zftape-compress.c

linux-2.6.15.6

			if (seg_dist < 0) {
				TRACE(ft_t_bug, "BUG: distance %d > 0, "
				      "segment difference %d < 0",
				      distance, seg_dist);
				result = -EIO;
				break;
			}
			new_seg = pos->seg_pos + seg_dist;
			if (new_seg > volume->end_seg) {
				new_seg = volume->end_seg;
			}
			if (old_seg == new_seg || /* loop */
			    seg_dist <= ZFT_SLOW_SEEK_THRESHOLD ||
			    fast_seek_trials >= ZFT_FAST_SEEK_MAX_TRIALS) {
				TRACE(ft_t_noise, "starting slow seek:\n"
				   KERN_INFO "fast seek failed too often: %s\n"
				   KERN_INFO "near target position      : %s\n"
				   KERN_INFO "looping between two segs  : %s",
				      (fast_seek_trials >= 
				       ZFT_FAST_SEEK_MAX_TRIALS)
				      ? "yes" : "no",
				      (seg_dist <= ZFT_SLOW_SEEK_THRESHOLD) 
				      ? "yes" : "no",
				      (old_seg == new_seg)
				      ? "yes" : "no");
				result = slow_seek_forward(dest, &cseg, 
							   pos, volume, buf);
				break;
			}
			old_seg = new_seg;
			limit = volume->end_seg;
			fast_seek_trials ++;
			for (;;) {
				result = search_valid_segment(new_seg, limit,
							      volume->size,
							      pos, &cseg,
							      volume, buf);
				if (result == 0 || result == -EINTR) {
					break;
				}
				if (new_seg == volume->start_seg) {
					result = -EIO; /* set errror 
							* condition
							*/
					break;
				}
				limit    = new_seg;
				new_seg -= ZFT_FAST_SEEK_BACKUP;
				if (new_seg < volume->start_seg) {
					new_seg = volume->start_seg;
				}
			}
			if (result < 0) {
				TRACE(ft_t_warn,
				      "Couldn't find a readable segment");
				break;
			}
		} else /* if (distance < 0) */ {
			if (seg_dist > 0) {
				TRACE(ft_t_bug, "BUG: distance %d < 0, "
				      "segment difference %d >0",
				      distance, seg_dist);
				result = -EIO;
				break;
			}
			new_seg = pos->seg_pos + seg_dist;
			if (fast_seek_trials > 0 && seg_dist == 0) {
				/* this avoids sticking to the same
				 * segment all the time. On the other hand:
				 * if we got here for the first time, and the
				 * deblock_buffer still contains a valid
				 * segment, then there is no need to skip to 
				 * the previous segment if the desired position
				 * is inside this segment.
				 */
				new_seg --;
			}
			if (new_seg < volume->start_seg) {
				new_seg = volume->start_seg;
			}
			limit   = pos->seg_pos;
			fast_seek_trials ++;
			for (;;) {
				result = search_valid_segment(new_seg, limit,
							      pos->volume_pos,
							      pos, &cseg,
							      volume, buf);
				if (result == 0 || result == -EINTR) {
					break;
				}
				if (new_seg == volume->start_seg) {
					result = -EIO; /* set errror 
							* condition
							*/
					break;
				}
				limit    = new_seg;
				new_seg -= ZFT_FAST_SEEK_BACKUP;
				if (new_seg < volume->start_seg) {
					new_seg = volume->start_seg;
				}
			}
			if (result < 0) {
				TRACE(ft_t_warn,
				      "Couldn't find a readable segment");
				break;
			}
		}
		distance = dest - (pos->volume_pos >> 10);
	}
	TRACE_EXIT result;
}


/*  advance inside the given segment at most to_do bytes.
 *  of kilobytes moved
 */

static int seek_in_segment(const unsigned int to_do,
			   cmpr_info  *c_info,
			   const char *src_buf, 
			   const int seg_sz, 
			   const int seg_pos,
			   const zft_volinfo *volume)
{
	int result = 0;
	int blk_sz = volume->blk_sz >> 10;
	int remaining = to_do;
	TRACE_FUN(ft_t_flow);

	if (c_info->offset == 0) {
		/* new segment just read
		 */
		TRACE_CATCH(get_cseg(c_info, src_buf, seg_sz, volume),);
		c_info->cmpr_pos += c_info->count;
		DUMP_CMPR_INFO(ft_t_noise, "", c_info);
	}
	/* loop and uncompress until user buffer full or
	 * deblock-buffer empty 
	 */
	TRACE(ft_t_noise, "compressed_sz: %d, compos : %d",
	      c_info->cmpr_sz, c_info->cmpr_pos);
	while (c_info->spans == 0 && remaining > 0) {
		if (c_info->cmpr_pos  != 0) { /* cmpr buf is not empty */
			result       += blk_sz;
			remaining    -= blk_sz;
			c_info->cmpr_pos = 0;
		}
		if (remaining > 0) {
			get_next_cluster(c_info, src_buf, seg_sz, 
					 volume->end_seg == seg_pos);
			if (c_info->count != 0) {
				c_info->cmpr_pos = c_info->count;
				c_info->offset  += c_info->count;
			} else {
				break;
			}
		}
		/*  Allow escape from this loop on signal!
		 */
		FT_SIGNAL_EXIT(_DONT_BLOCK);
		DUMP_CMPR_INFO(ft_t_noise, "", c_info);
		TRACE(ft_t_noise, "to_do: %d", remaining);
	}
	if (seg_sz - c_info->offset <= 18) {
		c_info->offset = seg_sz;
	}
	TRACE(ft_t_noise, "\n"
	      KERN_INFO "segment size   : %d\n"
	      KERN_INFO "buf_pos_read   : %d\n"
	      KERN_INFO "remaining      : %d",
	      seg_sz, c_info->offset,
	      seg_sz - c_info->offset);
	TRACE_EXIT result;
}                

static int slow_seek_forward_until_error(const unsigned int distance,
					 cmpr_info *c_info,
					 zft_position *pos, 
					 const zft_volinfo *volume,
					 __u8 *buf)
{
	unsigned int remaining = distance;
	int seg_sz;
	int seg_pos;
	int result;
	TRACE_FUN(ft_t_flow);
	
	seg_pos = pos->seg_pos;
	do {
		TRACE_CATCH(seg_sz = zft_fetch_segment(seg_pos, buf, 
						       FT_RD_AHEAD),);
		/* now we have the contents of the actual segment in
		 * the deblock buffer
		 */
		TRACE_CATCH(result = seek_in_segment(remaining, c_info, buf,
						     seg_sz, seg_pos,volume),);
		remaining        -= result;
		pos->volume_pos  += result<<10;
		pos->seg_pos      = seg_pos;
		pos->seg_byte_pos = c_info->offset;
		seg_pos ++;
		if (seg_pos <= volume->end_seg && c_info->offset == seg_sz) {
			pos->seg_pos ++;
			pos->seg_byte_pos = 0;
			c_info->offset = 0;
		}
		/*  Allow escape from this loop on signal!
		 */
		FT_SIGNAL_EXIT(_DONT_BLOCK);
		TRACE(ft_t_noise, "\n"
		      KERN_INFO "remaining:  %d\n"
		      KERN_INFO "seg_pos:    %d\n"
		      KERN_INFO "end_seg:    %d\n"
		      KERN_INFO "result:     %d",
		      remaining, seg_pos, volume->end_seg, result);  
	} while (remaining > 0 && seg_pos <= volume->end_seg);
	TRACE_EXIT 0;
}

/* return segment id of next segment containing valid data, -EIO otherwise
 */
static int search_valid_segment(unsigned int segment,
				const unsigned int end_seg,
				const unsigned int max_foffs,
				zft_position *pos,
				cmpr_info *c_info,
				const zft_volinfo *volume,
				__u8 *buf)
{
	cmpr_info tmp_info;
	int seg_sz;
	TRACE_FUN(ft_t_flow);
	
	memset(&tmp_info, 0, sizeof(cmpr_info));
	while (segment <= end_seg) {
		FT_SIGNAL_EXIT(_DONT_BLOCK);
		TRACE(ft_t_noise,
		      "Searching readable segment between %d and %d",
		      segment, end_seg);
		seg_sz = zft_fetch_segment(segment, buf, FT_RD_AHEAD);
		if ((seg_sz > 0) &&
		    (get_cseg (&tmp_info, buf, seg_sz, volume) >= 0) &&
		    (tmp_info.foffs != 0 || segment == volume->start_seg)) {
			if ((tmp_info.foffs>>10) > max_foffs) {
				TRACE_ABORT(-EIO, ft_t_noise, "\n"
					    KERN_INFO "cseg.foff: %d\n"
					    KERN_INFO "dest     : %d",
					    (int)(tmp_info.foffs >> 10),
					    max_foffs);
			}
			DUMP_CMPR_INFO(ft_t_noise, "", &tmp_info);
			*c_info           = tmp_info;
			pos->seg_pos      = segment;
			pos->volume_pos   = c_info->foffs;
			pos->seg_byte_pos = c_info->offset;
			TRACE(ft_t_noise, "found segment at %d", segment);
			TRACE_EXIT 0;
		}
		segment++;
	}
	TRACE_EXIT -EIO;
}

static int slow_seek_forward(unsigned int dest,
			     cmpr_info *c_info,
			     zft_position *pos,
			     const zft_volinfo *volume,
			     __u8 *buf)
{
	unsigned int distance;
	int result = 0;
	TRACE_FUN(ft_t_flow);
		
	distance = dest - (pos->volume_pos >> 10);
	while ((distance > 0) &&
	       (result = slow_seek_forward_until_error(distance,
						       c_info,
						       pos,
						       volume,
						       buf)) < 0) {
		if (result == -EINTR) {
			break;
		}
		TRACE(ft_t_noise, "seg_pos: %d", pos->seg_pos);
		/* the failing segment is either pos->seg_pos or
		 * pos->seg_pos + 1. There is no need to further try
		 * that segment, because ftape_read_segment() already
		 * has tried very much to read it. So we start with
		 * following segment, which is pos->seg_pos + 1
		 */
		if(search_valid_segment(pos->seg_pos+1, volume->end_seg, dest,
					pos, c_info,
					volume, buf) < 0) {
			TRACE(ft_t_noise, "search_valid_segment() failed");
			result = -EIO;
			break;
		}
		distance = dest - (pos->volume_pos >> 10);
		result = 0;
		TRACE(ft_t_noise, "segment: %d", pos->seg_pos);
		/* found valid segment, retry the seek */
	}
	TRACE_EXIT result;
}

static int compute_seg_pos(const unsigned int dest,
			   zft_position *pos,
			   const zft_volinfo *volume)
{
	int segment;
	int distance = dest - (pos->volume_pos >> 10);
	unsigned int raw_size;
	unsigned int virt_size;
	unsigned int factor;
	TRACE_FUN(ft_t_flow);

	if (distance >= 0) {
		raw_size  = volume->end_seg - pos->seg_pos + 1;
		virt_size = ((unsigned int)(volume->size>>10) 
			     - (unsigned int)(pos->volume_pos>>10)
			     + FT_SECTORS_PER_SEGMENT - FT_ECC_SECTORS - 1);
		virt_size /= FT_SECTORS_PER_SEGMENT - FT_ECC_SECTORS;
		if (virt_size == 0 || raw_size == 0) {
			TRACE_EXIT 0;
		}
		if (raw_size >= (1<<25)) {
			factor = raw_size/(virt_size>>7);
		} else {
			factor = (raw_size<<7)/virt_size;
		}
		segment = distance/(FT_SECTORS_PER_SEGMENT-FT_ECC_SECTORS);
		segment = (segment * factor)>>7;
	} else {
		raw_size  = pos->seg_pos - volume->start_seg + 1;
		virt_size = ((unsigned int)(pos->volume_pos>>10)
			     + FT_SECTORS_PER_SEGMENT - FT_ECC_SECTORS - 1);
		virt_size /= FT_SECTORS_PER_SEGMENT - FT_ECC_SECTORS;
		if (virt_size == 0 || raw_size == 0) {
			TRACE_EXIT 0;
		}
		if (raw_size >= (1<<25)) {
			factor = raw_size/(virt_size>>7);
		} else {
			factor = (raw_size<<7)/virt_size;
		}
		segment = distance/(FT_SECTORS_PER_SEGMENT-FT_ECC_SECTORS);
	}
	TRACE(ft_t_noise, "factor: %d/%d", factor, 1<<7);
	TRACE_EXIT segment;
}

static struct zft_cmpr_ops cmpr_ops = {
	zftc_write,
	zftc_read,
	zftc_seek,
	zftc_lock,
	zftc_reset,
	zftc_cleanup
};

int zft_compressor_init(void)
{
	TRACE_FUN(ft_t_flow);
	
#ifdef MODULE
	printk(KERN_INFO "zftape compressor v1.00a 970514 for " FTAPE_VERSION "\n");
        if (TRACE_LEVEL >= ft_t_info) {
		printk(
KERN_INFO "(c) 1997 Claus-Justus Heine ([e-mail])\n"
KERN_INFO "Compressor for zftape (lzrw3 algorithm)\n");
        }
#else /* !MODULE */
	/* print a short no-nonsense boot message */
	printk(KERN_INFO "zftape compressor v1.00a 970514\n");
	printk(KERN_INFO "For use with " FTAPE_VERSION "\n");
#endif /* MODULE */
	TRACE(ft_t_info, "zft_compressor_init @ 0x%p", zft_compressor_init);
	TRACE(ft_t_info, "installing compressor for zftape ...");
	TRACE_CATCH(zft_cmpr_register(&cmpr_ops),);
	TRACE_EXIT 0;
}

#ifdef MODULE

MODULE_AUTHOR(
	"(c) 1996, 1997 Claus-Justus Heine ([e-mail]");
MODULE_DESCRIPTION(
"Compression routines for zftape. Uses the lzrw3 algorithm by Ross Williams");
MODULE_LICENSE("GPL");

/* Called by modules package when installing the driver
 */
int init_module(void)
{
	return zft_compressor_init();
}

#endif /* MODULE */