blob: 9c50523382e7eced4a45a44ce64e07ebaca5d9c5 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * fs/libfs.c
3 * Library for filesystems writers.
4 */
5
6#include <linux/module.h>
7#include <linux/pagemap.h>
8#include <linux/mount.h>
9#include <linux/vfs.h>
10#include <asm/uaccess.h>
11
12int simple_getattr(struct vfsmount *mnt, struct dentry *dentry,
13 struct kstat *stat)
14{
15 struct inode *inode = dentry->d_inode;
16 generic_fillattr(inode, stat);
17 stat->blocks = inode->i_mapping->nrpages << (PAGE_CACHE_SHIFT - 9);
18 return 0;
19}
20
21int simple_statfs(struct super_block *sb, struct kstatfs *buf)
22{
23 buf->f_type = sb->s_magic;
24 buf->f_bsize = PAGE_CACHE_SIZE;
25 buf->f_namelen = NAME_MAX;
26 return 0;
27}
28
29/*
30 * Retaining negative dentries for an in-memory filesystem just wastes
31 * memory and lookup time: arrange for them to be deleted immediately.
32 */
33static int simple_delete_dentry(struct dentry *dentry)
34{
35 return 1;
36}
37
38/*
39 * Lookup the data. This is trivial - if the dentry didn't already
40 * exist, we know it is negative. Set d_op to delete negative dentries.
41 */
42struct dentry *simple_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
43{
44 static struct dentry_operations simple_dentry_operations = {
45 .d_delete = simple_delete_dentry,
46 };
47
48 if (dentry->d_name.len > NAME_MAX)
49 return ERR_PTR(-ENAMETOOLONG);
50 dentry->d_op = &simple_dentry_operations;
51 d_add(dentry, NULL);
52 return NULL;
53}
54
55int simple_sync_file(struct file * file, struct dentry *dentry, int datasync)
56{
57 return 0;
58}
59
60int dcache_dir_open(struct inode *inode, struct file *file)
61{
62 static struct qstr cursor_name = {.len = 1, .name = "."};
63
64 file->private_data = d_alloc(file->f_dentry, &cursor_name);
65
66 return file->private_data ? 0 : -ENOMEM;
67}
68
69int dcache_dir_close(struct inode *inode, struct file *file)
70{
71 dput(file->private_data);
72 return 0;
73}
74
75loff_t dcache_dir_lseek(struct file *file, loff_t offset, int origin)
76{
77 down(&file->f_dentry->d_inode->i_sem);
78 switch (origin) {
79 case 1:
80 offset += file->f_pos;
81 case 0:
82 if (offset >= 0)
83 break;
84 default:
85 up(&file->f_dentry->d_inode->i_sem);
86 return -EINVAL;
87 }
88 if (offset != file->f_pos) {
89 file->f_pos = offset;
90 if (file->f_pos >= 2) {
91 struct list_head *p;
92 struct dentry *cursor = file->private_data;
93 loff_t n = file->f_pos - 2;
94
95 spin_lock(&dcache_lock);
Eric Dumazet5160ee62006-01-08 01:03:32 -080096 list_del(&cursor->d_u.d_child);
Linus Torvalds1da177e2005-04-16 15:20:36 -070097 p = file->f_dentry->d_subdirs.next;
98 while (n && p != &file->f_dentry->d_subdirs) {
99 struct dentry *next;
Eric Dumazet5160ee62006-01-08 01:03:32 -0800100 next = list_entry(p, struct dentry, d_u.d_child);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700101 if (!d_unhashed(next) && next->d_inode)
102 n--;
103 p = p->next;
104 }
Eric Dumazet5160ee62006-01-08 01:03:32 -0800105 list_add_tail(&cursor->d_u.d_child, p);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700106 spin_unlock(&dcache_lock);
107 }
108 }
109 up(&file->f_dentry->d_inode->i_sem);
110 return offset;
111}
112
113/* Relationship between i_mode and the DT_xxx types */
114static inline unsigned char dt_type(struct inode *inode)
115{
116 return (inode->i_mode >> 12) & 15;
117}
118
119/*
120 * Directory is locked and all positive dentries in it are safe, since
121 * for ramfs-type trees they can't go away without unlink() or rmdir(),
122 * both impossible due to the lock on directory.
123 */
124
125int dcache_readdir(struct file * filp, void * dirent, filldir_t filldir)
126{
127 struct dentry *dentry = filp->f_dentry;
128 struct dentry *cursor = filp->private_data;
Eric Dumazet5160ee62006-01-08 01:03:32 -0800129 struct list_head *p, *q = &cursor->d_u.d_child;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700130 ino_t ino;
131 int i = filp->f_pos;
132
133 switch (i) {
134 case 0:
135 ino = dentry->d_inode->i_ino;
136 if (filldir(dirent, ".", 1, i, ino, DT_DIR) < 0)
137 break;
138 filp->f_pos++;
139 i++;
140 /* fallthrough */
141 case 1:
142 ino = parent_ino(dentry);
143 if (filldir(dirent, "..", 2, i, ino, DT_DIR) < 0)
144 break;
145 filp->f_pos++;
146 i++;
147 /* fallthrough */
148 default:
149 spin_lock(&dcache_lock);
150 if (filp->f_pos == 2) {
151 list_del(q);
152 list_add(q, &dentry->d_subdirs);
153 }
154 for (p=q->next; p != &dentry->d_subdirs; p=p->next) {
155 struct dentry *next;
Eric Dumazet5160ee62006-01-08 01:03:32 -0800156 next = list_entry(p, struct dentry, d_u.d_child);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700157 if (d_unhashed(next) || !next->d_inode)
158 continue;
159
160 spin_unlock(&dcache_lock);
161 if (filldir(dirent, next->d_name.name, next->d_name.len, filp->f_pos, next->d_inode->i_ino, dt_type(next->d_inode)) < 0)
162 return 0;
163 spin_lock(&dcache_lock);
164 /* next is still alive */
165 list_del(q);
166 list_add(q, p);
167 p = q;
168 filp->f_pos++;
169 }
170 spin_unlock(&dcache_lock);
171 }
172 return 0;
173}
174
175ssize_t generic_read_dir(struct file *filp, char __user *buf, size_t siz, loff_t *ppos)
176{
177 return -EISDIR;
178}
179
180struct file_operations simple_dir_operations = {
181 .open = dcache_dir_open,
182 .release = dcache_dir_close,
183 .llseek = dcache_dir_lseek,
184 .read = generic_read_dir,
185 .readdir = dcache_readdir,
Hugh Dickins8ae0b772005-06-25 14:55:41 -0700186 .fsync = simple_sync_file,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700187};
188
189struct inode_operations simple_dir_inode_operations = {
190 .lookup = simple_lookup,
191};
192
193/*
194 * Common helper for pseudo-filesystems (sockfs, pipefs, bdev - stuff that
195 * will never be mountable)
196 */
197struct super_block *
198get_sb_pseudo(struct file_system_type *fs_type, char *name,
199 struct super_operations *ops, unsigned long magic)
200{
201 struct super_block *s = sget(fs_type, NULL, set_anon_super, NULL);
202 static struct super_operations default_ops = {.statfs = simple_statfs};
203 struct dentry *dentry;
204 struct inode *root;
205 struct qstr d_name = {.name = name, .len = strlen(name)};
206
207 if (IS_ERR(s))
208 return s;
209
210 s->s_flags = MS_NOUSER;
211 s->s_maxbytes = ~0ULL;
212 s->s_blocksize = 1024;
213 s->s_blocksize_bits = 10;
214 s->s_magic = magic;
215 s->s_op = ops ? ops : &default_ops;
216 s->s_time_gran = 1;
217 root = new_inode(s);
218 if (!root)
219 goto Enomem;
220 root->i_mode = S_IFDIR | S_IRUSR | S_IWUSR;
221 root->i_uid = root->i_gid = 0;
222 root->i_atime = root->i_mtime = root->i_ctime = CURRENT_TIME;
223 dentry = d_alloc(NULL, &d_name);
224 if (!dentry) {
225 iput(root);
226 goto Enomem;
227 }
228 dentry->d_sb = s;
229 dentry->d_parent = dentry;
230 d_instantiate(dentry, root);
231 s->s_root = dentry;
232 s->s_flags |= MS_ACTIVE;
233 return s;
234
235Enomem:
236 up_write(&s->s_umount);
237 deactivate_super(s);
238 return ERR_PTR(-ENOMEM);
239}
240
241int simple_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
242{
243 struct inode *inode = old_dentry->d_inode;
244
245 inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
246 inode->i_nlink++;
247 atomic_inc(&inode->i_count);
248 dget(dentry);
249 d_instantiate(dentry, inode);
250 return 0;
251}
252
253static inline int simple_positive(struct dentry *dentry)
254{
255 return dentry->d_inode && !d_unhashed(dentry);
256}
257
258int simple_empty(struct dentry *dentry)
259{
260 struct dentry *child;
261 int ret = 0;
262
263 spin_lock(&dcache_lock);
Eric Dumazet5160ee62006-01-08 01:03:32 -0800264 list_for_each_entry(child, &dentry->d_subdirs, d_u.d_child)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700265 if (simple_positive(child))
266 goto out;
267 ret = 1;
268out:
269 spin_unlock(&dcache_lock);
270 return ret;
271}
272
273int simple_unlink(struct inode *dir, struct dentry *dentry)
274{
275 struct inode *inode = dentry->d_inode;
276
277 inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
278 inode->i_nlink--;
279 dput(dentry);
280 return 0;
281}
282
283int simple_rmdir(struct inode *dir, struct dentry *dentry)
284{
285 if (!simple_empty(dentry))
286 return -ENOTEMPTY;
287
288 dentry->d_inode->i_nlink--;
289 simple_unlink(dir, dentry);
290 dir->i_nlink--;
291 return 0;
292}
293
294int simple_rename(struct inode *old_dir, struct dentry *old_dentry,
295 struct inode *new_dir, struct dentry *new_dentry)
296{
297 struct inode *inode = old_dentry->d_inode;
298 int they_are_dirs = S_ISDIR(old_dentry->d_inode->i_mode);
299
300 if (!simple_empty(new_dentry))
301 return -ENOTEMPTY;
302
303 if (new_dentry->d_inode) {
304 simple_unlink(new_dir, new_dentry);
305 if (they_are_dirs)
306 old_dir->i_nlink--;
307 } else if (they_are_dirs) {
308 old_dir->i_nlink--;
309 new_dir->i_nlink++;
310 }
311
312 old_dir->i_ctime = old_dir->i_mtime = new_dir->i_ctime =
313 new_dir->i_mtime = inode->i_ctime = CURRENT_TIME;
314
315 return 0;
316}
317
318int simple_readpage(struct file *file, struct page *page)
319{
320 void *kaddr;
321
322 if (PageUptodate(page))
323 goto out;
324
325 kaddr = kmap_atomic(page, KM_USER0);
326 memset(kaddr, 0, PAGE_CACHE_SIZE);
327 kunmap_atomic(kaddr, KM_USER0);
328 flush_dcache_page(page);
329 SetPageUptodate(page);
330out:
331 unlock_page(page);
332 return 0;
333}
334
335int simple_prepare_write(struct file *file, struct page *page,
336 unsigned from, unsigned to)
337{
338 if (!PageUptodate(page)) {
339 if (to - from != PAGE_CACHE_SIZE) {
340 void *kaddr = kmap_atomic(page, KM_USER0);
341 memset(kaddr, 0, from);
342 memset(kaddr + to, 0, PAGE_CACHE_SIZE - to);
343 flush_dcache_page(page);
344 kunmap_atomic(kaddr, KM_USER0);
345 }
346 SetPageUptodate(page);
347 }
348 return 0;
349}
350
351int simple_commit_write(struct file *file, struct page *page,
352 unsigned offset, unsigned to)
353{
354 struct inode *inode = page->mapping->host;
355 loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to;
356
357 /*
358 * No need to use i_size_read() here, the i_size
359 * cannot change under us because we hold the i_sem.
360 */
361 if (pos > inode->i_size)
362 i_size_write(inode, pos);
363 set_page_dirty(page);
364 return 0;
365}
366
367int simple_fill_super(struct super_block *s, int magic, struct tree_descr *files)
368{
369 static struct super_operations s_ops = {.statfs = simple_statfs};
370 struct inode *inode;
371 struct dentry *root;
372 struct dentry *dentry;
373 int i;
374
375 s->s_blocksize = PAGE_CACHE_SIZE;
376 s->s_blocksize_bits = PAGE_CACHE_SHIFT;
377 s->s_magic = magic;
378 s->s_op = &s_ops;
379 s->s_time_gran = 1;
380
381 inode = new_inode(s);
382 if (!inode)
383 return -ENOMEM;
384 inode->i_mode = S_IFDIR | 0755;
385 inode->i_uid = inode->i_gid = 0;
386 inode->i_blksize = PAGE_CACHE_SIZE;
387 inode->i_blocks = 0;
388 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
389 inode->i_op = &simple_dir_inode_operations;
390 inode->i_fop = &simple_dir_operations;
391 root = d_alloc_root(inode);
392 if (!root) {
393 iput(inode);
394 return -ENOMEM;
395 }
396 for (i = 0; !files->name || files->name[0]; i++, files++) {
397 if (!files->name)
398 continue;
399 dentry = d_alloc_name(root, files->name);
400 if (!dentry)
401 goto out;
402 inode = new_inode(s);
403 if (!inode)
404 goto out;
405 inode->i_mode = S_IFREG | files->mode;
406 inode->i_uid = inode->i_gid = 0;
407 inode->i_blksize = PAGE_CACHE_SIZE;
408 inode->i_blocks = 0;
409 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
410 inode->i_fop = files->ops;
411 inode->i_ino = i;
412 d_add(dentry, inode);
413 }
414 s->s_root = root;
415 return 0;
416out:
417 d_genocide(root);
418 dput(root);
419 return -ENOMEM;
420}
421
422static DEFINE_SPINLOCK(pin_fs_lock);
423
424int simple_pin_fs(char *name, struct vfsmount **mount, int *count)
425{
426 struct vfsmount *mnt = NULL;
427 spin_lock(&pin_fs_lock);
428 if (unlikely(!*mount)) {
429 spin_unlock(&pin_fs_lock);
430 mnt = do_kern_mount(name, 0, name, NULL);
431 if (IS_ERR(mnt))
432 return PTR_ERR(mnt);
433 spin_lock(&pin_fs_lock);
434 if (!*mount)
435 *mount = mnt;
436 }
437 mntget(*mount);
438 ++*count;
439 spin_unlock(&pin_fs_lock);
440 mntput(mnt);
441 return 0;
442}
443
444void simple_release_fs(struct vfsmount **mount, int *count)
445{
446 struct vfsmount *mnt;
447 spin_lock(&pin_fs_lock);
448 mnt = *mount;
449 if (!--*count)
450 *mount = NULL;
451 spin_unlock(&pin_fs_lock);
452 mntput(mnt);
453}
454
455ssize_t simple_read_from_buffer(void __user *to, size_t count, loff_t *ppos,
456 const void *from, size_t available)
457{
458 loff_t pos = *ppos;
459 if (pos < 0)
460 return -EINVAL;
461 if (pos >= available)
462 return 0;
463 if (count > available - pos)
464 count = available - pos;
465 if (copy_to_user(to, from + pos, count))
466 return -EFAULT;
467 *ppos = pos + count;
468 return count;
469}
470
471/*
472 * Transaction based IO.
473 * The file expects a single write which triggers the transaction, and then
474 * possibly a read which collects the result - which is stored in a
475 * file-local buffer.
476 */
477char *simple_transaction_get(struct file *file, const char __user *buf, size_t size)
478{
479 struct simple_transaction_argresp *ar;
480 static DEFINE_SPINLOCK(simple_transaction_lock);
481
482 if (size > SIMPLE_TRANSACTION_LIMIT - 1)
483 return ERR_PTR(-EFBIG);
484
485 ar = (struct simple_transaction_argresp *)get_zeroed_page(GFP_KERNEL);
486 if (!ar)
487 return ERR_PTR(-ENOMEM);
488
489 spin_lock(&simple_transaction_lock);
490
491 /* only one write allowed per open */
492 if (file->private_data) {
493 spin_unlock(&simple_transaction_lock);
494 free_page((unsigned long)ar);
495 return ERR_PTR(-EBUSY);
496 }
497
498 file->private_data = ar;
499
500 spin_unlock(&simple_transaction_lock);
501
502 if (copy_from_user(ar->data, buf, size))
503 return ERR_PTR(-EFAULT);
504
505 return ar->data;
506}
507
508ssize_t simple_transaction_read(struct file *file, char __user *buf, size_t size, loff_t *pos)
509{
510 struct simple_transaction_argresp *ar = file->private_data;
511
512 if (!ar)
513 return 0;
514 return simple_read_from_buffer(buf, size, pos, ar->data, ar->size);
515}
516
517int simple_transaction_release(struct inode *inode, struct file *file)
518{
519 free_page((unsigned long)file->private_data);
520 return 0;
521}
522
Arnd Bergmannacaefc22005-05-18 14:40:59 +0200523/* Simple attribute files */
524
525struct simple_attr {
526 u64 (*get)(void *);
527 void (*set)(void *, u64);
528 char get_buf[24]; /* enough to store a u64 and "\n\0" */
529 char set_buf[24];
530 void *data;
531 const char *fmt; /* format for read operation */
532 struct semaphore sem; /* protects access to these buffers */
533};
534
535/* simple_attr_open is called by an actual attribute open file operation
536 * to set the attribute specific access operations. */
537int simple_attr_open(struct inode *inode, struct file *file,
538 u64 (*get)(void *), void (*set)(void *, u64),
539 const char *fmt)
540{
541 struct simple_attr *attr;
542
543 attr = kmalloc(sizeof(*attr), GFP_KERNEL);
544 if (!attr)
545 return -ENOMEM;
546
547 attr->get = get;
548 attr->set = set;
549 attr->data = inode->u.generic_ip;
550 attr->fmt = fmt;
551 init_MUTEX(&attr->sem);
552
553 file->private_data = attr;
554
555 return nonseekable_open(inode, file);
556}
557
558int simple_attr_close(struct inode *inode, struct file *file)
559{
560 kfree(file->private_data);
561 return 0;
562}
563
564/* read from the buffer that is filled with the get function */
565ssize_t simple_attr_read(struct file *file, char __user *buf,
566 size_t len, loff_t *ppos)
567{
568 struct simple_attr *attr;
569 size_t size;
570 ssize_t ret;
571
572 attr = file->private_data;
573
574 if (!attr->get)
575 return -EACCES;
576
577 down(&attr->sem);
578 if (*ppos) /* continued read */
579 size = strlen(attr->get_buf);
580 else /* first read */
581 size = scnprintf(attr->get_buf, sizeof(attr->get_buf),
582 attr->fmt,
583 (unsigned long long)attr->get(attr->data));
584
585 ret = simple_read_from_buffer(buf, len, ppos, attr->get_buf, size);
586 up(&attr->sem);
587 return ret;
588}
589
590/* interpret the buffer as a number to call the set function with */
591ssize_t simple_attr_write(struct file *file, const char __user *buf,
592 size_t len, loff_t *ppos)
593{
594 struct simple_attr *attr;
595 u64 val;
596 size_t size;
597 ssize_t ret;
598
599 attr = file->private_data;
600
601 if (!attr->set)
602 return -EACCES;
603
604 down(&attr->sem);
605 ret = -EFAULT;
606 size = min(sizeof(attr->set_buf) - 1, len);
607 if (copy_from_user(attr->set_buf, buf, size))
608 goto out;
609
610 ret = len; /* claim we got the whole input */
611 attr->set_buf[size] = '\0';
612 val = simple_strtol(attr->set_buf, NULL, 0);
613 attr->set(attr->data, val);
614out:
615 up(&attr->sem);
616 return ret;
617}
618
Linus Torvalds1da177e2005-04-16 15:20:36 -0700619EXPORT_SYMBOL(dcache_dir_close);
620EXPORT_SYMBOL(dcache_dir_lseek);
621EXPORT_SYMBOL(dcache_dir_open);
622EXPORT_SYMBOL(dcache_readdir);
623EXPORT_SYMBOL(generic_read_dir);
624EXPORT_SYMBOL(get_sb_pseudo);
625EXPORT_SYMBOL(simple_commit_write);
626EXPORT_SYMBOL(simple_dir_inode_operations);
627EXPORT_SYMBOL(simple_dir_operations);
628EXPORT_SYMBOL(simple_empty);
629EXPORT_SYMBOL(d_alloc_name);
630EXPORT_SYMBOL(simple_fill_super);
631EXPORT_SYMBOL(simple_getattr);
632EXPORT_SYMBOL(simple_link);
633EXPORT_SYMBOL(simple_lookup);
634EXPORT_SYMBOL(simple_pin_fs);
635EXPORT_SYMBOL(simple_prepare_write);
636EXPORT_SYMBOL(simple_readpage);
637EXPORT_SYMBOL(simple_release_fs);
638EXPORT_SYMBOL(simple_rename);
639EXPORT_SYMBOL(simple_rmdir);
640EXPORT_SYMBOL(simple_statfs);
641EXPORT_SYMBOL(simple_sync_file);
642EXPORT_SYMBOL(simple_unlink);
643EXPORT_SYMBOL(simple_read_from_buffer);
644EXPORT_SYMBOL(simple_transaction_get);
645EXPORT_SYMBOL(simple_transaction_read);
646EXPORT_SYMBOL(simple_transaction_release);
Arnd Bergmannacaefc22005-05-18 14:40:59 +0200647EXPORT_SYMBOL_GPL(simple_attr_open);
648EXPORT_SYMBOL_GPL(simple_attr_close);
649EXPORT_SYMBOL_GPL(simple_attr_read);
650EXPORT_SYMBOL_GPL(simple_attr_write);