fs/efs/inode.c

0001 // SPDX-License-Identifier: GPL-2.0-only
0002 /*
0003  * inode.c
0004  *
0005  * Copyright (c) 1999 Al Smith
0006  *
0007  * Portions derived from work (c) 1995,1996 Christian Vogelgsang,
0008  *              and from work (c) 1998 Mike Shaver.
0009  */
0010
0011 #include <linux/buffer_head.h>
0012 #include <linux/module.h>
0013 #include <linux/fs.h>
0014 #include "efs.h"
0015 #include <linux/efs_fs_sb.h>
0016
0017 static int efs_read_folio(struct file *file, struct folio *folio)
0018 {
0019     return block_read_full_folio(folio, efs_get_block);
0020 }
0021
0022 static sector_t _efs_bmap(struct address_space *mapping, sector_t block)
0023 {
0024     return generic_block_bmap(mapping,block,efs_get_block);
0025 }
0026
0027 static const struct address_space_operations efs_aops = {
0028     .read_folio = efs_read_folio,
0029     .bmap = _efs_bmap
0030 };
0031
0032 static inline void extent_copy(efs_extent *src, efs_extent *dst) {
0033     /*
0034      * this is slightly evil. it doesn't just copy
0035      * efs_extent from src to dst, it also mangles
0036      * the bits so that dst ends up in cpu byte-order.
0037      */
0038
0039     dst->cooked.ex_magic  =  (unsigned int) src->raw[0];
0040     dst->cooked.ex_bn     = ((unsigned int) src->raw[1] << 16) |
0041                 ((unsigned int) src->raw[2] <<  8) |
0042                 ((unsigned int) src->raw[3] <<  0);
0043     dst->cooked.ex_length =  (unsigned int) src->raw[4];
0044     dst->cooked.ex_offset = ((unsigned int) src->raw[5] << 16) |
0045                 ((unsigned int) src->raw[6] <<  8) |
0046                 ((unsigned int) src->raw[7] <<  0);
0047     return;
0048 }
0049
0050 struct inode *efs_iget(struct super_block *super, unsigned long ino)
0051 {
0052     int i, inode_index;
0053     dev_t device;
0054     u32 rdev;
0055     struct buffer_head *bh;
0056     struct efs_sb_info    *sb = SUPER_INFO(super);
0057     struct efs_inode_info *in;
0058     efs_block_t block, offset;
0059     struct efs_dinode *efs_inode;
0060     struct inode *inode;
0061
0062     inode = iget_locked(super, ino);
0063     if (!inode)
0064         return ERR_PTR(-ENOMEM);
0065     if (!(inode->i_state & I_NEW))
0066         return inode;
0067
0068     in = INODE_INFO(inode);
0069
0070     /*
0071     ** EFS layout:
0072     **
0073     ** |   cylinder group    |   cylinder group    |   cylinder group ..etc
0074     ** |inodes|data          |inodes|data          |inodes|data       ..etc
0075     **
0076     ** work out the inode block index, (considering initially that the
0077     ** inodes are stored as consecutive blocks). then work out the block
0078     ** number of that inode given the above layout, and finally the
0079     ** offset of the inode within that block.
0080     */
0081
0082     inode_index = inode->i_ino /
0083         (EFS_BLOCKSIZE / sizeof(struct efs_dinode));
0084
0085     block = sb->fs_start + sb->first_block +
0086         (sb->group_size * (inode_index / sb->inode_blocks)) +
0087         (inode_index % sb->inode_blocks);
0088
0089     offset = (inode->i_ino %
0090             (EFS_BLOCKSIZE / sizeof(struct efs_dinode))) *
0091         sizeof(struct efs_dinode);
0092
0093     bh = sb_bread(inode->i_sb, block);
0094     if (!bh) {
0095         pr_warn("%s() failed at block %d\n", __func__, block);
0096         goto read_inode_error;
0097     }
0098
0099     efs_inode = (struct efs_dinode *) (bh->b_data + offset);
0100
0101     inode->i_mode  = be16_to_cpu(efs_inode->di_mode);
0102     set_nlink(inode, be16_to_cpu(efs_inode->di_nlink));
0103     i_uid_write(inode, (uid_t)be16_to_cpu(efs_inode->di_uid));
0104     i_gid_write(inode, (gid_t)be16_to_cpu(efs_inode->di_gid));
0105     inode->i_size  = be32_to_cpu(efs_inode->di_size);
0106     inode->i_atime.tv_sec = be32_to_cpu(efs_inode->di_atime);
0107     inode->i_mtime.tv_sec = be32_to_cpu(efs_inode->di_mtime);
0108     inode->i_ctime.tv_sec = be32_to_cpu(efs_inode->di_ctime);
0109     inode->i_atime.tv_nsec = inode->i_mtime.tv_nsec = inode->i_ctime.tv_nsec = 0;
0110
0111     /* this is the number of blocks in the file */
0112     if (inode->i_size == 0) {
0113         inode->i_blocks = 0;
0114     } else {
0115         inode->i_blocks = ((inode->i_size - 1) >> EFS_BLOCKSIZE_BITS) + 1;
0116     }
0117
0118     rdev = be16_to_cpu(efs_inode->di_u.di_dev.odev);
0119     if (rdev == 0xffff) {
0120         rdev = be32_to_cpu(efs_inode->di_u.di_dev.ndev);
0121         if (sysv_major(rdev) > 0xfff)
0122             device = 0;
0123         else
0124             device = MKDEV(sysv_major(rdev), sysv_minor(rdev));
0125     } else
0126         device = old_decode_dev(rdev);
0127
0128     /* get the number of extents for this object */
0129     in->numextents = be16_to_cpu(efs_inode->di_numextents);
0130     in->lastextent = 0;
0131
0132     /* copy the extents contained within the inode to memory */
0133     for(i = 0; i < EFS_DIRECTEXTENTS; i++) {
0134         extent_copy(&(efs_inode->di_u.di_extents[i]), &(in->extents[i]));
0135         if (i < in->numextents && in->extents[i].cooked.ex_magic != 0) {
0136             pr_warn("extent %d has bad magic number in inode %lu\n",
0137                 i, inode->i_ino);
0138             brelse(bh);
0139             goto read_inode_error;
0140         }
0141     }
0142
0143     brelse(bh);
0144     pr_debug("efs_iget(): inode %lu, extents %d, mode %o\n",
0145          inode->i_ino, in->numextents, inode->i_mode);
0146     switch (inode->i_mode & S_IFMT) {
0147         case S_IFDIR:
0148             inode->i_op = &efs_dir_inode_operations;
0149             inode->i_fop = &efs_dir_operations;
0150             break;
0151         case S_IFREG:
0152             inode->i_fop = &generic_ro_fops;
0153             inode->i_data.a_ops = &efs_aops;
0154             break;
0155         case S_IFLNK:
0156             inode->i_op = &page_symlink_inode_operations;
0157             inode_nohighmem(inode);
0158             inode->i_data.a_ops = &efs_symlink_aops;
0159             break;
0160         case S_IFCHR:
0161         case S_IFBLK:
0162         case S_IFIFO:
0163             init_special_inode(inode, inode->i_mode, device);
0164             break;
0165         default:
0166             pr_warn("unsupported inode mode %o\n", inode->i_mode);
0167             goto read_inode_error;
0168             break;
0169     }
0170
0171     unlock_new_inode(inode);
0172     return inode;
0173
0174 read_inode_error:
0175     pr_warn("failed to read inode %lu\n", inode->i_ino);
0176     iget_failed(inode);
0177     return ERR_PTR(-EIO);
0178 }
0179
0180 static inline efs_block_t
0181 efs_extent_check(efs_extent *ptr, efs_block_t block, struct efs_sb_info *sb) {
0182     efs_block_t start;
0183     efs_block_t length;
0184     efs_block_t offset;
0185
0186     /*
0187      * given an extent and a logical block within a file,
0188      * can this block be found within this extent ?
0189      */
0190     start  = ptr->cooked.ex_bn;
0191     length = ptr->cooked.ex_length;
0192     offset = ptr->cooked.ex_offset;
0193
0194     if ((block >= offset) && (block < offset+length)) {
0195         return(sb->fs_start + start + block - offset);
0196     } else {
0197         return 0;
0198     }
0199 }
0200
0201 efs_block_t efs_map_block(struct inode *inode, efs_block_t block) {
0202     struct efs_sb_info    *sb = SUPER_INFO(inode->i_sb);
0203     struct efs_inode_info *in = INODE_INFO(inode);
0204     struct buffer_head    *bh = NULL;
0205
0206     int cur, last, first = 1;
0207     int ibase, ioffset, dirext, direxts, indext, indexts;
0208     efs_block_t iblock, result = 0, lastblock = 0;
0209     efs_extent ext, *exts;
0210
0211     last = in->lastextent;
0212
0213     if (in->numextents <= EFS_DIRECTEXTENTS) {
0214         /* first check the last extent we returned */
0215         if ((result = efs_extent_check(&in->extents[last], block, sb)))
0216             return result;
0217
0218         /* if we only have one extent then nothing can be found */
0219         if (in->numextents == 1) {
0220             pr_err("%s() failed to map (1 extent)\n", __func__);
0221             return 0;
0222         }
0223
0224         direxts = in->numextents;
0225
0226         /*
0227          * check the stored extents in the inode
0228          * start with next extent and check forwards
0229          */
0230         for(dirext = 1; dirext < direxts; dirext++) {
0231             cur = (last + dirext) % in->numextents;
0232             if ((result = efs_extent_check(&in->extents[cur], block, sb))) {
0233                 in->lastextent = cur;
0234                 return result;
0235             }
0236         }
0237
0238         pr_err("%s() failed to map block %u (dir)\n", __func__, block);
0239         return 0;
0240     }
0241
0242     pr_debug("%s(): indirect search for logical block %u\n",
0243          __func__, block);
0244     direxts = in->extents[0].cooked.ex_offset;
0245     indexts = in->numextents;
0246
0247     for(indext = 0; indext < indexts; indext++) {
0248         cur = (last + indext) % indexts;
0249
0250         /*
0251          * work out which direct extent contains `cur'.
0252          *
0253          * also compute ibase: i.e. the number of the first
0254          * indirect extent contained within direct extent `cur'.
0255          *
0256          */
0257         ibase = 0;
0258         for(dirext = 0; cur < ibase && dirext < direxts; dirext++) {
0259             ibase += in->extents[dirext].cooked.ex_length *
0260                 (EFS_BLOCKSIZE / sizeof(efs_extent));
0261         }
0262
0263         if (dirext == direxts) {
0264             /* should never happen */
0265             pr_err("couldn't find direct extent for indirect extent %d (block %u)\n",
0266                    cur, block);
0267             if (bh) brelse(bh);
0268             return 0;
0269         }
0270
0271         /* work out block number and offset of this indirect extent */
0272         iblock = sb->fs_start + in->extents[dirext].cooked.ex_bn +
0273             (cur - ibase) /
0274             (EFS_BLOCKSIZE / sizeof(efs_extent));
0275         ioffset = (cur - ibase) %
0276             (EFS_BLOCKSIZE / sizeof(efs_extent));
0277
0278         if (first || lastblock != iblock) {
0279             if (bh) brelse(bh);
0280
0281             bh = sb_bread(inode->i_sb, iblock);
0282             if (!bh) {
0283                 pr_err("%s() failed at block %d\n",
0284                        __func__, iblock);
0285                 return 0;
0286             }
0287             pr_debug("%s(): read indirect extent block %d\n",
0288                  __func__, iblock);
0289             first = 0;
0290             lastblock = iblock;
0291         }
0292
0293         exts = (efs_extent *) bh->b_data;
0294
0295         extent_copy(&(exts[ioffset]), &ext);
0296
0297         if (ext.cooked.ex_magic != 0) {
0298             pr_err("extent %d has bad magic number in block %d\n",
0299                    cur, iblock);
0300             if (bh) brelse(bh);
0301             return 0;
0302         }
0303
0304         if ((result = efs_extent_check(&ext, block, sb))) {
0305             if (bh) brelse(bh);
0306             in->lastextent = cur;
0307             return result;
0308         }
0309     }
0310     if (bh) brelse(bh);
0311     pr_err("%s() failed to map block %u (indir)\n", __func__, block);
0312     return 0;
0313 }
0314
0315 MODULE_LICENSE("GPL");