xref: /openbmc/linux/fs/adfs/inode.c (revision 31eeb6b0)
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/writeback.h>
9 #include "adfs.h"
10 
11 /*
12  * Lookup/Create a block at offset 'block' into 'inode'.  We currently do
13  * not support creation of new blocks, so we return -EIO for this case.
14  */
15 static int
16 adfs_get_block(struct inode *inode, sector_t block, struct buffer_head *bh,
17 	       int create)
18 {
19 	if (!create) {
20 		if (block >= inode->i_blocks)
21 			goto abort_toobig;
22 
23 		block = __adfs_block_map(inode->i_sb, ADFS_I(inode)->indaddr,
24 					 block);
25 		if (block)
26 			map_bh(bh, inode->i_sb, block);
27 		return 0;
28 	}
29 	/* don't support allocation of blocks yet */
30 	return -EIO;
31 
32 abort_toobig:
33 	return 0;
34 }
35 
36 static int adfs_writepage(struct page *page, struct writeback_control *wbc)
37 {
38 	return block_write_full_page(page, adfs_get_block, wbc);
39 }
40 
41 static int adfs_readpage(struct file *file, struct page *page)
42 {
43 	return block_read_full_page(page, adfs_get_block);
44 }
45 
46 static void adfs_write_failed(struct address_space *mapping, loff_t to)
47 {
48 	struct inode *inode = mapping->host;
49 
50 	if (to > inode->i_size)
51 		truncate_pagecache(inode, inode->i_size);
52 }
53 
54 static int adfs_write_begin(struct file *file, struct address_space *mapping,
55 			loff_t pos, unsigned len, unsigned flags,
56 			struct page **pagep, void **fsdata)
57 {
58 	int ret;
59 
60 	*pagep = NULL;
61 	ret = cont_write_begin(file, mapping, pos, len, flags, pagep, fsdata,
62 				adfs_get_block,
63 				&ADFS_I(mapping->host)->mmu_private);
64 	if (unlikely(ret))
65 		adfs_write_failed(mapping, pos + len);
66 
67 	return ret;
68 }
69 
70 static sector_t _adfs_bmap(struct address_space *mapping, sector_t block)
71 {
72 	return generic_block_bmap(mapping, block, adfs_get_block);
73 }
74 
75 static const struct address_space_operations adfs_aops = {
76 	.set_page_dirty	= __set_page_dirty_buffers,
77 	.readpage	= adfs_readpage,
78 	.writepage	= adfs_writepage,
79 	.write_begin	= adfs_write_begin,
80 	.write_end	= generic_write_end,
81 	.bmap		= _adfs_bmap
82 };
83 
84 /*
85  * Convert ADFS attributes and filetype to Linux permission.
86  */
87 static umode_t
88 adfs_atts2mode(struct super_block *sb, struct inode *inode)
89 {
90 	unsigned int attr = ADFS_I(inode)->attr;
91 	umode_t mode, rmask;
92 	struct adfs_sb_info *asb = ADFS_SB(sb);
93 
94 	if (attr & ADFS_NDA_DIRECTORY) {
95 		mode = S_IRUGO & asb->s_owner_mask;
96 		return S_IFDIR | S_IXUGO | mode;
97 	}
98 
99 	switch (adfs_filetype(ADFS_I(inode)->loadaddr)) {
100 	case 0xfc0:	/* LinkFS */
101 		return S_IFLNK|S_IRWXUGO;
102 
103 	case 0xfe6:	/* UnixExec */
104 		rmask = S_IRUGO | S_IXUGO;
105 		break;
106 
107 	default:
108 		rmask = S_IRUGO;
109 	}
110 
111 	mode = S_IFREG;
112 
113 	if (attr & ADFS_NDA_OWNER_READ)
114 		mode |= rmask & asb->s_owner_mask;
115 
116 	if (attr & ADFS_NDA_OWNER_WRITE)
117 		mode |= S_IWUGO & asb->s_owner_mask;
118 
119 	if (attr & ADFS_NDA_PUBLIC_READ)
120 		mode |= rmask & asb->s_other_mask;
121 
122 	if (attr & ADFS_NDA_PUBLIC_WRITE)
123 		mode |= S_IWUGO & asb->s_other_mask;
124 	return mode;
125 }
126 
127 /*
128  * Convert Linux permission to ADFS attribute.  We try to do the reverse
129  * of atts2mode, but there is not a 1:1 translation.
130  */
131 static int adfs_mode2atts(struct super_block *sb, struct inode *inode,
132 			  umode_t ia_mode)
133 {
134 	struct adfs_sb_info *asb = ADFS_SB(sb);
135 	umode_t mode;
136 	int attr;
137 
138 	/* FIXME: should we be able to alter a link? */
139 	if (S_ISLNK(inode->i_mode))
140 		return ADFS_I(inode)->attr;
141 
142 	/* Directories do not have read/write permissions on the media */
143 	if (S_ISDIR(inode->i_mode))
144 		return ADFS_NDA_DIRECTORY;
145 
146 	attr = 0;
147 	mode = ia_mode & asb->s_owner_mask;
148 	if (mode & S_IRUGO)
149 		attr |= ADFS_NDA_OWNER_READ;
150 	if (mode & S_IWUGO)
151 		attr |= ADFS_NDA_OWNER_WRITE;
152 
153 	mode = ia_mode & asb->s_other_mask;
154 	mode &= ~asb->s_owner_mask;
155 	if (mode & S_IRUGO)
156 		attr |= ADFS_NDA_PUBLIC_READ;
157 	if (mode & S_IWUGO)
158 		attr |= ADFS_NDA_PUBLIC_WRITE;
159 
160 	return attr;
161 }
162 
163 static const s64 nsec_unix_epoch_diff_risc_os_epoch = 2208988800000000000LL;
164 
165 /*
166  * Convert an ADFS time to Unix time.  ADFS has a 40-bit centi-second time
167  * referenced to 1 Jan 1900 (til 2248) so we need to discard 2208988800 seconds
168  * of time to convert from RISC OS epoch to Unix epoch.
169  */
170 static void
171 adfs_adfs2unix_time(struct timespec64 *tv, struct inode *inode)
172 {
173 	unsigned int high, low;
174 	/* 01 Jan 1970 00:00:00 (Unix epoch) as nanoseconds since
175 	 * 01 Jan 1900 00:00:00 (RISC OS epoch)
176 	 */
177 	s64 nsec;
178 
179 	if (!adfs_inode_is_stamped(inode))
180 		goto cur_time;
181 
182 	high = ADFS_I(inode)->loadaddr & 0xFF; /* top 8 bits of timestamp */
183 	low  = ADFS_I(inode)->execaddr;    /* bottom 32 bits of timestamp */
184 
185 	/* convert 40-bit centi-seconds to 32-bit seconds
186 	 * going via nanoseconds to retain precision
187 	 */
188 	nsec = (((s64) high << 32) | (s64) low) * 10000000; /* cs to ns */
189 
190 	/* Files dated pre  01 Jan 1970 00:00:00. */
191 	if (nsec < nsec_unix_epoch_diff_risc_os_epoch)
192 		goto too_early;
193 
194 	/* convert from RISC OS to Unix epoch */
195 	nsec -= nsec_unix_epoch_diff_risc_os_epoch;
196 
197 	*tv = ns_to_timespec64(nsec);
198 	return;
199 
200  cur_time:
201 	*tv = current_time(inode);
202 	return;
203 
204  too_early:
205 	tv->tv_sec = tv->tv_nsec = 0;
206 	return;
207 }
208 
209 /* Convert an Unix time to ADFS time for an entry that is already stamped. */
210 static void adfs_unix2adfs_time(struct inode *inode,
211 				const struct timespec64 *ts)
212 {
213 	s64 cs, nsec = timespec64_to_ns(ts);
214 
215 	/* convert from Unix to RISC OS epoch */
216 	nsec += nsec_unix_epoch_diff_risc_os_epoch;
217 
218 	/* convert from nanoseconds to centiseconds */
219 	cs = div_s64(nsec, 10000000);
220 
221 	cs = clamp_t(s64, cs, 0, 0xffffffffff);
222 
223 	ADFS_I(inode)->loadaddr &= ~0xff;
224 	ADFS_I(inode)->loadaddr |= (cs >> 32) & 0xff;
225 	ADFS_I(inode)->execaddr = cs;
226 }
227 
228 /*
229  * Fill in the inode information from the object information.
230  *
231  * Note that this is an inode-less filesystem, so we can't use the inode
232  * number to reference the metadata on the media.  Instead, we use the
233  * inode number to hold the object ID, which in turn will tell us where
234  * the data is held.  We also save the parent object ID, and with these
235  * two, we can locate the metadata.
236  *
237  * This does mean that we rely on an objects parent remaining the same at
238  * all times - we cannot cope with a cross-directory rename (yet).
239  */
240 struct inode *
241 adfs_iget(struct super_block *sb, struct object_info *obj)
242 {
243 	struct inode *inode;
244 
245 	inode = new_inode(sb);
246 	if (!inode)
247 		goto out;
248 
249 	inode->i_uid	 = ADFS_SB(sb)->s_uid;
250 	inode->i_gid	 = ADFS_SB(sb)->s_gid;
251 	inode->i_ino	 = obj->indaddr;
252 	inode->i_size	 = obj->size;
253 	set_nlink(inode, 2);
254 	inode->i_blocks	 = (inode->i_size + sb->s_blocksize - 1) >>
255 			    sb->s_blocksize_bits;
256 
257 	/*
258 	 * we need to save the parent directory ID so that
259 	 * write_inode can update the directory information
260 	 * for this file.  This will need special handling
261 	 * for cross-directory renames.
262 	 */
263 	ADFS_I(inode)->parent_id = obj->parent_id;
264 	ADFS_I(inode)->indaddr   = obj->indaddr;
265 	ADFS_I(inode)->loadaddr  = obj->loadaddr;
266 	ADFS_I(inode)->execaddr  = obj->execaddr;
267 	ADFS_I(inode)->attr      = obj->attr;
268 
269 	inode->i_mode	 = adfs_atts2mode(sb, inode);
270 	adfs_adfs2unix_time(&inode->i_mtime, inode);
271 	inode->i_atime = inode->i_mtime;
272 	inode->i_ctime = inode->i_mtime;
273 
274 	if (S_ISDIR(inode->i_mode)) {
275 		inode->i_op	= &adfs_dir_inode_operations;
276 		inode->i_fop	= &adfs_dir_operations;
277 	} else if (S_ISREG(inode->i_mode)) {
278 		inode->i_op	= &adfs_file_inode_operations;
279 		inode->i_fop	= &adfs_file_operations;
280 		inode->i_mapping->a_ops = &adfs_aops;
281 		ADFS_I(inode)->mmu_private = inode->i_size;
282 	}
283 
284 	inode_fake_hash(inode);
285 
286 out:
287 	return inode;
288 }
289 
290 /*
291  * Validate and convert a changed access mode/time to their ADFS equivalents.
292  * adfs_write_inode will actually write the information back to the directory
293  * later.
294  */
295 int
296 adfs_notify_change(struct user_namespace *mnt_userns, struct dentry *dentry,
297 		   struct iattr *attr)
298 {
299 	struct inode *inode = d_inode(dentry);
300 	struct super_block *sb = inode->i_sb;
301 	unsigned int ia_valid = attr->ia_valid;
302 	int error;
303 
304 	error = setattr_prepare(&init_user_ns, dentry, attr);
305 
306 	/*
307 	 * we can't change the UID or GID of any file -
308 	 * we have a global UID/GID in the superblock
309 	 */
310 	if ((ia_valid & ATTR_UID && !uid_eq(attr->ia_uid, ADFS_SB(sb)->s_uid)) ||
311 	    (ia_valid & ATTR_GID && !gid_eq(attr->ia_gid, ADFS_SB(sb)->s_gid)))
312 		error = -EPERM;
313 
314 	if (error)
315 		goto out;
316 
317 	/* XXX: this is missing some actual on-disk truncation.. */
318 	if (ia_valid & ATTR_SIZE)
319 		truncate_setsize(inode, attr->ia_size);
320 
321 	if (ia_valid & ATTR_MTIME && adfs_inode_is_stamped(inode)) {
322 		adfs_unix2adfs_time(inode, &attr->ia_mtime);
323 		adfs_adfs2unix_time(&inode->i_mtime, inode);
324 	}
325 
326 	/*
327 	 * FIXME: should we make these == to i_mtime since we don't
328 	 * have the ability to represent them in our filesystem?
329 	 */
330 	if (ia_valid & ATTR_ATIME)
331 		inode->i_atime = attr->ia_atime;
332 	if (ia_valid & ATTR_CTIME)
333 		inode->i_ctime = attr->ia_ctime;
334 	if (ia_valid & ATTR_MODE) {
335 		ADFS_I(inode)->attr = adfs_mode2atts(sb, inode, attr->ia_mode);
336 		inode->i_mode = adfs_atts2mode(sb, inode);
337 	}
338 
339 	/*
340 	 * FIXME: should we be marking this inode dirty even if
341 	 * we don't have any metadata to write back?
342 	 */
343 	if (ia_valid & (ATTR_SIZE | ATTR_MTIME | ATTR_MODE))
344 		mark_inode_dirty(inode);
345 out:
346 	return error;
347 }
348 
349 /*
350  * write an existing inode back to the directory, and therefore the disk.
351  * The adfs-specific inode data has already been updated by
352  * adfs_notify_change()
353  */
354 int adfs_write_inode(struct inode *inode, struct writeback_control *wbc)
355 {
356 	struct super_block *sb = inode->i_sb;
357 	struct object_info obj;
358 
359 	obj.indaddr	= ADFS_I(inode)->indaddr;
360 	obj.name_len	= 0;
361 	obj.parent_id	= ADFS_I(inode)->parent_id;
362 	obj.loadaddr	= ADFS_I(inode)->loadaddr;
363 	obj.execaddr	= ADFS_I(inode)->execaddr;
364 	obj.attr	= ADFS_I(inode)->attr;
365 	obj.size	= inode->i_size;
366 
367 	return adfs_dir_update(sb, &obj, wbc->sync_mode == WB_SYNC_ALL);
368 }
369