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1 | /* |
2 | * fs/libfs.c |
3 | * Library for filesystems writers. |
4 | */ |
5 | |
6 | #include <linux/module.h> |
7 | #include <linux/pagemap.h> |
8 | #include <linux/slab.h> |
9 | #include <linux/mount.h> |
10 | #include <linux/vfs.h> |
11 | #include <linux/quotaops.h> |
12 | #include <linux/mutex.h> |
13 | #include <linux/exportfs.h> |
14 | #include <linux/writeback.h> |
15 | #include <linux/buffer_head.h> |
16 | |
17 | #include <asm/uaccess.h> |
18 | |
19 | int simple_getattr(struct vfsmount *mnt, struct dentry *dentry, |
20 | struct kstat *stat) |
21 | { |
22 | struct inode *inode = dentry->d_inode; |
23 | generic_fillattr(inode, stat); |
24 | stat->blocks = inode->i_mapping->nrpages << (PAGE_CACHE_SHIFT - 9); |
25 | return 0; |
26 | } |
27 | |
28 | int simple_statfs(struct dentry *dentry, struct kstatfs *buf) |
29 | { |
30 | buf->f_type = dentry->d_sb->s_magic; |
31 | buf->f_bsize = PAGE_CACHE_SIZE; |
32 | buf->f_namelen = NAME_MAX; |
33 | return 0; |
34 | } |
35 | |
36 | /* |
37 | * Retaining negative dentries for an in-memory filesystem just wastes |
38 | * memory and lookup time: arrange for them to be deleted immediately. |
39 | */ |
40 | static int simple_delete_dentry(struct dentry *dentry) |
41 | { |
42 | return 1; |
43 | } |
44 | |
45 | /* |
46 | * Lookup the data. This is trivial - if the dentry didn't already |
47 | * exist, we know it is negative. Set d_op to delete negative dentries. |
48 | */ |
49 | struct dentry *simple_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd) |
50 | { |
51 | static const struct dentry_operations simple_dentry_operations = { |
52 | .d_delete = simple_delete_dentry, |
53 | }; |
54 | |
55 | if (dentry->d_name.len > NAME_MAX) |
56 | return ERR_PTR(-ENAMETOOLONG); |
57 | dentry->d_op = &simple_dentry_operations; |
58 | d_add(dentry, NULL); |
59 | return NULL; |
60 | } |
61 | |
62 | int dcache_dir_open(struct inode *inode, struct file *file) |
63 | { |
64 | static struct qstr cursor_name = {.len = 1, .name = "."}; |
65 | |
66 | file->private_data = d_alloc(file->f_path.dentry, &cursor_name); |
67 | |
68 | return file->private_data ? 0 : -ENOMEM; |
69 | } |
70 | |
71 | int dcache_dir_close(struct inode *inode, struct file *file) |
72 | { |
73 | dput(file->private_data); |
74 | return 0; |
75 | } |
76 | |
77 | loff_t dcache_dir_lseek(struct file *file, loff_t offset, int origin) |
78 | { |
79 | mutex_lock(&file->f_path.dentry->d_inode->i_mutex); |
80 | switch (origin) { |
81 | case 1: |
82 | offset += file->f_pos; |
83 | case 0: |
84 | if (offset >= 0) |
85 | break; |
86 | default: |
87 | mutex_unlock(&file->f_path.dentry->d_inode->i_mutex); |
88 | return -EINVAL; |
89 | } |
90 | if (offset != file->f_pos) { |
91 | file->f_pos = offset; |
92 | if (file->f_pos >= 2) { |
93 | struct list_head *p; |
94 | struct dentry *cursor = file->private_data; |
95 | loff_t n = file->f_pos - 2; |
96 | |
97 | spin_lock(&dcache_lock); |
98 | list_del(&cursor->d_u.d_child); |
99 | p = file->f_path.dentry->d_subdirs.next; |
100 | while (n && p != &file->f_path.dentry->d_subdirs) { |
101 | struct dentry *next; |
102 | next = list_entry(p, struct dentry, d_u.d_child); |
103 | if (!d_unhashed(next) && next->d_inode) |
104 | n--; |
105 | p = p->next; |
106 | } |
107 | list_add_tail(&cursor->d_u.d_child, p); |
108 | spin_unlock(&dcache_lock); |
109 | } |
110 | } |
111 | mutex_unlock(&file->f_path.dentry->d_inode->i_mutex); |
112 | return offset; |
113 | } |
114 | |
115 | /* Relationship between i_mode and the DT_xxx types */ |
116 | static inline unsigned char dt_type(struct inode *inode) |
117 | { |
118 | return (inode->i_mode >> 12) & 15; |
119 | } |
120 | |
121 | /* |
122 | * Directory is locked and all positive dentries in it are safe, since |
123 | * for ramfs-type trees they can't go away without unlink() or rmdir(), |
124 | * both impossible due to the lock on directory. |
125 | */ |
126 | |
127 | int dcache_readdir(struct file * filp, void * dirent, filldir_t filldir) |
128 | { |
129 | struct dentry *dentry = filp->f_path.dentry; |
130 | struct dentry *cursor = filp->private_data; |
131 | struct list_head *p, *q = &cursor->d_u.d_child; |
132 | ino_t ino; |
133 | int i = filp->f_pos; |
134 | |
135 | switch (i) { |
136 | case 0: |
137 | ino = dentry->d_inode->i_ino; |
138 | if (filldir(dirent, ".", 1, i, ino, DT_DIR) < 0) |
139 | break; |
140 | filp->f_pos++; |
141 | i++; |
142 | /* fallthrough */ |
143 | case 1: |
144 | ino = parent_ino(dentry); |
145 | if (filldir(dirent, "..", 2, i, ino, DT_DIR) < 0) |
146 | break; |
147 | filp->f_pos++; |
148 | i++; |
149 | /* fallthrough */ |
150 | default: |
151 | spin_lock(&dcache_lock); |
152 | if (filp->f_pos == 2) |
153 | list_move(q, &dentry->d_subdirs); |
154 | |
155 | for (p=q->next; p != &dentry->d_subdirs; p=p->next) { |
156 | struct dentry *next; |
157 | next = list_entry(p, struct dentry, d_u.d_child); |
158 | if (d_unhashed(next) || !next->d_inode) |
159 | continue; |
160 | |
161 | spin_unlock(&dcache_lock); |
162 | if (filldir(dirent, next->d_name.name, |
163 | next->d_name.len, filp->f_pos, |
164 | next->d_inode->i_ino, |
165 | dt_type(next->d_inode)) < 0) |
166 | return 0; |
167 | spin_lock(&dcache_lock); |
168 | /* next is still alive */ |
169 | list_move(q, p); |
170 | p = q; |
171 | filp->f_pos++; |
172 | } |
173 | spin_unlock(&dcache_lock); |
174 | } |
175 | return 0; |
176 | } |
177 | |
178 | ssize_t generic_read_dir(struct file *filp, char __user *buf, size_t siz, loff_t *ppos) |
179 | { |
180 | return -EISDIR; |
181 | } |
182 | |
183 | const struct file_operations simple_dir_operations = { |
184 | .open = dcache_dir_open, |
185 | .release = dcache_dir_close, |
186 | .llseek = dcache_dir_lseek, |
187 | .read = generic_read_dir, |
188 | .readdir = dcache_readdir, |
189 | .fsync = noop_fsync, |
190 | }; |
191 | |
192 | const struct inode_operations simple_dir_inode_operations = { |
193 | .lookup = simple_lookup, |
194 | }; |
195 | |
196 | static const struct super_operations simple_super_operations = { |
197 | .statfs = simple_statfs, |
198 | }; |
199 | |
200 | /* |
201 | * Common helper for pseudo-filesystems (sockfs, pipefs, bdev - stuff that |
202 | * will never be mountable) |
203 | */ |
204 | int get_sb_pseudo(struct file_system_type *fs_type, char *name, |
205 | const struct super_operations *ops, unsigned long magic, |
206 | struct vfsmount *mnt) |
207 | { |
208 | struct super_block *s = sget(fs_type, NULL, set_anon_super, NULL); |
209 | struct dentry *dentry; |
210 | struct inode *root; |
211 | struct qstr d_name = {.name = name, .len = strlen(name)}; |
212 | |
213 | if (IS_ERR(s)) |
214 | return PTR_ERR(s); |
215 | |
216 | s->s_flags = MS_NOUSER; |
217 | s->s_maxbytes = MAX_LFS_FILESIZE; |
218 | s->s_blocksize = PAGE_SIZE; |
219 | s->s_blocksize_bits = PAGE_SHIFT; |
220 | s->s_magic = magic; |
221 | s->s_op = ops ? ops : &simple_super_operations; |
222 | s->s_time_gran = 1; |
223 | root = new_inode(s); |
224 | if (!root) |
225 | goto Enomem; |
226 | /* |
227 | * since this is the first inode, make it number 1. New inodes created |
228 | * after this must take care not to collide with it (by passing |
229 | * max_reserved of 1 to iunique). |
230 | */ |
231 | root->i_ino = 1; |
232 | root->i_mode = S_IFDIR | S_IRUSR | S_IWUSR; |
233 | root->i_atime = root->i_mtime = root->i_ctime = CURRENT_TIME; |
234 | dentry = d_alloc(NULL, &d_name); |
235 | if (!dentry) { |
236 | iput(root); |
237 | goto Enomem; |
238 | } |
239 | dentry->d_sb = s; |
240 | dentry->d_parent = dentry; |
241 | d_instantiate(dentry, root); |
242 | s->s_root = dentry; |
243 | s->s_flags |= MS_ACTIVE; |
244 | simple_set_mnt(mnt, s); |
245 | return 0; |
246 | |
247 | Enomem: |
248 | deactivate_locked_super(s); |
249 | return -ENOMEM; |
250 | } |
251 | |
252 | int simple_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry) |
253 | { |
254 | struct inode *inode = old_dentry->d_inode; |
255 | |
256 | inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME; |
257 | inc_nlink(inode); |
258 | atomic_inc(&inode->i_count); |
259 | dget(dentry); |
260 | d_instantiate(dentry, inode); |
261 | return 0; |
262 | } |
263 | |
264 | static inline int simple_positive(struct dentry *dentry) |
265 | { |
266 | return dentry->d_inode && !d_unhashed(dentry); |
267 | } |
268 | |
269 | int simple_empty(struct dentry *dentry) |
270 | { |
271 | struct dentry *child; |
272 | int ret = 0; |
273 | |
274 | spin_lock(&dcache_lock); |
275 | list_for_each_entry(child, &dentry->d_subdirs, d_u.d_child) |
276 | if (simple_positive(child)) |
277 | goto out; |
278 | ret = 1; |
279 | out: |
280 | spin_unlock(&dcache_lock); |
281 | return ret; |
282 | } |
283 | |
284 | int simple_unlink(struct inode *dir, struct dentry *dentry) |
285 | { |
286 | struct inode *inode = dentry->d_inode; |
287 | |
288 | inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME; |
289 | drop_nlink(inode); |
290 | dput(dentry); |
291 | return 0; |
292 | } |
293 | |
294 | int simple_rmdir(struct inode *dir, struct dentry *dentry) |
295 | { |
296 | if (!simple_empty(dentry)) |
297 | return -ENOTEMPTY; |
298 | |
299 | drop_nlink(dentry->d_inode); |
300 | simple_unlink(dir, dentry); |
301 | drop_nlink(dir); |
302 | return 0; |
303 | } |
304 | |
305 | int simple_rename(struct inode *old_dir, struct dentry *old_dentry, |
306 | struct inode *new_dir, struct dentry *new_dentry) |
307 | { |
308 | struct inode *inode = old_dentry->d_inode; |
309 | int they_are_dirs = S_ISDIR(old_dentry->d_inode->i_mode); |
310 | |
311 | if (!simple_empty(new_dentry)) |
312 | return -ENOTEMPTY; |
313 | |
314 | if (new_dentry->d_inode) { |
315 | simple_unlink(new_dir, new_dentry); |
316 | if (they_are_dirs) |
317 | drop_nlink(old_dir); |
318 | } else if (they_are_dirs) { |
319 | drop_nlink(old_dir); |
320 | inc_nlink(new_dir); |
321 | } |
322 | |
323 | old_dir->i_ctime = old_dir->i_mtime = new_dir->i_ctime = |
324 | new_dir->i_mtime = inode->i_ctime = CURRENT_TIME; |
325 | |
326 | return 0; |
327 | } |
328 | |
329 | /** |
330 | * simple_setsize - handle core mm and vfs requirements for file size change |
331 | * @inode: inode |
332 | * @newsize: new file size |
333 | * |
334 | * Returns 0 on success, -error on failure. |
335 | * |
336 | * simple_setsize must be called with inode_mutex held. |
337 | * |
338 | * simple_setsize will check that the requested new size is OK (see |
339 | * inode_newsize_ok), and then will perform the necessary i_size update |
340 | * and pagecache truncation (if necessary). It will be typically be called |
341 | * from the filesystem's setattr function when ATTR_SIZE is passed in. |
342 | * |
343 | * The inode itself must have correct permissions and attributes to allow |
344 | * i_size to be changed, this function then just checks that the new size |
345 | * requested is valid. |
346 | * |
347 | * In the case of simple in-memory filesystems with inodes stored solely |
348 | * in the inode cache, and file data in the pagecache, nothing more needs |
349 | * to be done to satisfy a truncate request. Filesystems with on-disk |
350 | * blocks for example will need to free them in the case of truncate, in |
351 | * that case it may be easier not to use simple_setsize (but each of its |
352 | * components will likely be required at some point to update pagecache |
353 | * and inode etc). |
354 | */ |
355 | int simple_setsize(struct inode *inode, loff_t newsize) |
356 | { |
357 | loff_t oldsize; |
358 | int error; |
359 | |
360 | error = inode_newsize_ok(inode, newsize); |
361 | if (error) |
362 | return error; |
363 | |
364 | oldsize = inode->i_size; |
365 | i_size_write(inode, newsize); |
366 | truncate_pagecache(inode, oldsize, newsize); |
367 | |
368 | return error; |
369 | } |
370 | EXPORT_SYMBOL(simple_setsize); |
371 | |
372 | /** |
373 | * simple_setattr - setattr for simple in-memory filesystem |
374 | * @dentry: dentry |
375 | * @iattr: iattr structure |
376 | * |
377 | * Returns 0 on success, -error on failure. |
378 | * |
379 | * simple_setattr implements setattr for an in-memory filesystem which |
380 | * does not store its own file data or metadata (eg. uses the page cache |
381 | * and inode cache as its data store). |
382 | */ |
383 | int simple_setattr(struct dentry *dentry, struct iattr *iattr) |
384 | { |
385 | struct inode *inode = dentry->d_inode; |
386 | int error; |
387 | |
388 | error = inode_change_ok(inode, iattr); |
389 | if (error) |
390 | return error; |
391 | |
392 | if (iattr->ia_valid & ATTR_SIZE) { |
393 | error = simple_setsize(inode, iattr->ia_size); |
394 | if (error) |
395 | return error; |
396 | } |
397 | |
398 | generic_setattr(inode, iattr); |
399 | |
400 | return error; |
401 | } |
402 | EXPORT_SYMBOL(simple_setattr); |
403 | |
404 | int simple_readpage(struct file *file, struct page *page) |
405 | { |
406 | clear_highpage(page); |
407 | flush_dcache_page(page); |
408 | SetPageUptodate(page); |
409 | unlock_page(page); |
410 | return 0; |
411 | } |
412 | |
413 | int simple_write_begin(struct file *file, struct address_space *mapping, |
414 | loff_t pos, unsigned len, unsigned flags, |
415 | struct page **pagep, void **fsdata) |
416 | { |
417 | struct page *page; |
418 | pgoff_t index; |
419 | |
420 | index = pos >> PAGE_CACHE_SHIFT; |
421 | |
422 | page = grab_cache_page_write_begin(mapping, index, flags); |
423 | if (!page) |
424 | return -ENOMEM; |
425 | |
426 | *pagep = page; |
427 | |
428 | if (!PageUptodate(page) && (len != PAGE_CACHE_SIZE)) { |
429 | unsigned from = pos & (PAGE_CACHE_SIZE - 1); |
430 | |
431 | zero_user_segments(page, 0, from, from + len, PAGE_CACHE_SIZE); |
432 | } |
433 | return 0; |
434 | } |
435 | |
436 | /** |
437 | * simple_write_end - .write_end helper for non-block-device FSes |
438 | * @available: See .write_end of address_space_operations |
439 | * @file: " |
440 | * @mapping: " |
441 | * @pos: " |
442 | * @len: " |
443 | * @copied: " |
444 | * @page: " |
445 | * @fsdata: " |
446 | * |
447 | * simple_write_end does the minimum needed for updating a page after writing is |
448 | * done. It has the same API signature as the .write_end of |
449 | * address_space_operations vector. So it can just be set onto .write_end for |
450 | * FSes that don't need any other processing. i_mutex is assumed to be held. |
451 | * Block based filesystems should use generic_write_end(). |
452 | * NOTE: Even though i_size might get updated by this function, mark_inode_dirty |
453 | * is not called, so a filesystem that actually does store data in .write_inode |
454 | * should extend on what's done here with a call to mark_inode_dirty() in the |
455 | * case that i_size has changed. |
456 | */ |
457 | int simple_write_end(struct file *file, struct address_space *mapping, |
458 | loff_t pos, unsigned len, unsigned copied, |
459 | struct page *page, void *fsdata) |
460 | { |
461 | struct inode *inode = page->mapping->host; |
462 | loff_t last_pos = pos + copied; |
463 | |
464 | /* zero the stale part of the page if we did a short copy */ |
465 | if (copied < len) { |
466 | unsigned from = pos & (PAGE_CACHE_SIZE - 1); |
467 | |
468 | zero_user(page, from + copied, len - copied); |
469 | } |
470 | |
471 | if (!PageUptodate(page)) |
472 | SetPageUptodate(page); |
473 | /* |
474 | * No need to use i_size_read() here, the i_size |
475 | * cannot change under us because we hold the i_mutex. |
476 | */ |
477 | if (last_pos > inode->i_size) |
478 | i_size_write(inode, last_pos); |
479 | |
480 | set_page_dirty(page); |
481 | unlock_page(page); |
482 | page_cache_release(page); |
483 | |
484 | return copied; |
485 | } |
486 | |
487 | /* |
488 | * the inodes created here are not hashed. If you use iunique to generate |
489 | * unique inode values later for this filesystem, then you must take care |
490 | * to pass it an appropriate max_reserved value to avoid collisions. |
491 | */ |
492 | int simple_fill_super(struct super_block *s, unsigned long magic, |
493 | struct tree_descr *files) |
494 | { |
495 | struct inode *inode; |
496 | struct dentry *root; |
497 | struct dentry *dentry; |
498 | int i; |
499 | |
500 | s->s_blocksize = PAGE_CACHE_SIZE; |
501 | s->s_blocksize_bits = PAGE_CACHE_SHIFT; |
502 | s->s_magic = magic; |
503 | s->s_op = &simple_super_operations; |
504 | s->s_time_gran = 1; |
505 | |
506 | inode = new_inode(s); |
507 | if (!inode) |
508 | return -ENOMEM; |
509 | /* |
510 | * because the root inode is 1, the files array must not contain an |
511 | * entry at index 1 |
512 | */ |
513 | inode->i_ino = 1; |
514 | inode->i_mode = S_IFDIR | 0755; |
515 | inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME; |
516 | inode->i_op = &simple_dir_inode_operations; |
517 | inode->i_fop = &simple_dir_operations; |
518 | inode->i_nlink = 2; |
519 | root = d_alloc_root(inode); |
520 | if (!root) { |
521 | iput(inode); |
522 | return -ENOMEM; |
523 | } |
524 | for (i = 0; !files->name || files->name[0]; i++, files++) { |
525 | if (!files->name) |
526 | continue; |
527 | |
528 | /* warn if it tries to conflict with the root inode */ |
529 | if (unlikely(i == 1)) |
530 | printk(KERN_WARNING "%s: %s passed in a files array" |
531 | "with an index of 1!\n", __func__, |
532 | s->s_type->name); |
533 | |
534 | dentry = d_alloc_name(root, files->name); |
535 | if (!dentry) |
536 | goto out; |
537 | inode = new_inode(s); |
538 | if (!inode) |
539 | goto out; |
540 | inode->i_mode = S_IFREG | files->mode; |
541 | inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME; |
542 | inode->i_fop = files->ops; |
543 | inode->i_ino = i; |
544 | d_add(dentry, inode); |
545 | } |
546 | s->s_root = root; |
547 | return 0; |
548 | out: |
549 | d_genocide(root); |
550 | dput(root); |
551 | return -ENOMEM; |
552 | } |
553 | |
554 | static DEFINE_SPINLOCK(pin_fs_lock); |
555 | |
556 | int simple_pin_fs(struct file_system_type *type, struct vfsmount **mount, int *count) |
557 | { |
558 | struct vfsmount *mnt = NULL; |
559 | spin_lock(&pin_fs_lock); |
560 | if (unlikely(!*mount)) { |
561 | spin_unlock(&pin_fs_lock); |
562 | mnt = vfs_kern_mount(type, 0, type->name, NULL); |
563 | if (IS_ERR(mnt)) |
564 | return PTR_ERR(mnt); |
565 | spin_lock(&pin_fs_lock); |
566 | if (!*mount) |
567 | *mount = mnt; |
568 | } |
569 | mntget(*mount); |
570 | ++*count; |
571 | spin_unlock(&pin_fs_lock); |
572 | mntput(mnt); |
573 | return 0; |
574 | } |
575 | |
576 | void simple_release_fs(struct vfsmount **mount, int *count) |
577 | { |
578 | struct vfsmount *mnt; |
579 | spin_lock(&pin_fs_lock); |
580 | mnt = *mount; |
581 | if (!--*count) |
582 | *mount = NULL; |
583 | spin_unlock(&pin_fs_lock); |
584 | mntput(mnt); |
585 | } |
586 | |
587 | /** |
588 | * simple_read_from_buffer - copy data from the buffer to user space |
589 | * @to: the user space buffer to read to |
590 | * @count: the maximum number of bytes to read |
591 | * @ppos: the current position in the buffer |
592 | * @from: the buffer to read from |
593 | * @available: the size of the buffer |
594 | * |
595 | * The simple_read_from_buffer() function reads up to @count bytes from the |
596 | * buffer @from at offset @ppos into the user space address starting at @to. |
597 | * |
598 | * On success, the number of bytes read is returned and the offset @ppos is |
599 | * advanced by this number, or negative value is returned on error. |
600 | **/ |
601 | ssize_t simple_read_from_buffer(void __user *to, size_t count, loff_t *ppos, |
602 | const void *from, size_t available) |
603 | { |
604 | loff_t pos = *ppos; |
605 | size_t ret; |
606 | |
607 | if (pos < 0) |
608 | return -EINVAL; |
609 | if (pos >= available || !count) |
610 | return 0; |
611 | if (count > available - pos) |
612 | count = available - pos; |
613 | ret = copy_to_user(to, from + pos, count); |
614 | if (ret == count) |
615 | return -EFAULT; |
616 | count -= ret; |
617 | *ppos = pos + count; |
618 | return count; |
619 | } |
620 | |
621 | /** |
622 | * simple_write_to_buffer - copy data from user space to the buffer |
623 | * @to: the buffer to write to |
624 | * @available: the size of the buffer |
625 | * @ppos: the current position in the buffer |
626 | * @from: the user space buffer to read from |
627 | * @count: the maximum number of bytes to read |
628 | * |
629 | * The simple_write_to_buffer() function reads up to @count bytes from the user |
630 | * space address starting at @from into the buffer @to at offset @ppos. |
631 | * |
632 | * On success, the number of bytes written is returned and the offset @ppos is |
633 | * advanced by this number, or negative value is returned on error. |
634 | **/ |
635 | ssize_t simple_write_to_buffer(void *to, size_t available, loff_t *ppos, |
636 | const void __user *from, size_t count) |
637 | { |
638 | loff_t pos = *ppos; |
639 | size_t res; |
640 | |
641 | if (pos < 0) |
642 | return -EINVAL; |
643 | if (pos >= available || !count) |
644 | return 0; |
645 | if (count > available - pos) |
646 | count = available - pos; |
647 | res = copy_from_user(to + pos, from, count); |
648 | if (res == count) |
649 | return -EFAULT; |
650 | count -= res; |
651 | *ppos = pos + count; |
652 | return count; |
653 | } |
654 | |
655 | /** |
656 | * memory_read_from_buffer - copy data from the buffer |
657 | * @to: the kernel space buffer to read to |
658 | * @count: the maximum number of bytes to read |
659 | * @ppos: the current position in the buffer |
660 | * @from: the buffer to read from |
661 | * @available: the size of the buffer |
662 | * |
663 | * The memory_read_from_buffer() function reads up to @count bytes from the |
664 | * buffer @from at offset @ppos into the kernel space address starting at @to. |
665 | * |
666 | * On success, the number of bytes read is returned and the offset @ppos is |
667 | * advanced by this number, or negative value is returned on error. |
668 | **/ |
669 | ssize_t memory_read_from_buffer(void *to, size_t count, loff_t *ppos, |
670 | const void *from, size_t available) |
671 | { |
672 | loff_t pos = *ppos; |
673 | |
674 | if (pos < 0) |
675 | return -EINVAL; |
676 | if (pos >= available) |
677 | return 0; |
678 | if (count > available - pos) |
679 | count = available - pos; |
680 | memcpy(to, from + pos, count); |
681 | *ppos = pos + count; |
682 | |
683 | return count; |
684 | } |
685 | |
686 | /* |
687 | * Transaction based IO. |
688 | * The file expects a single write which triggers the transaction, and then |
689 | * possibly a read which collects the result - which is stored in a |
690 | * file-local buffer. |
691 | */ |
692 | |
693 | void simple_transaction_set(struct file *file, size_t n) |
694 | { |
695 | struct simple_transaction_argresp *ar = file->private_data; |
696 | |
697 | BUG_ON(n > SIMPLE_TRANSACTION_LIMIT); |
698 | |
699 | /* |
700 | * The barrier ensures that ar->size will really remain zero until |
701 | * ar->data is ready for reading. |
702 | */ |
703 | smp_mb(); |
704 | ar->size = n; |
705 | } |
706 | |
707 | char *simple_transaction_get(struct file *file, const char __user *buf, size_t size) |
708 | { |
709 | struct simple_transaction_argresp *ar; |
710 | static DEFINE_SPINLOCK(simple_transaction_lock); |
711 | |
712 | if (size > SIMPLE_TRANSACTION_LIMIT - 1) |
713 | return ERR_PTR(-EFBIG); |
714 | |
715 | ar = (struct simple_transaction_argresp *)get_zeroed_page(GFP_KERNEL); |
716 | if (!ar) |
717 | return ERR_PTR(-ENOMEM); |
718 | |
719 | spin_lock(&simple_transaction_lock); |
720 | |
721 | /* only one write allowed per open */ |
722 | if (file->private_data) { |
723 | spin_unlock(&simple_transaction_lock); |
724 | free_page((unsigned long)ar); |
725 | return ERR_PTR(-EBUSY); |
726 | } |
727 | |
728 | file->private_data = ar; |
729 | |
730 | spin_unlock(&simple_transaction_lock); |
731 | |
732 | if (copy_from_user(ar->data, buf, size)) |
733 | return ERR_PTR(-EFAULT); |
734 | |
735 | return ar->data; |
736 | } |
737 | |
738 | ssize_t simple_transaction_read(struct file *file, char __user *buf, size_t size, loff_t *pos) |
739 | { |
740 | struct simple_transaction_argresp *ar = file->private_data; |
741 | |
742 | if (!ar) |
743 | return 0; |
744 | return simple_read_from_buffer(buf, size, pos, ar->data, ar->size); |
745 | } |
746 | |
747 | int simple_transaction_release(struct inode *inode, struct file *file) |
748 | { |
749 | free_page((unsigned long)file->private_data); |
750 | return 0; |
751 | } |
752 | |
753 | /* Simple attribute files */ |
754 | |
755 | struct simple_attr { |
756 | int (*get)(void *, u64 *); |
757 | int (*set)(void *, u64); |
758 | char get_buf[24]; /* enough to store a u64 and "\n\0" */ |
759 | char set_buf[24]; |
760 | void *data; |
761 | const char *fmt; /* format for read operation */ |
762 | struct mutex mutex; /* protects access to these buffers */ |
763 | }; |
764 | |
765 | /* simple_attr_open is called by an actual attribute open file operation |
766 | * to set the attribute specific access operations. */ |
767 | int simple_attr_open(struct inode *inode, struct file *file, |
768 | int (*get)(void *, u64 *), int (*set)(void *, u64), |
769 | const char *fmt) |
770 | { |
771 | struct simple_attr *attr; |
772 | |
773 | attr = kmalloc(sizeof(*attr), GFP_KERNEL); |
774 | if (!attr) |
775 | return -ENOMEM; |
776 | |
777 | attr->get = get; |
778 | attr->set = set; |
779 | attr->data = inode->i_private; |
780 | attr->fmt = fmt; |
781 | mutex_init(&attr->mutex); |
782 | |
783 | file->private_data = attr; |
784 | |
785 | return nonseekable_open(inode, file); |
786 | } |
787 | |
788 | int simple_attr_release(struct inode *inode, struct file *file) |
789 | { |
790 | kfree(file->private_data); |
791 | return 0; |
792 | } |
793 | |
794 | /* read from the buffer that is filled with the get function */ |
795 | ssize_t simple_attr_read(struct file *file, char __user *buf, |
796 | size_t len, loff_t *ppos) |
797 | { |
798 | struct simple_attr *attr; |
799 | size_t size; |
800 | ssize_t ret; |
801 | |
802 | attr = file->private_data; |
803 | |
804 | if (!attr->get) |
805 | return -EACCES; |
806 | |
807 | ret = mutex_lock_interruptible(&attr->mutex); |
808 | if (ret) |
809 | return ret; |
810 | |
811 | if (*ppos) { /* continued read */ |
812 | size = strlen(attr->get_buf); |
813 | } else { /* first read */ |
814 | u64 val; |
815 | ret = attr->get(attr->data, &val); |
816 | if (ret) |
817 | goto out; |
818 | |
819 | size = scnprintf(attr->get_buf, sizeof(attr->get_buf), |
820 | attr->fmt, (unsigned long long)val); |
821 | } |
822 | |
823 | ret = simple_read_from_buffer(buf, len, ppos, attr->get_buf, size); |
824 | out: |
825 | mutex_unlock(&attr->mutex); |
826 | return ret; |
827 | } |
828 | |
829 | /* interpret the buffer as a number to call the set function with */ |
830 | ssize_t simple_attr_write(struct file *file, const char __user *buf, |
831 | size_t len, loff_t *ppos) |
832 | { |
833 | struct simple_attr *attr; |
834 | u64 val; |
835 | size_t size; |
836 | ssize_t ret; |
837 | |
838 | attr = file->private_data; |
839 | if (!attr->set) |
840 | return -EACCES; |
841 | |
842 | ret = mutex_lock_interruptible(&attr->mutex); |
843 | if (ret) |
844 | return ret; |
845 | |
846 | ret = -EFAULT; |
847 | size = min(sizeof(attr->set_buf) - 1, len); |
848 | if (copy_from_user(attr->set_buf, buf, size)) |
849 | goto out; |
850 | |
851 | attr->set_buf[size] = '\0'; |
852 | val = simple_strtol(attr->set_buf, NULL, 0); |
853 | ret = attr->set(attr->data, val); |
854 | if (ret == 0) |
855 | ret = len; /* on success, claim we got the whole input */ |
856 | out: |
857 | mutex_unlock(&attr->mutex); |
858 | return ret; |
859 | } |
860 | |
861 | /** |
862 | * generic_fh_to_dentry - generic helper for the fh_to_dentry export operation |
863 | * @sb: filesystem to do the file handle conversion on |
864 | * @fid: file handle to convert |
865 | * @fh_len: length of the file handle in bytes |
866 | * @fh_type: type of file handle |
867 | * @get_inode: filesystem callback to retrieve inode |
868 | * |
869 | * This function decodes @fid as long as it has one of the well-known |
870 | * Linux filehandle types and calls @get_inode on it to retrieve the |
871 | * inode for the object specified in the file handle. |
872 | */ |
873 | struct dentry *generic_fh_to_dentry(struct super_block *sb, struct fid *fid, |
874 | int fh_len, int fh_type, struct inode *(*get_inode) |
875 | (struct super_block *sb, u64 ino, u32 gen)) |
876 | { |
877 | struct inode *inode = NULL; |
878 | |
879 | if (fh_len < 2) |
880 | return NULL; |
881 | |
882 | switch (fh_type) { |
883 | case FILEID_INO32_GEN: |
884 | case FILEID_INO32_GEN_PARENT: |
885 | inode = get_inode(sb, fid->i32.ino, fid->i32.gen); |
886 | break; |
887 | } |
888 | |
889 | return d_obtain_alias(inode); |
890 | } |
891 | EXPORT_SYMBOL_GPL(generic_fh_to_dentry); |
892 | |
893 | /** |
894 | * generic_fh_to_dentry - generic helper for the fh_to_parent export operation |
895 | * @sb: filesystem to do the file handle conversion on |
896 | * @fid: file handle to convert |
897 | * @fh_len: length of the file handle in bytes |
898 | * @fh_type: type of file handle |
899 | * @get_inode: filesystem callback to retrieve inode |
900 | * |
901 | * This function decodes @fid as long as it has one of the well-known |
902 | * Linux filehandle types and calls @get_inode on it to retrieve the |
903 | * inode for the _parent_ object specified in the file handle if it |
904 | * is specified in the file handle, or NULL otherwise. |
905 | */ |
906 | struct dentry *generic_fh_to_parent(struct super_block *sb, struct fid *fid, |
907 | int fh_len, int fh_type, struct inode *(*get_inode) |
908 | (struct super_block *sb, u64 ino, u32 gen)) |
909 | { |
910 | struct inode *inode = NULL; |
911 | |
912 | if (fh_len <= 2) |
913 | return NULL; |
914 | |
915 | switch (fh_type) { |
916 | case FILEID_INO32_GEN_PARENT: |
917 | inode = get_inode(sb, fid->i32.parent_ino, |
918 | (fh_len > 3 ? fid->i32.parent_gen : 0)); |
919 | break; |
920 | } |
921 | |
922 | return d_obtain_alias(inode); |
923 | } |
924 | EXPORT_SYMBOL_GPL(generic_fh_to_parent); |
925 | |
926 | /** |
927 | * generic_file_fsync - generic fsync implementation for simple filesystems |
928 | * @file: file to synchronize |
929 | * @datasync: only synchronize essential metadata if true |
930 | * |
931 | * This is a generic implementation of the fsync method for simple |
932 | * filesystems which track all non-inode metadata in the buffers list |
933 | * hanging off the address_space structure. |
934 | */ |
935 | int generic_file_fsync(struct file *file, int datasync) |
936 | { |
937 | struct writeback_control wbc = { |
938 | .sync_mode = WB_SYNC_ALL, |
939 | .nr_to_write = 0, /* metadata-only; caller takes care of data */ |
940 | }; |
941 | struct inode *inode = file->f_mapping->host; |
942 | int err; |
943 | int ret; |
944 | |
945 | ret = sync_mapping_buffers(inode->i_mapping); |
946 | if (!(inode->i_state & I_DIRTY)) |
947 | return ret; |
948 | if (datasync && !(inode->i_state & I_DIRTY_DATASYNC)) |
949 | return ret; |
950 | |
951 | err = sync_inode(inode, &wbc); |
952 | if (ret == 0) |
953 | ret = err; |
954 | return ret; |
955 | } |
956 | EXPORT_SYMBOL(generic_file_fsync); |
957 | |
958 | /* |
959 | * No-op implementation of ->fsync for in-memory filesystems. |
960 | */ |
961 | int noop_fsync(struct file *file, int datasync) |
962 | { |
963 | return 0; |
964 | } |
965 | |
966 | EXPORT_SYMBOL(dcache_dir_close); |
967 | EXPORT_SYMBOL(dcache_dir_lseek); |
968 | EXPORT_SYMBOL(dcache_dir_open); |
969 | EXPORT_SYMBOL(dcache_readdir); |
970 | EXPORT_SYMBOL(generic_read_dir); |
971 | EXPORT_SYMBOL(get_sb_pseudo); |
972 | EXPORT_SYMBOL(simple_write_begin); |
973 | EXPORT_SYMBOL(simple_write_end); |
974 | EXPORT_SYMBOL(simple_dir_inode_operations); |
975 | EXPORT_SYMBOL(simple_dir_operations); |
976 | EXPORT_SYMBOL(simple_empty); |
977 | EXPORT_SYMBOL(simple_fill_super); |
978 | EXPORT_SYMBOL(simple_getattr); |
979 | EXPORT_SYMBOL(simple_link); |
980 | EXPORT_SYMBOL(simple_lookup); |
981 | EXPORT_SYMBOL(simple_pin_fs); |
982 | EXPORT_SYMBOL(simple_readpage); |
983 | EXPORT_SYMBOL(simple_release_fs); |
984 | EXPORT_SYMBOL(simple_rename); |
985 | EXPORT_SYMBOL(simple_rmdir); |
986 | EXPORT_SYMBOL(simple_statfs); |
987 | EXPORT_SYMBOL(noop_fsync); |
988 | EXPORT_SYMBOL(simple_unlink); |
989 | EXPORT_SYMBOL(simple_read_from_buffer); |
990 | EXPORT_SYMBOL(simple_write_to_buffer); |
991 | EXPORT_SYMBOL(memory_read_from_buffer); |
992 | EXPORT_SYMBOL(simple_transaction_set); |
993 | EXPORT_SYMBOL(simple_transaction_get); |
994 | EXPORT_SYMBOL(simple_transaction_read); |
995 | EXPORT_SYMBOL(simple_transaction_release); |
996 | EXPORT_SYMBOL_GPL(simple_attr_open); |
997 | EXPORT_SYMBOL_GPL(simple_attr_release); |
998 | EXPORT_SYMBOL_GPL(simple_attr_read); |
999 | EXPORT_SYMBOL_GPL(simple_attr_write); |
1000 |
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