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TOMOYO Linux Cross Reference
Linux/fs/libfs.c

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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/mount.h>
  9 #include <linux/vfs.h>
 10 #include <linux/mutex.h>
 11 #include <linux/exportfs.h>
 12 #include <linux/writeback.h>
 13 #include <linux/buffer_head.h>
 14 
 15 #include <asm/uaccess.h>
 16 
 17 int simple_getattr(struct vfsmount *mnt, struct dentry *dentry,
 18                    struct kstat *stat)
 19 {
 20         struct inode *inode = dentry->d_inode;
 21         generic_fillattr(inode, stat);
 22         stat->blocks = inode->i_mapping->nrpages << (PAGE_CACHE_SHIFT - 9);
 23         return 0;
 24 }
 25 
 26 int simple_statfs(struct dentry *dentry, struct kstatfs *buf)
 27 {
 28         buf->f_type = dentry->d_sb->s_magic;
 29         buf->f_bsize = PAGE_CACHE_SIZE;
 30         buf->f_namelen = NAME_MAX;
 31         return 0;
 32 }
 33 
 34 /*
 35  * Retaining negative dentries for an in-memory filesystem just wastes
 36  * memory and lookup time: arrange for them to be deleted immediately.
 37  */
 38 static int simple_delete_dentry(struct dentry *dentry)
 39 {
 40         return 1;
 41 }
 42 
 43 /*
 44  * Lookup the data. This is trivial - if the dentry didn't already
 45  * exist, we know it is negative.  Set d_op to delete negative dentries.
 46  */
 47 struct dentry *simple_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
 48 {
 49         static const struct dentry_operations simple_dentry_operations = {
 50                 .d_delete = simple_delete_dentry,
 51         };
 52 
 53         if (dentry->d_name.len > NAME_MAX)
 54                 return ERR_PTR(-ENAMETOOLONG);
 55         dentry->d_op = &simple_dentry_operations;
 56         d_add(dentry, NULL);
 57         return NULL;
 58 }
 59 
 60 int simple_sync_file(struct file * file, struct dentry *dentry, int datasync)
 61 {
 62         return 0;
 63 }
 64  
 65 int dcache_dir_open(struct inode *inode, struct file *file)
 66 {
 67         static struct qstr cursor_name = {.len = 1, .name = "."};
 68 
 69         file->private_data = d_alloc(file->f_path.dentry, &cursor_name);
 70 
 71         return file->private_data ? 0 : -ENOMEM;
 72 }
 73 
 74 int dcache_dir_close(struct inode *inode, struct file *file)
 75 {
 76         dput(file->private_data);
 77         return 0;
 78 }
 79 
 80 loff_t dcache_dir_lseek(struct file *file, loff_t offset, int origin)
 81 {
 82         mutex_lock(&file->f_path.dentry->d_inode->i_mutex);
 83         switch (origin) {
 84                 case 1:
 85                         offset += file->f_pos;
 86                 case 0:
 87                         if (offset >= 0)
 88                                 break;
 89                 default:
 90                         mutex_unlock(&file->f_path.dentry->d_inode->i_mutex);
 91                         return -EINVAL;
 92         }
 93         if (offset != file->f_pos) {
 94                 file->f_pos = offset;
 95                 if (file->f_pos >= 2) {
 96                         struct list_head *p;
 97                         struct dentry *cursor = file->private_data;
 98                         loff_t n = file->f_pos - 2;
 99 
100                         spin_lock(&dcache_lock);
101                         list_del(&cursor->d_u.d_child);
102                         p = file->f_path.dentry->d_subdirs.next;
103                         while (n && p != &file->f_path.dentry->d_subdirs) {
104                                 struct dentry *next;
105                                 next = list_entry(p, struct dentry, d_u.d_child);
106                                 if (!d_unhashed(next) && next->d_inode)
107                                         n--;
108                                 p = p->next;
109                         }
110                         list_add_tail(&cursor->d_u.d_child, p);
111                         spin_unlock(&dcache_lock);
112                 }
113         }
114         mutex_unlock(&file->f_path.dentry->d_inode->i_mutex);
115         return offset;
116 }
117 
118 /* Relationship between i_mode and the DT_xxx types */
119 static inline unsigned char dt_type(struct inode *inode)
120 {
121         return (inode->i_mode >> 12) & 15;
122 }
123 
124 /*
125  * Directory is locked and all positive dentries in it are safe, since
126  * for ramfs-type trees they can't go away without unlink() or rmdir(),
127  * both impossible due to the lock on directory.
128  */
129 
130 int dcache_readdir(struct file * filp, void * dirent, filldir_t filldir)
131 {
132         struct dentry *dentry = filp->f_path.dentry;
133         struct dentry *cursor = filp->private_data;
134         struct list_head *p, *q = &cursor->d_u.d_child;
135         ino_t ino;
136         int i = filp->f_pos;
137 
138         switch (i) {
139                 case 0:
140                         ino = dentry->d_inode->i_ino;
141                         if (filldir(dirent, ".", 1, i, ino, DT_DIR) < 0)
142                                 break;
143                         filp->f_pos++;
144                         i++;
145                         /* fallthrough */
146                 case 1:
147                         ino = parent_ino(dentry);
148                         if (filldir(dirent, "..", 2, i, ino, DT_DIR) < 0)
149                                 break;
150                         filp->f_pos++;
151                         i++;
152                         /* fallthrough */
153                 default:
154                         spin_lock(&dcache_lock);
155                         if (filp->f_pos == 2)
156                                 list_move(q, &dentry->d_subdirs);
157 
158                         for (p=q->next; p != &dentry->d_subdirs; p=p->next) {
159                                 struct dentry *next;
160                                 next = list_entry(p, struct dentry, d_u.d_child);
161                                 if (d_unhashed(next) || !next->d_inode)
162                                         continue;
163 
164                                 spin_unlock(&dcache_lock);
165                                 if (filldir(dirent, next->d_name.name, 
166                                             next->d_name.len, filp->f_pos, 
167                                             next->d_inode->i_ino, 
168                                             dt_type(next->d_inode)) < 0)
169                                         return 0;
170                                 spin_lock(&dcache_lock);
171                                 /* next is still alive */
172                                 list_move(q, p);
173                                 p = q;
174                                 filp->f_pos++;
175                         }
176                         spin_unlock(&dcache_lock);
177         }
178         return 0;
179 }
180 
181 ssize_t generic_read_dir(struct file *filp, char __user *buf, size_t siz, loff_t *ppos)
182 {
183         return -EISDIR;
184 }
185 
186 const struct file_operations simple_dir_operations = {
187         .open           = dcache_dir_open,
188         .release        = dcache_dir_close,
189         .llseek         = dcache_dir_lseek,
190         .read           = generic_read_dir,
191         .readdir        = dcache_readdir,
192         .fsync          = simple_sync_file,
193 };
194 
195 const struct inode_operations simple_dir_inode_operations = {
196         .lookup         = simple_lookup,
197 };
198 
199 static const struct super_operations simple_super_operations = {
200         .statfs         = simple_statfs,
201 };
202 
203 /*
204  * Common helper for pseudo-filesystems (sockfs, pipefs, bdev - stuff that
205  * will never be mountable)
206  */
207 int get_sb_pseudo(struct file_system_type *fs_type, char *name,
208         const struct super_operations *ops, unsigned long magic,
209         struct vfsmount *mnt)
210 {
211         struct super_block *s = sget(fs_type, NULL, set_anon_super, NULL);
212         struct dentry *dentry;
213         struct inode *root;
214         struct qstr d_name = {.name = name, .len = strlen(name)};
215 
216         if (IS_ERR(s))
217                 return PTR_ERR(s);
218 
219         s->s_flags = MS_NOUSER;
220         s->s_maxbytes = MAX_LFS_FILESIZE;
221         s->s_blocksize = PAGE_SIZE;
222         s->s_blocksize_bits = PAGE_SHIFT;
223         s->s_magic = magic;
224         s->s_op = ops ? ops : &simple_super_operations;
225         s->s_time_gran = 1;
226         root = new_inode(s);
227         if (!root)
228                 goto Enomem;
229         /*
230          * since this is the first inode, make it number 1. New inodes created
231          * after this must take care not to collide with it (by passing
232          * max_reserved of 1 to iunique).
233          */
234         root->i_ino = 1;
235         root->i_mode = S_IFDIR | S_IRUSR | S_IWUSR;
236         root->i_atime = root->i_mtime = root->i_ctime = CURRENT_TIME;
237         dentry = d_alloc(NULL, &d_name);
238         if (!dentry) {
239                 iput(root);
240                 goto Enomem;
241         }
242         dentry->d_sb = s;
243         dentry->d_parent = dentry;
244         d_instantiate(dentry, root);
245         s->s_root = dentry;
246         s->s_flags |= MS_ACTIVE;
247         simple_set_mnt(mnt, s);
248         return 0;
249 
250 Enomem:
251         deactivate_locked_super(s);
252         return -ENOMEM;
253 }
254 
255 int simple_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
256 {
257         struct inode *inode = old_dentry->d_inode;
258 
259         inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
260         inc_nlink(inode);
261         atomic_inc(&inode->i_count);
262         dget(dentry);
263         d_instantiate(dentry, inode);
264         return 0;
265 }
266 
267 static inline int simple_positive(struct dentry *dentry)
268 {
269         return dentry->d_inode && !d_unhashed(dentry);
270 }
271 
272 int simple_empty(struct dentry *dentry)
273 {
274         struct dentry *child;
275         int ret = 0;
276 
277         spin_lock(&dcache_lock);
278         list_for_each_entry(child, &dentry->d_subdirs, d_u.d_child)
279                 if (simple_positive(child))
280                         goto out;
281         ret = 1;
282 out:
283         spin_unlock(&dcache_lock);
284         return ret;
285 }
286 
287 int simple_unlink(struct inode *dir, struct dentry *dentry)
288 {
289         struct inode *inode = dentry->d_inode;
290 
291         inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
292         drop_nlink(inode);
293         dput(dentry);
294         return 0;
295 }
296 
297 int simple_rmdir(struct inode *dir, struct dentry *dentry)
298 {
299         if (!simple_empty(dentry))
300                 return -ENOTEMPTY;
301 
302         drop_nlink(dentry->d_inode);
303         simple_unlink(dir, dentry);
304         drop_nlink(dir);
305         return 0;
306 }
307 
308 int simple_rename(struct inode *old_dir, struct dentry *old_dentry,
309                 struct inode *new_dir, struct dentry *new_dentry)
310 {
311         struct inode *inode = old_dentry->d_inode;
312         int they_are_dirs = S_ISDIR(old_dentry->d_inode->i_mode);
313 
314         if (!simple_empty(new_dentry))
315                 return -ENOTEMPTY;
316 
317         if (new_dentry->d_inode) {
318                 simple_unlink(new_dir, new_dentry);
319                 if (they_are_dirs)
320                         drop_nlink(old_dir);
321         } else if (they_are_dirs) {
322                 drop_nlink(old_dir);
323                 inc_nlink(new_dir);
324         }
325 
326         old_dir->i_ctime = old_dir->i_mtime = new_dir->i_ctime =
327                 new_dir->i_mtime = inode->i_ctime = CURRENT_TIME;
328 
329         return 0;
330 }
331 
332 int simple_readpage(struct file *file, struct page *page)
333 {
334         clear_highpage(page);
335         flush_dcache_page(page);
336         SetPageUptodate(page);
337         unlock_page(page);
338         return 0;
339 }
340 
341 int simple_prepare_write(struct file *file, struct page *page,
342                         unsigned from, unsigned to)
343 {
344         if (!PageUptodate(page)) {
345                 if (to - from != PAGE_CACHE_SIZE)
346                         zero_user_segments(page,
347                                 0, from,
348                                 to, PAGE_CACHE_SIZE);
349         }
350         return 0;
351 }
352 
353 int simple_write_begin(struct file *file, struct address_space *mapping,
354                         loff_t pos, unsigned len, unsigned flags,
355                         struct page **pagep, void **fsdata)
356 {
357         struct page *page;
358         pgoff_t index;
359         unsigned from;
360 
361         index = pos >> PAGE_CACHE_SHIFT;
362         from = pos & (PAGE_CACHE_SIZE - 1);
363 
364         page = grab_cache_page_write_begin(mapping, index, flags);
365         if (!page)
366                 return -ENOMEM;
367 
368         *pagep = page;
369 
370         return simple_prepare_write(file, page, from, from+len);
371 }
372 
373 static int simple_commit_write(struct file *file, struct page *page,
374                                unsigned from, unsigned to)
375 {
376         struct inode *inode = page->mapping->host;
377         loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to;
378 
379         if (!PageUptodate(page))
380                 SetPageUptodate(page);
381         /*
382          * No need to use i_size_read() here, the i_size
383          * cannot change under us because we hold the i_mutex.
384          */
385         if (pos > inode->i_size)
386                 i_size_write(inode, pos);
387         set_page_dirty(page);
388         return 0;
389 }
390 
391 int simple_write_end(struct file *file, struct address_space *mapping,
392                         loff_t pos, unsigned len, unsigned copied,
393                         struct page *page, void *fsdata)
394 {
395         unsigned from = pos & (PAGE_CACHE_SIZE - 1);
396 
397         /* zero the stale part of the page if we did a short copy */
398         if (copied < len) {
399                 void *kaddr = kmap_atomic(page, KM_USER0);
400                 memset(kaddr + from + copied, 0, len - copied);
401                 flush_dcache_page(page);
402                 kunmap_atomic(kaddr, KM_USER0);
403         }
404 
405         simple_commit_write(file, page, from, from+copied);
406 
407         unlock_page(page);
408         page_cache_release(page);
409 
410         return copied;
411 }
412 
413 /*
414  * the inodes created here are not hashed. If you use iunique to generate
415  * unique inode values later for this filesystem, then you must take care
416  * to pass it an appropriate max_reserved value to avoid collisions.
417  */
418 int simple_fill_super(struct super_block *s, unsigned long magic,
419                       struct tree_descr *files)
420 {
421         struct inode *inode;
422         struct dentry *root;
423         struct dentry *dentry;
424         int i;
425 
426         s->s_blocksize = PAGE_CACHE_SIZE;
427         s->s_blocksize_bits = PAGE_CACHE_SHIFT;
428         s->s_magic = magic;
429         s->s_op = &simple_super_operations;
430         s->s_time_gran = 1;
431 
432         inode = new_inode(s);
433         if (!inode)
434                 return -ENOMEM;
435         /*
436          * because the root inode is 1, the files array must not contain an
437          * entry at index 1
438          */
439         inode->i_ino = 1;
440         inode->i_mode = S_IFDIR | 0755;
441         inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
442         inode->i_op = &simple_dir_inode_operations;
443         inode->i_fop = &simple_dir_operations;
444         inode->i_nlink = 2;
445         root = d_alloc_root(inode);
446         if (!root) {
447                 iput(inode);
448                 return -ENOMEM;
449         }
450         for (i = 0; !files->name || files->name[0]; i++, files++) {
451                 if (!files->name)
452                         continue;
453 
454                 /* warn if it tries to conflict with the root inode */
455                 if (unlikely(i == 1))
456                         printk(KERN_WARNING "%s: %s passed in a files array"
457                                 "with an index of 1!\n", __func__,
458                                 s->s_type->name);
459 
460                 dentry = d_alloc_name(root, files->name);
461                 if (!dentry)
462                         goto out;
463                 inode = new_inode(s);
464                 if (!inode)
465                         goto out;
466                 inode->i_mode = S_IFREG | files->mode;
467                 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
468                 inode->i_fop = files->ops;
469                 inode->i_ino = i;
470                 d_add(dentry, inode);
471         }
472         s->s_root = root;
473         return 0;
474 out:
475         d_genocide(root);
476         dput(root);
477         return -ENOMEM;
478 }
479 
480 static DEFINE_SPINLOCK(pin_fs_lock);
481 
482 int simple_pin_fs(struct file_system_type *type, struct vfsmount **mount, int *count)
483 {
484         struct vfsmount *mnt = NULL;
485         spin_lock(&pin_fs_lock);
486         if (unlikely(!*mount)) {
487                 spin_unlock(&pin_fs_lock);
488                 mnt = vfs_kern_mount(type, 0, type->name, NULL);
489                 if (IS_ERR(mnt))
490                         return PTR_ERR(mnt);
491                 spin_lock(&pin_fs_lock);
492                 if (!*mount)
493                         *mount = mnt;
494         }
495         mntget(*mount);
496         ++*count;
497         spin_unlock(&pin_fs_lock);
498         mntput(mnt);
499         return 0;
500 }
501 
502 void simple_release_fs(struct vfsmount **mount, int *count)
503 {
504         struct vfsmount *mnt;
505         spin_lock(&pin_fs_lock);
506         mnt = *mount;
507         if (!--*count)
508                 *mount = NULL;
509         spin_unlock(&pin_fs_lock);
510         mntput(mnt);
511 }
512 
513 /**
514  * simple_read_from_buffer - copy data from the buffer to user space
515  * @to: the user space buffer to read to
516  * @count: the maximum number of bytes to read
517  * @ppos: the current position in the buffer
518  * @from: the buffer to read from
519  * @available: the size of the buffer
520  *
521  * The simple_read_from_buffer() function reads up to @count bytes from the
522  * buffer @from at offset @ppos into the user space address starting at @to.
523  *
524  * On success, the number of bytes read is returned and the offset @ppos is
525  * advanced by this number, or negative value is returned on error.
526  **/
527 ssize_t simple_read_from_buffer(void __user *to, size_t count, loff_t *ppos,
528                                 const void *from, size_t available)
529 {
530         loff_t pos = *ppos;
531         size_t ret;
532 
533         if (pos < 0)
534                 return -EINVAL;
535         if (pos >= available || !count)
536                 return 0;
537         if (count > available - pos)
538                 count = available - pos;
539         ret = copy_to_user(to, from + pos, count);
540         if (ret == count)
541                 return -EFAULT;
542         count -= ret;
543         *ppos = pos + count;
544         return count;
545 }
546 
547 /**
548  * memory_read_from_buffer - copy data from the buffer
549  * @to: the kernel space buffer to read to
550  * @count: the maximum number of bytes to read
551  * @ppos: the current position in the buffer
552  * @from: the buffer to read from
553  * @available: the size of the buffer
554  *
555  * The memory_read_from_buffer() function reads up to @count bytes from the
556  * buffer @from at offset @ppos into the kernel space address starting at @to.
557  *
558  * On success, the number of bytes read is returned and the offset @ppos is
559  * advanced by this number, or negative value is returned on error.
560  **/
561 ssize_t memory_read_from_buffer(void *to, size_t count, loff_t *ppos,
562                                 const void *from, size_t available)
563 {
564         loff_t pos = *ppos;
565 
566         if (pos < 0)
567                 return -EINVAL;
568         if (pos >= available)
569                 return 0;
570         if (count > available - pos)
571                 count = available - pos;
572         memcpy(to, from + pos, count);
573         *ppos = pos + count;
574 
575         return count;
576 }
577 
578 /*
579  * Transaction based IO.
580  * The file expects a single write which triggers the transaction, and then
581  * possibly a read which collects the result - which is stored in a
582  * file-local buffer.
583  */
584 
585 void simple_transaction_set(struct file *file, size_t n)
586 {
587         struct simple_transaction_argresp *ar = file->private_data;
588 
589         BUG_ON(n > SIMPLE_TRANSACTION_LIMIT);
590 
591         /*
592          * The barrier ensures that ar->size will really remain zero until
593          * ar->data is ready for reading.
594          */
595         smp_mb();
596         ar->size = n;
597 }
598 
599 char *simple_transaction_get(struct file *file, const char __user *buf, size_t size)
600 {
601         struct simple_transaction_argresp *ar;
602         static DEFINE_SPINLOCK(simple_transaction_lock);
603 
604         if (size > SIMPLE_TRANSACTION_LIMIT - 1)
605                 return ERR_PTR(-EFBIG);
606 
607         ar = (struct simple_transaction_argresp *)get_zeroed_page(GFP_KERNEL);
608         if (!ar)
609                 return ERR_PTR(-ENOMEM);
610 
611         spin_lock(&simple_transaction_lock);
612 
613         /* only one write allowed per open */
614         if (file->private_data) {
615                 spin_unlock(&simple_transaction_lock);
616                 free_page((unsigned long)ar);
617                 return ERR_PTR(-EBUSY);
618         }
619 
620         file->private_data = ar;
621 
622         spin_unlock(&simple_transaction_lock);
623 
624         if (copy_from_user(ar->data, buf, size))
625                 return ERR_PTR(-EFAULT);
626 
627         return ar->data;
628 }
629 
630 ssize_t simple_transaction_read(struct file *file, char __user *buf, size_t size, loff_t *pos)
631 {
632         struct simple_transaction_argresp *ar = file->private_data;
633 
634         if (!ar)
635                 return 0;
636         return simple_read_from_buffer(buf, size, pos, ar->data, ar->size);
637 }
638 
639 int simple_transaction_release(struct inode *inode, struct file *file)
640 {
641         free_page((unsigned long)file->private_data);
642         return 0;
643 }
644 
645 /* Simple attribute files */
646 
647 struct simple_attr {
648         int (*get)(void *, u64 *);
649         int (*set)(void *, u64);
650         char get_buf[24];       /* enough to store a u64 and "\n\0" */
651         char set_buf[24];
652         void *data;
653         const char *fmt;        /* format for read operation */
654         struct mutex mutex;     /* protects access to these buffers */
655 };
656 
657 /* simple_attr_open is called by an actual attribute open file operation
658  * to set the attribute specific access operations. */
659 int simple_attr_open(struct inode *inode, struct file *file,
660                      int (*get)(void *, u64 *), int (*set)(void *, u64),
661                      const char *fmt)
662 {
663         struct simple_attr *attr;
664 
665         attr = kmalloc(sizeof(*attr), GFP_KERNEL);
666         if (!attr)
667                 return -ENOMEM;
668 
669         attr->get = get;
670         attr->set = set;
671         attr->data = inode->i_private;
672         attr->fmt = fmt;
673         mutex_init(&attr->mutex);
674 
675         file->private_data = attr;
676 
677         return nonseekable_open(inode, file);
678 }
679 
680 int simple_attr_release(struct inode *inode, struct file *file)
681 {
682         kfree(file->private_data);
683         return 0;
684 }
685 
686 /* read from the buffer that is filled with the get function */
687 ssize_t simple_attr_read(struct file *file, char __user *buf,
688                          size_t len, loff_t *ppos)
689 {
690         struct simple_attr *attr;
691         size_t size;
692         ssize_t ret;
693 
694         attr = file->private_data;
695 
696         if (!attr->get)
697                 return -EACCES;
698 
699         ret = mutex_lock_interruptible(&attr->mutex);
700         if (ret)
701                 return ret;
702 
703         if (*ppos) {            /* continued read */
704                 size = strlen(attr->get_buf);
705         } else {                /* first read */
706                 u64 val;
707                 ret = attr->get(attr->data, &val);
708                 if (ret)
709                         goto out;
710 
711                 size = scnprintf(attr->get_buf, sizeof(attr->get_buf),
712                                  attr->fmt, (unsigned long long)val);
713         }
714 
715         ret = simple_read_from_buffer(buf, len, ppos, attr->get_buf, size);
716 out:
717         mutex_unlock(&attr->mutex);
718         return ret;
719 }
720 
721 /* interpret the buffer as a number to call the set function with */
722 ssize_t simple_attr_write(struct file *file, const char __user *buf,
723                           size_t len, loff_t *ppos)
724 {
725         struct simple_attr *attr;
726         u64 val;
727         size_t size;
728         ssize_t ret;
729 
730         attr = file->private_data;
731         if (!attr->set)
732                 return -EACCES;
733 
734         ret = mutex_lock_interruptible(&attr->mutex);
735         if (ret)
736                 return ret;
737 
738         ret = -EFAULT;
739         size = min(sizeof(attr->set_buf) - 1, len);
740         if (copy_from_user(attr->set_buf, buf, size))
741                 goto out;
742 
743         attr->set_buf[size] = '\0';
744         val = simple_strtol(attr->set_buf, NULL, 0);
745         ret = attr->set(attr->data, val);
746         if (ret == 0)
747                 ret = len; /* on success, claim we got the whole input */
748 out:
749         mutex_unlock(&attr->mutex);
750         return ret;
751 }
752 
753 /**
754  * generic_fh_to_dentry - generic helper for the fh_to_dentry export operation
755  * @sb:         filesystem to do the file handle conversion on
756  * @fid:        file handle to convert
757  * @fh_len:     length of the file handle in bytes
758  * @fh_type:    type of file handle
759  * @get_inode:  filesystem callback to retrieve inode
760  *
761  * This function decodes @fid as long as it has one of the well-known
762  * Linux filehandle types and calls @get_inode on it to retrieve the
763  * inode for the object specified in the file handle.
764  */
765 struct dentry *generic_fh_to_dentry(struct super_block *sb, struct fid *fid,
766                 int fh_len, int fh_type, struct inode *(*get_inode)
767                         (struct super_block *sb, u64 ino, u32 gen))
768 {
769         struct inode *inode = NULL;
770 
771         if (fh_len < 2)
772                 return NULL;
773 
774         switch (fh_type) {
775         case FILEID_INO32_GEN:
776         case FILEID_INO32_GEN_PARENT:
777                 inode = get_inode(sb, fid->i32.ino, fid->i32.gen);
778                 break;
779         }
780 
781         return d_obtain_alias(inode);
782 }
783 EXPORT_SYMBOL_GPL(generic_fh_to_dentry);
784 
785 /**
786  * generic_fh_to_dentry - generic helper for the fh_to_parent export operation
787  * @sb:         filesystem to do the file handle conversion on
788  * @fid:        file handle to convert
789  * @fh_len:     length of the file handle in bytes
790  * @fh_type:    type of file handle
791  * @get_inode:  filesystem callback to retrieve inode
792  *
793  * This function decodes @fid as long as it has one of the well-known
794  * Linux filehandle types and calls @get_inode on it to retrieve the
795  * inode for the _parent_ object specified in the file handle if it
796  * is specified in the file handle, or NULL otherwise.
797  */
798 struct dentry *generic_fh_to_parent(struct super_block *sb, struct fid *fid,
799                 int fh_len, int fh_type, struct inode *(*get_inode)
800                         (struct super_block *sb, u64 ino, u32 gen))
801 {
802         struct inode *inode = NULL;
803 
804         if (fh_len <= 2)
805                 return NULL;
806 
807         switch (fh_type) {
808         case FILEID_INO32_GEN_PARENT:
809                 inode = get_inode(sb, fid->i32.parent_ino,
810                                   (fh_len > 3 ? fid->i32.parent_gen : 0));
811                 break;
812         }
813 
814         return d_obtain_alias(inode);
815 }
816 EXPORT_SYMBOL_GPL(generic_fh_to_parent);
817 
818 int simple_fsync(struct file *file, struct dentry *dentry, int datasync)
819 {
820         struct writeback_control wbc = {
821                 .sync_mode = WB_SYNC_ALL,
822                 .nr_to_write = 0, /* metadata-only; caller takes care of data */
823         };
824         struct inode *inode = dentry->d_inode;
825         int err;
826         int ret;
827 
828         ret = sync_mapping_buffers(inode->i_mapping);
829         if (!(inode->i_state & I_DIRTY))
830                 return ret;
831         if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
832                 return ret;
833 
834         err = sync_inode(inode, &wbc);
835         if (ret == 0)
836                 ret = err;
837         return ret;
838 }
839 EXPORT_SYMBOL(simple_fsync);
840 
841 EXPORT_SYMBOL(dcache_dir_close);
842 EXPORT_SYMBOL(dcache_dir_lseek);
843 EXPORT_SYMBOL(dcache_dir_open);
844 EXPORT_SYMBOL(dcache_readdir);
845 EXPORT_SYMBOL(generic_read_dir);
846 EXPORT_SYMBOL(get_sb_pseudo);
847 EXPORT_SYMBOL(simple_write_begin);
848 EXPORT_SYMBOL(simple_write_end);
849 EXPORT_SYMBOL(simple_dir_inode_operations);
850 EXPORT_SYMBOL(simple_dir_operations);
851 EXPORT_SYMBOL(simple_empty);
852 EXPORT_SYMBOL(d_alloc_name);
853 EXPORT_SYMBOL(simple_fill_super);
854 EXPORT_SYMBOL(simple_getattr);
855 EXPORT_SYMBOL(simple_link);
856 EXPORT_SYMBOL(simple_lookup);
857 EXPORT_SYMBOL(simple_pin_fs);
858 EXPORT_UNUSED_SYMBOL(simple_prepare_write);
859 EXPORT_SYMBOL(simple_readpage);
860 EXPORT_SYMBOL(simple_release_fs);
861 EXPORT_SYMBOL(simple_rename);
862 EXPORT_SYMBOL(simple_rmdir);
863 EXPORT_SYMBOL(simple_statfs);
864 EXPORT_SYMBOL(simple_sync_file);
865 EXPORT_SYMBOL(simple_unlink);
866 EXPORT_SYMBOL(simple_read_from_buffer);
867 EXPORT_SYMBOL(memory_read_from_buffer);
868 EXPORT_SYMBOL(simple_transaction_set);
869 EXPORT_SYMBOL(simple_transaction_get);
870 EXPORT_SYMBOL(simple_transaction_read);
871 EXPORT_SYMBOL(simple_transaction_release);
872 EXPORT_SYMBOL_GPL(simple_attr_open);
873 EXPORT_SYMBOL_GPL(simple_attr_release);
874 EXPORT_SYMBOL_GPL(simple_attr_read);
875 EXPORT_SYMBOL_GPL(simple_attr_write);
876 

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