Persistent log for mirroring.  Compiles but not run yet.
--- diff/drivers/md/dm-log.c	2003-11-26 10:18:32.000000000 +0000
+++ source/drivers/md/dm-log.c	2003-12-10 13:34:26.000000000 +0000
@@ -69,7 +69,7 @@
 	spin_unlock(&_lock);
 }
 
-struct dirty_log *dm_create_dirty_log(const char *type_name, sector_t dev_size,
+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;
@@ -86,7 +86,7 @@
 	}
 
 	log->type = type;
-	if (type->ctr(log, dev_size, argc, argv)) {
+	if (type->ctr(log, ti, argc, argv)) {
 		kfree(log);
 		put_type(type);
 		return NULL;
@@ -102,37 +102,193 @@
 	kfree(log);
 }
 
-
 /*-----------------------------------------------------------------
- * In core log, ie. trivial, non-persistent
- *
- * For now we'll keep this simple and just have 2 bitsets, one
- * for clean/dirty, the other for sync/nosync.  The sync bitset
- * will be freed when everything is in sync.
- *
- * FIXME: problems with a 64bit sector_t
+ * Persistent and core logs share a lot of their implementation.
+ * FIXME: need a reload method to be called from a resume
  *---------------------------------------------------------------*/
-struct core_log {
+/*
+ * Magic for persistent mirrors: "MiRr"
+ */
+#define MIRROR_MAGIC 0x4D695272
+
+/*
+ * The on-disk version of the metadata.
+ */
+#define MIRROR_DISK_VERSION 1
+#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;
 	sector_t region_size;
 	unsigned int region_count;
-	unsigned long *clean_bits;
-	unsigned long *sync_bits;
-	unsigned long *recovering_bits;	/* FIXME: this seems excessive */
+
+	unsigned bitset_uint32_count;
+	uint32_t *clean_bits;
+	uint32_t *sync_bits;
+	uint32_t *recovering_bits;	/* FIXME: this seems excessive */
 
 	int sync_search;
+
+	/*
+	 * Disk log fields
+	 */
+	struct dm_dev *log_dev;
+	struct log_header header;
+
+	struct io_region header_location;
+	struct page *header_pages;
+	struct log_header *disk_header;
+
+	struct io_region bits_location;
+	struct page *bits_pages;
+	uint32_t *disk_bits;
 };
 
+/*
+ * 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(bit, (unsigned long *) bs) ? 1 : 0;
+}
+
+static inline void log_set_bit(struct log_c *l,
+			       uint32_t *bs, unsigned bit)
+{
+	set_bit(bit, (unsigned long *) bs);
+	l->touched = 1;
+}
+
+static inline void log_clear_bit(struct log_c *l,
+				 uint32_t *bs, unsigned bit)
+{
+	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 read_header(struct log_c *log)
+{
+	int r;
+	unsigned long ebits;
+
+	r = dm_io_sync(1, &log->header_location, READ,
+		       log->header_pages, 0, &ebits);
+	if (r)
+		return r;
+
+	header_from_disk(&log->header, log->disk_header);
+
+	if (log->header.magic != MIRROR_MAGIC) {
+		log->header.magic = MIRROR_MAGIC;
+		log->header.version = MIRROR_DISK_VERSION;
+		log->header.nr_regions = 0;
+	}
+
+	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)
+{
+	unsigned long ebits;
+
+	header_to_disk(&log->header, log->disk_header);
+	return dm_io_sync(1, &log->header_location, WRITE,
+			  log->header_pages, 0, &ebits);
+}
+
+/*----------------------------------------------------------------
+ * Bits IO
+ *--------------------------------------------------------------*/
+static inline void bits_to_core(uint32_t *core, uint32_t *disk, unsigned count)
+{
+	unsigned i;
+
+	for (i = 0; i < count; i++)
+		core[i] = le32_to_cpu(disk[i]);
+}
+
+static inline void bits_to_disk(uint32_t *core, uint32_t *disk, unsigned count)
+{
+	unsigned i;
+
+	/* copy across the clean/dirty bitset */
+	for (i = 0; i < i; i++)
+		disk[i] = cpu_to_le32(core[i]);
+}
+
+static int read_bits(struct log_c *log)
+{
+	int r;
+	unsigned long ebits;
+
+	r = dm_io_sync(1, &log->bits_location, READ,
+		       log->bits_pages, 0, &ebits);
+	if (r)
+		return r;
+
+	bits_to_core(log->clean_bits, log->disk_bits,
+		     log->bitset_uint32_count);
+	return 0;
+}
+
+static int write_bits(struct log_c *log)
+{
+	unsigned long ebits;
+	bits_to_disk(log->clean_bits, log->disk_bits,
+		     log->bitset_uint32_count);
+	return dm_io_sync(1, &log->bits_location, WRITE,
+			  log->bits_pages, 0, &ebits);
+}
+
+/*----------------------------------------------------------------
+ * constructor/destructor
+ *--------------------------------------------------------------*/
 #define BYTE_SHIFT 3
-static int core_ctr(struct dirty_log *log, sector_t dev_size,
+static int core_ctr(struct dirty_log *log, struct dm_target *ti,
 		    unsigned int argc, char **argv)
 {
-	struct core_log *clog;
+	struct log_c *lc;
 	sector_t region_size;
 	unsigned int region_count;
 	size_t bitset_size;
 
 	if (argc != 1) {
-		DMWARN("wrong number of arguments to core_log");
+		DMWARN("wrong number of arguments to log_c");
 		return -EINVAL;
 	}
 
@@ -141,81 +297,182 @@
 		return -EINVAL;
 	}
 
-	region_count = dm_div_up(dev_size, region_size);
+	region_count = dm_div_up(ti->len, region_size);
 
-	clog = kmalloc(sizeof(*clog), GFP_KERNEL);
-	if (!clog) {
+	lc = kmalloc(sizeof(*lc), GFP_KERNEL);
+	if (!lc) {
 		DMWARN("couldn't allocate core log");
 		return -ENOMEM;
 	}
 
-	clog->region_size = region_size;
-	clog->region_count = region_count;
+	lc->ti = ti;
+	lc->touched = 0;
+	lc->region_size = region_size;
+	lc->region_count = region_count;
 
 	/*
 	 * Work out how many words we need to hold the bitset.
 	 */
 	bitset_size = dm_round_up(region_count,
-				  sizeof(*clog->clean_bits) << BYTE_SHIFT);
+				  sizeof(*lc->clean_bits) << BYTE_SHIFT);
 	bitset_size >>= BYTE_SHIFT;
 
-	clog->clean_bits = vmalloc(bitset_size);
-	if (!clog->clean_bits) {
+	lc->bitset_uint32_count = bitset_size / 4;
+	lc->clean_bits = vmalloc(bitset_size);
+	if (!lc->clean_bits) {
 		DMWARN("couldn't allocate clean bitset");
-		kfree(clog);
+		kfree(lc);
 		return -ENOMEM;
 	}
-	memset(clog->clean_bits, -1, bitset_size);
+	memset(lc->clean_bits, -1, bitset_size);
 
-	clog->sync_bits = vmalloc(bitset_size);
-	if (!clog->sync_bits) {
+	lc->sync_bits = vmalloc(bitset_size);
+	if (!lc->sync_bits) {
 		DMWARN("couldn't allocate sync bitset");
-		vfree(clog->clean_bits);
-		kfree(clog);
+		vfree(lc->clean_bits);
+		kfree(lc);
 		return -ENOMEM;
 	}
-	memset(clog->sync_bits, 0, bitset_size);
+	memset(lc->sync_bits, 0, bitset_size);
 
-	clog->recovering_bits = vmalloc(bitset_size);
-	if (!clog->recovering_bits) {
+	lc->recovering_bits = vmalloc(bitset_size);
+	if (!lc->recovering_bits) {
 		DMWARN("couldn't allocate sync bitset");
-		vfree(clog->sync_bits);
-		vfree(clog->clean_bits);
-		kfree(clog);
+		vfree(lc->sync_bits);
+		vfree(lc->clean_bits);
+		kfree(lc);
 		return -ENOMEM;
 	}
-	memset(clog->recovering_bits, 0, bitset_size);
-	clog->sync_search = 0;
-	log->context = clog;
+	memset(lc->recovering_bits, 0, bitset_size);
+	lc->sync_search = 0;
+	log->context = lc;
 	return 0;
 }
 
 static void core_dtr(struct dirty_log *log)
 {
-	struct core_log *clog = (struct core_log *) log->context;
-	vfree(clog->clean_bits);
-	vfree(clog->sync_bits);
-	vfree(clog->recovering_bits);
-	kfree(clog);
+	struct log_c *lc = (struct log_c *) log->context;
+	vfree(lc->clean_bits);
+	vfree(lc->sync_bits);
+	vfree(lc->recovering_bits);
+	kfree(lc);
+}
+
+static int disk_ctr(struct dirty_log *log, struct dm_target *ti,
+		    unsigned int argc, char **argv)
+{
+	int r;
+	size_t size;
+	struct log_c *lc;
+	struct dm_dev *dev;
+
+	r = dm_get_device(ti, argv[0], 0, 0 /* FIXME */,
+			  FMODE_READ | FMODE_WRITE, &dev);
+	if (r)
+		return r;
+
+	r = core_ctr(log, ti, argc - 1, argv + 1);
+	if (r) {
+		dm_put_device(ti, dev);
+		return r;
+	}
+
+	lc = (struct log_c *) log->context;
+	lc->log_dev = dev;
+
+	/* setup the disk header fields */
+	lc->header_location.bdev = lc->log_dev->bdev;
+	lc->header_location.sector = 0;
+	lc->header_location.count = 1;
+	lc->disk_header = vmalloc(sizeof(struct log_header));
+	if (!lc->disk_header)
+		goto bad;
+
+	lc->header_pages = vmalloc_to_page(lc->disk_header);
+
+	/* setup the disk bitset fields */
+	lc->bits_location.bdev = lc->log_dev->bdev;
+	lc->bits_location.sector = LOG_OFFSET;
+
+	size = dm_round_up(lc->bitset_uint32_count * sizeof(uint32_t),
+			   1 << SECTOR_SHIFT);
+	lc->bits_location.count = size >> SECTOR_SHIFT;
+	lc->disk_bits = vmalloc(size);
+	if (!lc->disk_bits) {
+		vfree(lc->disk_header);
+		goto bad;
+	}
+	lc->bits_pages = vmalloc_to_page(lc->disk_bits);
+	return 0;
+
+ bad:
+	dm_put_device(ti, lc->log_dev);
+	core_dtr(log);
+	return -ENOMEM;
+}
+
+static void disk_dtr(struct dirty_log *log)
+{
+	struct log_c *lc = (struct log_c *) log->context;
+	core_dtr(log);
+	dm_put_device(lc->ti, lc->log_dev);
+	vfree(lc->disk_header);
+	vfree(lc->disk_bits);
+}
+
+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)
+		return r;
+
+	/* read the bits */
+	r = read_bits(lc);
+	if (r)
+		return r;
+
+	/* zero any new bits if the mirror has grown */
+	for (i = lc->header.nr_regions; i < lc->region_count; i++)
+		/* FIXME: amazingly inefficient */
+		log_clear_bit(lc, lc->clean_bits, i);
+
+	/* copy clean across to sync */
+	memcpy(lc->sync_bits, lc->clean_bits, size);
+
+	/* write the bits */
+	r = write_bits(lc);
+	if (r)
+		return r;
+
+	/* set the correct number of regions in the header */
+	lc->header.nr_regions = lc->region_count;
+
+	/* write the new header */
+	return write_header(lc);
 }
 
 static sector_t core_get_region_size(struct dirty_log *log)
 {
-	struct core_log *clog = (struct core_log *) log->context;
-	return clog->region_size;
+	struct log_c *lc = (struct log_c *) log->context;
+	return lc->region_size;
 }
 
 static int core_is_clean(struct dirty_log *log, region_t region)
 {
-	struct core_log *clog = (struct core_log *) log->context;
-	return test_bit(region, clog->clean_bits);
+	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 core_log *clog = (struct core_log *) log->context;
-
-	return test_bit(region, clog->sync_bits) ? 1 : 0;
+	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)
@@ -224,53 +481,68 @@
 	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_bits(lc);
+	if (!r)
+		lc->touched = 0;
+
+	return r;
+}
+
 static void core_mark_region(struct dirty_log *log, region_t region)
 {
-	struct core_log *clog = (struct core_log *) log->context;
-	clear_bit(region, clog->clean_bits);
+	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 core_log *clog = (struct core_log *) log->context;
-	set_bit(region, clog->clean_bits);
+	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 core_log *clog = (struct core_log *) log->context;
+	struct log_c *lc = (struct log_c *) log->context;
 
-	if (clog->sync_search >= clog->region_count)
+	if (lc->sync_search >= lc->region_count)
 		return 0;
 
 	do {
-		*region = find_next_zero_bit(clog->sync_bits,
-					     clog->region_count,
-					     clog->sync_search);
-		clog->sync_search = *region + 1;
+		*region = find_next_zero_bit((unsigned long *) lc->sync_bits,
+					     lc->region_count,
+					     lc->sync_search);
+		lc->sync_search = *region + 1;
 
-		if (*region == clog->region_count)
+		if (*region == lc->region_count)
 			return 0;
 
-	} while (test_bit(*region, clog->recovering_bits));
+	} while (log_test_bit(lc->recovering_bits, *region));
 
-	set_bit(*region, clog->recovering_bits);
+	log_set_bit(lc, lc->recovering_bits, *region);
 	return 1;
 }
 
 static void core_complete_resync_work(struct dirty_log *log, region_t region,
 				      int success)
 {
-	struct core_log *clog = (struct core_log *) log->context;
+	struct log_c *lc = (struct log_c *) log->context;
 
-	clear_bit(region, clog->recovering_bits);
+	log_clear_bit(lc, lc->recovering_bits, region);
 	if (success)
-		set_bit(region, clog->sync_bits);
+		log_set_bit(lc, lc->sync_bits, region);
 }
 
 static struct dirty_log_type _core_type = {
 	.name = "core",
-
 	.ctr = core_ctr,
 	.dtr = core_dtr,
 	.get_region_size = core_get_region_size,
@@ -283,6 +555,21 @@
 	.complete_resync_work = core_complete_resync_work
 };
 
+static struct dirty_log_type _disk_type = {
+	.name = "disk",
+	.ctr = disk_ctr,
+	.dtr = disk_dtr,
+	.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,
+	.complete_resync_work = core_complete_resync_work
+};
+
 __init int dm_dirty_log_init(void)
 {
 	int r;
@@ -291,11 +578,18 @@
 	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);
 }
 
--- diff/drivers/md/dm-log.h	2003-11-26 10:18:32.000000000 +0000
+++ source/drivers/md/dm-log.h	2003-12-10 13:02:37.000000000 +0000
@@ -24,11 +24,18 @@
 	struct module *module;
 	unsigned int use_count;
 
-	int (*ctr)(struct dirty_log *log, sector_t dev_size,
+	int (*ctr)(struct dirty_log *log, struct dm_target *ti,
 		   unsigned int argc, char **argv);
 	void (*dtr)(struct dirty_log *log);
 
 	/*
+	 * There are times when we don't want the log to touch
+	 * the disk.
+	 */
+	int (*suspend)(struct dirty_log *log);
+	int (*resume)(struct dirty_log *log);
+
+	/*
 	 * Retrieves the smallest size of region that the log can
 	 * deal with.
 	 */
@@ -99,7 +106,7 @@
  * Make sure you use these two functions, rather than calling
  * type->constructor/destructor() directly.
  */
-struct dirty_log *dm_create_dirty_log(const char *type_name, sector_t dev_size,
+struct dirty_log *dm_create_dirty_log(const char *type_name, struct dm_target *ti,
 				      unsigned int argc, char **argv);
 void dm_destroy_dirty_log(struct dirty_log *log);
 
--- diff/drivers/md/dm-raid1.c	2003-12-04 11:18:37.000000000 +0000
+++ source/drivers/md/dm-raid1.c	2003-12-10 13:37:42.000000000 +0000
@@ -637,6 +637,8 @@
 	struct region *reg = (struct region *) context;
 	struct mirror_set *ms = reg->rh->ms;
 
+	/* FIXME: we need to flush the log */
+
 	/* FIXME: better error handling */
 	rh_recovery_end(reg, read_err || write_err);
 	if (++ms->sync_count == ms->nr_regions)
@@ -1025,7 +1027,7 @@
 		return NULL;
 	}
 
-	dl = dm_create_dirty_log(argv[0], ti->len, param_count, argv + 2);
+	dl = dm_create_dirty_log(argv[0], ti, param_count, argv + 2);
 	if (!dl) {
 		ti->error = "dm-mirror: Error creating mirror dirty log";
 		return NULL;
@@ -1198,12 +1200,20 @@
 static void mirror_suspend(struct dm_target *ti)
 {
 	struct mirror_set *ms = (struct mirror_set *) ti->private;
+	struct dirty_log *log = ms->rh.log;
 	rh_stop_recovery(&ms->rh);
+	if (log->type->suspend && log->type->suspend(log))
+		/* FIXME: need better error handling */
+		DMWARN("log suspend failed");
 }
 
 static void mirror_resume(struct dm_target *ti)
 {
 	struct mirror_set *ms = (struct mirror_set *) ti->private;
+	struct dirty_log *log = ms->rh.log;
+	if (log->type->resume && log->type->resume(log))
+		/* FIXME: need better error handling */
+		DMWARN("log resume failed");
 	rh_start_recovery(&ms->rh);
 }