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