/*
   * Block Translation Table
   * Copyright (c) 2014-2015, Intel Corporation.
   *
   * This program is free software; you can redistribute it and/or modify it
   * under the terms and conditions of the GNU General Public License,
   * version 2, as published by the Free Software Foundation.
   *
   * This program is distributed in the hope 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.
   */
  #include <linux/highmem.h>
  #include <linux/debugfs.h>
  #include <linux/blkdev.h>
  #include <linux/module.h>
  #include <linux/device.h>
  #include <linux/mutex.h>
  #include <linux/hdreg.h>
  #include <linux/genhd.h>
  #include <linux/sizes.h>
  #include <linux/ndctl.h>
  #include <linux/fs.h>
  #include <linux/nd.h>
  #include "btt.h"
  #include "nd.h"
  
  enum log_ent_request {
  	LOG_NEW_ENT = 0,
  	LOG_OLD_ENT
  };
  
  static int btt_major;
  
  static int arena_read_bytes(struct arena_info *arena, resource_size_t offset,
  		void *buf, size_t n)
  {
  	struct nd_btt *nd_btt = arena->nd_btt;
  	struct nd_namespace_common *ndns = nd_btt->ndns;
  
  	/* arena offsets are 4K from the base of the device */
  	offset += SZ_4K;
  	return nvdimm_read_bytes(ndns, offset, buf, n);
  }
  
  static int arena_write_bytes(struct arena_info *arena, resource_size_t offset,
  		void *buf, size_t n)
  {
  	struct nd_btt *nd_btt = arena->nd_btt;
  	struct nd_namespace_common *ndns = nd_btt->ndns;
  
  	/* arena offsets are 4K from the base of the device */
  	offset += SZ_4K;
  	return nvdimm_write_bytes(ndns, offset, buf, n);
  }
  
  static int btt_info_write(struct arena_info *arena, struct btt_sb *super)
  {
  	int ret;
  
  	ret = arena_write_bytes(arena, arena->info2off, super,
  			sizeof(struct btt_sb));
  	if (ret)
  		return ret;
  
  	return arena_write_bytes(arena, arena->infooff, super,
  			sizeof(struct btt_sb));
  }
  
  static int btt_info_read(struct arena_info *arena, struct btt_sb *super)
  {
  	WARN_ON(!super);
  	return arena_read_bytes(arena, arena->infooff, super,
  			sizeof(struct btt_sb));
  }
  
  /*
   * 'raw' version of btt_map write
   * Assumptions:
   *   mapping is in little-endian
   *   mapping contains 'E' and 'Z' flags as desired
   */
  static int __btt_map_write(struct arena_info *arena, u32 lba, __le32 mapping)
  {
  	u64 ns_off = arena->mapoff + (lba * MAP_ENT_SIZE);
  
  	WARN_ON(lba >= arena->external_nlba);
  	return arena_write_bytes(arena, ns_off, &mapping, MAP_ENT_SIZE);
  }
  
  static int btt_map_write(struct arena_info *arena, u32 lba, u32 mapping,
  			u32 z_flag, u32 e_flag)
  {
  	u32 ze;
  	__le32 mapping_le;
  
  	/*
  	 * This 'mapping' is supposed to be just the LBA mapping, without
  	 * any flags set, so strip the flag bits.
  	 */
  	mapping &= MAP_LBA_MASK;
  
  	ze = (z_flag << 1) + e_flag;
  	switch (ze) {
  	case 0:
  		/*
  		 * We want to set neither of the Z or E flags, and
  		 * in the actual layout, this means setting the bit
  		 * positions of both to '1' to indicate a 'normal'
  		 * map entry
  		 */
  		mapping |= MAP_ENT_NORMAL;
  		break;
  	case 1:
  		mapping |= (1 << MAP_ERR_SHIFT);
  		break;
  	case 2:
  		mapping |= (1 << MAP_TRIM_SHIFT);
  		break;
  	default:
  		/*
  		 * The case where Z and E are both sent in as '1' could be
  		 * construed as a valid 'normal' case, but we decide not to,
  		 * to avoid confusion
  		 */
  		WARN_ONCE(1, "Invalid use of Z and E flags
  ");
  		return -EIO;
  	}
  
  	mapping_le = cpu_to_le32(mapping);
  	return __btt_map_write(arena, lba, mapping_le);
  }
  
  static int btt_map_read(struct arena_info *arena, u32 lba, u32 *mapping,
  			int *trim, int *error)
  {
  	int ret;
  	__le32 in;
  	u32 raw_mapping, postmap, ze, z_flag, e_flag;
  	u64 ns_off = arena->mapoff + (lba * MAP_ENT_SIZE);
  
  	WARN_ON(lba >= arena->external_nlba);
  
  	ret = arena_read_bytes(arena, ns_off, &in, MAP_ENT_SIZE);
  	if (ret)
  		return ret;
  
  	raw_mapping = le32_to_cpu(in);
  
  	z_flag = (raw_mapping & MAP_TRIM_MASK) >> MAP_TRIM_SHIFT;
  	e_flag = (raw_mapping & MAP_ERR_MASK) >> MAP_ERR_SHIFT;
  	ze = (z_flag << 1) + e_flag;
  	postmap = raw_mapping & MAP_LBA_MASK;
  
  	/* Reuse the {z,e}_flag variables for *trim and *error */
  	z_flag = 0;
  	e_flag = 0;
  
  	switch (ze) {
  	case 0:
  		/* Initial state. Return postmap = premap */
  		*mapping = lba;
  		break;
  	case 1:
  		*mapping = postmap;
  		e_flag = 1;
  		break;
  	case 2:
  		*mapping = postmap;
  		z_flag = 1;
  		break;
  	case 3:
  		*mapping = postmap;
  		break;
  	default:
  		return -EIO;
  	}
  
  	if (trim)
  		*trim = z_flag;
  	if (error)
  		*error = e_flag;
  
  	return ret;
  }
  
  static int btt_log_read_pair(struct arena_info *arena, u32 lane,
  			struct log_entry *ent)
  {
  	WARN_ON(!ent);
  	return arena_read_bytes(arena,
  			arena->logoff + (2 * lane * LOG_ENT_SIZE), ent,
  			2 * LOG_ENT_SIZE);
  }
  
  static struct dentry *debugfs_root;
  
  static void arena_debugfs_init(struct arena_info *a, struct dentry *parent,
  				int idx)
  {
  	char dirname[32];
  	struct dentry *d;
  
  	/* If for some reason, parent bttN was not created, exit */
  	if (!parent)
  		return;
  
  	snprintf(dirname, 32, "arena%d", idx);
  	d = debugfs_create_dir(dirname, parent);
  	if (IS_ERR_OR_NULL(d))
  		return;
  	a->debugfs_dir = d;
  
  	debugfs_create_x64("size", S_IRUGO, d, &a->size);
  	debugfs_create_x64("external_lba_start", S_IRUGO, d,
  				&a->external_lba_start);
  	debugfs_create_x32("internal_nlba", S_IRUGO, d, &a->internal_nlba);
  	debugfs_create_u32("internal_lbasize", S_IRUGO, d,
  				&a->internal_lbasize);
  	debugfs_create_x32("external_nlba", S_IRUGO, d, &a->external_nlba);
  	debugfs_create_u32("external_lbasize", S_IRUGO, d,
  				&a->external_lbasize);
  	debugfs_create_u32("nfree", S_IRUGO, d, &a->nfree);
  	debugfs_create_u16("version_major", S_IRUGO, d, &a->version_major);
  	debugfs_create_u16("version_minor", S_IRUGO, d, &a->version_minor);
  	debugfs_create_x64("nextoff", S_IRUGO, d, &a->nextoff);
  	debugfs_create_x64("infooff", S_IRUGO, d, &a->infooff);
  	debugfs_create_x64("dataoff", S_IRUGO, d, &a->dataoff);
  	debugfs_create_x64("mapoff", S_IRUGO, d, &a->mapoff);
  	debugfs_create_x64("logoff", S_IRUGO, d, &a->logoff);
  	debugfs_create_x64("info2off", S_IRUGO, d, &a->info2off);
  	debugfs_create_x32("flags", S_IRUGO, d, &a->flags);
  }
  
  static void btt_debugfs_init(struct btt *btt)
  {
  	int i = 0;
  	struct arena_info *arena;
  
  	btt->debugfs_dir = debugfs_create_dir(dev_name(&btt->nd_btt->dev),
  						debugfs_root);
  	if (IS_ERR_OR_NULL(btt->debugfs_dir))
  		return;
  
  	list_for_each_entry(arena, &btt->arena_list, list) {
  		arena_debugfs_init(arena, btt->debugfs_dir, i);
  		i++;
  	}
  }
  
  /*
   * This function accepts two log entries, and uses the
   * sequence number to find the 'older' entry.
   * It also updates the sequence number in this old entry to
   * make it the 'new' one if the mark_flag is set.
   * Finally, it returns which of the entries was the older one.
   *
   * TODO The logic feels a bit kludge-y. make it better..
   */
  static int btt_log_get_old(struct log_entry *ent)
  {
  	int old;
  
  	/*
  	 * the first ever time this is seen, the entry goes into [0]
  	 * the next time, the following logic works out to put this
  	 * (next) entry into [1]
  	 */
  	if (ent[0].seq == 0) {
  		ent[0].seq = cpu_to_le32(1);
  		return 0;
  	}
  
  	if (ent[0].seq == ent[1].seq)
  		return -EINVAL;
  	if (le32_to_cpu(ent[0].seq) + le32_to_cpu(ent[1].seq) > 5)
  		return -EINVAL;
  
  	if (le32_to_cpu(ent[0].seq) < le32_to_cpu(ent[1].seq)) {
  		if (le32_to_cpu(ent[1].seq) - le32_to_cpu(ent[0].seq) == 1)
  			old = 0;
  		else
  			old = 1;
  	} else {
  		if (le32_to_cpu(ent[0].seq) - le32_to_cpu(ent[1].seq) == 1)
  			old = 1;
  		else
  			old = 0;
  	}
  
  	return old;
  }
  
  static struct device *to_dev(struct arena_info *arena)
  {
  	return &arena->nd_btt->dev;
  }
  
  /*
   * This function copies the desired (old/new) log entry into ent if
   * it is not NULL. It returns the sub-slot number (0 or 1)
   * where the desired log entry was found. Negative return values
   * indicate errors.
   */
  static int btt_log_read(struct arena_info *arena, u32 lane,
  			struct log_entry *ent, int old_flag)
  {
  	int ret;
  	int old_ent, ret_ent;
  	struct log_entry log[2];
  
  	ret = btt_log_read_pair(arena, lane, log);
  	if (ret)
  		return -EIO;
  
  	old_ent = btt_log_get_old(log);
  	if (old_ent < 0 || old_ent > 1) {
  		dev_info(to_dev(arena),
  				"log corruption (%d): lane %d seq [%d, %d]
  ",
  			old_ent, lane, log[0].seq, log[1].seq);
  		/* TODO set error state? */
  		return -EIO;
  	}
  
  	ret_ent = (old_flag ? old_ent : (1 - old_ent));
  
  	if (ent != NULL)
  		memcpy(ent, &log[ret_ent], LOG_ENT_SIZE);
  
  	return ret_ent;
  }
  
  /*
   * This function commits a log entry to media
   * It does _not_ prepare the freelist entry for the next write
   * btt_flog_write is the wrapper for updating the freelist elements
   */
  static int __btt_log_write(struct arena_info *arena, u32 lane,
  			u32 sub, struct log_entry *ent)
  {
  	int ret;
  	/*
  	 * Ignore the padding in log_entry for calculating log_half.
  	 * The entry is 'committed' when we write the sequence number,
  	 * and we want to ensure that that is the last thing written.
  	 * We don't bother writing the padding as that would be extra
  	 * media wear and write amplification
  	 */
  	unsigned int log_half = (LOG_ENT_SIZE - 2 * sizeof(u64)) / 2;
  	u64 ns_off = arena->logoff + (((2 * lane) + sub) * LOG_ENT_SIZE);
  	void *src = ent;
  
  	/* split the 16B write into atomic, durable halves */
  	ret = arena_write_bytes(arena, ns_off, src, log_half);
  	if (ret)
  		return ret;
  
  	ns_off += log_half;
  	src += log_half;
  	return arena_write_bytes(arena, ns_off, src, log_half);
  }
  
  static int btt_flog_write(struct arena_info *arena, u32 lane, u32 sub,
  			struct log_entry *ent)
  {
  	int ret;
  
  	ret = __btt_log_write(arena, lane, sub, ent);
  	if (ret)
  		return ret;
  
  	/* prepare the next free entry */
  	arena->freelist[lane].sub = 1 - arena->freelist[lane].sub;
  	if (++(arena->freelist[lane].seq) == 4)
  		arena->freelist[lane].seq = 1;
  	arena->freelist[lane].block = le32_to_cpu(ent->old_map);
  
  	return ret;
  }
  
  /*
   * This function initializes the BTT map to the initial state, which is
   * all-zeroes, and indicates an identity mapping
   */
  static int btt_map_init(struct arena_info *arena)
  {
  	int ret = -EINVAL;
  	void *zerobuf;
  	size_t offset = 0;
  	size_t chunk_size = SZ_2M;
  	size_t mapsize = arena->logoff - arena->mapoff;
  
  	zerobuf = kzalloc(chunk_size, GFP_KERNEL);
  	if (!zerobuf)
  		return -ENOMEM;
  
  	while (mapsize) {
  		size_t size = min(mapsize, chunk_size);
  
  		ret = arena_write_bytes(arena, arena->mapoff + offset, zerobuf,
  				size);
  		if (ret)
  			goto free;
  
  		offset += size;
  		mapsize -= size;
  		cond_resched();
  	}
  
   free:
  	kfree(zerobuf);
  	return ret;
  }
  
  /*
   * This function initializes the BTT log with 'fake' entries pointing
   * to the initial reserved set of blocks as being free
   */
  static int btt_log_init(struct arena_info *arena)
  {
  	int ret;
  	u32 i;
  	struct log_entry log, zerolog;
  
  	memset(&zerolog, 0, sizeof(zerolog));
  
  	for (i = 0; i < arena->nfree; i++) {
  		log.lba = cpu_to_le32(i);
  		log.old_map = cpu_to_le32(arena->external_nlba + i);
  		log.new_map = cpu_to_le32(arena->external_nlba + i);
  		log.seq = cpu_to_le32(LOG_SEQ_INIT);
  		ret = __btt_log_write(arena, i, 0, &log);
  		if (ret)
  			return ret;
  		ret = __btt_log_write(arena, i, 1, &zerolog);
  		if (ret)
  			return ret;
  	}
  
  	return 0;
  }
  
  static int btt_freelist_init(struct arena_info *arena)
  {
  	int old, new, ret;
  	u32 i, map_entry;
  	struct log_entry log_new, log_old;
  
  	arena->freelist = kcalloc(arena->nfree, sizeof(struct free_entry),
  					GFP_KERNEL);
  	if (!arena->freelist)
  		return -ENOMEM;
  
  	for (i = 0; i < arena->nfree; i++) {
  		old = btt_log_read(arena, i, &log_old, LOG_OLD_ENT);
  		if (old < 0)
  			return old;
  
  		new = btt_log_read(arena, i, &log_new, LOG_NEW_ENT);
  		if (new < 0)
  			return new;
  
  		/* sub points to the next one to be overwritten */
  		arena->freelist[i].sub = 1 - new;
  		arena->freelist[i].seq = nd_inc_seq(le32_to_cpu(log_new.seq));
  		arena->freelist[i].block = le32_to_cpu(log_new.old_map);
  
  		/* This implies a newly created or untouched flog entry */
  		if (log_new.old_map == log_new.new_map)
  			continue;
  
  		/* Check if map recovery is needed */
  		ret = btt_map_read(arena, le32_to_cpu(log_new.lba), &map_entry,
  				NULL, NULL);
  		if (ret)
  			return ret;
  		if ((le32_to_cpu(log_new.new_map) != map_entry) &&
  				(le32_to_cpu(log_new.old_map) == map_entry)) {
  			/*
  			 * Last transaction wrote the flog, but wasn't able
  			 * to complete the map write. So fix up the map.
  			 */
  			ret = btt_map_write(arena, le32_to_cpu(log_new.lba),
  					le32_to_cpu(log_new.new_map), 0, 0);
  			if (ret)
  				return ret;
  		}
  
  	}
  
  	return 0;
  }
  
  static int btt_rtt_init(struct arena_info *arena)
  {
  	arena->rtt = kcalloc(arena->nfree, sizeof(u32), GFP_KERNEL);
  	if (arena->rtt == NULL)
  		return -ENOMEM;
  
  	return 0;
  }
  
  static int btt_maplocks_init(struct arena_info *arena)
  {
  	u32 i;
  
  	arena->map_locks = kcalloc(arena->nfree, sizeof(struct aligned_lock),
  				GFP_KERNEL);
  	if (!arena->map_locks)
  		return -ENOMEM;
  
  	for (i = 0; i < arena->nfree; i++)
  		spin_lock_init(&arena->map_locks[i].lock);
  
  	return 0;
  }
  
  static struct arena_info *alloc_arena(struct btt *btt, size_t size,
  				size_t start, size_t arena_off)
  {
  	struct arena_info *arena;
  	u64 logsize, mapsize, datasize;
  	u64 available = size;
  
  	arena = kzalloc(sizeof(struct arena_info), GFP_KERNEL);
  	if (!arena)
  		return NULL;
  	arena->nd_btt = btt->nd_btt;
  
  	if (!size)
  		return arena;
  
  	arena->size = size;
  	arena->external_lba_start = start;
  	arena->external_lbasize = btt->lbasize;
  	arena->internal_lbasize = roundup(arena->external_lbasize,
  					INT_LBASIZE_ALIGNMENT);
  	arena->nfree = BTT_DEFAULT_NFREE;
  	arena->version_major = 1;
  	arena->version_minor = 1;
  
  	if (available % BTT_PG_SIZE)
  		available -= (available % BTT_PG_SIZE);
  
  	/* Two pages are reserved for the super block and its copy */
  	available -= 2 * BTT_PG_SIZE;
  
  	/* The log takes a fixed amount of space based on nfree */
  	logsize = roundup(2 * arena->nfree * sizeof(struct log_entry),
  				BTT_PG_SIZE);
  	available -= logsize;
  
  	/* Calculate optimal split between map and data area */
  	arena->internal_nlba = div_u64(available - BTT_PG_SIZE,
  			arena->internal_lbasize + MAP_ENT_SIZE);
  	arena->external_nlba = arena->internal_nlba - arena->nfree;
  
  	mapsize = roundup((arena->external_nlba * MAP_ENT_SIZE), BTT_PG_SIZE);
  	datasize = available - mapsize;
  
  	/* 'Absolute' values, relative to start of storage space */
  	arena->infooff = arena_off;
  	arena->dataoff = arena->infooff + BTT_PG_SIZE;
  	arena->mapoff = arena->dataoff + datasize;
  	arena->logoff = arena->mapoff + mapsize;
  	arena->info2off = arena->logoff + logsize;
  	return arena;
  }
  
  static void free_arenas(struct btt *btt)
  {
  	struct arena_info *arena, *next;
  
  	list_for_each_entry_safe(arena, next, &btt->arena_list, list) {
  		list_del(&arena->list);
  		kfree(arena->rtt);
  		kfree(arena->map_locks);
  		kfree(arena->freelist);
  		debugfs_remove_recursive(arena->debugfs_dir);
  		kfree(arena);
  	}
  }
  
  /*
   * This function reads an existing valid btt superblock and
   * populates the corresponding arena_info struct
   */
  static void parse_arena_meta(struct arena_info *arena, struct btt_sb *super,
  				u64 arena_off)
  {
  	arena->internal_nlba = le32_to_cpu(super->internal_nlba);
  	arena->internal_lbasize = le32_to_cpu(super->internal_lbasize);
  	arena->external_nlba = le32_to_cpu(super->external_nlba);
  	arena->external_lbasize = le32_to_cpu(super->external_lbasize);
  	arena->nfree = le32_to_cpu(super->nfree);
  	arena->version_major = le16_to_cpu(super->version_major);
  	arena->version_minor = le16_to_cpu(super->version_minor);
  
  	arena->nextoff = (super->nextoff == 0) ? 0 : (arena_off +
  			le64_to_cpu(super->nextoff));
  	arena->infooff = arena_off;
  	arena->dataoff = arena_off + le64_to_cpu(super->dataoff);
  	arena->mapoff = arena_off + le64_to_cpu(super->mapoff);
  	arena->logoff = arena_off + le64_to_cpu(super->logoff);
  	arena->info2off = arena_off + le64_to_cpu(super->info2off);
  
  	arena->size = (le64_to_cpu(super->nextoff) > 0)
  		? (le64_to_cpu(super->nextoff))
  		: (arena->info2off - arena->infooff + BTT_PG_SIZE);
  
  	arena->flags = le32_to_cpu(super->flags);
  }
  
  static int discover_arenas(struct btt *btt)
  {
  	int ret = 0;
  	struct arena_info *arena;
  	struct btt_sb *super;
  	size_t remaining = btt->rawsize;
  	u64 cur_nlba = 0;
  	size_t cur_off = 0;
  	int num_arenas = 0;
  
  	super = kzalloc(sizeof(*super), GFP_KERNEL);
  	if (!super)
  		return -ENOMEM;
  
  	while (remaining) {
  		/* Alloc memory for arena */
  		arena = alloc_arena(btt, 0, 0, 0);
  		if (!arena) {
  			ret = -ENOMEM;
  			goto out_super;
  		}
  
  		arena->infooff = cur_off;
  		ret = btt_info_read(arena, super);
  		if (ret)
  			goto out;
  
  		if (!nd_btt_arena_is_valid(btt->nd_btt, super)) {
  			if (remaining == btt->rawsize) {
  				btt->init_state = INIT_NOTFOUND;
  				dev_info(to_dev(arena), "No existing arenas
  ");
  				goto out;
  			} else {
  				dev_info(to_dev(arena),
  						"Found corrupted metadata!
  ");
  				ret = -ENODEV;
  				goto out;
  			}
  		}
  
  		arena->external_lba_start = cur_nlba;
  		parse_arena_meta(arena, super, cur_off);
  
  		ret = btt_freelist_init(arena);
  		if (ret)
  			goto out;
  
  		ret = btt_rtt_init(arena);
  		if (ret)
  			goto out;
  
  		ret = btt_maplocks_init(arena);
  		if (ret)
  			goto out;
  
  		list_add_tail(&arena->list, &btt->arena_list);
  
  		remaining -= arena->size;
  		cur_off += arena->size;
  		cur_nlba += arena->external_nlba;
  		num_arenas++;
  
  		if (arena->nextoff == 0)
  			break;
  	}
  	btt->num_arenas = num_arenas;
  	btt->nlba = cur_nlba;
  	btt->init_state = INIT_READY;
  
  	kfree(super);
  	return ret;
  
   out:
  	kfree(arena);
  	free_arenas(btt);
   out_super:
  	kfree(super);
  	return ret;
  }
  
  static int create_arenas(struct btt *btt)
  {
  	size_t remaining = btt->rawsize;
  	size_t cur_off = 0;
  
  	while (remaining) {
  		struct arena_info *arena;
  		size_t arena_size = min_t(u64, ARENA_MAX_SIZE, remaining);
  
  		remaining -= arena_size;
  		if (arena_size < ARENA_MIN_SIZE)
  			break;
  
  		arena = alloc_arena(btt, arena_size, btt->nlba, cur_off);
  		if (!arena) {
  			free_arenas(btt);
  			return -ENOMEM;
  		}
  		btt->nlba += arena->external_nlba;
  		if (remaining >= ARENA_MIN_SIZE)
  			arena->nextoff = arena->size;
  		else
  			arena->nextoff = 0;
  		cur_off += arena_size;
  		list_add_tail(&arena->list, &btt->arena_list);
  	}
  
  	return 0;
  }
  
  /*
   * This function completes arena initialization by writing
   * all the metadata.
   * It is only called for an uninitialized arena when a write
   * to that arena occurs for the first time.
   */
  static int btt_arena_write_layout(struct arena_info *arena)
  {
  	int ret;
  	u64 sum;
  	struct btt_sb *super;
  	struct nd_btt *nd_btt = arena->nd_btt;
  	const u8 *parent_uuid = nd_dev_to_uuid(&nd_btt->ndns->dev);
  
  	ret = btt_map_init(arena);
  	if (ret)
  		return ret;
  
  	ret = btt_log_init(arena);
  	if (ret)
  		return ret;
  
  	super = kzalloc(sizeof(struct btt_sb), GFP_NOIO);
  	if (!super)
  		return -ENOMEM;
  
  	strncpy(super->signature, BTT_SIG, BTT_SIG_LEN);
  	memcpy(super->uuid, nd_btt->uuid, 16);
  	memcpy(super->parent_uuid, parent_uuid, 16);
  	super->flags = cpu_to_le32(arena->flags);
  	super->version_major = cpu_to_le16(arena->version_major);
  	super->version_minor = cpu_to_le16(arena->version_minor);
  	super->external_lbasize = cpu_to_le32(arena->external_lbasize);
  	super->external_nlba = cpu_to_le32(arena->external_nlba);
  	super->internal_lbasize = cpu_to_le32(arena->internal_lbasize);
  	super->internal_nlba = cpu_to_le32(arena->internal_nlba);
  	super->nfree = cpu_to_le32(arena->nfree);
  	super->infosize = cpu_to_le32(sizeof(struct btt_sb));
  	super->nextoff = cpu_to_le64(arena->nextoff);
  	/*
  	 * Subtract arena->infooff (arena start) so numbers are relative
  	 * to 'this' arena
  	 */
  	super->dataoff = cpu_to_le64(arena->dataoff - arena->infooff);
  	super->mapoff = cpu_to_le64(arena->mapoff - arena->infooff);
  	super->logoff = cpu_to_le64(arena->logoff - arena->infooff);
  	super->info2off = cpu_to_le64(arena->info2off - arena->infooff);
  
  	super->flags = 0;
  	sum = nd_sb_checksum((struct nd_gen_sb *) super);
  	super->checksum = cpu_to_le64(sum);
  
  	ret = btt_info_write(arena, super);
  
  	kfree(super);
  	return ret;
  }
  
  /*
   * This function completes the initialization for the BTT namespace
   * such that it is ready to accept IOs
   */
  static int btt_meta_init(struct btt *btt)
  {
  	int ret = 0;
  	struct arena_info *arena;
  
  	mutex_lock(&btt->init_lock);
  	list_for_each_entry(arena, &btt->arena_list, list) {
  		ret = btt_arena_write_layout(arena);
  		if (ret)
  			goto unlock;
  
  		ret = btt_freelist_init(arena);
  		if (ret)
  			goto unlock;
  
  		ret = btt_rtt_init(arena);
  		if (ret)
  			goto unlock;
  
  		ret = btt_maplocks_init(arena);
  		if (ret)
  			goto unlock;
  	}
  
  	btt->init_state = INIT_READY;
  
   unlock:
  	mutex_unlock(&btt->init_lock);
  	return ret;
  }
  
  static u32 btt_meta_size(struct btt *btt)
  {
  	return btt->lbasize - btt->sector_size;
  }
  
  /*
   * This function calculates the arena in which the given LBA lies
   * by doing a linear walk. This is acceptable since we expect only
   * a few arenas. If we have backing devices that get much larger,
   * we can construct a balanced binary tree of arenas at init time
   * so that this range search becomes faster.
   */
  static int lba_to_arena(struct btt *btt, sector_t sector, __u32 *premap,
  				struct arena_info **arena)
  {
  	struct arena_info *arena_list;
  	__u64 lba = div_u64(sector << SECTOR_SHIFT, btt->sector_size);
  
  	list_for_each_entry(arena_list, &btt->arena_list, list) {
  		if (lba < arena_list->external_nlba) {
  			*arena = arena_list;
  			*premap = lba;
  			return 0;
  		}
  		lba -= arena_list->external_nlba;
  	}
  
  	return -EIO;
  }
  
  /*
   * The following (lock_map, unlock_map) are mostly just to improve
   * readability, since they index into an array of locks
   */
  static void lock_map(struct arena_info *arena, u32 premap)
  		__acquires(&arena->map_locks[idx].lock)
  {
  	u32 idx = (premap * MAP_ENT_SIZE / L1_CACHE_BYTES) % arena->nfree;
  
  	spin_lock(&arena->map_locks[idx].lock);
  }
  
  static void unlock_map(struct arena_info *arena, u32 premap)
  		__releases(&arena->map_locks[idx].lock)
  {
  	u32 idx = (premap * MAP_ENT_SIZE / L1_CACHE_BYTES) % arena->nfree;
  
  	spin_unlock(&arena->map_locks[idx].lock);
  }
  
  static u64 to_namespace_offset(struct arena_info *arena, u64 lba)
  {
  	return arena->dataoff + ((u64)lba * arena->internal_lbasize);
  }
  
  static int btt_data_read(struct arena_info *arena, struct page *page,
  			unsigned int off, u32 lba, u32 len)
  {
  	int ret;
  	u64 nsoff = to_namespace_offset(arena, lba);
  	void *mem = kmap_atomic(page);
  
  	ret = arena_read_bytes(arena, nsoff, mem + off, len);
  	kunmap_atomic(mem);
  
  	return ret;
  }
  
  static int btt_data_write(struct arena_info *arena, u32 lba,
  			struct page *page, unsigned int off, u32 len)
  {
  	int ret;
  	u64 nsoff = to_namespace_offset(arena, lba);
  	void *mem = kmap_atomic(page);
  
  	ret = arena_write_bytes(arena, nsoff, mem + off, len);
  	kunmap_atomic(mem);
  
  	return ret;
  }
  
  static void zero_fill_data(struct page *page, unsigned int off, u32 len)
  {
  	void *mem = kmap_atomic(page);
  
  	memset(mem + off, 0, len);
  	kunmap_atomic(mem);
  }
  
  #ifdef CONFIG_BLK_DEV_INTEGRITY
  static int btt_rw_integrity(struct btt *btt, struct bio_integrity_payload *bip,
  			struct arena_info *arena, u32 postmap, int rw)
  {
  	unsigned int len = btt_meta_size(btt);
  	u64 meta_nsoff;
  	int ret = 0;
  
  	if (bip == NULL)
  		return 0;
  
  	meta_nsoff = to_namespace_offset(arena, postmap) + btt->sector_size;
  
  	while (len) {
  		unsigned int cur_len;
  		struct bio_vec bv;
  		void *mem;
  
  		bv = bvec_iter_bvec(bip->bip_vec, bip->bip_iter);
  		/*
  		 * The 'bv' obtained from bvec_iter_bvec has its .bv_len and
  		 * .bv_offset already adjusted for iter->bi_bvec_done, and we
  		 * can use those directly
  		 */
  
  		cur_len = min(len, bv.bv_len);
  		mem = kmap_atomic(bv.bv_page);
  		if (rw)
  			ret = arena_write_bytes(arena, meta_nsoff,
  					mem + bv.bv_offset, cur_len);
  		else
  			ret = arena_read_bytes(arena, meta_nsoff,
  					mem + bv.bv_offset, cur_len);
  
  		kunmap_atomic(mem);
  		if (ret)
  			return ret;
  
  		len -= cur_len;
  		meta_nsoff += cur_len;
  		bvec_iter_advance(bip->bip_vec, &bip->bip_iter, cur_len);
  	}
  
  	return ret;
  }
  
  #else /* CONFIG_BLK_DEV_INTEGRITY */
  static int btt_rw_integrity(struct btt *btt, struct bio_integrity_payload *bip,
  			struct arena_info *arena, u32 postmap, int rw)
  {
  	return 0;
  }
  #endif
  
  static int btt_read_pg(struct btt *btt, struct bio_integrity_payload *bip,
  			struct page *page, unsigned int off, sector_t sector,
  			unsigned int len)
  {
  	int ret = 0;
  	int t_flag, e_flag;
  	struct arena_info *arena = NULL;
  	u32 lane = 0, premap, postmap;
  
  	while (len) {
  		u32 cur_len;
  
  		lane = nd_region_acquire_lane(btt->nd_region);
  
  		ret = lba_to_arena(btt, sector, &premap, &arena);
  		if (ret)
  			goto out_lane;
  
  		cur_len = min(btt->sector_size, len);
  
  		ret = btt_map_read(arena, premap, &postmap, &t_flag, &e_flag);
  		if (ret)
  			goto out_lane;
  
  		/*
  		 * We loop to make sure that the post map LBA didn't change
  		 * from under us between writing the RTT and doing the actual
  		 * read.
  		 */
  		while (1) {
  			u32 new_map;
  
  			if (t_flag) {
  				zero_fill_data(page, off, cur_len);
  				goto out_lane;
  			}
  
  			if (e_flag) {
  				ret = -EIO;
  				goto out_lane;
  			}
  
  			arena->rtt[lane] = RTT_VALID | postmap;
  			/*
  			 * Barrier to make sure this write is not reordered
  			 * to do the verification map_read before the RTT store
  			 */
  			barrier();
  
  			ret = btt_map_read(arena, premap, &new_map, &t_flag,
  						&e_flag);
  			if (ret)
  				goto out_rtt;
  
  			if (postmap == new_map)
  				break;
  
  			postmap = new_map;
  		}
  
  		ret = btt_data_read(arena, page, off, postmap, cur_len);
  		if (ret)
  			goto out_rtt;
  
  		if (bip) {
  			ret = btt_rw_integrity(btt, bip, arena, postmap, READ);
  			if (ret)
  				goto out_rtt;
  		}
  
  		arena->rtt[lane] = RTT_INVALID;
  		nd_region_release_lane(btt->nd_region, lane);
  
  		len -= cur_len;
  		off += cur_len;
  		sector += btt->sector_size >> SECTOR_SHIFT;
  	}
  
  	return 0;
  
   out_rtt:
  	arena->rtt[lane] = RTT_INVALID;
   out_lane:
  	nd_region_release_lane(btt->nd_region, lane);
  	return ret;
  }
  
  static int btt_write_pg(struct btt *btt, struct bio_integrity_payload *bip,
  			sector_t sector, struct page *page, unsigned int off,
  			unsigned int len)
  {
  	int ret = 0;
  	struct arena_info *arena = NULL;
  	u32 premap = 0, old_postmap, new_postmap, lane = 0, i;
  	struct log_entry log;
  	int sub;
  
  	while (len) {
  		u32 cur_len;
  
  		lane = nd_region_acquire_lane(btt->nd_region);
  
  		ret = lba_to_arena(btt, sector, &premap, &arena);
  		if (ret)
  			goto out_lane;
  		cur_len = min(btt->sector_size, len);
  
  		if ((arena->flags & IB_FLAG_ERROR_MASK) != 0) {
  			ret = -EIO;
  			goto out_lane;
  		}
  
  		new_postmap = arena->freelist[lane].block;
  
  		/* Wait if the new block is being read from */
  		for (i = 0; i < arena->nfree; i++)
  			while (arena->rtt[i] == (RTT_VALID | new_postmap))
  				cpu_relax();
  
  
  		if (new_postmap >= arena->internal_nlba) {
  			ret = -EIO;
  			goto out_lane;
  		}
  
  		ret = btt_data_write(arena, new_postmap, page, off, cur_len);
  		if (ret)
  			goto out_lane;
  
  		if (bip) {
  			ret = btt_rw_integrity(btt, bip, arena, new_postmap,
  						WRITE);
  			if (ret)
  				goto out_lane;
  		}
  
  		lock_map(arena, premap);
  		ret = btt_map_read(arena, premap, &old_postmap, NULL, NULL);
  		if (ret)
  			goto out_map;
  		if (old_postmap >= arena->internal_nlba) {
  			ret = -EIO;
  			goto out_map;
  		}
  
  		log.lba = cpu_to_le32(premap);
  		log.old_map = cpu_to_le32(old_postmap);
  		log.new_map = cpu_to_le32(new_postmap);
  		log.seq = cpu_to_le32(arena->freelist[lane].seq);
  		sub = arena->freelist[lane].sub;
  		ret = btt_flog_write(arena, lane, sub, &log);
  		if (ret)
  			goto out_map;
  
  		ret = btt_map_write(arena, premap, new_postmap, 0, 0);
  		if (ret)
  			goto out_map;
  
  		unlock_map(arena, premap);
  		nd_region_release_lane(btt->nd_region, lane);
  
  		len -= cur_len;
  		off += cur_len;
  		sector += btt->sector_size >> SECTOR_SHIFT;
  	}
  
  	return 0;
  
   out_map:
  	unlock_map(arena, premap);
   out_lane:
  	nd_region_release_lane(btt->nd_region, lane);
  	return ret;
  }
  
  static int btt_do_bvec(struct btt *btt, struct bio_integrity_payload *bip,
  			struct page *page, unsigned int len, unsigned int off,
  			int rw, sector_t sector)
  {
  	int ret;
  
  	if (rw == READ) {
  		ret = btt_read_pg(btt, bip, page, off, sector, len);
  		flush_dcache_page(page);
  	} else {
  		flush_dcache_page(page);
  		ret = btt_write_pg(btt, bip, sector, page, off, len);
  	}
  
  	return ret;
  }
  
  static blk_qc_t btt_make_request(struct request_queue *q, struct bio *bio)
  {
  	struct bio_integrity_payload *bip = bio_integrity(bio);
  	struct btt *btt = q->queuedata;
  	struct bvec_iter iter;
  	unsigned long start;
  	struct bio_vec bvec;
  	int err = 0, rw;
  	bool do_acct;
  
  	/*
  	 * bio_integrity_enabled also checks if the bio already has an
  	 * integrity payload attached. If it does, we *don't* do a
  	 * bio_integrity_prep here - the payload has been generated by
  	 * another kernel subsystem, and we just pass it through.
  	 */
  	if (bio_integrity_enabled(bio) && bio_integrity_prep(bio)) {
  		bio->bi_error = -EIO;
  		goto out;
  	}
  
  	do_acct = nd_iostat_start(bio, &start);
  	rw = bio_data_dir(bio);
  	bio_for_each_segment(bvec, bio, iter) {
  		unsigned int len = bvec.bv_len;
  
  		BUG_ON(len > PAGE_SIZE);
  		/* Make sure len is in multiples of sector size. */
  		/* XXX is this right? */
  		BUG_ON(len < btt->sector_size);
  		BUG_ON(len % btt->sector_size);
  
  		err = btt_do_bvec(btt, bip, bvec.bv_page, len, bvec.bv_offset,
  				rw, iter.bi_sector);
  		if (err) {
  			dev_info(&btt->nd_btt->dev,
  					"io error in %s sector %lld, len %d,
  ",
  					(rw == READ) ? "READ" : "WRITE",
  					(unsigned long long) iter.bi_sector, len);
  			bio->bi_error = err;
  			break;
  		}
  	}
  	if (do_acct)
  		nd_iostat_end(bio, start);
  
  out:
  	bio_endio(bio);
  	return BLK_QC_T_NONE;
  }
  
  static int btt_rw_page(struct block_device *bdev, sector_t sector,
  		struct page *page, int rw)
  {
  	struct btt *btt = bdev->bd_disk->private_data;
  
  	btt_do_bvec(btt, NULL, page, PAGE_CACHE_SIZE, 0, rw, sector);
  	page_endio(page, rw & WRITE, 0);
  	return 0;
  }
  
  
  static int btt_getgeo(struct block_device *bd, struct hd_geometry *geo)
  {
  	/* some standard values */
  	geo->heads = 1 << 6;
  	geo->sectors = 1 << 5;
  	geo->cylinders = get_capacity(bd->bd_disk) >> 11;
  	return 0;
  }
  
  static const struct block_device_operations btt_fops = {
  	.owner =		THIS_MODULE,
  	.rw_page =		btt_rw_page,
  	.getgeo =		btt_getgeo,
  	.revalidate_disk =	nvdimm_revalidate_disk,
  };
  
  static int btt_blk_init(struct btt *btt)
  {
  	struct nd_btt *nd_btt = btt->nd_btt;
  	struct nd_namespace_common *ndns = nd_btt->ndns;
  
  	/* create a new disk and request queue for btt */
  	btt->btt_queue = blk_alloc_queue(GFP_KERNEL);
  	if (!btt->btt_queue)
  		return -ENOMEM;
  
  	btt->btt_disk = alloc_disk(0);
  	if (!btt->btt_disk) {
  		blk_cleanup_queue(btt->btt_queue);
  		return -ENOMEM;
  	}
  
  	nvdimm_namespace_disk_name(ndns, btt->btt_disk->disk_name);
  	btt->btt_disk->driverfs_dev = &btt->nd_btt->dev;
  	btt->btt_disk->major = btt_major;
  	btt->btt_disk->first_minor = 0;
  	btt->btt_disk->fops = &btt_fops;
  	btt->btt_disk->private_data = btt;
  	btt->btt_disk->queue = btt->btt_queue;
  	btt->btt_disk->flags = GENHD_FL_EXT_DEVT;
  
  	blk_queue_make_request(btt->btt_queue, btt_make_request);
  	blk_queue_logical_block_size(btt->btt_queue, btt->sector_size);
  	blk_queue_max_hw_sectors(btt->btt_queue, UINT_MAX);
  	blk_queue_bounce_limit(btt->btt_queue, BLK_BOUNCE_ANY);
  	queue_flag_set_unlocked(QUEUE_FLAG_NONROT, btt->btt_queue);
  	btt->btt_queue->queuedata = btt;
  
  	set_capacity(btt->btt_disk, 0);
  	add_disk(btt->btt_disk);
  	if (btt_meta_size(btt)) {
  		int rc = nd_integrity_init(btt->btt_disk, btt_meta_size(btt));
  
  		if (rc) {
  			del_gendisk(btt->btt_disk);
  			put_disk(btt->btt_disk);
  			blk_cleanup_queue(btt->btt_queue);
  			return rc;
  		}
  	}
  	set_capacity(btt->btt_disk, btt->nlba * btt->sector_size >> 9);
  	revalidate_disk(btt->btt_disk);
  
  	return 0;
  }
  
  static void btt_blk_cleanup(struct btt *btt)
  {
  	del_gendisk(btt->btt_disk);
  	put_disk(btt->btt_disk);
  	blk_cleanup_queue(btt->btt_queue);
  }
  
  /**
   * btt_init - initialize a block translation table for the given device
   * @nd_btt:	device with BTT geometry and backing device info
   * @rawsize:	raw size in bytes of the backing device
   * @lbasize:	lba size of the backing device
   * @uuid:	A uuid for the backing device - this is stored on media
   * @maxlane:	maximum number of parallel requests the device can handle
   *
   * Initialize a Block Translation Table on a backing device to provide
   * single sector power fail atomicity.
   *
   * Context:
   * Might sleep.
   *
   * Returns:
   * Pointer to a new struct btt on success, NULL on failure.
   */
  static struct btt *btt_init(struct nd_btt *nd_btt, unsigned long long rawsize,
  		u32 lbasize, u8 *uuid, struct nd_region *nd_region)
  {
  	int ret;
  	struct btt *btt;
  	struct device *dev = &nd_btt->dev;
  
  	btt = kzalloc(sizeof(struct btt), GFP_KERNEL);
  	if (!btt)
  		return NULL;
  
  	btt->nd_btt = nd_btt;
  	btt->rawsize = rawsize;
  	btt->lbasize = lbasize;
  	btt->sector_size = ((lbasize >= 4096) ? 4096 : 512);
  	INIT_LIST_HEAD(&btt->arena_list);
  	mutex_init(&btt->init_lock);
  	btt->nd_region = nd_region;
  
  	ret = discover_arenas(btt);
  	if (ret) {
  		dev_err(dev, "init: error in arena_discover: %d
  ", ret);
  		goto out_free;
  	}
  
  	if (btt->init_state != INIT_READY && nd_region->ro) {
  		dev_info(dev, "%s is read-only, unable to init btt metadata
  ",
  				dev_name(&nd_region->dev));
  		goto out_free;
  	} else if (btt->init_state != INIT_READY) {
  		btt->num_arenas = (rawsize / ARENA_MAX_SIZE) +
  			((rawsize % ARENA_MAX_SIZE) ? 1 : 0);
  		dev_dbg(dev, "init: %d arenas for %llu rawsize
  ",
  				btt->num_arenas, rawsize);
  
  		ret = create_arenas(btt);
  		if (ret) {
  			dev_info(dev, "init: create_arenas: %d
  ", ret);
  			goto out_free;
  		}
  
  		ret = btt_meta_init(btt);
  		if (ret) {
  			dev_err(dev, "init: error in meta_init: %d
  ", ret);
  			goto out_free;
  		}
  	}
  
  	ret = btt_blk_init(btt);
  	if (ret) {
  		dev_err(dev, "init: error in blk_init: %d
  ", ret);
  		goto out_free;
  	}
  
  	btt_debugfs_init(btt);
  
  	return btt;
  
   out_free:
  	kfree(btt);
  	return NULL;
  }
  
  /**
   * btt_fini - de-initialize a BTT
   * @btt:	the BTT handle that was generated by btt_init
   *
   * De-initialize a Block Translation Table on device removal
   *
   * Context:
   * Might sleep.
   */
  static void btt_fini(struct btt *btt)
  {
  	if (btt) {
  		btt_blk_cleanup(btt);
  		free_arenas(btt);
  		debugfs_remove_recursive(btt->debugfs_dir);
  		kfree(btt);
  	}
  }
  
  int nvdimm_namespace_attach_btt(struct nd_namespace_common *ndns)
  {
  	struct nd_btt *nd_btt = to_nd_btt(ndns->claim);
  	struct nd_region *nd_region;
  	struct btt *btt;
  	size_t rawsize;
  
  	if (!nd_btt->uuid || !nd_btt->ndns || !nd_btt->lbasize)
  		return -ENODEV;
  
  	rawsize = nvdimm_namespace_capacity(ndns) - SZ_4K;
  	if (rawsize < ARENA_MIN_SIZE) {
  		return -ENXIO;
  	}
  	nd_region = to_nd_region(nd_btt->dev.parent);
  	btt = btt_init(nd_btt, rawsize, nd_btt->lbasize, nd_btt->uuid,
  			nd_region);
  	if (!btt)
  		return -ENOMEM;
  	nd_btt->btt = btt;
  
  	return 0;
  }
  EXPORT_SYMBOL(nvdimm_namespace_attach_btt);
  
  int nvdimm_namespace_detach_btt(struct nd_namespace_common *ndns)
  {
  	struct nd_btt *nd_btt = to_nd_btt(ndns->claim);
  	struct btt *btt = nd_btt->btt;
  
  	btt_fini(btt);
  	nd_btt->btt = NULL;
  
  	return 0;
  }
  EXPORT_SYMBOL(nvdimm_namespace_detach_btt);
  
  static int __init nd_btt_init(void)
  {
  	int rc;
  
  	btt_major = register_blkdev(0, "btt");
  	if (btt_major < 0)
  		return btt_major;
  
  	debugfs_root = debugfs_create_dir("btt", NULL);
  	if (IS_ERR_OR_NULL(debugfs_root)) {
  		rc = -ENXIO;
  		goto err_debugfs;
  	}
  
  	return 0;
  
   err_debugfs:
  	unregister_blkdev(btt_major, "btt");
  
  	return rc;
  }
  
  static void __exit nd_btt_exit(void)
  {
  	debugfs_remove_recursive(debugfs_root);
  	unregister_blkdev(btt_major, "btt");
  }
  
  MODULE_ALIAS_ND_DEVICE(ND_DEVICE_BTT);
  MODULE_AUTHOR("Vishal Verma <vishal.l.verma@linux.intel.com>");
  MODULE_LICENSE("GPL v2");
  module_init(nd_btt_init);
  module_exit(nd_btt_exit);