fs/isofs/compress.c

   1 /* -*- linux-c -*- ------------------------------------------------------- *
   2  *
   3  *   Copyright 2001 H. Peter Anvin - All Rights Reserved
   4  *
   5  *   This program is free software; you can redistribute it and/or modify
   6  *   it under the terms of the GNU General Public License as published by
   7  *   the Free Software Foundation, Inc., 675 Mass Ave, Cambridge MA 02139,
   8  *   USA; either version 2 of the License, or (at your option) any later
   9  *   version; incorporated herein by reference.
  10  *
  11  * ----------------------------------------------------------------------- */
  12
  13 /*
  14  * linux/fs/isofs/compress.c
  15  *
  16  * Transparent decompression of files on an iso9660 filesystem
  17  */
  18
  19 #include <linux/config.h>
  20 #include <linux/module.h>
  21
  22 #include <linux/stat.h>
  23 #include <linux/time.h>
  24 #include <linux/iso_fs.h>
  25 #include <linux/kernel.h>
  26 #include <linux/major.h>
  27 #include <linux/mm.h>
  28 #include <linux/string.h>
  29 #include <linux/slab.h>
  30 #include <linux/errno.h>
  31 #include <linux/cdrom.h>
  32 #include <linux/init.h>
  33 #include <linux/nls.h>
  34 #include <linux/ctype.h>
  35 #include <linux/smp_lock.h>
  36 #include <linux/blkdev.h>
  37 #include <linux/vmalloc.h>
  38 #include <linux/zlib.h>
  39 #include <linux/buffer_head.h>
  40
  41 #include <asm/system.h>
  42 #include <asm/uaccess.h>
  43 #include <asm/semaphore.h>
  44
  45 #include "zisofs.h"
  46
  47 /* This should probably be global. */
  48 static char zisofs_sink_page[PAGE_CACHE_SIZE];
  49
  50 /*
  51  * This contains the zlib memory allocation and the mutex for the
  52  * allocation; this avoids failures at block-decompression time.
  53  */
  54 static void *zisofs_zlib_workspace;
  55 static struct semaphore zisofs_zlib_semaphore;
  56
  57 /*
  58  * When decompressing, we typically obtain more than one page
  59  * per reference.  We inject the additional pages into the page
  60  * cache as a form of readahead.
  61  */
  62 static int zisofs_readpage(struct file *file, struct page *page)
  63 {
  64         struct inode *inode = file->f_dentry->d_inode;
  65         struct address_space *mapping = inode->i_mapping;
  66         unsigned int maxpage, xpage, fpage, blockindex;
  67         unsigned long offset;
  68         unsigned long blockptr, blockendptr, cstart, cend, csize;
  69         struct buffer_head *bh, *ptrbh[2];
  70         unsigned long bufsize = ISOFS_BUFFER_SIZE(inode);
  71         unsigned int bufshift = ISOFS_BUFFER_BITS(inode);
  72         unsigned long bufmask  = bufsize - 1;
  73         int err = -EIO;
  74         int i;
  75         unsigned int header_size = ISOFS_I(inode)->i_format_parm[0];
  76         unsigned int zisofs_block_shift = ISOFS_I(inode)->i_format_parm[1];
  77         /* unsigned long zisofs_block_size = 1UL << zisofs_block_shift; */
  78         unsigned int zisofs_block_page_shift = zisofs_block_shift-PAGE_CACHE_SHIFT;
  79         unsigned long zisofs_block_pages = 1UL << zisofs_block_page_shift;
  80         unsigned long zisofs_block_page_mask = zisofs_block_pages-1;
  81         struct page *pages[zisofs_block_pages];
  82         unsigned long index = page->index;
  83         int indexblocks;
  84
  85         /* We have already been given one page, this is the one
  86            we must do. */
  87         xpage = index & zisofs_block_page_mask;
  88         pages[xpage] = page;
  89
  90         /* The remaining pages need to be allocated and inserted */
  91         offset = index & ~zisofs_block_page_mask;
  92         blockindex = offset >> zisofs_block_page_shift;
  93         maxpage = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
  94         maxpage = min(zisofs_block_pages, maxpage-offset);
  95
  96         for ( i = 0 ; i < maxpage ; i++, offset++ ) {
  97                 if ( i != xpage ) {
  98                         pages[i] = grab_cache_page_nowait(mapping, offset);
  99                 }
 100                 page = pages[i];
 101                 if ( page ) {
 102                         ClearPageError(page);
 103                         kmap(page);
 104                 }
 105         }
 106
 107         /* This is the last page filled, plus one; used in case of abort. */
 108         fpage = 0;
 109
 110         /* Find the pointer to this specific chunk */
 111         /* Note: we're not using isonum_731() here because the data is known aligned */
 112         /* Note: header_size is in 32-bit words (4 bytes) */
 113         blockptr = (header_size + blockindex) << 2;
 114         blockendptr = blockptr + 4;
 115
 116         indexblocks = ((blockptr^blockendptr) >> bufshift) ? 2 : 1;
 117         ptrbh[0] = ptrbh[1] = 0;
 118
 119         if ( isofs_get_blocks(inode, blockptr >> bufshift, ptrbh, indexblocks) != indexblocks ) {
 120                 if ( ptrbh[0] ) brelse(ptrbh[0]);
 121                 printk(KERN_DEBUG "zisofs: Null buffer on reading block table, inode = %lu, block = %lu\n",
 122                        inode->i_ino, blockptr >> bufshift);
 123                 goto eio;
 124         }
 125         ll_rw_block(READ, indexblocks, ptrbh);
 126
 127         bh = ptrbh[0];
 128         if ( !bh || (wait_on_buffer(bh), !buffer_uptodate(bh)) ) {
 129                 printk(KERN_DEBUG "zisofs: Failed to read block table, inode = %lu, block = %lu\n",
 130                        inode->i_ino, blockptr >> bufshift);
 131                 if ( ptrbh[1] )
 132                         brelse(ptrbh[1]);
 133                 goto eio;
 134         }
 135         cstart = le32_to_cpu(*(u32 *)(bh->b_data + (blockptr & bufmask)));
 136
 137         if ( indexblocks == 2 ) {
 138                 /* We just crossed a block boundary.  Switch to the next block */
 139                 brelse(bh);
 140                 bh = ptrbh[1];
 141                 if ( !bh || (wait_on_buffer(bh), !buffer_uptodate(bh)) ) {
 142                         printk(KERN_DEBUG "zisofs: Failed to read block table, inode = %lu, block = %lu\n",
 143                                inode->i_ino, blockendptr >> bufshift);
 144                         goto eio;
 145                 }
 146         }
 147         cend = le32_to_cpu(*(u32 *)(bh->b_data + (blockendptr & bufmask)));
 148         brelse(bh);
 149
 150         csize = cend-cstart;
 151
 152         /* Now page[] contains an array of pages, any of which can be NULL,
 153            and the locks on which we hold.  We should now read the data and
 154            release the pages.  If the pages are NULL the decompressed data
 155            for that particular page should be discarded. */
 156
 157         if ( csize == 0 ) {
 158                 /* This data block is empty. */
 159
 160                 for ( fpage = 0 ; fpage < maxpage ; fpage++ ) {
 161                         if ( (page = pages[fpage]) != NULL ) {
 162                                 memset(page_address(page), 0, PAGE_CACHE_SIZE);
 163
 164                                 flush_dcache_page(page);
 165                                 SetPageUptodate(page);
 166                                 kunmap(page);
 167                                 unlock_page(page);
 168                                 if ( fpage == xpage )
 169                                         err = 0; /* The critical page */
 170                                 else
 171                                         page_cache_release(page);
 172                         }
 173                 }
 174         } else {
 175                 /* This data block is compressed. */
 176                 z_stream stream;
 177                 int bail = 0, left_out = -1;
 178                 int zerr;
 179                 int needblocks = (csize + (cstart & bufmask) + bufmask) >> bufshift;
 180                 int haveblocks;
 181                 struct buffer_head *bhs[needblocks+1];
 182                 struct buffer_head **bhptr;
 183
 184                 /* Because zlib is not thread-safe, do all the I/O at the top. */
 185
 186                 blockptr = cstart >> bufshift;
 187                 memset(bhs, 0, (needblocks+1)*sizeof(struct buffer_head *));
 188                 haveblocks = isofs_get_blocks(inode, blockptr, bhs, needblocks);
 189                 ll_rw_block(READ, haveblocks, bhs);
 190
 191                 bhptr = &bhs[0];
 192                 bh = *bhptr++;
 193
 194                 /* First block is special since it may be fractional.
 195                    We also wait for it before grabbing the zlib
 196                    semaphore; odds are that the subsequent blocks are
 197                    going to come in in short order so we don't hold
 198                    the zlib semaphore longer than necessary. */
 199
 200                 if ( !bh || (wait_on_buffer(bh), !buffer_uptodate(bh)) ) {
 201                         printk(KERN_DEBUG "zisofs: Hit null buffer, fpage = %d, xpage = %d, csize = %ld\n",
 202                                fpage, xpage, csize);
 203                         goto b_eio;
 204                 }
 205                 stream.next_in  = bh->b_data + (cstart & bufmask);
 206                 stream.avail_in = min(bufsize-(cstart & bufmask), csize);
 207                 csize -= stream.avail_in;
 208
 209                 stream.workspace = zisofs_zlib_workspace;
 210                 down(&zisofs_zlib_semaphore);
 211
 212                 zerr = zlib_inflateInit(&stream);
 213                 if ( zerr != Z_OK ) {
 214                         if ( err && zerr == Z_MEM_ERROR )
 215                                 err = -ENOMEM;
 216                         printk(KERN_DEBUG "zisofs: zisofs_inflateInit returned %d\n",
 217                                zerr);
 218                         goto z_eio;
 219                 }
 220
 221                 while ( !bail && fpage < maxpage ) {
 222                         page = pages[fpage];
 223                         if ( page )
 224                                 stream.next_out = page_address(page);
 225                         else
 226                                 stream.next_out = (void *)&zisofs_sink_page;
 227                         stream.avail_out = PAGE_CACHE_SIZE;
 228
 229                         while ( stream.avail_out ) {
 230                                 int ao, ai;
 231                                 if ( stream.avail_in == 0 && left_out ) {
 232                                         if ( !csize ) {
 233                                                 printk(KERN_WARNING "zisofs: ZF read beyond end of input\n");
 234                                                 bail = 1;
 235                                                 break;
 236                                         } else {
 237                                                 bh = *bhptr++;
 238                                                 if ( !bh ||
 239                                                      (wait_on_buffer(bh), !buffer_uptodate(bh)) ) {
 240                                                         /* Reached an EIO */
 241                                                         printk(KERN_DEBUG "zisofs: Hit null buffer, fpage = %d, xpage = %d, csize = %ld\n",
 242                                                                fpage, xpage, csize);
 243
 244                                                         bail = 1;
 245                                                         break;
 246                                                 }
 247                                                 stream.next_in = bh->b_data;
 248                                                 stream.avail_in = min(csize,bufsize);
 249                                                 csize -= stream.avail_in;
 250                                         }
 251                                 }
 252                                 ao = stream.avail_out;  ai = stream.avail_in;
 253                                 zerr = zlib_inflate(&stream, Z_SYNC_FLUSH);
 254                                 left_out = stream.avail_out;
 255                                 if ( zerr == Z_BUF_ERROR && stream.avail_in == 0 )
 256                                         continue;
 257                                 if ( zerr != Z_OK ) {
 258                                         /* EOF, error, or trying to read beyond end of input */
 259                                         if ( err && zerr == Z_MEM_ERROR )
 260                                                 err = -ENOMEM;
 261                                         if ( zerr != Z_STREAM_END )
 262                                                 printk(KERN_DEBUG "zisofs: zisofs_inflate returned %d, inode = %lu, index = %lu, fpage = %d, xpage = %d, avail_in = %d, avail_out = %d, ai = %d, ao = %d\n",
 263                                                        zerr, inode->i_ino, index,
 264                                                        fpage, xpage,
 265                                                        stream.avail_in, stream.avail_out,
 266                                                        ai, ao);
 267                                         bail = 1;
 268                                         break;
 269                                 }
 270                         }
 271
 272                         if ( stream.avail_out && zerr == Z_STREAM_END ) {
 273                                 /* Fractional page written before EOF.  This may
 274                                    be the last page in the file. */
 275                                 memset(stream.next_out, 0, stream.avail_out);
 276                                 stream.avail_out = 0;
 277                         }
 278
 279                         if ( !stream.avail_out ) {
 280                                 /* This page completed */
 281                                 if ( page ) {
 282                                         flush_dcache_page(page);
 283                                         SetPageUptodate(page);
 284                                         kunmap(page);
 285                                         unlock_page(page);
 286                                         if ( fpage == xpage )
 287                                                 err = 0; /* The critical page */
 288                                         else
 289                                                 page_cache_release(page);
 290                                 }
 291                                 fpage++;
 292                         }
 293                 }
 294                 zlib_inflateEnd(&stream);
 295
 296         z_eio:
 297                 up(&zisofs_zlib_semaphore);
 298
 299         b_eio:
 300                 for ( i = 0 ; i < haveblocks ; i++ ) {
 301                         if ( bhs[i] )
 302                                 brelse(bhs[i]);
 303                 }
 304         }
 305
 306 eio:
 307
 308         /* Release any residual pages, do not SetPageUptodate */
 309         while ( fpage < maxpage ) {
 310                 page = pages[fpage];
 311                 if ( page ) {
 312                         flush_dcache_page(page);
 313                         if ( fpage == xpage )
 314                                 SetPageError(page);
 315                         kunmap(page);
 316                         unlock_page(page);
 317                         if ( fpage != xpage )
 318                                 page_cache_release(page);
 319                 }
 320                 fpage++;
 321         }
 322
 323         /* At this point, err contains 0 or -EIO depending on the "critical" page */
 324         return err;
 325 }
 326
 327 struct address_space_operations zisofs_aops = {
 328         .readpage = zisofs_readpage,
 329         /* No sync_page operation supported? */
 330         /* No bmap operation supported */
 331 };
 332
 333 static int initialized;
 334
 335 int __init zisofs_init(void)
 336 {
 337         if ( initialized ) {
 338                 printk("zisofs_init: called more than once\n");
 339                 return 0;
 340         }
 341
 342         zisofs_zlib_workspace = vmalloc(zlib_inflate_workspacesize());
 343         if ( !zisofs_zlib_workspace )
 344                 return -ENOMEM;
 345         init_MUTEX(&zisofs_zlib_semaphore);
 346
 347         initialized = 1;
 348         return 0;
 349 }
 350
 351 void zisofs_cleanup(void)
 352 {
 353         if ( !initialized ) {
 354                 printk("zisofs_cleanup: called without initialization\n");
 355                 return;
 356         }
 357
 358         vfree(zisofs_zlib_workspace);
 359         initialized = 0;
 360 }