xref: /kernel/linux/linux-5.10/fs/efs/inode.c (revision 8c2ecf20) 
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
17static int efs_readpage(struct file *file, struct page *page)
18{
19	return block_read_full_page(page,efs_get_block);
20}
21static sector_t _efs_bmap(struct address_space *mapping, sector_t block)
22{
23	return generic_block_bmap(mapping,block,efs_get_block);
24}
25static const struct address_space_operations efs_aops = {
26	.readpage = efs_readpage,
27	.bmap = _efs_bmap
28};
29
30static 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
48struct 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
172read_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
178static inline efs_block_t
179efs_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
199efs_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
313MODULE_LICENSE("GPL");
314