fs/efs/inode.c

   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/efs_fs.h>
  11 #include <linux/efs_fs_sb.h>
  12
  13 static inline void extent_copy(efs_extent *src, efs_extent *dst) {
  14         /*
  15          * this is slightly evil. it doesn't just copy
  16          * efs_extent from src to dst, it also mangles
  17          * the bits so that dst ends up in cpu byte-order.
  18          */
  19
  20         dst->cooked.ex_magic  =  (unsigned int) src->raw[0];
  21         dst->cooked.ex_bn     = ((unsigned int) src->raw[1] << 16) |
  22                                 ((unsigned int) src->raw[2] <<  8) |
  23                                 ((unsigned int) src->raw[3] <<  0);
  24         dst->cooked.ex_length =  (unsigned int) src->raw[4];
  25         dst->cooked.ex_offset = ((unsigned int) src->raw[5] << 16) |
  26                                 ((unsigned int) src->raw[6] <<  8) |
  27                                 ((unsigned int) src->raw[7] <<  0);
  28         return;
  29 }
  30
  31 void efs_read_inode(struct inode *inode) {
  32         int i, inode_index;
  33         dev_t device;
  34         struct buffer_head *bh;
  35         struct efs_sb_info    *sb = SUPER_INFO(inode->i_sb);
  36         struct efs_inode_info *in = INODE_INFO(inode);
  37         efs_block_t block, offset;
  38         struct efs_dinode *efs_inode;
  39
  40         /*
  41         ** EFS layout:
  42         **
  43         ** |   cylinder group    |   cylinder group    |   cylinder group ..etc
  44         ** |inodes|data          |inodes|data          |inodes|data       ..etc
  45         **
  46         ** work out the inode block index, (considering initially that the
  47         ** inodes are stored as consecutive blocks). then work out the block
  48         ** number of that inode given the above layout, and finally the
  49         ** offset of the inode within that block.
  50         */
  51
  52         inode_index = inode->i_ino /
  53                 (EFS_BLOCKSIZE / sizeof(struct efs_dinode));
  54
  55         block = sb->fs_start + sb->first_block +
  56                 (sb->group_size * (inode_index / sb->inode_blocks)) +
  57                 (inode_index % sb->inode_blocks);
  58
  59         offset = (inode->i_ino %
  60                         (EFS_BLOCKSIZE / sizeof(struct efs_dinode))) *
  61                 sizeof(struct efs_dinode);
  62
  63         bh = bread(inode->i_dev, block, EFS_BLOCKSIZE);
  64         if (!bh) {
  65                 printk(KERN_WARNING "EFS: bread() failed at block %d\n", block);
  66                 goto read_inode_error;
  67         }
  68
  69         efs_inode = (struct efs_dinode *) (bh->b_data + offset);
  70
  71         inode->i_mode  = be16_to_cpu(efs_inode->di_mode);
  72         inode->i_nlink = be16_to_cpu(efs_inode->di_nlink);
  73         inode->i_uid   = be16_to_cpu(efs_inode->di_uid);
  74         inode->i_gid   = be16_to_cpu(efs_inode->di_gid);
  75         inode->i_size  = be32_to_cpu(efs_inode->di_size);
  76         inode->i_atime = be32_to_cpu(efs_inode->di_atime);
  77         inode->i_mtime = be32_to_cpu(efs_inode->di_mtime);
  78         inode->i_ctime = be32_to_cpu(efs_inode->di_ctime);
  79
  80         /* this is the number of blocks in the file */
  81         if (inode->i_size == 0) {
  82                 inode->i_blocks = 0;
  83         } else {
  84                 inode->i_blocks = ((inode->i_size - 1) >> EFS_BLOCKSIZE_BITS) + 1;
  85         }
  86
  87         /*
  88          * BUG: irix dev_t is 32-bits. linux dev_t is only 16-bits.
  89          *
  90          * apparently linux will change to 32-bit dev_t sometime during
  91          * linux 2.3.
  92          *
  93          * as is, this code maps devices that can't be represented in
  94          * 16-bits (ie major > 255 or minor > 255) to major = minor = 255.
  95          *
  96          * during 2.3 when 32-bit dev_t become available, we should test
  97          * to see whether odev contains 65535. if this is the case then we
  98          * should then do device = be32_to_cpu(efs_inode->di_u.di_dev.ndev).
  99          */
 100         device = be16_to_cpu(efs_inode->di_u.di_dev.odev);
 101
 102         /* get the number of extents for this object */
 103         in->numextents = be16_to_cpu(efs_inode->di_numextents);
 104         in->lastextent = 0;
 105
 106         /* copy the extents contained within the inode to memory */
 107         for(i = 0; i < EFS_DIRECTEXTENTS; i++) {
 108                 extent_copy(&(efs_inode->di_u.di_extents[i]), &(in->extents[i]));
 109                 if (i < in->numextents && in->extents[i].cooked.ex_magic != 0) {
 110                         printk(KERN_WARNING "EFS: extent %d has bad magic number in inode %lu\n", i, inode->i_ino);
 111                         brelse(bh);
 112                         goto read_inode_error;
 113                 }
 114         }
 115
 116         brelse(bh);
 117
 118 #ifdef DEBUG
 119         printk(KERN_DEBUG "EFS: read_inode(): inode %lu, extents %d, mode %o\n",
 120                 inode->i_ino, in->numextents, inode->i_mode);
 121 #endif
 122
 123         switch (inode->i_mode & S_IFMT) {
 124                 case S_IFDIR:
 125                         inode->i_op = &efs_dir_inode_operations;
 126                         break;
 127                 case S_IFREG:
 128                         inode->i_op = &efs_file_inode_operations;
 129                         break;
 130                 case S_IFLNK:
 131                         inode->i_op = &efs_symlink_inode_operations;
 132                         break;
 133                 case S_IFCHR:
 134                         inode->i_rdev = device;
 135                         inode->i_op = &chrdev_inode_operations;
 136                         break;
 137                 case S_IFBLK:
 138                         inode->i_rdev = device;
 139                         inode->i_op = &blkdev_inode_operations;
 140                         break;
 141                 case S_IFIFO:
 142                         init_fifo(inode);
 143                         break;
 144                 default:
 145                         printk(KERN_WARNING "EFS: unsupported inode mode %o\n", inode->i_mode);
 146                         goto read_inode_error;
 147                         break;
 148         }
 149
 150         return;
 151
 152 read_inode_error:
 153         printk(KERN_WARNING "EFS: failed to read inode %lu\n", inode->i_ino);
 154         inode->i_mode = S_IFREG;
 155         inode->i_atime = 0;
 156         inode->i_ctime = 0;
 157         inode->i_mtime = 0;
 158         inode->i_nlink = 1;
 159         inode->i_size = 0;
 160         inode->i_blocks = 0;
 161         inode->i_uid = 0;
 162         inode->i_gid = 0;
 163         inode->i_op = NULL;
 164
 165         return;
 166 }
 167
 168 static inline efs_block_t
 169 efs_extent_check(efs_extent *ptr, efs_block_t block, struct efs_sb_info *sb) {
 170         efs_block_t start;
 171         efs_block_t length;
 172         efs_block_t offset;
 173
 174         /*
 175          * given an extent and a logical block within a file,
 176          * can this block be found within this extent ?
 177          */
 178         start  = ptr->cooked.ex_bn;
 179         length = ptr->cooked.ex_length;
 180         offset = ptr->cooked.ex_offset;
 181
 182         if ((block >= offset) && (block < offset+length)) {
 183                 return(sb->fs_start + start + block - offset);
 184         } else {
 185                 return 0;
 186         }
 187 }
 188
 189 efs_block_t efs_map_block(struct inode *inode, efs_block_t block) {
 190         struct efs_sb_info    *sb = SUPER_INFO(inode->i_sb);
 191         struct efs_inode_info *in = INODE_INFO(inode);
 192         struct buffer_head    *bh = NULL;
 193
 194         int cur, last, first = 1;
 195         int ibase, ioffset, dirext, direxts, indext, indexts;
 196         efs_block_t iblock, result = 0, lastblock = 0;
 197         efs_extent ext, *exts;
 198
 199         last = in->lastextent;
 200
 201         if (in->numextents <= EFS_DIRECTEXTENTS) {
 202                 /* first check the last extent we returned */
 203                 if ((result = efs_extent_check(&in->extents[last], block, sb)))
 204                         return result;
 205
 206                 /* if we only have one extent then nothing can be found */
 207                 if (in->numextents == 1) {
 208                         printk(KERN_ERR "EFS: map_block() failed to map (1 extent)\n");
 209                         return 0;
 210                 }
 211
 212                 direxts = in->numextents;
 213
 214                 /*
 215                  * check the stored extents in the inode
 216                  * start with next extent and check forwards
 217                  */
 218                 for(dirext = 1; dirext < direxts; dirext++) {
 219                         cur = (last + dirext) % in->numextents;
 220                         if ((result = efs_extent_check(&in->extents[cur], block, sb))) {
 221                                 in->lastextent = cur;
 222                                 return result;
 223                         }
 224                 }
 225
 226                 printk(KERN_ERR "EFS: map_block() failed to map block %u (dir)\n", block);
 227                 return 0;
 228         }
 229
 230 #ifdef DEBUG
 231         printk(KERN_DEBUG "EFS: map_block(): indirect search for logical block %u\n", block);
 232 #endif
 233         direxts = in->extents[0].cooked.ex_offset;
 234         indexts = in->numextents;
 235
 236         for(indext = 0; indext < indexts; indext++) {
 237                 cur = (last + indext) % indexts;
 238
 239                 /*
 240                  * work out which direct extent contains `cur'.
 241                  *
 242                  * also compute ibase: i.e. the number of the first
 243                  * indirect extent contained within direct extent `cur'.
 244                  *
 245                  */
 246                 ibase = 0;
 247                 for(dirext = 0; cur < ibase && dirext < direxts; dirext++) {
 248                         ibase += in->extents[dirext].cooked.ex_length *
 249                                 (EFS_BLOCKSIZE / sizeof(efs_extent));
 250                 }
 251
 252                 if (dirext == direxts) {
 253                         /* should never happen */
 254                         printk(KERN_ERR "EFS: couldn't find direct extent for indirect extent %d (block %u)\n", cur, block);
 255                         if (bh) brelse(bh);
 256                         return 0;
 257                 }
 258
 259                 /* work out block number and offset of this indirect extent */
 260                 iblock = sb->fs_start + in->extents[dirext].cooked.ex_bn +
 261                         (cur - ibase) /
 262                         (EFS_BLOCKSIZE / sizeof(efs_extent));
 263                 ioffset = (cur - ibase) %
 264                         (EFS_BLOCKSIZE / sizeof(efs_extent));
 265
 266                 if (first || lastblock != iblock) {
 267                         if (bh) brelse(bh);
 268
 269                         bh = bread(inode->i_dev, iblock, EFS_BLOCKSIZE);
 270                         if (!bh) {
 271                                 printk(KERN_ERR "EFS: bread() failed at block %d\n", iblock);
 272                                 return 0;
 273                         }
 274 #ifdef DEBUG
 275                         printk(KERN_DEBUG "EFS: map_block(): read indirect extent block %d\n", iblock);
 276 #endif
 277                         first = 0;
 278                         lastblock = iblock;
 279                 }
 280
 281                 exts = (efs_extent *) bh->b_data;
 282
 283                 extent_copy(&(exts[ioffset]), &ext);
 284
 285                 if (ext.cooked.ex_magic != 0) {
 286                         printk(KERN_ERR "EFS: extent %d has bad magic number in block %d\n", cur, iblock);
 287                         if (bh) brelse(bh);
 288                         return 0;
 289                 }
 290
 291                 if ((result = efs_extent_check(&ext, block, sb))) {
 292                         if (bh) brelse(bh);
 293                         in->lastextent = cur;
 294                         return result;
 295                 }
 296         }
 297         if (bh) brelse(bh);
 298         printk(KERN_ERR "EFS: map_block() failed to map block %u (indir)\n", block);
 299         return 0;
 300 }
 301