root/fs/efs/inode.c

DEFINITIONS

1. efs_readpage
2. _efs_bmap
3. extent_copy
4. efs_iget
5. efs_extent_check
6. efs_map_block

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * inode.c
   4  *
   5  * Copyright (c) 1999 Al Smith
   6  *
   7  * Portions derived from work (c) 1995,1996 Christian Vogelgsang,
   8  *              and from work (c) 1998 Mike Shaver.
   9  */
  10 
  11 #include <linux/buffer_head.h>
  12 #include <linux/module.h>
  13 #include <linux/fs.h>
  14 #include "efs.h"
  15 #include <linux/efs_fs_sb.h>
  16 
  17 static int efs_readpage(struct file *file, struct page *page)
  18 {
  19         return block_read_full_page(page,efs_get_block);
  20 }
  21 static sector_t _efs_bmap(struct address_space *mapping, sector_t block)
  22 {
  23         return generic_block_bmap(mapping,block,efs_get_block);
  24 }
  25 static const struct address_space_operations efs_aops = {
  26         .readpage = efs_readpage,
  27         .bmap = _efs_bmap
  28 };
  29 
  30 static inline void extent_copy(efs_extent *src, efs_extent *dst) {
  31         /*
  32          * this is slightly evil. it doesn't just copy
  33          * efs_extent from src to dst, it also mangles
  34          * the bits so that dst ends up in cpu byte-order.
  35          */
  36 
  37         dst->cooked.ex_magic  =  (unsigned int) src->raw[0];
  38         dst->cooked.ex_bn     = ((unsigned int) src->raw[1] << 16) |
  39                                 ((unsigned int) src->raw[2] <<  8) |
  40                                 ((unsigned int) src->raw[3] <<  0);
  41         dst->cooked.ex_length =  (unsigned int) src->raw[4];
  42         dst->cooked.ex_offset = ((unsigned int) src->raw[5] << 16) |
  43                                 ((unsigned int) src->raw[6] <<  8) |
  44                                 ((unsigned int) src->raw[7] <<  0);
  45         return;
  46 }
  47 
  48 struct inode *efs_iget(struct super_block *super, unsigned long ino)
  49 {
  50         int i, inode_index;
  51         dev_t device;
  52         u32 rdev;
  53         struct buffer_head *bh;
  54         struct efs_sb_info    *sb = SUPER_INFO(super);
  55         struct efs_inode_info *in;
  56         efs_block_t block, offset;
  57         struct efs_dinode *efs_inode;
  58         struct inode *inode;
  59 
  60         inode = iget_locked(super, ino);
  61         if (!inode)
  62                 return ERR_PTR(-ENOMEM);
  63         if (!(inode->i_state & I_NEW))
  64                 return inode;
  65 
  66         in = INODE_INFO(inode);
  67 
  68         /*
  69         ** EFS layout:
  70         **
  71         ** |   cylinder group    |   cylinder group    |   cylinder group ..etc
  72         ** |inodes|data          |inodes|data          |inodes|data       ..etc
  73         **
  74         ** work out the inode block index, (considering initially that the
  75         ** inodes are stored as consecutive blocks). then work out the block
  76         ** number of that inode given the above layout, and finally the
  77         ** offset of the inode within that block.
  78         */
  79 
  80         inode_index = inode->i_ino /
  81                 (EFS_BLOCKSIZE / sizeof(struct efs_dinode));
  82 
  83         block = sb->fs_start + sb->first_block + 
  84                 (sb->group_size * (inode_index / sb->inode_blocks)) +
  85                 (inode_index % sb->inode_blocks);
  86 
  87         offset = (inode->i_ino %
  88                         (EFS_BLOCKSIZE / sizeof(struct efs_dinode))) *
  89                 sizeof(struct efs_dinode);
  90 
  91         bh = sb_bread(inode->i_sb, block);
  92         if (!bh) {
  93                 pr_warn("%s() failed at block %d\n", __func__, block);
  94                 goto read_inode_error;
  95         }
  96 
  97         efs_inode = (struct efs_dinode *) (bh->b_data + offset);
  98     
  99         inode->i_mode  = be16_to_cpu(efs_inode->di_mode);
 100         set_nlink(inode, be16_to_cpu(efs_inode->di_nlink));
 101         i_uid_write(inode, (uid_t)be16_to_cpu(efs_inode->di_uid));
 102         i_gid_write(inode, (gid_t)be16_to_cpu(efs_inode->di_gid));
 103         inode->i_size  = be32_to_cpu(efs_inode->di_size);
 104         inode->i_atime.tv_sec = be32_to_cpu(efs_inode->di_atime);
 105         inode->i_mtime.tv_sec = be32_to_cpu(efs_inode->di_mtime);
 106         inode->i_ctime.tv_sec = be32_to_cpu(efs_inode->di_ctime);
 107         inode->i_atime.tv_nsec = inode->i_mtime.tv_nsec = inode->i_ctime.tv_nsec = 0;
 108 
 109         /* this is the number of blocks in the file */
 110         if (inode->i_size == 0) {
 111                 inode->i_blocks = 0;
 112         } else {
 113                 inode->i_blocks = ((inode->i_size - 1) >> EFS_BLOCKSIZE_BITS) + 1;
 114         }
 115 
 116         rdev = be16_to_cpu(efs_inode->di_u.di_dev.odev);
 117         if (rdev == 0xffff) {
 118                 rdev = be32_to_cpu(efs_inode->di_u.di_dev.ndev);
 119                 if (sysv_major(rdev) > 0xfff)
 120                         device = 0;
 121                 else
 122                         device = MKDEV(sysv_major(rdev), sysv_minor(rdev));
 123         } else
 124                 device = old_decode_dev(rdev);
 125 
 126         /* get the number of extents for this object */
 127         in->numextents = be16_to_cpu(efs_inode->di_numextents);
 128         in->lastextent = 0;
 129 
 130         /* copy the extents contained within the inode to memory */
 131         for(i = 0; i < EFS_DIRECTEXTENTS; i++) {
 132                 extent_copy(&(efs_inode->di_u.di_extents[i]), &(in->extents[i]));
 133                 if (i < in->numextents && in->extents[i].cooked.ex_magic != 0) {
 134                         pr_warn("extent %d has bad magic number in inode %lu\n",
 135                                 i, inode->i_ino);
 136                         brelse(bh);
 137                         goto read_inode_error;
 138                 }
 139         }
 140 
 141         brelse(bh);
 142         pr_debug("efs_iget(): inode %lu, extents %d, mode %o\n",
 143                  inode->i_ino, in->numextents, inode->i_mode);
 144         switch (inode->i_mode & S_IFMT) {
 145                 case S_IFDIR: 
 146                         inode->i_op = &efs_dir_inode_operations; 
 147                         inode->i_fop = &efs_dir_operations; 
 148                         break;
 149                 case S_IFREG:
 150                         inode->i_fop = &generic_ro_fops;
 151                         inode->i_data.a_ops = &efs_aops;
 152                         break;
 153                 case S_IFLNK:
 154                         inode->i_op = &page_symlink_inode_operations;
 155                         inode_nohighmem(inode);
 156                         inode->i_data.a_ops = &efs_symlink_aops;
 157                         break;
 158                 case S_IFCHR:
 159                 case S_IFBLK:
 160                 case S_IFIFO:
 161                         init_special_inode(inode, inode->i_mode, device);
 162                         break;
 163                 default:
 164                         pr_warn("unsupported inode mode %o\n", inode->i_mode);
 165                         goto read_inode_error;
 166                         break;
 167         }
 168 
 169         unlock_new_inode(inode);
 170         return inode;
 171         
 172 read_inode_error:
 173         pr_warn("failed to read inode %lu\n", inode->i_ino);
 174         iget_failed(inode);
 175         return ERR_PTR(-EIO);
 176 }
 177 
 178 static inline efs_block_t
 179 efs_extent_check(efs_extent *ptr, efs_block_t block, struct efs_sb_info *sb) {
 180         efs_block_t start;
 181         efs_block_t length;
 182         efs_block_t offset;
 183 
 184         /*
 185          * given an extent and a logical block within a file,
 186          * can this block be found within this extent ?
 187          */
 188         start  = ptr->cooked.ex_bn;
 189         length = ptr->cooked.ex_length;
 190         offset = ptr->cooked.ex_offset;
 191 
 192         if ((block >= offset) && (block < offset+length)) {
 193                 return(sb->fs_start + start + block - offset);
 194         } else {
 195                 return 0;
 196         }
 197 }
 198 
 199 efs_block_t efs_map_block(struct inode *inode, efs_block_t block) {
 200         struct efs_sb_info    *sb = SUPER_INFO(inode->i_sb);
 201         struct efs_inode_info *in = INODE_INFO(inode);
 202         struct buffer_head    *bh = NULL;
 203 
 204         int cur, last, first = 1;
 205         int ibase, ioffset, dirext, direxts, indext, indexts;
 206         efs_block_t iblock, result = 0, lastblock = 0;
 207         efs_extent ext, *exts;
 208 
 209         last = in->lastextent;
 210 
 211         if (in->numextents <= EFS_DIRECTEXTENTS) {
 212                 /* first check the last extent we returned */
 213                 if ((result = efs_extent_check(&in->extents[last], block, sb)))
 214                         return result;
 215     
 216                 /* if we only have one extent then nothing can be found */
 217                 if (in->numextents == 1) {
 218                         pr_err("%s() failed to map (1 extent)\n", __func__);
 219                         return 0;
 220                 }
 221 
 222                 direxts = in->numextents;
 223 
 224                 /*
 225                  * check the stored extents in the inode
 226                  * start with next extent and check forwards
 227                  */
 228                 for(dirext = 1; dirext < direxts; dirext++) {
 229                         cur = (last + dirext) % in->numextents;
 230                         if ((result = efs_extent_check(&in->extents[cur], block, sb))) {
 231                                 in->lastextent = cur;
 232                                 return result;
 233                         }
 234                 }
 235 
 236                 pr_err("%s() failed to map block %u (dir)\n", __func__, block);
 237                 return 0;
 238         }
 239 
 240         pr_debug("%s(): indirect search for logical block %u\n",
 241                  __func__, block);
 242         direxts = in->extents[0].cooked.ex_offset;
 243         indexts = in->numextents;
 244 
 245         for(indext = 0; indext < indexts; indext++) {
 246                 cur = (last + indext) % indexts;
 247 
 248                 /*
 249                  * work out which direct extent contains `cur'.
 250                  *
 251                  * also compute ibase: i.e. the number of the first
 252                  * indirect extent contained within direct extent `cur'.
 253                  *
 254                  */
 255                 ibase = 0;
 256                 for(dirext = 0; cur < ibase && dirext < direxts; dirext++) {
 257                         ibase += in->extents[dirext].cooked.ex_length *
 258                                 (EFS_BLOCKSIZE / sizeof(efs_extent));
 259                 }
 260 
 261                 if (dirext == direxts) {
 262                         /* should never happen */
 263                         pr_err("couldn't find direct extent for indirect extent %d (block %u)\n",
 264                                cur, block);
 265                         if (bh) brelse(bh);
 266                         return 0;
 267                 }
 268                 
 269                 /* work out block number and offset of this indirect extent */
 270                 iblock = sb->fs_start + in->extents[dirext].cooked.ex_bn +
 271                         (cur - ibase) /
 272                         (EFS_BLOCKSIZE / sizeof(efs_extent));
 273                 ioffset = (cur - ibase) %
 274                         (EFS_BLOCKSIZE / sizeof(efs_extent));
 275 
 276                 if (first || lastblock != iblock) {
 277                         if (bh) brelse(bh);
 278 
 279                         bh = sb_bread(inode->i_sb, iblock);
 280                         if (!bh) {
 281                                 pr_err("%s() failed at block %d\n",
 282                                        __func__, iblock);
 283                                 return 0;
 284                         }
 285                         pr_debug("%s(): read indirect extent block %d\n",
 286                                  __func__, iblock);
 287                         first = 0;
 288                         lastblock = iblock;
 289                 }
 290 
 291                 exts = (efs_extent *) bh->b_data;
 292 
 293                 extent_copy(&(exts[ioffset]), &ext);
 294 
 295                 if (ext.cooked.ex_magic != 0) {
 296                         pr_err("extent %d has bad magic number in block %d\n",
 297                                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         pr_err("%s() failed to map block %u (indir)\n", __func__, block);
 310         return 0;
 311 }  
 312 
 313 MODULE_LICENSE("GPL");