1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 *  linux/fs/adfs/inode.c
4 *
5 *  Copyright (C) 1997-1999 Russell King
6 */
7#include <linux/buffer_head.h>
8#include <linux/mpage.h>
9#include <linux/writeback.h>
10#include "adfs.h"
11
12/*
13 * Lookup/Create a block at offset 'block' into 'inode'.  We currently do
14 * not support creation of new blocks, so we return -EIO for this case.
15 */
16static int
17adfs_get_block(struct inode *inode, sector_t block, struct buffer_head *bh,
18	       int create)
19{
20	if (!create) {
21		if (block >= inode->i_blocks)
22			goto abort_toobig;
23
24		block = __adfs_block_map(inode->i_sb, ADFS_I(inode)->indaddr,
25					 block);
26		if (block)
27			map_bh(bh, inode->i_sb, block);
28		return 0;
29	}
30	/* don't support allocation of blocks yet */
31	return -EIO;
32
33abort_toobig:
34	return 0;
35}
36
37static int adfs_writepages(struct address_space *mapping,
38		struct writeback_control *wbc)
39{
40	return mpage_writepages(mapping, wbc, adfs_get_block);
41}
42
43static int adfs_read_folio(struct file *file, struct folio *folio)
44{
45	return block_read_full_folio(folio, adfs_get_block);
46}
47
48static void adfs_write_failed(struct address_space *mapping, loff_t to)
49{
50	struct inode *inode = mapping->host;
51
52	if (to > inode->i_size)
53		truncate_pagecache(inode, inode->i_size);
54}
55
56static int adfs_write_begin(struct file *file, struct address_space *mapping,
57			loff_t pos, unsigned len,
58			struct page **pagep, void **fsdata)
59{
60	int ret;
61
62	*pagep = NULL;
63	ret = cont_write_begin(file, mapping, pos, len, pagep, fsdata,
64				adfs_get_block,
65				&ADFS_I(mapping->host)->mmu_private);
66	if (unlikely(ret))
67		adfs_write_failed(mapping, pos + len);
68
69	return ret;
70}
71
72static sector_t _adfs_bmap(struct address_space *mapping, sector_t block)
73{
74	return generic_block_bmap(mapping, block, adfs_get_block);
75}
76
77static const struct address_space_operations adfs_aops = {
78	.dirty_folio	= block_dirty_folio,
79	.invalidate_folio = block_invalidate_folio,
80	.read_folio	= adfs_read_folio,
81	.writepages	= adfs_writepages,
82	.write_begin	= adfs_write_begin,
83	.write_end	= generic_write_end,
84	.migrate_folio	= buffer_migrate_folio,
85	.bmap		= _adfs_bmap,
86};
87
88/*
89 * Convert ADFS attributes and filetype to Linux permission.
90 */
91static umode_t
92adfs_atts2mode(struct super_block *sb, struct inode *inode)
93{
94	unsigned int attr = ADFS_I(inode)->attr;
95	umode_t mode, rmask;
96	struct adfs_sb_info *asb = ADFS_SB(sb);
97
98	if (attr & ADFS_NDA_DIRECTORY) {
99		mode = S_IRUGO & asb->s_owner_mask;
100		return S_IFDIR | S_IXUGO | mode;
101	}
102
103	switch (adfs_filetype(ADFS_I(inode)->loadaddr)) {
104	case 0xfc0:	/* LinkFS */
105		return S_IFLNK|S_IRWXUGO;
106
107	case 0xfe6:	/* UnixExec */
108		rmask = S_IRUGO | S_IXUGO;
109		break;
110
111	default:
112		rmask = S_IRUGO;
113	}
114
115	mode = S_IFREG;
116
117	if (attr & ADFS_NDA_OWNER_READ)
118		mode |= rmask & asb->s_owner_mask;
119
120	if (attr & ADFS_NDA_OWNER_WRITE)
121		mode |= S_IWUGO & asb->s_owner_mask;
122
123	if (attr & ADFS_NDA_PUBLIC_READ)
124		mode |= rmask & asb->s_other_mask;
125
126	if (attr & ADFS_NDA_PUBLIC_WRITE)
127		mode |= S_IWUGO & asb->s_other_mask;
128	return mode;
129}
130
131/*
132 * Convert Linux permission to ADFS attribute.  We try to do the reverse
133 * of atts2mode, but there is not a 1:1 translation.
134 */
135static int adfs_mode2atts(struct super_block *sb, struct inode *inode,
136			  umode_t ia_mode)
137{
138	struct adfs_sb_info *asb = ADFS_SB(sb);
139	umode_t mode;
140	int attr;
141
142	/* FIXME: should we be able to alter a link? */
143	if (S_ISLNK(inode->i_mode))
144		return ADFS_I(inode)->attr;
145
146	/* Directories do not have read/write permissions on the media */
147	if (S_ISDIR(inode->i_mode))
148		return ADFS_NDA_DIRECTORY;
149
150	attr = 0;
151	mode = ia_mode & asb->s_owner_mask;
152	if (mode & S_IRUGO)
153		attr |= ADFS_NDA_OWNER_READ;
154	if (mode & S_IWUGO)
155		attr |= ADFS_NDA_OWNER_WRITE;
156
157	mode = ia_mode & asb->s_other_mask;
158	mode &= ~asb->s_owner_mask;
159	if (mode & S_IRUGO)
160		attr |= ADFS_NDA_PUBLIC_READ;
161	if (mode & S_IWUGO)
162		attr |= ADFS_NDA_PUBLIC_WRITE;
163
164	return attr;
165}
166
167static const s64 nsec_unix_epoch_diff_risc_os_epoch = 2208988800000000000LL;
168
169/*
170 * Convert an ADFS time to Unix time.  ADFS has a 40-bit centi-second time
171 * referenced to 1 Jan 1900 (til 2248) so we need to discard 2208988800 seconds
172 * of time to convert from RISC OS epoch to Unix epoch.
173 */
174static void
175adfs_adfs2unix_time(struct timespec64 *tv, struct inode *inode)
176{
177	unsigned int high, low;
178	/* 01 Jan 1970 00:00:00 (Unix epoch) as nanoseconds since
179	 * 01 Jan 1900 00:00:00 (RISC OS epoch)
180	 */
181	s64 nsec;
182
183	if (!adfs_inode_is_stamped(inode))
184		goto cur_time;
185
186	high = ADFS_I(inode)->loadaddr & 0xFF; /* top 8 bits of timestamp */
187	low  = ADFS_I(inode)->execaddr;    /* bottom 32 bits of timestamp */
188
189	/* convert 40-bit centi-seconds to 32-bit seconds
190	 * going via nanoseconds to retain precision
191	 */
192	nsec = (((s64) high << 32) | (s64) low) * 10000000; /* cs to ns */
193
194	/* Files dated pre  01 Jan 1970 00:00:00. */
195	if (nsec < nsec_unix_epoch_diff_risc_os_epoch)
196		goto too_early;
197
198	/* convert from RISC OS to Unix epoch */
199	nsec -= nsec_unix_epoch_diff_risc_os_epoch;
200
201	*tv = ns_to_timespec64(nsec);
202	return;
203
204 cur_time:
205	*tv = current_time(inode);
206	return;
207
208 too_early:
209	tv->tv_sec = tv->tv_nsec = 0;
210	return;
211}
212
213/* Convert an Unix time to ADFS time for an entry that is already stamped. */
214static void adfs_unix2adfs_time(struct inode *inode,
215				const struct timespec64 *ts)
216{
217	s64 cs, nsec = timespec64_to_ns(ts);
218
219	/* convert from Unix to RISC OS epoch */
220	nsec += nsec_unix_epoch_diff_risc_os_epoch;
221
222	/* convert from nanoseconds to centiseconds */
223	cs = div_s64(nsec, 10000000);
224
225	cs = clamp_t(s64, cs, 0, 0xffffffffff);
226
227	ADFS_I(inode)->loadaddr &= ~0xff;
228	ADFS_I(inode)->loadaddr |= (cs >> 32) & 0xff;
229	ADFS_I(inode)->execaddr = cs;
230}
231
232/*
233 * Fill in the inode information from the object information.
234 *
235 * Note that this is an inode-less filesystem, so we can't use the inode
236 * number to reference the metadata on the media.  Instead, we use the
237 * inode number to hold the object ID, which in turn will tell us where
238 * the data is held.  We also save the parent object ID, and with these
239 * two, we can locate the metadata.
240 *
241 * This does mean that we rely on an objects parent remaining the same at
242 * all times - we cannot cope with a cross-directory rename (yet).
243 */
244struct inode *
245adfs_iget(struct super_block *sb, struct object_info *obj)
246{
247	struct inode *inode;
248	struct timespec64 ts;
249
250	inode = new_inode(sb);
251	if (!inode)
252		goto out;
253
254	inode->i_uid	 = ADFS_SB(sb)->s_uid;
255	inode->i_gid	 = ADFS_SB(sb)->s_gid;
256	inode->i_ino	 = obj->indaddr;
257	inode->i_size	 = obj->size;
258	set_nlink(inode, 2);
259	inode->i_blocks	 = (inode->i_size + sb->s_blocksize - 1) >>
260			    sb->s_blocksize_bits;
261
262	/*
263	 * we need to save the parent directory ID so that
264	 * write_inode can update the directory information
265	 * for this file.  This will need special handling
266	 * for cross-directory renames.
267	 */
268	ADFS_I(inode)->parent_id = obj->parent_id;
269	ADFS_I(inode)->indaddr   = obj->indaddr;
270	ADFS_I(inode)->loadaddr  = obj->loadaddr;
271	ADFS_I(inode)->execaddr  = obj->execaddr;
272	ADFS_I(inode)->attr      = obj->attr;
273
274	inode->i_mode	 = adfs_atts2mode(sb, inode);
275	adfs_adfs2unix_time(&ts, inode);
276	inode_set_atime_to_ts(inode, ts);
277	inode_set_mtime_to_ts(inode, ts);
278	inode_set_ctime_to_ts(inode, ts);
279
280	if (S_ISDIR(inode->i_mode)) {
281		inode->i_op	= &adfs_dir_inode_operations;
282		inode->i_fop	= &adfs_dir_operations;
283	} else if (S_ISREG(inode->i_mode)) {
284		inode->i_op	= &adfs_file_inode_operations;
285		inode->i_fop	= &adfs_file_operations;
286		inode->i_mapping->a_ops = &adfs_aops;
287		ADFS_I(inode)->mmu_private = inode->i_size;
288	}
289
290	inode_fake_hash(inode);
291
292out:
293	return inode;
294}
295
296/*
297 * Validate and convert a changed access mode/time to their ADFS equivalents.
298 * adfs_write_inode will actually write the information back to the directory
299 * later.
300 */
301int
302adfs_notify_change(struct mnt_idmap *idmap, struct dentry *dentry,
303		   struct iattr *attr)
304{
305	struct inode *inode = d_inode(dentry);
306	struct super_block *sb = inode->i_sb;
307	unsigned int ia_valid = attr->ia_valid;
308	int error;
309
310	error = setattr_prepare(&nop_mnt_idmap, dentry, attr);
311
312	/*
313	 * we can't change the UID or GID of any file -
314	 * we have a global UID/GID in the superblock
315	 */
316	if ((ia_valid & ATTR_UID && !uid_eq(attr->ia_uid, ADFS_SB(sb)->s_uid)) ||
317	    (ia_valid & ATTR_GID && !gid_eq(attr->ia_gid, ADFS_SB(sb)->s_gid)))
318		error = -EPERM;
319
320	if (error)
321		goto out;
322
323	/* XXX: this is missing some actual on-disk truncation.. */
324	if (ia_valid & ATTR_SIZE)
325		truncate_setsize(inode, attr->ia_size);
326
327	if (ia_valid & ATTR_MTIME && adfs_inode_is_stamped(inode)) {
328		adfs_unix2adfs_time(inode, &attr->ia_mtime);
329		adfs_adfs2unix_time(&attr->ia_mtime, inode);
330		inode_set_mtime_to_ts(inode, attr->ia_mtime);
331	}
332
333	/*
334	 * FIXME: should we make these == to i_mtime since we don't
335	 * have the ability to represent them in our filesystem?
336	 */
337	if (ia_valid & ATTR_ATIME)
338		inode_set_atime_to_ts(inode, attr->ia_atime);
339	if (ia_valid & ATTR_CTIME)
340		inode_set_ctime_to_ts(inode, attr->ia_ctime);
341	if (ia_valid & ATTR_MODE) {
342		ADFS_I(inode)->attr = adfs_mode2atts(sb, inode, attr->ia_mode);
343		inode->i_mode = adfs_atts2mode(sb, inode);
344	}
345
346	/*
347	 * FIXME: should we be marking this inode dirty even if
348	 * we don't have any metadata to write back?
349	 */
350	if (ia_valid & (ATTR_SIZE | ATTR_MTIME | ATTR_MODE))
351		mark_inode_dirty(inode);
352out:
353	return error;
354}
355
356/*
357 * write an existing inode back to the directory, and therefore the disk.
358 * The adfs-specific inode data has already been updated by
359 * adfs_notify_change()
360 */
361int adfs_write_inode(struct inode *inode, struct writeback_control *wbc)
362{
363	struct super_block *sb = inode->i_sb;
364	struct object_info obj;
365
366	obj.indaddr	= ADFS_I(inode)->indaddr;
367	obj.name_len	= 0;
368	obj.parent_id	= ADFS_I(inode)->parent_id;
369	obj.loadaddr	= ADFS_I(inode)->loadaddr;
370	obj.execaddr	= ADFS_I(inode)->execaddr;
371	obj.attr	= ADFS_I(inode)->attr;
372	obj.size	= inode->i_size;
373
374	return adfs_dir_update(sb, &obj, wbc->sync_mode == WB_SYNC_ALL);
375}
376