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dm-log.c

/*
 * 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);

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