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 #include <linux/init.h>
  22
  23 #include <linux/vmalloc.h>
  24 #include <linux/zlib.h>
  25
  26 #include "isofs.h"
  27 #include "zisofs.h"
  28
  29 /* This should probably be global. */
  30 static char zisofs_sink_page[PAGE_CACHE_SIZE];
  31
  32 /*
  33  * This contains the zlib memory allocation and the mutex for the
  34  * allocation; this avoids failures at block-decompression time.
  35  */
  36 static void *zisofs_zlib_workspace;
  37 static struct semaphore zisofs_zlib_semaphore;
  38
  39 /*
  40  * When decompressing, we typically obtain more than one page
  41  * per reference.  We inject the additional pages into the page
  42  * cache as a form of readahead.
  43  */
  44 static int zisofs_readpage(struct file *file, struct page *page)
  45 {
  46         struct inode *inode = file->f_dentry->d_inode;
  47         struct address_space *mapping = inode->i_mapping;
  48         unsigned int maxpage, xpage, fpage, blockindex;
  49         unsigned long offset;
  50         unsigned long blockptr, blockendptr, cstart, cend, csize;
  51         struct buffer_head *bh, *ptrbh[2];
  52         unsigned long bufsize = ISOFS_BUFFER_SIZE(inode);
  53         unsigned int bufshift = ISOFS_BUFFER_BITS(inode);
  54         unsigned long bufmask  = bufsize - 1;
  55         int err = -EIO;
  56         int i;
  57         unsigned int header_size = ISOFS_I(inode)->i_format_parm[0];
  58         unsigned int zisofs_block_shift = ISOFS_I(inode)->i_format_parm[1];
  59         /* unsigned long zisofs_block_size = 1UL << zisofs_block_shift; */
  60         unsigned int zisofs_block_page_shift = zisofs_block_shift-PAGE_CACHE_SHIFT;
  61         unsigned long zisofs_block_pages = 1UL << zisofs_block_page_shift;
  62         unsigned long zisofs_block_page_mask = zisofs_block_pages-1;
  63         struct page *pages[zisofs_block_pages];
  64         unsigned long index = page->index;
  65         int indexblocks;
  66
  67         /* We have already been given one page, this is the one
  68            we must do. */
  69         xpage = index & zisofs_block_page_mask;
  70         pages[xpage] = page;
  71
  72         /* The remaining pages need to be allocated and inserted */
  73         offset = index & ~zisofs_block_page_mask;
  74         blockindex = offset >> zisofs_block_page_shift;
  75         maxpage = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
  76         maxpage = min(zisofs_block_pages, maxpage-offset);
  77
  78         for ( i = 0 ; i < maxpage ; i++, offset++ ) {
  79                 if ( i != xpage ) {
  80                         pages[i] = grab_cache_page_nowait(mapping, offset);
  81                 }
  82                 page = pages[i];
  83                 if ( page ) {
  84                         ClearPageError(page);
  85                         kmap(page);
  86                 }
  87         }
  88
  89         /* This is the last page filled, plus one; used in case of abort. */
  90         fpage = 0;
  91
  92         /* Find the pointer to this specific chunk */
  93         /* Note: we're not using isonum_731() here because the data is known aligned */
  94         /* Note: header_size is in 32-bit words (4 bytes) */
  95         blockptr = (header_size + blockindex) << 2;
  96         blockendptr = blockptr + 4;
  97
  98         indexblocks = ((blockptr^blockendptr) >> bufshift) ? 2 : 1;
  99         ptrbh[0] = ptrbh[1] = NULL;
 100
 101         if ( isofs_get_blocks(inode, blockptr >> bufshift, ptrbh, indexblocks) != indexblocks ) {
 102                 if ( ptrbh[0] ) brelse(ptrbh[0]);
 103                 printk(KERN_DEBUG "zisofs: Null buffer on reading block table, inode = %lu, block = %lu\n",
 104                        inode->i_ino, blockptr >> bufshift);
 105                 goto eio;
 106         }
 107         ll_rw_block(READ, indexblocks, ptrbh);
 108
 109         bh = ptrbh[0];
 110         if ( !bh || (wait_on_buffer(bh), !buffer_uptodate(bh)) ) {
 111                 printk(KERN_DEBUG "zisofs: Failed to read block table, inode = %lu, block = %lu\n",
 112                        inode->i_ino, blockptr >> bufshift);
 113                 if ( ptrbh[1] )
 114                         brelse(ptrbh[1]);
 115                 goto eio;
 116         }
 117         cstart = le32_to_cpu(*(__le32 *)(bh->b_data + (blockptr & bufmask)));
 118
 119         if ( indexblocks == 2 ) {
 120                 /* We just crossed a block boundary.  Switch to the next block */
 121                 brelse(bh);
 122                 bh = ptrbh[1];
 123                 if ( !bh || (wait_on_buffer(bh), !buffer_uptodate(bh)) ) {
 124                         printk(KERN_DEBUG "zisofs: Failed to read block table, inode = %lu, block = %lu\n",
 125                                inode->i_ino, blockendptr >> bufshift);
 126                         goto eio;
 127                 }
 128         }
 129         cend = le32_to_cpu(*(__le32 *)(bh->b_data + (blockendptr & bufmask)));
 130         brelse(bh);
 131
 132         if (cstart > cend)
 133                 goto eio;
 134
 135         csize = cend-cstart;
 136
 137         if (csize > deflateBound(1UL << zisofs_block_shift))
 138                 goto eio;
 139
 140         /* Now page[] contains an array of pages, any of which can be NULL,
 141            and the locks on which we hold.  We should now read the data and
 142            release the pages.  If the pages are NULL the decompressed data
 143            for that particular page should be discarded. */
 144
 145         if ( csize == 0 ) {
 146                 /* This data block is empty. */
 147
 148                 for ( fpage = 0 ; fpage < maxpage ; fpage++ ) {
 149                         if ( (page = pages[fpage]) != NULL ) {
 150                                 memset(page_address(page), 0, PAGE_CACHE_SIZE);
 151
 152                                 flush_dcache_page(page);
 153                                 SetPageUptodate(page);
 154                                 kunmap(page);
 155                                 unlock_page(page);
 156                                 if ( fpage == xpage )
 157                                         err = 0; /* The critical page */
 158                                 else
 159                                         page_cache_release(page);
 160                         }
 161                 }
 162         } else {
 163                 /* This data block is compressed. */
 164                 z_stream stream;
 165                 int bail = 0, left_out = -1;
 166                 int zerr;
 167                 int needblocks = (csize + (cstart & bufmask) + bufmask) >> bufshift;
 168                 int haveblocks;
 169                 struct buffer_head *bhs[needblocks+1];
 170                 struct buffer_head **bhptr;
 171
 172                 /* Because zlib is not thread-safe, do all the I/O at the top. */
 173
 174                 blockptr = cstart >> bufshift;
 175                 memset(bhs, 0, (needblocks+1)*sizeof(struct buffer_head *));
 176                 haveblocks = isofs_get_blocks(inode, blockptr, bhs, needblocks);
 177                 ll_rw_block(READ, haveblocks, bhs);
 178
 179                 bhptr = &bhs[0];
 180                 bh = *bhptr++;
 181
 182                 /* First block is special since it may be fractional.
 183                    We also wait for it before grabbing the zlib
 184                    semaphore; odds are that the subsequent blocks are
 185                    going to come in in short order so we don't hold
 186                    the zlib semaphore longer than necessary. */
 187
 188                 if ( !bh || (wait_on_buffer(bh), !buffer_uptodate(bh)) ) {
 189                         printk(KERN_DEBUG "zisofs: Hit null buffer, fpage = %d, xpage = %d, csize = %ld\n",
 190                                fpage, xpage, csize);
 191                         goto b_eio;
 192                 }
 193                 stream.next_in  = bh->b_data + (cstart & bufmask);
 194                 stream.avail_in = min(bufsize-(cstart & bufmask), csize);
 195                 csize -= stream.avail_in;
 196
 197                 stream.workspace = zisofs_zlib_workspace;
 198                 down(&zisofs_zlib_semaphore);
 199
 200                 zerr = zlib_inflateInit(&stream);
 201                 if ( zerr != Z_OK ) {
 202                         if ( err && zerr == Z_MEM_ERROR )
 203                                 err = -ENOMEM;
 204                         printk(KERN_DEBUG "zisofs: zisofs_inflateInit returned %d\n",
 205                                zerr);
 206                         goto z_eio;
 207                 }
 208
 209                 while ( !bail && fpage < maxpage ) {
 210                         page = pages[fpage];
 211                         if ( page )
 212                                 stream.next_out = page_address(page);
 213                         else
 214                                 stream.next_out = (void *)&zisofs_sink_page;
 215                         stream.avail_out = PAGE_CACHE_SIZE;
 216
 217                         while ( stream.avail_out ) {
 218                                 int ao, ai;
 219                                 if ( stream.avail_in == 0 && left_out ) {
 220                                         if ( !csize ) {
 221                                                 printk(KERN_WARNING "zisofs: ZF read beyond end of input\n");
 222                                                 bail = 1;
 223                                                 break;
 224                                         } else {
 225                                                 bh = *bhptr++;
 226                                                 if ( !bh ||
 227                                                      (wait_on_buffer(bh), !buffer_uptodate(bh)) ) {
 228                                                         /* Reached an EIO */
 229                                                         printk(KERN_DEBUG "zisofs: Hit null buffer, fpage = %d, xpage = %d, csize = %ld\n",
 230                                                                fpage, xpage, csize);
 231
 232                                                         bail = 1;
 233                                                         break;
 234                                                 }
 235                                                 stream.next_in = bh->b_data;
 236                                                 stream.avail_in = min(csize,bufsize);
 237                                                 csize -= stream.avail_in;
 238                                         }
 239                                 }
 240                                 ao = stream.avail_out;  ai = stream.avail_in;
 241                                 zerr = zlib_inflate(&stream, Z_SYNC_FLUSH);
 242                                 left_out = stream.avail_out;
 243                                 if ( zerr == Z_BUF_ERROR && stream.avail_in == 0 )
 244                                         continue;
 245                                 if ( zerr != Z_OK ) {
 246                                         /* EOF, error, or trying to read beyond end of input */
 247                                         if ( err && zerr == Z_MEM_ERROR )
 248                                                 err = -ENOMEM;
 249                                         if ( zerr != Z_STREAM_END )
 250                                                 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",
 251                                                        zerr, inode->i_ino, index,
 252                                                        fpage, xpage,
 253                                                        stream.avail_in, stream.avail_out,
 254                                                        ai, ao);
 255                                         bail = 1;
 256                                         break;
 257                                 }
 258                         }
 259
 260                         if ( stream.avail_out && zerr == Z_STREAM_END ) {
 261                                 /* Fractional page written before EOF.  This may
 262                                    be the last page in the file. */
 263                                 memset(stream.next_out, 0, stream.avail_out);
 264                                 stream.avail_out = 0;
 265                         }
 266
 267                         if ( !stream.avail_out ) {
 268                                 /* This page completed */
 269                                 if ( page ) {
 270                                         flush_dcache_page(page);
 271                                         SetPageUptodate(page);
 272                                         kunmap(page);
 273                                         unlock_page(page);
 274                                         if ( fpage == xpage )
 275                                                 err = 0; /* The critical page */
 276                                         else
 277                                                 page_cache_release(page);
 278                                 }
 279                                 fpage++;
 280                         }
 281                 }
 282                 zlib_inflateEnd(&stream);
 283
 284         z_eio:
 285                 up(&zisofs_zlib_semaphore);
 286
 287         b_eio:
 288                 for ( i = 0 ; i < haveblocks ; i++ ) {
 289                         if ( bhs[i] )
 290                                 brelse(bhs[i]);
 291                 }
 292         }
 293
 294 eio:
 295
 296         /* Release any residual pages, do not SetPageUptodate */
 297         while ( fpage < maxpage ) {
 298                 page = pages[fpage];
 299                 if ( page ) {
 300                         flush_dcache_page(page);
 301                         if ( fpage == xpage )
 302                                 SetPageError(page);
 303                         kunmap(page);
 304                         unlock_page(page);
 305                         if ( fpage != xpage )
 306                                 page_cache_release(page);
 307                 }
 308                 fpage++;
 309         }
 310
 311         /* At this point, err contains 0 or -EIO depending on the "critical" page */
 312         return err;
 313 }
 314
 315 struct address_space_operations zisofs_aops = {
 316         .readpage = zisofs_readpage,
 317         /* No sync_page operation supported? */
 318         /* No bmap operation supported */
 319 };
 320
 321 static int initialized;
 322
 323 int __init zisofs_init(void)
 324 {
 325         if ( initialized ) {
 326                 printk("zisofs_init: called more than once\n");
 327                 return 0;
 328         }
 329
 330         zisofs_zlib_workspace = vmalloc(zlib_inflate_workspacesize());
 331         if ( !zisofs_zlib_workspace )
 332                 return -ENOMEM;
 333         init_MUTEX(&zisofs_zlib_semaphore);
 334
 335         initialized = 1;
 336         return 0;
 337 }
 338
 339 void zisofs_cleanup(void)
 340 {
 341         if ( !initialized ) {
 342                 printk("zisofs_cleanup: called without initialization\n");
 343                 return;
 344         }
 345
 346         vfree(zisofs_zlib_workspace);
 347         initialized = 0;
 348 }