BBR Target.

--- diff/drivers/md/Kconfig	2005-02-28 08:47:41.273684104 -0600
+++ source/drivers/md/Kconfig	2005-02-28 09:30:07.009673408 -0600
@@ -239,6 +239,17 @@
 	---help---
 	  Multipath support for EMC CX/AX series hardware.
 
+config BLK_DEV_DM_BBR
+	tristate "Bad Block Relocation Device Target (EXPERIMENTAL)"
+	depends on BLK_DEV_DM && EXPERIMENTAL
+	---help---
+	  Support for devices with software-based bad-block-relocation.
+
+	  To compile this as a module, choose M here: the module will be
+	  called dm-bbr.
+
+	  If unsure, say N.
+
 config DM_FLAKEY
        tristate "Flakey target (EXPERIMENTAL)"
        depends on BLK_DEV_DM && EXPERIMENTAL
--- diff/drivers/md/Makefile	2005-02-28 08:47:41.274683952 -0600
+++ source/drivers/md/Makefile	2005-02-28 09:30:07.010673256 -0600
@@ -37,6 +37,7 @@
 obj-$(CONFIG_DM_MIRROR)		+= dm-mirror.o
 obj-$(CONFIG_DM_FLAKEY)		+= dm-flakey.o
 obj-$(CONFIG_DM_ZERO)		+= dm-zero.o
+obj-$(CONFIG_BLK_DEV_DM_BBR)	+= dm-bbr.o
 
 quiet_cmd_unroll = UNROLL  $@
       cmd_unroll = $(PERL) $(srctree)/$(src)/unroll.pl $(UNROLL) \
--- diff/drivers/md/dm-bbr.c	1969-12-31 18:00:00.000000000 -0600
+++ source/drivers/md/dm-bbr.c	2005-02-28 09:30:07.012672952 -0600
@@ -0,0 +1,1003 @@
+/*
+ *   (C) Copyright IBM Corp. 2002, 2004
+ *
+ *   This program is free software;  you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation; either version 2 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY;  without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See
+ *   the GNU General Public License for more details.
+ *
+ *   You should have received a copy of the GNU General Public License
+ *   along with this program;  if not, write to the Free Software
+ *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ *
+ * linux/drivers/md/dm-bbr.c
+ *
+ * Bad-block-relocation (BBR) target for device-mapper.
+ *
+ * The BBR target is designed to remap I/O write failures to another safe
+ * location on disk. Note that most disk drives have BBR built into them,
+ * this means that our software BBR will be only activated when all hardware
+ * BBR replacement sectors have been used.
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/bio.h>
+#include <linux/spinlock.h>
+#include <linux/slab.h>
+#include <linux/mempool.h>
+#include <linux/workqueue.h>
+#include <linux/vmalloc.h>
+
+#include "dm.h"
+#include "dm-bio-list.h"
+#include "dm-bio-record.h"
+#include "dm-bbr.h"
+#include "dm-io.h"
+
+#define SECTOR_SIZE (1 << SECTOR_SHIFT)
+
+static struct workqueue_struct *dm_bbr_wq = NULL;
+static void bbr_remap_handler(void *data);
+static kmem_cache_t *bbr_remap_cache;
+static kmem_cache_t *bbr_io_cache;
+static mempool_t *bbr_io_pool;
+
+/**
+ * bbr_binary_tree_destroy
+ *
+ * Destroy the binary tree.
+ **/
+static void bbr_binary_tree_destroy(struct bbr_runtime_remap *root)
+{
+	struct bbr_runtime_remap **link = NULL;
+	struct bbr_runtime_remap *node = root;
+
+	while (node) {
+		if (node->left) {
+			link = &(node->left);
+			node = node->left;
+			continue;
+		}
+		if (node->right) {
+			link = &(node->right);
+			node = node->right;
+			continue;
+		}
+
+		kmem_cache_free(bbr_remap_cache, node);
+		if (node == root) {
+			/* If root is deleted, we're done. */
+			break;
+		}
+
+		/* Back to root. */
+		node = root;
+		*link = NULL;
+	}
+}
+
+static void bbr_free_remap(struct bbr_private *bbr_id)
+{
+	spin_lock_irq(&bbr_id->remap_root_lock);
+	bbr_binary_tree_destroy(bbr_id->remap_root);
+	bbr_id->remap_root = NULL;
+	spin_unlock_irq(&bbr_id->remap_root_lock);
+}
+
+static struct bbr_private *bbr_alloc_private(void)
+{
+	struct bbr_private *bbr_id;
+
+	bbr_id = kmalloc(sizeof(*bbr_id), GFP_KERNEL);
+	if (bbr_id) {
+		memset(bbr_id, 0, sizeof(*bbr_id));
+		INIT_WORK(&bbr_id->remap_work, bbr_remap_handler, bbr_id);
+		bbr_id->remap_root_lock = SPIN_LOCK_UNLOCKED;
+		bbr_id->remap_ios_lock = SPIN_LOCK_UNLOCKED;
+		bbr_id->in_use_replacement_blks = (atomic_t)ATOMIC_INIT(0);
+	}
+
+	return bbr_id;
+}
+
+static void bbr_free_private(struct bbr_private *bbr_id)
+{
+	if (bbr_id->bbr_table) {
+		vfree(bbr_id->bbr_table);
+	}
+	bbr_free_remap(bbr_id);
+	kfree(bbr_id);
+}
+
+static u32 crc_table[256];
+static u32 crc_table_built = 0;
+
+static void build_crc_table(void)
+{
+	u32 i, j, crc;
+
+	for (i = 0; i <= 255; i++) {
+		crc = i;
+		for (j = 8; j > 0; j--) {
+			if (crc & 1)
+				crc = (crc >> 1) ^ CRC_POLYNOMIAL;
+			else
+				crc >>= 1;
+		}
+		crc_table[i] = crc;
+	}
+	crc_table_built = 1;
+}
+
+static u32 calculate_crc(u32 crc, void *buffer, u32 buffersize)
+{
+	unsigned char *current_byte;
+	u32 temp1, temp2, i;
+
+	current_byte = (unsigned char *) buffer;
+	/* Make sure the crc table is available */
+	if (!crc_table_built)
+		build_crc_table();
+	/* Process each byte in the buffer. */
+	for (i = 0; i < buffersize; i++) {
+		temp1 = (crc >> 8) & 0x00FFFFFF;
+		temp2 = crc_table[(crc ^ (u32) * current_byte) &
+				  (u32) 0xff];
+		current_byte++;
+		crc = temp1 ^ temp2;
+	}
+	return crc;
+}
+
+/**
+ * le_bbr_table_sector_to_cpu
+ *
+ * Convert bbr meta data from on-disk (LE) format
+ * to the native cpu endian format.
+ **/
+static void le_bbr_table_sector_to_cpu(struct bbr_table *p)
+{
+	int i;
+	p->signature		= le32_to_cpup(&p->signature);
+	p->crc			= le32_to_cpup(&p->crc);
+	p->sequence_number	= le32_to_cpup(&p->sequence_number);
+	p->in_use_cnt		= le32_to_cpup(&p->in_use_cnt);
+	for (i = 0; i < BBR_ENTRIES_PER_SECT; i++) {
+		p->entries[i].bad_sect =
+			le64_to_cpup(&p->entries[i].bad_sect);
+		p->entries[i].replacement_sect =
+			le64_to_cpup(&p->entries[i].replacement_sect);
+	}
+}
+
+/**
+ * cpu_bbr_table_sector_to_le
+ *
+ * Convert bbr meta data from cpu endian format to on-disk (LE) format
+ **/
+static void cpu_bbr_table_sector_to_le(struct bbr_table *p,
+				       struct bbr_table *le)
+{
+	int i;
+	le->signature		= cpu_to_le32p(&p->signature);
+	le->crc			= cpu_to_le32p(&p->crc);
+	le->sequence_number	= cpu_to_le32p(&p->sequence_number);
+	le->in_use_cnt		= cpu_to_le32p(&p->in_use_cnt);
+	for (i = 0; i < BBR_ENTRIES_PER_SECT; i++) {
+		le->entries[i].bad_sect =
+			cpu_to_le64p(&p->entries[i].bad_sect);
+		le->entries[i].replacement_sect =
+			cpu_to_le64p(&p->entries[i].replacement_sect);
+	}
+}
+
+/**
+ * validate_bbr_table_sector
+ *
+ * Check the specified BBR table sector for a valid signature and CRC. If it's
+ * valid, endian-convert the table sector.
+ **/
+static int validate_bbr_table_sector(struct bbr_table *p)
+{
+	int rc = 0;
+	int org_crc, final_crc;
+
+	if (le32_to_cpup(&p->signature) != BBR_TABLE_SIGNATURE) {
+		DMERR("dm-bbr: BBR table signature doesn't match!");
+		DMERR("dm-bbr: Found 0x%x. Expecting 0x%x",
+		      le32_to_cpup(&p->signature), BBR_TABLE_SIGNATURE);
+		rc = -EINVAL;
+		goto out;
+	}
+
+	if (!p->crc) {
+		DMERR("dm-bbr: BBR table sector has no CRC!");
+		rc = -EINVAL;
+		goto out;
+	}
+
+	org_crc = le32_to_cpup(&p->crc);
+	p->crc = 0;
+	final_crc = calculate_crc(INITIAL_CRC, (void *)p, sizeof(*p));
+	if (final_crc != org_crc) {
+		DMERR("dm-bbr: CRC failed!");
+		DMERR("dm-bbr: Found 0x%x. Expecting 0x%x",
+		      org_crc, final_crc);
+		rc = -EINVAL;
+		goto out;
+	}
+
+	p->crc = cpu_to_le32p(&org_crc);
+	le_bbr_table_sector_to_cpu(p);
+
+out:
+	return rc;
+}
+
+/**
+ * bbr_binary_tree_insert
+ *
+ * Insert a node into the binary tree.
+ **/
+static void bbr_binary_tree_insert(struct bbr_runtime_remap **root,
+				   struct bbr_runtime_remap *newnode)
+{
+	struct bbr_runtime_remap **node = root;
+	while (node && *node) {
+		if (newnode->remap.bad_sect > (*node)->remap.bad_sect) {
+			node = &((*node)->right);
+		} else {
+			node = &((*node)->left);
+		}
+	}
+
+	newnode->left = newnode->right = NULL;
+	*node = newnode;
+}
+
+/**
+ * bbr_binary_search
+ *
+ * Search for a node that contains bad_sect == lsn.
+ **/
+static struct bbr_runtime_remap *bbr_binary_search(
+	struct bbr_runtime_remap *root,
+	u64 lsn)
+{
+	struct bbr_runtime_remap *node = root;
+	while (node) {
+		if (node->remap.bad_sect == lsn) {
+			break;
+		}
+		if (lsn > node->remap.bad_sect) {
+			node = node->right;
+		} else {
+			node = node->left;
+		}
+	}
+	return node;
+}
+
+/**
+ * bbr_insert_remap_entry
+ *
+ * Create a new remap entry and add it to the binary tree for this node.
+ **/
+static int bbr_insert_remap_entry(struct bbr_private *bbr_id,
+				  struct bbr_table_entry *new_bbr_entry)
+{
+	struct bbr_runtime_remap *newnode;
+
+	newnode = kmem_cache_alloc(bbr_remap_cache, GFP_NOIO);
+	if (!newnode) {
+		DMERR("dm-bbr: Could not allocate from remap cache!");
+		return -ENOMEM;
+	}
+	newnode->remap.bad_sect  = new_bbr_entry->bad_sect;
+	newnode->remap.replacement_sect = new_bbr_entry->replacement_sect;
+	spin_lock_irq(&bbr_id->remap_root_lock);
+	bbr_binary_tree_insert(&bbr_id->remap_root, newnode);
+	spin_unlock_irq(&bbr_id->remap_root_lock);
+	return 0;
+}
+
+/**
+ * bbr_table_to_remap_list
+ *
+ * The on-disk bbr table is sorted by the replacement sector LBA. In order to
+ * improve run time performance, the in memory remap list must be sorted by
+ * the bad sector LBA. This function is called at discovery time to initialize
+ * the remap list. This function assumes that at least one copy of meta data
+ * is valid.
+ **/
+static u32 bbr_table_to_remap_list(struct bbr_private *bbr_id)
+{
+	u32 in_use_blks = 0;
+	int i, j;
+	struct bbr_table *p;
+
+	for (i = 0, p = bbr_id->bbr_table;
+	     i < bbr_id->nr_sects_bbr_table;
+	     i++, p++) {
+		if (!p->in_use_cnt) {
+			break;
+		}
+		in_use_blks += p->in_use_cnt;
+		for (j = 0; j < p->in_use_cnt; j++) {
+			bbr_insert_remap_entry(bbr_id, &p->entries[j]);
+		}
+	}
+	if (in_use_blks) {
+		char b[32];
+		DMWARN("dm-bbr: There are %u BBR entries for device %s",
+		       in_use_blks, format_dev_t(b, bbr_id->dev->bdev->bd_dev));
+	}
+
+	return in_use_blks;
+}
+
+/**
+ * bbr_search_remap_entry
+ *
+ * Search remap entry for the specified sector. If found, return a pointer to
+ * the table entry. Otherwise, return NULL.
+ **/
+static struct bbr_table_entry *bbr_search_remap_entry(
+	struct bbr_private *bbr_id,
+	u64 lsn)
+{
+	struct bbr_runtime_remap *p;
+
+	spin_lock_irq(&bbr_id->remap_root_lock);
+	p = bbr_binary_search(bbr_id->remap_root, lsn);
+	spin_unlock_irq(&bbr_id->remap_root_lock);
+	if (p) {
+		return (&p->remap);
+	} else {
+		return NULL;
+	}
+}
+
+/**
+ * bbr_remap
+ *
+ * If *lsn is in the remap table, return TRUE and modify *lsn,
+ * else, return FALSE.
+ **/
+static inline int bbr_remap(struct bbr_private *bbr_id,
+			    u64 *lsn)
+{
+	struct bbr_table_entry *e;
+
+	if (atomic_read(&bbr_id->in_use_replacement_blks)) {
+		e = bbr_search_remap_entry(bbr_id, *lsn);
+		if (e) {
+			*lsn = e->replacement_sect;
+			return 1;
+		}
+	}
+	return 0;
+}
+
+/**
+ * bbr_remap_probe
+ *
+ * If any of the sectors in the range [lsn, lsn+nr_sects] are in the remap
+ * table return TRUE, Else, return FALSE.
+ **/
+static inline int bbr_remap_probe(struct bbr_private *bbr_id,
+				  u64 lsn, u64 nr_sects)
+{
+	u64 tmp, cnt;
+
+	if (atomic_read(&bbr_id->in_use_replacement_blks)) {
+		for (cnt = 0, tmp = lsn;
+		     cnt < nr_sects;
+		     cnt += bbr_id->blksize_in_sects, tmp = lsn + cnt) {
+			if (bbr_remap(bbr_id,&tmp)) {
+				return 1;
+			}
+		}
+	}
+	return 0;
+}
+
+/**
+ * bbr_setup
+ *
+ * Read the remap tables from disk and set up the initial remap tree.
+ **/
+static int bbr_setup(struct bbr_private *bbr_id)
+{
+	struct bbr_table *table = bbr_id->bbr_table;
+	struct io_region job;
+	unsigned long error;
+	int i, rc = 0;
+
+	job.bdev = bbr_id->dev->bdev;
+	job.count = 1;
+
+	/* Read and verify each BBR table sector individually. */
+	for (i = 0; i < bbr_id->nr_sects_bbr_table; i++, table++) {
+		job.sector = bbr_id->lba_table1 + i;
+		rc = dm_io_sync_vm(1, &job, READ, table, &error);
+		if (rc && bbr_id->lba_table2) {
+			job.sector = bbr_id->lba_table2 + i;
+			rc = dm_io_sync_vm(1, &job, READ, table, &error);
+		}
+		if (rc) {
+			goto out;
+		}
+
+		rc = validate_bbr_table_sector(table);
+		if (rc) {
+			goto out;
+		}
+	}
+	atomic_set(&bbr_id->in_use_replacement_blks,
+		   bbr_table_to_remap_list(bbr_id));
+
+out:
+	if (rc) {
+		DMERR("dm-bbr: error during device setup: %d", rc);
+	}
+	return rc;
+}
+
+/**
+ * bbr_io_remap_error
+ * @bbr_id:		Private data for the BBR node.
+ * @rw:			READ or WRITE.
+ * @starting_lsn:	Starting sector of request to remap.
+ * @count:		Number of sectors in the request.
+ * @page:		Page containing the data for the request.
+ * @offset:		Byte-offset of the data within the page.
+ *
+ * For the requested range, try to write each sector individually. For each
+ * sector that fails, find the next available remap location and write the
+ * data to that new location. Then update the table and write both copies
+ * of the table to disk. Finally, update the in-memory mapping and do any
+ * other necessary bookkeeping.
+ **/
+static int bbr_io_remap_error(struct bbr_private *bbr_id,
+			      int rw,
+			      u64 starting_lsn,
+			      u64 count,
+			      struct page *page,
+			      unsigned int offset)
+{
+	struct bbr_table *bbr_table;
+	struct io_region job;
+	struct page_list pl;
+	unsigned long table_sector_index;
+	unsigned long table_sector_offset;
+	unsigned long index;
+	unsigned long error;
+	u64 lsn, new_lsn;
+	char b[32];
+	int rc;
+
+	job.bdev = bbr_id->dev->bdev;
+	job.count = 1;
+	pl.page = page;
+	pl.next = NULL;
+
+	/* For each sector in the request. */
+	for (lsn = 0; lsn < count; lsn++, offset += SECTOR_SIZE) {
+		job.sector = starting_lsn + lsn;
+		rc = dm_io_sync(1, &job, rw, &pl, offset, &error);
+		while (rc) {
+			/* Find the next available relocation sector. */
+			new_lsn = atomic_read(&bbr_id->in_use_replacement_blks);
+			if (new_lsn >= bbr_id->nr_replacement_blks) {
+				/* No more replacement sectors available. */
+				return -EIO;
+			}
+			new_lsn += bbr_id->start_replacement_sect;
+
+			/* Write the data to its new location. */
+			DMWARN("dm-bbr: device %s: Trying to remap bad sector "PFU64" to sector "PFU64,
+			       format_dev_t(b, bbr_id->dev->bdev->bd_dev),
+			       starting_lsn + lsn, new_lsn);
+			job.sector = new_lsn;
+			rc = dm_io_sync(1, &job, rw, &pl, offset, &error);
+			if (rc) {
+				/* This replacement sector is bad.
+				 * Try the next one.
+				 */
+				DMERR("dm-bbr: device %s: replacement sector "PFU64" is bad. Skipping.",
+				      format_dev_t(b, bbr_id->dev->bdev->bd_dev), new_lsn);
+				atomic_inc(&bbr_id->in_use_replacement_blks);
+				continue;
+			}
+
+			/* Add this new entry to the on-disk table. */
+			table_sector_index = new_lsn -
+					     bbr_id->start_replacement_sect;
+			table_sector_offset = table_sector_index /
+					      BBR_ENTRIES_PER_SECT;
+			index = table_sector_index % BBR_ENTRIES_PER_SECT;
+
+			bbr_table = &bbr_id->bbr_table[table_sector_offset];
+			bbr_table->entries[index].bad_sect = starting_lsn + lsn;
+			bbr_table->entries[index].replacement_sect = new_lsn;
+			bbr_table->in_use_cnt++;
+			bbr_table->sequence_number++;
+			bbr_table->crc = 0;
+			bbr_table->crc = calculate_crc(INITIAL_CRC,
+						       bbr_table,
+						       sizeof(struct bbr_table));
+
+			/* Write the table to disk. */
+			cpu_bbr_table_sector_to_le(bbr_table, bbr_table);
+			if (bbr_id->lba_table1) {
+				job.sector = bbr_id->lba_table1 + table_sector_offset;
+				rc = dm_io_sync_vm(1, &job, WRITE, bbr_table, &error);
+			}
+			if (bbr_id->lba_table2) {
+				job.sector = bbr_id->lba_table2 + table_sector_offset;
+				rc |= dm_io_sync_vm(1, &job, WRITE, bbr_table, &error);
+			}
+			le_bbr_table_sector_to_cpu(bbr_table);
+
+			if (rc) {
+				/* Error writing one of the tables to disk. */
+				DMERR("dm-bbr: device %s: error updating BBR tables on disk.",
+				      format_dev_t(b, bbr_id->dev->bdev->bd_dev));
+				return rc;
+			}
+
+			/* Insert a new entry in the remapping binary-tree. */
+			rc = bbr_insert_remap_entry(bbr_id,
+						    &bbr_table->entries[index]);
+			if (rc) {
+				DMERR("dm-bbr: device %s: error adding new entry to remap tree.",
+				      format_dev_t(b, bbr_id->dev->bdev->bd_dev));
+				return rc;
+			}
+
+			atomic_inc(&bbr_id->in_use_replacement_blks);
+		}
+	}
+
+	return 0;
+}
+
+/**
+ * bbr_io_process_request
+ *
+ * For each sector in this request, check if the sector has already
+ * been remapped. If so, process all previous sectors in the request,
+ * followed by the remapped sector. Then reset the starting lsn and
+ * count, and keep going with the rest of the request as if it were
+ * a whole new request. If any of the sync_io's return an error,
+ * call the remapper to relocate the bad sector(s).
+ *
+ * 2.5 Note: When switching over to bio's for the I/O path, we have made
+ * the assumption that the I/O request described by the bio is one
+ * virtually contiguous piece of memory (even though the bio vector
+ * describes it using a series of physical page addresses).
+ **/
+static int bbr_io_process_request(struct bbr_private *bbr_id,
+				  struct bio *bio)
+{
+	struct io_region job;
+	u64 starting_lsn = bio->bi_sector;
+	u64 count, lsn, remapped_lsn;
+	struct page_list pl;
+	unsigned int offset;
+	unsigned long error;
+	int i, rw = bio_data_dir(bio);
+	int rc = 0;
+
+	job.bdev = bbr_id->dev->bdev;
+	pl.next = NULL;
+
+	/* Each bio can contain multiple vectors, each with a different page.
+	 * Treat each vector as a separate request.
+	 */
+	/* KMC: Is this the right way to walk the bvec list? */
+	for (i = 0;
+	     i < bio->bi_vcnt;
+	     i++, bio->bi_idx++, starting_lsn += count) {
+
+		/* Bvec info: number of sectors, page,
+		 * and byte-offset within page.
+		 */
+		count = bio_iovec(bio)->bv_len >> SECTOR_SHIFT;
+		pl.page = bio_iovec(bio)->bv_page;
+		offset = bio_iovec(bio)->bv_offset;
+
+		/* For each sector in this bvec, check if the sector has
+		 * already been remapped. If so, process all previous sectors
+		 * in this request, followed by the remapped sector. Then reset
+		 * the starting lsn and count and keep going with the rest of
+		 * the request as if it were a whole new request.
+		 */
+		for (lsn = 0; lsn < count; lsn++) {
+			remapped_lsn = starting_lsn + lsn;
+			rc = bbr_remap(bbr_id, &remapped_lsn);
+			if (!rc) {
+				/* This sector is fine. */
+				continue;
+			}
+
+			/* Process all sectors in the request up to this one. */
+			if (lsn > 0) {
+				job.sector = starting_lsn;
+				job.count = lsn;
+				rc = dm_io_sync(1, &job, rw, &pl,
+						offset, &error);
+				if (rc) {
+					/* If this I/O failed, then one of the
+					 * sectors in this request needs to be
+					 * relocated.
+					 */
+					rc = bbr_io_remap_error(bbr_id, rw,
+								starting_lsn,
+								lsn, pl.page,
+								offset);
+					if (rc) {
+						/* KMC: Return? Or continue to next bvec? */
+						return rc;
+					}
+				}
+				offset += (lsn << SECTOR_SHIFT);
+			}
+	
+			/* Process the remapped sector. */
+			job.sector = remapped_lsn;
+			job.count = 1;
+			rc = dm_io_sync(1, &job, rw, &pl, offset, &error);
+			if (rc) {
+				/* BUGBUG - Need more processing if this caused
+				 * an error. If this I/O failed, then the
+				 * existing remap is now bad, and we need to
+				 * find a new remap. Can't use
+				 * bbr_io_remap_error(), because the existing
+				 * map entry needs to be changed, not added
+				 * again, and the original table entry also
+				 * needs to be changed.
+				 */
+				return rc;
+			}
+
+			starting_lsn	+= (lsn + 1);
+			count		-= (lsn + 1);
+			lsn		= -1;
+			offset		+= SECTOR_SIZE;
+		}
+
+		/* Check for any remaining sectors after the last split. This
+		 * could potentially be the whole request, but that should be a
+		 * rare case because requests should only be processed by the
+		 * thread if we know an error occurred or they contained one or
+		 * more remapped sectors.
+		 */
+		if (count) {
+			job.sector = starting_lsn;
+			job.count = count;
+			rc = dm_io_sync(1, &job, rw, &pl, offset, &error);
+			if (rc) {
+				/* If this I/O failed, then one of the sectors
+				 * in this request needs to be relocated.
+				 */
+				rc = bbr_io_remap_error(bbr_id, rw, starting_lsn,
+							count, pl.page, offset);
+				if (rc) {
+					/* KMC: Return? Or continue to next bvec? */
+					return rc;
+				}
+			}
+		}
+	}
+
+	return 0;
+}
+
+static void bbr_io_process_requests(struct bbr_private *bbr_id,
+				    struct bio *bio)
+{
+	struct bio *next;
+	int rc;
+
+	while (bio) {
+		next = bio->bi_next;
+		bio->bi_next = NULL;
+
+		rc = bbr_io_process_request(bbr_id, bio);
+
+		bio_endio(bio, bio->bi_size, rc);
+
+		bio = next;
+	}
+}
+
+/**
+ * bbr_remap_handler
+ *
+ * This is the handler for the bbr work-queue.
+ *
+ * I/O requests should only be sent to this handler if we know that:
+ * a) the request contains at least one remapped sector.
+ *   or
+ * b) the request caused an error on the normal I/O path.
+ *
+ * This function uses synchronous I/O, so sending a request to this
+ * thread that doesn't need special processing will cause severe
+ * performance degredation.
+ **/
+static void bbr_remap_handler(void *data)
+{
+	struct bbr_private *bbr_id = data;
+	struct bio *bio;
+	unsigned long flags;
+
+	spin_lock_irqsave(&bbr_id->remap_ios_lock, flags);
+	bio = bio_list_get(&bbr_id->remap_ios);
+	spin_unlock_irqrestore(&bbr_id->remap_ios_lock, flags);
+
+	bbr_io_process_requests(bbr_id, bio);
+}
+
+/**
+ * bbr_endio
+ *
+ * This is the callback for normal write requests. Check for an error
+ * during the I/O, and send to the thread for processing if necessary.
+ **/
+static int bbr_endio(struct dm_target *ti, struct bio *bio,
+		     int error, union map_info *map_context)
+{
+	struct bbr_private *bbr_id = ti->private;
+	struct dm_bio_details *bbr_io = map_context->ptr;
+
+	if (error && bbr_io) {
+		unsigned long flags;
+		char b[32];
+
+		dm_bio_restore(bbr_io, bio);
+		map_context->ptr = NULL;
+
+		DMERR("dm-bbr: device %s: I/O failure on sector %lu. "
+		      "Scheduling for retry.",
+		      format_dev_t(b, bbr_id->dev->bdev->bd_dev),
+		      (unsigned long)bio->bi_sector);
+
+		spin_lock_irqsave(&bbr_id->remap_ios_lock, flags);
+		bio_list_add(&bbr_id->remap_ios, bio);
+		spin_unlock_irqrestore(&bbr_id->remap_ios_lock, flags);
+
+		queue_work(dm_bbr_wq, &bbr_id->remap_work);
+
+		error = 1;
+	}
+
+	if (bbr_io)
+		mempool_free(bbr_io, bbr_io_pool);
+
+	return error;
+}
+
+/**
+ * Construct a bbr mapping
+ **/
+static int bbr_ctr(struct dm_target *ti, unsigned int argc, char **argv)
+{
+	struct bbr_private *bbr_id;
+	unsigned long block_size;
+	char *end;
+	int rc = -EINVAL;
+
+	if (argc != 8) {
+		ti->error = "dm-bbr requires exactly 8 arguments: "
+			    "device offset table1_lsn table2_lsn table_size start_replacement nr_replacement_blks block_size";
+		goto out1;
+	}
+
+	bbr_id = bbr_alloc_private();
+	if (!bbr_id) {
+		ti->error = "dm-bbr: Error allocating bbr private data.";
+		goto out1;
+	}
+
+	bbr_id->offset = simple_strtoull(argv[1], &end, 10);
+	bbr_id->lba_table1 = simple_strtoull(argv[2], &end, 10);
+	bbr_id->lba_table2 = simple_strtoull(argv[3], &end, 10);
+	bbr_id->nr_sects_bbr_table = simple_strtoull(argv[4], &end, 10);
+	bbr_id->start_replacement_sect = simple_strtoull(argv[5], &end, 10);
+	bbr_id->nr_replacement_blks = simple_strtoull(argv[6], &end, 10);
+	block_size = simple_strtoul(argv[7], &end, 10);
+	bbr_id->blksize_in_sects = (block_size >> SECTOR_SHIFT);
+
+	bbr_id->bbr_table = vmalloc(bbr_id->nr_sects_bbr_table << SECTOR_SHIFT);
+	if (!bbr_id->bbr_table) {
+		ti->error = "dm-bbr: Error allocating bbr table.";
+		goto out2;
+	}
+
+	if (dm_get_device(ti, argv[0], 0, ti->len,
+			  dm_table_get_mode(ti->table), &bbr_id->dev)) {
+		ti->error = "dm-bbr: Device lookup failed";
+		goto out2;
+	}
+
+	rc = bbr_setup(bbr_id);
+	if (rc) {
+		ti->error = "dm-bbr: Device setup failed";
+		goto out3;
+	}
+
+	ti->private = bbr_id;
+	return 0;
+
+out3:
+	dm_put_device(ti, bbr_id->dev);
+out2:
+	bbr_free_private(bbr_id);
+out1:
+	return rc;
+}
+
+static void bbr_dtr(struct dm_target *ti)
+{
+	struct bbr_private *bbr_id = ti->private;
+
+	dm_put_device(ti, bbr_id->dev);
+	bbr_free_private(bbr_id);
+}
+
+static int bbr_map(struct dm_target *ti, struct bio *bio,
+		   union map_info *map_context)
+{
+	struct bbr_private *bbr_id = ti->private;
+	struct dm_bio_details *bbr_io;
+	unsigned long flags;
+	int rc = 1;
+
+	bio->bi_sector += bbr_id->offset;
+
+	if (atomic_read(&bbr_id->in_use_replacement_blks) == 0 ||
+	    !bbr_remap_probe(bbr_id, bio->bi_sector, bio_sectors(bio))) {
+		/* No existing remaps or this request doesn't
+		 * contain any remapped sectors.
+		 */
+		bio->bi_bdev = bbr_id->dev->bdev;
+
+		bbr_io = mempool_alloc(bbr_io_pool, GFP_NOIO);
+		dm_bio_record(bbr_io, bio);
+		map_context->ptr = bbr_io;
+	} else {
+		/* This request has at least one remapped sector.
+		 * Give it to the work-queue for processing.
+		 */
+		map_context->ptr = NULL;
+		spin_lock_irqsave(&bbr_id->remap_ios_lock, flags);
+		bio_list_add(&bbr_id->remap_ios, bio);
+		spin_unlock_irqrestore(&bbr_id->remap_ios_lock, flags);
+
+		queue_work(dm_bbr_wq, &bbr_id->remap_work);
+		rc = 0;
+	}
+
+	return rc;
+}
+
+static int bbr_status(struct dm_target *ti, status_type_t type,
+		      char *result, unsigned int maxlen)
+{
+	struct bbr_private *bbr_id = ti->private;
+	char b[BDEVNAME_SIZE];
+
+	switch (type) {
+	case STATUSTYPE_INFO:
+		result[0] = '\0';
+		break;
+
+	case STATUSTYPE_TABLE:
+		snprintf(result, maxlen, "%s "PFU64" "PFU64" "PFU64" "PFU64" "PFU64" "PFU64" %u",
+			 format_dev_t(b, bbr_id->dev->bdev->bd_dev),
+			 bbr_id->offset, bbr_id->lba_table1, bbr_id->lba_table2,
+			 bbr_id->nr_sects_bbr_table,
+			 bbr_id->start_replacement_sect,
+			 bbr_id->nr_replacement_blks,
+			 bbr_id->blksize_in_sects << SECTOR_SHIFT);
+		 break;
+	}
+	return 0;
+}
+
+static struct target_type bbr_target = {
+	.name	= "bbr",
+	.version= {1, 0, 1},
+	.module	= THIS_MODULE,
+	.ctr	= bbr_ctr,
+	.dtr	= bbr_dtr,
+	.map	= bbr_map,
+	.end_io	= bbr_endio,
+	.status	= bbr_status,
+};
+
+int __init dm_bbr_init(void)
+{
+	int rc;
+
+	rc = dm_register_target(&bbr_target);
+	if (rc) {
+		DMERR("dm-bbr: error registering target.");
+		goto err1;
+	}
+
+	bbr_remap_cache = kmem_cache_create("bbr-remap",
+					    sizeof(struct bbr_runtime_remap),
+					    0, SLAB_HWCACHE_ALIGN, NULL, NULL);
+	if (!bbr_remap_cache) {
+		DMERR("dm-bbr: error creating remap cache.");
+		rc = ENOMEM;
+		goto err2;
+	}
+
+	bbr_io_cache = kmem_cache_create("bbr-io", sizeof(struct dm_bio_details),
+					 0, SLAB_HWCACHE_ALIGN, NULL, NULL);
+	if (!bbr_io_cache) {
+		DMERR("dm-bbr: error creating io cache.");
+		rc = ENOMEM;
+		goto err3;
+	}
+
+	bbr_io_pool = mempool_create(256, mempool_alloc_slab,
+				     mempool_free_slab, bbr_io_cache);
+	if (!bbr_io_pool) {
+		DMERR("dm-bbr: error creating io mempool.");
+		rc = ENOMEM;
+		goto err4;
+	}
+
+	dm_bbr_wq = create_workqueue("dm-bbr");
+	if (!dm_bbr_wq) {
+		DMERR("dm-bbr: error creating work-queue.");
+		rc = ENOMEM;
+		goto err5;
+	}
+
+	rc = dm_io_get(1);
+	if (rc) {
+		DMERR("dm-bbr: error initializing I/O service.");
+		goto err6;
+	}
+
+	return 0;
+
+err6:
+	destroy_workqueue(dm_bbr_wq);
+err5:
+	mempool_destroy(bbr_io_pool);
+err4:
+	kmem_cache_destroy(bbr_io_cache);
+err3:
+	kmem_cache_destroy(bbr_remap_cache);
+err2:
+	dm_unregister_target(&bbr_target);
+err1:
+	return rc;
+}
+
+void __exit dm_bbr_exit(void)
+{
+	dm_io_put(1);
+	destroy_workqueue(dm_bbr_wq);
+	mempool_destroy(bbr_io_pool);
+	kmem_cache_destroy(bbr_io_cache);
+	kmem_cache_destroy(bbr_remap_cache);
+	dm_unregister_target(&bbr_target);
+}
+
+module_init(dm_bbr_init);
+module_exit(dm_bbr_exit);
+MODULE_LICENSE("GPL");
--- diff/drivers/md/dm-bbr.h	1969-12-31 18:00:00.000000000 -0600
+++ source/drivers/md/dm-bbr.h	2005-02-28 09:30:07.013672800 -0600
@@ -0,0 +1,125 @@
+/*
+ *   (C) Copyright IBM Corp. 2002, 2004
+ *
+ *   This program is free software;  you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation; either version 2 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY;  without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See
+ *   the GNU General Public License for more details.
+ *
+ *   You should have received a copy of the GNU General Public License
+ *   along with this program;  if not, write to the Free Software
+ *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ *
+ * linux/drivers/md/dm-bbr.h
+ *
+ * Bad-block-relocation (BBR) target for device-mapper.
+ *
+ * The BBR target is designed to remap I/O write failures to another safe
+ * location on disk. Note that most disk drives have BBR built into them,
+ * this means that our software BBR will be only activated when all hardware
+ * BBR replacement sectors have been used.
+ */
+
+#define BBR_TABLE_SIGNATURE		0x42627254 /* BbrT */
+#define BBR_ENTRIES_PER_SECT		31
+#define INITIAL_CRC			0xFFFFFFFF
+#define CRC_POLYNOMIAL			0xEDB88320L
+
+/**
+ * Macros to cleanly print 64-bit numbers on both 32-bit and 64-bit machines.
+ * Use these in place of %Ld, %Lu, and %Lx.
+ **/
+#if BITS_PER_LONG > 32
+#define PFU64 "%lu"
+#else
+#define PFU64 "%Lu"
+#endif
+
+/**
+ * struct bbr_table_entry
+ * @bad_sect:		LBA of bad location.
+ * @replacement_sect:	LBA of new location.
+ *
+ * Structure to describe one BBR remap.
+ **/
+struct bbr_table_entry {
+	u64 bad_sect;
+	u64 replacement_sect;
+};
+
+/**
+ * struct bbr_table
+ * @signature:		Signature on each BBR table sector.
+ * @crc:		CRC for this table sector.
+ * @sequence_number:	Used to resolve conflicts when primary and secondary
+ *			tables do not match.
+ * @in_use_cnt:		Number of in-use table entries.
+ * @entries:		Actual table of remaps.
+ *
+ * Structure to describe each sector of the metadata table. Each sector in this
+ * table can describe 31 remapped sectors.
+ **/
+struct bbr_table {
+	u32			signature;
+	u32			crc;
+	u32			sequence_number;
+	u32			in_use_cnt;
+	struct bbr_table_entry	entries[BBR_ENTRIES_PER_SECT];
+};
+
+/**
+ * struct bbr_runtime_remap
+ *
+ * Node in the binary tree used to keep track of remaps.
+ **/
+struct bbr_runtime_remap {
+	struct bbr_table_entry		remap;
+	struct bbr_runtime_remap	*left;
+	struct bbr_runtime_remap	*right;
+};
+
+/**
+ * struct bbr_private
+ * @dev:			Info about underlying device.
+ * @bbr_table:			Copy of metadata table.
+ * @remap_root:			Binary tree containing all remaps.
+ * @remap_root_lock:		Lock for the binary tree.
+ * @remap_work:			For adding work items to the work-queue.
+ * @remap_ios:			List of I/Os for the work-queue to handle.
+ * @remap_ios_lock:		Lock for the remap_ios list.
+ * @offset:			LBA of data area.
+ * @lba_table1:			LBA of primary BBR table.
+ * @lba_table2:			LBA of secondary BBR table.
+ * @nr_sects_bbr_table:		Size of each BBR table.
+ * @nr_replacement_blks:	Number of replacement blocks.
+ * @start_replacement_sect:	LBA of start of replacement blocks.
+ * @blksize_in_sects:		Size of each block.
+ * @in_use_replacement_blks:	Current number of remapped blocks.
+ *
+ * Private data for each BBR target.
+ **/
+struct bbr_private {
+	struct dm_dev			*dev;
+	struct bbr_table		*bbr_table;
+	struct bbr_runtime_remap	*remap_root;
+	spinlock_t			remap_root_lock;
+
+	struct work_struct		remap_work;
+	struct bio_list			remap_ios;
+	spinlock_t			remap_ios_lock;
+
+	u64				offset;
+	u64				lba_table1;
+	u64				lba_table2;
+	u64				nr_sects_bbr_table;
+	u64				start_replacement_sect;
+	u64				nr_replacement_blks;
+	u32				blksize_in_sects;
+	atomic_t			in_use_replacement_blks;
+};
+