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_put_page(struct page * page,void * page_addr)31 inline void dir_put_page(struct page *page, void *page_addr)
32 {
33 kunmap_local((void *)((unsigned long)page_addr & PAGE_MASK));
34 put_page(page);
35 }
36
dir_commit_chunk(struct page * page,loff_t pos,unsigned len)37 static void dir_commit_chunk(struct page *page, loff_t pos, unsigned len)
38 {
39 struct address_space *mapping = page->mapping;
40 struct inode *dir = mapping->host;
41
42 block_write_end(NULL, mapping, pos, len, len, page, NULL);
43 if (pos+len > dir->i_size) {
44 i_size_write(dir, pos+len);
45 mark_inode_dirty(dir);
46 }
47 unlock_page(page);
48 }
49
sysv_handle_dirsync(struct inode * dir)50 static int sysv_handle_dirsync(struct inode *dir)
51 {
52 int err;
53
54 err = filemap_write_and_wait(dir->i_mapping);
55 if (!err)
56 err = sync_inode_metadata(dir, 1);
57 return err;
58 }
59
60 /*
61 * Calls to dir_get_page()/dir_put_page() must be nested according to the
62 * rules documented in mm/highmem.rst.
63 *
64 * NOTE: sysv_find_entry() and sysv_dotdot() act as calls to dir_get_page()
65 * and must be treated accordingly for nesting purposes.
66 */
dir_get_page(struct inode * dir,unsigned long n,struct page ** p)67 static void *dir_get_page(struct inode *dir, unsigned long n, struct page **p)
68 {
69 struct address_space *mapping = dir->i_mapping;
70 struct page *page = read_mapping_page(mapping, n, NULL);
71 if (IS_ERR(page))
72 return ERR_CAST(page);
73 *p = page;
74 return kmap_local_page(page);
75 }
76
sysv_readdir(struct file * file,struct dir_context * ctx)77 static int sysv_readdir(struct file *file, struct dir_context *ctx)
78 {
79 unsigned long pos = ctx->pos;
80 struct inode *inode = file_inode(file);
81 struct super_block *sb = inode->i_sb;
82 unsigned long npages = dir_pages(inode);
83 unsigned offset;
84 unsigned long n;
85
86 ctx->pos = pos = (pos + SYSV_DIRSIZE-1) & ~(SYSV_DIRSIZE-1);
87 if (pos >= inode->i_size)
88 return 0;
89
90 offset = pos & ~PAGE_MASK;
91 n = pos >> PAGE_SHIFT;
92
93 for ( ; n < npages; n++, offset = 0) {
94 char *kaddr, *limit;
95 struct sysv_dir_entry *de;
96 struct page *page;
97
98 kaddr = dir_get_page(inode, n, &page);
99 if (IS_ERR(kaddr))
100 continue;
101 de = (struct sysv_dir_entry *)(kaddr+offset);
102 limit = kaddr + PAGE_SIZE - SYSV_DIRSIZE;
103 for ( ;(char*)de <= limit; de++, ctx->pos += sizeof(*de)) {
104 char *name = de->name;
105
106 if (!de->inode)
107 continue;
108
109 if (!dir_emit(ctx, name, strnlen(name,SYSV_NAMELEN),
110 fs16_to_cpu(SYSV_SB(sb), de->inode),
111 DT_UNKNOWN)) {
112 dir_put_page(page, kaddr);
113 return 0;
114 }
115 }
116 dir_put_page(page, kaddr);
117 }
118 return 0;
119 }
120
121 /* compare strings: name[0..len-1] (not zero-terminated) and
122 * buffer[0..] (filled with zeroes up to buffer[0..maxlen-1])
123 */
namecompare(int len,int maxlen,const char * name,const char * buffer)124 static inline int namecompare(int len, int maxlen,
125 const char * name, const char * buffer)
126 {
127 if (len < maxlen && buffer[len])
128 return 0;
129 return !memcmp(name, buffer, len);
130 }
131
132 /*
133 * sysv_find_entry()
134 *
135 * finds an entry in the specified directory with the wanted name. It
136 * returns the cache buffer in which the entry was found, and the entry
137 * itself (as a parameter - res_dir). It does NOT read the inode of the
138 * entry - you'll have to do that yourself if you want to.
139 *
140 * On Success dir_put_page() should be called on *res_page.
141 *
142 * sysv_find_entry() acts as a call to dir_get_page() and must be treated
143 * accordingly for nesting purposes.
144 */
sysv_find_entry(struct dentry * dentry,struct page ** res_page)145 struct sysv_dir_entry *sysv_find_entry(struct dentry *dentry, struct page **res_page)
146 {
147 const char * name = dentry->d_name.name;
148 int namelen = dentry->d_name.len;
149 struct inode * dir = d_inode(dentry->d_parent);
150 unsigned long start, n;
151 unsigned long npages = dir_pages(dir);
152 struct page *page = NULL;
153 struct sysv_dir_entry *de;
154
155 *res_page = NULL;
156
157 start = SYSV_I(dir)->i_dir_start_lookup;
158 if (start >= npages)
159 start = 0;
160 n = start;
161
162 do {
163 char *kaddr = dir_get_page(dir, n, &page);
164
165 if (!IS_ERR(kaddr)) {
166 de = (struct sysv_dir_entry *)kaddr;
167 kaddr += PAGE_SIZE - SYSV_DIRSIZE;
168 for ( ; (char *) de <= kaddr ; de++) {
169 if (!de->inode)
170 continue;
171 if (namecompare(namelen, SYSV_NAMELEN,
172 name, de->name))
173 goto found;
174 }
175 dir_put_page(page, kaddr);
176 }
177
178 if (++n >= npages)
179 n = 0;
180 } while (n != start);
181
182 return NULL;
183
184 found:
185 SYSV_I(dir)->i_dir_start_lookup = n;
186 *res_page = page;
187 return de;
188 }
189
sysv_add_link(struct dentry * dentry,struct inode * inode)190 int sysv_add_link(struct dentry *dentry, struct inode *inode)
191 {
192 struct inode *dir = d_inode(dentry->d_parent);
193 const char * name = dentry->d_name.name;
194 int namelen = dentry->d_name.len;
195 struct page *page = NULL;
196 struct sysv_dir_entry * de;
197 unsigned long npages = dir_pages(dir);
198 unsigned long n;
199 char *kaddr;
200 loff_t pos;
201 int err;
202
203 /* We take care of directory expansion in the same loop */
204 for (n = 0; n <= npages; n++) {
205 kaddr = dir_get_page(dir, n, &page);
206 if (IS_ERR(kaddr))
207 return PTR_ERR(kaddr);
208 de = (struct sysv_dir_entry *)kaddr;
209 kaddr += PAGE_SIZE - SYSV_DIRSIZE;
210 while ((char *)de <= kaddr) {
211 if (!de->inode)
212 goto got_it;
213 err = -EEXIST;
214 if (namecompare(namelen, SYSV_NAMELEN, name, de->name))
215 goto out_page;
216 de++;
217 }
218 dir_put_page(page, kaddr);
219 }
220 BUG();
221 return -EINVAL;
222
223 got_it:
224 pos = page_offset(page) + offset_in_page(de);
225 lock_page(page);
226 err = sysv_prepare_chunk(page, pos, SYSV_DIRSIZE);
227 if (err)
228 goto out_unlock;
229 memcpy (de->name, name, namelen);
230 memset (de->name + namelen, 0, SYSV_DIRSIZE - namelen - 2);
231 de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino);
232 dir_commit_chunk(page, pos, SYSV_DIRSIZE);
233 dir->i_mtime = dir->i_ctime = current_time(dir);
234 mark_inode_dirty(dir);
235 err = sysv_handle_dirsync(dir);
236 out_page:
237 dir_put_page(page, kaddr);
238 return err;
239 out_unlock:
240 unlock_page(page);
241 goto out_page;
242 }
243
sysv_delete_entry(struct sysv_dir_entry * de,struct page * page)244 int sysv_delete_entry(struct sysv_dir_entry *de, struct page *page)
245 {
246 struct inode *inode = page->mapping->host;
247 loff_t pos = page_offset(page) + offset_in_page(de);
248 int err;
249
250 lock_page(page);
251 err = sysv_prepare_chunk(page, pos, SYSV_DIRSIZE);
252 if (err) {
253 unlock_page(page);
254 return err;
255 }
256 de->inode = 0;
257 dir_commit_chunk(page, pos, SYSV_DIRSIZE);
258 inode->i_ctime = inode->i_mtime = current_time(inode);
259 mark_inode_dirty(inode);
260 return sysv_handle_dirsync(inode);
261 }
262
sysv_make_empty(struct inode * inode,struct inode * dir)263 int sysv_make_empty(struct inode *inode, struct inode *dir)
264 {
265 struct page *page = grab_cache_page(inode->i_mapping, 0);
266 struct sysv_dir_entry * de;
267 char *base;
268 int err;
269
270 if (!page)
271 return -ENOMEM;
272 err = sysv_prepare_chunk(page, 0, 2 * SYSV_DIRSIZE);
273 if (err) {
274 unlock_page(page);
275 goto fail;
276 }
277 base = kmap_local_page(page);
278 memset(base, 0, PAGE_SIZE);
279
280 de = (struct sysv_dir_entry *) base;
281 de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino);
282 strcpy(de->name,".");
283 de++;
284 de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), dir->i_ino);
285 strcpy(de->name,"..");
286
287 kunmap_local(base);
288 dir_commit_chunk(page, 0, 2 * SYSV_DIRSIZE);
289 err = sysv_handle_dirsync(inode);
290 fail:
291 put_page(page);
292 return err;
293 }
294
295 /*
296 * routine to check that the specified directory is empty (for rmdir)
297 */
sysv_empty_dir(struct inode * inode)298 int sysv_empty_dir(struct inode * inode)
299 {
300 struct super_block *sb = inode->i_sb;
301 struct page *page = NULL;
302 unsigned long i, npages = dir_pages(inode);
303 char *kaddr;
304
305 for (i = 0; i < npages; i++) {
306 struct sysv_dir_entry *de;
307
308 kaddr = dir_get_page(inode, i, &page);
309 if (IS_ERR(kaddr))
310 continue;
311
312 de = (struct sysv_dir_entry *)kaddr;
313 kaddr += PAGE_SIZE-SYSV_DIRSIZE;
314
315 for ( ;(char *)de <= kaddr; de++) {
316 if (!de->inode)
317 continue;
318 /* check for . and .. */
319 if (de->name[0] != '.')
320 goto not_empty;
321 if (!de->name[1]) {
322 if (de->inode == cpu_to_fs16(SYSV_SB(sb),
323 inode->i_ino))
324 continue;
325 goto not_empty;
326 }
327 if (de->name[1] != '.' || de->name[2])
328 goto not_empty;
329 }
330 dir_put_page(page, kaddr);
331 }
332 return 1;
333
334 not_empty:
335 dir_put_page(page, kaddr);
336 return 0;
337 }
338
339 /* Releases the page */
sysv_set_link(struct sysv_dir_entry * de,struct page * page,struct inode * inode)340 int sysv_set_link(struct sysv_dir_entry *de, struct page *page,
341 struct inode *inode)
342 {
343 struct inode *dir = page->mapping->host;
344 loff_t pos = page_offset(page) + offset_in_page(de);
345 int err;
346
347 lock_page(page);
348 err = sysv_prepare_chunk(page, pos, SYSV_DIRSIZE);
349 if (err) {
350 unlock_page(page);
351 return err;
352 }
353 de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino);
354 dir_commit_chunk(page, pos, SYSV_DIRSIZE);
355 dir->i_mtime = dir->i_ctime = current_time(dir);
356 mark_inode_dirty(dir);
357 return sysv_handle_dirsync(inode);
358 }
359
360 /*
361 * Calls to dir_get_page()/dir_put_page() must be nested according to the
362 * rules documented in mm/highmem.rst.
363 *
364 * sysv_dotdot() acts as a call to dir_get_page() and must be treated
365 * accordingly for nesting purposes.
366 */
sysv_dotdot(struct inode * dir,struct page ** p)367 struct sysv_dir_entry *sysv_dotdot(struct inode *dir, struct page **p)
368 {
369 struct sysv_dir_entry *de = dir_get_page(dir, 0, p);
370
371 if (IS_ERR(de))
372 return NULL;
373 /* ".." is the second directory entry */
374 return de + 1;
375 }
376
sysv_inode_by_name(struct dentry * dentry)377 ino_t sysv_inode_by_name(struct dentry *dentry)
378 {
379 struct page *page;
380 struct sysv_dir_entry *de = sysv_find_entry (dentry, &page);
381 ino_t res = 0;
382
383 if (de) {
384 res = fs16_to_cpu(SYSV_SB(dentry->d_sb), de->inode);
385 dir_put_page(page, de);
386 }
387 return res;
388 }
389