xref: /kernel/linux/linux-6.6/fs/efs/inode.c (revision 62306a36) 
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->i_atime.tv_sec = be32_to_cpu(efs_inode->di_atime);
107	inode->i_mtime.tv_sec = be32_to_cpu(efs_inode->di_mtime);
108	inode_set_ctime(inode, be32_to_cpu(efs_inode->di_ctime), 0);
109	inode->i_atime.tv_nsec = inode->i_mtime.tv_nsec = 0;
110
111	/* this is the number of blocks in the file */
112	if (inode->i_size == 0) {
113		inode->i_blocks = 0;
114	} else {
115		inode->i_blocks = ((inode->i_size - 1) >> EFS_BLOCKSIZE_BITS) + 1;
116	}
117
118	rdev = be16_to_cpu(efs_inode->di_u.di_dev.odev);
119	if (rdev == 0xffff) {
120		rdev = be32_to_cpu(efs_inode->di_u.di_dev.ndev);
121		if (sysv_major(rdev) > 0xfff)
122			device = 0;
123		else
124			device = MKDEV(sysv_major(rdev), sysv_minor(rdev));
125	} else
126		device = old_decode_dev(rdev);
127
128	/* get the number of extents for this object */
129	in->numextents = be16_to_cpu(efs_inode->di_numextents);
130	in->lastextent = 0;
131
132	/* copy the extents contained within the inode to memory */
133	for(i = 0; i < EFS_DIRECTEXTENTS; i++) {
134		extent_copy(&(efs_inode->di_u.di_extents[i]), &(in->extents[i]));
135		if (i < in->numextents && in->extents[i].cooked.ex_magic != 0) {
136			pr_warn("extent %d has bad magic number in inode %lu\n",
137				i, inode->i_ino);
138			brelse(bh);
139			goto read_inode_error;
140		}
141	}
142
143	brelse(bh);
144	pr_debug("efs_iget(): inode %lu, extents %d, mode %o\n",
145		 inode->i_ino, in->numextents, inode->i_mode);
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_nohighmem(inode);
158			inode->i_data.a_ops = &efs_symlink_aops;
159			break;
160		case S_IFCHR:
161		case S_IFBLK:
162		case S_IFIFO:
163			init_special_inode(inode, inode->i_mode, device);
164			break;
165		default:
166			pr_warn("unsupported inode mode %o\n", inode->i_mode);
167			goto read_inode_error;
168			break;
169	}
170
171	unlock_new_inode(inode);
172	return inode;
173
174read_inode_error:
175	pr_warn("failed to read inode %lu\n", inode->i_ino);
176	iget_failed(inode);
177	return ERR_PTR(-EIO);
178}
179
180static inline efs_block_t
181efs_extent_check(efs_extent *ptr, efs_block_t block, struct efs_sb_info *sb) {
182	efs_block_t start;
183	efs_block_t length;
184	efs_block_t offset;
185
186	/*
187	 * given an extent and a logical block within a file,
188	 * can this block be found within this extent ?
189	 */
190	start  = ptr->cooked.ex_bn;
191	length = ptr->cooked.ex_length;
192	offset = ptr->cooked.ex_offset;
193
194	if ((block >= offset) && (block < offset+length)) {
195		return(sb->fs_start + start + block - offset);
196	} else {
197		return 0;
198	}
199}
200
201efs_block_t efs_map_block(struct inode *inode, efs_block_t block) {
202	struct efs_sb_info    *sb = SUPER_INFO(inode->i_sb);
203	struct efs_inode_info *in = INODE_INFO(inode);
204	struct buffer_head    *bh = NULL;
205
206	int cur, last, first = 1;
207	int ibase, ioffset, dirext, direxts, indext, indexts;
208	efs_block_t iblock, result = 0, lastblock = 0;
209	efs_extent ext, *exts;
210
211	last = in->lastextent;
212
213	if (in->numextents <= EFS_DIRECTEXTENTS) {
214		/* first check the last extent we returned */
215		if ((result = efs_extent_check(&in->extents[last], block, sb)))
216			return result;
217
218		/* if we only have one extent then nothing can be found */
219		if (in->numextents == 1) {
220			pr_err("%s() failed to map (1 extent)\n", __func__);
221			return 0;
222		}
223
224		direxts = in->numextents;
225
226		/*
227		 * check the stored extents in the inode
228		 * start with next extent and check forwards
229		 */
230		for(dirext = 1; dirext < direxts; dirext++) {
231			cur = (last + dirext) % in->numextents;
232			if ((result = efs_extent_check(&in->extents[cur], block, sb))) {
233				in->lastextent = cur;
234				return result;
235			}
236		}
237
238		pr_err("%s() failed to map block %u (dir)\n", __func__, block);
239		return 0;
240	}
241
242	pr_debug("%s(): indirect search for logical block %u\n",
243		 __func__, block);
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			pr_err("couldn't find direct extent for indirect extent %d (block %u)\n",
266			       cur, block);
267			if (bh) brelse(bh);
268			return 0;
269		}
270
271		/* work out block number and offset of this indirect extent */
272		iblock = sb->fs_start + in->extents[dirext].cooked.ex_bn +
273			(cur - ibase) /
274			(EFS_BLOCKSIZE / sizeof(efs_extent));
275		ioffset = (cur - ibase) %
276			(EFS_BLOCKSIZE / sizeof(efs_extent));
277
278		if (first || lastblock != iblock) {
279			if (bh) brelse(bh);
280
281			bh = sb_bread(inode->i_sb, iblock);
282			if (!bh) {
283				pr_err("%s() failed at block %d\n",
284				       __func__, iblock);
285				return 0;
286			}
287			pr_debug("%s(): read indirect extent block %d\n",
288				 __func__, iblock);
289			first = 0;
290			lastblock = iblock;
291		}
292
293		exts = (efs_extent *) bh->b_data;
294
295		extent_copy(&(exts[ioffset]), &ext);
296
297		if (ext.cooked.ex_magic != 0) {
298			pr_err("extent %d has bad magic number in block %d\n",
299			       cur, iblock);
300			if (bh) brelse(bh);
301			return 0;
302		}
303
304		if ((result = efs_extent_check(&ext, block, sb))) {
305			if (bh) brelse(bh);
306			in->lastextent = cur;
307			return result;
308		}
309	}
310	if (bh) brelse(bh);
311	pr_err("%s() failed to map block %u (indir)\n", __func__, block);
312	return 0;
313}
314
315MODULE_LICENSE("GPL");
316