/*
 * Copyright (C) 2001-2003 Sistina Software (UK) Limited.
 *
 * This file is released under the GPL.
 */

#include <linux/device-mapper.h>

#include <linux/module.h>
#include <linux/init.h>
#include <linux/blkdev.h>
#include <linux/bio.h>
#include <linux/slab.h>
#include <linux/log2.h>

#define DM_MSG_PREFIX "striped"
#define DM_IO_ERROR_THRESHOLD 15

struct stripe {
        struct dm_dev *dev;
        sector_t physical_start;

        atomic_t error_count;
};

struct stripe_c {
        uint32_t stripes;
        int stripes_shift;

        /* The size of this target / num. stripes */
        sector_t stripe_width;

        uint32_t chunk_size;
        int chunk_size_shift;

        /* Needed for handling events */
        struct dm_target *ti;

        /* Work struct used for triggering events*/
        struct work_struct trigger_event;

        struct stripe stripe[0];
};

/*
 * An event is triggered whenever a drive
 * drops out of a stripe volume.
 */
static void trigger_event(struct work_struct *work)
{
        struct stripe_c *sc = container_of(work, struct stripe_c,
                                           trigger_event);
        dm_table_event(sc->ti->table);
}

static inline struct stripe_c *alloc_context(unsigned int stripes)
{
        size_t len;

        if (dm_array_too_big(sizeof(struct stripe_c), sizeof(struct stripe),
                             stripes))
                return NULL;

        len = sizeof(struct stripe_c) + (sizeof(struct stripe) * stripes);

        return kmalloc(len, GFP_KERNEL);
}

/*
 * Parse a single <dev> <sector> pair
 */
static int get_stripe(struct dm_target *ti, struct stripe_c *sc,
                      unsigned int stripe, char **argv)
{
        unsigned long long start;
        char dummy;

        if (sscanf(argv[1], "%llu%c", &start, &dummy) != 1)
                return -EINVAL;

        if (dm_get_device(ti, argv[0], dm_table_get_mode(ti->table),
                          &sc->stripe[stripe].dev))
                return -ENXIO;

        sc->stripe[stripe].physical_start = start;

        return 0;
}

/*
 * Construct a striped mapping.
 * <number of stripes> <chunk size> [<dev_path> <offset>]+
 */
static int stripe_ctr(struct dm_target *ti, unsigned int argc, char **argv)
{
        struct stripe_c *sc;
        sector_t width;
        uint32_t stripes;
        uint32_t chunk_size;
        int r;
        unsigned int i;

        if (argc < 2) {
                ti->error = "Not enough arguments";
                return -EINVAL;
        }

        if (kstrtouint(argv[0], 10, &stripes) || !stripes) {
                ti->error = "Invalid stripe count";
                return -EINVAL;
        }

        if (kstrtouint(argv[1], 10, &chunk_size) || !chunk_size) {
                ti->error = "Invalid chunk_size";
                return -EINVAL;
        }

        width = ti->len;
        if (sector_div(width, chunk_size)) {
                ti->error = "Target length not divisible by "
                    "chunk size";
                return -EINVAL;
        }

        if (sector_div(width, stripes)) {
                ti->error = "Target length not divisible by "
                    "number of stripes";
                return -EINVAL;
        }

        /*
         * Do we have enough arguments for that many stripes ?
         */
        if (argc != (2 + 2 * stripes)) {
                ti->error = "Not enough destinations "
                        "specified";
                return -EINVAL;
        }

        sc = alloc_context(stripes);
        if (!sc) {
                ti->error = "Memory allocation for striped context "
                    "failed";
                return -ENOMEM;
        }

        INIT_WORK(&sc->trigger_event, trigger_event);

        /* Set pointer to dm target; used in trigger_event */
        sc->ti = ti;
        sc->stripes = stripes;
        sc->stripe_width = width;

        if (stripes & (stripes - 1))
                sc->stripes_shift = -1;
        else
                sc->stripes_shift = __ffs(stripes);

        r = dm_set_target_max_io_len(ti, chunk_size);
        if (r)
                return r;

        ti->num_flush_requests = stripes;
        ti->num_discard_requests = stripes;
        ti->num_write_same_requests = stripes;

        sc->chunk_size = chunk_size;
        if (chunk_size & (chunk_size - 1))
                sc->chunk_size_shift = -1;
        else
                sc->chunk_size_shift = __ffs(chunk_size);

        /*
         * Get the stripe destinations.
         */
        for (i = 0; i < stripes; i++) {
                argv += 2;

                r = get_stripe(ti, sc, i, argv);
                if (r < 0) {
                        ti->error = "Couldn't parse stripe destination";
                        while (i--)
                                dm_put_device(ti, sc->stripe[i].dev);
                        kfree(sc);
                        return r;
                }
                atomic_set(&(sc->stripe[i].error_count), 0);
        }

        ti->private = sc;

        return 0;
}

static void stripe_dtr(struct dm_target *ti)
{
        unsigned int i;
        struct stripe_c *sc = (struct stripe_c *) ti->private;

        for (i = 0; i < sc->stripes; i++)
                dm_put_device(ti, sc->stripe[i].dev);

        flush_work(&sc->trigger_event);
        kfree(sc);
}

static void stripe_map_sector(struct stripe_c *sc, sector_t sector,
                              uint32_t *stripe, sector_t *result)
{
        sector_t chunk = dm_target_offset(sc->ti, sector);
        sector_t chunk_offset;

        if (sc->chunk_size_shift < 0)
                chunk_offset = sector_div(chunk, sc->chunk_size);
        else {
                chunk_offset = chunk & (sc->chunk_size - 1);
                chunk >>= sc->chunk_size_shift;
        }

        if (sc->stripes_shift < 0)
                *stripe = sector_div(chunk, sc->stripes);
        else {
                *stripe = chunk & (sc->stripes - 1);
                chunk >>= sc->stripes_shift;
        }

        if (sc->chunk_size_shift < 0)
                chunk *= sc->chunk_size;
        else
                chunk <<= sc->chunk_size_shift;

        *result = chunk + chunk_offset;
}

static void stripe_map_range_sector(struct stripe_c *sc, sector_t sector,
                                    uint32_t target_stripe, sector_t *result)
{
        uint32_t stripe;

        stripe_map_sector(sc, sector, &stripe, result);
        if (stripe == target_stripe)
                return;

        /* round down */
        sector = *result;
        if (sc->chunk_size_shift < 0)
                *result -= sector_div(sector, sc->chunk_size);
        else
                *result = sector & ~(sector_t)(sc->chunk_size - 1);

        if (target_stripe < stripe)
                *result += sc->chunk_size;              /* next chunk */
}

static int stripe_map_range(struct stripe_c *sc, struct bio *bio,
                            uint32_t target_stripe)
{
        sector_t begin, end;

        stripe_map_range_sector(sc, bio->bi_sector, target_stripe, &begin);
        stripe_map_range_sector(sc, bio->bi_sector + bio_sectors(bio),
                                target_stripe, &end);
        if (begin < end) {
                bio->bi_bdev = sc->stripe[target_stripe].dev->bdev;
                bio->bi_sector = begin + sc->stripe[target_stripe].physical_start;
                bio->bi_size = to_bytes(end - begin);
                return DM_MAPIO_REMAPPED;
        } else {
                /* The range doesn't map to the target stripe */
                bio_endio(bio, 0);
                return DM_MAPIO_SUBMITTED;
        }
}

static int stripe_map(struct dm_target *ti, struct bio *bio)
{
        struct stripe_c *sc = ti->private;
        uint32_t stripe;
        unsigned target_request_nr;

        if (bio->bi_rw & REQ_FLUSH) {
                target_request_nr = dm_bio_get_target_request_nr(bio);
                BUG_ON(target_request_nr >= sc->stripes);
                bio->bi_bdev = sc->stripe[target_request_nr].dev->bdev;
                return DM_MAPIO_REMAPPED;
        }
        if (unlikely(bio->bi_rw & REQ_DISCARD) ||
            unlikely(bio->bi_rw & REQ_WRITE_SAME)) {
                target_request_nr = dm_bio_get_target_request_nr(bio);
                BUG_ON(target_request_nr >= sc->stripes);
                return stripe_map_range(sc, bio, target_request_nr);
        }

        stripe_map_sector(sc, bio->bi_sector, &stripe, &bio->bi_sector);

        bio->bi_sector += sc->stripe[stripe].physical_start;
        bio->bi_bdev = sc->stripe[stripe].dev->bdev;

        return DM_MAPIO_REMAPPED;
}

/*
 * Stripe status:
 *
 * INFO
 * #stripes [stripe_name <stripe_name>] [group word count]
 * [error count 'A|D' <error count 'A|D'>]
 *
 * TABLE
 * #stripes [stripe chunk size]
 * [stripe_name physical_start <stripe_name physical_start>]
 *
 */

static int stripe_status(struct dm_target *ti, status_type_t type,
                         unsigned status_flags, char *result, unsigned maxlen)
{
        struct stripe_c *sc = (struct stripe_c *) ti->private;
        char buffer[sc->stripes + 1];
        unsigned int sz = 0;
        unsigned int i;

        switch (type) {
        case STATUSTYPE_INFO:
                DMEMIT("%d ", sc->stripes);
                for (i = 0; i < sc->stripes; i++)  {
                        DMEMIT("%s ", sc->stripe[i].dev->name);
                        buffer[i] = atomic_read(&(sc->stripe[i].error_count)) ?
                                'D' : 'A';
                }
                buffer[i] = '\0';
                DMEMIT("1 %s", buffer);
                break;

        case STATUSTYPE_TABLE:
                DMEMIT("%d %llu", sc->stripes,
                        (unsigned long long)sc->chunk_size);
                for (i = 0; i < sc->stripes; i++)
                        DMEMIT(" %s %llu", sc->stripe[i].dev->name,
                            (unsigned long long)sc->stripe[i].physical_start);
                break;
        }
        return 0;
}

static int stripe_end_io(struct dm_target *ti, struct bio *bio, int error)
{
        unsigned i;
        char major_minor[16];
        struct stripe_c *sc = ti->private;

        if (!error)
                return 0; /* I/O complete */

        if ((error == -EWOULDBLOCK) && (bio->bi_rw & REQ_RAHEAD))
                return error;

        if (error == -EOPNOTSUPP)
                return error;

        memset(major_minor, 0, sizeof(major_minor));
        sprintf(major_minor, "%d:%d",
                MAJOR(disk_devt(bio->bi_bdev->bd_disk)),
                MINOR(disk_devt(bio->bi_bdev->bd_disk)));

        /*
         * Test to see which stripe drive triggered the event
         * and increment error count for all stripes on that device.
         * If the error count for a given device exceeds the threshold
         * value we will no longer trigger any further events.
         */
        for (i = 0; i < sc->stripes; i++)
                if (!strcmp(sc->stripe[i].dev->name, major_minor)) {
                        atomic_inc(&(sc->stripe[i].error_count));
                        if (atomic_read(&(sc->stripe[i].error_count)) <
                            DM_IO_ERROR_THRESHOLD)
                                schedule_work(&sc->trigger_event);
                }

        return error;
}

static int stripe_iterate_devices(struct dm_target *ti,
                                  iterate_devices_callout_fn fn, void *data)
{
        struct stripe_c *sc = ti->private;
        int ret = 0;
        unsigned i = 0;

        do {
                ret = fn(ti, sc->stripe[i].dev,
                         sc->stripe[i].physical_start,
                         sc->stripe_width, data);
        } while (!ret && ++i < sc->stripes);

        return ret;
}

static void stripe_io_hints(struct dm_target *ti,
                            struct queue_limits *limits)
{
        struct stripe_c *sc = ti->private;
        unsigned chunk_size = sc->chunk_size << SECTOR_SHIFT;

        blk_limits_io_min(limits, chunk_size);
        blk_limits_io_opt(limits, chunk_size * sc->stripes);
}

static int stripe_merge(struct dm_target *ti, struct bvec_merge_data *bvm,
                        struct bio_vec *biovec, int max_size)
{
        struct stripe_c *sc = ti->private;
        sector_t bvm_sector = bvm->bi_sector;
        uint32_t stripe;
        struct request_queue *q;

        stripe_map_sector(sc, bvm_sector, &stripe, &bvm_sector);

        q = bdev_get_queue(sc->stripe[stripe].dev->bdev);
        if (!q->merge_bvec_fn)
                return max_size;

        bvm->bi_bdev = sc->stripe[stripe].dev->bdev;
        bvm->bi_sector = sc->stripe[stripe].physical_start + bvm_sector;

        return min(max_size, q->merge_bvec_fn(q, bvm, biovec));
}

static struct target_type stripe_target = {
        .name   = "striped",
        .version = {1, 5, 0},
        .module = THIS_MODULE,
        .ctr    = stripe_ctr,
        .dtr    = stripe_dtr,
        .map    = stripe_map,
        .end_io = stripe_end_io,
        .status = stripe_status,
        .iterate_devices = stripe_iterate_devices,
        .io_hints = stripe_io_hints,
        .merge  = stripe_merge,
};

int __init dm_stripe_init(void)
{
        int r;

        r = dm_register_target(&stripe_target);
        if (r < 0) {
                DMWARN("target registration failed");
                return r;
        }

        return r;
}

void dm_stripe_exit(void)
{
        dm_unregister_target(&stripe_target);
}