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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/blkdev.h>
  7 #include <linux/export.h>
  8 #include <linux/pagemap.h>
  9 #include <linux/slab.h>
 10 #include <linux/cred.h>
 11 #include <linux/mount.h>
 12 #include <linux/vfs.h>
 13 #include <linux/quotaops.h>
 14 #include <linux/mutex.h>
 15 #include <linux/namei.h>
 16 #include <linux/exportfs.h>
 17 #include <linux/writeback.h>
 18 #include <linux/buffer_head.h> /* sync_mapping_buffers */
 19 
 20 #include <linux/uaccess.h>
 21 
 22 #include "internal.h"
 23 
 24 int simple_getattr(const struct path *path, struct kstat *stat,
 25                    u32 request_mask, unsigned int query_flags)
 26 {
 27         struct inode *inode = d_inode(path->dentry);
 28         generic_fillattr(inode, stat);
 29         stat->blocks = inode->i_mapping->nrpages << (PAGE_SHIFT - 9);
 30         return 0;
 31 }
 32 EXPORT_SYMBOL(simple_getattr);
 33 
 34 int simple_statfs(struct dentry *dentry, struct kstatfs *buf)
 35 {
 36         buf->f_type = dentry->d_sb->s_magic;
 37         buf->f_bsize = PAGE_SIZE;
 38         buf->f_namelen = NAME_MAX;
 39         return 0;
 40 }
 41 EXPORT_SYMBOL(simple_statfs);
 42 
 43 /*
 44  * Retaining negative dentries for an in-memory filesystem just wastes
 45  * memory and lookup time: arrange for them to be deleted immediately.
 46  */
 47 int always_delete_dentry(const struct dentry *dentry)
 48 {
 49         return 1;
 50 }
 51 EXPORT_SYMBOL(always_delete_dentry);
 52 
 53 const struct dentry_operations simple_dentry_operations = {
 54         .d_delete = always_delete_dentry,
 55 };
 56 EXPORT_SYMBOL(simple_dentry_operations);
 57 
 58 /*
 59  * Lookup the data. This is trivial - if the dentry didn't already
 60  * exist, we know it is negative.  Set d_op to delete negative dentries.
 61  */
 62 struct dentry *simple_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
 63 {
 64         if (dentry->d_name.len > NAME_MAX)
 65                 return ERR_PTR(-ENAMETOOLONG);
 66         if (!dentry->d_sb->s_d_op)
 67                 d_set_d_op(dentry, &simple_dentry_operations);
 68         d_add(dentry, NULL);
 69         return NULL;
 70 }
 71 EXPORT_SYMBOL(simple_lookup);
 72 
 73 int dcache_dir_open(struct inode *inode, struct file *file)
 74 {
 75         file->private_data = d_alloc_cursor(file->f_path.dentry);
 76 
 77         return file->private_data ? 0 : -ENOMEM;
 78 }
 79 EXPORT_SYMBOL(dcache_dir_open);
 80 
 81 int dcache_dir_close(struct inode *inode, struct file *file)
 82 {
 83         dput(file->private_data);
 84         return 0;
 85 }
 86 EXPORT_SYMBOL(dcache_dir_close);
 87 
 88 /* parent is locked at least shared */
 89 static struct dentry *next_positive(struct dentry *parent,
 90                                     struct list_head *from,
 91                                     int count)
 92 {
 93         unsigned *seq = &parent->d_inode->i_dir_seq, n;
 94         struct dentry *res;
 95         struct list_head *p;
 96         bool skipped;
 97         int i;
 98 
 99 retry:
100         i = count;
101         skipped = false;
102         n = smp_load_acquire(seq) & ~1;
103         res = NULL;
104         rcu_read_lock();
105         for (p = from->next; p != &parent->d_subdirs; p = p->next) {
106                 struct dentry *d = list_entry(p, struct dentry, d_child);
107                 if (!simple_positive(d)) {
108                         skipped = true;
109                 } else if (!--i) {
110                         res = d;
111                         break;
112                 }
113         }
114         rcu_read_unlock();
115         if (skipped) {
116                 smp_rmb();
117                 if (unlikely(*seq != n))
118                         goto retry;
119         }
120         return res;
121 }
122 
123 static void move_cursor(struct dentry *cursor, struct list_head *after)
124 {
125         struct dentry *parent = cursor->d_parent;
126         unsigned n, *seq = &parent->d_inode->i_dir_seq;
127         spin_lock(&parent->d_lock);
128         for (;;) {
129                 n = *seq;
130                 if (!(n & 1) && cmpxchg(seq, n, n + 1) == n)
131                         break;
132                 cpu_relax();
133         }
134         __list_del(cursor->d_child.prev, cursor->d_child.next);
135         if (after)
136                 list_add(&cursor->d_child, after);
137         else
138                 list_add_tail(&cursor->d_child, &parent->d_subdirs);
139         smp_store_release(seq, n + 2);
140         spin_unlock(&parent->d_lock);
141 }
142 
143 loff_t dcache_dir_lseek(struct file *file, loff_t offset, int whence)
144 {
145         struct dentry *dentry = file->f_path.dentry;
146         switch (whence) {
147                 case 1:
148                         offset += file->f_pos;
149                 case 0:
150                         if (offset >= 0)
151                                 break;
152                 default:
153                         return -EINVAL;
154         }
155         if (offset != file->f_pos) {
156                 file->f_pos = offset;
157                 if (file->f_pos >= 2) {
158                         struct dentry *cursor = file->private_data;
159                         struct dentry *to;
160                         loff_t n = file->f_pos - 2;
161 
162                         inode_lock_shared(dentry->d_inode);
163                         to = next_positive(dentry, &dentry->d_subdirs, n);
164                         move_cursor(cursor, to ? &to->d_child : NULL);
165                         inode_unlock_shared(dentry->d_inode);
166                 }
167         }
168         return offset;
169 }
170 EXPORT_SYMBOL(dcache_dir_lseek);
171 
172 /* Relationship between i_mode and the DT_xxx types */
173 static inline unsigned char dt_type(struct inode *inode)
174 {
175         return (inode->i_mode >> 12) & 15;
176 }
177 
178 /*
179  * Directory is locked and all positive dentries in it are safe, since
180  * for ramfs-type trees they can't go away without unlink() or rmdir(),
181  * both impossible due to the lock on directory.
182  */
183 
184 int dcache_readdir(struct file *file, struct dir_context *ctx)
185 {
186         struct dentry *dentry = file->f_path.dentry;
187         struct dentry *cursor = file->private_data;
188         struct list_head *p = &cursor->d_child;
189         struct dentry *next;
190         bool moved = false;
191 
192         if (!dir_emit_dots(file, ctx))
193                 return 0;
194 
195         if (ctx->pos == 2)
196                 p = &dentry->d_subdirs;
197         while ((next = next_positive(dentry, p, 1)) != NULL) {
198                 if (!dir_emit(ctx, next->d_name.name, next->d_name.len,
199                               d_inode(next)->i_ino, dt_type(d_inode(next))))
200                         break;
201                 moved = true;
202                 p = &next->d_child;
203                 ctx->pos++;
204         }
205         if (moved)
206                 move_cursor(cursor, p);
207         return 0;
208 }
209 EXPORT_SYMBOL(dcache_readdir);
210 
211 ssize_t generic_read_dir(struct file *filp, char __user *buf, size_t siz, loff_t *ppos)
212 {
213         return -EISDIR;
214 }
215 EXPORT_SYMBOL(generic_read_dir);
216 
217 const struct file_operations simple_dir_operations = {
218         .open           = dcache_dir_open,
219         .release        = dcache_dir_close,
220         .llseek         = dcache_dir_lseek,
221         .read           = generic_read_dir,
222         .iterate_shared = dcache_readdir,
223         .fsync          = noop_fsync,
224 };
225 EXPORT_SYMBOL(simple_dir_operations);
226 
227 const struct inode_operations simple_dir_inode_operations = {
228         .lookup         = simple_lookup,
229 };
230 EXPORT_SYMBOL(simple_dir_inode_operations);
231 
232 static const struct super_operations simple_super_operations = {
233         .statfs         = simple_statfs,
234 };
235 
236 /*
237  * Common helper for pseudo-filesystems (sockfs, pipefs, bdev - stuff that
238  * will never be mountable)
239  */
240 struct dentry *mount_pseudo_xattr(struct file_system_type *fs_type, char *name,
241         const struct super_operations *ops, const struct xattr_handler **xattr,
242         const struct dentry_operations *dops, unsigned long magic)
243 {
244         struct super_block *s;
245         struct dentry *dentry;
246         struct inode *root;
247         struct qstr d_name = QSTR_INIT(name, strlen(name));
248 
249         s = sget_userns(fs_type, NULL, set_anon_super, SB_KERNMOUNT|SB_NOUSER,
250                         &init_user_ns, NULL);
251         if (IS_ERR(s))
252                 return ERR_CAST(s);
253 
254         s->s_maxbytes = MAX_LFS_FILESIZE;
255         s->s_blocksize = PAGE_SIZE;
256         s->s_blocksize_bits = PAGE_SHIFT;
257         s->s_magic = magic;
258         s->s_op = ops ? ops : &simple_super_operations;
259         s->s_xattr = xattr;
260         s->s_time_gran = 1;
261         root = new_inode(s);
262         if (!root)
263                 goto Enomem;
264         /*
265          * since this is the first inode, make it number 1. New inodes created
266          * after this must take care not to collide with it (by passing
267          * max_reserved of 1 to iunique).
268          */
269         root->i_ino = 1;
270         root->i_mode = S_IFDIR | S_IRUSR | S_IWUSR;
271         root->i_atime = root->i_mtime = root->i_ctime = current_time(root);
272         dentry = __d_alloc(s, &d_name);
273         if (!dentry) {
274                 iput(root);
275                 goto Enomem;
276         }
277         d_instantiate(dentry, root);
278         s->s_root = dentry;
279         s->s_d_op = dops;
280         s->s_flags |= SB_ACTIVE;
281         return dget(s->s_root);
282 
283 Enomem:
284         deactivate_locked_super(s);
285         return ERR_PTR(-ENOMEM);
286 }
287 EXPORT_SYMBOL(mount_pseudo_xattr);
288 
289 int simple_open(struct inode *inode, struct file *file)
290 {
291         if (inode->i_private)
292                 file->private_data = inode->i_private;
293         return 0;
294 }
295 EXPORT_SYMBOL(simple_open);
296 
297 int simple_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
298 {
299         struct inode *inode = d_inode(old_dentry);
300 
301         inode->i_ctime = dir->i_ctime = dir->i_mtime = current_time(inode);
302         inc_nlink(inode);
303         ihold(inode);
304         dget(dentry);
305         d_instantiate(dentry, inode);
306         return 0;
307 }
308 EXPORT_SYMBOL(simple_link);
309 
310 int simple_empty(struct dentry *dentry)
311 {
312         struct dentry *child;
313         int ret = 0;
314 
315         spin_lock(&dentry->d_lock);
316         list_for_each_entry(child, &dentry->d_subdirs, d_child) {
317                 spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED);
318                 if (simple_positive(child)) {
319                         spin_unlock(&child->d_lock);
320                         goto out;
321                 }
322                 spin_unlock(&child->d_lock);
323         }
324         ret = 1;
325 out:
326         spin_unlock(&dentry->d_lock);
327         return ret;
328 }
329 EXPORT_SYMBOL(simple_empty);
330 
331 int simple_unlink(struct inode *dir, struct dentry *dentry)
332 {
333         struct inode *inode = d_inode(dentry);
334 
335         inode->i_ctime = dir->i_ctime = dir->i_mtime = current_time(inode);
336         drop_nlink(inode);
337         dput(dentry);
338         return 0;
339 }
340 EXPORT_SYMBOL(simple_unlink);
341 
342 int simple_rmdir(struct inode *dir, struct dentry *dentry)
343 {
344         if (!simple_empty(dentry))
345                 return -ENOTEMPTY;
346 
347         drop_nlink(d_inode(dentry));
348         simple_unlink(dir, dentry);
349         drop_nlink(dir);
350         return 0;
351 }
352 EXPORT_SYMBOL(simple_rmdir);
353 
354 int simple_rename(struct inode *old_dir, struct dentry *old_dentry,
355                   struct inode *new_dir, struct dentry *new_dentry,
356                   unsigned int flags)
357 {
358         struct inode *inode = d_inode(old_dentry);
359         int they_are_dirs = d_is_dir(old_dentry);
360 
361         if (flags & ~RENAME_NOREPLACE)
362                 return -EINVAL;
363 
364         if (!simple_empty(new_dentry))
365                 return -ENOTEMPTY;
366 
367         if (d_really_is_positive(new_dentry)) {
368                 simple_unlink(new_dir, new_dentry);
369                 if (they_are_dirs) {
370                         drop_nlink(d_inode(new_dentry));
371                         drop_nlink(old_dir);
372                 }
373         } else if (they_are_dirs) {
374                 drop_nlink(old_dir);
375                 inc_nlink(new_dir);
376         }
377 
378         old_dir->i_ctime = old_dir->i_mtime = new_dir->i_ctime =
379                 new_dir->i_mtime = inode->i_ctime = current_time(old_dir);
380 
381         return 0;
382 }
383 EXPORT_SYMBOL(simple_rename);
384 
385 /**
386  * simple_setattr - setattr for simple filesystem
387  * @dentry: dentry
388  * @iattr: iattr structure
389  *
390  * Returns 0 on success, -error on failure.
391  *
392  * simple_setattr is a simple ->setattr implementation without a proper
393  * implementation of size changes.
394  *
395  * It can either be used for in-memory filesystems or special files
396  * on simple regular filesystems.  Anything that needs to change on-disk
397  * or wire state on size changes needs its own setattr method.
398  */
399 int simple_setattr(struct dentry *dentry, struct iattr *iattr)
400 {
401         struct inode *inode = d_inode(dentry);
402         int error;
403 
404         error = setattr_prepare(dentry, iattr);
405         if (error)
406                 return error;
407 
408         if (iattr->ia_valid & ATTR_SIZE)
409                 truncate_setsize(inode, iattr->ia_size);
410         setattr_copy(inode, iattr);
411         mark_inode_dirty(inode);
412         return 0;
413 }
414 EXPORT_SYMBOL(simple_setattr);
415 
416 int simple_readpage(struct file *file, struct page *page)
417 {
418         clear_highpage(page);
419         flush_dcache_page(page);
420         SetPageUptodate(page);
421         unlock_page(page);
422         return 0;
423 }
424 EXPORT_SYMBOL(simple_readpage);
425 
426 int simple_write_begin(struct file *file, struct address_space *mapping,
427                         loff_t pos, unsigned len, unsigned flags,
428                         struct page **pagep, void **fsdata)
429 {
430         struct page *page;
431         pgoff_t index;
432 
433         index = pos >> PAGE_SHIFT;
434 
435         page = grab_cache_page_write_begin(mapping, index, flags);
436         if (!page)
437                 return -ENOMEM;
438 
439         *pagep = page;
440 
441         if (!PageUptodate(page) && (len != PAGE_SIZE)) {
442                 unsigned from = pos & (PAGE_SIZE - 1);
443 
444                 zero_user_segments(page, 0, from, from + len, PAGE_SIZE);
445         }
446         return 0;
447 }
448 EXPORT_SYMBOL(simple_write_begin);
449 
450 /**
451  * simple_write_end - .write_end helper for non-block-device FSes
452  * @available: See .write_end of address_space_operations
453  * @file:               "
454  * @mapping:            "
455  * @pos:                "
456  * @len:                "
457  * @copied:             "
458  * @page:               "
459  * @fsdata:             "
460  *
461  * simple_write_end does the minimum needed for updating a page after writing is
462  * done. It has the same API signature as the .write_end of
463  * address_space_operations vector. So it can just be set onto .write_end for
464  * FSes that don't need any other processing. i_mutex is assumed to be held.
465  * Block based filesystems should use generic_write_end().
466  * NOTE: Even though i_size might get updated by this function, mark_inode_dirty
467  * is not called, so a filesystem that actually does store data in .write_inode
468  * should extend on what's done here with a call to mark_inode_dirty() in the
469  * case that i_size has changed.
470  *
471  * Use *ONLY* with simple_readpage()
472  */
473 int simple_write_end(struct file *file, struct address_space *mapping,
474                         loff_t pos, unsigned len, unsigned copied,
475                         struct page *page, void *fsdata)
476 {
477         struct inode *inode = page->mapping->host;
478         loff_t last_pos = pos + copied;
479 
480         /* zero the stale part of the page if we did a short copy */
481         if (!PageUptodate(page)) {
482                 if (copied < len) {
483                         unsigned from = pos & (PAGE_SIZE - 1);
484 
485                         zero_user(page, from + copied, len - copied);
486                 }
487                 SetPageUptodate(page);
488         }
489         /*
490          * No need to use i_size_read() here, the i_size
491          * cannot change under us because we hold the i_mutex.
492          */
493         if (last_pos > inode->i_size)
494                 i_size_write(inode, last_pos);
495 
496         set_page_dirty(page);
497         unlock_page(page);
498         put_page(page);
499 
500         return copied;
501 }
502 EXPORT_SYMBOL(simple_write_end);
503 
504 /*
505  * the inodes created here are not hashed. If you use iunique to generate
506  * unique inode values later for this filesystem, then you must take care
507  * to pass it an appropriate max_reserved value to avoid collisions.
508  */
509 int simple_fill_super(struct super_block *s, unsigned long magic,
510                       const struct tree_descr *files)
511 {
512         struct inode *inode;
513         struct dentry *root;
514         struct dentry *dentry;
515         int i;
516 
517         s->s_blocksize = PAGE_SIZE;
518         s->s_blocksize_bits = PAGE_SHIFT;
519         s->s_magic = magic;
520         s->s_op = &simple_super_operations;
521         s->s_time_gran = 1;
522 
523         inode = new_inode(s);
524         if (!inode)
525                 return -ENOMEM;
526         /*
527          * because the root inode is 1, the files array must not contain an
528          * entry at index 1
529          */
530         inode->i_ino = 1;
531         inode->i_mode = S_IFDIR | 0755;
532         inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
533         inode->i_op = &simple_dir_inode_operations;
534         inode->i_fop = &simple_dir_operations;
535         set_nlink(inode, 2);
536         root = d_make_root(inode);
537         if (!root)
538                 return -ENOMEM;
539         for (i = 0; !files->name || files->name[0]; i++, files++) {
540                 if (!files->name)
541                         continue;
542 
543                 /* warn if it tries to conflict with the root inode */
544                 if (unlikely(i == 1))
545                         printk(KERN_WARNING "%s: %s passed in a files array"
546                                 "with an index of 1!\n", __func__,
547                                 s->s_type->name);
548 
549                 dentry = d_alloc_name(root, files->name);
550                 if (!dentry)
551                         goto out;
552                 inode = new_inode(s);
553                 if (!inode) {
554                         dput(dentry);
555                         goto out;
556                 }
557                 inode->i_mode = S_IFREG | files->mode;
558                 inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
559                 inode->i_fop = files->ops;
560                 inode->i_ino = i;
561                 d_add(dentry, inode);
562         }
563         s->s_root = root;
564         return 0;
565 out:
566         d_genocide(root);
567         shrink_dcache_parent(root);
568         dput(root);
569         return -ENOMEM;
570 }
571 EXPORT_SYMBOL(simple_fill_super);
572 
573 static DEFINE_SPINLOCK(pin_fs_lock);
574 
575 int simple_pin_fs(struct file_system_type *type, struct vfsmount **mount, int *count)
576 {
577         struct vfsmount *mnt = NULL;
578         spin_lock(&pin_fs_lock);
579         if (unlikely(!*mount)) {
580                 spin_unlock(&pin_fs_lock);
581                 mnt = vfs_kern_mount(type, SB_KERNMOUNT, type->name, NULL);
582                 if (IS_ERR(mnt))
583                         return PTR_ERR(mnt);
584                 spin_lock(&pin_fs_lock);
585                 if (!*mount)
586                         *mount = mnt;
587         }
588         mntget(*mount);
589         ++*count;
590         spin_unlock(&pin_fs_lock);
591         mntput(mnt);
592         return 0;
593 }
594 EXPORT_SYMBOL(simple_pin_fs);
595 
596 void simple_release_fs(struct vfsmount **mount, int *count)
597 {
598         struct vfsmount *mnt;
599         spin_lock(&pin_fs_lock);
600         mnt = *mount;
601         if (!--*count)
602                 *mount = NULL;
603         spin_unlock(&pin_fs_lock);
604         mntput(mnt);
605 }
606 EXPORT_SYMBOL(simple_release_fs);
607 
608 /**
609  * simple_read_from_buffer - copy data from the buffer to user space
610  * @to: the user space buffer to read to
611  * @count: the maximum number of bytes to read
612  * @ppos: the current position in the buffer
613  * @from: the buffer to read from
614  * @available: the size of the buffer
615  *
616  * The simple_read_from_buffer() function reads up to @count bytes from the
617  * buffer @from at offset @ppos into the user space address starting at @to.
618  *
619  * On success, the number of bytes read is returned and the offset @ppos is
620  * advanced by this number, or negative value is returned on error.
621  **/
622 ssize_t simple_read_from_buffer(void __user *to, size_t count, loff_t *ppos,
623                                 const void *from, size_t available)
624 {
625         loff_t pos = *ppos;
626         size_t ret;
627 
628         if (pos < 0)
629                 return -EINVAL;
630         if (pos >= available || !count)
631                 return 0;
632         if (count > available - pos)
633                 count = available - pos;
634         ret = copy_to_user(to, from + pos, count);
635         if (ret == count)
636                 return -EFAULT;
637         count -= ret;
638         *ppos = pos + count;
639         return count;
640 }
641 EXPORT_SYMBOL(simple_read_from_buffer);
642 
643 /**
644  * simple_write_to_buffer - copy data from user space to the buffer
645  * @to: the buffer to write to
646  * @available: the size of the buffer
647  * @ppos: the current position in the buffer
648  * @from: the user space buffer to read from
649  * @count: the maximum number of bytes to read
650  *
651  * The simple_write_to_buffer() function reads up to @count bytes from the user
652  * space address starting at @from into the buffer @to at offset @ppos.
653  *
654  * On success, the number of bytes written is returned and the offset @ppos is
655  * advanced by this number, or negative value is returned on error.
656  **/
657 ssize_t simple_write_to_buffer(void *to, size_t available, loff_t *ppos,
658                 const void __user *from, size_t count)
659 {
660         loff_t pos = *ppos;
661         size_t res;
662 
663         if (pos < 0)
664                 return -EINVAL;
665         if (pos >= available || !count)
666                 return 0;
667         if (count > available - pos)
668                 count = available - pos;
669         res = copy_from_user(to + pos, from, count);
670         if (res == count)
671                 return -EFAULT;
672         count -= res;
673         *ppos = pos + count;
674         return count;
675 }
676 EXPORT_SYMBOL(simple_write_to_buffer);
677 
678 /**
679  * memory_read_from_buffer - copy data from the buffer
680  * @to: the kernel space buffer to read to
681  * @count: the maximum number of bytes to read
682  * @ppos: the current position in the buffer
683  * @from: the buffer to read from
684  * @available: the size of the buffer
685  *
686  * The memory_read_from_buffer() function reads up to @count bytes from the
687  * buffer @from at offset @ppos into the kernel space address starting at @to.
688  *
689  * On success, the number of bytes read is returned and the offset @ppos is
690  * advanced by this number, or negative value is returned on error.
691  **/
692 ssize_t memory_read_from_buffer(void *to, size_t count, loff_t *ppos,
693                                 const void *from, size_t available)
694 {
695         loff_t pos = *ppos;
696 
697         if (pos < 0)
698                 return -EINVAL;
699         if (pos >= available)
700                 return 0;
701         if (count > available - pos)
702                 count = available - pos;
703         memcpy(to, from + pos, count);
704         *ppos = pos + count;
705 
706         return count;
707 }
708 EXPORT_SYMBOL(memory_read_from_buffer);
709 
710 /*
711  * Transaction based IO.
712  * The file expects a single write which triggers the transaction, and then
713  * possibly a read which collects the result - which is stored in a
714  * file-local buffer.
715  */
716 
717 void simple_transaction_set(struct file *file, size_t n)
718 {
719         struct simple_transaction_argresp *ar = file->private_data;
720 
721         BUG_ON(n > SIMPLE_TRANSACTION_LIMIT);
722 
723         /*
724          * The barrier ensures that ar->size will really remain zero until
725          * ar->data is ready for reading.
726          */
727         smp_mb();
728         ar->size = n;
729 }
730 EXPORT_SYMBOL(simple_transaction_set);
731 
732 char *simple_transaction_get(struct file *file, const char __user *buf, size_t size)
733 {
734         struct simple_transaction_argresp *ar;
735         static DEFINE_SPINLOCK(simple_transaction_lock);
736 
737         if (size > SIMPLE_TRANSACTION_LIMIT - 1)
738                 return ERR_PTR(-EFBIG);
739 
740         ar = (struct simple_transaction_argresp *)get_zeroed_page(GFP_KERNEL);
741         if (!ar)
742                 return ERR_PTR(-ENOMEM);
743 
744         spin_lock(&simple_transaction_lock);
745 
746         /* only one write allowed per open */
747         if (file->private_data) {
748                 spin_unlock(&simple_transaction_lock);
749                 free_page((unsigned long)ar);
750                 return ERR_PTR(-EBUSY);
751         }
752 
753         file->private_data = ar;
754 
755         spin_unlock(&simple_transaction_lock);
756 
757         if (copy_from_user(ar->data, buf, size))
758                 return ERR_PTR(-EFAULT);
759 
760         return ar->data;
761 }
762 EXPORT_SYMBOL(simple_transaction_get);
763 
764 ssize_t simple_transaction_read(struct file *file, char __user *buf, size_t size, loff_t *pos)
765 {
766         struct simple_transaction_argresp *ar = file->private_data;
767 
768         if (!ar)
769                 return 0;
770         return simple_read_from_buffer(buf, size, pos, ar->data, ar->size);
771 }
772 EXPORT_SYMBOL(simple_transaction_read);
773 
774 int simple_transaction_release(struct inode *inode, struct file *file)
775 {
776         free_page((unsigned long)file->private_data);
777         return 0;
778 }
779 EXPORT_SYMBOL(simple_transaction_release);
780 
781 /* Simple attribute files */
782 
783 struct simple_attr {
784         int (*get)(void *, u64 *);
785         int (*set)(void *, u64);
786         char get_buf[24];       /* enough to store a u64 and "\n\0" */
787         char set_buf[24];
788         void *data;
789         const char *fmt;        /* format for read operation */
790         struct mutex mutex;     /* protects access to these buffers */
791 };
792 
793 /* simple_attr_open is called by an actual attribute open file operation
794  * to set the attribute specific access operations. */
795 int simple_attr_open(struct inode *inode, struct file *file,
796                      int (*get)(void *, u64 *), int (*set)(void *, u64),
797                      const char *fmt)
798 {
799         struct simple_attr *attr;
800 
801         attr = kmalloc(sizeof(*attr), GFP_KERNEL);
802         if (!attr)
803                 return -ENOMEM;
804 
805         attr->get = get;
806         attr->set = set;
807         attr->data = inode->i_private;
808         attr->fmt = fmt;
809         mutex_init(&attr->mutex);
810 
811         file->private_data = attr;
812 
813         return nonseekable_open(inode, file);
814 }
815 EXPORT_SYMBOL_GPL(simple_attr_open);
816 
817 int simple_attr_release(struct inode *inode, struct file *file)
818 {
819         kfree(file->private_data);
820         return 0;
821 }
822 EXPORT_SYMBOL_GPL(simple_attr_release); /* GPL-only?  This?  Really? */
823 
824 /* read from the buffer that is filled with the get function */
825 ssize_t simple_attr_read(struct file *file, char __user *buf,
826                          size_t len, loff_t *ppos)
827 {
828         struct simple_attr *attr;
829         size_t size;
830         ssize_t ret;
831 
832         attr = file->private_data;
833 
834         if (!attr->get)
835                 return -EACCES;
836 
837         ret = mutex_lock_interruptible(&attr->mutex);
838         if (ret)
839                 return ret;
840 
841         if (*ppos) {            /* continued read */
842                 size = strlen(attr->get_buf);
843         } else {                /* first read */
844                 u64 val;
845                 ret = attr->get(attr->data, &val);
846                 if (ret)
847                         goto out;
848 
849                 size = scnprintf(attr->get_buf, sizeof(attr->get_buf),
850                                  attr->fmt, (unsigned long long)val);
851         }
852 
853         ret = simple_read_from_buffer(buf, len, ppos, attr->get_buf, size);
854 out:
855         mutex_unlock(&attr->mutex);
856         return ret;
857 }
858 EXPORT_SYMBOL_GPL(simple_attr_read);
859 
860 /* interpret the buffer as a number to call the set function with */
861 ssize_t simple_attr_write(struct file *file, const char __user *buf,
862                           size_t len, loff_t *ppos)
863 {
864         struct simple_attr *attr;
865         u64 val;
866         size_t size;
867         ssize_t ret;
868 
869         attr = file->private_data;
870         if (!attr->set)
871                 return -EACCES;
872 
873         ret = mutex_lock_interruptible(&attr->mutex);
874         if (ret)
875                 return ret;
876 
877         ret = -EFAULT;
878         size = min(sizeof(attr->set_buf) - 1, len);
879         if (copy_from_user(attr->set_buf, buf, size))
880                 goto out;
881 
882         attr->set_buf[size] = '\0';
883         val = simple_strtoll(attr->set_buf, NULL, 0);
884         ret = attr->set(attr->data, val);
885         if (ret == 0)
886                 ret = len; /* on success, claim we got the whole input */
887 out:
888         mutex_unlock(&attr->mutex);
889         return ret;
890 }
891 EXPORT_SYMBOL_GPL(simple_attr_write);
892 
893 /**
894  * generic_fh_to_dentry - generic helper for the fh_to_dentry 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 object specified in the file handle.
904  */
905 struct dentry *generic_fh_to_dentry(struct super_block *sb, struct fid *fid,
906                 int fh_len, int fh_type, struct inode *(*get_inode)
907                         (struct super_block *sb, u64 ino, u32 gen))
908 {
909         struct inode *inode = NULL;
910 
911         if (fh_len < 2)
912                 return NULL;
913 
914         switch (fh_type) {
915         case FILEID_INO32_GEN:
916         case FILEID_INO32_GEN_PARENT:
917                 inode = get_inode(sb, fid->i32.ino, fid->i32.gen);
918                 break;
919         }
920 
921         return d_obtain_alias(inode);
922 }
923 EXPORT_SYMBOL_GPL(generic_fh_to_dentry);
924 
925 /**
926  * generic_fh_to_parent - generic helper for the fh_to_parent export operation
927  * @sb:         filesystem to do the file handle conversion on
928  * @fid:        file handle to convert
929  * @fh_len:     length of the file handle in bytes
930  * @fh_type:    type of file handle
931  * @get_inode:  filesystem callback to retrieve inode
932  *
933  * This function decodes @fid as long as it has one of the well-known
934  * Linux filehandle types and calls @get_inode on it to retrieve the
935  * inode for the _parent_ object specified in the file handle if it
936  * is specified in the file handle, or NULL otherwise.
937  */
938 struct dentry *generic_fh_to_parent(struct super_block *sb, struct fid *fid,
939                 int fh_len, int fh_type, struct inode *(*get_inode)
940                         (struct super_block *sb, u64 ino, u32 gen))
941 {
942         struct inode *inode = NULL;
943 
944         if (fh_len <= 2)
945                 return NULL;
946 
947         switch (fh_type) {
948         case FILEID_INO32_GEN_PARENT:
949                 inode = get_inode(sb, fid->i32.parent_ino,
950                                   (fh_len > 3 ? fid->i32.parent_gen : 0));
951                 break;
952         }
953 
954         return d_obtain_alias(inode);
955 }
956 EXPORT_SYMBOL_GPL(generic_fh_to_parent);
957 
958 /**
959  * __generic_file_fsync - generic fsync implementation for simple filesystems
960  *
961  * @file:       file to synchronize
962  * @start:      start offset in bytes
963  * @end:        end offset in bytes (inclusive)
964  * @datasync:   only synchronize essential metadata if true
965  *
966  * This is a generic implementation of the fsync method for simple
967  * filesystems which track all non-inode metadata in the buffers list
968  * hanging off the address_space structure.
969  */
970 int __generic_file_fsync(struct file *file, loff_t start, loff_t end,
971                                  int datasync)
972 {
973         struct inode *inode = file->f_mapping->host;
974         int err;
975         int ret;
976 
977         err = file_write_and_wait_range(file, start, end);
978         if (err)
979                 return err;
980 
981         inode_lock(inode);
982         ret = sync_mapping_buffers(inode->i_mapping);
983         if (!(inode->i_state & I_DIRTY_ALL))
984                 goto out;
985         if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
986                 goto out;
987 
988         err = sync_inode_metadata(inode, 1);
989         if (ret == 0)
990                 ret = err;
991 
992 out:
993         inode_unlock(inode);
994         /* check and advance again to catch errors after syncing out buffers */
995         err = file_check_and_advance_wb_err(file);
996         if (ret == 0)
997                 ret = err;
998         return ret;
999 }
1000 EXPORT_SYMBOL(__generic_file_fsync);
1001 
1002 /**
1003  * generic_file_fsync - generic fsync implementation for simple filesystems
1004  *                      with flush
1005  * @file:       file to synchronize
1006  * @start:      start offset in bytes
1007  * @end:        end offset in bytes (inclusive)
1008  * @datasync:   only synchronize essential metadata if true
1009  *
1010  */
1011 
1012 int generic_file_fsync(struct file *file, loff_t start, loff_t end,
1013                        int datasync)
1014 {
1015         struct inode *inode = file->f_mapping->host;
1016         int err;
1017 
1018         err = __generic_file_fsync(file, start, end, datasync);
1019         if (err)
1020                 return err;
1021         return blkdev_issue_flush(inode->i_sb->s_bdev, GFP_KERNEL, NULL);
1022 }
1023 EXPORT_SYMBOL(generic_file_fsync);
1024 
1025 /**
1026  * generic_check_addressable - Check addressability of file system
1027  * @blocksize_bits:     log of file system block size
1028  * @num_blocks:         number of blocks in file system
1029  *
1030  * Determine whether a file system with @num_blocks blocks (and a
1031  * block size of 2**@blocksize_bits) is addressable by the sector_t
1032  * and page cache of the system.  Return 0 if so and -EFBIG otherwise.
1033  */
1034 int generic_check_addressable(unsigned blocksize_bits, u64 num_blocks)
1035 {
1036         u64 last_fs_block = num_blocks - 1;
1037         u64 last_fs_page =
1038                 last_fs_block >> (PAGE_SHIFT - blocksize_bits);
1039 
1040         if (unlikely(num_blocks == 0))
1041                 return 0;
1042 
1043         if ((blocksize_bits < 9) || (blocksize_bits > PAGE_SHIFT))
1044                 return -EINVAL;
1045 
1046         if ((last_fs_block > (sector_t)(~0ULL) >> (blocksize_bits - 9)) ||
1047             (last_fs_page > (pgoff_t)(~0ULL))) {
1048                 return -EFBIG;
1049         }
1050         return 0;
1051 }
1052 EXPORT_SYMBOL(generic_check_addressable);
1053 
1054 /*
1055  * No-op implementation of ->fsync for in-memory filesystems.
1056  */
1057 int noop_fsync(struct file *file, loff_t start, loff_t end, int datasync)
1058 {
1059         return 0;
1060 }
1061 EXPORT_SYMBOL(noop_fsync);
1062 
1063 int noop_set_page_dirty(struct page *page)
1064 {
1065         /*
1066          * Unlike __set_page_dirty_no_writeback that handles dirty page
1067          * tracking in the page object, dax does all dirty tracking in
1068          * the inode address_space in response to mkwrite faults. In the
1069          * dax case we only need to worry about potentially dirty CPU
1070          * caches, not dirty page cache pages to write back.
1071          *
1072          * This callback is defined to prevent fallback to
1073          * __set_page_dirty_buffers() in set_page_dirty().
1074          */
1075         return 0;
1076 }
1077 EXPORT_SYMBOL_GPL(noop_set_page_dirty);
1078 
1079 void noop_invalidatepage(struct page *page, unsigned int offset,
1080                 unsigned int length)
1081 {
1082         /*
1083          * There is no page cache to invalidate in the dax case, however
1084          * we need this callback defined to prevent falling back to
1085          * block_invalidatepage() in do_invalidatepage().
1086          */
1087 }
1088 EXPORT_SYMBOL_GPL(noop_invalidatepage);
1089 
1090 ssize_t noop_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
1091 {
1092         /*
1093          * iomap based filesystems support direct I/O without need for
1094          * this callback. However, it still needs to be set in
1095          * inode->a_ops so that open/fcntl know that direct I/O is
1096          * generally supported.
1097          */
1098         return -EINVAL;
1099 }
1100 EXPORT_SYMBOL_GPL(noop_direct_IO);
1101 
1102 /* Because kfree isn't assignment-compatible with void(void*) ;-/ */
1103 void kfree_link(void *p)
1104 {
1105         kfree(p);
1106 }
1107 EXPORT_SYMBOL(kfree_link);
1108 
1109 /*
1110  * nop .set_page_dirty method so that people can use .page_mkwrite on
1111  * anon inodes.
1112  */
1113 static int anon_set_page_dirty(struct page *page)
1114 {
1115         return 0;
1116 };
1117 
1118 /*
1119  * A single inode exists for all anon_inode files. Contrary to pipes,
1120  * anon_inode inodes have no associated per-instance data, so we need
1121  * only allocate one of them.
1122  */
1123 struct inode *alloc_anon_inode(struct super_block *s)
1124 {
1125         static const struct address_space_operations anon_aops = {
1126                 .set_page_dirty = anon_set_page_dirty,
1127         };
1128         struct inode *inode = new_inode_pseudo(s);
1129 
1130         if (!inode)
1131                 return ERR_PTR(-ENOMEM);
1132 
1133         inode->i_ino = get_next_ino();
1134         inode->i_mapping->a_ops = &anon_aops;
1135 
1136         /*
1137          * Mark the inode dirty from the very beginning,
1138          * that way it will never be moved to the dirty
1139          * list because mark_inode_dirty() will think
1140          * that it already _is_ on the dirty list.
1141          */
1142         inode->i_state = I_DIRTY;
1143         inode->i_mode = S_IRUSR | S_IWUSR;
1144         inode->i_uid = current_fsuid();
1145         inode->i_gid = current_fsgid();
1146         inode->i_flags |= S_PRIVATE;
1147         inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
1148         return inode;
1149 }
1150 EXPORT_SYMBOL(alloc_anon_inode);
1151 
1152 /**
1153  * simple_nosetlease - generic helper for prohibiting leases
1154  * @filp: file pointer
1155  * @arg: type of lease to obtain
1156  * @flp: new lease supplied for insertion
1157  * @priv: private data for lm_setup operation
1158  *
1159  * Generic helper for filesystems that do not wish to allow leases to be set.
1160  * All arguments are ignored and it just returns -EINVAL.
1161  */
1162 int
1163 simple_nosetlease(struct file *filp, long arg, struct file_lock **flp,
1164                   void **priv)
1165 {
1166         return -EINVAL;
1167 }
1168 EXPORT_SYMBOL(simple_nosetlease);
1169 
1170 const char *simple_get_link(struct dentry *dentry, struct inode *inode,
1171                             struct delayed_call *done)
1172 {
1173         return inode->i_link;
1174 }
1175 EXPORT_SYMBOL(simple_get_link);
1176 
1177 const struct inode_operations simple_symlink_inode_operations = {
1178         .get_link = simple_get_link,
1179 };
1180 EXPORT_SYMBOL(simple_symlink_inode_operations);
1181 
1182 /*
1183  * Operations for a permanently empty directory.
1184  */
1185 static struct dentry *empty_dir_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
1186 {
1187         return ERR_PTR(-ENOENT);
1188 }
1189 
1190 static int empty_dir_getattr(const struct path *path, struct kstat *stat,
1191                              u32 request_mask, unsigned int query_flags)
1192 {
1193         struct inode *inode = d_inode(path->dentry);
1194         generic_fillattr(inode, stat);
1195         return 0;
1196 }
1197 
1198 static int empty_dir_setattr(struct dentry *dentry, struct iattr *attr)
1199 {
1200         return -EPERM;
1201 }
1202 
1203 static ssize_t empty_dir_listxattr(struct dentry *dentry, char *list, size_t size)
1204 {
1205         return -EOPNOTSUPP;
1206 }
1207 
1208 static const struct inode_operations empty_dir_inode_operations = {
1209         .lookup         = empty_dir_lookup,
1210         .permission     = generic_permission,
1211         .setattr        = empty_dir_setattr,
1212         .getattr        = empty_dir_getattr,
1213         .listxattr      = empty_dir_listxattr,
1214 };
1215 
1216 static loff_t empty_dir_llseek(struct file *file, loff_t offset, int whence)
1217 {
1218         /* An empty directory has two entries . and .. at offsets 0 and 1 */
1219         return generic_file_llseek_size(file, offset, whence, 2, 2);
1220 }
1221 
1222 static int empty_dir_readdir(struct file *file, struct dir_context *ctx)
1223 {
1224         dir_emit_dots(file, ctx);
1225         return 0;
1226 }
1227 
1228 static const struct file_operations empty_dir_operations = {
1229         .llseek         = empty_dir_llseek,
1230         .read           = generic_read_dir,
1231         .iterate_shared = empty_dir_readdir,
1232         .fsync          = noop_fsync,
1233 };
1234 
1235 
1236 void make_empty_dir_inode(struct inode *inode)
1237 {
1238         set_nlink(inode, 2);
1239         inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO;
1240         inode->i_uid = GLOBAL_ROOT_UID;
1241         inode->i_gid = GLOBAL_ROOT_GID;
1242         inode->i_rdev = 0;
1243         inode->i_size = 0;
1244         inode->i_blkbits = PAGE_SHIFT;
1245         inode->i_blocks = 0;
1246 
1247         inode->i_op = &empty_dir_inode_operations;
1248         inode->i_opflags &= ~IOP_XATTR;
1249         inode->i_fop = &empty_dir_operations;
1250 }
1251 
1252 bool is_empty_dir_inode(struct inode *inode)
1253 {
1254         return (inode->i_fop == &empty_dir_operations) &&
1255                 (inode->i_op == &empty_dir_inode_operations);
1256 }
1257 

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