dir.c

  1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 *  linux/fs/minix/dir.c
  4 *
  5 *  Copyright (C) 1991, 1992 Linus Torvalds
  6 *
  7 *  minix directory handling functions
  8 *
  9 *  Updated to filesystem version 3 by Daniel Aragones
 10 */
 11
 12#include "minix.h"
 13#include <linux/buffer_head.h>
 14#include <linux/highmem.h>
 15#include <linux/swap.h>
 16
 17typedef struct minix_dir_entry minix_dirent;
 18typedef struct minix3_dir_entry minix3_dirent;
 19
 20static int minix_readdir(struct file *, struct dir_context *);
 21
 22const struct file_operations minix_dir_operations = {
 23	.llseek		= generic_file_llseek,
 24	.read		= generic_read_dir,
 25	.iterate_shared	= minix_readdir,
 26	.fsync		= generic_file_fsync,
 27};
 28
 29/*
 30 * Return the offset into page `page_nr' of the last valid
 31 * byte in that page, plus one.
 32 */
 33static unsigned
 34minix_last_byte(struct inode *inode, unsigned long page_nr)
 35{
 36	unsigned last_byte = PAGE_SIZE;
 37
 38	if (page_nr == (inode->i_size >> PAGE_SHIFT))
 39		last_byte = inode->i_size & (PAGE_SIZE - 1);
 40	return last_byte;
 41}
 42
 43static void dir_commit_chunk(struct folio *folio, loff_t pos, unsigned len)
 44{
 45	struct address_space *mapping = folio->mapping;
 46	struct inode *dir = mapping->host;
 47
 48	block_write_end(pos, len, len, folio);
 49
 50	if (pos+len > dir->i_size) {
 51		i_size_write(dir, pos+len);
 52		mark_inode_dirty(dir);
 53	}
 54	folio_unlock(folio);
 55}
 56
 57static int minix_handle_dirsync(struct inode *dir)
 58{
 59	int err;
 60
 61	err = filemap_write_and_wait(dir->i_mapping);
 62	if (!err)
 63		err = sync_inode_metadata(dir, 1);
 64	return err;
 65}
 66
 67static void *dir_get_folio(struct inode *dir, unsigned long n,
 68		struct folio **foliop)
 69{
 70	struct folio *folio = read_mapping_folio(dir->i_mapping, n, NULL);
 71
 72	if (IS_ERR(folio))
 73		return ERR_CAST(folio);
 74	*foliop = folio;
 75	return kmap_local_folio(folio, 0);
 76}
 77
 78static inline void *minix_next_entry(void *de, struct minix_sb_info *sbi)
 79{
 80	return (void*)((char*)de + sbi->s_dirsize);
 81}
 82
 83static int minix_readdir(struct file *file, struct dir_context *ctx)
 84{
 85	struct inode *inode = file_inode(file);
 86	struct super_block *sb = inode->i_sb;
 87	struct minix_sb_info *sbi = minix_sb(sb);
 88	unsigned chunk_size = sbi->s_dirsize;
 89	unsigned long npages = dir_pages(inode);
 90	unsigned long pos = ctx->pos;
 91	unsigned offset;
 92	unsigned long n;
 93
 94	ctx->pos = pos = ALIGN(pos, chunk_size);
 95	if (pos >= inode->i_size)
 96		return 0;
 97
 98	offset = pos & ~PAGE_MASK;
 99	n = pos >> PAGE_SHIFT;
100
101	for ( ; n < npages; n++, offset = 0) {
102		char *p, *kaddr, *limit;
103		struct folio *folio;
104
105		kaddr = dir_get_folio(inode, n, &folio);
106		if (IS_ERR(kaddr))
107			continue;
108		p = kaddr+offset;
109		limit = kaddr + minix_last_byte(inode, n) - chunk_size;
110		for ( ; p <= limit; p = minix_next_entry(p, sbi)) {
111			const char *name;
112			__u32 inumber;
113			if (sbi->s_version == MINIX_V3) {
114				minix3_dirent *de3 = (minix3_dirent *)p;
115				name = de3->name;
116				inumber = de3->inode;
117	 		} else {
118				minix_dirent *de = (minix_dirent *)p;
119				name = de->name;
120				inumber = de->inode;
121			}
122			if (inumber) {
123				unsigned l = strnlen(name, sbi->s_namelen);
124				if (!dir_emit(ctx, name, l,
125					      inumber, DT_UNKNOWN)) {
126					folio_release_kmap(folio, p);
127					return 0;
128				}
129			}
130			ctx->pos += chunk_size;
131		}
132		folio_release_kmap(folio, kaddr);
133	}
134	return 0;
135}
136
137static inline int namecompare(int len, int maxlen,
138	const char * name, const char * buffer)
139{
140	if (len < maxlen && buffer[len])
141		return 0;
142	return !memcmp(name, buffer, len);
143}
144
145/*
146 *	minix_find_entry()
147 *
148 * finds an entry in the specified directory with the wanted name.
149 * It does NOT read the inode of the
150 * entry - you'll have to do that yourself if you want to.
151 * 
152 * On Success folio_release_kmap() should be called on *foliop.
153 */
154minix_dirent *minix_find_entry(struct dentry *dentry, struct folio **foliop)
155{
156	const char * name = dentry->d_name.name;
157	int namelen = dentry->d_name.len;
158	struct inode * dir = d_inode(dentry->d_parent);
159	struct super_block * sb = dir->i_sb;
160	struct minix_sb_info * sbi = minix_sb(sb);
161	unsigned long n;
162	unsigned long npages = dir_pages(dir);
163	char *p;
164
165	char *namx;
166	__u32 inumber;
167
168	for (n = 0; n < npages; n++) {
169		char *kaddr, *limit;
170
171		kaddr = dir_get_folio(dir, n, foliop);
172		if (IS_ERR(kaddr))
173			continue;
174
175		limit = kaddr + minix_last_byte(dir, n) - sbi->s_dirsize;
176		for (p = kaddr; p <= limit; p = minix_next_entry(p, sbi)) {
177			if (sbi->s_version == MINIX_V3) {
178				minix3_dirent *de3 = (minix3_dirent *)p;
179				namx = de3->name;
180				inumber = de3->inode;
181 			} else {
182				minix_dirent *de = (minix_dirent *)p;
183				namx = de->name;
184				inumber = de->inode;
185			}
186			if (!inumber)
187				continue;
188			if (namecompare(namelen, sbi->s_namelen, name, namx))
189				goto found;
190		}
191		folio_release_kmap(*foliop, kaddr);
192	}
193	return NULL;
194
195found:
196	return (minix_dirent *)p;
197}
198
199int minix_add_link(struct dentry *dentry, struct inode *inode)
200{
201	struct inode *dir = d_inode(dentry->d_parent);
202	const char * name = dentry->d_name.name;
203	int namelen = dentry->d_name.len;
204	struct super_block * sb = dir->i_sb;
205	struct minix_sb_info * sbi = minix_sb(sb);
206	struct folio *folio = NULL;
207	unsigned long npages = dir_pages(dir);
208	unsigned long n;
209	char *kaddr, *p;
210	minix_dirent *de;
211	minix3_dirent *de3;
212	loff_t pos;
213	int err;
214	char *namx = NULL;
215	__u32 inumber;
216
217	/*
218	 * We take care of directory expansion in the same loop
219	 * This code plays outside i_size, so it locks the page
220	 * to protect that region.
221	 */
222	for (n = 0; n <= npages; n++) {
223		char *limit, *dir_end;
224
225		kaddr = dir_get_folio(dir, n, &folio);
226		if (IS_ERR(kaddr))
227			return PTR_ERR(kaddr);
228		folio_lock(folio);
229		dir_end = kaddr + minix_last_byte(dir, n);
230		limit = kaddr + PAGE_SIZE - sbi->s_dirsize;
231		for (p = kaddr; p <= limit; p = minix_next_entry(p, sbi)) {
232			de = (minix_dirent *)p;
233			de3 = (minix3_dirent *)p;
234			if (sbi->s_version == MINIX_V3) {
235				namx = de3->name;
236				inumber = de3->inode;
237		 	} else {
238  				namx = de->name;
239				inumber = de->inode;
240			}
241			if (p == dir_end) {
242				/* We hit i_size */
243				if (sbi->s_version == MINIX_V3)
244					de3->inode = 0;
245		 		else
246					de->inode = 0;
247				goto got_it;
248			}
249			if (!inumber)
250				goto got_it;
251			err = -EEXIST;
252			if (namecompare(namelen, sbi->s_namelen, name, namx))
253				goto out_unlock;
254		}
255		folio_unlock(folio);
256		folio_release_kmap(folio, kaddr);
257	}
258	BUG();
259	return -EINVAL;
260
261got_it:
262	pos = folio_pos(folio) + offset_in_folio(folio, p);
263	err = minix_prepare_chunk(folio, pos, sbi->s_dirsize);
264	if (err)
265		goto out_unlock;
266	memcpy (namx, name, namelen);
267	if (sbi->s_version == MINIX_V3) {
268		memset (namx + namelen, 0, sbi->s_dirsize - namelen - 4);
269		de3->inode = inode->i_ino;
270	} else {
271		memset (namx + namelen, 0, sbi->s_dirsize - namelen - 2);
272		de->inode = inode->i_ino;
273	}
274	dir_commit_chunk(folio, pos, sbi->s_dirsize);
275	inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir));
276	mark_inode_dirty(dir);
277	err = minix_handle_dirsync(dir);
278out_put:
279	folio_release_kmap(folio, kaddr);
280	return err;
281out_unlock:
282	folio_unlock(folio);
283	goto out_put;
284}
285
286int minix_delete_entry(struct minix_dir_entry *de, struct folio *folio)
287{
288	struct inode *inode = folio->mapping->host;
289	loff_t pos = folio_pos(folio) + offset_in_folio(folio, de);
290	struct minix_sb_info *sbi = minix_sb(inode->i_sb);
291	unsigned len = sbi->s_dirsize;
292	int err;
293
294	folio_lock(folio);
295	err = minix_prepare_chunk(folio, pos, len);
296	if (err) {
297		folio_unlock(folio);
298		return err;
299	}
300	if (sbi->s_version == MINIX_V3)
301		((minix3_dirent *)de)->inode = 0;
302	else
303		de->inode = 0;
304	dir_commit_chunk(folio, pos, len);
305	inode_set_mtime_to_ts(inode, inode_set_ctime_current(inode));
306	mark_inode_dirty(inode);
307	return minix_handle_dirsync(inode);
308}
309
310int minix_make_empty(struct inode *inode, struct inode *dir)
311{
312	struct folio *folio = filemap_grab_folio(inode->i_mapping, 0);
313	struct minix_sb_info *sbi = minix_sb(inode->i_sb);
314	char *kaddr;
315	int err;
316
317	if (IS_ERR(folio))
318		return PTR_ERR(folio);
319	err = minix_prepare_chunk(folio, 0, 2 * sbi->s_dirsize);
320	if (err) {
321		folio_unlock(folio);
322		goto fail;
323	}
324
325	kaddr = kmap_local_folio(folio, 0);
326	memset(kaddr, 0, folio_size(folio));
327
328	if (sbi->s_version == MINIX_V3) {
329		minix3_dirent *de3 = (minix3_dirent *)kaddr;
330
331		de3->inode = inode->i_ino;
332		strcpy(de3->name, ".");
333		de3 = minix_next_entry(de3, sbi);
334		de3->inode = dir->i_ino;
335		strcpy(de3->name, "..");
336	} else {
337		minix_dirent *de = (minix_dirent *)kaddr;
338
339		de->inode = inode->i_ino;
340		strcpy(de->name, ".");
341		de = minix_next_entry(de, sbi);
342		de->inode = dir->i_ino;
343		strcpy(de->name, "..");
344	}
345	kunmap_local(kaddr);
346
347	dir_commit_chunk(folio, 0, 2 * sbi->s_dirsize);
348	err = minix_handle_dirsync(inode);
349fail:
350	folio_put(folio);
351	return err;
352}
353
354/*
355 * routine to check that the specified directory is empty (for rmdir)
356 */
357int minix_empty_dir(struct inode * inode)
358{
359	struct folio *folio = NULL;
360	unsigned long i, npages = dir_pages(inode);
361	struct minix_sb_info *sbi = minix_sb(inode->i_sb);
362	char *name, *kaddr;
363	__u32 inumber;
364
365	for (i = 0; i < npages; i++) {
366		char *p, *limit;
367
368		kaddr = dir_get_folio(inode, i, &folio);
369		if (IS_ERR(kaddr))
370			continue;
371
372		limit = kaddr + minix_last_byte(inode, i) - sbi->s_dirsize;
373		for (p = kaddr; p <= limit; p = minix_next_entry(p, sbi)) {
374			if (sbi->s_version == MINIX_V3) {
375				minix3_dirent *de3 = (minix3_dirent *)p;
376				name = de3->name;
377				inumber = de3->inode;
378			} else {
379				minix_dirent *de = (minix_dirent *)p;
380				name = de->name;
381				inumber = de->inode;
382			}
383
384			if (inumber != 0) {
385				/* check for . and .. */
386				if (name[0] != '.')
387					goto not_empty;
388				if (!name[1]) {
389					if (inumber != inode->i_ino)
390						goto not_empty;
391				} else if (name[1] != '.')
392					goto not_empty;
393				else if (name[2])
394					goto not_empty;
395			}
396		}
397		folio_release_kmap(folio, kaddr);
398	}
399	return 1;
400
401not_empty:
402	folio_release_kmap(folio, kaddr);
403	return 0;
404}
405
406/* Releases the page */
407int minix_set_link(struct minix_dir_entry *de, struct folio *folio,
408		struct inode *inode)
409{
410	struct inode *dir = folio->mapping->host;
411	struct minix_sb_info *sbi = minix_sb(dir->i_sb);
412	loff_t pos = folio_pos(folio) + offset_in_folio(folio, de);
413	int err;
414
415	folio_lock(folio);
416	err = minix_prepare_chunk(folio, pos, sbi->s_dirsize);
417	if (err) {
418		folio_unlock(folio);
419		return err;
420	}
421	if (sbi->s_version == MINIX_V3)
422		((minix3_dirent *)de)->inode = inode->i_ino;
423	else
424		de->inode = inode->i_ino;
425	dir_commit_chunk(folio, pos, sbi->s_dirsize);
426	inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir));
427	mark_inode_dirty(dir);
428	return minix_handle_dirsync(dir);
429}
430
431struct minix_dir_entry *minix_dotdot(struct inode *dir, struct folio **foliop)
432{
433	struct minix_sb_info *sbi = minix_sb(dir->i_sb);
434	struct minix_dir_entry *de = dir_get_folio(dir, 0, foliop);
435
436	if (!IS_ERR(de))
437		return minix_next_entry(de, sbi);
438	return NULL;
439}
440
441ino_t minix_inode_by_name(struct dentry *dentry)
442{
443	struct folio *folio;
444	struct minix_dir_entry *de = minix_find_entry(dentry, &folio);
445	ino_t res = 0;
446
447	if (de) {
448		struct inode *inode = folio->mapping->host;
449		struct minix_sb_info *sbi = minix_sb(inode->i_sb);
450
451		if (sbi->s_version == MINIX_V3)
452			res = ((minix3_dirent *) de)->inode;
453		else
454			res = de->inode;
455		folio_release_kmap(folio, de);
456	}
457	return res;
458}