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_read_folio(struct file *file, struct folio *folio)
18{
19	return block_read_full_folio(folio, efs_get_block);
20}
21
22static sector_t _efs_bmap(struct address_space *mapping, sector_t block)
23{
24	return generic_block_bmap(mapping,block,efs_get_block);
25}
26
27static const struct address_space_operations efs_aops = {
28	.read_folio = efs_read_folio,
29	.bmap = _efs_bmap
30};
31
32static 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
50struct 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
173read_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
179static inline efs_block_t
180efs_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
200efs_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
314MODULE_LICENSE("GPL");
315