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 extern int efs_get_block(struct inode *, long, struct buffer_head *, int);
  14 static int efs_readpage(struct dentry *dentry, struct page *page)
  15 {
  16         return block_read_full_page(page,efs_get_block);
  17 }
  18 static int _efs_bmap(struct address_space *mapping, long block)
  19 {
  20         return generic_block_bmap(mapping,block,efs_get_block);
  21 }
  22 struct address_space_operations efs_aops = {
  23         readpage: efs_readpage,
  24         bmap: _efs_bmap
  25 };
  26
  27 static inline void extent_copy(efs_extent *src, efs_extent *dst) {
  28         /*
  29          * this is slightly evil. it doesn't just copy
  30          * efs_extent from src to dst, it also mangles
  31          * the bits so that dst ends up in cpu byte-order.
  32          */
  33
  34         dst->cooked.ex_magic  =  (unsigned int) src->raw[0];
  35         dst->cooked.ex_bn     = ((unsigned int) src->raw[1] << 16) |
  36                                 ((unsigned int) src->raw[2] <<  8) |
  37                                 ((unsigned int) src->raw[3] <<  0);
  38         dst->cooked.ex_length =  (unsigned int) src->raw[4];
  39         dst->cooked.ex_offset = ((unsigned int) src->raw[5] << 16) |
  40                                 ((unsigned int) src->raw[6] <<  8) |
  41                                 ((unsigned int) src->raw[7] <<  0);
  42         return;
  43 }
  44
  45 void efs_read_inode(struct inode *inode) {
  46         int i, inode_index;
  47         dev_t device;
  48         struct buffer_head *bh;
  49         struct efs_sb_info    *sb = SUPER_INFO(inode->i_sb);
  50         struct efs_inode_info *in = INODE_INFO(inode);
  51         efs_block_t block, offset;
  52         struct efs_dinode *efs_inode;
  53
  54         /*
  55         ** EFS layout:
  56         **
  57         ** |   cylinder group    |   cylinder group    |   cylinder group ..etc
  58         ** |inodes|data          |inodes|data          |inodes|data       ..etc
  59         **
  60         ** work out the inode block index, (considering initially that the
  61         ** inodes are stored as consecutive blocks). then work out the block
  62         ** number of that inode given the above layout, and finally the
  63         ** offset of the inode within that block.
  64         */
  65
  66         inode_index = inode->i_ino /
  67                 (EFS_BLOCKSIZE / sizeof(struct efs_dinode));
  68
  69         block = sb->fs_start + sb->first_block +
  70                 (sb->group_size * (inode_index / sb->inode_blocks)) +
  71                 (inode_index % sb->inode_blocks);
  72
  73         offset = (inode->i_ino %
  74                         (EFS_BLOCKSIZE / sizeof(struct efs_dinode))) *
  75                 sizeof(struct efs_dinode);
  76
  77         bh = bread(inode->i_dev, block, EFS_BLOCKSIZE);
  78         if (!bh) {
  79                 printk(KERN_WARNING "EFS: bread() failed at block %d\n", block);
  80                 goto read_inode_error;
  81         }
  82
  83         efs_inode = (struct efs_dinode *) (bh->b_data + offset);
  84
  85         inode->i_mode  = be16_to_cpu(efs_inode->di_mode);
  86         inode->i_nlink = be16_to_cpu(efs_inode->di_nlink);
  87         inode->i_uid   = (uid_t)be16_to_cpu(efs_inode->di_uid);
  88         inode->i_gid   = (gid_t)be16_to_cpu(efs_inode->di_gid);
  89         inode->i_size  = be32_to_cpu(efs_inode->di_size);
  90         inode->i_atime = be32_to_cpu(efs_inode->di_atime);
  91         inode->i_mtime = be32_to_cpu(efs_inode->di_mtime);
  92         inode->i_ctime = be32_to_cpu(efs_inode->di_ctime);
  93
  94         /* this is the number of blocks in the file */
  95         if (inode->i_size == 0) {
  96                 inode->i_blocks = 0;
  97         } else {
  98                 inode->i_blocks = ((inode->i_size - 1) >> EFS_BLOCKSIZE_BITS) + 1;
  99         }
 100
 101         /*
 102          * BUG: irix dev_t is 32-bits. linux dev_t is only 16-bits.
 103          *
 104          * apparently linux will change to 32-bit dev_t sometime during
 105          * linux 2.3.
 106          *
 107          * as is, this code maps devices that can't be represented in
 108          * 16-bits (ie major > 255 or minor > 255) to major = minor = 255.
 109          *
 110          * during 2.3 when 32-bit dev_t become available, we should test
 111          * to see whether odev contains 65535. if this is the case then we
 112          * should then do device = be32_to_cpu(efs_inode->di_u.di_dev.ndev).
 113          */
 114         device = be16_to_cpu(efs_inode->di_u.di_dev.odev);
 115
 116         /* get the number of extents for this object */
 117         in->numextents = be16_to_cpu(efs_inode->di_numextents);
 118         in->lastextent = 0;
 119
 120         /* copy the extents contained within the inode to memory */
 121         for(i = 0; i < EFS_DIRECTEXTENTS; i++) {
 122                 extent_copy(&(efs_inode->di_u.di_extents[i]), &(in->extents[i]));
 123                 if (i < in->numextents && in->extents[i].cooked.ex_magic != 0) {
 124                         printk(KERN_WARNING "EFS: extent %d has bad magic number in inode %lu\n", i, inode->i_ino);
 125                         brelse(bh);
 126                         goto read_inode_error;
 127                 }
 128         }
 129
 130         brelse(bh);
 131
 132 #ifdef DEBUG
 133         printk(KERN_DEBUG "EFS: read_inode(): inode %lu, extents %d, mode %o\n",
 134                 inode->i_ino, in->numextents, inode->i_mode);
 135 #endif
 136
 137         switch (inode->i_mode & S_IFMT) {
 138                 case S_IFDIR:
 139                         inode->i_op = &efs_dir_inode_operations;
 140                         inode->i_fop = &efs_dir_operations;
 141                         break;
 142                 case S_IFREG:
 143                         inode->i_fop = &generic_ro_fops;
 144                         inode->i_data.a_ops = &efs_aops;
 145                         break;
 146                 case S_IFLNK:
 147                         inode->i_op = &page_symlink_inode_operations;
 148                         inode->i_data.a_ops = &efs_symlink_aops;
 149                         break;
 150                 case S_IFCHR:
 151                 case S_IFBLK:
 152                 case S_IFIFO:
 153                         init_special_inode(inode, inode->i_mode, device);
 154                         break;
 155                 default:
 156                         printk(KERN_WARNING "EFS: unsupported inode mode %o\n", inode->i_mode);
 157                         goto read_inode_error;
 158                         break;
 159         }
 160
 161         return;
 162
 163 read_inode_error:
 164         printk(KERN_WARNING "EFS: failed to read inode %lu\n", inode->i_ino);
 165         make_bad_inode(inode);
 166
 167         return;
 168 }
 169
 170 static inline efs_block_t
 171 efs_extent_check(efs_extent *ptr, efs_block_t block, struct efs_sb_info *sb) {
 172         efs_block_t start;
 173         efs_block_t length;
 174         efs_block_t offset;
 175
 176         /*
 177          * given an extent and a logical block within a file,
 178          * can this block be found within this extent ?
 179          */
 180         start  = ptr->cooked.ex_bn;
 181         length = ptr->cooked.ex_length;
 182         offset = ptr->cooked.ex_offset;
 183
 184         if ((block >= offset) && (block < offset+length)) {
 185                 return(sb->fs_start + start + block - offset);
 186         } else {
 187                 return 0;
 188         }
 189 }
 190
 191 efs_block_t efs_map_block(struct inode *inode, efs_block_t block) {
 192         struct efs_sb_info    *sb = SUPER_INFO(inode->i_sb);
 193         struct efs_inode_info *in = INODE_INFO(inode);
 194         struct buffer_head    *bh = NULL;
 195
 196         int cur, last, first = 1;
 197         int ibase, ioffset, dirext, direxts, indext, indexts;
 198         efs_block_t iblock, result = 0, lastblock = 0;
 199         efs_extent ext, *exts;
 200
 201         last = in->lastextent;
 202
 203         if (in->numextents <= EFS_DIRECTEXTENTS) {
 204                 /* first check the last extent we returned */
 205                 if ((result = efs_extent_check(&in->extents[last], block, sb)))
 206                         return result;
 207
 208                 /* if we only have one extent then nothing can be found */
 209                 if (in->numextents == 1) {
 210                         printk(KERN_ERR "EFS: map_block() failed to map (1 extent)\n");
 211                         return 0;
 212                 }
 213
 214                 direxts = in->numextents;
 215
 216                 /*
 217                  * check the stored extents in the inode
 218                  * start with next extent and check forwards
 219                  */
 220                 for(dirext = 1; dirext < direxts; dirext++) {
 221                         cur = (last + dirext) % in->numextents;
 222                         if ((result = efs_extent_check(&in->extents[cur], block, sb))) {
 223                                 in->lastextent = cur;
 224                                 return result;
 225                         }
 226                 }
 227
 228                 printk(KERN_ERR "EFS: map_block() failed to map block %u (dir)\n", block);
 229                 return 0;
 230         }
 231
 232 #ifdef DEBUG
 233         printk(KERN_DEBUG "EFS: map_block(): indirect search for logical block %u\n", block);
 234 #endif
 235         direxts = in->extents[0].cooked.ex_offset;
 236         indexts = in->numextents;
 237
 238         for(indext = 0; indext < indexts; indext++) {
 239                 cur = (last + indext) % indexts;
 240
 241                 /*
 242                  * work out which direct extent contains `cur'.
 243                  *
 244                  * also compute ibase: i.e. the number of the first
 245                  * indirect extent contained within direct extent `cur'.
 246                  *
 247                  */
 248                 ibase = 0;
 249                 for(dirext = 0; cur < ibase && dirext < direxts; dirext++) {
 250                         ibase += in->extents[dirext].cooked.ex_length *
 251                                 (EFS_BLOCKSIZE / sizeof(efs_extent));
 252                 }
 253
 254                 if (dirext == direxts) {
 255                         /* should never happen */
 256                         printk(KERN_ERR "EFS: couldn't find direct extent for indirect extent %d (block %u)\n", cur, block);
 257                         if (bh) brelse(bh);
 258                         return 0;
 259                 }
 260
 261                 /* work out block number and offset of this indirect extent */
 262                 iblock = sb->fs_start + in->extents[dirext].cooked.ex_bn +
 263                         (cur - ibase) /
 264                         (EFS_BLOCKSIZE / sizeof(efs_extent));
 265                 ioffset = (cur - ibase) %
 266                         (EFS_BLOCKSIZE / sizeof(efs_extent));
 267
 268                 if (first || lastblock != iblock) {
 269                         if (bh) brelse(bh);
 270
 271                         bh = bread(inode->i_dev, iblock, EFS_BLOCKSIZE);
 272                         if (!bh) {
 273                                 printk(KERN_ERR "EFS: bread() failed at block %d\n", iblock);
 274                                 return 0;
 275                         }
 276 #ifdef DEBUG
 277                         printk(KERN_DEBUG "EFS: map_block(): read indirect extent block %d\n", iblock);
 278 #endif
 279                         first = 0;
 280                         lastblock = iblock;
 281                 }
 282
 283                 exts = (efs_extent *) bh->b_data;
 284
 285                 extent_copy(&(exts[ioffset]), &ext);
 286
 287                 if (ext.cooked.ex_magic != 0) {
 288                         printk(KERN_ERR "EFS: extent %d has bad magic number in block %d\n", cur, iblock);
 289                         if (bh) brelse(bh);
 290                         return 0;
 291                 }
 292
 293                 if ((result = efs_extent_check(&ext, block, sb))) {
 294                         if (bh) brelse(bh);
 295                         in->lastextent = cur;
 296                         return result;
 297                 }
 298         }
 299         if (bh) brelse(bh);
 300         printk(KERN_ERR "EFS: map_block() failed to map block %u (indir)\n", block);
 301         return 0;
 302 }
 303