/*
   *  linux/fs/hpfs/buffer.c
   *
   *  Mikulas Patocka (mikulas@artax.karlin.mff.cuni.cz), 1998-1999
   *
   *  general buffer i/o
   */

  #include <linux/sched.h>

  #include <linux/slab.h>

  #include <linux/blkdev.h>

  #include "hpfs_fn.h"

  secno hpfs_search_hotfix_map(struct super_block *s, secno sec)
  {
  	unsigned i;
  	struct hpfs_sb_info *sbi = hpfs_sb(s);
  	for (i = 0; unlikely(i < sbi->n_hotfixes); i++) {
  		if (sbi->hotfix_from[i] == sec) {
  			return sbi->hotfix_to[i];
  		}
  	}
  	return sec;
  }
  
  unsigned hpfs_search_hotfix_map_for_range(struct super_block *s, secno sec, unsigned n)
  {
  	unsigned i;
  	struct hpfs_sb_info *sbi = hpfs_sb(s);
  	for (i = 0; unlikely(i < sbi->n_hotfixes); i++) {
  		if (sbi->hotfix_from[i] >= sec && sbi->hotfix_from[i] < sec + n) {
  			n = sbi->hotfix_from[i] - sec;
  		}
  	}
  	return n;
  }

  void hpfs_prefetch_sectors(struct super_block *s, unsigned secno, int n)
  {
  	struct buffer_head *bh;
  	struct blk_plug plug;
  
  	if (n <= 0 || unlikely(secno >= hpfs_sb(s)->sb_fs_size))
  		return;

  	if (unlikely(hpfs_search_hotfix_map_for_range(s, secno, n) != n))
  		return;

  	bh = sb_find_get_block(s, secno);
  	if (bh) {
  		if (buffer_uptodate(bh)) {
  			brelse(bh);
  			return;
  		}
  		brelse(bh);
  	};
  
  	blk_start_plug(&plug);
  	while (n > 0) {
  		if (unlikely(secno >= hpfs_sb(s)->sb_fs_size))
  			break;
  		sb_breadahead(s, secno);
  		secno++;
  		n--;
  	}
  	blk_finish_plug(&plug);
  }

  /* Map a sector into a buffer and return pointers to it and to the buffer. */
  
  void *hpfs_map_sector(struct super_block *s, unsigned secno, struct buffer_head **bhp,
  		 int ahead)
  {
  	struct buffer_head *bh;

  	hpfs_lock_assert(s);

  	hpfs_prefetch_sectors(s, secno, ahead);

  	cond_resched();

  	*bhp = bh = sb_bread(s, hpfs_search_hotfix_map(s, secno));

  	if (bh != NULL)
  		return bh->b_data;
  	else {

  		pr_err("%s(): read error
  ", __func__);

  		return NULL;
  	}
  }
  
  /* Like hpfs_map_sector but don't read anything */
  
  void *hpfs_get_sector(struct super_block *s, unsigned secno, struct buffer_head **bhp)
  {
  	struct buffer_head *bh;
  	/*return hpfs_map_sector(s, secno, bhp, 0);*/

  	hpfs_lock_assert(s);

  	cond_resched();

  	if ((*bhp = bh = sb_getblk(s, hpfs_search_hotfix_map(s, secno))) != NULL) {

  		if (!buffer_uptodate(bh)) wait_on_buffer(bh);
  		set_buffer_uptodate(bh);
  		return bh->b_data;
  	} else {

  		pr_err("%s(): getblk failed
  ", __func__);

  		return NULL;
  	}
  }
  
  /* Map 4 sectors into a 4buffer and return pointers to it and to the buffer. */
  
  void *hpfs_map_4sectors(struct super_block *s, unsigned secno, struct quad_buffer_head *qbh,
  		   int ahead)
  {

  	char *data;

  	hpfs_lock_assert(s);

  	cond_resched();
  
  	if (secno & 3) {

  		pr_err("%s(): unaligned read
  ", __func__);

  		return NULL;
  	}

  	hpfs_prefetch_sectors(s, secno, 4 + ahead);

  	if (!hpfs_map_sector(s, secno + 0, &qbh->bh[0], 0)) goto bail0;
  	if (!hpfs_map_sector(s, secno + 1, &qbh->bh[1], 0)) goto bail1;
  	if (!hpfs_map_sector(s, secno + 2, &qbh->bh[2], 0)) goto bail2;
  	if (!hpfs_map_sector(s, secno + 3, &qbh->bh[3], 0)) goto bail3;

  
  	if (likely(qbh->bh[1]->b_data == qbh->bh[0]->b_data + 1 * 512) &&
  	    likely(qbh->bh[2]->b_data == qbh->bh[0]->b_data + 2 * 512) &&
  	    likely(qbh->bh[3]->b_data == qbh->bh[0]->b_data + 3 * 512)) {
  		return qbh->data = qbh->bh[0]->b_data;
  	}

  	qbh->data = data = kmalloc(2048, GFP_NOFS);

  	if (!data) {

  		pr_err("%s(): out of memory
  ", __func__);

  		goto bail4;

  	}

  	memcpy(data + 0 * 512, qbh->bh[0]->b_data, 512);
  	memcpy(data + 1 * 512, qbh->bh[1]->b_data, 512);
  	memcpy(data + 2 * 512, qbh->bh[2]->b_data, 512);
  	memcpy(data + 3 * 512, qbh->bh[3]->b_data, 512);

  
  	return data;

   bail4:
  	brelse(qbh->bh[3]);

   bail3:
  	brelse(qbh->bh[2]);
   bail2:
  	brelse(qbh->bh[1]);
   bail1:
  	brelse(qbh->bh[0]);
   bail0:

  	return NULL;
  }
  
  /* Don't read sectors */
  
  void *hpfs_get_4sectors(struct super_block *s, unsigned secno,
                            struct quad_buffer_head *qbh)
  {
  	cond_resched();

  	hpfs_lock_assert(s);

  	if (secno & 3) {

  		pr_err("%s(): unaligned read
  ", __func__);

  		return NULL;
  	}

  	if (!hpfs_get_sector(s, secno + 0, &qbh->bh[0])) goto bail0;
  	if (!hpfs_get_sector(s, secno + 1, &qbh->bh[1])) goto bail1;
  	if (!hpfs_get_sector(s, secno + 2, &qbh->bh[2])) goto bail2;
  	if (!hpfs_get_sector(s, secno + 3, &qbh->bh[3])) goto bail3;
  
  	if (likely(qbh->bh[1]->b_data == qbh->bh[0]->b_data + 1 * 512) &&
  	    likely(qbh->bh[2]->b_data == qbh->bh[0]->b_data + 2 * 512) &&
  	    likely(qbh->bh[3]->b_data == qbh->bh[0]->b_data + 3 * 512)) {
  		return qbh->data = qbh->bh[0]->b_data;
  	}

  	if (!(qbh->data = kmalloc(2048, GFP_NOFS))) {

  		pr_err("%s(): out of memory
  ", __func__);

  		goto bail4;

  	}

  	return qbh->data;

  bail4:
  	brelse(qbh->bh[3]);
  bail3:
  	brelse(qbh->bh[2]);
  bail2:
  	brelse(qbh->bh[1]);
  bail1:
  	brelse(qbh->bh[0]);
  bail0:

  	return NULL;
  }
  	
  
  void hpfs_brelse4(struct quad_buffer_head *qbh)
  {

  	if (unlikely(qbh->data != qbh->bh[0]->b_data))
  		kfree(qbh->data);

  	brelse(qbh->bh[0]);

  	brelse(qbh->bh[1]);
  	brelse(qbh->bh[2]);
  	brelse(qbh->bh[3]);

  }	
  
  void hpfs_mark_4buffers_dirty(struct quad_buffer_head *qbh)
  {

  	if (unlikely(qbh->data != qbh->bh[0]->b_data)) {
  		memcpy(qbh->bh[0]->b_data, qbh->data + 0 * 512, 512);
  		memcpy(qbh->bh[1]->b_data, qbh->data + 1 * 512, 512);
  		memcpy(qbh->bh[2]->b_data, qbh->data + 2 * 512, 512);
  		memcpy(qbh->bh[3]->b_data, qbh->data + 3 * 512, 512);
  	}

  	mark_buffer_dirty(qbh->bh[0]);
  	mark_buffer_dirty(qbh->bh[1]);
  	mark_buffer_dirty(qbh->bh[2]);
  	mark_buffer_dirty(qbh->bh[3]);
  }