null_blk: remove unused nullb device

[thirdparty/kernel/linux.git] / drivers / block / null_blk_main.c

/*
 * Add configfs and memory store: Kyungchan Koh <kkc6196@fb.com> and
 * Shaohua Li <shli@fb.com>
 */
#include <linux/module.h>

#include <linux/moduleparam.h>
#include <linux/sched.h>
#include <linux/fs.h>
#include <linux/init.h>
#include "null_blk.h"

#define PAGE_SECTORS_SHIFT      (PAGE_SHIFT - SECTOR_SHIFT)
#define PAGE_SECTORS            (1 << PAGE_SECTORS_SHIFT)
#define SECTOR_MASK             (PAGE_SECTORS - 1)

#define FREE_BATCH              16

#define TICKS_PER_SEC           50ULL
#define TIMER_INTERVAL          (NSEC_PER_SEC / TICKS_PER_SEC)

#ifdef CONFIG_BLK_DEV_NULL_BLK_FAULT_INJECTION
static DECLARE_FAULT_ATTR(null_timeout_attr);
static DECLARE_FAULT_ATTR(null_requeue_attr);
#endif

static inline u64 mb_per_tick(int mbps)
{
        return (1 << 20) / TICKS_PER_SEC * ((u64) mbps);
}

/*
 * Status flags for nullb_device.
 *
 * CONFIGURED:  Device has been configured and turned on. Cannot reconfigure.
 * UP:          Device is currently on and visible in userspace.
 * THROTTLED:   Device is being throttled.
 * CACHE:       Device is using a write-back cache.
 */
enum nullb_device_flags {
        NULLB_DEV_FL_CONFIGURED = 0,
        NULLB_DEV_FL_UP         = 1,
        NULLB_DEV_FL_THROTTLED  = 2,
        NULLB_DEV_FL_CACHE      = 3,
};

#define MAP_SZ          ((PAGE_SIZE >> SECTOR_SHIFT) + 2)
/*
 * nullb_page is a page in memory for nullb devices.
 *
 * @page:       The page holding the data.
 * @bitmap:     The bitmap represents which sector in the page has data.
 *              Each bit represents one block size. For example, sector 8
 *              will use the 7th bit
 * The highest 2 bits of bitmap are for special purpose. LOCK means the cache
 * page is being flushing to storage. FREE means the cache page is freed and
 * should be skipped from flushing to storage. Please see
 * null_make_cache_space
 */
struct nullb_page {
        struct page *page;
        DECLARE_BITMAP(bitmap, MAP_SZ);
};
#define NULLB_PAGE_LOCK (MAP_SZ - 1)
#define NULLB_PAGE_FREE (MAP_SZ - 2)

static LIST_HEAD(nullb_list);
static struct mutex lock;
static int null_major;
static DEFINE_IDA(nullb_indexes);
static struct blk_mq_tag_set tag_set;

enum {
        NULL_IRQ_NONE           = 0,
        NULL_IRQ_SOFTIRQ        = 1,
        NULL_IRQ_TIMER          = 2,
};

enum {
        NULL_Q_BIO              = 0,
        NULL_Q_RQ               = 1,
        NULL_Q_MQ               = 2,
};

static int g_no_sched;
module_param_named(no_sched, g_no_sched, int, 0444);
MODULE_PARM_DESC(no_sched, "No io scheduler");

static int g_submit_queues = 1;
module_param_named(submit_queues, g_submit_queues, int, 0444);
MODULE_PARM_DESC(submit_queues, "Number of submission queues");

static int g_home_node = NUMA_NO_NODE;
module_param_named(home_node, g_home_node, int, 0444);
MODULE_PARM_DESC(home_node, "Home node for the device");

#ifdef CONFIG_BLK_DEV_NULL_BLK_FAULT_INJECTION
static char g_timeout_str[80];
module_param_string(timeout, g_timeout_str, sizeof(g_timeout_str), 0444);

static char g_requeue_str[80];
module_param_string(requeue, g_requeue_str, sizeof(g_requeue_str), 0444);
#endif

static int g_queue_mode = NULL_Q_MQ;

static int null_param_store_val(const char *str, int *val, int min, int max)
{
        int ret, new_val;

        ret = kstrtoint(str, 10, &new_val);
        if (ret)
                return -EINVAL;

        if (new_val < min || new_val > max)
                return -EINVAL;

        *val = new_val;
        return 0;
}

static int null_set_queue_mode(const char *str, const struct kernel_param *kp)
{
        return null_param_store_val(str, &g_queue_mode, NULL_Q_BIO, NULL_Q_MQ);
}

static const struct kernel_param_ops null_queue_mode_param_ops = {
        .set    = null_set_queue_mode,
        .get    = param_get_int,
};

device_param_cb(queue_mode, &null_queue_mode_param_ops, &g_queue_mode, 0444);
MODULE_PARM_DESC(queue_mode, "Block interface to use (0=bio,1=rq,2=multiqueue)");

static int g_gb = 250;
module_param_named(gb, g_gb, int, 0444);
MODULE_PARM_DESC(gb, "Size in GB");

static int g_bs = 512;
module_param_named(bs, g_bs, int, 0444);
MODULE_PARM_DESC(bs, "Block size (in bytes)");

static int nr_devices = 1;
module_param(nr_devices, int, 0444);
MODULE_PARM_DESC(nr_devices, "Number of devices to register");

static bool g_blocking;
module_param_named(blocking, g_blocking, bool, 0444);
MODULE_PARM_DESC(blocking, "Register as a blocking blk-mq driver device");

static bool shared_tags;
module_param(shared_tags, bool, 0444);
MODULE_PARM_DESC(shared_tags, "Share tag set between devices for blk-mq");

static int g_irqmode = NULL_IRQ_SOFTIRQ;

static int null_set_irqmode(const char *str, const struct kernel_param *kp)
{
        return null_param_store_val(str, &g_irqmode, NULL_IRQ_NONE,
                                        NULL_IRQ_TIMER);
}

static const struct kernel_param_ops null_irqmode_param_ops = {
        .set    = null_set_irqmode,
        .get    = param_get_int,
};

device_param_cb(irqmode, &null_irqmode_param_ops, &g_irqmode, 0444);
MODULE_PARM_DESC(irqmode, "IRQ completion handler. 0-none, 1-softirq, 2-timer");

static unsigned long g_completion_nsec = 10000;
module_param_named(completion_nsec, g_completion_nsec, ulong, 0444);
MODULE_PARM_DESC(completion_nsec, "Time in ns to complete a request in hardware. Default: 10,000ns");

static int g_hw_queue_depth = 64;
module_param_named(hw_queue_depth, g_hw_queue_depth, int, 0444);
MODULE_PARM_DESC(hw_queue_depth, "Queue depth for each hardware queue. Default: 64");

static bool g_use_per_node_hctx;
module_param_named(use_per_node_hctx, g_use_per_node_hctx, bool, 0444);
MODULE_PARM_DESC(use_per_node_hctx, "Use per-node allocation for hardware context queues. Default: false");

static bool g_zoned;
module_param_named(zoned, g_zoned, bool, S_IRUGO);
MODULE_PARM_DESC(zoned, "Make device as a host-managed zoned block device. Default: false");

static unsigned long g_zone_size = 256;
module_param_named(zone_size, g_zone_size, ulong, S_IRUGO);
MODULE_PARM_DESC(zone_size, "Zone size in MB when block device is zoned. Must be power-of-two: Default: 256");

static unsigned int g_zone_nr_conv;
module_param_named(zone_nr_conv, g_zone_nr_conv, uint, 0444);
MODULE_PARM_DESC(zone_nr_conv, "Number of conventional zones when block device is zoned. Default: 0");

static struct nullb_device *null_alloc_dev(void);
static void null_free_dev(struct nullb_device *dev);
static void null_del_dev(struct nullb *nullb);
static int null_add_dev(struct nullb_device *dev);
static void null_free_device_storage(struct nullb_device *dev, bool is_cache);

static inline struct nullb_device *to_nullb_device(struct config_item *item)
{
        return item ? container_of(item, struct nullb_device, item) : NULL;
}

static inline ssize_t nullb_device_uint_attr_show(unsigned int val, char *page)
{
        return snprintf(page, PAGE_SIZE, "%u\n", val);
}

static inline ssize_t nullb_device_ulong_attr_show(unsigned long val,
        char *page)
{
        return snprintf(page, PAGE_SIZE, "%lu\n", val);
}

static inline ssize_t nullb_device_bool_attr_show(bool val, char *page)
{
        return snprintf(page, PAGE_SIZE, "%u\n", val);
}

static ssize_t nullb_device_uint_attr_store(unsigned int *val,
        const char *page, size_t count)
{
        unsigned int tmp;
        int result;

        result = kstrtouint(page, 0, &tmp);
        if (result)
                return result;

        *val = tmp;
        return count;
}

static ssize_t nullb_device_ulong_attr_store(unsigned long *val,
        const char *page, size_t count)
{
        int result;
        unsigned long tmp;

        result = kstrtoul(page, 0, &tmp);
        if (result)
                return result;

        *val = tmp;
        return count;
}

static ssize_t nullb_device_bool_attr_store(bool *val, const char *page,
        size_t count)
{
        bool tmp;
        int result;

        result = kstrtobool(page,  &tmp);
        if (result)
                return result;

        *val = tmp;
        return count;
}

/* The following macro should only be used with TYPE = {uint, ulong, bool}. */
#define NULLB_DEVICE_ATTR(NAME, TYPE)                                           \
static ssize_t                                                                  \
nullb_device_##NAME##_show(struct config_item *item, char *page)                \
{                                                                               \
        return nullb_device_##TYPE##_attr_show(                                 \
                                to_nullb_device(item)->NAME, page);             \
}                                                                               \
static ssize_t                                                                  \
nullb_device_##NAME##_store(struct config_item *item, const char *page,         \
                            size_t count)                                       \
{                                                                               \
        if (test_bit(NULLB_DEV_FL_CONFIGURED, &to_nullb_device(item)->flags))   \
                return -EBUSY;                                                  \
        return nullb_device_##TYPE##_attr_store(                                \
                        &to_nullb_device(item)->NAME, page, count);             \
}                                                                               \
CONFIGFS_ATTR(nullb_device_, NAME);

NULLB_DEVICE_ATTR(size, ulong);
NULLB_DEVICE_ATTR(completion_nsec, ulong);
NULLB_DEVICE_ATTR(submit_queues, uint);
NULLB_DEVICE_ATTR(home_node, uint);
NULLB_DEVICE_ATTR(queue_mode, uint);
NULLB_DEVICE_ATTR(blocksize, uint);
NULLB_DEVICE_ATTR(irqmode, uint);
NULLB_DEVICE_ATTR(hw_queue_depth, uint);
NULLB_DEVICE_ATTR(index, uint);
NULLB_DEVICE_ATTR(blocking, bool);
NULLB_DEVICE_ATTR(use_per_node_hctx, bool);
NULLB_DEVICE_ATTR(memory_backed, bool);
NULLB_DEVICE_ATTR(discard, bool);
NULLB_DEVICE_ATTR(mbps, uint);
NULLB_DEVICE_ATTR(cache_size, ulong);
NULLB_DEVICE_ATTR(zoned, bool);
NULLB_DEVICE_ATTR(zone_size, ulong);
NULLB_DEVICE_ATTR(zone_nr_conv, uint);

static ssize_t nullb_device_power_show(struct config_item *item, char *page)
{
        return nullb_device_bool_attr_show(to_nullb_device(item)->power, page);
}

static ssize_t nullb_device_power_store(struct config_item *item,
                                     const char *page, size_t count)
{
        struct nullb_device *dev = to_nullb_device(item);
        bool newp = false;
        ssize_t ret;

        ret = nullb_device_bool_attr_store(&newp, page, count);
        if (ret < 0)
                return ret;

        if (!dev->power && newp) {
                if (test_and_set_bit(NULLB_DEV_FL_UP, &dev->flags))
                        return count;
                if (null_add_dev(dev)) {
                        clear_bit(NULLB_DEV_FL_UP, &dev->flags);
                        return -ENOMEM;
                }

                set_bit(NULLB_DEV_FL_CONFIGURED, &dev->flags);
                dev->power = newp;
        } else if (dev->power && !newp) {
                mutex_lock(&lock);
                dev->power = newp;
                null_del_dev(dev->nullb);
                mutex_unlock(&lock);
                clear_bit(NULLB_DEV_FL_UP, &dev->flags);
                clear_bit(NULLB_DEV_FL_CONFIGURED, &dev->flags);
        }

        return count;
}

CONFIGFS_ATTR(nullb_device_, power);

static ssize_t nullb_device_badblocks_show(struct config_item *item, char *page)
{
        struct nullb_device *t_dev = to_nullb_device(item);

        return badblocks_show(&t_dev->badblocks, page, 0);
}

static ssize_t nullb_device_badblocks_store(struct config_item *item,
                                     const char *page, size_t count)
{
        struct nullb_device *t_dev = to_nullb_device(item);
        char *orig, *buf, *tmp;
        u64 start, end;
        int ret;

        orig = kstrndup(page, count, GFP_KERNEL);
        if (!orig)
                return -ENOMEM;

        buf = strstrip(orig);

        ret = -EINVAL;
        if (buf[0] != '+' && buf[0] != '-')
                goto out;
        tmp = strchr(&buf[1], '-');
        if (!tmp)
                goto out;
        *tmp = '\0';
        ret = kstrtoull(buf + 1, 0, &start);
        if (ret)
                goto out;
        ret = kstrtoull(tmp + 1, 0, &end);
        if (ret)
                goto out;
        ret = -EINVAL;
        if (start > end)
                goto out;
        /* enable badblocks */
        cmpxchg(&t_dev->badblocks.shift, -1, 0);
        if (buf[0] == '+')
                ret = badblocks_set(&t_dev->badblocks, start,
                        end - start + 1, 1);
        else
                ret = badblocks_clear(&t_dev->badblocks, start,
                        end - start + 1);
        if (ret == 0)
                ret = count;
out:
        kfree(orig);
        return ret;
}
CONFIGFS_ATTR(nullb_device_, badblocks);

static struct configfs_attribute *nullb_device_attrs[] = {
        &nullb_device_attr_size,
        &nullb_device_attr_completion_nsec,
        &nullb_device_attr_submit_queues,
        &nullb_device_attr_home_node,
        &nullb_device_attr_queue_mode,
        &nullb_device_attr_blocksize,
        &nullb_device_attr_irqmode,
        &nullb_device_attr_hw_queue_depth,
        &nullb_device_attr_index,
        &nullb_device_attr_blocking,
        &nullb_device_attr_use_per_node_hctx,
        &nullb_device_attr_power,
        &nullb_device_attr_memory_backed,
        &nullb_device_attr_discard,
        &nullb_device_attr_mbps,
        &nullb_device_attr_cache_size,
        &nullb_device_attr_badblocks,
        &nullb_device_attr_zoned,
        &nullb_device_attr_zone_size,
        &nullb_device_attr_zone_nr_conv,
        NULL,
};

static void nullb_device_release(struct config_item *item)
{
        struct nullb_device *dev = to_nullb_device(item);

        null_free_device_storage(dev, false);
        null_free_dev(dev);
}

static struct configfs_item_operations nullb_device_ops = {
        .release        = nullb_device_release,
};

static const struct config_item_type nullb_device_type = {
        .ct_item_ops    = &nullb_device_ops,
        .ct_attrs       = nullb_device_attrs,
        .ct_owner       = THIS_MODULE,
};

static struct
config_item *nullb_group_make_item(struct config_group *group, const char *name)
{
        struct nullb_device *dev;

        dev = null_alloc_dev();
        if (!dev)
                return ERR_PTR(-ENOMEM);

        config_item_init_type_name(&dev->item, name, &nullb_device_type);

        return &dev->item;
}

static void
nullb_group_drop_item(struct config_group *group, struct config_item *item)
{
        struct nullb_device *dev = to_nullb_device(item);

        if (test_and_clear_bit(NULLB_DEV_FL_UP, &dev->flags)) {
                mutex_lock(&lock);
                dev->power = false;
                null_del_dev(dev->nullb);
                mutex_unlock(&lock);
        }

        config_item_put(item);
}

static ssize_t memb_group_features_show(struct config_item *item, char *page)
{
        return snprintf(page, PAGE_SIZE, "memory_backed,discard,bandwidth,cache,badblocks,zoned,zone_size\n");
}

CONFIGFS_ATTR_RO(memb_group_, features);

static struct configfs_attribute *nullb_group_attrs[] = {
        &memb_group_attr_features,
        NULL,
};

static struct configfs_group_operations nullb_group_ops = {
        .make_item      = nullb_group_make_item,
        .drop_item      = nullb_group_drop_item,
};

static const struct config_item_type nullb_group_type = {
        .ct_group_ops   = &nullb_group_ops,
        .ct_attrs       = nullb_group_attrs,
        .ct_owner       = THIS_MODULE,
};

static struct configfs_subsystem nullb_subsys = {
        .su_group = {
                .cg_item = {
                        .ci_namebuf = "nullb",
                        .ci_type = &nullb_group_type,
                },
        },
};

static inline int null_cache_active(struct nullb *nullb)
{
        return test_bit(NULLB_DEV_FL_CACHE, &nullb->dev->flags);
}

static struct nullb_device *null_alloc_dev(void)
{
        struct nullb_device *dev;

        dev = kzalloc(sizeof(*dev), GFP_KERNEL);
        if (!dev)
                return NULL;
        INIT_RADIX_TREE(&dev->data, GFP_ATOMIC);
        INIT_RADIX_TREE(&dev->cache, GFP_ATOMIC);
        if (badblocks_init(&dev->badblocks, 0)) {
                kfree(dev);
                return NULL;
        }

        dev->size = g_gb * 1024;
        dev->completion_nsec = g_completion_nsec;
        dev->submit_queues = g_submit_queues;
        dev->home_node = g_home_node;
        dev->queue_mode = g_queue_mode;
        dev->blocksize = g_bs;
        dev->irqmode = g_irqmode;
        dev->hw_queue_depth = g_hw_queue_depth;
        dev->blocking = g_blocking;
        dev->use_per_node_hctx = g_use_per_node_hctx;
        dev->zoned = g_zoned;
        dev->zone_size = g_zone_size;
        dev->zone_nr_conv = g_zone_nr_conv;
        return dev;
}

static void null_free_dev(struct nullb_device *dev)
{
        if (!dev)
                return;

        null_zone_exit(dev);
        badblocks_exit(&dev->badblocks);
        kfree(dev);
}

static void put_tag(struct nullb_queue *nq, unsigned int tag)
{
        clear_bit_unlock(tag, nq->tag_map);

        if (waitqueue_active(&nq->wait))
                wake_up(&nq->wait);
}

static unsigned int get_tag(struct nullb_queue *nq)
{
        unsigned int tag;

        do {
                tag = find_first_zero_bit(nq->tag_map, nq->queue_depth);
                if (tag >= nq->queue_depth)
                        return -1U;
        } while (test_and_set_bit_lock(tag, nq->tag_map));

        return tag;
}

static void free_cmd(struct nullb_cmd *cmd)
{
        put_tag(cmd->nq, cmd->tag);
}

static enum hrtimer_restart null_cmd_timer_expired(struct hrtimer *timer);

static struct nullb_cmd *__alloc_cmd(struct nullb_queue *nq)
{
        struct nullb_cmd *cmd;
        unsigned int tag;

        tag = get_tag(nq);
        if (tag != -1U) {
                cmd = &nq->cmds[tag];
                cmd->tag = tag;
                cmd->nq = nq;
                if (nq->dev->irqmode == NULL_IRQ_TIMER) {
                        hrtimer_init(&cmd->timer, CLOCK_MONOTONIC,
                                     HRTIMER_MODE_REL);
                        cmd->timer.function = null_cmd_timer_expired;
                }
                return cmd;
        }

        return NULL;
}

static struct nullb_cmd *alloc_cmd(struct nullb_queue *nq, int can_wait)
{
        struct nullb_cmd *cmd;
        DEFINE_WAIT(wait);

        cmd = __alloc_cmd(nq);
        if (cmd || !can_wait)
                return cmd;

        do {
                prepare_to_wait(&nq->wait, &wait, TASK_UNINTERRUPTIBLE);
                cmd = __alloc_cmd(nq);
                if (cmd)
                        break;

                io_schedule();
        } while (1);

        finish_wait(&nq->wait, &wait);
        return cmd;
}

static void end_cmd(struct nullb_cmd *cmd)
{
        int queue_mode = cmd->nq->dev->queue_mode;

        switch (queue_mode)  {
        case NULL_Q_MQ:
                blk_mq_end_request(cmd->rq, cmd->error);
                return;
        case NULL_Q_BIO:
                cmd->bio->bi_status = cmd->error;
                bio_endio(cmd->bio);
                break;
        }

        free_cmd(cmd);
}

static enum hrtimer_restart null_cmd_timer_expired(struct hrtimer *timer)
{
        end_cmd(container_of(timer, struct nullb_cmd, timer));

        return HRTIMER_NORESTART;
}

static void null_cmd_end_timer(struct nullb_cmd *cmd)
{
        ktime_t kt = cmd->nq->dev->completion_nsec;

        hrtimer_start(&cmd->timer, kt, HRTIMER_MODE_REL);
}

static void null_complete_rq(struct request *rq)
{
        end_cmd(blk_mq_rq_to_pdu(rq));
}

static struct nullb_page *null_alloc_page(gfp_t gfp_flags)
{
        struct nullb_page *t_page;

        t_page = kmalloc(sizeof(struct nullb_page), gfp_flags);
        if (!t_page)
                goto out;

        t_page->page = alloc_pages(gfp_flags, 0);
        if (!t_page->page)
                goto out_freepage;

        memset(t_page->bitmap, 0, sizeof(t_page->bitmap));
        return t_page;
out_freepage:
        kfree(t_page);
out:
        return NULL;
}

static void null_free_page(struct nullb_page *t_page)
{
        __set_bit(NULLB_PAGE_FREE, t_page->bitmap);
        if (test_bit(NULLB_PAGE_LOCK, t_page->bitmap))
                return;
        __free_page(t_page->page);
        kfree(t_page);
}

static bool null_page_empty(struct nullb_page *page)
{
        int size = MAP_SZ - 2;

        return find_first_bit(page->bitmap, size) == size;
}

static void null_free_sector(struct nullb *nullb, sector_t sector,
        bool is_cache)
{
        unsigned int sector_bit;
        u64 idx;
        struct nullb_page *t_page, *ret;
        struct radix_tree_root *root;

        root = is_cache ? &nullb->dev->cache : &nullb->dev->data;
        idx = sector >> PAGE_SECTORS_SHIFT;
        sector_bit = (sector & SECTOR_MASK);

        t_page = radix_tree_lookup(root, idx);
        if (t_page) {
                __clear_bit(sector_bit, t_page->bitmap);

                if (null_page_empty(t_page)) {
                        ret = radix_tree_delete_item(root, idx, t_page);
                        WARN_ON(ret != t_page);
                        null_free_page(ret);
                        if (is_cache)
                                nullb->dev->curr_cache -= PAGE_SIZE;
                }
        }
}

static struct nullb_page *null_radix_tree_insert(struct nullb *nullb, u64 idx,
        struct nullb_page *t_page, bool is_cache)
{
        struct radix_tree_root *root;

        root = is_cache ? &nullb->dev->cache : &nullb->dev->data;

        if (radix_tree_insert(root, idx, t_page)) {
                null_free_page(t_page);
                t_page = radix_tree_lookup(root, idx);
                WARN_ON(!t_page || t_page->page->index != idx);
        } else if (is_cache)
                nullb->dev->curr_cache += PAGE_SIZE;

        return t_page;
}

static void null_free_device_storage(struct nullb_device *dev, bool is_cache)
{
        unsigned long pos = 0;
        int nr_pages;
        struct nullb_page *ret, *t_pages[FREE_BATCH];
        struct radix_tree_root *root;

        root = is_cache ? &dev->cache : &dev->data;

        do {
                int i;

                nr_pages = radix_tree_gang_lookup(root,
                                (void **)t_pages, pos, FREE_BATCH);

                for (i = 0; i < nr_pages; i++) {
                        pos = t_pages[i]->page->index;
                        ret = radix_tree_delete_item(root, pos, t_pages[i]);
                        WARN_ON(ret != t_pages[i]);
                        null_free_page(ret);
                }

                pos++;
        } while (nr_pages == FREE_BATCH);

        if (is_cache)
                dev->curr_cache = 0;
}

static struct nullb_page *__null_lookup_page(struct nullb *nullb,
        sector_t sector, bool for_write, bool is_cache)
{
        unsigned int sector_bit;
        u64 idx;
        struct nullb_page *t_page;
        struct radix_tree_root *root;

        idx = sector >> PAGE_SECTORS_SHIFT;
        sector_bit = (sector & SECTOR_MASK);

        root = is_cache ? &nullb->dev->cache : &nullb->dev->data;
        t_page = radix_tree_lookup(root, idx);
        WARN_ON(t_page && t_page->page->index != idx);

        if (t_page && (for_write || test_bit(sector_bit, t_page->bitmap)))
                return t_page;

        return NULL;
}

static struct nullb_page *null_lookup_page(struct nullb *nullb,
        sector_t sector, bool for_write, bool ignore_cache)
{
        struct nullb_page *page = NULL;

        if (!ignore_cache)
                page = __null_lookup_page(nullb, sector, for_write, true);
        if (page)
                return page;
        return __null_lookup_page(nullb, sector, for_write, false);
}

static struct nullb_page *null_insert_page(struct nullb *nullb,
                                           sector_t sector, bool ignore_cache)
        __releases(&nullb->lock)
        __acquires(&nullb->lock)
{
        u64 idx;
        struct nullb_page *t_page;

        t_page = null_lookup_page(nullb, sector, true, ignore_cache);
        if (t_page)
                return t_page;

        spin_unlock_irq(&nullb->lock);

        t_page = null_alloc_page(GFP_NOIO);
        if (!t_page)
                goto out_lock;

        if (radix_tree_preload(GFP_NOIO))
                goto out_freepage;

        spin_lock_irq(&nullb->lock);
        idx = sector >> PAGE_SECTORS_SHIFT;
        t_page->page->index = idx;
        t_page = null_radix_tree_insert(nullb, idx, t_page, !ignore_cache);
        radix_tree_preload_end();

        return t_page;
out_freepage:
        null_free_page(t_page);
out_lock:
        spin_lock_irq(&nullb->lock);
        return null_lookup_page(nullb, sector, true, ignore_cache);
}

static int null_flush_cache_page(struct nullb *nullb, struct nullb_page *c_page)
{
        int i;
        unsigned int offset;
        u64 idx;
        struct nullb_page *t_page, *ret;
        void *dst, *src;

        idx = c_page->page->index;

        t_page = null_insert_page(nullb, idx << PAGE_SECTORS_SHIFT, true);

        __clear_bit(NULLB_PAGE_LOCK, c_page->bitmap);
        if (test_bit(NULLB_PAGE_FREE, c_page->bitmap)) {
                null_free_page(c_page);
                if (t_page && null_page_empty(t_page)) {
                        ret = radix_tree_delete_item(&nullb->dev->data,
                                idx, t_page);
                        null_free_page(t_page);
                }
                return 0;
        }

        if (!t_page)
                return -ENOMEM;

        src = kmap_atomic(c_page->page);
        dst = kmap_atomic(t_page->page);

        for (i = 0; i < PAGE_SECTORS;
                        i += (nullb->dev->blocksize >> SECTOR_SHIFT)) {
                if (test_bit(i, c_page->bitmap)) {
                        offset = (i << SECTOR_SHIFT);
                        memcpy(dst + offset, src + offset,
                                nullb->dev->blocksize);
                        __set_bit(i, t_page->bitmap);
                }
        }

        kunmap_atomic(dst);
        kunmap_atomic(src);

        ret = radix_tree_delete_item(&nullb->dev->cache, idx, c_page);
        null_free_page(ret);
        nullb->dev->curr_cache -= PAGE_SIZE;

        return 0;
}

static int null_make_cache_space(struct nullb *nullb, unsigned long n)
{
        int i, err, nr_pages;
        struct nullb_page *c_pages[FREE_BATCH];
        unsigned long flushed = 0, one_round;

again:
        if ((nullb->dev->cache_size * 1024 * 1024) >
             nullb->dev->curr_cache + n || nullb->dev->curr_cache == 0)
                return 0;

        nr_pages = radix_tree_gang_lookup(&nullb->dev->cache,
                        (void **)c_pages, nullb->cache_flush_pos, FREE_BATCH);
        /*
         * nullb_flush_cache_page could unlock before using the c_pages. To
         * avoid race, we don't allow page free
         */
        for (i = 0; i < nr_pages; i++) {
                nullb->cache_flush_pos = c_pages[i]->page->index;
                /*
                 * We found the page which is being flushed to disk by other
                 * threads
                 */
                if (test_bit(NULLB_PAGE_LOCK, c_pages[i]->bitmap))
                        c_pages[i] = NULL;
                else
                        __set_bit(NULLB_PAGE_LOCK, c_pages[i]->bitmap);
        }

        one_round = 0;
        for (i = 0; i < nr_pages; i++) {
                if (c_pages[i] == NULL)
                        continue;
                err = null_flush_cache_page(nullb, c_pages[i]);
                if (err)
                        return err;
                one_round++;
        }
        flushed += one_round << PAGE_SHIFT;

        if (n > flushed) {
                if (nr_pages == 0)
                        nullb->cache_flush_pos = 0;
                if (one_round == 0) {
                        /* give other threads a chance */
                        spin_unlock_irq(&nullb->lock);
                        spin_lock_irq(&nullb->lock);
                }
                goto again;
        }
        return 0;
}

static int copy_to_nullb(struct nullb *nullb, struct page *source,
        unsigned int off, sector_t sector, size_t n, bool is_fua)
{
        size_t temp, count = 0;
        unsigned int offset;
        struct nullb_page *t_page;
        void *dst, *src;

        while (count < n) {
                temp = min_t(size_t, nullb->dev->blocksize, n - count);

                if (null_cache_active(nullb) && !is_fua)
                        null_make_cache_space(nullb, PAGE_SIZE);

                offset = (sector & SECTOR_MASK) << SECTOR_SHIFT;
                t_page = null_insert_page(nullb, sector,
                        !null_cache_active(nullb) || is_fua);
                if (!t_page)
                        return -ENOSPC;

                src = kmap_atomic(source);
                dst = kmap_atomic(t_page->page);
                memcpy(dst + offset, src + off + count, temp);
                kunmap_atomic(dst);
                kunmap_atomic(src);

                __set_bit(sector & SECTOR_MASK, t_page->bitmap);

                if (is_fua)
                        null_free_sector(nullb, sector, true);

                count += temp;
                sector += temp >> SECTOR_SHIFT;
        }
        return 0;
}

static int copy_from_nullb(struct nullb *nullb, struct page *dest,
        unsigned int off, sector_t sector, size_t n)
{
        size_t temp, count = 0;
        unsigned int offset;
        struct nullb_page *t_page;
        void *dst, *src;

        while (count < n) {
                temp = min_t(size_t, nullb->dev->blocksize, n - count);

                offset = (sector & SECTOR_MASK) << SECTOR_SHIFT;
                t_page = null_lookup_page(nullb, sector, false,
                        !null_cache_active(nullb));

                dst = kmap_atomic(dest);
                if (!t_page) {
                        memset(dst + off + count, 0, temp);
                        goto next;
                }
                src = kmap_atomic(t_page->page);
                memcpy(dst + off + count, src + offset, temp);
                kunmap_atomic(src);
next:
                kunmap_atomic(dst);

                count += temp;
                sector += temp >> SECTOR_SHIFT;
        }
        return 0;
}

static void null_handle_discard(struct nullb *nullb, sector_t sector, size_t n)
{
        size_t temp;

        spin_lock_irq(&nullb->lock);
        while (n > 0) {
                temp = min_t(size_t, n, nullb->dev->blocksize);
                null_free_sector(nullb, sector, false);
                if (null_cache_active(nullb))
                        null_free_sector(nullb, sector, true);
                sector += temp >> SECTOR_SHIFT;
                n -= temp;
        }
        spin_unlock_irq(&nullb->lock);
}

static int null_handle_flush(struct nullb *nullb)
{
        int err;

        if (!null_cache_active(nullb))
                return 0;

        spin_lock_irq(&nullb->lock);
        while (true) {
                err = null_make_cache_space(nullb,
                        nullb->dev->cache_size * 1024 * 1024);
                if (err || nullb->dev->curr_cache == 0)
                        break;
        }

        WARN_ON(!radix_tree_empty(&nullb->dev->cache));
        spin_unlock_irq(&nullb->lock);
        return err;
}

static int null_transfer(struct nullb *nullb, struct page *page,
        unsigned int len, unsigned int off, bool is_write, sector_t sector,
        bool is_fua)
{
        int err = 0;

        if (!is_write) {
                err = copy_from_nullb(nullb, page, off, sector, len);
                flush_dcache_page(page);
        } else {
                flush_dcache_page(page);
                err = copy_to_nullb(nullb, page, off, sector, len, is_fua);
        }

        return err;
}

static int null_handle_rq(struct nullb_cmd *cmd)
{
        struct request *rq = cmd->rq;
        struct nullb *nullb = cmd->nq->dev->nullb;
        int err;
        unsigned int len;
        sector_t sector;
        struct req_iterator iter;
        struct bio_vec bvec;

        sector = blk_rq_pos(rq);

        if (req_op(rq) == REQ_OP_DISCARD) {
                null_handle_discard(nullb, sector, blk_rq_bytes(rq));
                return 0;
        }

        spin_lock_irq(&nullb->lock);
        rq_for_each_segment(bvec, rq, iter) {
                len = bvec.bv_len;
                err = null_transfer(nullb, bvec.bv_page, len, bvec.bv_offset,
                                     op_is_write(req_op(rq)), sector,
                                     req_op(rq) & REQ_FUA);
                if (err) {
                        spin_unlock_irq(&nullb->lock);
                        return err;
                }
                sector += len >> SECTOR_SHIFT;
        }
        spin_unlock_irq(&nullb->lock);

        return 0;
}

static int null_handle_bio(struct nullb_cmd *cmd)
{
        struct bio *bio = cmd->bio;
        struct nullb *nullb = cmd->nq->dev->nullb;
        int err;
        unsigned int len;
        sector_t sector;
        struct bio_vec bvec;
        struct bvec_iter iter;

        sector = bio->bi_iter.bi_sector;

        if (bio_op(bio) == REQ_OP_DISCARD) {
                null_handle_discard(nullb, sector,
                        bio_sectors(bio) << SECTOR_SHIFT);
                return 0;
        }

        spin_lock_irq(&nullb->lock);
        bio_for_each_segment(bvec, bio, iter) {
                len = bvec.bv_len;
                err = null_transfer(nullb, bvec.bv_page, len, bvec.bv_offset,
                                     op_is_write(bio_op(bio)), sector,
                                     bio_op(bio) & REQ_FUA);
                if (err) {
                        spin_unlock_irq(&nullb->lock);
                        return err;
                }
                sector += len >> SECTOR_SHIFT;
        }
        spin_unlock_irq(&nullb->lock);
        return 0;
}

static void null_stop_queue(struct nullb *nullb)
{
        struct request_queue *q = nullb->q;

        if (nullb->dev->queue_mode == NULL_Q_MQ)
                blk_mq_stop_hw_queues(q);
}

static void null_restart_queue_async(struct nullb *nullb)
{
        struct request_queue *q = nullb->q;

        if (nullb->dev->queue_mode == NULL_Q_MQ)
                blk_mq_start_stopped_hw_queues(q, true);
}

static blk_status_t null_handle_cmd(struct nullb_cmd *cmd)
{
        struct nullb_device *dev = cmd->nq->dev;
        struct nullb *nullb = dev->nullb;
        int err = 0;

        if (test_bit(NULLB_DEV_FL_THROTTLED, &dev->flags)) {
                struct request *rq = cmd->rq;

                if (!hrtimer_active(&nullb->bw_timer))
                        hrtimer_restart(&nullb->bw_timer);

                if (atomic_long_sub_return(blk_rq_bytes(rq),
                                &nullb->cur_bytes) < 0) {
                        null_stop_queue(nullb);
                        /* race with timer */
                        if (atomic_long_read(&nullb->cur_bytes) > 0)
                                null_restart_queue_async(nullb);
                        /* requeue request */
                        return BLK_STS_DEV_RESOURCE;
                }
        }

        if (nullb->dev->badblocks.shift != -1) {
                int bad_sectors;
                sector_t sector, size, first_bad;
                bool is_flush = true;

                if (dev->queue_mode == NULL_Q_BIO &&
                                bio_op(cmd->bio) != REQ_OP_FLUSH) {
                        is_flush = false;
                        sector = cmd->bio->bi_iter.bi_sector;
                        size = bio_sectors(cmd->bio);
                }
                if (dev->queue_mode != NULL_Q_BIO &&
                                req_op(cmd->rq) != REQ_OP_FLUSH) {
                        is_flush = false;
                        sector = blk_rq_pos(cmd->rq);
                        size = blk_rq_sectors(cmd->rq);
                }
                if (!is_flush && badblocks_check(&nullb->dev->badblocks, sector,
                                size, &first_bad, &bad_sectors)) {
                        cmd->error = BLK_STS_IOERR;
                        goto out;
                }
        }

        if (dev->memory_backed) {
                if (dev->queue_mode == NULL_Q_BIO) {
                        if (bio_op(cmd->bio) == REQ_OP_FLUSH)
                                err = null_handle_flush(nullb);
                        else
                                err = null_handle_bio(cmd);
                } else {
                        if (req_op(cmd->rq) == REQ_OP_FLUSH)
                                err = null_handle_flush(nullb);
                        else
                                err = null_handle_rq(cmd);
                }
        }
        cmd->error = errno_to_blk_status(err);

        if (!cmd->error && dev->zoned) {
                sector_t sector;
                unsigned int nr_sectors;
                int op;

                if (dev->queue_mode == NULL_Q_BIO) {
                        op = bio_op(cmd->bio);
                        sector = cmd->bio->bi_iter.bi_sector;
                        nr_sectors = cmd->bio->bi_iter.bi_size >> 9;
                } else {
                        op = req_op(cmd->rq);
                        sector = blk_rq_pos(cmd->rq);
                        nr_sectors = blk_rq_sectors(cmd->rq);
                }

                if (op == REQ_OP_WRITE)
                        null_zone_write(cmd, sector, nr_sectors);
                else if (op == REQ_OP_ZONE_RESET)
                        null_zone_reset(cmd, sector);
        }
out:
        /* Complete IO by inline, softirq or timer */
        switch (dev->irqmode) {
        case NULL_IRQ_SOFTIRQ:
                switch (dev->queue_mode)  {
                case NULL_Q_MQ:
                        blk_mq_complete_request(cmd->rq);
                        break;
                case NULL_Q_BIO:
                        /*
                         * XXX: no proper submitting cpu information available.
                         */
                        end_cmd(cmd);
                        break;
                }
                break;
        case NULL_IRQ_NONE:
                end_cmd(cmd);
                break;
        case NULL_IRQ_TIMER:
                null_cmd_end_timer(cmd);
                break;
        }
        return BLK_STS_OK;
}

static enum hrtimer_restart nullb_bwtimer_fn(struct hrtimer *timer)
{
        struct nullb *nullb = container_of(timer, struct nullb, bw_timer);
        ktime_t timer_interval = ktime_set(0, TIMER_INTERVAL);
        unsigned int mbps = nullb->dev->mbps;

        if (atomic_long_read(&nullb->cur_bytes) == mb_per_tick(mbps))
                return HRTIMER_NORESTART;

        atomic_long_set(&nullb->cur_bytes, mb_per_tick(mbps));
        null_restart_queue_async(nullb);

        hrtimer_forward_now(&nullb->bw_timer, timer_interval);

        return HRTIMER_RESTART;
}

static void nullb_setup_bwtimer(struct nullb *nullb)
{
        ktime_t timer_interval = ktime_set(0, TIMER_INTERVAL);

        hrtimer_init(&nullb->bw_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
        nullb->bw_timer.function = nullb_bwtimer_fn;
        atomic_long_set(&nullb->cur_bytes, mb_per_tick(nullb->dev->mbps));
        hrtimer_start(&nullb->bw_timer, timer_interval, HRTIMER_MODE_REL);
}

static struct nullb_queue *nullb_to_queue(struct nullb *nullb)
{
        int index = 0;

        if (nullb->nr_queues != 1)
                index = raw_smp_processor_id() / ((nr_cpu_ids + nullb->nr_queues - 1) / nullb->nr_queues);

        return &nullb->queues[index];
}

static blk_qc_t null_queue_bio(struct request_queue *q, struct bio *bio)
{
        struct nullb *nullb = q->queuedata;
        struct nullb_queue *nq = nullb_to_queue(nullb);
        struct nullb_cmd *cmd;

        cmd = alloc_cmd(nq, 1);
        cmd->bio = bio;

        null_handle_cmd(cmd);
        return BLK_QC_T_NONE;
}

static bool should_timeout_request(struct request *rq)
{
#ifdef CONFIG_BLK_DEV_NULL_BLK_FAULT_INJECTION
        if (g_timeout_str[0])
                return should_fail(&null_timeout_attr, 1);
#endif
        return false;
}

static bool should_requeue_request(struct request *rq)
{
#ifdef CONFIG_BLK_DEV_NULL_BLK_FAULT_INJECTION
        if (g_requeue_str[0])
                return should_fail(&null_requeue_attr, 1);
#endif
        return false;
}

static enum blk_eh_timer_return null_timeout_rq(struct request *rq, bool res)
{
        pr_info("null: rq %p timed out\n", rq);
        blk_mq_complete_request(rq);
        return BLK_EH_DONE;
}

static blk_status_t null_queue_rq(struct blk_mq_hw_ctx *hctx,
                         const struct blk_mq_queue_data *bd)
{
        struct nullb_cmd *cmd = blk_mq_rq_to_pdu(bd->rq);
        struct nullb_queue *nq = hctx->driver_data;

        might_sleep_if(hctx->flags & BLK_MQ_F_BLOCKING);

        if (nq->dev->irqmode == NULL_IRQ_TIMER) {
                hrtimer_init(&cmd->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
                cmd->timer.function = null_cmd_timer_expired;
        }
        cmd->rq = bd->rq;
        cmd->nq = nq;

        blk_mq_start_request(bd->rq);

        if (should_requeue_request(bd->rq)) {
                /*
                 * Alternate between hitting the core BUSY path, and the
                 * driver driven requeue path
                 */
                nq->requeue_selection++;
                if (nq->requeue_selection & 1)
                        return BLK_STS_RESOURCE;
                else {
                        blk_mq_requeue_request(bd->rq, true);
                        return BLK_STS_OK;
                }
        }
        if (should_timeout_request(bd->rq))
                return BLK_STS_OK;

        return null_handle_cmd(cmd);
}

static const struct blk_mq_ops null_mq_ops = {
        .queue_rq       = null_queue_rq,
        .complete       = null_complete_rq,
        .timeout        = null_timeout_rq,
};

static void cleanup_queue(struct nullb_queue *nq)
{
        kfree(nq->tag_map);
        kfree(nq->cmds);
}

static void cleanup_queues(struct nullb *nullb)
{
        int i;

        for (i = 0; i < nullb->nr_queues; i++)
                cleanup_queue(&nullb->queues[i]);

        kfree(nullb->queues);
}

static void null_del_dev(struct nullb *nullb)
{
        struct nullb_device *dev = nullb->dev;

        ida_simple_remove(&nullb_indexes, nullb->index);

        list_del_init(&nullb->list);

        del_gendisk(nullb->disk);

        if (test_bit(NULLB_DEV_FL_THROTTLED, &nullb->dev->flags)) {
                hrtimer_cancel(&nullb->bw_timer);
                atomic_long_set(&nullb->cur_bytes, LONG_MAX);
                null_restart_queue_async(nullb);
        }

        blk_cleanup_queue(nullb->q);
        if (dev->queue_mode == NULL_Q_MQ &&
            nullb->tag_set == &nullb->__tag_set)
                blk_mq_free_tag_set(nullb->tag_set);
        put_disk(nullb->disk);
        cleanup_queues(nullb);
        if (null_cache_active(nullb))
                null_free_device_storage(nullb->dev, true);
        kfree(nullb);
        dev->nullb = NULL;
}

static void null_config_discard(struct nullb *nullb)
{
        if (nullb->dev->discard == false)
                return;
        nullb->q->limits.discard_granularity = nullb->dev->blocksize;
        nullb->q->limits.discard_alignment = nullb->dev->blocksize;
        blk_queue_max_discard_sectors(nullb->q, UINT_MAX >> 9);
        blk_queue_flag_set(QUEUE_FLAG_DISCARD, nullb->q);
}

static int null_open(struct block_device *bdev, fmode_t mode)
{
        return 0;
}

static void null_release(struct gendisk *disk, fmode_t mode)
{
}

static const struct block_device_operations null_fops = {
        .owner =        THIS_MODULE,
        .open =         null_open,
        .release =      null_release,
        .report_zones = null_zone_report,
};

static void null_init_queue(struct nullb *nullb, struct nullb_queue *nq)
{
        BUG_ON(!nullb);
        BUG_ON(!nq);

        init_waitqueue_head(&nq->wait);
        nq->queue_depth = nullb->queue_depth;
        nq->dev = nullb->dev;
}

static void null_init_queues(struct nullb *nullb)
{
        struct request_queue *q = nullb->q;
        struct blk_mq_hw_ctx *hctx;
        struct nullb_queue *nq;
        int i;

        queue_for_each_hw_ctx(q, hctx, i) {
                if (!hctx->nr_ctx || !hctx->tags)
                        continue;
                nq = &nullb->queues[i];
                hctx->driver_data = nq;
                null_init_queue(nullb, nq);
                nullb->nr_queues++;
        }
}

static int setup_commands(struct nullb_queue *nq)
{
        struct nullb_cmd *cmd;
        int i, tag_size;

        nq->cmds = kcalloc(nq->queue_depth, sizeof(*cmd), GFP_KERNEL);
        if (!nq->cmds)
                return -ENOMEM;

        tag_size = ALIGN(nq->queue_depth, BITS_PER_LONG) / BITS_PER_LONG;
        nq->tag_map = kcalloc(tag_size, sizeof(unsigned long), GFP_KERNEL);
        if (!nq->tag_map) {
                kfree(nq->cmds);
                return -ENOMEM;
        }

        for (i = 0; i < nq->queue_depth; i++) {
                cmd = &nq->cmds[i];
                INIT_LIST_HEAD(&cmd->list);
                cmd->ll_list.next = NULL;
                cmd->tag = -1U;
        }

        return 0;
}

static int setup_queues(struct nullb *nullb)
{
        nullb->queues = kcalloc(nullb->dev->submit_queues,
                                sizeof(struct nullb_queue),
                                GFP_KERNEL);
        if (!nullb->queues)
                return -ENOMEM;

        nullb->nr_queues = 0;
        nullb->queue_depth = nullb->dev->hw_queue_depth;

        return 0;
}

static int init_driver_queues(struct nullb *nullb)
{
        struct nullb_queue *nq;
        int i, ret = 0;

        for (i = 0; i < nullb->dev->submit_queues; i++) {
                nq = &nullb->queues[i];

                null_init_queue(nullb, nq);

                ret = setup_commands(nq);
                if (ret)
                        return ret;
                nullb->nr_queues++;
        }
        return 0;
}

static int null_gendisk_register(struct nullb *nullb)
{
        struct gendisk *disk;
        sector_t size;

        disk = nullb->disk = alloc_disk_node(1, nullb->dev->home_node);
        if (!disk)
                return -ENOMEM;
        size = (sector_t)nullb->dev->size * 1024 * 1024ULL;
        set_capacity(disk, size >> 9);

        disk->flags |= GENHD_FL_EXT_DEVT | GENHD_FL_SUPPRESS_PARTITION_INFO;
        disk->major             = null_major;
        disk->first_minor       = nullb->index;
        disk->fops              = &null_fops;
        disk->private_data      = nullb;
        disk->queue             = nullb->q;
        strncpy(disk->disk_name, nullb->disk_name, DISK_NAME_LEN);

        if (nullb->dev->zoned) {
                int ret = blk_revalidate_disk_zones(disk);

                if (ret != 0)
                        return ret;
        }

        add_disk(disk);
        return 0;
}

static int null_init_tag_set(struct nullb *nullb, struct blk_mq_tag_set *set)
{
        set->ops = &null_mq_ops;
        set->nr_hw_queues = nullb ? nullb->dev->submit_queues :
                                                g_submit_queues;
        set->queue_depth = nullb ? nullb->dev->hw_queue_depth :
                                                g_hw_queue_depth;
        set->numa_node = nullb ? nullb->dev->home_node : g_home_node;
        set->cmd_size   = sizeof(struct nullb_cmd);
        set->flags = BLK_MQ_F_SHOULD_MERGE;
        if (g_no_sched)
                set->flags |= BLK_MQ_F_NO_SCHED;
        set->driver_data = NULL;

        if ((nullb && nullb->dev->blocking) || g_blocking)
                set->flags |= BLK_MQ_F_BLOCKING;

        return blk_mq_alloc_tag_set(set);
}

static void null_validate_conf(struct nullb_device *dev)
{
        dev->blocksize = round_down(dev->blocksize, 512);
        dev->blocksize = clamp_t(unsigned int, dev->blocksize, 512, 4096);

        if (dev->queue_mode == NULL_Q_MQ && dev->use_per_node_hctx) {
                if (dev->submit_queues != nr_online_nodes)
                        dev->submit_queues = nr_online_nodes;
        } else if (dev->submit_queues > nr_cpu_ids)
                dev->submit_queues = nr_cpu_ids;
        else if (dev->submit_queues == 0)
                dev->submit_queues = 1;

        dev->queue_mode = min_t(unsigned int, dev->queue_mode, NULL_Q_MQ);
        dev->irqmode = min_t(unsigned int, dev->irqmode, NULL_IRQ_TIMER);

        /* Do memory allocation, so set blocking */
        if (dev->memory_backed)
                dev->blocking = true;
        else /* cache is meaningless */
                dev->cache_size = 0;
        dev->cache_size = min_t(unsigned long, ULONG_MAX / 1024 / 1024,
                                                dev->cache_size);
        dev->mbps = min_t(unsigned int, 1024 * 40, dev->mbps);
        /* can not stop a queue */
        if (dev->queue_mode == NULL_Q_BIO)
                dev->mbps = 0;
}

#ifdef CONFIG_BLK_DEV_NULL_BLK_FAULT_INJECTION
static bool __null_setup_fault(struct fault_attr *attr, char *str)
{
        if (!str[0])
                return true;

        if (!setup_fault_attr(attr, str))
                return false;

        attr->verbose = 0;
        return true;
}
#endif

static bool null_setup_fault(void)
{
#ifdef CONFIG_BLK_DEV_NULL_BLK_FAULT_INJECTION
        if (!__null_setup_fault(&null_timeout_attr, g_timeout_str))
                return false;
        if (!__null_setup_fault(&null_requeue_attr, g_requeue_str))
                return false;
#endif
        return true;
}

static int null_add_dev(struct nullb_device *dev)
{
        struct nullb *nullb;
        int rv;

        null_validate_conf(dev);

        nullb = kzalloc_node(sizeof(*nullb), GFP_KERNEL, dev->home_node);
        if (!nullb) {
                rv = -ENOMEM;
                goto out;
        }
        nullb->dev = dev;
        dev->nullb = nullb;

        spin_lock_init(&nullb->lock);

        rv = setup_queues(nullb);
        if (rv)
                goto out_free_nullb;

        if (dev->queue_mode == NULL_Q_MQ) {
                if (shared_tags) {
                        nullb->tag_set = &tag_set;
                        rv = 0;
                } else {
                        nullb->tag_set = &nullb->__tag_set;
                        rv = null_init_tag_set(nullb, nullb->tag_set);
                }

                if (rv)
                        goto out_cleanup_queues;

                if (!null_setup_fault())
                        goto out_cleanup_queues;

                nullb->tag_set->timeout = 5 * HZ;
                nullb->q = blk_mq_init_queue(nullb->tag_set);
                if (IS_ERR(nullb->q)) {
                        rv = -ENOMEM;
                        goto out_cleanup_tags;
                }
                null_init_queues(nullb);
        } else if (dev->queue_mode == NULL_Q_BIO) {
                nullb->q = blk_alloc_queue_node(GFP_KERNEL, dev->home_node,
                                                NULL);
                if (!nullb->q) {
                        rv = -ENOMEM;
                        goto out_cleanup_queues;
                }
                blk_queue_make_request(nullb->q, null_queue_bio);
                rv = init_driver_queues(nullb);
                if (rv)
                        goto out_cleanup_blk_queue;
        }

        if (dev->mbps) {
                set_bit(NULLB_DEV_FL_THROTTLED, &dev->flags);
                nullb_setup_bwtimer(nullb);
        }

        if (dev->cache_size > 0) {
                set_bit(NULLB_DEV_FL_CACHE, &nullb->dev->flags);
                blk_queue_write_cache(nullb->q, true, true);
                blk_queue_flush_queueable(nullb->q, true);
        }

        if (dev->zoned) {
                rv = null_zone_init(dev);
                if (rv)
                        goto out_cleanup_blk_queue;

                blk_queue_chunk_sectors(nullb->q, dev->zone_size_sects);
                nullb->q->limits.zoned = BLK_ZONED_HM;
        }

        nullb->q->queuedata = nullb;
        blk_queue_flag_set(QUEUE_FLAG_NONROT, nullb->q);
        blk_queue_flag_clear(QUEUE_FLAG_ADD_RANDOM, nullb->q);

        mutex_lock(&lock);
        nullb->index = ida_simple_get(&nullb_indexes, 0, 0, GFP_KERNEL);
        dev->index = nullb->index;
        mutex_unlock(&lock);

        blk_queue_logical_block_size(nullb->q, dev->blocksize);
        blk_queue_physical_block_size(nullb->q, dev->blocksize);

        null_config_discard(nullb);

        sprintf(nullb->disk_name, "nullb%d", nullb->index);

        rv = null_gendisk_register(nullb);
        if (rv)
                goto out_cleanup_zone;

        mutex_lock(&lock);
        list_add_tail(&nullb->list, &nullb_list);
        mutex_unlock(&lock);

        return 0;
out_cleanup_zone:
        if (dev->zoned)
                null_zone_exit(dev);
out_cleanup_blk_queue:
        blk_cleanup_queue(nullb->q);
out_cleanup_tags:
        if (dev->queue_mode == NULL_Q_MQ && nullb->tag_set == &nullb->__tag_set)
                blk_mq_free_tag_set(nullb->tag_set);
out_cleanup_queues:
        cleanup_queues(nullb);
out_free_nullb:
        kfree(nullb);
out:
        return rv;
}

static int __init null_init(void)
{
        int ret = 0;
        unsigned int i;
        struct nullb *nullb;
        struct nullb_device *dev;

        if (g_bs > PAGE_SIZE) {
                pr_warn("null_blk: invalid block size\n");
                pr_warn("null_blk: defaults block size to %lu\n", PAGE_SIZE);
                g_bs = PAGE_SIZE;
        }

        if (!is_power_of_2(g_zone_size)) {
                pr_err("null_blk: zone_size must be power-of-two\n");
                return -EINVAL;
        }

        if (g_queue_mode == NULL_Q_RQ) {
                pr_err("null_blk: legacy IO path no longer available\n");
                return -EINVAL;
        }
        if (g_queue_mode == NULL_Q_MQ && g_use_per_node_hctx) {
                if (g_submit_queues != nr_online_nodes) {
                        pr_warn("null_blk: submit_queues param is set to %u.\n",
                                                        nr_online_nodes);
                        g_submit_queues = nr_online_nodes;
                }
        } else if (g_submit_queues > nr_cpu_ids)
                g_submit_queues = nr_cpu_ids;
        else if (g_submit_queues <= 0)
                g_submit_queues = 1;

        if (g_queue_mode == NULL_Q_MQ && shared_tags) {
                ret = null_init_tag_set(NULL, &tag_set);
                if (ret)
                        return ret;
        }

        config_group_init(&nullb_subsys.su_group);
        mutex_init(&nullb_subsys.su_mutex);

        ret = configfs_register_subsystem(&nullb_subsys);
        if (ret)
                goto err_tagset;

        mutex_init(&lock);

        null_major = register_blkdev(0, "nullb");
        if (null_major < 0) {
                ret = null_major;
                goto err_conf;
        }

        for (i = 0; i < nr_devices; i++) {
                dev = null_alloc_dev();
                if (!dev) {
                        ret = -ENOMEM;
                        goto err_dev;
                }
                ret = null_add_dev(dev);
                if (ret) {
                        null_free_dev(dev);
                        goto err_dev;
                }
        }

        pr_info("null: module loaded\n");
        return 0;

err_dev:
        while (!list_empty(&nullb_list)) {
                nullb = list_entry(nullb_list.next, struct nullb, list);
                dev = nullb->dev;
                null_del_dev(nullb);
                null_free_dev(dev);
        }
        unregister_blkdev(null_major, "nullb");
err_conf:
        configfs_unregister_subsystem(&nullb_subsys);
err_tagset:
        if (g_queue_mode == NULL_Q_MQ && shared_tags)
                blk_mq_free_tag_set(&tag_set);
        return ret;
}

static void __exit null_exit(void)
{
        struct nullb *nullb;

        configfs_unregister_subsystem(&nullb_subsys);

        unregister_blkdev(null_major, "nullb");

        mutex_lock(&lock);
        while (!list_empty(&nullb_list)) {
                struct nullb_device *dev;

                nullb = list_entry(nullb_list.next, struct nullb, list);
                dev = nullb->dev;
                null_del_dev(nullb);
                null_free_dev(dev);
        }
        mutex_unlock(&lock);

        if (g_queue_mode == NULL_Q_MQ && shared_tags)
                blk_mq_free_tag_set(&tag_set);
}

module_init(null_init);
module_exit(null_exit);

MODULE_AUTHOR("Jens Axboe <axboe@kernel.dk>");
MODULE_LICENSE("GPL");