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 #include <linux/bio.h>
  22
  23 #include <linux/slab.h>
  24 #include <linux/vmalloc.h>
  25 #include <linux/zlib.h>
  26
  27 #include "isofs.h"
  28 #include "zisofs.h"
  29
  30 /* This should probably be global. */
  31 static char zisofs_sink_page[PAGE_SIZE];
  32
  33 /*
  34  * This contains the zlib memory allocation and the mutex for the
  35  * allocation; this avoids failures at block-decompression time.
  36  */
  37 static void *zisofs_zlib_workspace;
  38 static DEFINE_MUTEX(zisofs_zlib_lock);
  39
  40 /*
  41  * Read data of @inode from @block_start to @block_end and uncompress
  42  * to one zisofs block. Store the data in the @pages array with @pcount
  43  * entries. Start storing at offset @poffset of the first page.
  44  */
  45 static loff_t zisofs_uncompress_block(struct inode *inode, loff_t block_start,
  46                                       loff_t block_end, int pcount,
  47                                       struct page **pages, unsigned poffset,
  48                                       int *errp)
  49 {
  50         unsigned int zisofs_block_shift = ISOFS_I(inode)->i_format_parm[1];
  51         unsigned int bufsize = ISOFS_BUFFER_SIZE(inode);
  52         unsigned int bufshift = ISOFS_BUFFER_BITS(inode);
  53         unsigned int bufmask = bufsize - 1;
  54         int i, block_size = block_end - block_start;
  55         z_stream stream = { .total_out = 0,
  56                             .avail_in = 0,
  57                             .avail_out = 0, };
  58         int zerr;
  59         int needblocks = (block_size + (block_start & bufmask) + bufmask)
  60                                 >> bufshift;
  61         int haveblocks;
  62         blkcnt_t blocknum;
  63         struct buffer_head **bhs;
  64         int curbh, curpage;
  65
  66         if (block_size > deflateBound(1UL << zisofs_block_shift)) {
  67                 *errp = -EIO;
  68                 return 0;
  69         }
  70         /* Empty block? */
  71         if (block_size == 0) {
  72                 for ( i = 0 ; i < pcount ; i++ ) {
  73                         if (!pages[i])
  74                                 continue;
  75                         memset(page_address(pages[i]), 0, PAGE_SIZE);
  76                         flush_dcache_page(pages[i]);
  77                         SetPageUptodate(pages[i]);
  78                 }
  79                 return ((loff_t)pcount) << PAGE_SHIFT;
  80         }
  81
  82         /* Because zlib is not thread-safe, do all the I/O at the top. */
  83         blocknum = block_start >> bufshift;
  84         bhs = kcalloc(needblocks + 1, sizeof(*bhs), GFP_KERNEL);
  85         if (!bhs) {
  86                 *errp = -ENOMEM;
  87                 return 0;
  88         }
  89         haveblocks = isofs_get_blocks(inode, blocknum, bhs, needblocks);
  90         ll_rw_block(REQ_OP_READ, 0, haveblocks, bhs);
  91
  92         curbh = 0;
  93         curpage = 0;
  94         /*
  95          * First block is special since it may be fractional.  We also wait for
  96          * it before grabbing the zlib mutex; odds are that the subsequent
  97          * blocks are going to come in in short order so we don't hold the zlib
  98          * mutex longer than necessary.
  99          */
 100
 101         if (!bhs[0])
 102                 goto b_eio;
 103
 104         wait_on_buffer(bhs[0]);
 105         if (!buffer_uptodate(bhs[0])) {
 106                 *errp = -EIO;
 107                 goto b_eio;
 108         }
 109
 110         stream.workspace = zisofs_zlib_workspace;
 111         mutex_lock(&zisofs_zlib_lock);
 112
 113         zerr = zlib_inflateInit(&stream);
 114         if (zerr != Z_OK) {
 115                 if (zerr == Z_MEM_ERROR)
 116                         *errp = -ENOMEM;
 117                 else
 118                         *errp = -EIO;
 119                 printk(KERN_DEBUG "zisofs: zisofs_inflateInit returned %d\n",
 120                                zerr);
 121                 goto z_eio;
 122         }
 123
 124         while (curpage < pcount && curbh < haveblocks &&
 125                zerr != Z_STREAM_END) {
 126                 if (!stream.avail_out) {
 127                         if (pages[curpage]) {
 128                                 stream.next_out = page_address(pages[curpage])
 129                                                 + poffset;
 130                                 stream.avail_out = PAGE_SIZE - poffset;
 131                                 poffset = 0;
 132                         } else {
 133                                 stream.next_out = (void *)&zisofs_sink_page;
 134                                 stream.avail_out = PAGE_SIZE;
 135                         }
 136                 }
 137                 if (!stream.avail_in) {
 138                         wait_on_buffer(bhs[curbh]);
 139                         if (!buffer_uptodate(bhs[curbh])) {
 140                                 *errp = -EIO;
 141                                 break;
 142                         }
 143                         stream.next_in  = bhs[curbh]->b_data +
 144                                                 (block_start & bufmask);
 145                         stream.avail_in = min_t(unsigned, bufsize -
 146                                                 (block_start & bufmask),
 147                                                 block_size);
 148                         block_size -= stream.avail_in;
 149                         block_start = 0;
 150                 }
 151
 152                 while (stream.avail_out && stream.avail_in) {
 153                         zerr = zlib_inflate(&stream, Z_SYNC_FLUSH);
 154                         if (zerr == Z_BUF_ERROR && stream.avail_in == 0)
 155                                 break;
 156                         if (zerr == Z_STREAM_END)
 157                                 break;
 158                         if (zerr != Z_OK) {
 159                                 /* EOF, error, or trying to read beyond end of input */
 160                                 if (zerr == Z_MEM_ERROR)
 161                                         *errp = -ENOMEM;
 162                                 else {
 163                                         printk(KERN_DEBUG
 164                                                "zisofs: zisofs_inflate returned"
 165                                                " %d, inode = %lu,"
 166                                                " page idx = %d, bh idx = %d,"
 167                                                " avail_in = %ld,"
 168                                                " avail_out = %ld\n",
 169                                                zerr, inode->i_ino, curpage,
 170                                                curbh, stream.avail_in,
 171                                                stream.avail_out);
 172                                         *errp = -EIO;
 173                                 }
 174                                 goto inflate_out;
 175                         }
 176                 }
 177
 178                 if (!stream.avail_out) {
 179                         /* This page completed */
 180                         if (pages[curpage]) {
 181                                 flush_dcache_page(pages[curpage]);
 182                                 SetPageUptodate(pages[curpage]);
 183                         }
 184                         curpage++;
 185                 }
 186                 if (!stream.avail_in)
 187                         curbh++;
 188         }
 189 inflate_out:
 190         zlib_inflateEnd(&stream);
 191
 192 z_eio:
 193         mutex_unlock(&zisofs_zlib_lock);
 194
 195 b_eio:
 196         for (i = 0; i < haveblocks; i++)
 197                 brelse(bhs[i]);
 198         kfree(bhs);
 199         return stream.total_out;
 200 }
 201
 202 /*
 203  * Uncompress data so that pages[full_page] is fully uptodate and possibly
 204  * fills in other pages if we have data for them.
 205  */
 206 static int zisofs_fill_pages(struct inode *inode, int full_page, int pcount,
 207                              struct page **pages)
 208 {
 209         loff_t start_off, end_off;
 210         loff_t block_start, block_end;
 211         unsigned int header_size = ISOFS_I(inode)->i_format_parm[0];
 212         unsigned int zisofs_block_shift = ISOFS_I(inode)->i_format_parm[1];
 213         unsigned int blockptr;
 214         loff_t poffset = 0;
 215         blkcnt_t cstart_block, cend_block;
 216         struct buffer_head *bh;
 217         unsigned int blkbits = ISOFS_BUFFER_BITS(inode);
 218         unsigned int blksize = 1 << blkbits;
 219         int err;
 220         loff_t ret;
 221
 222         BUG_ON(!pages[full_page]);
 223
 224         /*
 225          * We want to read at least 'full_page' page. Because we have to
 226          * uncompress the whole compression block anyway, fill the surrounding
 227          * pages with the data we have anyway...
 228          */
 229         start_off = page_offset(pages[full_page]);
 230         end_off = min_t(loff_t, start_off + PAGE_SIZE, inode->i_size);
 231
 232         cstart_block = start_off >> zisofs_block_shift;
 233         cend_block = (end_off + (1 << zisofs_block_shift) - 1)
 234                         >> zisofs_block_shift;
 235
 236         WARN_ON(start_off - (full_page << PAGE_SHIFT) !=
 237                 ((cstart_block << zisofs_block_shift) & PAGE_MASK));
 238
 239         /* Find the pointer to this specific chunk */
 240         /* Note: we're not using isonum_731() here because the data is known aligned */
 241         /* Note: header_size is in 32-bit words (4 bytes) */
 242         blockptr = (header_size + cstart_block) << 2;
 243         bh = isofs_bread(inode, blockptr >> blkbits);
 244         if (!bh)
 245                 return -EIO;
 246         block_start = le32_to_cpu(*(__le32 *)
 247                                 (bh->b_data + (blockptr & (blksize - 1))));
 248
 249         while (cstart_block < cend_block && pcount > 0) {
 250                 /* Load end of the compressed block in the file */
 251                 blockptr += 4;
 252                 /* Traversed to next block? */
 253                 if (!(blockptr & (blksize - 1))) {
 254                         brelse(bh);
 255
 256                         bh = isofs_bread(inode, blockptr >> blkbits);
 257                         if (!bh)
 258                                 return -EIO;
 259                 }
 260                 block_end = le32_to_cpu(*(__le32 *)
 261                                 (bh->b_data + (blockptr & (blksize - 1))));
 262                 if (block_start > block_end) {
 263                         brelse(bh);
 264                         return -EIO;
 265                 }
 266                 err = 0;
 267                 ret = zisofs_uncompress_block(inode, block_start, block_end,
 268                                               pcount, pages, poffset, &err);
 269                 poffset += ret;
 270                 pages += poffset >> PAGE_SHIFT;
 271                 pcount -= poffset >> PAGE_SHIFT;
 272                 full_page -= poffset >> PAGE_SHIFT;
 273                 poffset &= ~PAGE_MASK;
 274
 275                 if (err) {
 276                         brelse(bh);
 277                         /*
 278                          * Did we finish reading the page we really wanted
 279                          * to read?
 280                          */
 281                         if (full_page < 0)
 282                                 return 0;
 283                         return err;
 284                 }
 285
 286                 block_start = block_end;
 287                 cstart_block++;
 288         }
 289
 290         if (poffset && *pages) {
 291                 memset(page_address(*pages) + poffset, 0,
 292                        PAGE_SIZE - poffset);
 293                 flush_dcache_page(*pages);
 294                 SetPageUptodate(*pages);
 295         }
 296         return 0;
 297 }
 298
 299 /*
 300  * When decompressing, we typically obtain more than one page
 301  * per reference.  We inject the additional pages into the page
 302  * cache as a form of readahead.
 303  */
 304 static int zisofs_readpage(struct file *file, struct page *page)
 305 {
 306         struct inode *inode = file_inode(file);
 307         struct address_space *mapping = inode->i_mapping;
 308         int err;
 309         int i, pcount, full_page;
 310         unsigned int zisofs_block_shift = ISOFS_I(inode)->i_format_parm[1];
 311         unsigned int zisofs_pages_per_cblock =
 312                 PAGE_SHIFT <= zisofs_block_shift ?
 313                 (1 << (zisofs_block_shift - PAGE_SHIFT)) : 0;
 314         struct page **pages;
 315         pgoff_t index = page->index, end_index;
 316
 317         end_index = (inode->i_size + PAGE_SIZE - 1) >> PAGE_SHIFT;
 318         /*
 319          * If this page is wholly outside i_size we just return zero;
 320          * do_generic_file_read() will handle this for us
 321          */
 322         if (index >= end_index) {
 323                 SetPageUptodate(page);
 324                 unlock_page(page);
 325                 return 0;
 326         }
 327
 328         if (PAGE_SHIFT <= zisofs_block_shift) {
 329                 /* We have already been given one page, this is the one
 330                    we must do. */
 331                 full_page = index & (zisofs_pages_per_cblock - 1);
 332                 pcount = min_t(int, zisofs_pages_per_cblock,
 333                         end_index - (index & ~(zisofs_pages_per_cblock - 1)));
 334                 index -= full_page;
 335         } else {
 336                 full_page = 0;
 337                 pcount = 1;
 338         }
 339         pages = kcalloc(max_t(unsigned int, zisofs_pages_per_cblock, 1),
 340                                         sizeof(*pages), GFP_KERNEL);
 341         if (!pages) {
 342                 unlock_page(page);
 343                 return -ENOMEM;
 344         }
 345         pages[full_page] = page;
 346
 347         for (i = 0; i < pcount; i++, index++) {
 348                 if (i != full_page)
 349                         pages[i] = grab_cache_page_nowait(mapping, index);
 350                 if (pages[i]) {
 351                         ClearPageError(pages[i]);
 352                         kmap(pages[i]);
 353                 }
 354         }
 355
 356         err = zisofs_fill_pages(inode, full_page, pcount, pages);
 357
 358         /* Release any residual pages, do not SetPageUptodate */
 359         for (i = 0; i < pcount; i++) {
 360                 if (pages[i]) {
 361                         flush_dcache_page(pages[i]);
 362                         if (i == full_page && err)
 363                                 SetPageError(pages[i]);
 364                         kunmap(pages[i]);
 365                         unlock_page(pages[i]);
 366                         if (i != full_page)
 367                                 put_page(pages[i]);
 368                 }
 369         }
 370
 371         /* At this point, err contains 0 or -EIO depending on the "critical" page */
 372         kfree(pages);
 373         return err;
 374 }
 375
 376 const struct address_space_operations zisofs_aops = {
 377         .readpage = zisofs_readpage,
 378         /* No bmap operation supported */
 379 };
 380
 381 int __init zisofs_init(void)
 382 {
 383         zisofs_zlib_workspace = vmalloc(zlib_inflate_workspacesize());
 384         if ( !zisofs_zlib_workspace )
 385                 return -ENOMEM;
 386
 387         return 0;
 388 }
 389
 390 void zisofs_cleanup(void)
 391 {
 392         vfree(zisofs_zlib_workspace);
 393 }