/*
 * Copyright (C) 2003 Sistina Software
 *
 * This file is released under the LGPL.
 */

#include <linux/init.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/vmalloc.h>

#include "dm-log.h"
#include "dm-io.h"

#define DM_MSG_PREFIX "mirror log"

static LIST_HEAD(_log_types);
static DEFINE_SPINLOCK(_lock);

int dm_register_dirty_log_type(struct dirty_log_type *type)
{
        spin_lock(&_lock);
        type->use_count = 0;
        list_add(&type->list, &_log_types);
        spin_unlock(&_lock);

        return 0;
}

int dm_unregister_dirty_log_type(struct dirty_log_type *type)
{
        spin_lock(&_lock);

        if (type->use_count)
                DMWARN("Attempt to unregister a log type that is still in use");
        else
                list_del(&type->list);

        spin_unlock(&_lock);

        return 0;
}

static struct dirty_log_type *get_type(const char *type_name)
{
        struct dirty_log_type *type;

        spin_lock(&_lock);
        list_for_each_entry (type, &_log_types, list)
                if (!strcmp(type_name, type->name)) {
                        if (!type->use_count && !try_module_get(type->module)){
                                spin_unlock(&_lock);
                                return NULL;
                        }
                        type->use_count++;
                        spin_unlock(&_lock);
                        return type;
                }

        spin_unlock(&_lock);
        return NULL;
}

static void put_type(struct dirty_log_type *type)
{
        spin_lock(&_lock);
        if (!--type->use_count)
                module_put(type->module);
        spin_unlock(&_lock);
}

struct dirty_log *dm_create_dirty_log(const char *type_name, struct dm_target *ti,
                                      unsigned int argc, char **argv)
{
        struct dirty_log_type *type;
        struct dirty_log *log;

        log = kmalloc(sizeof(*log), GFP_KERNEL);
        if (!log)
                return NULL;

        type = get_type(type_name);
        if (!type) {
                kfree(log);
                return NULL;
        }

        log->type = type;
        if (type->ctr(log, ti, argc, argv)) {
                kfree(log);
                put_type(type);
                return NULL;
        }

        return log;
}

void dm_destroy_dirty_log(struct dirty_log *log)
{
        log->type->dtr(log);
        put_type(log->type);
        kfree(log);
}

/*-----------------------------------------------------------------
 * Persistent and core logs share a lot of their implementation.
 * FIXME: need a reload method to be called from a resume
 *---------------------------------------------------------------*/
/*
 * Magic for persistent mirrors: "MiRr"
 */
#define MIRROR_MAGIC 0x4D695272

/*
 * The on-disk version of the metadata.
 */
#define MIRROR_DISK_VERSION 2
#define LOG_OFFSET 2

struct log_header {
        uint32_t magic;

        /*
         * Simple, incrementing version. no backward
         * compatibility.
         */
        uint32_t version;
        sector_t nr_regions;
};

struct log_c {
        struct dm_target *ti;
        int touched;
        uint32_t region_size;
        unsigned int region_count;
        region_t sync_count;

        unsigned bitset_uint32_count;
        uint32_t *clean_bits;
        uint32_t *sync_bits;
        uint32_t *recovering_bits;      /* FIXME: this seems excessive */

        int sync_search;

        /* Resync flag */
        enum sync {
                DEFAULTSYNC,    /* Synchronize if necessary */
                NOSYNC,         /* Devices known to be already in sync */
                FORCESYNC,      /* Force a sync to happen */
        } sync;

        struct dm_io_request io_req;

        /*
         * Disk log fields
         */
        int log_dev_failed;
        struct dm_dev *log_dev;
        struct log_header header;

        struct io_region header_location;
        struct log_header *disk_header;
};

/*
 * The touched member needs to be updated every time we access
 * one of the bitsets.
 */
static  inline int log_test_bit(uint32_t *bs, unsigned bit)
{
        return ext2_test_bit(bit, (unsigned long *) bs) ? 1 : 0;
}

static inline void log_set_bit(struct log_c *l,
                               uint32_t *bs, unsigned bit)
{
        ext2_set_bit(bit, (unsigned long *) bs);
        l->touched = 1;
}

static inline void log_clear_bit(struct log_c *l,
                                 uint32_t *bs, unsigned bit)
{
        ext2_clear_bit(bit, (unsigned long *) bs);
        l->touched = 1;
}

/*----------------------------------------------------------------
 * Header IO
 *--------------------------------------------------------------*/
static void header_to_disk(struct log_header *core, struct log_header *disk)
{
        disk->magic = cpu_to_le32(core->magic);
        disk->version = cpu_to_le32(core->version);
        disk->nr_regions = cpu_to_le64(core->nr_regions);
}

static void header_from_disk(struct log_header *core, struct log_header *disk)
{
        core->magic = le32_to_cpu(disk->magic);
        core->version = le32_to_cpu(disk->version);
        core->nr_regions = le64_to_cpu(disk->nr_regions);
}

static int rw_header(struct log_c *lc, int rw)
{
        lc->io_req.bi_rw = rw;
        lc->io_req.mem.ptr.vma = lc->disk_header;
        lc->io_req.notify.fn = NULL;

        return dm_io(&lc->io_req, 1, &lc->header_location, NULL);
}

static int read_header(struct log_c *log)
{
        int r;

        r = rw_header(log, READ);
        if (r)
                return r;

        header_from_disk(&log->header, log->disk_header);

        /* New log required? */
        if (log->sync != DEFAULTSYNC || log->header.magic != MIRROR_MAGIC) {
                log->header.magic = MIRROR_MAGIC;
                log->header.version = MIRROR_DISK_VERSION;
                log->header.nr_regions = 0;
        }

#ifdef __LITTLE_ENDIAN
        if (log->header.version == 1)
                log->header.version = 2;
#endif

        if (log->header.version != MIRROR_DISK_VERSION) {
                DMWARN("incompatible disk log version");
                return -EINVAL;
        }

        return 0;
}

static inline int write_header(struct log_c *log)
{
        header_to_disk(&log->header, log->disk_header);
        return rw_header(log, WRITE);
}

/*----------------------------------------------------------------
 * core log constructor/destructor
 *
 * argv contains region_size followed optionally by [no]sync
 *--------------------------------------------------------------*/
#define BYTE_SHIFT 3
static int create_log_context(struct dirty_log *log, struct dm_target *ti,
                              unsigned int argc, char **argv,
                              struct dm_dev *dev)
{
        enum sync sync = DEFAULTSYNC;

        struct log_c *lc;
        uint32_t region_size;
        unsigned int region_count;
        size_t bitset_size, buf_size;
        int r;

        if (argc < 1 || argc > 2) {
                DMWARN("wrong number of arguments to mirror log");
                return -EINVAL;
        }

        if (argc > 1) {
                if (!strcmp(argv[1], "sync"))
                        sync = FORCESYNC;
                else if (!strcmp(argv[1], "nosync"))
                        sync = NOSYNC;
                else {
                        DMWARN("unrecognised sync argument to mirror log: %s",
                               argv[1]);
                        return -EINVAL;
                }
        }

        if (sscanf(argv[0], "%u", &region_size) != 1) {
                DMWARN("invalid region size string");
                return -EINVAL;
        }

        region_count = dm_sector_div_up(ti->len, region_size);

        lc = kmalloc(sizeof(*lc), GFP_KERNEL);
        if (!lc) {
                DMWARN("couldn't allocate core log");
                return -ENOMEM;
        }

        lc->ti = ti;
        lc->touched = 0;
        lc->region_size = region_size;
        lc->region_count = region_count;
        lc->sync = sync;

        /*
         * Work out how many "unsigned long"s we need to hold the bitset.
         */
        bitset_size = dm_round_up(region_count,
                                  sizeof(*lc->clean_bits) << BYTE_SHIFT);
        bitset_size >>= BYTE_SHIFT;

        lc->bitset_uint32_count = bitset_size / sizeof(*lc->clean_bits);

        /*
         * Disk log?
         */
        if (!dev) {
                lc->clean_bits = vmalloc(bitset_size);
                if (!lc->clean_bits) {
                        DMWARN("couldn't allocate clean bitset");
                        kfree(lc);
                        return -ENOMEM;
                }
                lc->disk_header = NULL;
        } else {
                lc->log_dev = dev;
                lc->log_dev_failed = 0;
                lc->header_location.bdev = lc->log_dev->bdev;
                lc->header_location.sector = 0;

                /*
                 * Buffer holds both header and bitset.
                 */
                buf_size = dm_round_up((LOG_OFFSET << SECTOR_SHIFT) +
                                       bitset_size, ti->limits.hardsect_size);
                lc->header_location.count = buf_size >> SECTOR_SHIFT;
                lc->io_req.mem.type = DM_IO_VMA;
                lc->io_req.client = dm_io_client_create(dm_div_up(buf_size,
                                                                   PAGE_SIZE));
                if (IS_ERR(lc->io_req.client)) {
                        r = PTR_ERR(lc->io_req.client);
                        DMWARN("couldn't allocate disk io client");
                        kfree(lc);
                        return -ENOMEM;
                }

                lc->disk_header = vmalloc(buf_size);
                if (!lc->disk_header) {
                        DMWARN("couldn't allocate disk log buffer");
                        kfree(lc);
                        return -ENOMEM;
                }

                lc->clean_bits = (void *)lc->disk_header +
                                 (LOG_OFFSET << SECTOR_SHIFT);
        }

        memset(lc->clean_bits, -1, bitset_size);

        lc->sync_bits = vmalloc(bitset_size);
        if (!lc->sync_bits) {
                DMWARN("couldn't allocate sync bitset");
                if (!dev)
                        vfree(lc->clean_bits);
                vfree(lc->disk_header);
                kfree(lc);
                return -ENOMEM;
        }
        memset(lc->sync_bits, (sync == NOSYNC) ? -1 : 0, bitset_size);
        lc->sync_count = (sync == NOSYNC) ? region_count : 0;

        lc->recovering_bits = vmalloc(bitset_size);
        if (!lc->recovering_bits) {
                DMWARN("couldn't allocate sync bitset");
                vfree(lc->sync_bits);
                if (!dev)
                        vfree(lc->clean_bits);
                vfree(lc->disk_header);
                kfree(lc);
                return -ENOMEM;
        }
        memset(lc->recovering_bits, 0, bitset_size);
        lc->sync_search = 0;
        log->context = lc;

        return 0;
}

static int core_ctr(struct dirty_log *log, struct dm_target *ti,
                    unsigned int argc, char **argv)
{
        return create_log_context(log, ti, argc, argv, NULL);
}

static void destroy_log_context(struct log_c *lc)
{
        vfree(lc->sync_bits);
        vfree(lc->recovering_bits);
        kfree(lc);
}

static void core_dtr(struct dirty_log *log)
{
        struct log_c *lc = (struct log_c *) log->context;

        vfree(lc->clean_bits);
        destroy_log_context(lc);
}

/*----------------------------------------------------------------
 * disk log constructor/destructor
 *
 * argv contains log_device region_size followed optionally by [no]sync
 *--------------------------------------------------------------*/
static int disk_ctr(struct dirty_log *log, struct dm_target *ti,
                    unsigned int argc, char **argv)
{
        int r;
        struct dm_dev *dev;

        if (argc < 2 || argc > 3) {
                DMWARN("wrong number of arguments to disk mirror log");
                return -EINVAL;
        }

        r = dm_get_device(ti, argv[0], 0, 0 /* FIXME */,
                          FMODE_READ | FMODE_WRITE, &dev);
        if (r)
                return r;

        r = create_log_context(log, ti, argc - 1, argv + 1, dev);
        if (r) {
                dm_put_device(ti, dev);
                return r;
        }

        return 0;
}

static void disk_dtr(struct dirty_log *log)
{
        struct log_c *lc = (struct log_c *) log->context;

        dm_put_device(lc->ti, lc->log_dev);
        vfree(lc->disk_header);
        dm_io_client_destroy(lc->io_req.client);
        destroy_log_context(lc);
}

static int count_bits32(uint32_t *addr, unsigned size)
{
        int count = 0, i;

        for (i = 0; i < size; i++) {
                count += hweight32(*(addr+i));
        }
        return count;
}

static void fail_log_device(struct log_c *lc)
{
        if (lc->log_dev_failed)
                return;

        lc->log_dev_failed = 1;
        dm_table_event(lc->ti->table);
}

static int disk_resume(struct dirty_log *log)
{
        int r;
        unsigned i;
        struct log_c *lc = (struct log_c *) log->context;
        size_t size = lc->bitset_uint32_count * sizeof(uint32_t);

        /* read the disk header */
        r = read_header(lc);
        if (r) {
                DMWARN("%s: Failed to read header on mirror log device",
                       lc->log_dev->name);
                fail_log_device(lc);
                /*
                 * If the log device cannot be read, we must assume
                 * all regions are out-of-sync.  If we simply return
                 * here, the state will be uninitialized and could
                 * lead us to return 'in-sync' status for regions
                 * that are actually 'out-of-sync'.
                 */
                lc->header.nr_regions = 0;
        }

        /* set or clear any new bits -- device has grown */
        if (lc->sync == NOSYNC)
                for (i = lc->header.nr_regions; i < lc->region_count; i++)
                        /* FIXME: amazingly inefficient */
                        log_set_bit(lc, lc->clean_bits, i);
        else
                for (i = lc->header.nr_regions; i < lc->region_count; i++)
                        /* FIXME: amazingly inefficient */
                        log_clear_bit(lc, lc->clean_bits, i);

        /* clear any old bits -- device has shrunk */
        for (i = lc->region_count; i % (sizeof(*lc->clean_bits) << BYTE_SHIFT); i++)
                log_clear_bit(lc, lc->clean_bits, i);

        /* copy clean across to sync */
        memcpy(lc->sync_bits, lc->clean_bits, size);
        lc->sync_count = count_bits32(lc->clean_bits, lc->bitset_uint32_count);
        lc->sync_search = 0;

        /* set the correct number of regions in the header */
        lc->header.nr_regions = lc->region_count;

        /* write the new header */
        r = write_header(lc);
        if (r) {
                DMWARN("%s: Failed to write header on mirror log device",
                       lc->log_dev->name);
                fail_log_device(lc);
        }

        return r;
}

static uint32_t core_get_region_size(struct dirty_log *log)
{
        struct log_c *lc = (struct log_c *) log->context;
        return lc->region_size;
}

static int core_resume(struct dirty_log *log)
{
        struct log_c *lc = (struct log_c *) log->context;
        lc->sync_search = 0;
        return 0;
}

static int core_is_clean(struct dirty_log *log, region_t region)
{
        struct log_c *lc = (struct log_c *) log->context;
        return log_test_bit(lc->clean_bits, region);
}

static int core_in_sync(struct dirty_log *log, region_t region, int block)
{
        struct log_c *lc = (struct log_c *) log->context;
        return log_test_bit(lc->sync_bits, region);
}

static int core_flush(struct dirty_log *log)
{
        /* no op */
        return 0;
}

static int disk_flush(struct dirty_log *log)
{
        int r;
        struct log_c *lc = (struct log_c *) log->context;

        /* only write if the log has changed */
        if (!lc->touched)
                return 0;

        r = write_header(lc);
        if (r)
                fail_log_device(lc);
        else
                lc->touched = 0;

        return r;
}

static void core_mark_region(struct dirty_log *log, region_t region)
{
        struct log_c *lc = (struct log_c *) log->context;
        log_clear_bit(lc, lc->clean_bits, region);
}

static void core_clear_region(struct dirty_log *log, region_t region)
{
        struct log_c *lc = (struct log_c *) log->context;
        log_set_bit(lc, lc->clean_bits, region);
}

static int core_get_resync_work(struct dirty_log *log, region_t *region)
{
        struct log_c *lc = (struct log_c *) log->context;

        if (lc->sync_search >= lc->region_count)
                return 0;

        do {
                *region = ext2_find_next_zero_bit(
                                             (unsigned long *) lc->sync_bits,
                                             lc->region_count,
                                             lc->sync_search);
                lc->sync_search = *region + 1;

                if (*region >= lc->region_count)
                        return 0;

        } while (log_test_bit(lc->recovering_bits, *region));

        log_set_bit(lc, lc->recovering_bits, *region);
        return 1;
}

static void core_set_region_sync(struct dirty_log *log, region_t region,
                                 int in_sync)
{
        struct log_c *lc = (struct log_c *) log->context;

        log_clear_bit(lc, lc->recovering_bits, region);
        if (in_sync) {
                log_set_bit(lc, lc->sync_bits, region);
                lc->sync_count++;
        } else if (log_test_bit(lc->sync_bits, region)) {
                lc->sync_count--;
                log_clear_bit(lc, lc->sync_bits, region);
        }
}

static region_t core_get_sync_count(struct dirty_log *log)
{
        struct log_c *lc = (struct log_c *) log->context;

        return lc->sync_count;
}

#define DMEMIT_SYNC \
        if (lc->sync != DEFAULTSYNC) \
                DMEMIT("%ssync ", lc->sync == NOSYNC ? "no" : "")

static int core_status(struct dirty_log *log, status_type_t status,
                       char *result, unsigned int maxlen)
{
        int sz = 0;
        struct log_c *lc = log->context;

        switch(status) {
        case STATUSTYPE_INFO:
                DMEMIT("1 %s", log->type->name);
                break;

        case STATUSTYPE_TABLE:
                DMEMIT("%s %u %u ", log->type->name,
                       lc->sync == DEFAULTSYNC ? 1 : 2, lc->region_size);
                DMEMIT_SYNC;
        }

        return sz;
}

static int disk_status(struct dirty_log *log, status_type_t status,
                       char *result, unsigned int maxlen)
{
        int sz = 0;
        struct log_c *lc = log->context;

        switch(status) {
        case STATUSTYPE_INFO:
                DMEMIT("3 %s %s %c", log->type->name, lc->log_dev->name,
                       lc->log_dev_failed ? 'D' : 'A');
                break;

        case STATUSTYPE_TABLE:
                DMEMIT("%s %u %s %u ", log->type->name,
                       lc->sync == DEFAULTSYNC ? 2 : 3, lc->log_dev->name,
                       lc->region_size);
                DMEMIT_SYNC;
        }

        return sz;
}

static struct dirty_log_type _core_type = {
        .name = "core",
        .module = THIS_MODULE,
        .ctr = core_ctr,
        .dtr = core_dtr,
        .resume = core_resume,
        .get_region_size = core_get_region_size,
        .is_clean = core_is_clean,
        .in_sync = core_in_sync,
        .flush = core_flush,
        .mark_region = core_mark_region,
        .clear_region = core_clear_region,
        .get_resync_work = core_get_resync_work,
        .set_region_sync = core_set_region_sync,
        .get_sync_count = core_get_sync_count,
        .status = core_status,
};

static struct dirty_log_type _disk_type = {
        .name = "disk",
        .module = THIS_MODULE,
        .ctr = disk_ctr,
        .dtr = disk_dtr,
        .postsuspend = disk_flush,
        .resume = disk_resume,
        .get_region_size = core_get_region_size,
        .is_clean = core_is_clean,
        .in_sync = core_in_sync,
        .flush = disk_flush,
        .mark_region = core_mark_region,
        .clear_region = core_clear_region,
        .get_resync_work = core_get_resync_work,
        .set_region_sync = core_set_region_sync,
        .get_sync_count = core_get_sync_count,
        .status = disk_status,
};

int __init dm_dirty_log_init(void)
{
        int r;

        r = dm_register_dirty_log_type(&_core_type);
        if (r)
                DMWARN("couldn't register core log");

        r = dm_register_dirty_log_type(&_disk_type);
        if (r) {
                DMWARN("couldn't register disk type");
                dm_unregister_dirty_log_type(&_core_type);
        }

        return r;
}

void dm_dirty_log_exit(void)
{
        dm_unregister_dirty_log_type(&_disk_type);
        dm_unregister_dirty_log_type(&_core_type);
}

EXPORT_SYMBOL(dm_register_dirty_log_type);
EXPORT_SYMBOL(dm_unregister_dirty_log_type);
EXPORT_SYMBOL(dm_create_dirty_log);
EXPORT_SYMBOL(dm_destroy_dirty_log);