fs/efs/inode.c

   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_read_folio(struct file *file, struct folio *folio)
  18 {
  19         return block_read_full_folio(folio, efs_get_block);
  20 }
  21
  22 static sector_t _efs_bmap(struct address_space *mapping, sector_t block)
  23 {
  24         return generic_block_bmap(mapping,block,efs_get_block);
  25 }
  26
  27 static const struct address_space_operations efs_aops = {
  28         .read_folio = efs_read_folio,
  29         .bmap = _efs_bmap
  30 };
  31
  32 static inline void extent_copy(efs_extent *src, efs_extent *dst) {
  33         /*
  34          * this is slightly evil. it doesn't just copy
  35          * efs_extent from src to dst, it also mangles
  36          * the bits so that dst ends up in cpu byte-order.
  37          */
  38
  39         dst->cooked.ex_magic  =  (unsigned int) src->raw[0];
  40         dst->cooked.ex_bn     = ((unsigned int) src->raw[1] << 16) |
  41                                 ((unsigned int) src->raw[2] <<  8) |
  42                                 ((unsigned int) src->raw[3] <<  0);
  43         dst->cooked.ex_length =  (unsigned int) src->raw[4];
  44         dst->cooked.ex_offset = ((unsigned int) src->raw[5] << 16) |
  45                                 ((unsigned int) src->raw[6] <<  8) |
  46                                 ((unsigned int) src->raw[7] <<  0);
  47         return;
  48 }
  49
  50 struct inode *efs_iget(struct super_block *super, unsigned long ino)
  51 {
  52         int i, inode_index;
  53         dev_t device;
  54         u32 rdev;
  55         struct buffer_head *bh;
  56         struct efs_sb_info    *sb = SUPER_INFO(super);
  57         struct efs_inode_info *in;
  58         efs_block_t block, offset;
  59         struct efs_dinode *efs_inode;
  60         struct inode *inode;
  61
  62         inode = iget_locked(super, ino);
  63         if (!inode)
  64                 return ERR_PTR(-ENOMEM);
  65         if (!(inode->i_state & I_NEW))
  66                 return inode;
  67
  68         in = INODE_INFO(inode);
  69
  70         /*
  71         ** EFS layout:
  72         **
  73         ** |   cylinder group    |   cylinder group    |   cylinder group ..etc
  74         ** |inodes|data          |inodes|data          |inodes|data       ..etc
  75         **
  76         ** work out the inode block index, (considering initially that the
  77         ** inodes are stored as consecutive blocks). then work out the block
  78         ** number of that inode given the above layout, and finally the
  79         ** offset of the inode within that block.
  80         */
  81
  82         inode_index = inode->i_ino /
  83                 (EFS_BLOCKSIZE / sizeof(struct efs_dinode));
  84
  85         block = sb->fs_start + sb->first_block +
  86                 (sb->group_size * (inode_index / sb->inode_blocks)) +
  87                 (inode_index % sb->inode_blocks);
  88
  89         offset = (inode->i_ino %
  90                         (EFS_BLOCKSIZE / sizeof(struct efs_dinode))) *
  91                 sizeof(struct efs_dinode);
  92
  93         bh = sb_bread(inode->i_sb, block);
  94         if (!bh) {
  95                 pr_warn("%s() failed at block %d\n", __func__, block);
  96                 goto read_inode_error;
  97         }
  98
  99         efs_inode = (struct efs_dinode *) (bh->b_data + offset);
 100
 101         inode->i_mode  = be16_to_cpu(efs_inode->di_mode);
 102         set_nlink(inode, be16_to_cpu(efs_inode->di_nlink));
 103         i_uid_write(inode, (uid_t)be16_to_cpu(efs_inode->di_uid));
 104         i_gid_write(inode, (gid_t)be16_to_cpu(efs_inode->di_gid));
 105         inode->i_size  = be32_to_cpu(efs_inode->di_size);
 106         inode_set_atime(inode, be32_to_cpu(efs_inode->di_atime), 0);
 107         inode_set_mtime(inode, be32_to_cpu(efs_inode->di_mtime), 0);
 108         inode_set_ctime(inode, be32_to_cpu(efs_inode->di_ctime), 0);
 109
 110         /* this is the number of blocks in the file */
 111         if (inode->i_size == 0) {
 112                 inode->i_blocks = 0;
 113         } else {
 114                 inode->i_blocks = ((inode->i_size - 1) >> EFS_BLOCKSIZE_BITS) + 1;
 115         }
 116
 117         rdev = be16_to_cpu(efs_inode->di_u.di_dev.odev);
 118         if (rdev == 0xffff) {
 119                 rdev = be32_to_cpu(efs_inode->di_u.di_dev.ndev);
 120                 if (sysv_major(rdev) > 0xfff)
 121                         device = 0;
 122                 else
 123                         device = MKDEV(sysv_major(rdev), sysv_minor(rdev));
 124         } else
 125                 device = old_decode_dev(rdev);
 126
 127         /* get the number of extents for this object */
 128         in->numextents = be16_to_cpu(efs_inode->di_numextents);
 129         in->lastextent = 0;
 130
 131         /* copy the extents contained within the inode to memory */
 132         for(i = 0; i < EFS_DIRECTEXTENTS; i++) {
 133                 extent_copy(&(efs_inode->di_u.di_extents[i]), &(in->extents[i]));
 134                 if (i < in->numextents && in->extents[i].cooked.ex_magic != 0) {
 135                         pr_warn("extent %d has bad magic number in inode %lu\n",
 136                                 i, inode->i_ino);
 137                         brelse(bh);
 138                         goto read_inode_error;
 139                 }
 140         }
 141
 142         brelse(bh);
 143         pr_debug("efs_iget(): inode %lu, extents %d, mode %o\n",
 144                  inode->i_ino, in->numextents, inode->i_mode);
 145         switch (inode->i_mode & S_IFMT) {
 146                 case S_IFDIR:
 147                         inode->i_op = &efs_dir_inode_operations;
 148                         inode->i_fop = &efs_dir_operations;
 149                         break;
 150                 case S_IFREG:
 151                         inode->i_fop = &generic_ro_fops;
 152                         inode->i_data.a_ops = &efs_aops;
 153                         break;
 154                 case S_IFLNK:
 155                         inode->i_op = &page_symlink_inode_operations;
 156                         inode_nohighmem(inode);
 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                         pr_warn("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
 173 read_inode_error:
 174         pr_warn("failed to read inode %lu\n", inode->i_ino);
 175         iget_failed(inode);
 176         return ERR_PTR(-EIO);
 177 }
 178
 179 static inline efs_block_t
 180 efs_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
 200 efs_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                         pr_err("%s() failed to map (1 extent)\n", __func__);
 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                 pr_err("%s() failed to map block %u (dir)\n", __func__, block);
 238                 return 0;
 239         }
 240
 241         pr_debug("%s(): indirect search for logical block %u\n",
 242                  __func__, block);
 243         direxts = in->extents[0].cooked.ex_offset;
 244         indexts = in->numextents;
 245
 246         for(indext = 0; indext < indexts; indext++) {
 247                 cur = (last + indext) % indexts;
 248
 249                 /*
 250                  * work out which direct extent contains `cur'.
 251                  *
 252                  * also compute ibase: i.e. the number of the first
 253                  * indirect extent contained within direct extent `cur'.
 254                  *
 255                  */
 256                 ibase = 0;
 257                 for(dirext = 0; cur < ibase && dirext < direxts; dirext++) {
 258                         ibase += in->extents[dirext].cooked.ex_length *
 259                                 (EFS_BLOCKSIZE / sizeof(efs_extent));
 260                 }
 261
 262                 if (dirext == direxts) {
 263                         /* should never happen */
 264                         pr_err("couldn't find direct extent for indirect extent %d (block %u)\n",
 265                                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                                 pr_err("%s() failed at block %d\n",
 283                                        __func__, iblock);
 284                                 return 0;
 285                         }
 286                         pr_debug("%s(): read indirect extent block %d\n",
 287                                  __func__, iblock);
 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                         pr_err("extent %d has bad magic number in block %d\n",
 298                                cur, iblock);
 299                         if (bh) brelse(bh);
 300                         return 0;
 301                 }
 302
 303                 if ((result = efs_extent_check(&ext, block, sb))) {
 304                         if (bh) brelse(bh);
 305                         in->lastextent = cur;
 306                         return result;
 307                 }
 308         }
 309         if (bh) brelse(bh);
 310         pr_err("%s() failed to map block %u (indir)\n", __func__, block);
 311         return 0;
 312 }
 313
 314 MODULE_DESCRIPTION("Extent File System (efs)");
 315 MODULE_LICENSE("GPL");