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/module.h>
  20 #include <linux/init.h>
  21
  22 #include <linux/vmalloc.h>
  23 #include <linux/zlib.h>
  24
  25 #include "isofs.h"
  26 #include "zisofs.h"
  27
  28 /* This should probably be global. */
  29 static char zisofs_sink_page[PAGE_CACHE_SIZE];
  30
  31 /*
  32  * This contains the zlib memory allocation and the mutex for the
  33  * allocation; this avoids failures at block-decompression time.
  34  */
  35 static void *zisofs_zlib_workspace;
  36 static DEFINE_MUTEX(zisofs_zlib_lock);
  37
  38 /*
  39  * Read data of @inode from @block_start to @block_end and uncompress
  40  * to one zisofs block. Store the data in the @pages array with @pcount
  41  * entries. Start storing at offset @poffset of the first page.
  42  */
  43 static loff_t zisofs_uncompress_block(struct inode *inode, loff_t block_start,
  44                                       loff_t block_end, int pcount,
  45                                       struct page **pages, unsigned poffset,
  46                                       int *errp)
  47 {
  48         unsigned int zisofs_block_shift = ISOFS_I(inode)->i_format_parm[1];
  49         unsigned int bufsize = ISOFS_BUFFER_SIZE(inode);
  50         unsigned int bufshift = ISOFS_BUFFER_BITS(inode);
  51         unsigned int bufmask = bufsize - 1;
  52         int i, block_size = block_end - block_start;
  53         z_stream stream = { .total_out = 0,
  54                             .avail_in = 0,
  55                             .avail_out = 0, };
  56         int zerr;
  57         int needblocks = (block_size + (block_start & bufmask) + bufmask)
  58                                 >> bufshift;
  59         int haveblocks;
  60         blkcnt_t blocknum;
  61         struct buffer_head *bhs[needblocks + 1];
  62         int curbh, curpage;
  63
  64         if (block_size > deflateBound(1UL << zisofs_block_shift)) {
  65                 *errp = -EIO;
  66                 return 0;
  67         }
  68         /* Empty block? */
  69         if (block_size == 0) {
  70                 for ( i = 0 ; i < pcount ; i++ ) {
  71                         if (!pages[i])
  72                                 continue;
  73                         memset(page_address(pages[i]), 0, PAGE_CACHE_SIZE);
  74                         flush_dcache_page(pages[i]);
  75                         SetPageUptodate(pages[i]);
  76                 }
  77                 return ((loff_t)pcount) << PAGE_CACHE_SHIFT;
  78         }
  79
  80         /* Because zlib is not thread-safe, do all the I/O at the top. */
  81         blocknum = block_start >> bufshift;
  82         memset(bhs, 0, (needblocks + 1) * sizeof(struct buffer_head *));
  83         haveblocks = isofs_get_blocks(inode, blocknum, bhs, needblocks);
  84         ll_rw_block(READ, haveblocks, bhs);
  85
  86         curbh = 0;
  87         curpage = 0;
  88         /*
  89          * First block is special since it may be fractional.  We also wait for
  90          * it before grabbing the zlib mutex; odds are that the subsequent
  91          * blocks are going to come in in short order so we don't hold the zlib
  92          * mutex longer than necessary.
  93          */
  94
  95         if (!bhs[0])
  96                 goto b_eio;
  97
  98         wait_on_buffer(bhs[0]);
  99         if (!buffer_uptodate(bhs[0])) {
 100                 *errp = -EIO;
 101                 goto b_eio;
 102         }
 103
 104         stream.workspace = zisofs_zlib_workspace;
 105         mutex_lock(&zisofs_zlib_lock);
 106
 107         zerr = zlib_inflateInit(&stream);
 108         if (zerr != Z_OK) {
 109                 if (zerr == Z_MEM_ERROR)
 110                         *errp = -ENOMEM;
 111                 else
 112                         *errp = -EIO;
 113                 printk(KERN_DEBUG "zisofs: zisofs_inflateInit returned %d\n",
 114                                zerr);
 115                 goto z_eio;
 116         }
 117
 118         while (curpage < pcount && curbh < haveblocks &&
 119                zerr != Z_STREAM_END) {
 120                 if (!stream.avail_out) {
 121                         if (pages[curpage]) {
 122                                 stream.next_out = page_address(pages[curpage])
 123                                                 + poffset;
 124                                 stream.avail_out = PAGE_CACHE_SIZE - poffset;
 125                                 poffset = 0;
 126                         } else {
 127                                 stream.next_out = (void *)&zisofs_sink_page;
 128                                 stream.avail_out = PAGE_CACHE_SIZE;
 129                         }
 130                 }
 131                 if (!stream.avail_in) {
 132                         wait_on_buffer(bhs[curbh]);
 133                         if (!buffer_uptodate(bhs[curbh])) {
 134                                 *errp = -EIO;
 135                                 break;
 136                         }
 137                         stream.next_in  = bhs[curbh]->b_data +
 138                                                 (block_start & bufmask);
 139                         stream.avail_in = min_t(unsigned, bufsize -
 140                                                 (block_start & bufmask),
 141                                                 block_size);
 142                         block_size -= stream.avail_in;
 143                         block_start = 0;
 144                 }
 145
 146                 while (stream.avail_out && stream.avail_in) {
 147                         zerr = zlib_inflate(&stream, Z_SYNC_FLUSH);
 148                         if (zerr == Z_BUF_ERROR && stream.avail_in == 0)
 149                                 break;
 150                         if (zerr == Z_STREAM_END)
 151                                 break;
 152                         if (zerr != Z_OK) {
 153                                 /* EOF, error, or trying to read beyond end of input */
 154                                 if (zerr == Z_MEM_ERROR)
 155                                         *errp = -ENOMEM;
 156                                 else {
 157                                         printk(KERN_DEBUG
 158                                                "zisofs: zisofs_inflate returned"
 159                                                " %d, inode = %lu,"
 160                                                " page idx = %d, bh idx = %d,"
 161                                                " avail_in = %d,"
 162                                                " avail_out = %d\n",
 163                                                zerr, inode->i_ino, curpage,
 164                                                curbh, stream.avail_in,
 165                                                stream.avail_out);
 166                                         *errp = -EIO;
 167                                 }
 168                                 goto inflate_out;
 169                         }
 170                 }
 171
 172                 if (!stream.avail_out) {
 173                         /* This page completed */
 174                         if (pages[curpage]) {
 175                                 flush_dcache_page(pages[curpage]);
 176                                 SetPageUptodate(pages[curpage]);
 177                         }
 178                         curpage++;
 179                 }
 180                 if (!stream.avail_in)
 181                         curbh++;
 182         }
 183 inflate_out:
 184         zlib_inflateEnd(&stream);
 185
 186 z_eio:
 187         mutex_unlock(&zisofs_zlib_lock);
 188
 189 b_eio:
 190         for (i = 0; i < haveblocks; i++)
 191                 brelse(bhs[i]);
 192         return stream.total_out;
 193 }
 194
 195 /*
 196  * Uncompress data so that pages[full_page] is fully uptodate and possibly
 197  * fills in other pages if we have data for them.
 198  */
 199 static int zisofs_fill_pages(struct inode *inode, int full_page, int pcount,
 200                              struct page **pages)
 201 {
 202         loff_t start_off, end_off;
 203         loff_t block_start, block_end;
 204         unsigned int header_size = ISOFS_I(inode)->i_format_parm[0];
 205         unsigned int zisofs_block_shift = ISOFS_I(inode)->i_format_parm[1];
 206         unsigned int blockptr;
 207         loff_t poffset = 0;
 208         blkcnt_t cstart_block, cend_block;
 209         struct buffer_head *bh;
 210         unsigned int blkbits = ISOFS_BUFFER_BITS(inode);
 211         unsigned int blksize = 1 << blkbits;
 212         int err;
 213         loff_t ret;
 214
 215         BUG_ON(!pages[full_page]);
 216
 217         /*
 218          * We want to read at least 'full_page' page. Because we have to
 219          * uncompress the whole compression block anyway, fill the surrounding
 220          * pages with the data we have anyway...
 221          */
 222         start_off = page_offset(pages[full_page]);
 223         end_off = min_t(loff_t, start_off + PAGE_CACHE_SIZE, inode->i_size);
 224
 225         cstart_block = start_off >> zisofs_block_shift;
 226         cend_block = (end_off + (1 << zisofs_block_shift) - 1)
 227                         >> zisofs_block_shift;
 228
 229         WARN_ON(start_off - (full_page << PAGE_CACHE_SHIFT) !=
 230                 ((cstart_block << zisofs_block_shift) & PAGE_CACHE_MASK));
 231
 232         /* Find the pointer to this specific chunk */
 233         /* Note: we're not using isonum_731() here because the data is known aligned */
 234         /* Note: header_size is in 32-bit words (4 bytes) */
 235         blockptr = (header_size + cstart_block) << 2;
 236         bh = isofs_bread(inode, blockptr >> blkbits);
 237         if (!bh)
 238                 return -EIO;
 239         block_start = le32_to_cpu(*(__le32 *)
 240                                 (bh->b_data + (blockptr & (blksize - 1))));
 241
 242         while (cstart_block < cend_block && pcount > 0) {
 243                 /* Load end of the compressed block in the file */
 244                 blockptr += 4;
 245                 /* Traversed to next block? */
 246                 if (!(blockptr & (blksize - 1))) {
 247                         brelse(bh);
 248
 249                         bh = isofs_bread(inode, blockptr >> blkbits);
 250                         if (!bh)
 251                                 return -EIO;
 252                 }
 253                 block_end = le32_to_cpu(*(__le32 *)
 254                                 (bh->b_data + (blockptr & (blksize - 1))));
 255                 if (block_start > block_end) {
 256                         brelse(bh);
 257                         return -EIO;
 258                 }
 259                 err = 0;
 260                 ret = zisofs_uncompress_block(inode, block_start, block_end,
 261                                               pcount, pages, poffset, &err);
 262                 poffset += ret;
 263                 pages += poffset >> PAGE_CACHE_SHIFT;
 264                 pcount -= poffset >> PAGE_CACHE_SHIFT;
 265                 full_page -= poffset >> PAGE_CACHE_SHIFT;
 266                 poffset &= ~PAGE_CACHE_MASK;
 267
 268                 if (err) {
 269                         brelse(bh);
 270                         /*
 271                          * Did we finish reading the page we really wanted
 272                          * to read?
 273                          */
 274                         if (full_page < 0)
 275                                 return 0;
 276                         return err;
 277                 }
 278
 279                 block_start = block_end;
 280                 cstart_block++;
 281         }
 282
 283         if (poffset && *pages) {
 284                 memset(page_address(*pages) + poffset, 0,
 285                        PAGE_CACHE_SIZE - poffset);
 286                 flush_dcache_page(*pages);
 287                 SetPageUptodate(*pages);
 288         }
 289         return 0;
 290 }
 291
 292 /*
 293  * When decompressing, we typically obtain more than one page
 294  * per reference.  We inject the additional pages into the page
 295  * cache as a form of readahead.
 296  */
 297 static int zisofs_readpage(struct file *file, struct page *page)
 298 {
 299         struct inode *inode = file->f_path.dentry->d_inode;
 300         struct address_space *mapping = inode->i_mapping;
 301         int err;
 302         int i, pcount, full_page;
 303         unsigned int zisofs_block_shift = ISOFS_I(inode)->i_format_parm[1];
 304         unsigned int zisofs_pages_per_cblock =
 305                 PAGE_CACHE_SHIFT <= zisofs_block_shift ?
 306                 (1 << (zisofs_block_shift - PAGE_CACHE_SHIFT)) : 0;
 307         struct page *pages[max_t(unsigned, zisofs_pages_per_cblock, 1)];
 308         pgoff_t index = page->index, end_index;
 309
 310         end_index = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 311         /*
 312          * If this page is wholly outside i_size we just return zero;
 313          * do_generic_file_read() will handle this for us
 314          */
 315         if (index >= end_index) {
 316                 SetPageUptodate(page);
 317                 unlock_page(page);
 318                 return 0;
 319         }
 320
 321         if (PAGE_CACHE_SHIFT <= zisofs_block_shift) {
 322                 /* We have already been given one page, this is the one
 323                    we must do. */
 324                 full_page = index & (zisofs_pages_per_cblock - 1);
 325                 pcount = min_t(int, zisofs_pages_per_cblock,
 326                         end_index - (index & ~(zisofs_pages_per_cblock - 1)));
 327                 index -= full_page;
 328         } else {
 329                 full_page = 0;
 330                 pcount = 1;
 331         }
 332         pages[full_page] = page;
 333
 334         for (i = 0; i < pcount; i++, index++) {
 335                 if (i != full_page)
 336                         pages[i] = grab_cache_page_nowait(mapping, index);
 337                 if (pages[i]) {
 338                         ClearPageError(pages[i]);
 339                         kmap(pages[i]);
 340                 }
 341         }
 342
 343         err = zisofs_fill_pages(inode, full_page, pcount, pages);
 344
 345         /* Release any residual pages, do not SetPageUptodate */
 346         for (i = 0; i < pcount; i++) {
 347                 if (pages[i]) {
 348                         flush_dcache_page(pages[i]);
 349                         if (i == full_page && err)
 350                                 SetPageError(pages[i]);
 351                         kunmap(pages[i]);
 352                         unlock_page(pages[i]);
 353                         if (i != full_page)
 354                                 page_cache_release(pages[i]);
 355                 }
 356         }
 357
 358         /* At this point, err contains 0 or -EIO depending on the "critical" page */
 359         return err;
 360 }
 361
 362 const struct address_space_operations zisofs_aops = {
 363         .readpage = zisofs_readpage,
 364         /* No sync_page operation supported? */
 365         /* No bmap operation supported */
 366 };
 367
 368 int __init zisofs_init(void)
 369 {
 370         zisofs_zlib_workspace = vmalloc(zlib_inflate_workspacesize());
 371         if ( !zisofs_zlib_workspace )
 372                 return -ENOMEM;
 373
 374         return 0;
 375 }
 376
 377 void zisofs_cleanup(void)
 378 {
 379         vfree(zisofs_zlib_workspace);
 380 }