1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * linux/fs/sysv/dir.c
4 *
5 * minix/dir.c
6 * Copyright (C) 1991, 1992 Linus Torvalds
7 *
8 * coh/dir.c
9 * Copyright (C) 1993 Pascal Haible, Bruno Haible
10 *
11 * sysv/dir.c
12 * Copyright (C) 1993 Bruno Haible
13 *
14 * SystemV/Coherent directory handling functions
15 */
16
17 #include <linux/pagemap.h>
18 #include <linux/highmem.h>
19 #include <linux/swap.h>
20 #include "sysv.h"
21
22 static int sysv_readdir(struct file *, struct dir_context *);
23
24 const struct file_operations sysv_dir_operations = {
25 .llseek = generic_file_llseek,
26 .read = generic_read_dir,
27 .iterate_shared = sysv_readdir,
28 .fsync = generic_file_fsync,
29 };
30
dir_commit_chunk(struct folio * folio,loff_t pos,unsigned len)31 static void dir_commit_chunk(struct folio *folio, loff_t pos, unsigned len)
32 {
33 struct address_space *mapping = folio->mapping;
34 struct inode *dir = mapping->host;
35
36 block_write_end(NULL, mapping, pos, len, len, folio, NULL);
37 if (pos+len > dir->i_size) {
38 i_size_write(dir, pos+len);
39 mark_inode_dirty(dir);
40 }
41 folio_unlock(folio);
42 }
43
sysv_handle_dirsync(struct inode * dir)44 static int sysv_handle_dirsync(struct inode *dir)
45 {
46 int err;
47
48 err = filemap_write_and_wait(dir->i_mapping);
49 if (!err)
50 err = sync_inode_metadata(dir, 1);
51 return err;
52 }
53
54 /*
55 * Calls to dir_get_folio()/folio_release_kmap() must be nested according to the
56 * rules documented in mm/highmem.rst.
57 *
58 * NOTE: sysv_find_entry() and sysv_dotdot() act as calls to dir_get_folio()
59 * and must be treated accordingly for nesting purposes.
60 */
dir_get_folio(struct inode * dir,unsigned long n,struct folio ** foliop)61 static void *dir_get_folio(struct inode *dir, unsigned long n,
62 struct folio **foliop)
63 {
64 struct folio *folio = read_mapping_folio(dir->i_mapping, n, NULL);
65
66 if (IS_ERR(folio))
67 return ERR_CAST(folio);
68 *foliop = folio;
69 return kmap_local_folio(folio, 0);
70 }
71
sysv_readdir(struct file * file,struct dir_context * ctx)72 static int sysv_readdir(struct file *file, struct dir_context *ctx)
73 {
74 unsigned long pos = ctx->pos;
75 struct inode *inode = file_inode(file);
76 struct super_block *sb = inode->i_sb;
77 unsigned long npages = dir_pages(inode);
78 unsigned offset;
79 unsigned long n;
80
81 ctx->pos = pos = (pos + SYSV_DIRSIZE-1) & ~(SYSV_DIRSIZE-1);
82 if (pos >= inode->i_size)
83 return 0;
84
85 offset = pos & ~PAGE_MASK;
86 n = pos >> PAGE_SHIFT;
87
88 for ( ; n < npages; n++, offset = 0) {
89 char *kaddr, *limit;
90 struct sysv_dir_entry *de;
91 struct folio *folio;
92
93 kaddr = dir_get_folio(inode, n, &folio);
94 if (IS_ERR(kaddr))
95 continue;
96 de = (struct sysv_dir_entry *)(kaddr+offset);
97 limit = kaddr + PAGE_SIZE - SYSV_DIRSIZE;
98 for ( ;(char*)de <= limit; de++, ctx->pos += sizeof(*de)) {
99 char *name = de->name;
100
101 if (!de->inode)
102 continue;
103
104 if (!dir_emit(ctx, name, strnlen(name,SYSV_NAMELEN),
105 fs16_to_cpu(SYSV_SB(sb), de->inode),
106 DT_UNKNOWN)) {
107 folio_release_kmap(folio, kaddr);
108 return 0;
109 }
110 }
111 folio_release_kmap(folio, kaddr);
112 }
113 return 0;
114 }
115
116 /* compare strings: name[0..len-1] (not zero-terminated) and
117 * buffer[0..] (filled with zeroes up to buffer[0..maxlen-1])
118 */
namecompare(int len,int maxlen,const char * name,const char * buffer)119 static inline int namecompare(int len, int maxlen,
120 const char * name, const char * buffer)
121 {
122 if (len < maxlen && buffer[len])
123 return 0;
124 return !memcmp(name, buffer, len);
125 }
126
127 /*
128 * sysv_find_entry()
129 *
130 * finds an entry in the specified directory with the wanted name.
131 * It does NOT read the inode of the
132 * entry - you'll have to do that yourself if you want to.
133 *
134 * On Success folio_release_kmap() should be called on *foliop.
135 *
136 * sysv_find_entry() acts as a call to dir_get_folio() and must be treated
137 * accordingly for nesting purposes.
138 */
sysv_find_entry(struct dentry * dentry,struct folio ** foliop)139 struct sysv_dir_entry *sysv_find_entry(struct dentry *dentry, struct folio **foliop)
140 {
141 const char * name = dentry->d_name.name;
142 int namelen = dentry->d_name.len;
143 struct inode * dir = d_inode(dentry->d_parent);
144 unsigned long start, n;
145 unsigned long npages = dir_pages(dir);
146 struct sysv_dir_entry *de;
147
148 start = SYSV_I(dir)->i_dir_start_lookup;
149 if (start >= npages)
150 start = 0;
151 n = start;
152
153 do {
154 char *kaddr = dir_get_folio(dir, n, foliop);
155
156 if (!IS_ERR(kaddr)) {
157 de = (struct sysv_dir_entry *)kaddr;
158 kaddr += folio_size(*foliop) - SYSV_DIRSIZE;
159 for ( ; (char *) de <= kaddr ; de++) {
160 if (!de->inode)
161 continue;
162 if (namecompare(namelen, SYSV_NAMELEN,
163 name, de->name))
164 goto found;
165 }
166 folio_release_kmap(*foliop, kaddr);
167 }
168
169 if (++n >= npages)
170 n = 0;
171 } while (n != start);
172
173 return NULL;
174
175 found:
176 SYSV_I(dir)->i_dir_start_lookup = n;
177 return de;
178 }
179
sysv_add_link(struct dentry * dentry,struct inode * inode)180 int sysv_add_link(struct dentry *dentry, struct inode *inode)
181 {
182 struct inode *dir = d_inode(dentry->d_parent);
183 const char * name = dentry->d_name.name;
184 int namelen = dentry->d_name.len;
185 struct folio *folio = NULL;
186 struct sysv_dir_entry * de;
187 unsigned long npages = dir_pages(dir);
188 unsigned long n;
189 char *kaddr;
190 loff_t pos;
191 int err;
192
193 /* We take care of directory expansion in the same loop */
194 for (n = 0; n <= npages; n++) {
195 kaddr = dir_get_folio(dir, n, &folio);
196 if (IS_ERR(kaddr))
197 return PTR_ERR(kaddr);
198 de = (struct sysv_dir_entry *)kaddr;
199 kaddr += PAGE_SIZE - SYSV_DIRSIZE;
200 while ((char *)de <= kaddr) {
201 if (!de->inode)
202 goto got_it;
203 err = -EEXIST;
204 if (namecompare(namelen, SYSV_NAMELEN, name, de->name))
205 goto out_folio;
206 de++;
207 }
208 folio_release_kmap(folio, kaddr);
209 }
210 BUG();
211 return -EINVAL;
212
213 got_it:
214 pos = folio_pos(folio) + offset_in_folio(folio, de);
215 folio_lock(folio);
216 err = sysv_prepare_chunk(folio, pos, SYSV_DIRSIZE);
217 if (err)
218 goto out_unlock;
219 memcpy (de->name, name, namelen);
220 memset (de->name + namelen, 0, SYSV_DIRSIZE - namelen - 2);
221 de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino);
222 dir_commit_chunk(folio, pos, SYSV_DIRSIZE);
223 inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir));
224 mark_inode_dirty(dir);
225 err = sysv_handle_dirsync(dir);
226 out_folio:
227 folio_release_kmap(folio, kaddr);
228 return err;
229 out_unlock:
230 folio_unlock(folio);
231 goto out_folio;
232 }
233
sysv_delete_entry(struct sysv_dir_entry * de,struct folio * folio)234 int sysv_delete_entry(struct sysv_dir_entry *de, struct folio *folio)
235 {
236 struct inode *inode = folio->mapping->host;
237 loff_t pos = folio_pos(folio) + offset_in_folio(folio, de);
238 int err;
239
240 folio_lock(folio);
241 err = sysv_prepare_chunk(folio, pos, SYSV_DIRSIZE);
242 if (err) {
243 folio_unlock(folio);
244 return err;
245 }
246 de->inode = 0;
247 dir_commit_chunk(folio, pos, SYSV_DIRSIZE);
248 inode_set_mtime_to_ts(inode, inode_set_ctime_current(inode));
249 mark_inode_dirty(inode);
250 return sysv_handle_dirsync(inode);
251 }
252
sysv_make_empty(struct inode * inode,struct inode * dir)253 int sysv_make_empty(struct inode *inode, struct inode *dir)
254 {
255 struct folio *folio = filemap_grab_folio(inode->i_mapping, 0);
256 struct sysv_dir_entry * de;
257 char *kaddr;
258 int err;
259
260 if (IS_ERR(folio))
261 return PTR_ERR(folio);
262 err = sysv_prepare_chunk(folio, 0, 2 * SYSV_DIRSIZE);
263 if (err) {
264 folio_unlock(folio);
265 goto fail;
266 }
267 kaddr = kmap_local_folio(folio, 0);
268 memset(kaddr, 0, folio_size(folio));
269
270 de = (struct sysv_dir_entry *)kaddr;
271 de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino);
272 strcpy(de->name,".");
273 de++;
274 de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), dir->i_ino);
275 strcpy(de->name,"..");
276
277 kunmap_local(kaddr);
278 dir_commit_chunk(folio, 0, 2 * SYSV_DIRSIZE);
279 err = sysv_handle_dirsync(inode);
280 fail:
281 folio_put(folio);
282 return err;
283 }
284
285 /*
286 * routine to check that the specified directory is empty (for rmdir)
287 */
sysv_empty_dir(struct inode * inode)288 int sysv_empty_dir(struct inode * inode)
289 {
290 struct super_block *sb = inode->i_sb;
291 struct folio *folio = NULL;
292 unsigned long i, npages = dir_pages(inode);
293 char *kaddr;
294
295 for (i = 0; i < npages; i++) {
296 struct sysv_dir_entry *de;
297
298 kaddr = dir_get_folio(inode, i, &folio);
299 if (IS_ERR(kaddr))
300 continue;
301
302 de = (struct sysv_dir_entry *)kaddr;
303 kaddr += folio_size(folio) - SYSV_DIRSIZE;
304
305 for ( ;(char *)de <= kaddr; de++) {
306 if (!de->inode)
307 continue;
308 /* check for . and .. */
309 if (de->name[0] != '.')
310 goto not_empty;
311 if (!de->name[1]) {
312 if (de->inode == cpu_to_fs16(SYSV_SB(sb),
313 inode->i_ino))
314 continue;
315 goto not_empty;
316 }
317 if (de->name[1] != '.' || de->name[2])
318 goto not_empty;
319 }
320 folio_release_kmap(folio, kaddr);
321 }
322 return 1;
323
324 not_empty:
325 folio_release_kmap(folio, kaddr);
326 return 0;
327 }
328
329 /* Releases the page */
sysv_set_link(struct sysv_dir_entry * de,struct folio * folio,struct inode * inode)330 int sysv_set_link(struct sysv_dir_entry *de, struct folio *folio,
331 struct inode *inode)
332 {
333 struct inode *dir = folio->mapping->host;
334 loff_t pos = folio_pos(folio) + offset_in_folio(folio, de);
335 int err;
336
337 folio_lock(folio);
338 err = sysv_prepare_chunk(folio, pos, SYSV_DIRSIZE);
339 if (err) {
340 folio_unlock(folio);
341 return err;
342 }
343 de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino);
344 dir_commit_chunk(folio, pos, SYSV_DIRSIZE);
345 inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir));
346 mark_inode_dirty(dir);
347 return sysv_handle_dirsync(inode);
348 }
349
350 /*
351 * Calls to dir_get_folio()/folio_release_kmap() must be nested according to the
352 * rules documented in mm/highmem.rst.
353 *
354 * sysv_dotdot() acts as a call to dir_get_folio() and must be treated
355 * accordingly for nesting purposes.
356 */
sysv_dotdot(struct inode * dir,struct folio ** foliop)357 struct sysv_dir_entry *sysv_dotdot(struct inode *dir, struct folio **foliop)
358 {
359 struct sysv_dir_entry *de = dir_get_folio(dir, 0, foliop);
360
361 if (IS_ERR(de))
362 return NULL;
363 /* ".." is the second directory entry */
364 return de + 1;
365 }
366
sysv_inode_by_name(struct dentry * dentry)367 ino_t sysv_inode_by_name(struct dentry *dentry)
368 {
369 struct folio *folio;
370 struct sysv_dir_entry *de = sysv_find_entry (dentry, &folio);
371 ino_t res = 0;
372
373 if (de) {
374 res = fs16_to_cpu(SYSV_SB(dentry->d_sb), de->inode);
375 folio_release_kmap(folio, de);
376 }
377 return res;
378 }
379