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