linux/fs/isofs/compress.c
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   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. */
  29static 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 */
  35static void *zisofs_zlib_workspace;
  36static 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 */
  43static 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        }
 183inflate_out:
 184        zlib_inflateEnd(&stream);
 185
 186z_eio:
 187        mutex_unlock(&zisofs_zlib_lock);
 188
 189b_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 */
 199static 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 */
 297static 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
 362const struct address_space_operations zisofs_aops = {
 363        .readpage = zisofs_readpage,
 364        /* No sync_page operation supported? */
 365        /* No bmap operation supported */
 366};
 367
 368int __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
 377void zisofs_cleanup(void)
 378{
 379        vfree(zisofs_zlib_workspace);
 380}
 381
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