dm-log.c

Go to the documentation of this file.

/*
 * 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 rw)
{
    lc->io_req.bi_rw = rw;

    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_rw = WRITE_FLUSH;

    return dm_io(&lc->io_req, 1, &null_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 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, 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, 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 <[email protected]>");
MODULE_LICENSE("GPL");