/*
 * Copyright (C) 2003 Sistina Software
 * Copyright (C) 2004-2008 Red Hat, Inc. All rights reserved.
 *
 * This file is released under the LGPL.
 */

#include <linux/init.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/vmalloc.h>
#include <linux/dm-io.h>
#include <linux/dm-dirty-log.h>

#include <linux/device-mapper.h>

#define DM_MSG_PREFIX "dirty region log"

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

static struct dm_dirty_log_type *__find_dirty_log_type(const char *name)
{
        struct dm_dirty_log_type *log_type;

        list_for_each_entry(log_type, &_log_types, list)
                if (!strcmp(name, log_type->name))
                        return log_type;

        return NULL;
}

static struct dm_dirty_log_type *_get_dirty_log_type(const char *name)
{
        struct dm_dirty_log_type *log_type;

        spin_lock(&_lock);

        log_type = __find_dirty_log_type(name);
        if (log_type && !try_module_get(log_type->module))
                log_type = NULL;

        spin_unlock(&_lock);

        return log_type;
}

/*
 * get_type
 * @type_name
 *
 * Attempt to retrieve the dm_dirty_log_type by name.  If not already
 * available, attempt to load the appropriate module.
 *
 * Log modules are named "dm-log-" followed by the 'type_name'.
 * Modules may contain multiple types.
 * This function will first try the module "dm-log-<type_name>",
 * then truncate 'type_name' on the last '-' and try again.
 *
 * For example, if type_name was "clustered-disk", it would search
 * 'dm-log-clustered-disk' then 'dm-log-clustered'.
 *
 * Returns: dirty_log_type* on success, NULL on failure
 */
static struct dm_dirty_log_type *get_type(const char *type_name)
{
        char *p, *type_name_dup;
        struct dm_dirty_log_type *log_type;

        if (!type_name)
                return NULL;

        log_type = _get_dirty_log_type(type_name);
        if (log_type)
                return log_type;

        type_name_dup = kstrdup(type_name, GFP_KERNEL);
        if (!type_name_dup) {
                DMWARN("No memory left to attempt log module load for \"%s\"",
                       type_name);
                return NULL;
        }

        while (request_module("dm-log-%s", type_name_dup) ||
               !(log_type = _get_dirty_log_type(type_name))) {
                p = strrchr(type_name_dup, '-');
                if (!p)
                        break;
                p[0] = '\0';
        }

        if (!log_type)
                DMWARN("Module for logging type \"%s\" not found.", type_name);

        kfree(type_name_dup);

        return log_type;
}

static void put_type(struct dm_dirty_log_type *type)
{
        if (!type)
                return;

        spin_lock(&_lock);
        if (!__find_dirty_log_type(type->name))
                goto out;

        module_put(type->module);

out:
        spin_unlock(&_lock);
}

int dm_dirty_log_type_register(struct dm_dirty_log_type *type)
{
        int r = 0;

        spin_lock(&_lock);
        if (!__find_dirty_log_type(type->name))
                list_add(&type->list, &_log_types);
        else
                r = -EEXIST;
        spin_unlock(&_lock);

        return r;
}
EXPORT_SYMBOL(dm_dirty_log_type_register);

int dm_dirty_log_type_unregister(struct dm_dirty_log_type *type)
{
        spin_lock(&_lock);

        if (!__find_dirty_log_type(type->name)) {
                spin_unlock(&_lock);
                return -EINVAL;
        }

        list_del(&type->list);

        spin_unlock(&_lock);

        return 0;
}
EXPORT_SYMBOL(dm_dirty_log_type_unregister);

struct dm_dirty_log *dm_dirty_log_create(const char *type_name,
                        struct dm_target *ti,
                        int (*flush_callback_fn)(struct dm_target *ti),
                        unsigned int argc, char **argv)
{
        struct dm_dirty_log_type *type;
        struct dm_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->flush_callback_fn = flush_callback_fn;
        log->type = type;
        if (type->ctr(log, ti, argc, argv)) {
                kfree(log);
                put_type(type);
                return NULL;
        }

        return log;
}
EXPORT_SYMBOL(dm_dirty_log_create);

void dm_dirty_log_destroy(struct dm_dirty_log *log)
{
        log->type->dtr(log);
        put_type(log->type);
        kfree(log);
}
EXPORT_SYMBOL(dm_dirty_log_destroy);

/*-----------------------------------------------------------------
 * 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_disk {
        __le32 magic;

        /*
         * Simple, incrementing version. no backward
         * compatibility.
         */
        __le32 version;
        __le64 nr_regions;
} __packed;

struct log_header_core {
        uint32_t magic;
        uint32_t version;
        uint64_t nr_regions;
};

struct log_c {
        struct dm_target *ti;
        int touched_dirtied;
        int touched_cleaned;
        int flush_failed;
        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;
        int log_dev_flush_failed;
        struct dm_dev *log_dev;
        struct log_header_core header;

        struct dm_io_region header_location;
        struct log_header_disk *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 test_bit_le(bit, bs) ? 1 : 0;
}

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

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

/*----------------------------------------------------------------
 * Header IO
 *--------------------------------------------------------------*/
static void header_to_disk(struct log_header_core *core, struct log_header_disk *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 *core, struct log_header_disk *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 op)
{
        lc->io_req.bi_op = op;
        lc->io_req.bi_op_flags = 0;

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

static int flush_header(struct log_c *lc)
{
        struct dm_io_region null_location = {
                .bdev = lc->header_location.bdev,
                .sector = 0,
                .count = 0,
        };

        lc->io_req.bi_op = REQ_OP_WRITE;
        lc->io_req.bi_op_flags = REQ_PREFLUSH;

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

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

        r = rw_header(log, REQ_OP_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 int _check_region_size(struct dm_target *ti, uint32_t region_size)
{
        if (region_size < 2 || region_size > ti->len)
                return 0;

        if (!is_power_of_2(region_size))
                return 0;

        return 1;
}

/*----------------------------------------------------------------
 * core log constructor/destructor
 *
 * argv contains region_size followed optionally by [no]sync
 *--------------------------------------------------------------*/
#define BYTE_SHIFT 3
static int create_log_context(struct dm_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;
        char dummy;

        if (argc < 1 || argc > 2) {
                DMWARN("wrong number of arguments to dirty region 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 "
                               "dirty region log: %s", argv[1]);
                        return -EINVAL;
                }
        }

        if (sscanf(argv[0], "%u%c", &region_size, &dummy) != 1 ||
            !_check_region_size(ti, region_size)) {
                DMWARN("invalid region size %s", argv[0]);
                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_dirtied = 0;
        lc->touched_cleaned = 0;
        lc->flush_failed = 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->log_dev_flush_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,
                                bdev_logical_block_size(lc->header_location.
                                                            bdev));

                if (buf_size > i_size_read(dev->bdev->bd_inode)) {
                        DMWARN("log device %s too small: need %llu bytes",
                                dev->name, (unsigned long long)buf_size);
                        kfree(lc);
                        return -EINVAL;
                }

                lc->header_location.count = buf_size >> SECTOR_SHIFT;

                lc->io_req.mem.type = DM_IO_VMA;
                lc->io_req.notify.fn = NULL;
                lc->io_req.client = dm_io_client_create();
                if (IS_ERR(lc->io_req.client)) {
                        r = PTR_ERR(lc->io_req.client);
                        DMWARN("couldn't allocate disk io client");
                        kfree(lc);
                        return r;
                }

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

                lc->io_req.mem.ptr.vma = lc->disk_header;
                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);
                else
                        dm_io_client_destroy(lc->io_req.client);
                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 = vzalloc(bitset_size);
        if (!lc->recovering_bits) {
                DMWARN("couldn't allocate sync bitset");
                vfree(lc->sync_bits);
                if (!dev)
                        vfree(lc->clean_bits);
                else
                        dm_io_client_destroy(lc->io_req.client);
                vfree(lc->disk_header);
                kfree(lc);
                return -ENOMEM;
        }
        lc->sync_search = 0;
        log->context = lc;

        return 0;
}

static int core_ctr(struct dm_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 dm_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 dm_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 dirty region log");
                return -EINVAL;
        }

        r = dm_get_device(ti, argv[0], dm_table_get_mode(ti->table), &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 dm_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 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 dm_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 dirty region 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 = memweight(lc->clean_bits,
                                lc->bitset_uint32_count * sizeof(uint32_t));
        lc->sync_search = 0;

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

        header_to_disk(&lc->header, lc->disk_header);

        /* write the new header */
        r = rw_header(lc, REQ_OP_WRITE);
        if (!r) {
                r = flush_header(lc);
                if (r)
                        lc->log_dev_flush_failed = 1;
        }
        if (r) {
                DMWARN("%s: Failed to write header on dirty region log device",
                       lc->log_dev->name);
                fail_log_device(lc);
        }

        return r;
}

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

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

static int core_is_clean(struct dm_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 dm_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 dm_dirty_log *log)
{
        /* no op */
        return 0;
}

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

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

        if (lc->touched_cleaned && log->flush_callback_fn &&
            log->flush_callback_fn(lc->ti)) {
                /*
                 * At this point it is impossible to determine which
                 * regions are clean and which are dirty (without
                 * re-reading the log off disk). So mark all of them
                 * dirty.
                 */
                lc->flush_failed = 1;
                for (i = 0; i < lc->region_count; i++)
                        log_clear_bit(lc, lc->clean_bits, i);
        }

        r = rw_header(lc, REQ_OP_WRITE);
        if (r)
                fail_log_device(lc);
        else {
                if (lc->touched_dirtied) {
                        r = flush_header(lc);
                        if (r) {
                                lc->log_dev_flush_failed = 1;
                                fail_log_device(lc);
                        } else
                                lc->touched_dirtied = 0;
                }
                lc->touched_cleaned = 0;
        }

        return r;
}

static void core_mark_region(struct dm_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 dm_dirty_log *log, region_t region)
{
        struct log_c *lc = (struct log_c *) log->context;
        if (likely(!lc->flush_failed))
                log_set_bit(lc, lc->clean_bits, region);
}

static int core_get_resync_work(struct dm_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 = find_next_zero_bit_le(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 dm_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 dm_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 dm_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 dm_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_flush_failed ? 'F' :
                       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 dm_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 dm_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,
};

static int __init dm_dirty_log_init(void)
{
        int r;

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

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

        return r;
}

static void __exit dm_dirty_log_exit(void)
{
        dm_dirty_log_type_unregister(&_disk_type);
        dm_dirty_log_type_unregister(&_core_type);
}

module_init(dm_dirty_log_init);
module_exit(dm_dirty_log_exit);

MODULE_DESCRIPTION(DM_NAME " dirty region log");
MODULE_AUTHOR("Joe Thornber, Heinz Mauelshagen <dm-devel@redhat.com>");
MODULE_LICENSE("GPL");