drivers/char/ftape/compressor/zftape-compress.c

   1 /*
   2  *      Copyright (C) 1994-1997 Claus-Justus Heine
   3
   4  This program is free software; you can redistribute it and/or
   5  modify it under the terms of the GNU General Public License as
   6  published by the Free Software Foundation; either version 2, or (at
   7  your option) any later version.
   8
   9  This program is distributed in the hope that it will be useful, but
  10  WITHOUT ANY WARRANTY; without even the implied warranty of
  11  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  General Public License for more details.
  13
  14  You should have received a copy of the GNU General Public License
  15  along with this program; see the file COPYING.  If not, write to
  16  the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139,
  17  USA.
  18
  19  *
  20  *     This file implements a "generic" interface between the *
  21  *     zftape-driver and a compression-algorithm. The *
  22  *     compression-algorithm currently used is a LZ77. I use the *
  23  *     implementation lzrw3 by Ross N. Williams (Renaissance *
  24  *     Software). The compression program itself is in the file
  25  *     lzrw3.c * and lzrw3.h.  To adopt another compression algorithm
  26  *     the functions * zft_compress() and zft_uncompress() must be
  27  *     changed * appropriately. See below.
  28  */
  29
  30 #include <linux/errno.h>
  31 #include <linux/mm.h>
  32 #include <linux/module.h>
  33
  34 #include <linux/zftape.h>
  35
  36 #include <asm/uaccess.h>
  37
  38 #include "../zftape/zftape-init.h"
  39 #include "../zftape/zftape-eof.h"
  40 #include "../zftape/zftape-ctl.h"
  41 #include "../zftape/zftape-write.h"
  42 #include "../zftape/zftape-read.h"
  43 #include "../zftape/zftape-rw.h"
  44 #include "../compressor/zftape-compress.h"
  45 #include "../zftape/zftape-vtbl.h"
  46 #include "../compressor/lzrw3.h"
  47
  48 /*
  49  *   global variables
  50  */
  51
  52 /* I handle the allocation of this buffer as a special case, because
  53  * it's size varies depending on the tape length inserted.
  54  */
  55
  56 /* local variables
  57  */
  58 static void *zftc_wrk_mem = NULL;
  59 static __u8 *zftc_buf     = NULL;
  60 static void *zftc_scratch_buf  = NULL;
  61
  62 /* compression statistics
  63  */
  64 static unsigned int zftc_wr_uncompressed = 0;
  65 static unsigned int zftc_wr_compressed   = 0;
  66 static unsigned int zftc_rd_uncompressed = 0;
  67 static unsigned int zftc_rd_compressed   = 0;
  68
  69 /* forward */
  70 static int  zftc_write(int *write_cnt,
  71                        __u8 *dst_buf, const int seg_sz,
  72                        const __u8 __user *src_buf, const int req_len,
  73                        const zft_position *pos, const zft_volinfo *volume);
  74 static int  zftc_read(int *read_cnt,
  75                       __u8  __user *dst_buf, const int to_do,
  76                       const __u8 *src_buf, const int seg_sz,
  77                       const zft_position *pos, const zft_volinfo *volume);
  78 static int  zftc_seek(unsigned int new_block_pos,
  79                       zft_position *pos, const zft_volinfo *volume,
  80                       __u8 *buffer);
  81 static void zftc_lock   (void);
  82 static void zftc_reset  (void);
  83 static void zftc_cleanup(void);
  84 static void zftc_stats      (void);
  85
  86 /* compressed segment. This conforms to QIC-80-MC, Revision K.
  87  *
  88  * Rev. K applies to tapes with `fixed length format' which is
  89  * indicated by format code 2,3 and 5. See below for format code 4 and 6
  90  *
  91  * 2 bytes: offset of compression segment structure
  92  *          29k > offset >= 29k-18: data from previous segment ens in this
  93  *                                  segment and no compressed block starts
  94  *                                  in this segment
  95  *                     offset == 0: data from previous segment occupies entire
  96  *                                  segment and continues in next segment
  97  * n bytes: remainder from previous segment
  98  *
  99  * Rev. K:
 100  * 4 bytes: 4 bytes: files set byte offset
 101  * Post Rev. K and QIC-3020/3020:
 102  * 8 bytes: 8 bytes: files set byte offset
 103  * 2 bytes: byte count N (amount of data following)
 104  *          bit 15 is set if data is compressed, bit 15 is not
 105  *          set if data is uncompressed
 106  * N bytes: data (as much as specified in the byte count)
 107  * 2 bytes: byte count N_1 of next cluster
 108  * N_1 bytes: data of next cluset
 109  * 2 bytes: byte count N_2 of next cluster
 110  * N_2 bytes: ...
 111  *
 112  * Note that the `N' byte count accounts only for the bytes that in the
 113  * current segment if the cluster spans to the next segment.
 114  */
 115
 116 typedef struct
 117 {
 118         int cmpr_pos;             /* actual position in compression buffer */
 119         int cmpr_sz;              /* what is left in the compression buffer
 120                                    * when copying the compressed data to the
 121                                    * deblock buffer
 122                                    */
 123         unsigned int first_block; /* location of header information in
 124                                    * this segment
 125                                    */
 126         unsigned int count;       /* amount of data of current block
 127                                    * contained in current segment
 128                                    */
 129         unsigned int offset;      /* offset in current segment */
 130         unsigned int spans:1;     /* might continue in next segment */
 131         unsigned int uncmpr;      /* 0x8000 if this block contains
 132                                    * uncompressed data
 133                                    */
 134         __s64 foffs;              /* file set byte offset, same as in
 135                                    * compression map segment
 136                                    */
 137 } cmpr_info;
 138
 139 static cmpr_info cseg; /* static data. Must be kept uptodate and shared by
 140                         * read, write and seek functions
 141                         */
 142
 143 #define DUMP_CMPR_INFO(level, msg, info)                                \
 144         TRACE(level, msg "\n"                                           \
 145               KERN_INFO "cmpr_pos   : %d\n"                             \
 146               KERN_INFO "cmpr_sz    : %d\n"                             \
 147               KERN_INFO "first_block: %d\n"                             \
 148               KERN_INFO "count      : %d\n"                             \
 149               KERN_INFO "offset     : %d\n"                             \
 150               KERN_INFO "spans      : %d\n"                             \
 151               KERN_INFO "uncmpr     : 0x%04x\n"                         \
 152               KERN_INFO "foffs      : " LL_X,                           \
 153               (info)->cmpr_pos, (info)->cmpr_sz, (info)->first_block,   \
 154               (info)->count, (info)->offset, (info)->spans == 1,        \
 155               (info)->uncmpr, LL((info)->foffs))
 156
 157 /*   dispatch compression segment info, return error code
 158  *
 159  *   afterwards, cseg->offset points to start of data of the NEXT
 160  *   compressed block, and cseg->count contains the amount of data
 161  *   left in the actual compressed block. cseg->spans is set to 1 if
 162  *   the block is continued in the following segment. Otherwise it is
 163  *   set to 0.
 164  */
 165 static int get_cseg (cmpr_info *cinfo, const __u8 *buff,
 166                      const unsigned int seg_sz,
 167                      const zft_volinfo *volume)
 168 {
 169         TRACE_FUN(ft_t_flow);
 170
 171         cinfo->first_block = GET2(buff, 0);
 172         if (cinfo->first_block == 0) { /* data spans to next segment */
 173                 cinfo->count  = seg_sz - sizeof(__u16);
 174                 cinfo->offset = seg_sz;
 175                 cinfo->spans = 1;
 176         } else { /* cluster definetely ends in this segment */
 177                 if (cinfo->first_block > seg_sz) {
 178                         /* data corrupted */
 179                         TRACE_ABORT(-EIO, ft_t_err, "corrupted data:\n"
 180                                     KERN_INFO "segment size: %d\n"
 181                                     KERN_INFO "first block : %d",
 182                                     seg_sz, cinfo->first_block);
 183                 }
 184                 cinfo->count  = cinfo->first_block - sizeof(__u16);
 185                 cinfo->offset = cinfo->first_block;
 186                 cinfo->spans = 0;
 187         }
 188         /* now get the offset the first block should have in the
 189          * uncompressed data stream.
 190          *
 191          * For this magic `18' refer to CRF-3 standard or QIC-80MC,
 192          * Rev. K.
 193          */
 194         if ((seg_sz - cinfo->offset) > 18) {
 195                 if (volume->qic113) { /* > revision K */
 196                         TRACE(ft_t_data_flow, "New QIC-113 compliance");
 197                         cinfo->foffs = GET8(buff, cinfo->offset);
 198                         cinfo->offset += sizeof(__s64);
 199                 } else {
 200                         TRACE(/* ft_t_data_flow */ ft_t_noise, "pre QIC-113 version");
 201                         cinfo->foffs   = (__s64)GET4(buff, cinfo->offset);
 202                         cinfo->offset += sizeof(__u32);
 203                 }
 204         }
 205         if (cinfo->foffs > volume->size) {
 206                 TRACE_ABORT(-EIO, ft_t_err, "Inconsistency:\n"
 207                             KERN_INFO "offset in current volume: %d\n"
 208                             KERN_INFO "size of current volume  : %d",
 209                             (int)(cinfo->foffs>>10), (int)(volume->size>>10));
 210         }
 211         if (cinfo->cmpr_pos + cinfo->count > volume->blk_sz) {
 212                 TRACE_ABORT(-EIO, ft_t_err, "Inconsistency:\n"
 213                             KERN_INFO "block size : %d\n"
 214                             KERN_INFO "data record: %d",
 215                             volume->blk_sz, cinfo->cmpr_pos + cinfo->count);
 216         }
 217         DUMP_CMPR_INFO(ft_t_noise /* ft_t_any */, "", cinfo);
 218         TRACE_EXIT 0;
 219 }
 220
 221 /*  This one is called, when a new cluster starts in same segment.
 222  *
 223  *  Note: if this is the first cluster in the current segment, we must
 224  *  not check whether there are more than 18 bytes available because
 225  *  this have already been done in get_cseg() and there may be less
 226  *  than 18 bytes available due to header information.
 227  *
 228  */
 229 static void get_next_cluster(cmpr_info *cluster, const __u8 *buff,
 230                              const int seg_sz, const int finish)
 231 {
 232         TRACE_FUN(ft_t_flow);
 233
 234         if (seg_sz - cluster->offset > 18 || cluster->foffs != 0) {
 235                 cluster->count   = GET2(buff, cluster->offset);
 236                 cluster->uncmpr  = cluster->count & 0x8000;
 237                 cluster->count  -= cluster->uncmpr;
 238                 cluster->offset += sizeof(__u16);
 239                 cluster->foffs   = 0;
 240                 if ((cluster->offset + cluster->count) < seg_sz) {
 241                         cluster->spans = 0;
 242                 } else if (cluster->offset + cluster->count == seg_sz) {
 243                         cluster->spans = !finish;
 244                 } else {
 245                         /* either an error or a volume written by an
 246                          * old version. If this is a data error, then we'll
 247                          * catch it later.
 248                          */
 249                         TRACE(ft_t_data_flow, "Either error or old volume");
 250                         cluster->spans = 1;
 251                         cluster->count = seg_sz - cluster->offset;
 252                 }
 253         } else {
 254                 cluster->count = 0;
 255                 cluster->spans = 0;
 256                 cluster->foffs = 0;
 257         }
 258         DUMP_CMPR_INFO(ft_t_noise /* ft_t_any */ , "", cluster);
 259         TRACE_EXIT;
 260 }
 261
 262 static void zftc_lock(void)
 263 {
 264 }
 265
 266 /*  this function is needed for zftape_reset_position in zftape-io.c
 267  */
 268 static void zftc_reset(void)
 269 {
 270         TRACE_FUN(ft_t_flow);
 271
 272         memset((void *)&cseg, '\0', sizeof(cseg));
 273         zftc_stats();
 274         TRACE_EXIT;
 275 }
 276
 277 static int cmpr_mem_initialized = 0;
 278 static unsigned int alloc_blksz = 0;
 279
 280 static int zft_allocate_cmpr_mem(unsigned int blksz)
 281 {
 282         TRACE_FUN(ft_t_flow);
 283
 284         if (cmpr_mem_initialized && blksz == alloc_blksz) {
 285                 TRACE_EXIT 0;
 286         }
 287         TRACE_CATCH(zft_vmalloc_once(&zftc_wrk_mem, CMPR_WRK_MEM_SIZE),
 288                     zftc_cleanup());
 289         TRACE_CATCH(zft_vmalloc_always(&zftc_buf, blksz + CMPR_OVERRUN),
 290                     zftc_cleanup());
 291         alloc_blksz = blksz;
 292         TRACE_CATCH(zft_vmalloc_always(&zftc_scratch_buf, blksz+CMPR_OVERRUN),
 293                     zftc_cleanup());
 294         cmpr_mem_initialized = 1;
 295         TRACE_EXIT 0;
 296 }
 297
 298 static void zftc_cleanup(void)
 299 {
 300         TRACE_FUN(ft_t_flow);
 301
 302         zft_vfree(&zftc_wrk_mem, CMPR_WRK_MEM_SIZE);
 303         zft_vfree(&zftc_buf, alloc_blksz + CMPR_OVERRUN);
 304         zft_vfree(&zftc_scratch_buf, alloc_blksz + CMPR_OVERRUN);
 305         cmpr_mem_initialized = alloc_blksz = 0;
 306         TRACE_EXIT;
 307 }
 308
 309 /*****************************************************************************
 310  *                                                                           *
 311  *  The following two functions "ftape_compress()" and                       *
 312  *  "ftape_uncompress()" are the interface to the actual compression         *
 313  *  algorithm (i.e. they are calling the "compress()" function from          *
 314  *  the lzrw3 package for now). These routines could quite easily be         *
 315  *  changed to adopt another compression algorithm instead of lzrw3,         *
 316  *  which currently is used.                                                 *
 317  *                                                                           *
 318  *****************************************************************************/
 319
 320 /* called by zft_compress_write() to perform the compression. Must
 321  * return the size of the compressed data.
 322  *
 323  * NOTE: The size of the compressed data should not exceed the size of
 324  *       the uncompressed data. Most compression algorithms have means
 325  *       to store data unchanged if the "compressed" data amount would
 326  *       exceed the original one. Mostly this is done by storing some
 327  *       flag-bytes in front of the compressed data to indicate if it
 328  *       is compressed or not. Thus the worst compression result
 329  *       length is the original length plus those flag-bytes.
 330  *
 331  *       We don't want that, as the QIC-80 standard provides a means
 332  *       of marking uncompressed blocks by simply setting bit 15 of
 333  *       the compressed block's length. Thus a compessed block can
 334  *       have at most a length of 2^15-1 bytes. The QIC-80 standard
 335  *       restricts the block-length even further, allowing only 29k -
 336  *       6 bytes.
 337  *
 338  *       Currently, the maximum blocksize used by zftape is 28k.
 339  *
 340  *       In short: don't exceed the length of the input-package, set
 341  *       bit 15 of the compressed size to 1 if you have copied data
 342  *       instead of compressing it.
 343  */
 344 static int zft_compress(__u8 *in_buffer, unsigned int in_sz, __u8 *out_buffer)
 345 {
 346         __s32 compressed_sz;
 347         TRACE_FUN(ft_t_flow);
 348
 349
 350         lzrw3_compress(COMPRESS_ACTION_COMPRESS, zftc_wrk_mem,
 351                        in_buffer, in_sz, out_buffer, &compressed_sz);
 352         if (TRACE_LEVEL >= ft_t_info) {
 353                 /*  the compiler will optimize this away when
 354                  *  compiled with NO_TRACE_AT_ALL option
 355                  */
 356                 TRACE(ft_t_data_flow, "\n"
 357                       KERN_INFO "before compression: %d bytes\n"
 358                       KERN_INFO "after compresison : %d bytes",
 359                       in_sz,
 360                       (int)(compressed_sz < 0
 361                       ? -compressed_sz : compressed_sz));
 362                 /*  for statistical purposes
 363                  */
 364                 zftc_wr_compressed   += (compressed_sz < 0
 365                                            ? -compressed_sz : compressed_sz);
 366                 zftc_wr_uncompressed += in_sz;
 367         }
 368         TRACE_EXIT (int)compressed_sz;
 369 }
 370
 371 /* called by zft_compress_read() to decompress the data. Must
 372  * return the size of the decompressed data for sanity checks
 373  * (compared with zft_blk_sz)
 374  *
 375  * NOTE: Read the note for zft_compress() above!  If bit 15 of the
 376  *       parameter in_sz is set, then the data in in_buffer isn't
 377  *       compressed, which must be handled by the un-compression
 378  *       algorithm. (I changed lzrw3 to handle this.)
 379  *
 380  *  The parameter max_out_sz is needed to prevent buffer overruns when
 381  *  uncompressing corrupt data.
 382  */
 383 static unsigned int zft_uncompress(__u8 *in_buffer,
 384                                    int in_sz,
 385                                    __u8 *out_buffer,
 386                                    unsigned int max_out_sz)
 387 {
 388         TRACE_FUN(ft_t_flow);
 389
 390         lzrw3_compress(COMPRESS_ACTION_DECOMPRESS, zftc_wrk_mem,
 391                        in_buffer, (__s32)in_sz,
 392                        out_buffer, (__u32 *)&max_out_sz);
 393
 394         if (TRACE_LEVEL >= ft_t_info) {
 395                 TRACE(ft_t_data_flow, "\n"
 396                       KERN_INFO "before decompression: %d bytes\n"
 397                       KERN_INFO "after decompression : %d bytes",
 398                       in_sz < 0 ? -in_sz : in_sz,(int)max_out_sz);
 399                 /*  for statistical purposes
 400                  */
 401                 zftc_rd_compressed   += in_sz < 0 ? -in_sz : in_sz;
 402                 zftc_rd_uncompressed += max_out_sz;
 403         }
 404         TRACE_EXIT (unsigned int)max_out_sz;
 405 }
 406
 407 /* print some statistics about the efficiency of the compression to
 408  * the kernel log
 409  */
 410 static void zftc_stats(void)
 411 {
 412         TRACE_FUN(ft_t_flow);
 413
 414         if (TRACE_LEVEL < ft_t_info) {
 415                 TRACE_EXIT;
 416         }
 417         if (zftc_wr_uncompressed != 0) {
 418                 if (zftc_wr_compressed > (1<<14)) {
 419                         TRACE(ft_t_info, "compression statistics (writing):\n"
 420                               KERN_INFO " compr./uncmpr.   : %3d %%",
 421                               (((zftc_wr_compressed>>10) * 100)
 422                                / (zftc_wr_uncompressed>>10)));
 423                 } else {
 424                         TRACE(ft_t_info, "compression statistics (writing):\n"
 425                               KERN_INFO " compr./uncmpr.   : %3d %%",
 426                               ((zftc_wr_compressed * 100)
 427                                / zftc_wr_uncompressed));
 428                 }
 429         }
 430         if (zftc_rd_uncompressed != 0) {
 431                 if (zftc_rd_compressed > (1<<14)) {
 432                         TRACE(ft_t_info, "compression statistics (reading):\n"
 433                               KERN_INFO " compr./uncmpr.   : %3d %%",
 434                               (((zftc_rd_compressed>>10) * 100)
 435                                / (zftc_rd_uncompressed>>10)));
 436                 } else {
 437                         TRACE(ft_t_info, "compression statistics (reading):\n"
 438                               KERN_INFO " compr./uncmpr.   : %3d %%",
 439                               ((zftc_rd_compressed * 100)
 440                                / zftc_rd_uncompressed));
 441                 }
 442         }
 443         /* only print it once: */
 444         zftc_wr_uncompressed =
 445                 zftc_wr_compressed  =
 446                 zftc_rd_uncompressed =
 447                 zftc_rd_compressed   = 0;
 448         TRACE_EXIT;
 449 }
 450
 451 /* start new compressed block
 452  */
 453 static int start_new_cseg(cmpr_info *cluster,
 454                           char *dst_buf,
 455                           const zft_position *pos,
 456                           const unsigned int blk_sz,
 457                           const char *src_buf,
 458                           const int this_segs_sz,
 459                           const int qic113)
 460 {
 461         int size_left;
 462         int cp_cnt;
 463         int buf_pos;
 464         TRACE_FUN(ft_t_flow);
 465
 466         size_left = this_segs_sz - sizeof(__u16) - cluster->cmpr_sz;
 467         TRACE(ft_t_data_flow,"\n"
 468               KERN_INFO "segment size   : %d\n"
 469               KERN_INFO "compressed_sz: %d\n"
 470               KERN_INFO "size_left      : %d",
 471               this_segs_sz, cluster->cmpr_sz, size_left);
 472         if (size_left > 18) { /* start a new cluseter */
 473                 cp_cnt = cluster->cmpr_sz;
 474                 cluster->cmpr_sz = 0;
 475                 buf_pos = cp_cnt + sizeof(__u16);
 476                 PUT2(dst_buf, 0, buf_pos);
 477
 478                 if (qic113) {
 479                         __s64 foffs = pos->volume_pos;
 480                         if (cp_cnt) foffs += (__s64)blk_sz;
 481
 482                         TRACE(ft_t_data_flow, "new style QIC-113 header");
 483                         PUT8(dst_buf, buf_pos, foffs);
 484                         buf_pos += sizeof(__s64);
 485                 } else {
 486                         __u32 foffs = (__u32)pos->volume_pos;
 487                         if (cp_cnt) foffs += (__u32)blk_sz;
 488
 489                         TRACE(ft_t_data_flow, "old style QIC-80MC header");
 490                         PUT4(dst_buf, buf_pos, foffs);
 491                         buf_pos += sizeof(__u32);
 492                 }
 493         } else if (size_left >= 0) {
 494                 cp_cnt = cluster->cmpr_sz;
 495                 cluster->cmpr_sz = 0;
 496                 buf_pos = cp_cnt + sizeof(__u16);
 497                 PUT2(dst_buf, 0, buf_pos);
 498                 /* zero unused part of segment. */
 499                 memset(dst_buf + buf_pos, '\0', size_left);
 500                 buf_pos = this_segs_sz;
 501         } else { /* need entire segment and more space */
 502                 PUT2(dst_buf, 0, 0);
 503                 cp_cnt = this_segs_sz - sizeof(__u16);
 504                 cluster->cmpr_sz  -= cp_cnt;
 505                 buf_pos = this_segs_sz;
 506         }
 507         memcpy(dst_buf + sizeof(__u16), src_buf + cluster->cmpr_pos, cp_cnt);
 508         cluster->cmpr_pos += cp_cnt;
 509         TRACE_EXIT buf_pos;
 510 }
 511
 512 /* return-value: the number of bytes removed from the user-buffer
 513  *               `src_buf' or error code
 514  *
 515  *  int *write_cnt           : how much actually has been moved to the
 516  *                             dst_buf. Need not be initialized when
 517  *                             function returns with an error code
 518  *                             (negativ return value)
 519  *  __u8 *dst_buf            : kernel space buffer where the has to be
 520  *                             copied to. The contents of this buffers
 521  *                             goes to a specific segment.
 522  *  const int seg_sz         : the size of the segment dst_buf will be
 523  *                             copied to.
 524  *  const zft_position *pos  : struct containing the coordinates in
 525  *                             the current volume (byte position,
 526  *                             segment id of current segment etc)
 527  *  const zft_volinfo *volume: information about the current volume,
 528  *                             size etc.
 529  *  const __u8 *src_buf      : user space buffer that contains the
 530  *                             data the user wants to be written to
 531  *                             tape.
 532  *  const int req_len        : the amount of data the user wants to be
 533  *                             written to tape.
 534  */
 535 static int zftc_write(int *write_cnt,
 536                       __u8 *dst_buf, const int seg_sz,
 537                       const __u8 __user *src_buf, const int req_len,
 538                       const zft_position *pos, const zft_volinfo *volume)
 539 {
 540         int req_len_left = req_len;
 541         int result;
 542         int len_left;
 543         int buf_pos_write = pos->seg_byte_pos;
 544         TRACE_FUN(ft_t_flow);
 545
 546         /* Note: we do not unlock the module because
 547          * there are some values cached in that `cseg' variable.  We
 548          * don't don't want to use this information when being
 549          * unloaded by kerneld even when the tape is full or when we
 550          * cannot allocate enough memory.
 551          */
 552         if (pos->tape_pos > (volume->size-volume->blk_sz-ZFT_CMPR_OVERHEAD)) {
 553                 TRACE_EXIT -ENOSPC;
 554         }
 555         if (zft_allocate_cmpr_mem(volume->blk_sz) < 0) {
 556                 /* should we unlock the module? But it shouldn't
 557                  * be locked anyway ...
 558                  */
 559                 TRACE_EXIT -ENOMEM;
 560         }
 561         if (buf_pos_write == 0) { /* fill a new segment */
 562                 *write_cnt = buf_pos_write = start_new_cseg(&cseg,
 563                                                             dst_buf,
 564                                                             pos,
 565                                                             volume->blk_sz,
 566                                                             zftc_buf,
 567                                                             seg_sz,
 568                                                             volume->qic113);
 569                 if (cseg.cmpr_sz == 0 && cseg.cmpr_pos != 0) {
 570                         req_len_left -= result = volume->blk_sz;
 571                         cseg.cmpr_pos  = 0;
 572                 } else {
 573                         result = 0;
 574                 }
 575         } else {
 576                 *write_cnt = result = 0;
 577         }
 578
 579         len_left = seg_sz - buf_pos_write;
 580         while ((req_len_left > 0) && (len_left > 18)) {
 581                 /* now we have some size left for a new compressed
 582                  * block.  We know, that the compression buffer is
 583                  * empty (else there wouldn't be any space left).
 584                  */
 585                 if (copy_from_user(zftc_scratch_buf, src_buf + result,
 586                                    volume->blk_sz) != 0) {
 587                         TRACE_EXIT -EFAULT;
 588                 }
 589                 req_len_left -= volume->blk_sz;
 590                 cseg.cmpr_sz = zft_compress(zftc_scratch_buf, volume->blk_sz,
 591                                             zftc_buf);
 592                 if (cseg.cmpr_sz < 0) {
 593                         cseg.uncmpr = 0x8000;
 594                         cseg.cmpr_sz = -cseg.cmpr_sz;
 595                 } else {
 596                         cseg.uncmpr = 0;
 597                 }
 598                 /* increment "result" iff we copied the entire
 599                  * compressed block to the zft_deblock_buf
 600                  */
 601                 len_left -= sizeof(__u16);
 602                 if (len_left >= cseg.cmpr_sz) {
 603                         len_left -= cseg.count = cseg.cmpr_sz;
 604                         cseg.cmpr_pos = cseg.cmpr_sz = 0;
 605                         result += volume->blk_sz;
 606                 } else {
 607                         cseg.cmpr_sz       -=
 608                                 cseg.cmpr_pos =
 609                                 cseg.count    = len_left;
 610                         len_left = 0;
 611                 }
 612                 PUT2(dst_buf, buf_pos_write, cseg.uncmpr | cseg.count);
 613                 buf_pos_write += sizeof(__u16);
 614                 memcpy(dst_buf + buf_pos_write, zftc_buf, cseg.count);
 615                 buf_pos_write += cseg.count;
 616                 *write_cnt    += cseg.count + sizeof(__u16);
 617                 FT_SIGNAL_EXIT(_DONT_BLOCK);
 618         }
 619         /* erase the remainder of the segment if less than 18 bytes
 620          * left (18 bytes is due to the QIC-80 standard)
 621          */
 622         if (len_left <= 18) {
 623                 memset(dst_buf + buf_pos_write, '\0', len_left);
 624                 (*write_cnt) += len_left;
 625         }
 626         TRACE(ft_t_data_flow, "returning %d", result);
 627         TRACE_EXIT result;
 628 }
 629
 630 /* out:
 631  *
 632  * int *read_cnt: the number of bytes we removed from the zft_deblock_buf
 633  *                (result)
 634  * int *to_do   : the remaining size of the read-request.
 635  *
 636  * in:
 637  *
 638  * char *buff          : buff is the address of the upper part of the user
 639  *                       buffer, that hasn't been filled with data yet.
 640
 641  * int buf_pos_read    : copy of from _ftape_read()
 642  * int buf_len_read    : copy of buf_len_rd from _ftape_read()
 643  * char *zft_deblock_buf: zft_deblock_buf
 644  * unsigned short blk_sz: the block size valid for this volume, may differ
 645  *                            from zft_blk_sz.
 646  * int finish: if != 0 means that this is the last segment belonging
 647  *  to this volume
 648  * returns the amount of data actually copied to the user-buffer
 649  *
 650  * to_do MUST NOT SHRINK except to indicate an EOF. In this case *to_do has to
 651  * be set to 0
 652  */
 653 static int zftc_read (int *read_cnt,
 654                       __u8  __user *dst_buf, const int to_do,
 655                       const __u8 *src_buf, const int seg_sz,
 656                       const zft_position *pos, const zft_volinfo *volume)
 657 {
 658         int uncompressed_sz;
 659         int result = 0;
 660         int remaining = to_do;
 661         TRACE_FUN(ft_t_flow);
 662
 663         TRACE_CATCH(zft_allocate_cmpr_mem(volume->blk_sz),);
 664         if (pos->seg_byte_pos == 0) {
 665                 /* new segment just read
 666                  */
 667                 TRACE_CATCH(get_cseg(&cseg, src_buf, seg_sz, volume),
 668                             *read_cnt = 0);
 669                 memcpy(zftc_buf + cseg.cmpr_pos, src_buf + sizeof(__u16),
 670                        cseg.count);
 671                 cseg.cmpr_pos += cseg.count;
 672                 *read_cnt      = cseg.offset;
 673                 DUMP_CMPR_INFO(ft_t_noise /* ft_t_any */, "", &cseg);
 674         } else {
 675                 *read_cnt = 0;
 676         }
 677         /* loop and uncompress until user buffer full or
 678          * deblock-buffer empty
 679          */
 680         TRACE(ft_t_data_flow, "compressed_sz: %d, compos : %d, *read_cnt: %d",
 681               cseg.cmpr_sz, cseg.cmpr_pos, *read_cnt);
 682         while ((cseg.spans == 0) && (remaining > 0)) {
 683                 if (cseg.cmpr_pos  != 0) { /* cmpr buf is not empty */
 684                         uncompressed_sz =
 685                                 zft_uncompress(zftc_buf,
 686                                                cseg.uncmpr == 0x8000 ?
 687                                                -cseg.cmpr_pos : cseg.cmpr_pos,
 688                                                zftc_scratch_buf,
 689                                                volume->blk_sz);
 690                         if (uncompressed_sz != volume->blk_sz) {
 691                                 *read_cnt = 0;
 692                                 TRACE_ABORT(-EIO, ft_t_warn,
 693                                       "Uncompressed blk (%d) != blk size (%d)",
 694                                       uncompressed_sz, volume->blk_sz);
 695                         }
 696                         if (copy_to_user(dst_buf + result,
 697                                          zftc_scratch_buf,
 698                                          uncompressed_sz) != 0 ) {
 699                                 TRACE_EXIT -EFAULT;
 700                         }
 701                         remaining      -= uncompressed_sz;
 702                         result     += uncompressed_sz;
 703                         cseg.cmpr_pos  = 0;
 704                 }
 705                 if (remaining > 0) {
 706                         get_next_cluster(&cseg, src_buf, seg_sz,
 707                                          volume->end_seg == pos->seg_pos);
 708                         if (cseg.count != 0) {
 709                                 memcpy(zftc_buf, src_buf + cseg.offset,
 710                                        cseg.count);
 711                                 cseg.cmpr_pos = cseg.count;
 712                                 cseg.offset  += cseg.count;
 713                                 *read_cnt += cseg.count + sizeof(__u16);
 714                         } else {
 715                                 remaining = 0;
 716                         }
 717                 }
 718                 TRACE(ft_t_data_flow, "\n"
 719                       KERN_INFO "compressed_sz: %d\n"
 720                       KERN_INFO "compos       : %d\n"
 721                       KERN_INFO "*read_cnt    : %d",
 722                       cseg.cmpr_sz, cseg.cmpr_pos, *read_cnt);
 723         }
 724         if (seg_sz - cseg.offset <= 18) {
 725                 *read_cnt += seg_sz - cseg.offset;
 726                 TRACE(ft_t_data_flow, "expanding read cnt to: %d", *read_cnt);
 727         }
 728         TRACE(ft_t_data_flow, "\n"
 729               KERN_INFO "segment size   : %d\n"
 730               KERN_INFO "read count     : %d\n"
 731               KERN_INFO "buf_pos_read   : %d\n"
 732               KERN_INFO "remaining      : %d",
 733                 seg_sz, *read_cnt, pos->seg_byte_pos,
 734                 seg_sz - *read_cnt - pos->seg_byte_pos);
 735         TRACE(ft_t_data_flow, "returning: %d", result);
 736         TRACE_EXIT result;
 737 }
 738
 739 /* seeks to the new data-position. Reads sometimes a segment.
 740  *
 741  * start_seg and end_seg give the boundaries of the current volume
 742  * blk_sz is the blk_sz of the current volume as stored in the
 743  * volume label
 744  *
 745  * We don't allow blocksizes less than 1024 bytes, therefore we don't need
 746  * a 64 bit argument for new_block_pos.
 747  */
 748
 749 static int seek_in_segment(const unsigned int to_do, cmpr_info  *c_info,
 750                            const char *src_buf, const int seg_sz,
 751                            const int seg_pos, const zft_volinfo *volume);
 752 static int slow_seek_forward_until_error(const unsigned int distance,
 753                                          cmpr_info *c_info, zft_position *pos,
 754                                          const zft_volinfo *volume, __u8 *buf);
 755 static int search_valid_segment(unsigned int segment,
 756                                 const unsigned int end_seg,
 757                                 const unsigned int max_foffs,
 758                                 zft_position *pos, cmpr_info *c_info,
 759                                 const zft_volinfo *volume, __u8 *buf);
 760 static int slow_seek_forward(unsigned int dest, cmpr_info *c_info,
 761                              zft_position *pos, const zft_volinfo *volume,
 762                              __u8 *buf);
 763 static int compute_seg_pos(unsigned int dest, zft_position *pos,
 764                            const zft_volinfo *volume);
 765
 766 #define ZFT_SLOW_SEEK_THRESHOLD  10 /* segments */
 767 #define ZFT_FAST_SEEK_MAX_TRIALS 10 /* times */
 768 #define ZFT_FAST_SEEK_BACKUP     10 /* segments */
 769
 770 static int zftc_seek(unsigned int new_block_pos,
 771                      zft_position *pos, const zft_volinfo *volume, __u8 *buf)
 772 {
 773         unsigned int dest;
 774         int limit;
 775         int distance;
 776         int result = 0;
 777         int seg_dist;
 778         int new_seg;
 779         int old_seg = 0;
 780         int fast_seek_trials = 0;
 781         TRACE_FUN(ft_t_flow);
 782
 783         if (new_block_pos == 0) {
 784                 pos->seg_pos      = volume->start_seg;
 785                 pos->seg_byte_pos = 0;
 786                 pos->volume_pos   = 0;
 787                 zftc_reset();
 788                 TRACE_EXIT 0;
 789         }
 790         dest = new_block_pos * (volume->blk_sz >> 10);
 791         distance = dest - (pos->volume_pos >> 10);
 792         while (distance != 0) {
 793                 seg_dist = compute_seg_pos(dest, pos, volume);
 794                 TRACE(ft_t_noise, "\n"
 795                       KERN_INFO "seg_dist: %d\n"
 796                       KERN_INFO "distance: %d\n"
 797                       KERN_INFO "dest    : %d\n"
 798                       KERN_INFO "vpos    : %d\n"
 799                       KERN_INFO "seg_pos : %d\n"
 800                       KERN_INFO "trials  : %d",
 801                       seg_dist, distance, dest,
 802                       (unsigned int)(pos->volume_pos>>10), pos->seg_pos,
 803                       fast_seek_trials);
 804                 if (distance > 0) {
 805                         if (seg_dist < 0) {
 806                                 TRACE(ft_t_bug, "BUG: distance %d > 0, "
 807                                       "segment difference %d < 0",
 808                                       distance, seg_dist);
 809                                 result = -EIO;
 810                                 break;
 811                         }
 812                         new_seg = pos->seg_pos + seg_dist;
 813                         if (new_seg > volume->end_seg) {
 814                                 new_seg = volume->end_seg;
 815                         }
 816                         if (old_seg == new_seg || /* loop */
 817                             seg_dist <= ZFT_SLOW_SEEK_THRESHOLD ||
 818                             fast_seek_trials >= ZFT_FAST_SEEK_MAX_TRIALS) {
 819                                 TRACE(ft_t_noise, "starting slow seek:\n"
 820                                    KERN_INFO "fast seek failed too often: %s\n"
 821                                    KERN_INFO "near target position      : %s\n"
 822                                    KERN_INFO "looping between two segs  : %s",
 823                                       (fast_seek_trials >=
 824                                        ZFT_FAST_SEEK_MAX_TRIALS)
 825                                       ? "yes" : "no",
 826                                       (seg_dist <= ZFT_SLOW_SEEK_THRESHOLD)
 827                                       ? "yes" : "no",
 828                                       (old_seg == new_seg)
 829                                       ? "yes" : "no");
 830                                 result = slow_seek_forward(dest, &cseg,
 831                                                            pos, volume, buf);
 832                                 break;
 833                         }
 834                         old_seg = new_seg;
 835                         limit = volume->end_seg;
 836                         fast_seek_trials ++;
 837                         for (;;) {
 838                                 result = search_valid_segment(new_seg, limit,
 839                                                               volume->size,
 840                                                               pos, &cseg,
 841                                                               volume, buf);
 842                                 if (result == 0 || result == -EINTR) {
 843                                         break;
 844                                 }
 845                                 if (new_seg == volume->start_seg) {
 846                                         result = -EIO; /* set errror
 847                                                         * condition
 848                                                         */
 849                                         break;
 850                                 }
 851                                 limit    = new_seg;
 852                                 new_seg -= ZFT_FAST_SEEK_BACKUP;
 853                                 if (new_seg < volume->start_seg) {
 854                                         new_seg = volume->start_seg;
 855                                 }
 856                         }
 857                         if (result < 0) {
 858                                 TRACE(ft_t_warn,
 859                                       "Couldn't find a readable segment");
 860                                 break;
 861                         }
 862                 } else /* if (distance < 0) */ {
 863                         if (seg_dist > 0) {
 864                                 TRACE(ft_t_bug, "BUG: distance %d < 0, "
 865                                       "segment difference %d >0",
 866                                       distance, seg_dist);
 867                                 result = -EIO;
 868                                 break;
 869                         }
 870                         new_seg = pos->seg_pos + seg_dist;
 871                         if (fast_seek_trials > 0 && seg_dist == 0) {
 872                                 /* this avoids sticking to the same
 873                                  * segment all the time. On the other hand:
 874                                  * if we got here for the first time, and the
 875                                  * deblock_buffer still contains a valid
 876                                  * segment, then there is no need to skip to
 877                                  * the previous segment if the desired position
 878                                  * is inside this segment.
 879                                  */
 880                                 new_seg --;
 881                         }
 882                         if (new_seg < volume->start_seg) {
 883                                 new_seg = volume->start_seg;
 884                         }
 885                         limit   = pos->seg_pos;
 886                         fast_seek_trials ++;
 887                         for (;;) {
 888                                 result = search_valid_segment(new_seg, limit,
 889                                                               pos->volume_pos,
 890                                                               pos, &cseg,
 891                                                               volume, buf);
 892                                 if (result == 0 || result == -EINTR) {
 893                                         break;
 894                                 }
 895                                 if (new_seg == volume->start_seg) {
 896                                         result = -EIO; /* set errror
 897                                                         * condition
 898                                                         */
 899                                         break;
 900                                 }
 901                                 limit    = new_seg;
 902                                 new_seg -= ZFT_FAST_SEEK_BACKUP;
 903                                 if (new_seg < volume->start_seg) {
 904                                         new_seg = volume->start_seg;
 905                                 }
 906                         }
 907                         if (result < 0) {
 908                                 TRACE(ft_t_warn,
 909                                       "Couldn't find a readable segment");
 910                                 break;
 911                         }
 912                 }
 913                 distance = dest - (pos->volume_pos >> 10);
 914         }
 915         TRACE_EXIT result;
 916 }
 917
 918
 919 /*  advance inside the given segment at most to_do bytes.
 920  *  of kilobytes moved
 921  */
 922
 923 static int seek_in_segment(const unsigned int to_do,
 924                            cmpr_info  *c_info,
 925                            const char *src_buf,
 926                            const int seg_sz,
 927                            const int seg_pos,
 928                            const zft_volinfo *volume)
 929 {
 930         int result = 0;
 931         int blk_sz = volume->blk_sz >> 10;
 932         int remaining = to_do;
 933         TRACE_FUN(ft_t_flow);
 934
 935         if (c_info->offset == 0) {
 936                 /* new segment just read
 937                  */
 938                 TRACE_CATCH(get_cseg(c_info, src_buf, seg_sz, volume),);
 939                 c_info->cmpr_pos += c_info->count;
 940                 DUMP_CMPR_INFO(ft_t_noise, "", c_info);
 941         }
 942         /* loop and uncompress until user buffer full or
 943          * deblock-buffer empty
 944          */
 945         TRACE(ft_t_noise, "compressed_sz: %d, compos : %d",
 946               c_info->cmpr_sz, c_info->cmpr_pos);
 947         while (c_info->spans == 0 && remaining > 0) {
 948                 if (c_info->cmpr_pos  != 0) { /* cmpr buf is not empty */
 949                         result       += blk_sz;
 950                         remaining    -= blk_sz;
 951                         c_info->cmpr_pos = 0;
 952                 }
 953                 if (remaining > 0) {
 954                         get_next_cluster(c_info, src_buf, seg_sz,
 955                                          volume->end_seg == seg_pos);
 956                         if (c_info->count != 0) {
 957                                 c_info->cmpr_pos = c_info->count;
 958                                 c_info->offset  += c_info->count;
 959                         } else {
 960                                 break;
 961                         }
 962                 }
 963                 /*  Allow escape from this loop on signal!
 964                  */
 965                 FT_SIGNAL_EXIT(_DONT_BLOCK);
 966                 DUMP_CMPR_INFO(ft_t_noise, "", c_info);
 967                 TRACE(ft_t_noise, "to_do: %d", remaining);
 968         }
 969         if (seg_sz - c_info->offset <= 18) {
 970                 c_info->offset = seg_sz;
 971         }
 972         TRACE(ft_t_noise, "\n"
 973               KERN_INFO "segment size   : %d\n"
 974               KERN_INFO "buf_pos_read   : %d\n"
 975               KERN_INFO "remaining      : %d",
 976               seg_sz, c_info->offset,
 977               seg_sz - c_info->offset);
 978         TRACE_EXIT result;
 979 }
 980
 981 static int slow_seek_forward_until_error(const unsigned int distance,
 982                                          cmpr_info *c_info,
 983                                          zft_position *pos,
 984                                          const zft_volinfo *volume,
 985                                          __u8 *buf)
 986 {
 987         unsigned int remaining = distance;
 988         int seg_sz;
 989         int seg_pos;
 990         int result;
 991         TRACE_FUN(ft_t_flow);
 992
 993         seg_pos = pos->seg_pos;
 994         do {
 995                 TRACE_CATCH(seg_sz = zft_fetch_segment(seg_pos, buf,
 996                                                        FT_RD_AHEAD),);
 997                 /* now we have the contents of the actual segment in
 998                  * the deblock buffer
 999                  */
1000                 TRACE_CATCH(result = seek_in_segment(remaining, c_info, buf,
1001                                                      seg_sz, seg_pos,volume),);
1002                 remaining        -= result;
1003                 pos->volume_pos  += result<<10;
1004                 pos->seg_pos      = seg_pos;
1005                 pos->seg_byte_pos = c_info->offset;
1006                 seg_pos ++;
1007                 if (seg_pos <= volume->end_seg && c_info->offset == seg_sz) {
1008                         pos->seg_pos ++;
1009                         pos->seg_byte_pos = 0;
1010                         c_info->offset = 0;
1011                 }
1012                 /*  Allow escape from this loop on signal!
1013                  */
1014                 FT_SIGNAL_EXIT(_DONT_BLOCK);
1015                 TRACE(ft_t_noise, "\n"
1016                       KERN_INFO "remaining:  %d\n"
1017                       KERN_INFO "seg_pos:    %d\n"
1018                       KERN_INFO "end_seg:    %d\n"
1019                       KERN_INFO "result:     %d",
1020                       remaining, seg_pos, volume->end_seg, result);
1021         } while (remaining > 0 && seg_pos <= volume->end_seg);
1022         TRACE_EXIT 0;
1023 }
1024
1025 /* return segment id of next segment containing valid data, -EIO otherwise
1026  */
1027 static int search_valid_segment(unsigned int segment,
1028                                 const unsigned int end_seg,
1029                                 const unsigned int max_foffs,
1030                                 zft_position *pos,
1031                                 cmpr_info *c_info,
1032                                 const zft_volinfo *volume,
1033                                 __u8 *buf)
1034 {
1035         cmpr_info tmp_info;
1036         int seg_sz;
1037         TRACE_FUN(ft_t_flow);
1038
1039         memset(&tmp_info, 0, sizeof(cmpr_info));
1040         while (segment <= end_seg) {
1041                 FT_SIGNAL_EXIT(_DONT_BLOCK);
1042                 TRACE(ft_t_noise,
1043                       "Searching readable segment between %d and %d",
1044                       segment, end_seg);
1045                 seg_sz = zft_fetch_segment(segment, buf, FT_RD_AHEAD);
1046                 if ((seg_sz > 0) &&
1047                     (get_cseg (&tmp_info, buf, seg_sz, volume) >= 0) &&
1048                     (tmp_info.foffs != 0 || segment == volume->start_seg)) {
1049                         if ((tmp_info.foffs>>10) > max_foffs) {
1050                                 TRACE_ABORT(-EIO, ft_t_noise, "\n"
1051                                             KERN_INFO "cseg.foff: %d\n"
1052                                             KERN_INFO "dest     : %d",
1053                                             (int)(tmp_info.foffs >> 10),
1054                                             max_foffs);
1055                         }
1056                         DUMP_CMPR_INFO(ft_t_noise, "", &tmp_info);
1057                         *c_info           = tmp_info;
1058                         pos->seg_pos      = segment;
1059                         pos->volume_pos   = c_info->foffs;
1060                         pos->seg_byte_pos = c_info->offset;
1061                         TRACE(ft_t_noise, "found segment at %d", segment);
1062                         TRACE_EXIT 0;
1063                 }
1064                 segment++;
1065         }
1066         TRACE_EXIT -EIO;
1067 }
1068
1069 static int slow_seek_forward(unsigned int dest,
1070                              cmpr_info *c_info,
1071                              zft_position *pos,
1072                              const zft_volinfo *volume,
1073                              __u8 *buf)
1074 {
1075         unsigned int distance;
1076         int result = 0;
1077         TRACE_FUN(ft_t_flow);
1078
1079         distance = dest - (pos->volume_pos >> 10);
1080         while ((distance > 0) &&
1081                (result = slow_seek_forward_until_error(distance,
1082                                                        c_info,
1083                                                        pos,
1084                                                        volume,
1085                                                        buf)) < 0) {
1086                 if (result == -EINTR) {
1087                         break;
1088                 }
1089                 TRACE(ft_t_noise, "seg_pos: %d", pos->seg_pos);
1090                 /* the failing segment is either pos->seg_pos or
1091                  * pos->seg_pos + 1. There is no need to further try
1092                  * that segment, because ftape_read_segment() already
1093                  * has tried very much to read it. So we start with
1094                  * following segment, which is pos->seg_pos + 1
1095                  */
1096                 if(search_valid_segment(pos->seg_pos+1, volume->end_seg, dest,
1097                                         pos, c_info,
1098                                         volume, buf) < 0) {
1099                         TRACE(ft_t_noise, "search_valid_segment() failed");
1100                         result = -EIO;
1101                         break;
1102                 }
1103                 distance = dest - (pos->volume_pos >> 10);
1104                 result = 0;
1105                 TRACE(ft_t_noise, "segment: %d", pos->seg_pos);
1106                 /* found valid segment, retry the seek */
1107         }
1108         TRACE_EXIT result;
1109 }
1110
1111 static int compute_seg_pos(const unsigned int dest,
1112                            zft_position *pos,
1113                            const zft_volinfo *volume)
1114 {
1115         int segment;
1116         int distance = dest - (pos->volume_pos >> 10);
1117         unsigned int raw_size;
1118         unsigned int virt_size;
1119         unsigned int factor;
1120         TRACE_FUN(ft_t_flow);
1121
1122         if (distance >= 0) {
1123                 raw_size  = volume->end_seg - pos->seg_pos + 1;
1124                 virt_size = ((unsigned int)(volume->size>>10)
1125                              - (unsigned int)(pos->volume_pos>>10)
1126                              + FT_SECTORS_PER_SEGMENT - FT_ECC_SECTORS - 1);
1127                 virt_size /= FT_SECTORS_PER_SEGMENT - FT_ECC_SECTORS;
1128                 if (virt_size == 0 || raw_size == 0) {
1129                         TRACE_EXIT 0;
1130                 }
1131                 if (raw_size >= (1<<25)) {
1132                         factor = raw_size/(virt_size>>7);
1133                 } else {
1134                         factor = (raw_size<<7)/virt_size;
1135                 }
1136                 segment = distance/(FT_SECTORS_PER_SEGMENT-FT_ECC_SECTORS);
1137                 segment = (segment * factor)>>7;
1138         } else {
1139                 raw_size  = pos->seg_pos - volume->start_seg + 1;
1140                 virt_size = ((unsigned int)(pos->volume_pos>>10)
1141                              + FT_SECTORS_PER_SEGMENT - FT_ECC_SECTORS - 1);
1142                 virt_size /= FT_SECTORS_PER_SEGMENT - FT_ECC_SECTORS;
1143                 if (virt_size == 0 || raw_size == 0) {
1144                         TRACE_EXIT 0;
1145                 }
1146                 if (raw_size >= (1<<25)) {
1147                         factor = raw_size/(virt_size>>7);
1148                 } else {
1149                         factor = (raw_size<<7)/virt_size;
1150                 }
1151                 segment = distance/(FT_SECTORS_PER_SEGMENT-FT_ECC_SECTORS);
1152         }
1153         TRACE(ft_t_noise, "factor: %d/%d", factor, 1<<7);
1154         TRACE_EXIT segment;
1155 }
1156
1157 static struct zft_cmpr_ops cmpr_ops = {
1158         zftc_write,
1159         zftc_read,
1160         zftc_seek,
1161         zftc_lock,
1162         zftc_reset,
1163         zftc_cleanup
1164 };
1165
1166 int zft_compressor_init(void)
1167 {
1168         TRACE_FUN(ft_t_flow);
1169
1170 #ifdef MODULE
1171         printk(KERN_INFO "zftape compressor v1.00a 970514 for " FTAPE_VERSION "\n");
1172         if (TRACE_LEVEL >= ft_t_info) {
1173                 printk(
1174 KERN_INFO "(c) 1997 Claus-Justus Heine (claus@momo.math.rwth-aachen.de)\n"
1175 KERN_INFO "Compressor for zftape (lzrw3 algorithm)\n");
1176         }
1177 #else /* !MODULE */
1178         /* print a short no-nonsense boot message */
1179         printk("zftape compressor v1.00a 970514\n");
1180         printk("For use with " FTAPE_VERSION "\n");
1181 #endif /* MODULE */
1182         TRACE(ft_t_info, "zft_compressor_init @ 0x%p", zft_compressor_init);
1183         TRACE(ft_t_info, "installing compressor for zftape ...");
1184         TRACE_CATCH(zft_cmpr_register(&cmpr_ops),);
1185         TRACE_EXIT 0;
1186 }
1187
1188 #ifdef MODULE
1189
1190 MODULE_AUTHOR(
1191         "(c) 1996, 1997 Claus-Justus Heine (claus@momo.math.rwth-aachen.de");
1192 MODULE_DESCRIPTION(
1193 "Compression routines for zftape. Uses the lzrw3 algorithm by Ross Williams");
1194 MODULE_LICENSE("GPL");
1195
1196 /* Called by modules package when installing the driver
1197  */
1198 int init_module(void)
1199 {
1200         return zft_compressor_init();
1201 }
1202
1203 #endif /* MODULE */