/*
   * recovery.c - NILFS recovery logic
   *
   * Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.
   *
   * 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., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
   *
   * Written by Ryusuke Konishi <ryusuke@osrg.net>
   */
  
  #include <linux/buffer_head.h>
  #include <linux/blkdev.h>
  #include <linux/swap.h>

  #include <linux/slab.h>

  #include <linux/crc32.h>
  #include "nilfs.h"
  #include "segment.h"
  #include "sufile.h"
  #include "page.h"

  #include "segbuf.h"
  
  /*
   * Segment check result
   */
  enum {
  	NILFS_SEG_VALID,
  	NILFS_SEG_NO_SUPER_ROOT,
  	NILFS_SEG_FAIL_IO,
  	NILFS_SEG_FAIL_MAGIC,
  	NILFS_SEG_FAIL_SEQ,

  	NILFS_SEG_FAIL_CHECKSUM_SUPER_ROOT,
  	NILFS_SEG_FAIL_CHECKSUM_FULL,
  	NILFS_SEG_FAIL_CONSISTENCY,
  };
  
  /* work structure for recovery */
  struct nilfs_recovery_block {
  	ino_t ino;		/* Inode number of the file that this block
  				   belongs to */
  	sector_t blocknr;	/* block number */
  	__u64 vblocknr;		/* virtual block number */
  	unsigned long blkoff;	/* File offset of the data block (per block) */
  	struct list_head list;
  };
  
  
  static int nilfs_warn_segment_error(int err)
  {
  	switch (err) {
  	case NILFS_SEG_FAIL_IO:
  		printk(KERN_WARNING
  		       "NILFS warning: I/O error on loading last segment
  ");
  		return -EIO;
  	case NILFS_SEG_FAIL_MAGIC:
  		printk(KERN_WARNING
  		       "NILFS warning: Segment magic number invalid
  ");
  		break;
  	case NILFS_SEG_FAIL_SEQ:
  		printk(KERN_WARNING
  		       "NILFS warning: Sequence number mismatch
  ");
  		break;

  	case NILFS_SEG_FAIL_CHECKSUM_SUPER_ROOT:
  		printk(KERN_WARNING
  		       "NILFS warning: Checksum error in super root
  ");
  		break;
  	case NILFS_SEG_FAIL_CHECKSUM_FULL:
  		printk(KERN_WARNING
  		       "NILFS warning: Checksum error in segment payload
  ");
  		break;
  	case NILFS_SEG_FAIL_CONSISTENCY:
  		printk(KERN_WARNING
  		       "NILFS warning: Inconsistent segment
  ");
  		break;
  	case NILFS_SEG_NO_SUPER_ROOT:
  		printk(KERN_WARNING
  		       "NILFS warning: No super root in the last segment
  ");
  		break;

  	}
  	return -EINVAL;
  }

  /**

   * nilfs_compute_checksum - compute checksum of blocks continuously
   * @nilfs: nilfs object

   * @bhs: buffer head of start block
   * @sum: place to store result
   * @offset: offset bytes in the first block
   * @check_bytes: number of bytes to be checked
   * @start: DBN of start block
   * @nblock: number of blocks to be checked
   */

  static int nilfs_compute_checksum(struct the_nilfs *nilfs,
  				  struct buffer_head *bhs, u32 *sum,
  				  unsigned long offset, u64 check_bytes,
  				  sector_t start, unsigned long nblock)

  {

  	unsigned int blocksize = nilfs->ns_blocksize;

  	unsigned long size;
  	u32 crc;
  
  	BUG_ON(offset >= blocksize);
  	check_bytes -= offset;
  	size = min_t(u64, check_bytes, blocksize - offset);

  	crc = crc32_le(nilfs->ns_crc_seed,

  		       (unsigned char *)bhs->b_data + offset, size);
  	if (--nblock > 0) {
  		do {

  			struct buffer_head *bh;
  
  			bh = __bread(nilfs->ns_bdev, ++start, blocksize);

  			if (!bh)
  				return -EIO;
  			check_bytes -= size;
  			size = min_t(u64, check_bytes, blocksize);
  			crc = crc32_le(crc, bh->b_data, size);
  			brelse(bh);
  		} while (--nblock > 0);
  	}
  	*sum = crc;
  	return 0;
  }
  
  /**
   * nilfs_read_super_root_block - read super root block

   * @nilfs: nilfs object

   * @sr_block: disk block number of the super root block
   * @pbh: address of a buffer_head pointer to return super root buffer
   * @check: CRC check flag
   */

  int nilfs_read_super_root_block(struct the_nilfs *nilfs, sector_t sr_block,

  				struct buffer_head **pbh, int check)
  {
  	struct buffer_head *bh_sr;
  	struct nilfs_super_root *sr;
  	u32 crc;
  	int ret;
  
  	*pbh = NULL;

  	bh_sr = __bread(nilfs->ns_bdev, sr_block, nilfs->ns_blocksize);

  	if (unlikely(!bh_sr)) {
  		ret = NILFS_SEG_FAIL_IO;
  		goto failed;
  	}
  
  	sr = (struct nilfs_super_root *)bh_sr->b_data;
  	if (check) {
  		unsigned bytes = le16_to_cpu(sr->sr_bytes);

  		if (bytes == 0 || bytes > nilfs->ns_blocksize) {

  			ret = NILFS_SEG_FAIL_CHECKSUM_SUPER_ROOT;
  			goto failed_bh;
  		}

  		if (nilfs_compute_checksum(
  			    nilfs, bh_sr, &crc, sizeof(sr->sr_sum), bytes,
  			    sr_block, 1)) {

  			ret = NILFS_SEG_FAIL_IO;
  			goto failed_bh;
  		}
  		if (crc != le32_to_cpu(sr->sr_sum)) {
  			ret = NILFS_SEG_FAIL_CHECKSUM_SUPER_ROOT;
  			goto failed_bh;
  		}
  	}
  	*pbh = bh_sr;
  	return 0;
  
   failed_bh:
  	brelse(bh_sr);
  
   failed:
  	return nilfs_warn_segment_error(ret);
  }
  
  /**

   * nilfs_read_log_header - read summary header of the specified log

   * @nilfs: nilfs object

   * @start_blocknr: start block number of the log
   * @sum: pointer to return segment summary structure

   */

  static struct buffer_head *
  nilfs_read_log_header(struct the_nilfs *nilfs, sector_t start_blocknr,
  		      struct nilfs_segment_summary **sum)

  {
  	struct buffer_head *bh_sum;

  
  	bh_sum = __bread(nilfs->ns_bdev, start_blocknr, nilfs->ns_blocksize);
  	if (bh_sum)
  		*sum = (struct nilfs_segment_summary *)bh_sum->b_data;
  	return bh_sum;
  }
  
  /**
   * nilfs_validate_log - verify consistency of log
   * @nilfs: nilfs object
   * @seg_seq: sequence number of segment
   * @bh_sum: buffer head of summary block
   * @sum: segment summary struct
   */
  static int nilfs_validate_log(struct the_nilfs *nilfs, u64 seg_seq,
  			      struct buffer_head *bh_sum,
  			      struct nilfs_segment_summary *sum)
  {

  	unsigned long nblock;
  	u32 crc;

  	int ret;

  	ret = NILFS_SEG_FAIL_MAGIC;
  	if (le32_to_cpu(sum->ss_magic) != NILFS_SEGSUM_MAGIC)

  		goto out;

  	ret = NILFS_SEG_FAIL_SEQ;
  	if (le64_to_cpu(sum->ss_seq) != seg_seq)
  		goto out;

  	nblock = le32_to_cpu(sum->ss_nblocks);
  	ret = NILFS_SEG_FAIL_CONSISTENCY;
  	if (unlikely(nblock == 0 || nblock > nilfs->ns_blocks_per_segment))

  		/* This limits the number of blocks read in the CRC check */

  		goto out;
  
  	ret = NILFS_SEG_FAIL_IO;

  	if (nilfs_compute_checksum(nilfs, bh_sum, &crc, sizeof(sum->ss_datasum),
  				   ((u64)nblock << nilfs->ns_blocksize_bits),

  				   bh_sum->b_blocknr, nblock))
  		goto out;
  
  	ret = NILFS_SEG_FAIL_CHECKSUM_FULL;
  	if (crc != le32_to_cpu(sum->ss_datasum))
  		goto out;
  	ret = 0;
  out:

  	return ret;
  }

  /**
   * nilfs_read_summary_info - read an item on summary blocks of a log
   * @nilfs: nilfs object
   * @pbh: the current buffer head on summary blocks [in, out]
   * @offset: the current byte offset on summary blocks [in, out]
   * @bytes: byte size of the item to be read
   */
  static void *nilfs_read_summary_info(struct the_nilfs *nilfs,
  				     struct buffer_head **pbh,
  				     unsigned int *offset, unsigned int bytes)

  {
  	void *ptr;
  	sector_t blocknr;
  
  	BUG_ON((*pbh)->b_size < *offset);
  	if (bytes > (*pbh)->b_size - *offset) {
  		blocknr = (*pbh)->b_blocknr;
  		brelse(*pbh);

  		*pbh = __bread(nilfs->ns_bdev, blocknr + 1,
  			       nilfs->ns_blocksize);

  		if (unlikely(!*pbh))
  			return NULL;
  		*offset = 0;
  	}
  	ptr = (*pbh)->b_data + *offset;
  	*offset += bytes;
  	return ptr;
  }

  /**
   * nilfs_skip_summary_info - skip items on summary blocks of a log
   * @nilfs: nilfs object
   * @pbh: the current buffer head on summary blocks [in, out]
   * @offset: the current byte offset on summary blocks [in, out]
   * @bytes: byte size of the item to be skipped
   * @count: number of items to be skipped
   */
  static void nilfs_skip_summary_info(struct the_nilfs *nilfs,
  				    struct buffer_head **pbh,
  				    unsigned int *offset, unsigned int bytes,
  				    unsigned long count)

  {
  	unsigned int rest_item_in_current_block
  		= ((*pbh)->b_size - *offset) / bytes;
  
  	if (count <= rest_item_in_current_block) {
  		*offset += bytes * count;
  	} else {
  		sector_t blocknr = (*pbh)->b_blocknr;
  		unsigned int nitem_per_block = (*pbh)->b_size / bytes;
  		unsigned int bcnt;
  
  		count -= rest_item_in_current_block;
  		bcnt = DIV_ROUND_UP(count, nitem_per_block);
  		*offset = bytes * (count - (bcnt - 1) * nitem_per_block);
  
  		brelse(*pbh);

  		*pbh = __bread(nilfs->ns_bdev, blocknr + bcnt,
  			       nilfs->ns_blocksize);

  	}
  }

  /**
   * nilfs_scan_dsync_log - get block information of a log written for data sync
   * @nilfs: nilfs object
   * @start_blocknr: start block number of the log

   * @sum: log summary information

   * @head: list head to add nilfs_recovery_block struct
   */
  static int nilfs_scan_dsync_log(struct the_nilfs *nilfs, sector_t start_blocknr,

  				struct nilfs_segment_summary *sum,

  				struct list_head *head)

  {
  	struct buffer_head *bh;
  	unsigned int offset;

  	u32 nfinfo, sumbytes;
  	sector_t blocknr;

  	ino_t ino;
  	int err = -EIO;

  	nfinfo = le32_to_cpu(sum->ss_nfinfo);

  	if (!nfinfo)
  		return 0;

  	sumbytes = le32_to_cpu(sum->ss_sumbytes);
  	blocknr = start_blocknr + DIV_ROUND_UP(sumbytes, nilfs->ns_blocksize);

  	bh = __bread(nilfs->ns_bdev, start_blocknr, nilfs->ns_blocksize);

  	if (unlikely(!bh))
  		goto out;

  	offset = le16_to_cpu(sum->ss_bytes);

  	for (;;) {
  		unsigned long nblocks, ndatablk, nnodeblk;
  		struct nilfs_finfo *finfo;

  		finfo = nilfs_read_summary_info(nilfs, &bh, &offset,
  						sizeof(*finfo));

  		if (unlikely(!finfo))
  			goto out;
  
  		ino = le64_to_cpu(finfo->fi_ino);
  		nblocks = le32_to_cpu(finfo->fi_nblocks);
  		ndatablk = le32_to_cpu(finfo->fi_ndatablk);
  		nnodeblk = nblocks - ndatablk;
  
  		while (ndatablk-- > 0) {
  			struct nilfs_recovery_block *rb;
  			struct nilfs_binfo_v *binfo;

  			binfo = nilfs_read_summary_info(nilfs, &bh, &offset,
  							sizeof(*binfo));

  			if (unlikely(!binfo))
  				goto out;
  
  			rb = kmalloc(sizeof(*rb), GFP_NOFS);
  			if (unlikely(!rb)) {
  				err = -ENOMEM;
  				goto out;
  			}
  			rb->ino = ino;
  			rb->blocknr = blocknr++;
  			rb->vblocknr = le64_to_cpu(binfo->bi_vblocknr);
  			rb->blkoff = le64_to_cpu(binfo->bi_blkoff);
  			/* INIT_LIST_HEAD(&rb->list); */
  			list_add_tail(&rb->list, head);
  		}
  		if (--nfinfo == 0)
  			break;

  		blocknr += nnodeblk; /* always 0 for data sync logs */
  		nilfs_skip_summary_info(nilfs, &bh, &offset, sizeof(__le64),
  					nnodeblk);

  		if (unlikely(!bh))
  			goto out;
  	}
  	err = 0;
   out:
  	brelse(bh);   /* brelse(NULL) is just ignored */
  	return err;
  }
  
  static void dispose_recovery_list(struct list_head *head)
  {
  	while (!list_empty(head)) {

  		struct nilfs_recovery_block *rb;
  
  		rb = list_first_entry(head, struct nilfs_recovery_block, list);

  		list_del(&rb->list);
  		kfree(rb);
  	}
  }

  struct nilfs_segment_entry {
  	struct list_head	list;
  	__u64			segnum;
  };
  
  static int nilfs_segment_list_add(struct list_head *head, __u64 segnum)
  {
  	struct nilfs_segment_entry *ent = kmalloc(sizeof(*ent), GFP_NOFS);
  
  	if (unlikely(!ent))
  		return -ENOMEM;
  
  	ent->segnum = segnum;
  	INIT_LIST_HEAD(&ent->list);
  	list_add_tail(&ent->list, head);
  	return 0;
  }

  void nilfs_dispose_segment_list(struct list_head *head)
  {
  	while (!list_empty(head)) {

  		struct nilfs_segment_entry *ent;
  
  		ent = list_first_entry(head, struct nilfs_segment_entry, list);

  		list_del(&ent->list);

  		kfree(ent);

  	}
  }
  
  static int nilfs_prepare_segment_for_recovery(struct the_nilfs *nilfs,

  					      struct super_block *sb,

  					      struct nilfs_recovery_info *ri)
  {
  	struct list_head *head = &ri->ri_used_segments;
  	struct nilfs_segment_entry *ent, *n;
  	struct inode *sufile = nilfs->ns_sufile;
  	__u64 segnum[4];
  	int err;
  	int i;
  
  	segnum[0] = nilfs->ns_segnum;
  	segnum[1] = nilfs->ns_nextnum;
  	segnum[2] = ri->ri_segnum;
  	segnum[3] = ri->ri_nextnum;
  
  	/*
  	 * Releasing the next segment of the latest super root.
  	 * The next segment is invalidated by this recovery.
  	 */
  	err = nilfs_sufile_free(sufile, segnum[1]);
  	if (unlikely(err))
  		goto failed;

  	for (i = 1; i < 4; i++) {

  		err = nilfs_segment_list_add(head, segnum[i]);
  		if (unlikely(err))

  			goto failed;

  	}
  
  	/*
  	 * Collecting segments written after the latest super root.

  	 * These are marked dirty to avoid being reallocated in the next write.

  	 */
  	list_for_each_entry_safe(ent, n, head, list) {

  		if (ent->segnum != segnum[0]) {
  			err = nilfs_sufile_scrap(sufile, ent->segnum);
  			if (unlikely(err))
  				goto failed;

  		}

  		list_del(&ent->list);

  		kfree(ent);

  	}

  	/* Allocate new segments for recovery */
  	err = nilfs_sufile_alloc(sufile, &segnum[0]);
  	if (unlikely(err))
  		goto failed;
  
  	nilfs->ns_pseg_offset = 0;
  	nilfs->ns_seg_seq = ri->ri_seq + 2;
  	nilfs->ns_nextnum = nilfs->ns_segnum = segnum[0];

  
   failed:
  	/* No need to recover sufile because it will be destroyed on error */
  	return err;
  }

  static int nilfs_recovery_copy_block(struct the_nilfs *nilfs,

  				     struct nilfs_recovery_block *rb,
  				     struct page *page)
  {
  	struct buffer_head *bh_org;
  	void *kaddr;

  	bh_org = __bread(nilfs->ns_bdev, rb->blocknr, nilfs->ns_blocksize);

  	if (unlikely(!bh_org))
  		return -EIO;
  
  	kaddr = kmap_atomic(page, KM_USER0);
  	memcpy(kaddr + bh_offset(bh_org), bh_org->b_data, bh_org->b_size);
  	kunmap_atomic(kaddr, KM_USER0);
  	brelse(bh_org);
  	return 0;
  }

  static int nilfs_recover_dsync_blocks(struct the_nilfs *nilfs,

  				      struct super_block *sb,

  				      struct nilfs_root *root,

  				      struct list_head *head,
  				      unsigned long *nr_salvaged_blocks)

  {
  	struct inode *inode;
  	struct nilfs_recovery_block *rb, *n;

  	unsigned blocksize = nilfs->ns_blocksize;

  	struct page *page;
  	loff_t pos;
  	int err = 0, err2 = 0;
  
  	list_for_each_entry_safe(rb, n, head, list) {

  		inode = nilfs_iget(sb, root, rb->ino);

  		if (IS_ERR(inode)) {
  			err = PTR_ERR(inode);
  			inode = NULL;
  			goto failed_inode;
  		}
  
  		pos = rb->blkoff << inode->i_blkbits;

  		err = block_write_begin(inode->i_mapping, pos, blocksize,
  					0, &page, nilfs_get_block);
  		if (unlikely(err)) {
  			loff_t isize = inode->i_size;
  			if (pos + blocksize > isize)
  				vmtruncate(inode, isize);

  			goto failed_inode;

  		}

  		err = nilfs_recovery_copy_block(nilfs, rb, page);

  		if (unlikely(err))
  			goto failed_page;

  		err = nilfs_set_file_dirty(inode, 1);

  		if (unlikely(err))
  			goto failed_page;
  
  		block_write_end(NULL, inode->i_mapping, pos, blocksize,
  				blocksize, page, NULL);
  
  		unlock_page(page);
  		page_cache_release(page);
  
  		(*nr_salvaged_blocks)++;
  		goto next;
  
   failed_page:
  		unlock_page(page);
  		page_cache_release(page);
  
   failed_inode:
  		printk(KERN_WARNING
  		       "NILFS warning: error recovering data block "
  		       "(err=%d, ino=%lu, block-offset=%llu)
  ",

  		       err, (unsigned long)rb->ino,
  		       (unsigned long long)rb->blkoff);

  		if (!err2)
  			err2 = err;
   next:
  		iput(inode); /* iput(NULL) is just ignored */
  		list_del_init(&rb->list);
  		kfree(rb);
  	}
  	return err2;
  }
  
  /**
   * nilfs_do_roll_forward - salvage logical segments newer than the latest
   * checkpoint

   * @nilfs: nilfs object

   * @sb: super block instance

   * @ri: pointer to a nilfs_recovery_info
   */
  static int nilfs_do_roll_forward(struct the_nilfs *nilfs,

  				 struct super_block *sb,

  				 struct nilfs_root *root,

  				 struct nilfs_recovery_info *ri)
  {

  	struct buffer_head *bh_sum = NULL;
  	struct nilfs_segment_summary *sum;

  	sector_t pseg_start;
  	sector_t seg_start, seg_end;  /* Starting/ending DBN of full segment */
  	unsigned long nsalvaged_blocks = 0;

  	unsigned int flags;

  	u64 seg_seq;
  	__u64 segnum, nextnum = 0;
  	int empty_seg = 0;
  	int err = 0, ret;
  	LIST_HEAD(dsync_blocks);  /* list of data blocks to be recovered */
  	enum {
  		RF_INIT_ST,
  		RF_DSYNC_ST,   /* scanning data-sync segments */
  	};
  	int state = RF_INIT_ST;

  	pseg_start = ri->ri_lsegs_start;
  	seg_seq = ri->ri_lsegs_start_seq;
  	segnum = nilfs_get_segnum_of_block(nilfs, pseg_start);
  	nilfs_get_segment_range(nilfs, segnum, &seg_start, &seg_end);
  
  	while (segnum != ri->ri_segnum || pseg_start <= ri->ri_pseg_start) {

  		brelse(bh_sum);
  		bh_sum = nilfs_read_log_header(nilfs, pseg_start, &sum);
  		if (!bh_sum) {
  			err = -EIO;
  			goto failed;
  		}

  		ret = nilfs_validate_log(nilfs, seg_seq, bh_sum, sum);

  		if (ret) {
  			if (ret == NILFS_SEG_FAIL_IO) {
  				err = -EIO;
  				goto failed;
  			}
  			goto strayed;
  		}

  		flags = le16_to_cpu(sum->ss_flags);
  		if (flags & NILFS_SS_SR)

  			goto confused;
  
  		/* Found a valid partial segment; do recovery actions */

  		nextnum = nilfs_get_segnum_of_block(nilfs,
  						    le64_to_cpu(sum->ss_next));

  		empty_seg = 0;

  		nilfs->ns_ctime = le64_to_cpu(sum->ss_create);
  		if (!(flags & NILFS_SS_GC))
  			nilfs->ns_nongc_ctime = nilfs->ns_ctime;

  
  		switch (state) {
  		case RF_INIT_ST:

  			if (!(flags & NILFS_SS_LOGBGN) ||
  			    !(flags & NILFS_SS_SYNDT))

  				goto try_next_pseg;
  			state = RF_DSYNC_ST;
  			/* Fall through */
  		case RF_DSYNC_ST:

  			if (!(flags & NILFS_SS_SYNDT))

  				goto confused;

  			err = nilfs_scan_dsync_log(nilfs, pseg_start, sum,

  						   &dsync_blocks);

  			if (unlikely(err))
  				goto failed;

  			if (flags & NILFS_SS_LOGEND) {

  				err = nilfs_recover_dsync_blocks(

  					nilfs, sb, root, &dsync_blocks,

  					&nsalvaged_blocks);

  				if (unlikely(err))
  					goto failed;
  				state = RF_INIT_ST;
  			}
  			break; /* Fall through to try_next_pseg */
  		}
  
   try_next_pseg:
  		if (pseg_start == ri->ri_lsegs_end)
  			break;

  		pseg_start += le32_to_cpu(sum->ss_nblocks);

  		if (pseg_start < seg_end)
  			continue;
  		goto feed_segment;
  
   strayed:
  		if (pseg_start == ri->ri_lsegs_end)
  			break;
  
   feed_segment:
  		/* Looking to the next full segment */
  		if (empty_seg++)
  			break;
  		seg_seq++;
  		segnum = nextnum;
  		nilfs_get_segment_range(nilfs, segnum, &seg_start, &seg_end);
  		pseg_start = seg_start;
  	}
  
  	if (nsalvaged_blocks) {
  		printk(KERN_INFO "NILFS (device %s): salvaged %lu blocks
  ",

  		       sb->s_id, nsalvaged_blocks);

  		ri->ri_need_recovery = NILFS_RECOVERY_ROLLFORWARD_DONE;
  	}
   out:

  	brelse(bh_sum);

  	dispose_recovery_list(&dsync_blocks);

  	return err;
  
   confused:
  	err = -EINVAL;
   failed:
  	printk(KERN_ERR
  	       "NILFS (device %s): Error roll-forwarding "
  	       "(err=%d, pseg block=%llu). ",

  	       sb->s_id, err, (unsigned long long)pseg_start);

  	goto out;
  }
  
  static void nilfs_finish_roll_forward(struct the_nilfs *nilfs,

  				      struct nilfs_recovery_info *ri)
  {
  	struct buffer_head *bh;
  	int err;
  
  	if (nilfs_get_segnum_of_block(nilfs, ri->ri_lsegs_start) !=
  	    nilfs_get_segnum_of_block(nilfs, ri->ri_super_root))
  		return;

  	bh = __getblk(nilfs->ns_bdev, ri->ri_lsegs_start, nilfs->ns_blocksize);

  	BUG_ON(!bh);
  	memset(bh->b_data, 0, bh->b_size);
  	set_buffer_dirty(bh);
  	err = sync_dirty_buffer(bh);
  	if (unlikely(err))
  		printk(KERN_WARNING
  		       "NILFS warning: buffer sync write failed during "
  		       "post-cleaning of recovery.
  ");
  	brelse(bh);
  }
  
  /**

   * nilfs_salvage_orphan_logs - salvage logs written after the latest checkpoint
   * @nilfs: nilfs object

   * @sb: super block instance

   * @ri: pointer to a nilfs_recovery_info struct to store search results.
   *
   * Return Value: On success, 0 is returned.  On error, one of the following
   * negative error code is returned.
   *
   * %-EINVAL - Inconsistent filesystem state.
   *
   * %-EIO - I/O error
   *
   * %-ENOSPC - No space left on device (only in a panic state).
   *
   * %-ERESTARTSYS - Interrupted.
   *
   * %-ENOMEM - Insufficient memory available.
   */

  int nilfs_salvage_orphan_logs(struct the_nilfs *nilfs,

  			      struct super_block *sb,

  			      struct nilfs_recovery_info *ri)

  {

  	struct nilfs_root *root;

  	int err;
  
  	if (ri->ri_lsegs_start == 0 || ri->ri_lsegs_end == 0)
  		return 0;

  	err = nilfs_attach_checkpoint(sb, ri->ri_cno, true, &root);

  	if (unlikely(err)) {
  		printk(KERN_ERR
  		       "NILFS: error loading the latest checkpoint.
  ");
  		return err;
  	}

  	err = nilfs_do_roll_forward(nilfs, sb, root, ri);

  	if (unlikely(err))
  		goto failed;
  
  	if (ri->ri_need_recovery == NILFS_RECOVERY_ROLLFORWARD_DONE) {

  		err = nilfs_prepare_segment_for_recovery(nilfs, sb, ri);

  		if (unlikely(err)) {
  			printk(KERN_ERR "NILFS: Error preparing segments for "
  			       "recovery.
  ");
  			goto failed;
  		}

  		err = nilfs_attach_log_writer(sb, root);

  		if (unlikely(err))
  			goto failed;
  
  		set_nilfs_discontinued(nilfs);

  		err = nilfs_construct_segment(sb);
  		nilfs_detach_log_writer(sb);

  
  		if (unlikely(err)) {
  			printk(KERN_ERR "NILFS: Oops! recovery failed. "
  			       "(err=%d)
  ", err);
  			goto failed;
  		}

  		nilfs_finish_roll_forward(nilfs, ri);

  	}

   failed:

  	nilfs_put_root(root);

  	return err;
  }
  
  /**
   * nilfs_search_super_root - search the latest valid super root
   * @nilfs: the_nilfs

   * @ri: pointer to a nilfs_recovery_info struct to store search results.
   *
   * nilfs_search_super_root() looks for the latest super-root from a partial
   * segment pointed by the superblock.  It sets up struct the_nilfs through
   * this search. It fills nilfs_recovery_info (ri) required for recovery.
   *
   * Return Value: On success, 0 is returned.  On error, one of the following
   * negative error code is returned.
   *
   * %-EINVAL - No valid segment found
   *
   * %-EIO - I/O error

   *
   * %-ENOMEM - Insufficient memory available.

   */

  int nilfs_search_super_root(struct the_nilfs *nilfs,

  			    struct nilfs_recovery_info *ri)
  {

  	struct buffer_head *bh_sum = NULL;
  	struct nilfs_segment_summary *sum;

  	sector_t pseg_start, pseg_end, sr_pseg_start = 0;
  	sector_t seg_start, seg_end; /* range of full segment (block number) */

  	sector_t b, end;

  	unsigned long nblocks;
  	unsigned int flags;

  	u64 seg_seq;
  	__u64 segnum, nextnum = 0;
  	__u64 cno;

  	LIST_HEAD(segments);
  	int empty_seg = 0, scan_newer = 0;
  	int ret;
  
  	pseg_start = nilfs->ns_last_pseg;
  	seg_seq = nilfs->ns_last_seq;
  	cno = nilfs->ns_last_cno;
  	segnum = nilfs_get_segnum_of_block(nilfs, pseg_start);
  
  	/* Calculate range of segment */
  	nilfs_get_segment_range(nilfs, segnum, &seg_start, &seg_end);

  	/* Read ahead segment */
  	b = seg_start;
  	while (b <= seg_end)

  		__breadahead(nilfs->ns_bdev, b++, nilfs->ns_blocksize);

  	for (;;) {

  		brelse(bh_sum);
  		ret = NILFS_SEG_FAIL_IO;
  		bh_sum = nilfs_read_log_header(nilfs, pseg_start, &sum);
  		if (!bh_sum)
  			goto failed;
  
  		ret = nilfs_validate_log(nilfs, seg_seq, bh_sum, sum);

  		if (ret) {
  			if (ret == NILFS_SEG_FAIL_IO)
  				goto failed;
  			goto strayed;
  		}

  		nblocks = le32_to_cpu(sum->ss_nblocks);
  		pseg_end = pseg_start + nblocks - 1;

  		if (unlikely(pseg_end > seg_end)) {
  			ret = NILFS_SEG_FAIL_CONSISTENCY;
  			goto strayed;
  		}
  
  		/* A valid partial segment */
  		ri->ri_pseg_start = pseg_start;
  		ri->ri_seq = seg_seq;
  		ri->ri_segnum = segnum;

  		nextnum = nilfs_get_segnum_of_block(nilfs,
  						    le64_to_cpu(sum->ss_next));

  		ri->ri_nextnum = nextnum;
  		empty_seg = 0;

  		flags = le16_to_cpu(sum->ss_flags);
  		if (!(flags & NILFS_SS_SR) && !scan_newer) {

  			/* This will never happen because a superblock
  			   (last_segment) always points to a pseg
  			   having a super root. */
  			ret = NILFS_SEG_FAIL_CONSISTENCY;
  			goto failed;
  		}
  
  		if (pseg_start == seg_start) {
  			nilfs_get_segment_range(nilfs, nextnum, &b, &end);
  			while (b <= end)

  				__breadahead(nilfs->ns_bdev, b++,
  					     nilfs->ns_blocksize);

  		}

  		if (!(flags & NILFS_SS_SR)) {
  			if (!ri->ri_lsegs_start && (flags & NILFS_SS_LOGBGN)) {

  				ri->ri_lsegs_start = pseg_start;
  				ri->ri_lsegs_start_seq = seg_seq;
  			}

  			if (flags & NILFS_SS_LOGEND)

  				ri->ri_lsegs_end = pseg_start;
  			goto try_next_pseg;
  		}
  
  		/* A valid super root was found. */
  		ri->ri_cno = cno++;
  		ri->ri_super_root = pseg_end;
  		ri->ri_lsegs_start = ri->ri_lsegs_end = 0;
  
  		nilfs_dispose_segment_list(&segments);

  		sr_pseg_start = pseg_start;
  		nilfs->ns_pseg_offset = pseg_start + nblocks - seg_start;

  		nilfs->ns_seg_seq = seg_seq;
  		nilfs->ns_segnum = segnum;
  		nilfs->ns_cno = cno;  /* nilfs->ns_cno = ri->ri_cno + 1 */

  		nilfs->ns_ctime = le64_to_cpu(sum->ss_create);

  		nilfs->ns_nextnum = nextnum;
  
  		if (scan_newer)
  			ri->ri_need_recovery = NILFS_RECOVERY_SR_UPDATED;

  		else {

  			if (nilfs->ns_mount_state & NILFS_VALID_FS)
  				goto super_root_found;
  			scan_newer = 1;
  		}

   try_next_pseg:
  		/* Standing on a course, or met an inconsistent state */

  		pseg_start += nblocks;

  		if (pseg_start < seg_end)
  			continue;
  		goto feed_segment;
  
   strayed:
  		/* Off the trail */
  		if (!scan_newer)
  			/*
  			 * This can happen if a checkpoint was written without
  			 * barriers, or as a result of an I/O failure.
  			 */
  			goto failed;
  
   feed_segment:
  		/* Looking to the next full segment */
  		if (empty_seg++)
  			goto super_root_found; /* found a valid super root */

  		ret = nilfs_segment_list_add(&segments, segnum);
  		if (unlikely(ret))

  			goto failed;

  
  		seg_seq++;
  		segnum = nextnum;
  		nilfs_get_segment_range(nilfs, segnum, &seg_start, &seg_end);
  		pseg_start = seg_start;
  	}
  
   super_root_found:
  	/* Updating pointers relating to the latest checkpoint */

  	brelse(bh_sum);

  	list_splice_tail(&segments, &ri->ri_used_segments);

  	nilfs->ns_last_pseg = sr_pseg_start;
  	nilfs->ns_last_seq = nilfs->ns_seg_seq;
  	nilfs->ns_last_cno = ri->ri_cno;
  	return 0;
  
   failed:

  	brelse(bh_sum);

  	nilfs_dispose_segment_list(&segments);
  	return (ret < 0) ? ret : nilfs_warn_segment_error(ret);
  }