/*
 * Copyright (C) 2016 Red Hat, Inc. All rights reserved.
 *
 * This file is released under the GPL.
 */

#include "dm-core.h"
#include "dm-rq.h"

#include <linux/elevator.h> /* for rq_end_sector() */
#include <linux/blk-mq.h>

#define DM_MSG_PREFIX "core-rq"

/*
 * One of these is allocated per request.
 */
struct dm_rq_target_io {
        struct mapped_device *md;
        struct dm_target *ti;
        struct request *orig, *clone;
        struct kthread_work work;
        blk_status_t error;
        union map_info info;
        struct dm_stats_aux stats_aux;
        unsigned long duration_jiffies;
        unsigned n_sectors;
        unsigned completed;
};

#define DM_MQ_NR_HW_QUEUES 1
#define DM_MQ_QUEUE_DEPTH 2048
static unsigned dm_mq_nr_hw_queues = DM_MQ_NR_HW_QUEUES;
static unsigned dm_mq_queue_depth = DM_MQ_QUEUE_DEPTH;

/*
 * Request-based DM's mempools' reserved IOs set by the user.
 */
#define RESERVED_REQUEST_BASED_IOS      256
static unsigned reserved_rq_based_ios = RESERVED_REQUEST_BASED_IOS;

unsigned dm_get_reserved_rq_based_ios(void)
{
        return __dm_get_module_param(&reserved_rq_based_ios,
                                     RESERVED_REQUEST_BASED_IOS, DM_RESERVED_MAX_IOS);
}
EXPORT_SYMBOL_GPL(dm_get_reserved_rq_based_ios);

static unsigned dm_get_blk_mq_nr_hw_queues(void)
{
        return __dm_get_module_param(&dm_mq_nr_hw_queues, 1, 32);
}

static unsigned dm_get_blk_mq_queue_depth(void)
{
        return __dm_get_module_param(&dm_mq_queue_depth,
                                     DM_MQ_QUEUE_DEPTH, BLK_MQ_MAX_DEPTH);
}

int dm_request_based(struct mapped_device *md)
{
        return queue_is_mq(md->queue);
}

void dm_start_queue(struct request_queue *q)
{
        blk_mq_unquiesce_queue(q);
        blk_mq_kick_requeue_list(q);
}

void dm_stop_queue(struct request_queue *q)
{
        blk_mq_quiesce_queue(q);
}

/*
 * Partial completion handling for request-based dm
 */
static void end_clone_bio(struct bio *clone)
{
        struct dm_rq_clone_bio_info *info =
                container_of(clone, struct dm_rq_clone_bio_info, clone);
        struct dm_rq_target_io *tio = info->tio;
        unsigned int nr_bytes = info->orig->bi_iter.bi_size;
        blk_status_t error = clone->bi_status;
        bool is_last = !clone->bi_next;

        bio_put(clone);

        if (tio->error)
                /*
                 * An error has already been detected on the request.
                 * Once error occurred, just let clone->end_io() handle
                 * the remainder.
                 */
                return;
        else if (error) {
                /*
                 * Don't notice the error to the upper layer yet.
                 * The error handling decision is made by the target driver,
                 * when the request is completed.
                 */
                tio->error = error;
                goto exit;
        }

        /*
         * I/O for the bio successfully completed.
         * Notice the data completion to the upper layer.
         */
        tio->completed += nr_bytes;

        /*
         * Update the original request.
         * Do not use blk_mq_end_request() here, because it may complete
         * the original request before the clone, and break the ordering.
         */
        if (is_last)
 exit:
                blk_update_request(tio->orig, BLK_STS_OK, tio->completed);
}

static struct dm_rq_target_io *tio_from_request(struct request *rq)
{
        return blk_mq_rq_to_pdu(rq);
}

static void rq_end_stats(struct mapped_device *md, struct request *orig)
{
        if (unlikely(dm_stats_used(&md->stats))) {
                struct dm_rq_target_io *tio = tio_from_request(orig);
                tio->duration_jiffies = jiffies - tio->duration_jiffies;
                dm_stats_account_io(&md->stats, rq_data_dir(orig),
                                    blk_rq_pos(orig), tio->n_sectors, true,
                                    tio->duration_jiffies, &tio->stats_aux);
        }
}

/*
 * Don't touch any member of the md after calling this function because
 * the md may be freed in dm_put() at the end of this function.
 * Or do dm_get() before calling this function and dm_put() later.
 */
static void rq_completed(struct mapped_device *md)
{
        /*
         * dm_put() must be at the end of this function. See the comment above
         */
        dm_put(md);
}

/*
 * Complete the clone and the original request.
 * Must be called without clone's queue lock held,
 * see end_clone_request() for more details.
 */
static void dm_end_request(struct request *clone, blk_status_t error)
{
        struct dm_rq_target_io *tio = clone->end_io_data;
        struct mapped_device *md = tio->md;
        struct request *rq = tio->orig;

        blk_rq_unprep_clone(clone);
        tio->ti->type->release_clone_rq(clone, NULL);

        rq_end_stats(md, rq);
        blk_mq_end_request(rq, error);
        rq_completed(md);
}

static void __dm_mq_kick_requeue_list(struct request_queue *q, unsigned long msecs)
{
        blk_mq_delay_kick_requeue_list(q, msecs);
}

void dm_mq_kick_requeue_list(struct mapped_device *md)
{
        __dm_mq_kick_requeue_list(md->queue, 0);
}
EXPORT_SYMBOL(dm_mq_kick_requeue_list);

static void dm_mq_delay_requeue_request(struct request *rq, unsigned long msecs)
{
        blk_mq_requeue_request(rq, false);
        __dm_mq_kick_requeue_list(rq->q, msecs);
}

static void dm_requeue_original_request(struct dm_rq_target_io *tio, bool delay_requeue)
{
        struct mapped_device *md = tio->md;
        struct request *rq = tio->orig;
        unsigned long delay_ms = delay_requeue ? 100 : 0;

        rq_end_stats(md, rq);
        if (tio->clone) {
                blk_rq_unprep_clone(tio->clone);
                tio->ti->type->release_clone_rq(tio->clone, NULL);
        }

        dm_mq_delay_requeue_request(rq, delay_ms);
        rq_completed(md);
}

static void dm_done(struct request *clone, blk_status_t error, bool mapped)
{
        int r = DM_ENDIO_DONE;
        struct dm_rq_target_io *tio = clone->end_io_data;
        dm_request_endio_fn rq_end_io = NULL;

        if (tio->ti) {
                rq_end_io = tio->ti->type->rq_end_io;

                if (mapped && rq_end_io)
                        r = rq_end_io(tio->ti, clone, error, &tio->info);
        }

        if (unlikely(error == BLK_STS_TARGET)) {
                if (req_op(clone) == REQ_OP_DISCARD &&
                    !clone->q->limits.max_discard_sectors)
                        disable_discard(tio->md);
                else if (req_op(clone) == REQ_OP_WRITE_SAME &&
                         !clone->q->limits.max_write_same_sectors)
                        disable_write_same(tio->md);
                else if (req_op(clone) == REQ_OP_WRITE_ZEROES &&
                         !clone->q->limits.max_write_zeroes_sectors)
                        disable_write_zeroes(tio->md);
        }

        switch (r) {
        case DM_ENDIO_DONE:
                /* The target wants to complete the I/O */
                dm_end_request(clone, error);
                break;
        case DM_ENDIO_INCOMPLETE:
                /* The target will handle the I/O */
                return;
        case DM_ENDIO_REQUEUE:
                /* The target wants to requeue the I/O */
                dm_requeue_original_request(tio, false);
                break;
        case DM_ENDIO_DELAY_REQUEUE:
                /* The target wants to requeue the I/O after a delay */
                dm_requeue_original_request(tio, true);
                break;
        default:
                DMWARN("unimplemented target endio return value: %d", r);
                BUG();
        }
}

/*
 * Request completion handler for request-based dm
 */
static void dm_softirq_done(struct request *rq)
{
        bool mapped = true;
        struct dm_rq_target_io *tio = tio_from_request(rq);
        struct request *clone = tio->clone;

        if (!clone) {
                struct mapped_device *md = tio->md;

                rq_end_stats(md, rq);
                blk_mq_end_request(rq, tio->error);
                rq_completed(md);
                return;
        }

        if (rq->rq_flags & RQF_FAILED)
                mapped = false;

        dm_done(clone, tio->error, mapped);
}

/*
 * Complete the clone and the original request with the error status
 * through softirq context.
 */
static void dm_complete_request(struct request *rq, blk_status_t error)
{
        struct dm_rq_target_io *tio = tio_from_request(rq);

        tio->error = error;
        if (likely(!blk_should_fake_timeout(rq->q)))
                blk_mq_complete_request(rq);
}

/*
 * Complete the not-mapped clone and the original request with the error status
 * through softirq context.
 * Target's rq_end_io() function isn't called.
 * This may be used when the target's clone_and_map_rq() function fails.
 */
static void dm_kill_unmapped_request(struct request *rq, blk_status_t error)
{
        rq->rq_flags |= RQF_FAILED;
        dm_complete_request(rq, error);
}

static void end_clone_request(struct request *clone, blk_status_t error)
{
        struct dm_rq_target_io *tio = clone->end_io_data;

        dm_complete_request(tio->orig, error);
}

static blk_status_t dm_dispatch_clone_request(struct request *clone, struct request *rq)
{
        blk_status_t r;

        if (blk_queue_io_stat(clone->q))
                clone->rq_flags |= RQF_IO_STAT;

        clone->start_time_ns = ktime_get_ns();
        r = blk_insert_cloned_request(clone->q, clone);
        if (r != BLK_STS_OK && r != BLK_STS_RESOURCE && r != BLK_STS_DEV_RESOURCE)
                /* must complete clone in terms of original request */
                dm_complete_request(rq, r);
        return r;
}

static int dm_rq_bio_constructor(struct bio *bio, struct bio *bio_orig,
                                 void *data)
{
        struct dm_rq_target_io *tio = data;
        struct dm_rq_clone_bio_info *info =
                container_of(bio, struct dm_rq_clone_bio_info, clone);

        info->orig = bio_orig;
        info->tio = tio;
        bio->bi_end_io = end_clone_bio;

        return 0;
}

static int setup_clone(struct request *clone, struct request *rq,
                       struct dm_rq_target_io *tio, gfp_t gfp_mask)
{
        int r;

        r = blk_rq_prep_clone(clone, rq, &tio->md->bs, gfp_mask,
                              dm_rq_bio_constructor, tio);
        if (r)
                return r;

        clone->end_io = end_clone_request;
        clone->end_io_data = tio;

        tio->clone = clone;

        return 0;
}

static void init_tio(struct dm_rq_target_io *tio, struct request *rq,
                     struct mapped_device *md)
{
        tio->md = md;
        tio->ti = NULL;
        tio->clone = NULL;
        tio->orig = rq;
        tio->error = 0;
        tio->completed = 0;
        /*
         * Avoid initializing info for blk-mq; it passes
         * target-specific data through info.ptr
         * (see: dm_mq_init_request)
         */
        if (!md->init_tio_pdu)
                memset(&tio->info, 0, sizeof(tio->info));
}

/*
 * Returns:
 * DM_MAPIO_*       : the request has been processed as indicated
 * DM_MAPIO_REQUEUE : the original request needs to be immediately requeued
 * < 0              : the request was completed due to failure
 */
static int map_request(struct dm_rq_target_io *tio)
{
        int r;
        struct dm_target *ti = tio->ti;
        struct mapped_device *md = tio->md;
        struct request *rq = tio->orig;
        struct request *clone = NULL;
        blk_status_t ret;

        r = ti->type->clone_and_map_rq(ti, rq, &tio->info, &clone);
        switch (r) {
        case DM_MAPIO_SUBMITTED:
                /* The target has taken the I/O to submit by itself later */
                break;
        case DM_MAPIO_REMAPPED:
                if (setup_clone(clone, rq, tio, GFP_ATOMIC)) {
                        /* -ENOMEM */
                        ti->type->release_clone_rq(clone, &tio->info);
                        return DM_MAPIO_REQUEUE;
                }

                /* The target has remapped the I/O so dispatch it */
                trace_block_rq_remap(clone, disk_devt(dm_disk(md)),
                                     blk_rq_pos(rq));
                ret = dm_dispatch_clone_request(clone, rq);
                if (ret == BLK_STS_RESOURCE || ret == BLK_STS_DEV_RESOURCE) {
                        blk_rq_unprep_clone(clone);
                        blk_mq_cleanup_rq(clone);
                        tio->ti->type->release_clone_rq(clone, &tio->info);
                        tio->clone = NULL;
                        return DM_MAPIO_REQUEUE;
                }
                break;
        case DM_MAPIO_REQUEUE:
                /* The target wants to requeue the I/O */
                break;
        case DM_MAPIO_DELAY_REQUEUE:
                /* The target wants to requeue the I/O after a delay */
                dm_requeue_original_request(tio, true);
                break;
        case DM_MAPIO_KILL:
                /* The target wants to complete the I/O */
                dm_kill_unmapped_request(rq, BLK_STS_IOERR);
                break;
        default:
                DMWARN("unimplemented target map return value: %d", r);
                BUG();
        }

        return r;
}

/* DEPRECATED: previously used for request-based merge heuristic in dm_request_fn() */
ssize_t dm_attr_rq_based_seq_io_merge_deadline_show(struct mapped_device *md, char *buf)
{
        return sprintf(buf, "%u\n", 0);
}

ssize_t dm_attr_rq_based_seq_io_merge_deadline_store(struct mapped_device *md,
                                                     const char *buf, size_t count)
{
        return count;
}

static void dm_start_request(struct mapped_device *md, struct request *orig)
{
        blk_mq_start_request(orig);

        if (unlikely(dm_stats_used(&md->stats))) {
                struct dm_rq_target_io *tio = tio_from_request(orig);
                tio->duration_jiffies = jiffies;
                tio->n_sectors = blk_rq_sectors(orig);
                dm_stats_account_io(&md->stats, rq_data_dir(orig),
                                    blk_rq_pos(orig), tio->n_sectors, false, 0,
                                    &tio->stats_aux);
        }

        /*
         * Hold the md reference here for the in-flight I/O.
         * We can't rely on the reference count by device opener,
         * because the device may be closed during the request completion
         * when all bios are completed.
         * See the comment in rq_completed() too.
         */
        dm_get(md);
}

static int dm_mq_init_request(struct blk_mq_tag_set *set, struct request *rq,
                              unsigned int hctx_idx, unsigned int numa_node)
{
        struct mapped_device *md = set->driver_data;
        struct dm_rq_target_io *tio = blk_mq_rq_to_pdu(rq);

        /*
         * Must initialize md member of tio, otherwise it won't
         * be available in dm_mq_queue_rq.
         */
        tio->md = md;

        if (md->init_tio_pdu) {
                /* target-specific per-io data is immediately after the tio */
                tio->info.ptr = tio + 1;
        }

        return 0;
}

static blk_status_t dm_mq_queue_rq(struct blk_mq_hw_ctx *hctx,
                          const struct blk_mq_queue_data *bd)
{
        struct request *rq = bd->rq;
        struct dm_rq_target_io *tio = blk_mq_rq_to_pdu(rq);
        struct mapped_device *md = tio->md;
        struct dm_target *ti = md->immutable_target;

        /*
         * blk-mq's unquiesce may come from outside events, such as
         * elevator switch, updating nr_requests or others, and request may
         * come during suspend, so simply ask for blk-mq to requeue it.
         */
        if (unlikely(test_bit(DMF_BLOCK_IO_FOR_SUSPEND, &md->flags)))
                return BLK_STS_RESOURCE;

        if (unlikely(!ti)) {
                int srcu_idx;
                struct dm_table *map = dm_get_live_table(md, &srcu_idx);

                ti = dm_table_find_target(map, 0);
                dm_put_live_table(md, srcu_idx);
        }

        if (ti->type->busy && ti->type->busy(ti))
                return BLK_STS_RESOURCE;

        dm_start_request(md, rq);

        /* Init tio using md established in .init_request */
        init_tio(tio, rq, md);

        /*
         * Establish tio->ti before calling map_request().
         */
        tio->ti = ti;

        /* Direct call is fine since .queue_rq allows allocations */
        if (map_request(tio) == DM_MAPIO_REQUEUE) {
                /* Undo dm_start_request() before requeuing */
                rq_end_stats(md, rq);
                rq_completed(md);
                return BLK_STS_RESOURCE;
        }

        return BLK_STS_OK;
}

static const struct blk_mq_ops dm_mq_ops = {
        .queue_rq = dm_mq_queue_rq,
        .complete = dm_softirq_done,
        .init_request = dm_mq_init_request,
};

int dm_mq_init_request_queue(struct mapped_device *md, struct dm_table *t)
{
        struct request_queue *q;
        struct dm_target *immutable_tgt;
        int err;

        md->tag_set = kzalloc_node(sizeof(struct blk_mq_tag_set), GFP_KERNEL, md->numa_node_id);
        if (!md->tag_set)
                return -ENOMEM;

        md->tag_set->ops = &dm_mq_ops;
        md->tag_set->queue_depth = dm_get_blk_mq_queue_depth();
        md->tag_set->numa_node = md->numa_node_id;
        md->tag_set->flags = BLK_MQ_F_SHOULD_MERGE | BLK_MQ_F_STACKING;
        md->tag_set->nr_hw_queues = dm_get_blk_mq_nr_hw_queues();
        md->tag_set->driver_data = md;

        md->tag_set->cmd_size = sizeof(struct dm_rq_target_io);
        immutable_tgt = dm_table_get_immutable_target(t);
        if (immutable_tgt && immutable_tgt->per_io_data_size) {
                /* any target-specific per-io data is immediately after the tio */
                md->tag_set->cmd_size += immutable_tgt->per_io_data_size;
                md->init_tio_pdu = true;
        }

        err = blk_mq_alloc_tag_set(md->tag_set);
        if (err)
                goto out_kfree_tag_set;

        q = blk_mq_init_allocated_queue(md->tag_set, md->queue, true);
        if (IS_ERR(q)) {
                err = PTR_ERR(q);
                goto out_tag_set;
        }

        return 0;

out_tag_set:
        blk_mq_free_tag_set(md->tag_set);
out_kfree_tag_set:
        kfree(md->tag_set);
        md->tag_set = NULL;

        return err;
}

void dm_mq_cleanup_mapped_device(struct mapped_device *md)
{
        if (md->tag_set) {
                blk_mq_free_tag_set(md->tag_set);
                kfree(md->tag_set);
                md->tag_set = NULL;
        }
}

module_param(reserved_rq_based_ios, uint, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(reserved_rq_based_ios, "Reserved IOs in request-based mempools");

/* Unused, but preserved for userspace compatibility */
static bool use_blk_mq = true;
module_param(use_blk_mq, bool, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(use_blk_mq, "Use block multiqueue for request-based DM devices");

module_param(dm_mq_nr_hw_queues, uint, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(dm_mq_nr_hw_queues, "Number of hardware queues for request-based dm-mq devices");

module_param(dm_mq_queue_depth, uint, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(dm_mq_queue_depth, "Queue depth for request-based dm-mq devices");