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 
efs_readpage(struct file * file,struct page * page)17 static int efs_readpage(struct file *file, struct page *page)
18 {
19 	return block_read_full_page(page,efs_get_block);
20 }
_efs_bmap(struct address_space * mapping,sector_t block)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 
extent_copy(efs_extent * src,efs_extent * dst)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 
efs_iget(struct super_block * super,unsigned long ino)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
efs_extent_check(efs_extent * ptr,efs_block_t block,struct efs_sb_info * sb)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 
efs_map_block(struct inode * inode,efs_block_t block)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");
314