zftape-compress.c

linux-2.6.15.6

	}
	TRACE_EXIT (unsigned int)max_out_sz;
}

/* print some statistics about the efficiency of the compression to
 * the kernel log 
 */
static void zftc_stats(void)
{
	TRACE_FUN(ft_t_flow);

	if (TRACE_LEVEL < ft_t_info) {
		TRACE_EXIT;
	}
	if (zftc_wr_uncompressed != 0) {
		if (zftc_wr_compressed > (1<<14)) {
			TRACE(ft_t_info, "compression statistics (writing):\n"
			      KERN_INFO " compr./uncmpr.   : %3d %%",
			      (((zftc_wr_compressed>>10) * 100)
			       / (zftc_wr_uncompressed>>10)));
		} else {
			TRACE(ft_t_info, "compression statistics (writing):\n"
			      KERN_INFO " compr./uncmpr.   : %3d %%",
			      ((zftc_wr_compressed * 100)
			       / zftc_wr_uncompressed));
		}
	}
	if (zftc_rd_uncompressed != 0) {
		if (zftc_rd_compressed > (1<<14)) {
			TRACE(ft_t_info, "compression statistics (reading):\n"
			      KERN_INFO " compr./uncmpr.   : %3d %%",
			      (((zftc_rd_compressed>>10) * 100)
			       / (zftc_rd_uncompressed>>10)));
		} else {
			TRACE(ft_t_info, "compression statistics (reading):\n"
			      KERN_INFO " compr./uncmpr.   : %3d %%",
			      ((zftc_rd_compressed * 100)
			       / zftc_rd_uncompressed));
		}
	}
	/* only print it once: */
	zftc_wr_uncompressed = 
		zftc_wr_compressed  =
		zftc_rd_uncompressed =
		zftc_rd_compressed   = 0;
	TRACE_EXIT;
}

/* start new compressed block 
 */
static int start_new_cseg(cmpr_info *cluster, 
			  char *dst_buf, 
			  const zft_position *pos,
			  const unsigned int blk_sz,
			  const char *src_buf,
			  const int this_segs_sz,
			  const int qic113)
{
	int size_left;
	int cp_cnt;
	int buf_pos;
	TRACE_FUN(ft_t_flow);

	size_left = this_segs_sz - sizeof(__u16) - cluster->cmpr_sz;
	TRACE(ft_t_data_flow,"\n" 
	      KERN_INFO "segment size   : %d\n"
	      KERN_INFO "compressed_sz: %d\n"
	      KERN_INFO "size_left      : %d",
	      this_segs_sz, cluster->cmpr_sz, size_left);
	if (size_left > 18) { /* start a new cluseter */
		cp_cnt = cluster->cmpr_sz;
		cluster->cmpr_sz = 0;
		buf_pos = cp_cnt + sizeof(__u16);
		PUT2(dst_buf, 0, buf_pos);

		if (qic113) {
			__s64 foffs = pos->volume_pos;
			if (cp_cnt) foffs += (__s64)blk_sz;

			TRACE(ft_t_data_flow, "new style QIC-113 header");
			PUT8(dst_buf, buf_pos, foffs);
			buf_pos += sizeof(__s64);
		} else {
			__u32 foffs = (__u32)pos->volume_pos;
			if (cp_cnt) foffs += (__u32)blk_sz;
			
			TRACE(ft_t_data_flow, "old style QIC-80MC header");
			PUT4(dst_buf, buf_pos, foffs);
			buf_pos += sizeof(__u32);
		}
	} else if (size_left >= 0) {
		cp_cnt = cluster->cmpr_sz;
		cluster->cmpr_sz = 0;
		buf_pos = cp_cnt + sizeof(__u16);
		PUT2(dst_buf, 0, buf_pos);  
		/* zero unused part of segment. */
		memset(dst_buf + buf_pos, '\0', size_left);
		buf_pos = this_segs_sz;
	} else { /* need entire segment and more space */
		PUT2(dst_buf, 0, 0); 
		cp_cnt = this_segs_sz - sizeof(__u16);
		cluster->cmpr_sz  -= cp_cnt;
		buf_pos = this_segs_sz;
	}
	memcpy(dst_buf + sizeof(__u16), src_buf + cluster->cmpr_pos, cp_cnt);
	cluster->cmpr_pos += cp_cnt;
	TRACE_EXIT buf_pos;
}

/* return-value: the number of bytes removed from the user-buffer
 *               `src_buf' or error code
 *
 *  int *write_cnt           : how much actually has been moved to the
 *                             dst_buf. Need not be initialized when
 *                             function returns with an error code
 *                             (negativ return value) 
 *  __u8 *dst_buf            : kernel space buffer where the has to be
 *                             copied to. The contents of this buffers
 *                             goes to a specific segment.
 *  const int seg_sz         : the size of the segment dst_buf will be
 *                             copied to.
 *  const zft_position *pos  : struct containing the coordinates in
 *                             the current volume (byte position,
 *                             segment id of current segment etc)
 *  const zft_volinfo *volume: information about the current volume,
 *                             size etc.
 *  const __u8 *src_buf      : user space buffer that contains the
 *                             data the user wants to be written to
 *                             tape.
 *  const int req_len        : the amount of data the user wants to be
 *                             written to tape.
 */
static int zftc_write(int *write_cnt,
		      __u8 *dst_buf, const int seg_sz,
		      const __u8 __user *src_buf, const int req_len,
		      const zft_position *pos, const zft_volinfo *volume)
{
	int req_len_left = req_len;
	int result;
	int len_left;
	int buf_pos_write = pos->seg_byte_pos;
	TRACE_FUN(ft_t_flow);
	
	/* Note: we do not unlock the module because
	 * there are some values cached in that `cseg' variable.  We
	 * don't don't want to use this information when being
	 * unloaded by kerneld even when the tape is full or when we
	 * cannot allocate enough memory.
	 */
	if (pos->tape_pos > (volume->size-volume->blk_sz-ZFT_CMPR_OVERHEAD)) {
		TRACE_EXIT -ENOSPC;
	}    
	if (zft_allocate_cmpr_mem(volume->blk_sz) < 0) {
		/* should we unlock the module? But it shouldn't 
		 * be locked anyway ...
		 */
		TRACE_EXIT -ENOMEM;
	}
	if (buf_pos_write == 0) { /* fill a new segment */
		*write_cnt = buf_pos_write = start_new_cseg(&cseg,
							    dst_buf,
							    pos,
							    volume->blk_sz,
							    zftc_buf, 
							    seg_sz,
							    volume->qic113);
		if (cseg.cmpr_sz == 0 && cseg.cmpr_pos != 0) {
			req_len_left -= result = volume->blk_sz;
			cseg.cmpr_pos  = 0;
		} else {
			result = 0;
		}
	} else {
		*write_cnt = result = 0;
	}
	
	len_left = seg_sz - buf_pos_write;
	while ((req_len_left > 0) && (len_left > 18)) {
		/* now we have some size left for a new compressed
		 * block.  We know, that the compression buffer is
		 * empty (else there wouldn't be any space left).  
		 */
		if (copy_from_user(zftc_scratch_buf, src_buf + result, 
				   volume->blk_sz) != 0) {
			TRACE_EXIT -EFAULT;
		}
		req_len_left -= volume->blk_sz;
		cseg.cmpr_sz = zft_compress(zftc_scratch_buf, volume->blk_sz, 
					    zftc_buf);
		if (cseg.cmpr_sz < 0) {
			cseg.uncmpr = 0x8000;
			cseg.cmpr_sz = -cseg.cmpr_sz;
		} else {
			cseg.uncmpr = 0;
		}
		/* increment "result" iff we copied the entire
		 * compressed block to the zft_deblock_buf 
		 */
		len_left -= sizeof(__u16);
		if (len_left >= cseg.cmpr_sz) {
			len_left -= cseg.count = cseg.cmpr_sz;
			cseg.cmpr_pos = cseg.cmpr_sz = 0;
			result += volume->blk_sz;
		} else {
			cseg.cmpr_sz       -= 
				cseg.cmpr_pos =
				cseg.count    = len_left;
			len_left = 0;
		}
		PUT2(dst_buf, buf_pos_write, cseg.uncmpr | cseg.count);
		buf_pos_write += sizeof(__u16);
		memcpy(dst_buf + buf_pos_write, zftc_buf, cseg.count);
		buf_pos_write += cseg.count;
		*write_cnt    += cseg.count + sizeof(__u16);
		FT_SIGNAL_EXIT(_DONT_BLOCK);
	}
	/* erase the remainder of the segment if less than 18 bytes
	 * left (18 bytes is due to the QIC-80 standard) 
	 */
	if (len_left <= 18) {
		memset(dst_buf + buf_pos_write, '\0', len_left);
		(*write_cnt) += len_left;
	}
	TRACE(ft_t_data_flow, "returning %d", result);
	TRACE_EXIT result;
}   

/* out:
 *
 * int *read_cnt: the number of bytes we removed from the zft_deblock_buf
 *                (result)
 * int *to_do   : the remaining size of the read-request.
 *
 * in:
 *
 * char *buff          : buff is the address of the upper part of the user
 *                       buffer, that hasn't been filled with data yet.

 * int buf_pos_read    : copy of from _ftape_read()
 * int buf_len_read    : copy of buf_len_rd from _ftape_read()
 * char *zft_deblock_buf: zft_deblock_buf
 * unsigned short blk_sz: the block size valid for this volume, may differ
 *                            from zft_blk_sz.
 * int finish: if != 0 means that this is the last segment belonging
 *  to this volume
 * returns the amount of data actually copied to the user-buffer
 *
 * to_do MUST NOT SHRINK except to indicate an EOF. In this case *to_do has to
 * be set to 0 
 */
static int zftc_read (int *read_cnt, 
		      __u8  __user *dst_buf, const int to_do, 
		      const __u8 *src_buf, const int seg_sz, 
		      const zft_position *pos, const zft_volinfo *volume)
{          
	int uncompressed_sz;         
	int result = 0;
	int remaining = to_do;
	TRACE_FUN(ft_t_flow);

	TRACE_CATCH(zft_allocate_cmpr_mem(volume->blk_sz),);
	if (pos->seg_byte_pos == 0) {
		/* new segment just read
		 */
		TRACE_CATCH(get_cseg(&cseg, src_buf, seg_sz, volume),
			    *read_cnt = 0);
		memcpy(zftc_buf + cseg.cmpr_pos, src_buf + sizeof(__u16), 
		       cseg.count);
		cseg.cmpr_pos += cseg.count;
		*read_cnt      = cseg.offset;
		DUMP_CMPR_INFO(ft_t_noise /* ft_t_any */, "", &cseg);
	} else {
		*read_cnt = 0;
	}
	/* loop and uncompress until user buffer full or
	 * deblock-buffer empty 
	 */
	TRACE(ft_t_data_flow, "compressed_sz: %d, compos : %d, *read_cnt: %d",
	      cseg.cmpr_sz, cseg.cmpr_pos, *read_cnt);
	while ((cseg.spans == 0) && (remaining > 0)) {
		if (cseg.cmpr_pos  != 0) { /* cmpr buf is not empty */
			uncompressed_sz = 
				zft_uncompress(zftc_buf,
					       cseg.uncmpr == 0x8000 ?
					       -cseg.cmpr_pos : cseg.cmpr_pos,
					       zftc_scratch_buf,
					       volume->blk_sz);
			if (uncompressed_sz != volume->blk_sz) {
				*read_cnt = 0;
				TRACE_ABORT(-EIO, ft_t_warn,
				      "Uncompressed blk (%d) != blk size (%d)",
				      uncompressed_sz, volume->blk_sz);
			}       
			if (copy_to_user(dst_buf + result, 
					 zftc_scratch_buf, 
					 uncompressed_sz) != 0 ) {
				TRACE_EXIT -EFAULT;
			}
			remaining      -= uncompressed_sz;
			result     += uncompressed_sz;
			cseg.cmpr_pos  = 0;
		}                                              
		if (remaining > 0) {
			get_next_cluster(&cseg, src_buf, seg_sz, 
					 volume->end_seg == pos->seg_pos);
			if (cseg.count != 0) {
				memcpy(zftc_buf, src_buf + cseg.offset,
				       cseg.count);
				cseg.cmpr_pos = cseg.count;
				cseg.offset  += cseg.count;
				*read_cnt += cseg.count + sizeof(__u16);
			} else {
				remaining = 0;
			}
		}
		TRACE(ft_t_data_flow, "\n" 
		      KERN_INFO "compressed_sz: %d\n"
		      KERN_INFO "compos       : %d\n"
		      KERN_INFO "*read_cnt    : %d",
		      cseg.cmpr_sz, cseg.cmpr_pos, *read_cnt);
	}
	if (seg_sz - cseg.offset <= 18) {
		*read_cnt += seg_sz - cseg.offset;
		TRACE(ft_t_data_flow, "expanding read cnt to: %d", *read_cnt);
	}
	TRACE(ft_t_data_flow, "\n"
	      KERN_INFO "segment size   : %d\n"
	      KERN_INFO "read count     : %d\n"
	      KERN_INFO "buf_pos_read   : %d\n"
	      KERN_INFO "remaining      : %d",
		seg_sz, *read_cnt, pos->seg_byte_pos, 
		seg_sz - *read_cnt - pos->seg_byte_pos);
	TRACE(ft_t_data_flow, "returning: %d", result);
	TRACE_EXIT result;
}                

/* seeks to the new data-position. Reads sometimes a segment.
 *  
 * start_seg and end_seg give the boundaries of the current volume
 * blk_sz is the blk_sz of the current volume as stored in the
 * volume label
 *
 * We don't allow blocksizes less than 1024 bytes, therefore we don't need
 * a 64 bit argument for new_block_pos.
 */

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);
static int slow_seek_forward_until_error(const unsigned int distance,
					 cmpr_info *c_info, zft_position *pos, 
					 const zft_volinfo *volume, __u8 *buf);
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);
static int slow_seek_forward(unsigned int dest, cmpr_info *c_info,
			     zft_position *pos, const zft_volinfo *volume,
			     __u8 *buf);
static int compute_seg_pos(unsigned int dest, zft_position *pos,
			   const zft_volinfo *volume);

#define ZFT_SLOW_SEEK_THRESHOLD  10 /* segments */
#define ZFT_FAST_SEEK_MAX_TRIALS 10 /* times */
#define ZFT_FAST_SEEK_BACKUP     10 /* segments */

static int zftc_seek(unsigned int new_block_pos,
		     zft_position *pos, const zft_volinfo *volume, __u8 *buf)
{
	unsigned int dest;
	int limit;
	int distance;
	int result = 0;
	int seg_dist;
	int new_seg;
	int old_seg = 0;
	int fast_seek_trials = 0;
	TRACE_FUN(ft_t_flow);

	if (new_block_pos == 0) {
		pos->seg_pos      = volume->start_seg;
		pos->seg_byte_pos = 0;
		pos->volume_pos   = 0;
		zftc_reset();
		TRACE_EXIT 0;
	}
	dest = new_block_pos * (volume->blk_sz >> 10);
	distance = dest - (pos->volume_pos >> 10);
	while (distance != 0) {
		seg_dist = compute_seg_pos(dest, pos, volume);
		TRACE(ft_t_noise, "\n"
		      KERN_INFO "seg_dist: %d\n"
		      KERN_INFO "distance: %d\n"
		      KERN_INFO "dest    : %d\n"
		      KERN_INFO "vpos    : %d\n"
		      KERN_INFO "seg_pos : %d\n"
		      KERN_INFO "trials  : %d",
		      seg_dist, distance, dest,
		      (unsigned int)(pos->volume_pos>>10), pos->seg_pos,
		      fast_seek_trials);
		if (distance > 0) {