// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright 2023 Red Hat
 */

#include "io-submitter.h"

#include <linux/bio.h>
#include <linux/kernel.h>
#include <linux/mutex.h>

#include "memory-alloc.h"
#include "permassert.h"

#include "data-vio.h"
#include "logger.h"
#include "types.h"
#include "vdo.h"
#include "vio.h"

/*
 * Submission of bio operations to the underlying storage device will go through a separate work
 * queue thread (or more than one) to prevent blocking in other threads if the storage device has a
 * full queue. The plug structure allows that thread to do better batching of requests to make the
 * I/O more efficient.
 *
 * When multiple worker threads are used, a thread is chosen for a I/O operation submission based
 * on the PBN, so a given PBN will consistently wind up on the same thread. Flush operations are
 * assigned round-robin.
 *
 * The map (protected by the mutex) collects pending I/O operations so that the worker thread can
 * reorder them to try to encourage I/O request merging in the request queue underneath.
 */
struct bio_queue_data {
        struct vdo_work_queue *queue;
        struct blk_plug plug;
        struct int_map *map;
        struct mutex lock;
        unsigned int queue_number;
};

struct io_submitter {
        unsigned int num_bio_queues_used;
        unsigned int bio_queue_rotation_interval;
        struct bio_queue_data bio_queue_data[];
};

static void start_bio_queue(void *ptr)
{
        struct bio_queue_data *bio_queue_data = ptr;

        blk_start_plug(&bio_queue_data->plug);
}

static void finish_bio_queue(void *ptr)
{
        struct bio_queue_data *bio_queue_data = ptr;

        blk_finish_plug(&bio_queue_data->plug);
}

static const struct vdo_work_queue_type bio_queue_type = {
        .start = start_bio_queue,
        .finish = finish_bio_queue,
        .max_priority = BIO_Q_MAX_PRIORITY,
        .default_priority = BIO_Q_DATA_PRIORITY,
};

/**
 * count_all_bios() - Determine which bio counter to use.
 * @vio: The vio associated with the bio.
 * @bio: The bio to count.
 */
static void count_all_bios(struct vio *vio, struct bio *bio)
{
        struct atomic_statistics *stats = &vio->completion.vdo->stats;

        if (is_data_vio(vio)) {
                vdo_count_bios(&stats->bios_out, bio);
                return;
        }

        vdo_count_bios(&stats->bios_meta, bio);
        if (vio->type == VIO_TYPE_RECOVERY_JOURNAL)
                vdo_count_bios(&stats->bios_journal, bio);
        else if (vio->type == VIO_TYPE_BLOCK_MAP)
                vdo_count_bios(&stats->bios_page_cache, bio);
}

/**
 * assert_in_bio_zone() - Assert that a vio is in the correct bio zone and not in interrupt
 *                        context.
 * @vio: The vio to check.
 */
static void assert_in_bio_zone(struct vio *vio)
{
        VDO_ASSERT_LOG_ONLY(!in_interrupt(), "not in interrupt context");
        assert_vio_in_bio_zone(vio);
}

/**
 * send_bio_to_device() - Update stats and tracing info, then submit the supplied bio to the OS for
 *                        processing.
 * @vio: The vio associated with the bio.
 * @bio: The bio to submit to the OS.
 */
static void send_bio_to_device(struct vio *vio, struct bio *bio)
{
        struct vdo *vdo = vio->completion.vdo;

        assert_in_bio_zone(vio);
        atomic64_inc(&vdo->stats.bios_submitted);
        count_all_bios(vio, bio);
        bio_set_dev(bio, vdo_get_backing_device(vdo));
        submit_bio_noacct(bio);
}

/**
 * vdo_submit_vio() - Submits a vio's bio to the underlying block device. May block if the device
 *                    is busy. This callback should be used by vios which did not attempt to merge.
 * @completion: The vio to submit.
 */
void vdo_submit_vio(struct vdo_completion *completion)
{
        struct vio *vio = as_vio(completion);

        send_bio_to_device(vio, vio->bio);
}

/**
 * get_bio_list() - Extract the list of bios to submit from a vio.
 * @vio: The vio submitting I/O.
 *
 * The list will always contain at least one entry (the bio for the vio on which it is called), but
 * other bios may have been merged with it as well.
 *
 * Return: The head of the bio list to submit.
 */
static struct bio *get_bio_list(struct vio *vio)
{
        struct bio *bio;
        struct io_submitter *submitter = vio->completion.vdo->io_submitter;
        struct bio_queue_data *bio_queue_data = &(submitter->bio_queue_data[vio->bio_zone]);

        assert_in_bio_zone(vio);

        mutex_lock(&bio_queue_data->lock);
        vdo_int_map_remove(bio_queue_data->map,
                           vio->bios_merged.head->bi_iter.bi_sector);
        vdo_int_map_remove(bio_queue_data->map,
                           vio->bios_merged.tail->bi_iter.bi_sector);
        bio = vio->bios_merged.head;
        bio_list_init(&vio->bios_merged);
        mutex_unlock(&bio_queue_data->lock);

        return bio;
}

/**
 * submit_data_vio() - Submit a data_vio's bio to the storage below along with
 *                     any bios that have been merged with it.
 * @completion: The vio to submit.
 *
 * Context: This call may block and so should only be called from a bio thread.
 */
static void submit_data_vio(struct vdo_completion *completion)
{
        struct bio *bio, *next;
        struct vio *vio = as_vio(completion);

        assert_in_bio_zone(vio);
        for (bio = get_bio_list(vio); bio != NULL; bio = next) {
                next = bio->bi_next;
                bio->bi_next = NULL;
                send_bio_to_device((struct vio *) bio->bi_private, bio);
        }
}

/**
 * get_mergeable_locked() - Attempt to find an already queued bio that the current bio can be
 *                          merged with.
 * @map: The bio map to use for merging.
 * @vio: The vio we want to merge.
 * @back_merge: Set to true for a back merge, false for a front merge.
 *
 * There are two types of merging possible, forward and backward, which are distinguished by a flag
 * that uses kernel elevator terminology.
 *
 * Return: The vio to merge to, NULL if no merging is possible.
 */
static struct vio *get_mergeable_locked(struct int_map *map, struct vio *vio,
                                        bool back_merge)
{
        struct bio *bio = vio->bio;
        sector_t merge_sector = bio->bi_iter.bi_sector;
        struct vio *vio_merge;

        if (back_merge)
                merge_sector -= VDO_SECTORS_PER_BLOCK;
        else
                merge_sector += VDO_SECTORS_PER_BLOCK;

        vio_merge = vdo_int_map_get(map, merge_sector);

        if (vio_merge == NULL)
                return NULL;

        if (vio->completion.priority != vio_merge->completion.priority)
                return NULL;

        if (bio_data_dir(bio) != bio_data_dir(vio_merge->bio))
                return NULL;

        if (bio_list_empty(&vio_merge->bios_merged))
                return NULL;

        if (back_merge) {
                return (vio_merge->bios_merged.tail->bi_iter.bi_sector == merge_sector ?
                        vio_merge : NULL);
        }

        return (vio_merge->bios_merged.head->bi_iter.bi_sector == merge_sector ?
                vio_merge : NULL);
}

static int map_merged_vio(struct int_map *bio_map, struct vio *vio)
{
        int result;
        sector_t bio_sector;

        bio_sector = vio->bios_merged.head->bi_iter.bi_sector;
        result = vdo_int_map_put(bio_map, bio_sector, vio, true, NULL);
        if (result != VDO_SUCCESS)
                return result;

        bio_sector = vio->bios_merged.tail->bi_iter.bi_sector;
        return vdo_int_map_put(bio_map, bio_sector, vio, true, NULL);
}

static int merge_to_prev_tail(struct int_map *bio_map, struct vio *vio,
                              struct vio *prev_vio)
{
        vdo_int_map_remove(bio_map, prev_vio->bios_merged.tail->bi_iter.bi_sector);
        bio_list_merge(&prev_vio->bios_merged, &vio->bios_merged);
        return map_merged_vio(bio_map, prev_vio);
}

static int merge_to_next_head(struct int_map *bio_map, struct vio *vio,
                              struct vio *next_vio)
{
        /*
         * Handle "next merge" and "gap fill" cases the same way so as to reorder bios in a way
         * that's compatible with using funnel queues in work queues. This avoids removing an
         * existing completion.
         */
        vdo_int_map_remove(bio_map, next_vio->bios_merged.head->bi_iter.bi_sector);
        bio_list_merge_head(&next_vio->bios_merged, &vio->bios_merged);
        return map_merged_vio(bio_map, next_vio);
}

/**
 * try_bio_map_merge() - Attempt to merge a vio's bio with other pending I/Os.
 * @vio: The vio to merge.
 *
 * Currently this is only used for data_vios, but is broken out for future use with metadata vios.
 *
 * Return: Whether or not the vio was merged.
 */
static bool try_bio_map_merge(struct vio *vio)
{
        int result;
        bool merged = true;
        struct bio *bio = vio->bio;
        struct vio *prev_vio, *next_vio;
        struct vdo *vdo = vio->completion.vdo;
        struct bio_queue_data *bio_queue_data =
                &vdo->io_submitter->bio_queue_data[vio->bio_zone];

        bio->bi_next = NULL;
        bio_list_init(&vio->bios_merged);
        bio_list_add(&vio->bios_merged, bio);

        mutex_lock(&bio_queue_data->lock);
        prev_vio = get_mergeable_locked(bio_queue_data->map, vio, true);
        next_vio = get_mergeable_locked(bio_queue_data->map, vio, false);
        if (prev_vio == next_vio)
                next_vio = NULL;

        if ((prev_vio == NULL) && (next_vio == NULL)) {
                /* no merge. just add to bio_queue */
                merged = false;
                result = vdo_int_map_put(bio_queue_data->map,
                                         bio->bi_iter.bi_sector,
                                         vio, true, NULL);
        } else if (next_vio == NULL) {
                /* Only prev. merge to prev's tail */
                result = merge_to_prev_tail(bio_queue_data->map, vio, prev_vio);
        } else {
                /* Only next. merge to next's head */
                result = merge_to_next_head(bio_queue_data->map, vio, next_vio);
        }
        mutex_unlock(&bio_queue_data->lock);

        /* We don't care about failure of int_map_put in this case. */
        VDO_ASSERT_LOG_ONLY(result == VDO_SUCCESS, "bio map insertion succeeds");
        return merged;
}

/**
 * vdo_submit_data_vio() - Submit I/O for a data_vio.
 * @data_vio: The data_vio for which to issue I/O.
 *
 * If possible, this I/O will be merged other pending I/Os. Otherwise, the data_vio will be sent to
 * the appropriate bio zone directly.
 */
void vdo_submit_data_vio(struct data_vio *data_vio)
{
        if (try_bio_map_merge(&data_vio->vio))
                return;

        launch_data_vio_bio_zone_callback(data_vio, submit_data_vio);
}

/**
 * __submit_metadata_vio() - Submit I/O for a metadata vio.
 * @vio: The vio for which to issue I/O.
 * @physical: The physical block number to read or write.
 * @callback: The bio endio function which will be called after the I/O completes.
 * @error_handler: The handler for submission or I/O errors; may be NULL.
 * @operation: The type of I/O to perform.
 * @data: The buffer to read or write; may be NULL.
 * @size: The I/O amount in bytes.
 *
 * The vio is enqueued on a vdo bio queue so that bio submission (which may block) does not block
 * other vdo threads.
 *
 * That the error handler will run on the correct thread is only true so long as the thread calling
 * this function, and the thread set in the endio callback are the same, as well as the fact that
 * no error can occur on the bio queue. Currently this is true for all callers, but additional care
 * will be needed if this ever changes.
 */
void __submit_metadata_vio(struct vio *vio, physical_block_number_t physical,
                           bio_end_io_t callback, vdo_action_fn error_handler,
                           blk_opf_t operation, char *data, int size)
{
        int result;
        struct vdo_completion *completion = &vio->completion;
        const struct admin_state_code *code = vdo_get_admin_state(completion->vdo);


        VDO_ASSERT_LOG_ONLY(!code->quiescent, "I/O not allowed in state %s", code->name);

        vdo_reset_completion(completion);
        completion->error_handler = error_handler;
        result = vio_reset_bio_with_size(vio, data, size, callback, operation | REQ_META,
                                         physical);
        if (result != VDO_SUCCESS) {
                continue_vio(vio, result);
                return;
        }

        vdo_set_completion_callback(completion, vdo_submit_vio,
                                    get_vio_bio_zone_thread_id(vio));
        vdo_launch_completion_with_priority(completion, get_metadata_priority(vio));
}

/**
 * vdo_make_io_submitter() - Create an io_submitter structure.
 * @thread_count: Number of bio-submission threads to set up.
 * @rotation_interval: Interval to use when rotating between bio-submission threads when enqueuing
 *                     completions.
 * @max_requests_active: Number of bios for merge tracking.
 * @vdo: The vdo which will use this submitter.
 * @io_submitter_ptr: pointer to the new data structure.
 *
 * Return: VDO_SUCCESS or an error.
 */
int vdo_make_io_submitter(unsigned int thread_count, unsigned int rotation_interval,
                          unsigned int max_requests_active, struct vdo *vdo,
                          struct io_submitter **io_submitter_ptr)
{
        unsigned int i;
        struct io_submitter *io_submitter;
        int result;

        result = vdo_allocate_extended(struct io_submitter, thread_count,
                                       struct bio_queue_data, "bio submission data",
                                       &io_submitter);
        if (result != VDO_SUCCESS)
                return result;

        io_submitter->bio_queue_rotation_interval = rotation_interval;

        /* Setup for each bio-submission work queue */
        for (i = 0; i < thread_count; i++) {
                struct bio_queue_data *bio_queue_data = &io_submitter->bio_queue_data[i];

                mutex_init(&bio_queue_data->lock);
                /*
                 * One I/O operation per request, but both first & last sector numbers.
                 *
                 * If requests are assigned to threads round-robin, they should be distributed
                 * quite evenly. But if they're assigned based on PBN, things can sometimes be very
                 * uneven. So for now, we'll assume that all requests *may* wind up on one thread,
                 * and thus all in the same map.
                 */
                result = vdo_int_map_create(max_requests_active * 2,
                                            &bio_queue_data->map);
                if (result != VDO_SUCCESS) {
                        /*
                         * Clean up the partially initialized bio-queue entirely and indicate that
                         * initialization failed.
                         */
                        vdo_log_error("bio map initialization failed %d", result);
                        vdo_cleanup_io_submitter(io_submitter);
                        vdo_free_io_submitter(io_submitter);
                        return result;
                }

                bio_queue_data->queue_number = i;
                result = vdo_make_thread(vdo, vdo->thread_config.bio_threads[i],
                                         &bio_queue_type, 1, (void **) &bio_queue_data);
                if (result != VDO_SUCCESS) {
                        /*
                         * Clean up the partially initialized bio-queue entirely and indicate that
                         * initialization failed.
                         */
                        vdo_int_map_free(vdo_forget(bio_queue_data->map));
                        vdo_log_error("bio queue initialization failed %d", result);
                        vdo_cleanup_io_submitter(io_submitter);
                        vdo_free_io_submitter(io_submitter);
                        return result;
                }

                bio_queue_data->queue = vdo->threads[vdo->thread_config.bio_threads[i]].queue;
                io_submitter->num_bio_queues_used++;
        }

        *io_submitter_ptr = io_submitter;

        return VDO_SUCCESS;
}

/**
 * vdo_cleanup_io_submitter() - Tear down the io_submitter fields as needed for a physical layer.
 * @io_submitter: The I/O submitter data to tear down; may be NULL.
 */
void vdo_cleanup_io_submitter(struct io_submitter *io_submitter)
{
        int i;

        if (io_submitter == NULL)
                return;

        for (i = io_submitter->num_bio_queues_used - 1; i >= 0; i--)
                vdo_finish_work_queue(io_submitter->bio_queue_data[i].queue);
}

/**
 * vdo_free_io_submitter() - Free the io_submitter fields and structure as needed.
 * @io_submitter: The I/O submitter data to destroy.
 *
 * This must be called after vdo_cleanup_io_submitter(). It is used to release resources late in
 * the shutdown process to avoid or reduce the chance of race conditions.
 */
void vdo_free_io_submitter(struct io_submitter *io_submitter)
{
        int i;

        if (io_submitter == NULL)
                return;

        for (i = io_submitter->num_bio_queues_used - 1; i >= 0; i--) {
                io_submitter->num_bio_queues_used--;
                /* vdo_destroy() will free the work queue, so just give up our reference to it. */
                vdo_forget(io_submitter->bio_queue_data[i].queue);
                vdo_int_map_free(vdo_forget(io_submitter->bio_queue_data[i].map));
        }
        vdo_free(io_submitter);
}