        goto again;
                }
                return zwplug;
        }

        /*
         * Allocate and initialize a zone write plug with an extra reference
         * so that it is not freed when the zone write plug becomes idle without
         * the zone being full.
         */
        zwplug = mempool_alloc(disk->zone_wplugs_pool, gfp_mask);
        if (!zwplug)
                return NULL;

        INIT_HLIST_NODE(&zwplug->node);
        INIT_LIST_HEAD(&zwplug->link);
        atomic_set(&zwplug->ref, 2);
        spin_lock_init(&zwplug->lock);
        zwplug->flags = 0;
        zwplug->zone_no = zno;
        zwplug->wp_offset = sector & (disk->queue->limits.chunk_sectors - 1);
        bio_list_init(&zwplug->bio_list);
        INIT_WORK(&zwplug->bio_work, blk_zone_wplug_bio_work);
        zwplug->disk = disk;

        spin_lock_irqsave(&zwplug->lock, *flags);

        /*
         * Insert the new zone write plug in the hash table. This can fail only
         * if another context already inserted a plug. Retry from the beginning
         * in such case.
         */
        if (!disk_insert_zone_wplug(disk, zwplug)) {
                spin_unlock_irqrestore(&zwplug->lock, *flags);
                mempool_free(zwplug, disk->zone_wplugs_pool);
                goto again;
        }

        return zwplug;
}

static inline void blk_zone_wplug_bio_io_error(struct blk_zone_wplug *zwplug,
                                               struct bio *bio)
{
        struct request_queue *q = zwplug->disk->queue;

        bio_clear_flag(bio, BIO_ZONE_WRITE_PLUGGING);
        bio_io_error(bio);
        disk_put_zone_wplug(zwplug);
        blk_queue_exit(q);
}

/*
 * Abort (fail) all plugged BIOs of a zone write plug.
 */
static void disk_zone_wplug_abort(struct blk_zone_wplug *zwplug)
{
        struct bio *bio;

        while ((bio = bio_list_pop(&zwplug->bio_list)))
                blk_zone_wplug_bio_io_error(zwplug, bio);
}

/*
 * Abort (fail) all plugged BIOs of a zone write plug that are not aligned
 * with the assumed write pointer location of the zone when the BIO will
 * be unplugged.
 */
static void disk_zone_wplug_abort_unaligned(struct gendisk *disk,
                                            struct blk_zone_wplug *zwplug)
{
        unsigned int wp_offset = zwplug->wp_offset;
        struct bio_list bl = BIO_EMPTY_LIST;
        struct bio *bio;

        while ((bio = bio_list_pop(&zwplug->bio_list))) {
                if (disk_zone_is_full(disk, zwplug->zone_no, wp_offset) ||
                    (bio_op(bio) != REQ_OP_ZONE_APPEND &&
                     bio_offset_from_zone_start(bio) != wp_offset)) {
                        blk_zone_wplug_bio_io_error(zwplug, bio);
                        continue;
                }

                wp_offset += bio_sectors(bio);
                bio_list_add(&bl, bio);
        }

        bio_list_merge(&zwplug->bio_list, &bl);
}

static inline void disk_zone_wplug_set_error(struct gendisk *disk,
                                             struct blk_zone_wplug *zwplug)
{
        unsigned long flags;

        if (zwplug->flags & BLK_ZONE_WPLUG_ERROR)
                return;

        /*
         * At this point, we already have a reference on the zone write plug.
         * However, since we are going to add the plug to the disk zone write
         * plugs work list, increase its reference count. This reference will
         * be dropped in disk_zone_wplugs_work() once the error state is
         * handled, or in disk_zone_wplug_clear_error() if the zone is reset or
         * finished.
         */
        zwplug->flags |= BLK_ZONE_WPLUG_ERROR;
        atomic_inc(&zwplug->ref);

        spin_lock_irqsave(&disk->zone_wplugs_lock, flags);
        list_add_tail(&zwplug->link, &disk->zone_wplugs_err_list);
        spin_unlock_irqrestore(&disk->zone_wplugs_lock, flags);
}

static inline void disk_zone_wplug_clear_error(struct gendisk *disk,
                                               struct blk_zone_wplug *zwplug)
{
        unsigned long flags;

        if (!(zwplug->flags & BLK_ZONE_WPLUG_ERROR))
                return;

        /*
         * We are racing with the error handling work which drops the reference
         * on the zone write plug after handling the error state. So remove the
         * plug from the error list and drop its reference count only if the
         * error handling has not yet started, that is, if the zone write plug
         * is still listed.
         */
        spin_lock_irqsave(&disk->zone_wplugs_lock, flags);
        if (!list_empty(&zwplug->link)) {
                list_del_init(&zwplug->link);
                zwplug->flags &= ~BLK_ZONE_WPLUG_ERROR;
                disk_put_zone_wplug(zwplug);
        }
        spin_unlock_irqrestore(&disk->zone_wplugs_lock, flags);
}

/*
 * Set a zone write plug write pointer offset to either 0 (zone reset case)
 * or to the zone size (zone finish case). This aborts all plugged BIOs, which
 * is fine to do as doing a zone reset or zone finish while writes are in-flight
 * is a mistake from the user which will most likely cause all plugged BIOs to
 * fail anyway.
 */
static void disk_zone_wplug_set_wp_offset(struct gendisk *disk,
                                          struct blk_zone_wplug *zwplug,
                                          unsigned int wp_offset)
{
        unsigned long flags;

        spin_lock_irqsave(&zwplug->lock, flags);

        /*
         * Make sure that a BIO completion or another zone reset or finish
         * operation has not already removed the plug from the hash table.
         */
        if (zwplug->flags & BLK_ZONE_WPLUG_UNHASHED) {
                spin_unlock_irqrestore(&zwplug->lock, flags);
                return;
        }

        /* Update the zone write pointer and abort all plugged BIOs. */
        zwplug->wp_offset = wp_offset;
        disk_zone_wplug_abort(zwplug);

        /*
         * Updating the write pointer offset puts back the zone
         * in a good state. So clear the error flag and decrement the
         * error count if we were in error state.
         */
        disk_zone_wplug_clear_error(disk, zwplug);

        /*
         * The zone write plug now has no BIO plugged: remove it from the
         * hash table so that it cannot be seen. The plug will be freed
         * when the last reference is dropped.
         */
        if (disk_should_remove_zone_wplug(disk, zwplug))
                disk_remove_zone_wplug(disk, zwplug);

        spin_unlock_irqrestore(&zwplug->lock, flags);
}

static bool blk_zone_wplug_handle_reset_or_finish(struct bio *bio,
                                                  unsigned int wp_offset)
{
        struct gendisk *disk = bio->bi_bdev->bd_disk;
        sector_t sector = bio->bi_iter.bi_sector;
        struct blk_zone_wplug *zwplug;

        /* Conventional zones cannot be reset nor finished. */
        if (disk_zone_is_conv(disk, sector)) {
                bio_io_error(bio);
                return true;
        }

        /*
         * If we have a zone write plug, set its write pointer offset to 0
         * (reset case) or to the zone size (finish case). This will abort all
         * BIOs plugged for the target zone. It is fine as resetting or
         * finishing zones while writes are still in-flight will result in the
         * writes failing anyway.
         */
        zwplug = disk_get_zone_wplug(disk, sector);
        if (zwplug) {
                disk_zone_wplug_set_wp_offset(disk, zwplug, wp_offset);
                disk_put_zone_wplug(zwplug);
        }

        return false;
}

static bool blk_zone_wplug_handle_reset_all(struct bio *bio)
{
        struct gendisk *disk = bio->bi_bdev->bd_disk;
        struct blk_zone_wplug *zwplug;
        sector_t sector;

        /*
         * Set the write pointer offset of all zone write plugs to 0. This will
         * abort all plugged BIOs. It is fine as resetting zones while writes
         * are still in-flight will result in the writes failing anyway.
         */
        for (sector = 0; sector < get_capacity(disk);
             sector += disk->queue->limits.chunk_sectors) {
                zwplug = disk_get_zone_wplug(disk, sector);
                if (zwplug) {
                        disk_zone_wplug_set_wp_offset(disk, zwplug, 0);
                        disk_put_zone_wplug(zwplug);
                }
        }

        return false;
}

static inline void blk_zone_wplug_add_bio(struct blk_zone_wplug *zwplug,
                                          struct bio *bio, unsigned int nr_segs)
{
        /*
         * Grab an extra reference on the BIO request queue usage counter.
         * This reference will be reused to submit a request for the BIO for
         * blk-mq devices and dropped when the BIO is failed and after
         * it is issued in the case of BIO-based devices.
         */
        percpu_ref_get(&bio->bi_bdev->bd_disk->queue->q_usage_counter);

        /*
         * The BIO is being plugged and thus will have to wait for the on-going
         * write and for all other writes already plugged. So polling makes
         * no sense.
         */
        bio_clear_polled(bio);

        /*
         * Reuse the poll cookie field to store the number of segments when
         * split to the hardware limits.
         */
        bio->__bi_nr_segments = nr_segs;

        /*
         * We always receive BIOs after they are split and ready to be issued.
         * The block layer passes the parts of a split BIO in order, and the
         * user must also issue write sequentially. So simply add the new BIO
         * at the tail of the list to preserve the sequential write order.
         */
        bio_list_add(&zwplug->bio_list, bio);
}

/*
 * Called from bio_attempt_back_merge() when a BIO was merged with a request.
 */
void blk_zone_write_plug_bio_merged(struct bio *bio)
{
        struct blk_zone_wplug *zwplug;
        unsigned long flags;

        /*
         * If the BIO was already plugged, then we were called through
         * blk_zone_write_plug_init_request() -> blk_attempt_bio_merge().
         * For this case, we already hold a reference on the zone write plug for
         * the BIO and blk_zone_write_plug_init_request() will handle the
         * zone write pointer offset update.
         */
        if (bio_flagged(bio, BIO_ZONE_WRITE_PLUGGING))
                return;

        bio_set_flag(bio, BIO_ZONE_WRITE_PLUGGING);

        /*
         * Get a reference on the zone write plug of the target zone and advance
         * the zone write pointer offset. Given that this is a merge, we already
         * have at least one request and one BIO referencing the zone write
         * plug. So this should not fail.
         */
        zwplug = disk_get_zone_wplug(bio->bi_bdev->bd_disk,
                                     bio->bi_iter.bi_sector);
        if (WARN_ON_ONCE(!zwplug))
                return;

        spin_lock_irqsave(&zwplug->lock, flags);
        zwplug->wp_offset += bio_sectors(bio);
        spin_unlock_irqrestore(&zwplug->lock, flags);
}

/*
 * Attempt to merge plugged BIOs with a newly prepared request for a BIO that
 * already went through zone write plugging (either a new BIO or one that was
 * unplugged).
 */
void blk_zone_write_plug_init_request(struct request *req)
{
        sector_t req_back_sector = blk_rq_pos(req) + blk_rq_sectors(req);
        struct request_queue *q = req->q;
        struct gendisk *disk = q->disk;
        struct blk_zone_wplug *zwplug =
                disk_get_zone_wplug(disk, blk_rq_pos(req));
        unsigned long flags;
        struct bio *bio;

        if (WARN_ON_ONCE(!zwplug))
                return;

        /*
         * Indicate that completion of this request needs to be handled with
         * blk_zone_write_plug_finish_request(), which will drop the reference
         * on the zone write plug we took above on entry to this function.
         */
        req->rq_flags |= RQF_ZONE_WRITE_PLUGGING;

        if (blk_queue_nomerges(q))
                return;

        /*
         * Walk through the list of plugged BIOs to check if they can be merged
         * into the back of the request.
         */
        spin_lock_irqsave(&zwplug->lock, flags);
        while (!disk_zone_wplug_is_full(disk, zwplug)) {
                bio = bio_list_peek(&zwplug->bio_list);
                if (!bio)
                        break;

                if (bio->bi_iter.bi_sector != req_back_sector ||
                    !blk_rq_merge_ok(req, bio))
                        break;

                WARN_ON_ONCE(bio_op(bio) != REQ_OP_WRITE_ZEROES &&
                             !bio->__bi_nr_segments);

                bio_list_pop(&zwplug->bio_list);
                if (bio_attempt_back_merge(req, bio, bio->__bi_nr_segments) !=
                    BIO_MERGE_OK) {
                        bio_list_add_head(&zwplug->bio_list, bio);
                        break;
                }

                /*
                 * Drop the extra reference on the queue usage we got when
                 * plugging the BIO and advance the write pointer offset.
                 */
                blk_queue_exit(q);
                zwplug->wp_offset += bio_sectors(bio);

                req_back_sector += bio_sectors(bio);
        }
        spin_unlock_irqrestore(&zwplug->lock, flags);
}

/*
 * Check and prepare a BIO for submission by incrementing the write pointer
 * offset of its zone write plug and changing zone append operations into
 * regular write when zone append emulation is needed.
 */
static bool blk_zone_wplug_prepare_bio(struct blk_zone_wplug *zwplug,
                                       struct bio *bio)
{
        struct gendisk *disk = bio->bi_bdev->bd_disk;

        /*
         * Check that the user is not attempting to write to a full zone.
         * We know such BIO will fail, and that would potentially overflow our
         * write pointer offset beyond the end of the zone.
         */
        if (disk_zone_wplug_is_full(disk, zwplug))
                goto err;

        if (bio_op(bio) == REQ_OP_ZONE_APPEND) {
                /*
                 * Use a regular write starting at the current write pointer.
                 * Similarly to native zone append operations, do not allow
                 * merging.
                 */
                bio->bi_opf &= ~REQ_OP_MASK;
                bio->bi_opf |= REQ_OP_WRITE | REQ_NOMERGE;
                bio->bi_iter.bi_sector += zwplug->wp_offset;

                /*
                 * Remember that this BIO is in fact a zone append operation
                 * so that we can restore its operation code on completion.
                 */
                bio_set_flag(bio, BIO_EMULATES_ZONE_APPEND);
        } else {
                /*
                 * Check for non-sequential writes early because we avoid a
                 * whole lot of error handling trouble if we don't send it off
                 * to the driver.
                 */
                if (bio_offset_from_zone_start(bio) != zwplug->wp_offset)
                        goto err;
        }

        /* Advance the zone write pointer offset. */
        zwplug->wp_offset += bio_sectors(bio);

        return true;

err:
        /* We detected an invalid write BIO: schedule error recovery. */
        disk_zone_wplug_set_error(disk, zwplug);
        kblockd_schedule_work(&disk->zone_wplugs_work);
        return false;
}

static bool blk_zone_wplug_handle_write(struct bio *bio, unsigned int nr_segs)
{
        struct gendisk *disk = bio->bi_bdev->bd_disk;
        sector_t sector = bio->bi_iter.bi_sector;
        struct blk_zone_wplug *zwplug;
        gfp_t gfp_mask = GFP_NOIO;
        unsigned long flags;

        /*
         * BIOs must be fully contained within a zone so that we use the correct
         * zone write plug for the entire BIO. For blk-mq devices, the block
         * layer should already have done any splitting required to ensure this
         * and this BIO should thus not be straddling zone boundaries. For
         * BIO-based devices, it is the responsibility of the driver to split
         * the bio before submitting it.
         */
        if (WARN_ON_ONCE(bio_straddles_zones(bio))) {
                bio_io_error(bio);
                return true;
        }

        /* Conventional zones do not need write plugging. */
        if (disk_zone_is_conv(disk, sector)) {
                /* Zone append to conventional zones is not allowed. */
                if (bio_op(bio) == REQ_OP_ZONE_APPEND) {
                        bio_io_error(bio);
                        return true;
                }
                return false;
        }

        if (bio->bi_opf & REQ_NOWAIT)
                gfp_mask = GFP_NOWAIT;

        zwplug = disk_get_and_lock_zone_wplug(disk, sector, gfp_mask, &flags);
        if (!zwplug) {
                bio_io_error(bio);
                return true;
        }

        /* Indicate that this BIO is being handled using zone write plugging. */
        bio_set_flag(bio, BIO_ZONE_WRITE_PLUGGING);

        /*
         * If the zone is already plugged or has a pending error, add the BIO
         * to the plug BIO list. Otherwise, plug and let the BIO execute.
         */
        if (zwplug->flags & BLK_ZONE_WPLUG_BUSY)
                goto plug;

        /*
         * If an error is detected when preparing the BIO, add it to the BIO
         * list so that error recovery can deal with it.
         */
        if (!blk_zone_wplug_prepare_bio(zwplug, bio))
                goto plug;

        zwplug->flags |= BLK_ZONE_WPLUG_PLUGGED;

        spin_unlock_irqrestore(&zwplug->lock, flags);

        return false;

plug:
        zwplug->flags |= BLK_ZONE_WPLUG_PLUGGED;
        blk_zone_wplug_add_bio(zwplug, bio, nr_segs);

        spin_unlock_irqrestore(&zwplug->lock, flags);

        return true;
}

/**
 * blk_zone_plug_bio - Handle a zone write BIO with zone write plugging
 * @bio: The BIO being submitted
 * @nr_segs: The number of physical segments of @bio
 *
 * Handle write, write zeroes and zone append operations requiring emulation
 * using zone write plugging.
 *
 * Return true whenever @bio execution needs to be delayed through the zone
 * write plug. Otherwise, return false to let the submission path process
 * @bio normally.
 */
bool blk_zone_plug_bio(struct bio *bio, unsigned int nr_segs)
{
        struct block_device *bdev = bio->bi_bdev;

        if (!bdev->bd_disk->zone_wplugs_hash)
                return false;

        /*
         * If the BIO already has the plugging flag set, then it was already
         * handled through this path and this is a submission from the zone
         * plug bio submit work.
         */
        if (bio_flagged(bio, BIO_ZONE_WRITE_PLUGGING))
                return false;

        /*
         * We do not need to do anything special for empty flush BIOs, e.g
         * BIOs such as issued by blkdev_issue_flush(). The is because it is
         * the responsibility of the user to first wait for the completion of
         * write operations for flush to have any effect on the persistence of
         * the written data.
         */
        if (op_is_flush(bio->bi_opf) && !bio_sectors(bio))
                return false;

        /*
         * Regular writes and write zeroes need to be handled through the target
         * zone write plug. This includes writes with REQ_FUA | REQ_PREFLUSH
         * which may need to go through the flush machinery depending on the
         * target device capabilities. Plugging such writes is fine as the flush
         * machinery operates at the request level, below the plug, and
         * completion of the flush sequence will go through the regular BIO
         * completion, which will handle zone write plugging.
         * Zone append operations for devices that requested emulation must
         * also be plugged so that these BIOs can be changed into regular
         * write BIOs.
         * Zone reset, reset all and finish commands need special treatment
         * to correctly track the write pointer offset of zones. These commands
         * are not plugged as we do not need serialization with write
         * operations. It is the responsibility of the user to not issue reset
         * and finish commands when write operations are in flight.
         */
        switch (bio_op(bio)) {
        case REQ_OP_ZONE_APPEND:
                if (!bdev_emulates_zone_append(bdev))
                        return false;
                fallthrough;
        case REQ_OP_WRITE:
        case REQ_OP_WRITE_ZEROES:
                return blk_zone_wplug_handle_write(bio, nr_segs);
        case REQ_OP_ZONE_RESET:
                return blk_zone_wplug_handle_reset_or_finish(bio, 0);
        case REQ_OP_ZONE_FINISH:
                return blk_zone_wplug_handle_reset_or_finish(bio,
                                                bdev_zone_sectors(bdev));
        case REQ_OP_ZONE_RESET_ALL:
                return blk_zone_wplug_handle_reset_all(bio);
        default:
                return false;
        }

        return false;
}
EXPORT_SYMBOL_GPL(blk_zone_plug_bio);

static void disk_zone_wplug_schedule_bio_work(struct gendisk *disk,
                                              struct blk_zone_wplug *zwplug)
{
        /*
         * Take a reference on the zone write plug and schedule the submission
         * of the next plugged BIO. blk_zone_wplug_bio_work() will release the
         * reference we take here.
         */
        WARN_ON_ONCE(!(zwplug->flags & BLK_ZONE_WPLUG_PLUGGED));
        atomic_inc(&zwplug->ref);
        queue_work(disk->zone_wplugs_wq, &zwplug->bio_work);
}

static void disk_zone_wplug_unplug_bio(struct gendisk *disk,
                                       struct blk_zone_wplug *zwplug)
{
        unsigned long flags;

        spin_lock_irqsave(&zwplug->lock, flags);

        /*
         * If we had an error, schedule error recovery. The recovery work
         * will restart submission of plugged BIOs.
         */
        if (zwplug->flags & BLK_ZONE_WPLUG_ERROR) {
                spin_unlock_irqrestore(&zwplug->lock, flags);
                kblockd_schedule_work(&disk->zone_wplugs_work);
                return;
        }

        /* Schedule submission of the next plugged BIO if we have one. */
        if (!bio_list_empty(&zwplug->bio_list)) {
                disk_zone_wplug_schedule_bio_work(disk, zwplug);
                spin_unlock_irqrestore(&zwplug->lock, flags);
                return;
        }

        zwplug->flags &= ~BLK_ZONE_WPLUG_PLUGGED;

        /*
         * If the zone is full (it was fully written or finished, or empty
         * (it was reset), remove its zone write plug from the hash table.
         */
        if (disk_should_remove_zone_wplug(disk, zwplug))
                disk_remove_zone_wplug(disk, zwplug);

        spin_unlock_irqrestore(&zwplug->lock, flags);
}

void blk_zone_write_plug_bio_endio(struct bio *bio)
{
        struct gendisk *disk = bio->bi_bdev->bd_disk;
        struct blk_zone_wplug *zwplug =
                disk_get_zone_wplug(disk, bio->bi_iter.bi_sector);
        unsigned long flags;

        if (WARN_ON_ONCE(!zwplug))
                return;

        /* Make sure we do not see this BIO again by clearing the plug flag. */
        bio_clear_flag(bio, BIO_ZONE_WRITE_PLUGGING);

        /*
         * If this is a regular write emulating a zone append operation,
         * restore the original operation code.
         */
        if (bio_flagged(bio, BIO_EMULATES_ZONE_APPEND)) {
                bio->bi_opf &= ~REQ_OP_MASK;
                bio->bi_opf |= REQ_OP_ZONE_APPEND;
        }

        /*
         * If the BIO failed, mark the plug as having an error to trigger
         * recovery.
         */
        if (bio->bi_status != BLK_STS_OK) {
                spin_lock_irqsave(&zwplug->lock, flags);
                disk_zone_wplug_set_error(disk, zwplug);
                spin_unlock_irqrestore(&zwplug->lock, flags);
        }

        /* Drop the reference we took when the BIO was issued. */
        disk_put_zone_wplug(zwplug);

        /*
         * For BIO-based devices, blk_zone_write_plug_finish_request()
         * is not called. So we need to schedule execution of the next
         * plugged BIO here.
         */
        if (bdev_test_flag(bio->bi_bdev, BD_HAS_SUBMIT_BIO))
                disk_zone_wplug_unplug_bio(disk, zwplug);

        /* Drop the reference we took when entering this function. */
        disk_put_zone_wplug(zwplug);
}

void blk_zone_write_plug_finish_request(struct request *req)
{
        struct gendisk *disk = req->q->disk;
        struct blk_zone_wplug *zwplug;

        zwplug = disk_get_zone_wplug(disk, req->__sector);
        if (WARN_ON_ONCE(!zwplug))
                return;

        req->rq_flags &= ~RQF_ZONE_WRITE_PLUGGING;

        /*
         * Drop the reference we took when the request was initialized in
         * blk_zone_write_plug_init_request().
         */
        disk_put_zone_wplug(zwplug);

        disk_zone_wplug_unplug_bio(disk, zwplug);

        /* Drop the reference we took when entering this function. */
        disk_put_zone_wplug(zwplug);
}

static void blk_zone_wplug_bio_work(struct work_struct *work)
{
        struct blk_zone_wplug *zwplug =
                container_of(work, struct blk_zone_wplug, bio_work);
        struct block_device *bdev;
        unsigned long flags;
        struct bio *bio;

        /*
         * Submit the next plugged BIO. If we do not have any, clear
         * the plugged flag.
         */
        spin_lock_irqsave(&zwplug->lock, flags);

        bio = bio_list_pop(&zwplug->bio_list);
        if (!bio) {
                zwplug->flags &= ~BLK_ZONE_WPLUG_PLUGGED;
                spin_unlock_irqrestore(&zwplug->lock, flags);
                goto put_zwplug;
        }

        if (!blk_zone_wplug_prepare_bio(zwplug, bio)) {
                /* Error recovery will decide what to do with the BIO. */
                bio_list_add_head(&zwplug->bio_list, bio);
                spin_unlock_irqrestore(&zwplug->lock, flags);
                goto put_zwplug;
        }

        spin_unlock_irqrestore(&zwplug->lock, flags);

        bdev = bio->bi_bdev;
        submit_bio_noacct_nocheck(bio);

        /*
         * blk-mq devices will reuse the extra reference on the request queue
         * usage counter we took when the BIO was plugged, but the submission
         * path for BIO-based devices will not do that. So drop this extra
         * reference here.
         */
        if (bdev_test_flag(bdev, BD_HAS_SUBMIT_BIO))
                blk_queue_exit(bdev->bd_disk->queue);

put_zwplug:
        /* Drop the reference we took in disk_zone_wplug_schedule_bio_work(). */
        disk_put_zone_wplug(zwplug);
}

static unsigned int blk_zone_wp_offset(struct blk_zone *zone)
{
        switch (zone->cond) {
        case BLK_ZONE_COND_IMP_OPEN:
        case BLK_ZONE_COND_EXP_OPEN:
        case BLK_ZONE_COND_CLOSED:
                return zone->wp - zone->start;
        case BLK_ZONE_COND_FULL:
                return zone->len;
        case BLK_ZONE_COND_EMPTY:
                return 0;
        case BLK_ZONE_COND_NOT_WP:
        case BLK_ZONE_COND_OFFLINE:
        case BLK_ZONE_COND_READONLY:
        default:
                /*
                 * Conventional, offline and read-only zones do not have a valid
                 * write pointer.
                 */
                return UINT_MAX;
        }
}

static int blk_zone_wplug_report_zone_cb(struct blk_zone *zone,
                                         unsigned int idx, void *data)
{
        struct blk_zone *zonep = data;

        *zonep = *zone;
        return 0;
}

static void disk_zone_wplug_handle_error(struct gendisk *disk,
                                         struct blk_zone_wplug *zwplug)
{
        sector_t zone_start_sector =
                bdev_zone_sectors(disk->part0) * zwplug->zone_no;
        unsigned int noio_flag;
        struct blk_zone zone;
        unsigned long flags;
        int ret;

        /* Get the current zone information from the device. */
        noio_flag = memalloc_noio_save();
        ret = disk->fops->report_zones(disk, zone_start_sector, 1,
                                       blk_zone_wplug_report_zone_cb, &zone);
        memalloc_noio_restore(noio_flag);

        spin_lock_irqsave(&zwplug->lock, flags);

        /*
         * A zone reset or finish may have cleared the error already. In such
         * case, do nothing as the report zones may have seen the "old" write
         * pointer value before the reset/finish operation completed.
         */
        if (!(zwplug->flags & BLK_ZONE_WPLUG_ERROR))
                goto unlock;

        zwplug->flags &= ~BLK_ZONE_WPLUG_ERROR;

        if (ret != 1) {
                /*
                 * We failed to get the zone information, meaning that something
                 * is likely really wrong with the device. Abort all remaining
                 * plugged BIOs as otherwise we could endup waiting forever on
                 * plugged BIOs to complete if there is a queue freeze on-going.
                 */
                disk_zone_wplug_abort(zwplug);
                goto unplug;
        }

        /* Update the zone write pointer offset. */
        zwplug->wp_offset = blk_zone_wp_offset(&zone);
        disk_zone_wplug_abort_unaligned(disk, zwplug);

        /* Restart BIO submission if we still have any BIO left. */
        if (!bio_list_empty(&zwplug->bio_list)) {
                disk_zone_wplug_schedule_bio_work(disk, zwplug);
                goto unlock;
        }

unplug:
        zwplug->flags &= ~BLK_ZONE_WPLUG_PLUGGED;
        if (disk_should_remove_zone_wplug(disk, zwplug))
                disk_remove_zone_wplug(disk, zwplug);

unlock:
        spin_unlock_irqrestore(&zwplug->lock, flags);
}

static void disk_zone_wplugs_work(struct work_struct *work)
{
        struct gendisk *disk =
                container_of(work, struct gendisk, zone_wplugs_work);
        struct blk_zone_wplug *zwplug;
        unsigned long flags;

        spin_lock_irqsave(&disk->zone_wplugs_lock, flags);

        while (!list_empty(&disk->zone_wplugs_err_list)) {
                zwplug = list_first_entry(&disk->zone_wplugs_err_list,
                                          struct blk_zone_wplug, link);
                list_del_init(&zwplug->link);
                spin_unlock_irqrestore(&disk->zone_wplugs_lock, flags);

                disk_zone_wplug_handle_error(disk, zwplug);
                disk_put_zone_wplug(zwplug);

                spin_lock_irqsave(&disk->zone_wplugs_lock, flags);
        }

        spin_unlock_irqrestore(&disk->zone_wplugs_lock, flags);
}

static inline unsigned int disk_zone_wplugs_hash_size(struct gendisk *disk)
{
        return 1U << disk->zone_wplugs_hash_bits;
}

void disk_init_zone_resources(struct gendisk *disk)
{
        spin_lock_init(&disk->zone_wplugs_lock);
        INIT_LIST_HEAD(&disk->zone_wplugs_err_list);
        INIT_WORK(&disk->zone_wplugs_work, disk_zone_wplugs_work);
}

/*
 * For the size of a disk zone write plug hash table, use the size of the
 * zone write plug mempool, which is the maximum of the disk open zones and
 * active zones limits. But do not exceed 4KB (512 hlist head entries), that is,
 * 9 bits. For a disk that has no limits, mempool size defaults to 128.
 */
#define BLK_ZONE_WPLUG_MAX_HASH_BITS            9
#define BLK_ZONE_WPLUG_DEFAULT_POOL_SIZE        128

static int disk_alloc_zone_resources(struct gendisk *disk,
                                     unsigned int pool_size)
{
        unsigned int i;

        disk->zone_wplugs_hash_bits =
                min(ilog2(pool_size) + 1, BLK_ZONE_WPLUG_MAX_HASH_BITS);

        disk->zone_wplugs_hash =
                kcalloc(disk_zone_wplugs_hash_size(disk),
                        sizeof(struct hlist_head), GFP_KERNEL);
        if (!disk->zone_wplugs_hash)
                return -ENOMEM;

        for (i = 0; i < disk_zone_wplugs_hash_size(disk); i++)
                INIT_HLIST_HEAD(&disk->zone_wplugs_hash[i]);

        disk->zone_wplugs_pool = mempool_create_kmalloc_pool(pool_size,
                                                sizeof(struct blk_zone_wplug));
        if (!disk->zone_wplugs_pool)
                goto free_hash;

        disk->zone_wplugs_wq =
                alloc_workqueue("%s_zwplugs", WQ_MEM_RECLAIM | WQ_HIGHPRI,
                                pool_size, disk->disk_name);
        if (!disk->zone_wplugs_wq)
                goto destroy_pool;

        return 0;

destroy_pool:
        mempool_destroy(disk->zone_wplugs_pool);
        disk->zone_wplugs_pool = NULL;
free_hash:
        kfree(disk->zone_wplugs_hash);
        disk->zone_wplugs_hash = NULL;
        disk->zone_wplugs_hash_bits = 0;
        return -ENOMEM;
}

static void disk_destroy_zone_wplugs_hash_table(struct gendisk *disk)
{
        struct blk_zone_wplug *zwplug;
        unsigned int i;

        if (!disk->zone_wplugs_hash)
                return;

        /* Free all the zone write plugs we have. */
        for (i = 0; i < disk_zone_wplugs_hash_size(disk); i++) {
                while (!hlist_empty(&disk->zone_wplugs_hash[i])) {
                        zwplug = hlist_entry(disk->zone_wplugs_hash[i].first,
                                             struct blk_zone_wplug, node);
                        atomic_inc(&zwplug->ref);
                        disk_remove_zone_wplug(disk, zwplug);
                        disk_put_zone_wplug(zwplug);
                }
        }

        kfree(disk->zone_wplugs_hash);
        disk->zone_wplugs_hash = NULL;
        disk->zone_wplugs_hash_bits = 0;
}

void disk_free_zone_resources(struct gendisk *disk)
{
        if (!disk->zone_wplugs_pool)
                return;

        cancel_work_sync(&disk->zone_wplugs_work);

        if (disk->zone_wplugs_wq) {
                destroy_workqueue(disk->zone_wplugs_wq);
                disk->zone_wplugs_wq = NULL;
        }

        disk_destroy_zone_wplugs_hash_table(disk);

        /*
         * Wait for the zone write plugs to be RCU-freed before
         * destorying the mempool.
         */
        rcu_barrier();

        mempool_destroy(disk->zone_wplugs_pool);
        disk->zone_wplugs_pool = NULL;

        bitmap_free(disk->conv_zones_bitmap);
        disk->conv_zones_bitmap = NULL;
        disk->zone_capacity = 0;
        disk->last_zone_capacity = 0;
        disk->nr_zones = 0;
}

static inline bool disk_need_zone_resources(struct gendisk *disk)
{
        /*
         * All mq zoned devices need zone resources so that the block layer
         * can automatically handle write BIO plugging. BIO-based device drivers
         * (e.g. DM devices) are normally responsible for handling zone write
         * ordering and do not need zone resources, unless the driver requires
         * zone append emulation.
         */
        return queue_is_mq(disk->queue) ||
                queue_emulates_zone_append(disk->queue);
}

static int disk_revalidate_zone_resources(struct gendisk *disk,
                                          unsigned int nr_zones)
{
        struct queue_limits *lim = &disk->queue->limits;
        unsigned int pool_size;

        if (!disk_need_zone_resources(disk))
                return 0;

        /*
         * If the device has no limit on the maximum number of open and active
         * zones, use BLK_ZONE_WPLUG_DEFAULT_POOL_SIZE.
         */
        pool_size = max(lim->max_open_zones, lim->max_active_zones);
        if (!pool_size)
                pool_size = min(BLK_ZONE_WPLUG_DEFAULT_POOL_SIZE, nr_zones);

        if (!disk->zone_wplugs_hash)
                return disk_alloc_zone_resources(disk, pool_size);

        return 0;
}

struct blk_revalidate_zone_args {
        struct gendisk  *disk;
        unsigned long   *conv_zones_bitmap;
        unsigned int    nr_zones;
        unsigned int    zone_capacity;
        unsigned int    last_zone_capacity;
        sector_t        sector;
};

/*
 * Update the disk zone resources information and device queue limits.
 * The disk queue is frozen when this is executed.
 */
static int disk_update_zone_resources(struct gendisk *disk,
                                      struct blk_revalidate_zone_args *args)
{
        struct request_queue *q = disk->queue;
        unsigned int nr_seq_zones, nr_conv_zones = 0;
        unsigned int pool_size;
        struct queue_limits lim;

        disk->nr_zones = args->nr_zones;
        disk->zone_capacity = args->zone_capacity;
        disk->last_zone_capacity = args->last_zone_capacity;
        swap(disk->conv_zones_bitmap, args->conv_zones_bitmap);
        if (disk->conv_zones_bitmap)
                nr_conv_zones = bitmap_weight(disk->conv_zones_bitmap,
                                              disk->nr_zones);
        if (nr_conv_zones >= disk->nr_zones) {
                pr_warn("%s: Invalid number of conventional zones %u / %u\n",
                        disk->disk_name, nr_conv_zones, disk->nr_zones);
                return -ENODEV;
        }

        lim = queue_limits_start_update(q);

        /*
         * Some devices can advertize zone resource limits that are larger than
         * the number of sequential zones of the zoned block device, e.g. a
         * small ZNS namespace. For such case, assume that the zoned device has
         * no zone resource limits.
         */
        nr_seq_zones = disk->nr_zones - nr_conv_zones;
        if (lim.max_open_zones >= nr_seq_zones)
                lim.max_open_zones = 0;
        if (lim.max_active_zones >= nr_seq_zones)
                lim.max_active_zones = 0;

        if (!disk->zone_wplugs_pool)
                goto commit;

        /*
         * If the device has no limit on the maximum number of open and active
         * zones, set its max open zone limit to the mempool size to indicate
         * to the user that there is a potential performance impact due to
         * dynamic zone write plug allocation when simultaneously writing to
         * more zones than the size of the mempool.
         */
        pool_size = max(lim.max_open_zones, lim.max_active_zones);
        if (!pool_size)
                pool_size = min(BLK_ZONE_WPLUG_DEFAULT_POOL_SIZE, nr_seq_zones);

        mempool_resize(disk->zone_wplugs_pool, pool_size);

        if (!lim.max_open_zones && !lim.max_active_zones) {
                if (pool_size < nr_seq_zones)
                        lim.max_open_zones = pool_size;
                else
                        lim.max_open_zones = 0;
        }

commit:
        return queue_limits_commit_update(q, &lim);
}

static int blk_revalidate_conv_zone(struct blk_zone *zone, unsigned int idx,
                                    struct blk_revalidate_zone_args *args)
{
        struct gendisk *disk = args->disk;

        if (zone->capacity != zone->len) {
                pr_warn("%s: Invalid conventional zone capacity\n",
                        disk->disk_name);
                return -ENODEV;
        }

        if (disk_zone_is_last(disk, zone))
                args->last_zone_capacity = zone->capacity;

        if (!disk_need_zone_resources(disk))
                return 0;

        if (!args->conv_zones_bitmap) {
                args->conv_zones_bitmap =
                        bitmap_zalloc(args->nr_zones, GFP_NOIO);
                if (!args->conv_zones_bitmap)
                        return -ENOMEM;
        }

        set_bit(idx, args->conv_zones_bitmap);

        return 0;
}

static int blk_revalidate_seq_zone(struct blk_zone *zone, unsigned int idx,
                                   struct blk_revalidate_zone_args *args)
{
        struct gendisk *disk = args->disk;
        struct blk_zone_wplug *zwplug;
        unsigned int wp_offset;
        unsigned long flags;

        /*
         * Remember the capacity of the first sequential zone and check
         * if it is constant for all zones, ignoring the last zone as it can be
         * smaller.
         */
        if (!args->zone_capacity)
                args->zone_capacity = zone->capacity;
        if (disk_zone_is_last(disk, zone)) {
                args->last_zone_capacity = zone->capacity;
        } else if (zone->capacity != args->zone_capacity) {
                pr_warn("%s: Invalid variable zone capacity\n",
                        disk->disk_name);
                return -ENODEV;
        }

        /*
         * We need to track the write pointer of all zones that are not
         * empty nor full. So make sure we have a zone write plug for
         * such zone if the device has a zone write plug hash table.
         */
        if (!disk->zone_wplugs_hash)
                return 0;

        wp_offset = blk_zone_wp_offset(zone);
        if (!wp_offset || wp_offset >= zone->capacity)
                return 0;

        zwplug = disk_get_and_lock_zone_wplug(disk, zone->wp, GFP_NOIO, &flags);
        if (!zwplug)
                return -ENOMEM;
        spin_unlock_irqrestore(&zwplug->lock, flags);
        disk_put_zone_wplug(zwplug);

        return 0;
}

/*
 * Helper function to check the validity of zones of a zoned block device.
 */
static int blk_revalidate_zone_cb(struct blk_zone *zone, unsigned int idx,
                                  void *data)
{
        struct blk_revalidate_zone_args *args = data;
        struct gendisk *disk = args->disk;
        sector_t zone_sectors = disk->queue->limits.chunk_sectors;
        int ret;

        /* Check for bad zones and holes in the zone report */
        if (zone->start != args->sector) {
                pr_warn("%s: Zone gap at sectors %llu..%llu\n",
                        disk->disk_name, args->sector, zone->start);
                return -ENODEV;
        }

        if (zone->start >= get_capacity(disk) || !zone->len) {
                pr_warn("%s: Invalid zone start %llu, length %llu\n",
                        disk->disk_name, zone->start, zone->len);
                return -ENODEV;
        }

        /*
         * All zones must have the same size, with the exception on an eventual
         * smaller last zone.
         */
        if (!disk_zone_is_last(disk, zone)) {
                if (zone->len != zone_sectors) {
                        pr_warn("%s: Invalid zoned device with non constant zone size\n",
                                disk->disk_name);
                        return -ENODEV;
                }
        } else if (zone->len > zone_sectors) {
                pr_warn("%s: Invalid zoned device with larger last zone size\n",
                        disk->disk_name);
                return -ENODEV;
        }

        if (!zone->capacity || zone->capacity > zone->len) {
                pr_warn("%s: Invalid zone capacity\n",
                        disk->disk_name);
                return -ENODEV;
        }

        /* Check zone type */
        switch (zone->type) {
        case BLK_ZONE_TYPE_CONVENTIONAL:
                ret = blk_revalidate_conv_zone(zone, idx, args);
                break;
        case BLK_ZONE_TYPE_SEQWRITE_REQ:
                ret = blk_revalidate_seq_zone(zone, idx, args);
                break;
        case BLK_ZONE_TYPE_SEQWRITE_PREF:
        default:
                pr_warn("%s: Invalid zone type 0x%x at sectors %llu\n",
                        disk->disk_name, (int)zone->type, zone->start);
                ret = -ENODEV;
        }

        if (!ret)
                args->sector += zone->len;

        return ret;
}

/**
 * blk_revalidate_disk_zones - (re)allocate and initialize zone write plugs
 * @disk:       Target disk
 *
 * Helper function for low-level device drivers to check, (re) allocate and
 * initialize resources used for managing zoned disks. This function should
 * normally be called by blk-mq based drivers when a zoned gendisk is probed
 * and when the zone configuration of the gendisk changes (e.g. after a format).
 * Before calling this function, the device driver must already have set the
 * device zone size (chunk_sector limit) and the max zone append limit.
 * BIO based drivers can also use this function as long as the device queue
 * can be safely frozen.
 */
int blk_revalidate_disk_zones(struct gendisk *disk)
{
        struct request_queue *q = disk->queue;
        sector_t zone_sectors = q->limits.chunk_sectors;
        sector_t capacity = get_capacity(disk);
        struct blk_revalidate_zone_args args = { };
        unsigned int noio_flag;
        int ret = -ENOMEM;

        if (WARN_ON_ONCE(!blk_queue_is_zoned(q)))
                return -EIO;

        if (!capacity)
                return -ENODEV;

        /*
         * Checks that the device driver indicated a valid zone size and that
         * the max zone append limit is set.
         */
        if (!zone_sectors || !is_power_of_2(zone_sectors)) {
                pr_warn("%s: Invalid non power of two zone size (%llu)\n",
                        disk->disk_name, zone_sectors);
                return -ENODEV;
        }

        if (!queue_max_zone_append_sectors(q)) {
                pr_warn("%s: Invalid 0 maximum zone append limit\n",
                        disk->disk_name);
                return -ENODEV;
        }

        /*
         * Ensure that all memory allocations in this context are done as if
         * GFP_NOIO was specified.
         */
        args.disk = disk;
        args.nr_zones = (capacity + zone_sectors - 1) >> ilog2(zone_sectors);
        noio_flag = memalloc_noio_save();
        ret = disk_revalidate_zone_resources(disk, args.nr_zones);
        if (ret) {
                memalloc_noio_restore(noio_flag);
                return ret;
        }
        ret = disk->fops->report_zones(disk, 0, UINT_MAX,
                                       blk_revalidate_zone_cb, &args);
        if (!ret) {
                pr_warn("%s: No zones reported\n", disk->disk_name);
                ret = -ENODEV;
        }
        memalloc_noio_restore(noio_flag);

        /*
         * If zones where reported, make sure that the entire disk capacity
         * has been checked.
         */
        if (ret > 0 && args.sector != capacity) {
                pr_warn("%s: Missing zones from sector %llu\n",
                        disk->disk_name, args.sector);
                ret = -ENODEV;
        }

        /*
         * Set the new disk zone parameters only once the queue is frozen and
         * all I/Os are completed.
         */
        blk_mq_freeze_queue(q);
        if (ret > 0)
                ret = disk_update_zone_resources(disk, &args);
        else
                pr_warn("%s: failed to revalidate zones\n", disk->disk_name);
        if (ret)
                disk_free_zone_resources(disk);
        blk_mq_unfreeze_queue(q);

        kfree(args.conv_zones_bitmap);

        return ret;
}
EXPORT_SYMBOL_GPL(blk_revalidate_disk_zones);

#ifdef CONFIG_BLK_DEBUG_FS

int queue_zone_wplugs_show(void *data, struct seq_file *m)
{
        struct request_queue *q = data;
        struct gendisk *disk = q->disk;
        struct blk_zone_wplug *zwplug;
        unsigned int zwp_wp_offset, zwp_flags;
        unsigned int zwp_zone_no, zwp_ref;
        unsigned int zwp_bio_list_size, i;
        unsigned long flags;

        if (!disk->zone_wplugs_hash)
                return 0;

        rcu_read_lock();
        for (i = 0; i < disk_zone_wplugs_hash_size(disk); i++) {
                hlist_for_each_entry_rcu(zwplug,
                                         &disk->zone_wplugs_hash[i], node) {
                        spin_lock_irqsave(&zwplug->lock, flags);
                        zwp_zone_no = zwplug->zone_no;
                        zwp_flags = zwplug->flags;
                        zwp_ref = atomic_read(&zwplug->ref);
                        zwp_wp_offset = zwplug->wp_offset;
                        zwp_bio_list_size = bio_list_size(&zwplug->bio_list);
                        spin_unlock_irqrestore(&zwplug->lock, flags);

                        seq_printf(m, "%u 0x%x %u %u %u\n",
                                   zwp_zone_no, zwp_flags, zwp_ref,
                                   zwp_wp_offset, zwp_bio_list_size);
                }
        }
        rcu_read_unlock();

        return 0;
}

#endif