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/buffer_head.h>
11 #include <linux/module.h>
12 #include <linux/fs.h>
13 #include "efs.h"
14 #include <linux/efs_fs_sb.h>
15 
efs_readpage(struct file * file,struct page * page)16 static int efs_readpage(struct file *file, struct page *page)
17 {
18 	return block_read_full_page(page,efs_get_block);
19 }
_efs_bmap(struct address_space * mapping,sector_t block)20 static sector_t _efs_bmap(struct address_space *mapping, sector_t block)
21 {
22 	return generic_block_bmap(mapping,block,efs_get_block);
23 }
24 static const struct address_space_operations efs_aops = {
25 	.readpage = efs_readpage,
26 	.bmap = _efs_bmap
27 };
28 
extent_copy(efs_extent * src,efs_extent * dst)29 static inline void extent_copy(efs_extent *src, efs_extent *dst) {
30 	/*
31 	 * this is slightly evil. it doesn't just copy
32 	 * efs_extent from src to dst, it also mangles
33 	 * the bits so that dst ends up in cpu byte-order.
34 	 */
35 
36 	dst->cooked.ex_magic  =  (unsigned int) src->raw[0];
37 	dst->cooked.ex_bn     = ((unsigned int) src->raw[1] << 16) |
38 				((unsigned int) src->raw[2] <<  8) |
39 				((unsigned int) src->raw[3] <<  0);
40 	dst->cooked.ex_length =  (unsigned int) src->raw[4];
41 	dst->cooked.ex_offset = ((unsigned int) src->raw[5] << 16) |
42 				((unsigned int) src->raw[6] <<  8) |
43 				((unsigned int) src->raw[7] <<  0);
44 	return;
45 }
46 
efs_iget(struct super_block * super,unsigned long ino)47 struct inode *efs_iget(struct super_block *super, unsigned long ino)
48 {
49 	int i, inode_index;
50 	dev_t device;
51 	u32 rdev;
52 	struct buffer_head *bh;
53 	struct efs_sb_info    *sb = SUPER_INFO(super);
54 	struct efs_inode_info *in;
55 	efs_block_t block, offset;
56 	struct efs_dinode *efs_inode;
57 	struct inode *inode;
58 
59 	inode = iget_locked(super, ino);
60 	if (IS_ERR(inode))
61 		return ERR_PTR(-ENOMEM);
62 	if (!(inode->i_state & I_NEW))
63 		return inode;
64 
65 	in = INODE_INFO(inode);
66 
67 	/*
68 	** EFS layout:
69 	**
70 	** |   cylinder group    |   cylinder group    |   cylinder group ..etc
71 	** |inodes|data          |inodes|data          |inodes|data       ..etc
72 	**
73 	** work out the inode block index, (considering initially that the
74 	** inodes are stored as consecutive blocks). then work out the block
75 	** number of that inode given the above layout, and finally the
76 	** offset of the inode within that block.
77 	*/
78 
79 	inode_index = inode->i_ino /
80 		(EFS_BLOCKSIZE / sizeof(struct efs_dinode));
81 
82 	block = sb->fs_start + sb->first_block +
83 		(sb->group_size * (inode_index / sb->inode_blocks)) +
84 		(inode_index % sb->inode_blocks);
85 
86 	offset = (inode->i_ino %
87 			(EFS_BLOCKSIZE / sizeof(struct efs_dinode))) *
88 		sizeof(struct efs_dinode);
89 
90 	bh = sb_bread(inode->i_sb, block);
91 	if (!bh) {
92 		printk(KERN_WARNING "EFS: bread() failed at block %d\n", block);
93 		goto read_inode_error;
94 	}
95 
96 	efs_inode = (struct efs_dinode *) (bh->b_data + offset);
97 
98 	inode->i_mode  = be16_to_cpu(efs_inode->di_mode);
99 	set_nlink(inode, be16_to_cpu(efs_inode->di_nlink));
100 	inode->i_uid   = (uid_t)be16_to_cpu(efs_inode->di_uid);
101 	inode->i_gid   = (gid_t)be16_to_cpu(efs_inode->di_gid);
102 	inode->i_size  = be32_to_cpu(efs_inode->di_size);
103 	inode->i_atime.tv_sec = be32_to_cpu(efs_inode->di_atime);
104 	inode->i_mtime.tv_sec = be32_to_cpu(efs_inode->di_mtime);
105 	inode->i_ctime.tv_sec = be32_to_cpu(efs_inode->di_ctime);
106 	inode->i_atime.tv_nsec = inode->i_mtime.tv_nsec = inode->i_ctime.tv_nsec = 0;
107 
108 	/* this is the number of blocks in the file */
109 	if (inode->i_size == 0) {
110 		inode->i_blocks = 0;
111 	} else {
112 		inode->i_blocks = ((inode->i_size - 1) >> EFS_BLOCKSIZE_BITS) + 1;
113 	}
114 
115 	rdev = be16_to_cpu(efs_inode->di_u.di_dev.odev);
116 	if (rdev == 0xffff) {
117 		rdev = be32_to_cpu(efs_inode->di_u.di_dev.ndev);
118 		if (sysv_major(rdev) > 0xfff)
119 			device = 0;
120 		else
121 			device = MKDEV(sysv_major(rdev), sysv_minor(rdev));
122 	} else
123 		device = old_decode_dev(rdev);
124 
125 	/* get the number of extents for this object */
126 	in->numextents = be16_to_cpu(efs_inode->di_numextents);
127 	in->lastextent = 0;
128 
129 	/* copy the extents contained within the inode to memory */
130 	for(i = 0; i < EFS_DIRECTEXTENTS; i++) {
131 		extent_copy(&(efs_inode->di_u.di_extents[i]), &(in->extents[i]));
132 		if (i < in->numextents && in->extents[i].cooked.ex_magic != 0) {
133 			printk(KERN_WARNING "EFS: extent %d has bad magic number in inode %lu\n", i, inode->i_ino);
134 			brelse(bh);
135 			goto read_inode_error;
136 		}
137 	}
138 
139 	brelse(bh);
140 
141 #ifdef DEBUG
142 	printk(KERN_DEBUG "EFS: efs_iget(): inode %lu, extents %d, mode %o\n",
143 		inode->i_ino, in->numextents, inode->i_mode);
144 #endif
145 
146 	switch (inode->i_mode & S_IFMT) {
147 		case S_IFDIR:
148 			inode->i_op = &efs_dir_inode_operations;
149 			inode->i_fop = &efs_dir_operations;
150 			break;
151 		case S_IFREG:
152 			inode->i_fop = &generic_ro_fops;
153 			inode->i_data.a_ops = &efs_aops;
154 			break;
155 		case S_IFLNK:
156 			inode->i_op = &page_symlink_inode_operations;
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 			printk(KERN_WARNING "EFS: 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 	printk(KERN_WARNING "EFS: 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
efs_extent_check(efs_extent * ptr,efs_block_t block,struct efs_sb_info * sb)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 
efs_map_block(struct inode * inode,efs_block_t block)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 			printk(KERN_ERR "EFS: map_block() failed to map (1 extent)\n");
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 		printk(KERN_ERR "EFS: map_block() failed to map block %u (dir)\n", block);
238 		return 0;
239 	}
240 
241 #ifdef DEBUG
242 	printk(KERN_DEBUG "EFS: map_block(): indirect search for logical block %u\n", block);
243 #endif
244 	direxts = in->extents[0].cooked.ex_offset;
245 	indexts = in->numextents;
246 
247 	for(indext = 0; indext < indexts; indext++) {
248 		cur = (last + indext) % indexts;
249 
250 		/*
251 		 * work out which direct extent contains `cur'.
252 		 *
253 		 * also compute ibase: i.e. the number of the first
254 		 * indirect extent contained within direct extent `cur'.
255 		 *
256 		 */
257 		ibase = 0;
258 		for(dirext = 0; cur < ibase && dirext < direxts; dirext++) {
259 			ibase += in->extents[dirext].cooked.ex_length *
260 				(EFS_BLOCKSIZE / sizeof(efs_extent));
261 		}
262 
263 		if (dirext == direxts) {
264 			/* should never happen */
265 			printk(KERN_ERR "EFS: couldn't find direct extent for indirect extent %d (block %u)\n", 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 				printk(KERN_ERR "EFS: bread() failed at block %d\n", iblock);
283 				return 0;
284 			}
285 #ifdef DEBUG
286 			printk(KERN_DEBUG "EFS: map_block(): read indirect extent block %d\n", iblock);
287 #endif
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 			printk(KERN_ERR "EFS: extent %d has bad magic number in block %d\n", 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 	printk(KERN_ERR "EFS: map_block() failed to map block %u (indir)\n", block);
310 	return 0;
311 }
312 
313 MODULE_LICENSE("GPL");
314