linux/fs/efs/inode.c
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   1/*
   2 * inode.c
   3 *
   4 * Copyright (c) 1999 Al Smith
   5 *
   6 * Portions derived from work (c) 1995,1996 Christian Vogelgsang,
   7 *              and from work (c) 1998 Mike Shaver.
   8 */
   9
  10#include <linux/buffer_head.h>
  11#include <linux/module.h>
  12#include <linux/fs.h>
  13#include "efs.h"
  14#include <linux/efs_fs_sb.h>
  15
  16static int efs_readpage(struct file *file, struct page *page)
  17{
  18        return block_read_full_page(page,efs_get_block);
  19}
  20static sector_t _efs_bmap(struct address_space *mapping, sector_t block)
  21{
  22        return generic_block_bmap(mapping,block,efs_get_block);
  23}
  24static const struct address_space_operations efs_aops = {
  25        .readpage = efs_readpage,
  26        .bmap = _efs_bmap
  27};
  28
  29static inline void extent_copy(efs_extent *src, efs_extent *dst) {
  30        /*
  31         * this is slightly evil. it doesn't just copy
  32         * efs_extent from src to dst, it also mangles
  33         * the bits so that dst ends up in cpu byte-order.
  34         */
  35
  36        dst->cooked.ex_magic  =  (unsigned int) src->raw[0];
  37        dst->cooked.ex_bn     = ((unsigned int) src->raw[1] << 16) |
  38                                ((unsigned int) src->raw[2] <<  8) |
  39                                ((unsigned int) src->raw[3] <<  0);
  40        dst->cooked.ex_length =  (unsigned int) src->raw[4];
  41        dst->cooked.ex_offset = ((unsigned int) src->raw[5] << 16) |
  42                                ((unsigned int) src->raw[6] <<  8) |
  43                                ((unsigned int) src->raw[7] <<  0);
  44        return;
  45}
  46
  47struct inode *efs_iget(struct super_block *super, unsigned long ino)
  48{
  49        int i, inode_index;
  50        dev_t device;
  51        u32 rdev;
  52        struct buffer_head *bh;
  53        struct efs_sb_info    *sb = SUPER_INFO(super);
  54        struct efs_inode_info *in;
  55        efs_block_t block, offset;
  56        struct efs_dinode *efs_inode;
  57        struct inode *inode;
  58
  59        inode = iget_locked(super, ino);
  60        if (IS_ERR(inode))
  61                return ERR_PTR(-ENOMEM);
  62        if (!(inode->i_state & I_NEW))
  63                return inode;
  64
  65        in = INODE_INFO(inode);
  66
  67        /*
  68        ** EFS layout:
  69        **
  70        ** |   cylinder group    |   cylinder group    |   cylinder group ..etc
  71        ** |inodes|data          |inodes|data          |inodes|data       ..etc
  72        **
  73        ** work out the inode block index, (considering initially that the
  74        ** inodes are stored as consecutive blocks). then work out the block
  75        ** number of that inode given the above layout, and finally the
  76        ** offset of the inode within that block.
  77        */
  78
  79        inode_index = inode->i_ino /
  80                (EFS_BLOCKSIZE / sizeof(struct efs_dinode));
  81
  82        block = sb->fs_start + sb->first_block + 
  83                (sb->group_size * (inode_index / sb->inode_blocks)) +
  84                (inode_index % sb->inode_blocks);
  85
  86        offset = (inode->i_ino %
  87                        (EFS_BLOCKSIZE / sizeof(struct efs_dinode))) *
  88                sizeof(struct efs_dinode);
  89
  90        bh = sb_bread(inode->i_sb, block);
  91        if (!bh) {
  92                printk(KERN_WARNING "EFS: bread() failed at block %d\n", block);
  93                goto read_inode_error;
  94        }
  95
  96        efs_inode = (struct efs_dinode *) (bh->b_data + offset);
  97    
  98        inode->i_mode  = be16_to_cpu(efs_inode->di_mode);
  99        set_nlink(inode, be16_to_cpu(efs_inode->di_nlink));
 100        i_uid_write(inode, (uid_t)be16_to_cpu(efs_inode->di_uid));
 101        i_gid_write(inode, (gid_t)be16_to_cpu(efs_inode->di_gid));
 102        inode->i_size  = be32_to_cpu(efs_inode->di_size);
 103        inode->i_atime.tv_sec = be32_to_cpu(efs_inode->di_atime);
 104        inode->i_mtime.tv_sec = be32_to_cpu(efs_inode->di_mtime);
 105        inode->i_ctime.tv_sec = be32_to_cpu(efs_inode->di_ctime);
 106        inode->i_atime.tv_nsec = inode->i_mtime.tv_nsec = inode->i_ctime.tv_nsec = 0;
 107
 108        /* this is the number of blocks in the file */
 109        if (inode->i_size == 0) {
 110                inode->i_blocks = 0;
 111        } else {
 112                inode->i_blocks = ((inode->i_size - 1) >> EFS_BLOCKSIZE_BITS) + 1;
 113        }
 114
 115        rdev = be16_to_cpu(efs_inode->di_u.di_dev.odev);
 116        if (rdev == 0xffff) {
 117                rdev = be32_to_cpu(efs_inode->di_u.di_dev.ndev);
 118                if (sysv_major(rdev) > 0xfff)
 119                        device = 0;
 120                else
 121                        device = MKDEV(sysv_major(rdev), sysv_minor(rdev));
 122        } else
 123                device = old_decode_dev(rdev);
 124
 125        /* get the number of extents for this object */
 126        in->numextents = be16_to_cpu(efs_inode->di_numextents);
 127        in->lastextent = 0;
 128
 129        /* copy the extents contained within the inode to memory */
 130        for(i = 0; i < EFS_DIRECTEXTENTS; i++) {
 131                extent_copy(&(efs_inode->di_u.di_extents[i]), &(in->extents[i]));
 132                if (i < in->numextents && in->extents[i].cooked.ex_magic != 0) {
 133                        printk(KERN_WARNING "EFS: extent %d has bad magic number in inode %lu\n", i, inode->i_ino);
 134                        brelse(bh);
 135                        goto read_inode_error;
 136                }
 137        }
 138
 139        brelse(bh);
 140   
 141#ifdef DEBUG
 142        printk(KERN_DEBUG "EFS: efs_iget(): inode %lu, extents %d, mode %o\n",
 143                inode->i_ino, in->numextents, inode->i_mode);
 144#endif
 145
 146        switch (inode->i_mode & S_IFMT) {
 147                case S_IFDIR: 
 148                        inode->i_op = &efs_dir_inode_operations; 
 149                        inode->i_fop = &efs_dir_operations; 
 150                        break;
 151                case S_IFREG:
 152                        inode->i_fop = &generic_ro_fops;
 153                        inode->i_data.a_ops = &efs_aops;
 154                        break;
 155                case S_IFLNK:
 156                        inode->i_op = &page_symlink_inode_operations;
 157                        inode->i_data.a_ops = &efs_symlink_aops;
 158                        break;
 159                case S_IFCHR:
 160                case S_IFBLK:
 161                case S_IFIFO:
 162                        init_special_inode(inode, inode->i_mode, device);
 163                        break;
 164                default:
 165                        printk(KERN_WARNING "EFS: unsupported inode mode %o\n", inode->i_mode);
 166                        goto read_inode_error;
 167                        break;
 168        }
 169
 170        unlock_new_inode(inode);
 171        return inode;
 172        
 173read_inode_error:
 174        printk(KERN_WARNING "EFS: failed to read inode %lu\n", inode->i_ino);
 175        iget_failed(inode);
 176        return ERR_PTR(-EIO);
 177}
 178
 179static inline efs_block_t
 180efs_extent_check(efs_extent *ptr, efs_block_t block, struct efs_sb_info *sb) {
 181        efs_block_t start;
 182        efs_block_t length;
 183        efs_block_t offset;
 184
 185        /*
 186         * given an extent and a logical block within a file,
 187         * can this block be found within this extent ?
 188         */
 189        start  = ptr->cooked.ex_bn;
 190        length = ptr->cooked.ex_length;
 191        offset = ptr->cooked.ex_offset;
 192
 193        if ((block >= offset) && (block < offset+length)) {
 194                return(sb->fs_start + start + block - offset);
 195        } else {
 196                return 0;
 197        }
 198}
 199
 200efs_block_t efs_map_block(struct inode *inode, efs_block_t block) {
 201        struct efs_sb_info    *sb = SUPER_INFO(inode->i_sb);
 202        struct efs_inode_info *in = INODE_INFO(inode);
 203        struct buffer_head    *bh = NULL;
 204
 205        int cur, last, first = 1;
 206        int ibase, ioffset, dirext, direxts, indext, indexts;
 207        efs_block_t iblock, result = 0, lastblock = 0;
 208        efs_extent ext, *exts;
 209
 210        last = in->lastextent;
 211
 212        if (in->numextents <= EFS_DIRECTEXTENTS) {
 213                /* first check the last extent we returned */
 214                if ((result = efs_extent_check(&in->extents[last], block, sb)))
 215                        return result;
 216    
 217                /* if we only have one extent then nothing can be found */
 218                if (in->numextents == 1) {
 219                        printk(KERN_ERR "EFS: map_block() failed to map (1 extent)\n");
 220                        return 0;
 221                }
 222
 223                direxts = in->numextents;
 224
 225                /*
 226                 * check the stored extents in the inode
 227                 * start with next extent and check forwards
 228                 */
 229                for(dirext = 1; dirext < direxts; dirext++) {
 230                        cur = (last + dirext) % in->numextents;
 231                        if ((result = efs_extent_check(&in->extents[cur], block, sb))) {
 232                                in->lastextent = cur;
 233                                return result;
 234                        }
 235                }
 236
 237                printk(KERN_ERR "EFS: map_block() failed to map block %u (dir)\n", block);
 238                return 0;
 239        }
 240
 241#ifdef DEBUG
 242        printk(KERN_DEBUG "EFS: map_block(): indirect search for logical block %u\n", block);
 243#endif
 244        direxts = in->extents[0].cooked.ex_offset;
 245        indexts = in->numextents;
 246
 247        for(indext = 0; indext < indexts; indext++) {
 248                cur = (last + indext) % indexts;
 249
 250                /*
 251                 * work out which direct extent contains `cur'.
 252                 *
 253                 * also compute ibase: i.e. the number of the first
 254                 * indirect extent contained within direct extent `cur'.
 255                 *
 256                 */
 257                ibase = 0;
 258                for(dirext = 0; cur < ibase && dirext < direxts; dirext++) {
 259                        ibase += in->extents[dirext].cooked.ex_length *
 260                                (EFS_BLOCKSIZE / sizeof(efs_extent));
 261                }
 262
 263                if (dirext == direxts) {
 264                        /* should never happen */
 265                        printk(KERN_ERR "EFS: couldn't find direct extent for indirect extent %d (block %u)\n", cur, block);
 266                        if (bh) brelse(bh);
 267                        return 0;
 268                }
 269                
 270                /* work out block number and offset of this indirect extent */
 271                iblock = sb->fs_start + in->extents[dirext].cooked.ex_bn +
 272                        (cur - ibase) /
 273                        (EFS_BLOCKSIZE / sizeof(efs_extent));
 274                ioffset = (cur - ibase) %
 275                        (EFS_BLOCKSIZE / sizeof(efs_extent));
 276
 277                if (first || lastblock != iblock) {
 278                        if (bh) brelse(bh);
 279
 280                        bh = sb_bread(inode->i_sb, iblock);
 281                        if (!bh) {
 282                                printk(KERN_ERR "EFS: bread() failed at block %d\n", iblock);
 283                                return 0;
 284                        }
 285#ifdef DEBUG
 286                        printk(KERN_DEBUG "EFS: map_block(): read indirect extent block %d\n", iblock);
 287#endif
 288                        first = 0;
 289                        lastblock = iblock;
 290                }
 291
 292                exts = (efs_extent *) bh->b_data;
 293
 294                extent_copy(&(exts[ioffset]), &ext);
 295
 296                if (ext.cooked.ex_magic != 0) {
 297                        printk(KERN_ERR "EFS: extent %d has bad magic number in block %d\n", cur, iblock);
 298                        if (bh) brelse(bh);
 299                        return 0;
 300                }
 301
 302                if ((result = efs_extent_check(&ext, block, sb))) {
 303                        if (bh) brelse(bh);
 304                        in->lastextent = cur;
 305                        return result;
 306                }
 307        }
 308        if (bh) brelse(bh);
 309        printk(KERN_ERR "EFS: map_block() failed to map block %u (indir)\n", block);
 310        return 0;
 311}  
 312
 313MODULE_LICENSE("GPL");
 314
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