/*
   * segbuf.c - NILFS segment buffer
   *
   * 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/writeback.h>
  #include <linux/crc32.h>

  #include <linux/backing-dev.h>

  #include <linux/slab.h>

  #include "page.h"
  #include "segbuf.h"

  struct nilfs_write_info {
  	struct the_nilfs       *nilfs;
  	struct bio	       *bio;

  	int			start, end; /* The region to be submitted */

  	int			rest_blocks;
  	int			max_pages;
  	int			nr_vecs;
  	sector_t		blocknr;
  };

  static int nilfs_segbuf_write(struct nilfs_segment_buffer *segbuf,
  			      struct the_nilfs *nilfs);
  static int nilfs_segbuf_wait(struct nilfs_segment_buffer *segbuf);

  struct nilfs_segment_buffer *nilfs_segbuf_new(struct super_block *sb)
  {
  	struct nilfs_segment_buffer *segbuf;
  
  	segbuf = kmem_cache_alloc(nilfs_segbuf_cachep, GFP_NOFS);
  	if (unlikely(!segbuf))
  		return NULL;
  
  	segbuf->sb_super = sb;
  	INIT_LIST_HEAD(&segbuf->sb_list);
  	INIT_LIST_HEAD(&segbuf->sb_segsum_buffers);
  	INIT_LIST_HEAD(&segbuf->sb_payload_buffers);

  	segbuf->sb_super_root = NULL;

  
  	init_completion(&segbuf->sb_bio_event);
  	atomic_set(&segbuf->sb_err, 0);
  	segbuf->sb_nbio = 0;

  	return segbuf;
  }
  
  void nilfs_segbuf_free(struct nilfs_segment_buffer *segbuf)
  {

  	kmem_cache_free(nilfs_segbuf_cachep, segbuf);
  }

  void nilfs_segbuf_map(struct nilfs_segment_buffer *segbuf, __u64 segnum,

  		     unsigned long offset, struct the_nilfs *nilfs)
  {

  	segbuf->sb_segnum = segnum;
  	nilfs_get_segment_range(nilfs, segnum, &segbuf->sb_fseg_start,
  				&segbuf->sb_fseg_end);
  
  	segbuf->sb_pseg_start = segbuf->sb_fseg_start + offset;
  	segbuf->sb_rest_blocks =
  		segbuf->sb_fseg_end - segbuf->sb_pseg_start + 1;

  }

  /**
   * nilfs_segbuf_map_cont - map a new log behind a given log
   * @segbuf: new segment buffer
   * @prev: segment buffer containing a log to be continued
   */
  void nilfs_segbuf_map_cont(struct nilfs_segment_buffer *segbuf,
  			   struct nilfs_segment_buffer *prev)
  {
  	segbuf->sb_segnum = prev->sb_segnum;
  	segbuf->sb_fseg_start = prev->sb_fseg_start;
  	segbuf->sb_fseg_end = prev->sb_fseg_end;
  	segbuf->sb_pseg_start = prev->sb_pseg_start + prev->sb_sum.nblocks;
  	segbuf->sb_rest_blocks =
  		segbuf->sb_fseg_end - segbuf->sb_pseg_start + 1;
  }

  void nilfs_segbuf_set_next_segnum(struct nilfs_segment_buffer *segbuf,
  				  __u64 nextnum, struct the_nilfs *nilfs)
  {
  	segbuf->sb_nextnum = nextnum;
  	segbuf->sb_sum.next = nilfs_get_segment_start_blocknr(nilfs, nextnum);
  }
  
  int nilfs_segbuf_extend_segsum(struct nilfs_segment_buffer *segbuf)
  {
  	struct buffer_head *bh;
  
  	bh = sb_getblk(segbuf->sb_super,
  		       segbuf->sb_pseg_start + segbuf->sb_sum.nsumblk);
  	if (unlikely(!bh))
  		return -ENOMEM;
  
  	nilfs_segbuf_add_segsum_buffer(segbuf, bh);
  	return 0;
  }
  
  int nilfs_segbuf_extend_payload(struct nilfs_segment_buffer *segbuf,
  				struct buffer_head **bhp)
  {
  	struct buffer_head *bh;
  
  	bh = sb_getblk(segbuf->sb_super,
  		       segbuf->sb_pseg_start + segbuf->sb_sum.nblocks);
  	if (unlikely(!bh))
  		return -ENOMEM;
  
  	nilfs_segbuf_add_payload_buffer(segbuf, bh);
  	*bhp = bh;
  	return 0;
  }
  
  int nilfs_segbuf_reset(struct nilfs_segment_buffer *segbuf, unsigned flags,

  		       time_t ctime, __u64 cno)

  {
  	int err;
  
  	segbuf->sb_sum.nblocks = segbuf->sb_sum.nsumblk = 0;
  	err = nilfs_segbuf_extend_segsum(segbuf);
  	if (unlikely(err))
  		return err;
  
  	segbuf->sb_sum.flags = flags;
  	segbuf->sb_sum.sumbytes = sizeof(struct nilfs_segment_summary);
  	segbuf->sb_sum.nfinfo = segbuf->sb_sum.nfileblk = 0;
  	segbuf->sb_sum.ctime = ctime;

  	segbuf->sb_sum.cno = cno;

  	return 0;
  }
  
  /*

   * Setup segment summary

   */
  void nilfs_segbuf_fill_in_segsum(struct nilfs_segment_buffer *segbuf)
  {
  	struct nilfs_segment_summary *raw_sum;
  	struct buffer_head *bh_sum;
  
  	bh_sum = list_entry(segbuf->sb_segsum_buffers.next,
  			    struct buffer_head, b_assoc_buffers);
  	raw_sum = (struct nilfs_segment_summary *)bh_sum->b_data;
  
  	raw_sum->ss_magic    = cpu_to_le32(NILFS_SEGSUM_MAGIC);
  	raw_sum->ss_bytes    = cpu_to_le16(sizeof(*raw_sum));
  	raw_sum->ss_flags    = cpu_to_le16(segbuf->sb_sum.flags);
  	raw_sum->ss_seq      = cpu_to_le64(segbuf->sb_sum.seg_seq);
  	raw_sum->ss_create   = cpu_to_le64(segbuf->sb_sum.ctime);
  	raw_sum->ss_next     = cpu_to_le64(segbuf->sb_sum.next);
  	raw_sum->ss_nblocks  = cpu_to_le32(segbuf->sb_sum.nblocks);
  	raw_sum->ss_nfinfo   = cpu_to_le32(segbuf->sb_sum.nfinfo);
  	raw_sum->ss_sumbytes = cpu_to_le32(segbuf->sb_sum.sumbytes);
  	raw_sum->ss_pad      = 0;

  	raw_sum->ss_cno      = cpu_to_le64(segbuf->sb_sum.cno);

  }
  
  /*
   * CRC calculation routines
   */

  static void
  nilfs_segbuf_fill_in_segsum_crc(struct nilfs_segment_buffer *segbuf, u32 seed)

  {
  	struct buffer_head *bh;
  	struct nilfs_segment_summary *raw_sum;
  	unsigned long size, bytes = segbuf->sb_sum.sumbytes;
  	u32 crc;
  
  	bh = list_entry(segbuf->sb_segsum_buffers.next, struct buffer_head,
  			b_assoc_buffers);
  
  	raw_sum = (struct nilfs_segment_summary *)bh->b_data;
  	size = min_t(unsigned long, bytes, bh->b_size);
  	crc = crc32_le(seed,
  		       (unsigned char *)raw_sum +
  		       sizeof(raw_sum->ss_datasum) + sizeof(raw_sum->ss_sumsum),
  		       size - (sizeof(raw_sum->ss_datasum) +
  			       sizeof(raw_sum->ss_sumsum)));
  
  	list_for_each_entry_continue(bh, &segbuf->sb_segsum_buffers,
  				     b_assoc_buffers) {
  		bytes -= size;
  		size = min_t(unsigned long, bytes, bh->b_size);
  		crc = crc32_le(crc, bh->b_data, size);
  	}
  	raw_sum->ss_sumsum = cpu_to_le32(crc);
  }

  static void nilfs_segbuf_fill_in_data_crc(struct nilfs_segment_buffer *segbuf,
  					  u32 seed)

  {
  	struct buffer_head *bh;
  	struct nilfs_segment_summary *raw_sum;
  	void *kaddr;
  	u32 crc;
  
  	bh = list_entry(segbuf->sb_segsum_buffers.next, struct buffer_head,
  			b_assoc_buffers);
  	raw_sum = (struct nilfs_segment_summary *)bh->b_data;
  	crc = crc32_le(seed,
  		       (unsigned char *)raw_sum + sizeof(raw_sum->ss_datasum),
  		       bh->b_size - sizeof(raw_sum->ss_datasum));
  
  	list_for_each_entry_continue(bh, &segbuf->sb_segsum_buffers,
  				     b_assoc_buffers) {
  		crc = crc32_le(crc, bh->b_data, bh->b_size);
  	}
  	list_for_each_entry(bh, &segbuf->sb_payload_buffers, b_assoc_buffers) {
  		kaddr = kmap_atomic(bh->b_page, KM_USER0);
  		crc = crc32_le(crc, kaddr + bh_offset(bh), bh->b_size);
  		kunmap_atomic(kaddr, KM_USER0);
  	}
  	raw_sum->ss_datasum = cpu_to_le32(crc);
  }

  static void
  nilfs_segbuf_fill_in_super_root_crc(struct nilfs_segment_buffer *segbuf,
  				    u32 seed)
  {
  	struct nilfs_super_root *raw_sr;

  	struct the_nilfs *nilfs = segbuf->sb_super->s_fs_info;
  	unsigned srsize;

  	u32 crc;
  
  	raw_sr = (struct nilfs_super_root *)segbuf->sb_super_root->b_data;

  	srsize = NILFS_SR_BYTES(nilfs->ns_inode_size);

  	crc = crc32_le(seed,
  		       (unsigned char *)raw_sr + sizeof(raw_sr->sr_sum),

  		       srsize - sizeof(raw_sr->sr_sum));

  	raw_sr->sr_sum = cpu_to_le32(crc);
  }

  static void nilfs_release_buffers(struct list_head *list)

  {
  	struct buffer_head *bh, *n;
  
  	list_for_each_entry_safe(bh, n, list, b_assoc_buffers) {
  		list_del_init(&bh->b_assoc_buffers);

  		brelse(bh);
  	}
  }

  static void nilfs_segbuf_clear(struct nilfs_segment_buffer *segbuf)
  {
  	nilfs_release_buffers(&segbuf->sb_segsum_buffers);
  	nilfs_release_buffers(&segbuf->sb_payload_buffers);

  	segbuf->sb_super_root = NULL;

  }
  
  /*
   * Iterators for segment buffers
   */
  void nilfs_clear_logs(struct list_head *logs)
  {
  	struct nilfs_segment_buffer *segbuf;
  
  	list_for_each_entry(segbuf, logs, sb_list)
  		nilfs_segbuf_clear(segbuf);
  }
  
  void nilfs_truncate_logs(struct list_head *logs,
  			 struct nilfs_segment_buffer *last)
  {
  	struct nilfs_segment_buffer *n, *segbuf;
  
  	segbuf = list_prepare_entry(last, logs, sb_list);
  	list_for_each_entry_safe_continue(segbuf, n, logs, sb_list) {
  		list_del_init(&segbuf->sb_list);
  		nilfs_segbuf_clear(segbuf);
  		nilfs_segbuf_free(segbuf);
  	}
  }

  int nilfs_write_logs(struct list_head *logs, struct the_nilfs *nilfs)
  {
  	struct nilfs_segment_buffer *segbuf;
  	int ret = 0;
  
  	list_for_each_entry(segbuf, logs, sb_list) {
  		ret = nilfs_segbuf_write(segbuf, nilfs);
  		if (ret)
  			break;
  	}
  	return ret;
  }

  int nilfs_wait_on_logs(struct list_head *logs)
  {
  	struct nilfs_segment_buffer *segbuf;

  	int err, ret = 0;

  
  	list_for_each_entry(segbuf, logs, sb_list) {
  		err = nilfs_segbuf_wait(segbuf);

  		if (err && !ret)
  			ret = err;

  	}

  	return ret;

  }

  /**
   * nilfs_add_checksums_on_logs - add checksums on the logs
   * @logs: list of segment buffers storing target logs
   * @seed: checksum seed value
   */
  void nilfs_add_checksums_on_logs(struct list_head *logs, u32 seed)
  {
  	struct nilfs_segment_buffer *segbuf;
  
  	list_for_each_entry(segbuf, logs, sb_list) {
  		if (segbuf->sb_super_root)
  			nilfs_segbuf_fill_in_super_root_crc(segbuf, seed);
  		nilfs_segbuf_fill_in_segsum_crc(segbuf, seed);
  		nilfs_segbuf_fill_in_data_crc(segbuf, seed);
  	}
  }

  /*
   * BIO operations
   */
  static void nilfs_end_bio_write(struct bio *bio, int err)
  {
  	const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);

  	struct nilfs_segment_buffer *segbuf = bio->bi_private;

  
  	if (err == -EOPNOTSUPP) {
  		set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
  		bio_put(bio);
  		/* to be detected by submit_seg_bio() */
  	}
  
  	if (!uptodate)

  		atomic_inc(&segbuf->sb_err);

  
  	bio_put(bio);

  	complete(&segbuf->sb_bio_event);

  }

  static int nilfs_segbuf_submit_bio(struct nilfs_segment_buffer *segbuf,
  				   struct nilfs_write_info *wi, int mode)

  {
  	struct bio *bio = wi->bio;
  	int err;

  	if (segbuf->sb_nbio > 0 &&
  	    bdi_write_congested(segbuf->sb_super->s_bdi)) {

  		wait_for_completion(&segbuf->sb_bio_event);
  		segbuf->sb_nbio--;
  		if (unlikely(atomic_read(&segbuf->sb_err))) {

  			bio_put(bio);
  			err = -EIO;
  			goto failed;
  		}
  	}
  
  	bio->bi_end_io = nilfs_end_bio_write;

  	bio->bi_private = segbuf;

  	bio_get(bio);
  	submit_bio(mode, bio);
  	if (bio_flagged(bio, BIO_EOPNOTSUPP)) {
  		bio_put(bio);
  		err = -EOPNOTSUPP;
  		goto failed;
  	}

  	segbuf->sb_nbio++;

  	bio_put(bio);
  
  	wi->bio = NULL;
  	wi->rest_blocks -= wi->end - wi->start;
  	wi->nr_vecs = min(wi->max_pages, wi->rest_blocks);
  	wi->start = wi->end;
  	return 0;
  
   failed:
  	wi->bio = NULL;
  	return err;
  }
  
  /**

   * nilfs_alloc_seg_bio - allocate a new bio for writing log
   * @nilfs: nilfs object
   * @start: start block number of the bio

   * @nr_vecs: request size of page vector.
   *

   * Return Value: On success, pointer to the struct bio is returned.
   * On error, NULL is returned.
   */

  static struct bio *nilfs_alloc_seg_bio(struct the_nilfs *nilfs, sector_t start,

  				       int nr_vecs)
  {
  	struct bio *bio;

  	bio = bio_alloc(GFP_NOIO, nr_vecs);

  	if (bio == NULL) {
  		while (!bio && (nr_vecs >>= 1))

  			bio = bio_alloc(GFP_NOIO, nr_vecs);

  	}
  	if (likely(bio)) {

  		bio->bi_bdev = nilfs->ns_bdev;
  		bio->bi_sector = start << (nilfs->ns_blocksize_bits - 9);

  	}
  	return bio;
  }

  static void nilfs_segbuf_prepare_write(struct nilfs_segment_buffer *segbuf,
  				       struct nilfs_write_info *wi)

  {
  	wi->bio = NULL;
  	wi->rest_blocks = segbuf->sb_sum.nblocks;

  	wi->max_pages = bio_get_nr_vecs(wi->nilfs->ns_bdev);

  	wi->nr_vecs = min(wi->max_pages, wi->rest_blocks);
  	wi->start = wi->end = 0;

  	wi->blocknr = segbuf->sb_pseg_start;

  }

  static int nilfs_segbuf_submit_bh(struct nilfs_segment_buffer *segbuf,
  				  struct nilfs_write_info *wi,
  				  struct buffer_head *bh, int mode)

  {
  	int len, err;
  
  	BUG_ON(wi->nr_vecs <= 0);
   repeat:
  	if (!wi->bio) {

  		wi->bio = nilfs_alloc_seg_bio(wi->nilfs, wi->blocknr + wi->end,

  					      wi->nr_vecs);
  		if (unlikely(!wi->bio))
  			return -ENOMEM;
  	}
  
  	len = bio_add_page(wi->bio, bh->b_page, bh->b_size, bh_offset(bh));
  	if (len == bh->b_size) {
  		wi->end++;
  		return 0;
  	}
  	/* bio is FULL */

  	err = nilfs_segbuf_submit_bio(segbuf, wi, mode);

  	/* never submit current bh */
  	if (likely(!err))
  		goto repeat;
  	return err;
  }

  /**
   * nilfs_segbuf_write - submit write requests of a log
   * @segbuf: buffer storing a log to be written
   * @nilfs: nilfs object
   *
   * Return Value: On Success, 0 is returned. On Error, one of the following
   * negative error code is returned.
   *
   * %-EIO - I/O error
   *
   * %-ENOMEM - Insufficient memory available.
   */

  static int nilfs_segbuf_write(struct nilfs_segment_buffer *segbuf,
  			      struct the_nilfs *nilfs)

  {

  	struct nilfs_write_info wi;

  	struct buffer_head *bh;

  	int res = 0, rw = WRITE;

  	wi.nilfs = nilfs;
  	nilfs_segbuf_prepare_write(segbuf, &wi);

  	list_for_each_entry(bh, &segbuf->sb_segsum_buffers, b_assoc_buffers) {

  		res = nilfs_segbuf_submit_bh(segbuf, &wi, bh, rw);

  		if (unlikely(res))
  			goto failed_bio;
  	}
  
  	list_for_each_entry(bh, &segbuf->sb_payload_buffers, b_assoc_buffers) {

  		res = nilfs_segbuf_submit_bh(segbuf, &wi, bh, rw);

  		if (unlikely(res))
  			goto failed_bio;
  	}

  	if (wi.bio) {

  		/*
  		 * Last BIO is always sent through the following
  		 * submission.
  		 */

  		rw |= REQ_SYNC;

  		res = nilfs_segbuf_submit_bio(segbuf, &wi, rw);

  	}

   failed_bio:

  	return res;

  }
  
  /**
   * nilfs_segbuf_wait - wait for completion of requested BIOs

   * @segbuf: segment buffer

   *
   * Return Value: On Success, 0 is returned. On Error, one of the following
   * negative error code is returned.
   *
   * %-EIO - I/O error
   */

  static int nilfs_segbuf_wait(struct nilfs_segment_buffer *segbuf)

  {
  	int err = 0;

  	if (!segbuf->sb_nbio)

  		return 0;
  
  	do {

  		wait_for_completion(&segbuf->sb_bio_event);
  	} while (--segbuf->sb_nbio > 0);

  	if (unlikely(atomic_read(&segbuf->sb_err) > 0)) {

  		printk(KERN_ERR "NILFS: IO error writing segment
  ");
  		err = -EIO;

  	}
  	return err;
  }