~ [ source navigation ] ~ [ diff markup ] ~ [ identifier search ] ~

TOMOYO Linux Cross Reference
Linux/fs/libfs.c

Version: ~ [ linux-5.10-rc5 ] ~ [ linux-5.9.10 ] ~ [ linux-5.8.18 ] ~ [ linux-5.7.19 ] ~ [ linux-5.6.19 ] ~ [ linux-5.5.19 ] ~ [ linux-5.4.79 ] ~ [ linux-5.3.18 ] ~ [ linux-5.2.21 ] ~ [ linux-5.1.21 ] ~ [ linux-5.0.21 ] ~ [ linux-4.20.17 ] ~ [ linux-4.19.159 ] ~ [ linux-4.18.20 ] ~ [ linux-4.17.19 ] ~ [ linux-4.16.18 ] ~ [ linux-4.15.18 ] ~ [ linux-4.14.208 ] ~ [ linux-4.13.16 ] ~ [ linux-4.12.14 ] ~ [ linux-4.11.12 ] ~ [ linux-4.10.17 ] ~ [ linux-4.9.245 ] ~ [ linux-4.8.17 ] ~ [ linux-4.7.10 ] ~ [ linux-4.6.7 ] ~ [ linux-4.5.7 ] ~ [ linux-4.4.245 ] ~ [ linux-4.3.6 ] ~ [ linux-4.2.8 ] ~ [ linux-4.1.52 ] ~ [ linux-4.0.9 ] ~ [ linux-3.19.8 ] ~ [ linux-3.18.140 ] ~ [ linux-3.17.8 ] ~ [ linux-3.16.85 ] ~ [ linux-3.15.10 ] ~ [ linux-3.14.79 ] ~ [ linux-3.13.11 ] ~ [ linux-3.12.74 ] ~ [ linux-3.11.10 ] ~ [ linux-3.10.108 ] ~ [ linux-2.6.32.71 ] ~ [ linux-2.6.0 ] ~ [ linux-2.4.37.11 ] ~ [ unix-v6-master ] ~ [ ccs-tools-1.8.5 ] ~ [ policy-sample ] ~
Architecture: ~ [ i386 ] ~ [ alpha ] ~ [ m68k ] ~ [ mips ] ~ [ ppc ] ~ [ sparc ] ~ [ sparc64 ] ~

  1 // SPDX-License-Identifier: GPL-2.0-only
  2 /*
  3  *      fs/libfs.c
  4  *      Library for filesystems writers.
  5  */
  6 
  7 #include <linux/blkdev.h>
  8 #include <linux/export.h>
  9 #include <linux/pagemap.h>
 10 #include <linux/slab.h>
 11 #include <linux/cred.h>
 12 #include <linux/mount.h>
 13 #include <linux/vfs.h>
 14 #include <linux/quotaops.h>
 15 #include <linux/mutex.h>
 16 #include <linux/namei.h>
 17 #include <linux/exportfs.h>
 18 #include <linux/writeback.h>
 19 #include <linux/buffer_head.h> /* sync_mapping_buffers */
 20 #include <linux/fs_context.h>
 21 #include <linux/pseudo_fs.h>
 22 #include <linux/fsnotify.h>
 23 #include <linux/unicode.h>
 24 #include <linux/fscrypt.h>
 25 
 26 #include <linux/uaccess.h>
 27 
 28 #include "internal.h"
 29 
 30 int simple_getattr(const struct path *path, struct kstat *stat,
 31                    u32 request_mask, unsigned int query_flags)
 32 {
 33         struct inode *inode = d_inode(path->dentry);
 34         generic_fillattr(inode, stat);
 35         stat->blocks = inode->i_mapping->nrpages << (PAGE_SHIFT - 9);
 36         return 0;
 37 }
 38 EXPORT_SYMBOL(simple_getattr);
 39 
 40 int simple_statfs(struct dentry *dentry, struct kstatfs *buf)
 41 {
 42         buf->f_type = dentry->d_sb->s_magic;
 43         buf->f_bsize = PAGE_SIZE;
 44         buf->f_namelen = NAME_MAX;
 45         return 0;
 46 }
 47 EXPORT_SYMBOL(simple_statfs);
 48 
 49 /*
 50  * Retaining negative dentries for an in-memory filesystem just wastes
 51  * memory and lookup time: arrange for them to be deleted immediately.
 52  */
 53 int always_delete_dentry(const struct dentry *dentry)
 54 {
 55         return 1;
 56 }
 57 EXPORT_SYMBOL(always_delete_dentry);
 58 
 59 const struct dentry_operations simple_dentry_operations = {
 60         .d_delete = always_delete_dentry,
 61 };
 62 EXPORT_SYMBOL(simple_dentry_operations);
 63 
 64 /*
 65  * Lookup the data. This is trivial - if the dentry didn't already
 66  * exist, we know it is negative.  Set d_op to delete negative dentries.
 67  */
 68 struct dentry *simple_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
 69 {
 70         if (dentry->d_name.len > NAME_MAX)
 71                 return ERR_PTR(-ENAMETOOLONG);
 72         if (!dentry->d_sb->s_d_op)
 73                 d_set_d_op(dentry, &simple_dentry_operations);
 74         d_add(dentry, NULL);
 75         return NULL;
 76 }
 77 EXPORT_SYMBOL(simple_lookup);
 78 
 79 int dcache_dir_open(struct inode *inode, struct file *file)
 80 {
 81         file->private_data = d_alloc_cursor(file->f_path.dentry);
 82 
 83         return file->private_data ? 0 : -ENOMEM;
 84 }
 85 EXPORT_SYMBOL(dcache_dir_open);
 86 
 87 int dcache_dir_close(struct inode *inode, struct file *file)
 88 {
 89         dput(file->private_data);
 90         return 0;
 91 }
 92 EXPORT_SYMBOL(dcache_dir_close);
 93 
 94 /* parent is locked at least shared */
 95 /*
 96  * Returns an element of siblings' list.
 97  * We are looking for <count>th positive after <p>; if
 98  * found, dentry is grabbed and returned to caller.
 99  * If no such element exists, NULL is returned.
100  */
101 static struct dentry *scan_positives(struct dentry *cursor,
102                                         struct list_head *p,
103                                         loff_t count,
104                                         struct dentry *last)
105 {
106         struct dentry *dentry = cursor->d_parent, *found = NULL;
107 
108         spin_lock(&dentry->d_lock);
109         while ((p = p->next) != &dentry->d_subdirs) {
110                 struct dentry *d = list_entry(p, struct dentry, d_child);
111                 // we must at least skip cursors, to avoid livelocks
112                 if (d->d_flags & DCACHE_DENTRY_CURSOR)
113                         continue;
114                 if (simple_positive(d) && !--count) {
115                         spin_lock_nested(&d->d_lock, DENTRY_D_LOCK_NESTED);
116                         if (simple_positive(d))
117                                 found = dget_dlock(d);
118                         spin_unlock(&d->d_lock);
119                         if (likely(found))
120                                 break;
121                         count = 1;
122                 }
123                 if (need_resched()) {
124                         list_move(&cursor->d_child, p);
125                         p = &cursor->d_child;
126                         spin_unlock(&dentry->d_lock);
127                         cond_resched();
128                         spin_lock(&dentry->d_lock);
129                 }
130         }
131         spin_unlock(&dentry->d_lock);
132         dput(last);
133         return found;
134 }
135 
136 loff_t dcache_dir_lseek(struct file *file, loff_t offset, int whence)
137 {
138         struct dentry *dentry = file->f_path.dentry;
139         switch (whence) {
140                 case 1:
141                         offset += file->f_pos;
142                         fallthrough;
143                 case 0:
144                         if (offset >= 0)
145                                 break;
146                         fallthrough;
147                 default:
148                         return -EINVAL;
149         }
150         if (offset != file->f_pos) {
151                 struct dentry *cursor = file->private_data;
152                 struct dentry *to = NULL;
153 
154                 inode_lock_shared(dentry->d_inode);
155 
156                 if (offset > 2)
157                         to = scan_positives(cursor, &dentry->d_subdirs,
158                                             offset - 2, NULL);
159                 spin_lock(&dentry->d_lock);
160                 if (to)
161                         list_move(&cursor->d_child, &to->d_child);
162                 else
163                         list_del_init(&cursor->d_child);
164                 spin_unlock(&dentry->d_lock);
165                 dput(to);
166 
167                 file->f_pos = offset;
168 
169                 inode_unlock_shared(dentry->d_inode);
170         }
171         return offset;
172 }
173 EXPORT_SYMBOL(dcache_dir_lseek);
174 
175 /* Relationship between i_mode and the DT_xxx types */
176 static inline unsigned char dt_type(struct inode *inode)
177 {
178         return (inode->i_mode >> 12) & 15;
179 }
180 
181 /*
182  * Directory is locked and all positive dentries in it are safe, since
183  * for ramfs-type trees they can't go away without unlink() or rmdir(),
184  * both impossible due to the lock on directory.
185  */
186 
187 int dcache_readdir(struct file *file, struct dir_context *ctx)
188 {
189         struct dentry *dentry = file->f_path.dentry;
190         struct dentry *cursor = file->private_data;
191         struct list_head *anchor = &dentry->d_subdirs;
192         struct dentry *next = NULL;
193         struct list_head *p;
194 
195         if (!dir_emit_dots(file, ctx))
196                 return 0;
197 
198         if (ctx->pos == 2)
199                 p = anchor;
200         else if (!list_empty(&cursor->d_child))
201                 p = &cursor->d_child;
202         else
203                 return 0;
204 
205         while ((next = scan_positives(cursor, p, 1, next)) != NULL) {
206                 if (!dir_emit(ctx, next->d_name.name, next->d_name.len,
207                               d_inode(next)->i_ino, dt_type(d_inode(next))))
208                         break;
209                 ctx->pos++;
210                 p = &next->d_child;
211         }
212         spin_lock(&dentry->d_lock);
213         if (next)
214                 list_move_tail(&cursor->d_child, &next->d_child);
215         else
216                 list_del_init(&cursor->d_child);
217         spin_unlock(&dentry->d_lock);
218         dput(next);
219 
220         return 0;
221 }
222 EXPORT_SYMBOL(dcache_readdir);
223 
224 ssize_t generic_read_dir(struct file *filp, char __user *buf, size_t siz, loff_t *ppos)
225 {
226         return -EISDIR;
227 }
228 EXPORT_SYMBOL(generic_read_dir);
229 
230 const struct file_operations simple_dir_operations = {
231         .open           = dcache_dir_open,
232         .release        = dcache_dir_close,
233         .llseek         = dcache_dir_lseek,
234         .read           = generic_read_dir,
235         .iterate_shared = dcache_readdir,
236         .fsync          = noop_fsync,
237 };
238 EXPORT_SYMBOL(simple_dir_operations);
239 
240 const struct inode_operations simple_dir_inode_operations = {
241         .lookup         = simple_lookup,
242 };
243 EXPORT_SYMBOL(simple_dir_inode_operations);
244 
245 static struct dentry *find_next_child(struct dentry *parent, struct dentry *prev)
246 {
247         struct dentry *child = NULL;
248         struct list_head *p = prev ? &prev->d_child : &parent->d_subdirs;
249 
250         spin_lock(&parent->d_lock);
251         while ((p = p->next) != &parent->d_subdirs) {
252                 struct dentry *d = container_of(p, struct dentry, d_child);
253                 if (simple_positive(d)) {
254                         spin_lock_nested(&d->d_lock, DENTRY_D_LOCK_NESTED);
255                         if (simple_positive(d))
256                                 child = dget_dlock(d);
257                         spin_unlock(&d->d_lock);
258                         if (likely(child))
259                                 break;
260                 }
261         }
262         spin_unlock(&parent->d_lock);
263         dput(prev);
264         return child;
265 }
266 
267 void simple_recursive_removal(struct dentry *dentry,
268                               void (*callback)(struct dentry *))
269 {
270         struct dentry *this = dget(dentry);
271         while (true) {
272                 struct dentry *victim = NULL, *child;
273                 struct inode *inode = this->d_inode;
274 
275                 inode_lock(inode);
276                 if (d_is_dir(this))
277                         inode->i_flags |= S_DEAD;
278                 while ((child = find_next_child(this, victim)) == NULL) {
279                         // kill and ascend
280                         // update metadata while it's still locked
281                         inode->i_ctime = current_time(inode);
282                         clear_nlink(inode);
283                         inode_unlock(inode);
284                         victim = this;
285                         this = this->d_parent;
286                         inode = this->d_inode;
287                         inode_lock(inode);
288                         if (simple_positive(victim)) {
289                                 d_invalidate(victim);   // avoid lost mounts
290                                 if (d_is_dir(victim))
291                                         fsnotify_rmdir(inode, victim);
292                                 else
293                                         fsnotify_unlink(inode, victim);
294                                 if (callback)
295                                         callback(victim);
296                                 dput(victim);           // unpin it
297                         }
298                         if (victim == dentry) {
299                                 inode->i_ctime = inode->i_mtime =
300                                         current_time(inode);
301                                 if (d_is_dir(dentry))
302                                         drop_nlink(inode);
303                                 inode_unlock(inode);
304                                 dput(dentry);
305                                 return;
306                         }
307                 }
308                 inode_unlock(inode);
309                 this = child;
310         }
311 }
312 EXPORT_SYMBOL(simple_recursive_removal);
313 
314 static const struct super_operations simple_super_operations = {
315         .statfs         = simple_statfs,
316 };
317 
318 static int pseudo_fs_fill_super(struct super_block *s, struct fs_context *fc)
319 {
320         struct pseudo_fs_context *ctx = fc->fs_private;
321         struct inode *root;
322 
323         s->s_maxbytes = MAX_LFS_FILESIZE;
324         s->s_blocksize = PAGE_SIZE;
325         s->s_blocksize_bits = PAGE_SHIFT;
326         s->s_magic = ctx->magic;
327         s->s_op = ctx->ops ?: &simple_super_operations;
328         s->s_xattr = ctx->xattr;
329         s->s_time_gran = 1;
330         root = new_inode(s);
331         if (!root)
332                 return -ENOMEM;
333 
334         /*
335          * since this is the first inode, make it number 1. New inodes created
336          * after this must take care not to collide with it (by passing
337          * max_reserved of 1 to iunique).
338          */
339         root->i_ino = 1;
340         root->i_mode = S_IFDIR | S_IRUSR | S_IWUSR;
341         root->i_atime = root->i_mtime = root->i_ctime = current_time(root);
342         s->s_root = d_make_root(root);
343         if (!s->s_root)
344                 return -ENOMEM;
345         s->s_d_op = ctx->dops;
346         return 0;
347 }
348 
349 static int pseudo_fs_get_tree(struct fs_context *fc)
350 {
351         return get_tree_nodev(fc, pseudo_fs_fill_super);
352 }
353 
354 static void pseudo_fs_free(struct fs_context *fc)
355 {
356         kfree(fc->fs_private);
357 }
358 
359 static const struct fs_context_operations pseudo_fs_context_ops = {
360         .free           = pseudo_fs_free,
361         .get_tree       = pseudo_fs_get_tree,
362 };
363 
364 /*
365  * Common helper for pseudo-filesystems (sockfs, pipefs, bdev - stuff that
366  * will never be mountable)
367  */
368 struct pseudo_fs_context *init_pseudo(struct fs_context *fc,
369                                         unsigned long magic)
370 {
371         struct pseudo_fs_context *ctx;
372 
373         ctx = kzalloc(sizeof(struct pseudo_fs_context), GFP_KERNEL);
374         if (likely(ctx)) {
375                 ctx->magic = magic;
376                 fc->fs_private = ctx;
377                 fc->ops = &pseudo_fs_context_ops;
378                 fc->sb_flags |= SB_NOUSER;
379                 fc->global = true;
380         }
381         return ctx;
382 }
383 EXPORT_SYMBOL(init_pseudo);
384 
385 int simple_open(struct inode *inode, struct file *file)
386 {
387         if (inode->i_private)
388                 file->private_data = inode->i_private;
389         return 0;
390 }
391 EXPORT_SYMBOL(simple_open);
392 
393 int simple_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
394 {
395         struct inode *inode = d_inode(old_dentry);
396 
397         inode->i_ctime = dir->i_ctime = dir->i_mtime = current_time(inode);
398         inc_nlink(inode);
399         ihold(inode);
400         dget(dentry);
401         d_instantiate(dentry, inode);
402         return 0;
403 }
404 EXPORT_SYMBOL(simple_link);
405 
406 int simple_empty(struct dentry *dentry)
407 {
408         struct dentry *child;
409         int ret = 0;
410 
411         spin_lock(&dentry->d_lock);
412         list_for_each_entry(child, &dentry->d_subdirs, d_child) {
413                 spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED);
414                 if (simple_positive(child)) {
415                         spin_unlock(&child->d_lock);
416                         goto out;
417                 }
418                 spin_unlock(&child->d_lock);
419         }
420         ret = 1;
421 out:
422         spin_unlock(&dentry->d_lock);
423         return ret;
424 }
425 EXPORT_SYMBOL(simple_empty);
426 
427 int simple_unlink(struct inode *dir, struct dentry *dentry)
428 {
429         struct inode *inode = d_inode(dentry);
430 
431         inode->i_ctime = dir->i_ctime = dir->i_mtime = current_time(inode);
432         drop_nlink(inode);
433         dput(dentry);
434         return 0;
435 }
436 EXPORT_SYMBOL(simple_unlink);
437 
438 int simple_rmdir(struct inode *dir, struct dentry *dentry)
439 {
440         if (!simple_empty(dentry))
441                 return -ENOTEMPTY;
442 
443         drop_nlink(d_inode(dentry));
444         simple_unlink(dir, dentry);
445         drop_nlink(dir);
446         return 0;
447 }
448 EXPORT_SYMBOL(simple_rmdir);
449 
450 int simple_rename(struct inode *old_dir, struct dentry *old_dentry,
451                   struct inode *new_dir, struct dentry *new_dentry,
452                   unsigned int flags)
453 {
454         struct inode *inode = d_inode(old_dentry);
455         int they_are_dirs = d_is_dir(old_dentry);
456 
457         if (flags & ~RENAME_NOREPLACE)
458                 return -EINVAL;
459 
460         if (!simple_empty(new_dentry))
461                 return -ENOTEMPTY;
462 
463         if (d_really_is_positive(new_dentry)) {
464                 simple_unlink(new_dir, new_dentry);
465                 if (they_are_dirs) {
466                         drop_nlink(d_inode(new_dentry));
467                         drop_nlink(old_dir);
468                 }
469         } else if (they_are_dirs) {
470                 drop_nlink(old_dir);
471                 inc_nlink(new_dir);
472         }
473 
474         old_dir->i_ctime = old_dir->i_mtime = new_dir->i_ctime =
475                 new_dir->i_mtime = inode->i_ctime = current_time(old_dir);
476 
477         return 0;
478 }
479 EXPORT_SYMBOL(simple_rename);
480 
481 /**
482  * simple_setattr - setattr for simple filesystem
483  * @dentry: dentry
484  * @iattr: iattr structure
485  *
486  * Returns 0 on success, -error on failure.
487  *
488  * simple_setattr is a simple ->setattr implementation without a proper
489  * implementation of size changes.
490  *
491  * It can either be used for in-memory filesystems or special files
492  * on simple regular filesystems.  Anything that needs to change on-disk
493  * or wire state on size changes needs its own setattr method.
494  */
495 int simple_setattr(struct dentry *dentry, struct iattr *iattr)
496 {
497         struct inode *inode = d_inode(dentry);
498         int error;
499 
500         error = setattr_prepare(dentry, iattr);
501         if (error)
502                 return error;
503 
504         if (iattr->ia_valid & ATTR_SIZE)
505                 truncate_setsize(inode, iattr->ia_size);
506         setattr_copy(inode, iattr);
507         mark_inode_dirty(inode);
508         return 0;
509 }
510 EXPORT_SYMBOL(simple_setattr);
511 
512 int simple_readpage(struct file *file, struct page *page)
513 {
514         clear_highpage(page);
515         flush_dcache_page(page);
516         SetPageUptodate(page);
517         unlock_page(page);
518         return 0;
519 }
520 EXPORT_SYMBOL(simple_readpage);
521 
522 int simple_write_begin(struct file *file, struct address_space *mapping,
523                         loff_t pos, unsigned len, unsigned flags,
524                         struct page **pagep, void **fsdata)
525 {
526         struct page *page;
527         pgoff_t index;
528 
529         index = pos >> PAGE_SHIFT;
530 
531         page = grab_cache_page_write_begin(mapping, index, flags);
532         if (!page)
533                 return -ENOMEM;
534 
535         *pagep = page;
536 
537         if (!PageUptodate(page) && (len != PAGE_SIZE)) {
538                 unsigned from = pos & (PAGE_SIZE - 1);
539 
540                 zero_user_segments(page, 0, from, from + len, PAGE_SIZE);
541         }
542         return 0;
543 }
544 EXPORT_SYMBOL(simple_write_begin);
545 
546 /**
547  * simple_write_end - .write_end helper for non-block-device FSes
548  * @file: See .write_end of address_space_operations
549  * @mapping:            "
550  * @pos:                "
551  * @len:                "
552  * @copied:             "
553  * @page:               "
554  * @fsdata:             "
555  *
556  * simple_write_end does the minimum needed for updating a page after writing is
557  * done. It has the same API signature as the .write_end of
558  * address_space_operations vector. So it can just be set onto .write_end for
559  * FSes that don't need any other processing. i_mutex is assumed to be held.
560  * Block based filesystems should use generic_write_end().
561  * NOTE: Even though i_size might get updated by this function, mark_inode_dirty
562  * is not called, so a filesystem that actually does store data in .write_inode
563  * should extend on what's done here with a call to mark_inode_dirty() in the
564  * case that i_size has changed.
565  *
566  * Use *ONLY* with simple_readpage()
567  */
568 int simple_write_end(struct file *file, struct address_space *mapping,
569                         loff_t pos, unsigned len, unsigned copied,
570                         struct page *page, void *fsdata)
571 {
572         struct inode *inode = page->mapping->host;
573         loff_t last_pos = pos + copied;
574 
575         /* zero the stale part of the page if we did a short copy */
576         if (!PageUptodate(page)) {
577                 if (copied < len) {
578                         unsigned from = pos & (PAGE_SIZE - 1);
579 
580                         zero_user(page, from + copied, len - copied);
581                 }
582                 SetPageUptodate(page);
583         }
584         /*
585          * No need to use i_size_read() here, the i_size
586          * cannot change under us because we hold the i_mutex.
587          */
588         if (last_pos > inode->i_size)
589                 i_size_write(inode, last_pos);
590 
591         set_page_dirty(page);
592         unlock_page(page);
593         put_page(page);
594 
595         return copied;
596 }
597 EXPORT_SYMBOL(simple_write_end);
598 
599 /*
600  * the inodes created here are not hashed. If you use iunique to generate
601  * unique inode values later for this filesystem, then you must take care
602  * to pass it an appropriate max_reserved value to avoid collisions.
603  */
604 int simple_fill_super(struct super_block *s, unsigned long magic,
605                       const struct tree_descr *files)
606 {
607         struct inode *inode;
608         struct dentry *root;
609         struct dentry *dentry;
610         int i;
611 
612         s->s_blocksize = PAGE_SIZE;
613         s->s_blocksize_bits = PAGE_SHIFT;
614         s->s_magic = magic;
615         s->s_op = &simple_super_operations;
616         s->s_time_gran = 1;
617 
618         inode = new_inode(s);
619         if (!inode)
620                 return -ENOMEM;
621         /*
622          * because the root inode is 1, the files array must not contain an
623          * entry at index 1
624          */
625         inode->i_ino = 1;
626         inode->i_mode = S_IFDIR | 0755;
627         inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
628         inode->i_op = &simple_dir_inode_operations;
629         inode->i_fop = &simple_dir_operations;
630         set_nlink(inode, 2);
631         root = d_make_root(inode);
632         if (!root)
633                 return -ENOMEM;
634         for (i = 0; !files->name || files->name[0]; i++, files++) {
635                 if (!files->name)
636                         continue;
637 
638                 /* warn if it tries to conflict with the root inode */
639                 if (unlikely(i == 1))
640                         printk(KERN_WARNING "%s: %s passed in a files array"
641                                 "with an index of 1!\n", __func__,
642                                 s->s_type->name);
643 
644                 dentry = d_alloc_name(root, files->name);
645                 if (!dentry)
646                         goto out;
647                 inode = new_inode(s);
648                 if (!inode) {
649                         dput(dentry);
650                         goto out;
651                 }
652                 inode->i_mode = S_IFREG | files->mode;
653                 inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
654                 inode->i_fop = files->ops;
655                 inode->i_ino = i;
656                 d_add(dentry, inode);
657         }
658         s->s_root = root;
659         return 0;
660 out:
661         d_genocide(root);
662         shrink_dcache_parent(root);
663         dput(root);
664         return -ENOMEM;
665 }
666 EXPORT_SYMBOL(simple_fill_super);
667 
668 static DEFINE_SPINLOCK(pin_fs_lock);
669 
670 int simple_pin_fs(struct file_system_type *type, struct vfsmount **mount, int *count)
671 {
672         struct vfsmount *mnt = NULL;
673         spin_lock(&pin_fs_lock);
674         if (unlikely(!*mount)) {
675                 spin_unlock(&pin_fs_lock);
676                 mnt = vfs_kern_mount(type, SB_KERNMOUNT, type->name, NULL);
677                 if (IS_ERR(mnt))
678                         return PTR_ERR(mnt);
679                 spin_lock(&pin_fs_lock);
680                 if (!*mount)
681                         *mount = mnt;
682         }
683         mntget(*mount);
684         ++*count;
685         spin_unlock(&pin_fs_lock);
686         mntput(mnt);
687         return 0;
688 }
689 EXPORT_SYMBOL(simple_pin_fs);
690 
691 void simple_release_fs(struct vfsmount **mount, int *count)
692 {
693         struct vfsmount *mnt;
694         spin_lock(&pin_fs_lock);
695         mnt = *mount;
696         if (!--*count)
697                 *mount = NULL;
698         spin_unlock(&pin_fs_lock);
699         mntput(mnt);
700 }
701 EXPORT_SYMBOL(simple_release_fs);
702 
703 /**
704  * simple_read_from_buffer - copy data from the buffer to user space
705  * @to: the user space buffer to read to
706  * @count: the maximum number of bytes to read
707  * @ppos: the current position in the buffer
708  * @from: the buffer to read from
709  * @available: the size of the buffer
710  *
711  * The simple_read_from_buffer() function reads up to @count bytes from the
712  * buffer @from at offset @ppos into the user space address starting at @to.
713  *
714  * On success, the number of bytes read is returned and the offset @ppos is
715  * advanced by this number, or negative value is returned on error.
716  **/
717 ssize_t simple_read_from_buffer(void __user *to, size_t count, loff_t *ppos,
718                                 const void *from, size_t available)
719 {
720         loff_t pos = *ppos;
721         size_t ret;
722 
723         if (pos < 0)
724                 return -EINVAL;
725         if (pos >= available || !count)
726                 return 0;
727         if (count > available - pos)
728                 count = available - pos;
729         ret = copy_to_user(to, from + pos, count);
730         if (ret == count)
731                 return -EFAULT;
732         count -= ret;
733         *ppos = pos + count;
734         return count;
735 }
736 EXPORT_SYMBOL(simple_read_from_buffer);
737 
738 /**
739  * simple_write_to_buffer - copy data from user space to the buffer
740  * @to: the buffer to write to
741  * @available: the size of the buffer
742  * @ppos: the current position in the buffer
743  * @from: the user space buffer to read from
744  * @count: the maximum number of bytes to read
745  *
746  * The simple_write_to_buffer() function reads up to @count bytes from the user
747  * space address starting at @from into the buffer @to at offset @ppos.
748  *
749  * On success, the number of bytes written is returned and the offset @ppos is
750  * advanced by this number, or negative value is returned on error.
751  **/
752 ssize_t simple_write_to_buffer(void *to, size_t available, loff_t *ppos,
753                 const void __user *from, size_t count)
754 {
755         loff_t pos = *ppos;
756         size_t res;
757 
758         if (pos < 0)
759                 return -EINVAL;
760         if (pos >= available || !count)
761                 return 0;
762         if (count > available - pos)
763                 count = available - pos;
764         res = copy_from_user(to + pos, from, count);
765         if (res == count)
766                 return -EFAULT;
767         count -= res;
768         *ppos = pos + count;
769         return count;
770 }
771 EXPORT_SYMBOL(simple_write_to_buffer);
772 
773 /**
774  * memory_read_from_buffer - copy data from the buffer
775  * @to: the kernel space buffer to read to
776  * @count: the maximum number of bytes to read
777  * @ppos: the current position in the buffer
778  * @from: the buffer to read from
779  * @available: the size of the buffer
780  *
781  * The memory_read_from_buffer() function reads up to @count bytes from the
782  * buffer @from at offset @ppos into the kernel space address starting at @to.
783  *
784  * On success, the number of bytes read is returned and the offset @ppos is
785  * advanced by this number, or negative value is returned on error.
786  **/
787 ssize_t memory_read_from_buffer(void *to, size_t count, loff_t *ppos,
788                                 const void *from, size_t available)
789 {
790         loff_t pos = *ppos;
791 
792         if (pos < 0)
793                 return -EINVAL;
794         if (pos >= available)
795                 return 0;
796         if (count > available - pos)
797                 count = available - pos;
798         memcpy(to, from + pos, count);
799         *ppos = pos + count;
800 
801         return count;
802 }
803 EXPORT_SYMBOL(memory_read_from_buffer);
804 
805 /*
806  * Transaction based IO.
807  * The file expects a single write which triggers the transaction, and then
808  * possibly a read which collects the result - which is stored in a
809  * file-local buffer.
810  */
811 
812 void simple_transaction_set(struct file *file, size_t n)
813 {
814         struct simple_transaction_argresp *ar = file->private_data;
815 
816         BUG_ON(n > SIMPLE_TRANSACTION_LIMIT);
817 
818         /*
819          * The barrier ensures that ar->size will really remain zero until
820          * ar->data is ready for reading.
821          */
822         smp_mb();
823         ar->size = n;
824 }
825 EXPORT_SYMBOL(simple_transaction_set);
826 
827 char *simple_transaction_get(struct file *file, const char __user *buf, size_t size)
828 {
829         struct simple_transaction_argresp *ar;
830         static DEFINE_SPINLOCK(simple_transaction_lock);
831 
832         if (size > SIMPLE_TRANSACTION_LIMIT - 1)
833                 return ERR_PTR(-EFBIG);
834 
835         ar = (struct simple_transaction_argresp *)get_zeroed_page(GFP_KERNEL);
836         if (!ar)
837                 return ERR_PTR(-ENOMEM);
838 
839         spin_lock(&simple_transaction_lock);
840 
841         /* only one write allowed per open */
842         if (file->private_data) {
843                 spin_unlock(&simple_transaction_lock);
844                 free_page((unsigned long)ar);
845                 return ERR_PTR(-EBUSY);
846         }
847 
848         file->private_data = ar;
849 
850         spin_unlock(&simple_transaction_lock);
851 
852         if (copy_from_user(ar->data, buf, size))
853                 return ERR_PTR(-EFAULT);
854 
855         return ar->data;
856 }
857 EXPORT_SYMBOL(simple_transaction_get);
858 
859 ssize_t simple_transaction_read(struct file *file, char __user *buf, size_t size, loff_t *pos)
860 {
861         struct simple_transaction_argresp *ar = file->private_data;
862 
863         if (!ar)
864                 return 0;
865         return simple_read_from_buffer(buf, size, pos, ar->data, ar->size);
866 }
867 EXPORT_SYMBOL(simple_transaction_read);
868 
869 int simple_transaction_release(struct inode *inode, struct file *file)
870 {
871         free_page((unsigned long)file->private_data);
872         return 0;
873 }
874 EXPORT_SYMBOL(simple_transaction_release);
875 
876 /* Simple attribute files */
877 
878 struct simple_attr {
879         int (*get)(void *, u64 *);
880         int (*set)(void *, u64);
881         char get_buf[24];       /* enough to store a u64 and "\n\0" */
882         char set_buf[24];
883         void *data;
884         const char *fmt;        /* format for read operation */
885         struct mutex mutex;     /* protects access to these buffers */
886 };
887 
888 /* simple_attr_open is called by an actual attribute open file operation
889  * to set the attribute specific access operations. */
890 int simple_attr_open(struct inode *inode, struct file *file,
891                      int (*get)(void *, u64 *), int (*set)(void *, u64),
892                      const char *fmt)
893 {
894         struct simple_attr *attr;
895 
896         attr = kzalloc(sizeof(*attr), GFP_KERNEL);
897         if (!attr)
898                 return -ENOMEM;
899 
900         attr->get = get;
901         attr->set = set;
902         attr->data = inode->i_private;
903         attr->fmt = fmt;
904         mutex_init(&attr->mutex);
905 
906         file->private_data = attr;
907 
908         return nonseekable_open(inode, file);
909 }
910 EXPORT_SYMBOL_GPL(simple_attr_open);
911 
912 int simple_attr_release(struct inode *inode, struct file *file)
913 {
914         kfree(file->private_data);
915         return 0;
916 }
917 EXPORT_SYMBOL_GPL(simple_attr_release); /* GPL-only?  This?  Really? */
918 
919 /* read from the buffer that is filled with the get function */
920 ssize_t simple_attr_read(struct file *file, char __user *buf,
921                          size_t len, loff_t *ppos)
922 {
923         struct simple_attr *attr;
924         size_t size;
925         ssize_t ret;
926 
927         attr = file->private_data;
928 
929         if (!attr->get)
930                 return -EACCES;
931 
932         ret = mutex_lock_interruptible(&attr->mutex);
933         if (ret)
934                 return ret;
935 
936         if (*ppos && attr->get_buf[0]) {
937                 /* continued read */
938                 size = strlen(attr->get_buf);
939         } else {
940                 /* first read */
941                 u64 val;
942                 ret = attr->get(attr->data, &val);
943                 if (ret)
944                         goto out;
945 
946                 size = scnprintf(attr->get_buf, sizeof(attr->get_buf),
947                                  attr->fmt, (unsigned long long)val);
948         }
949 
950         ret = simple_read_from_buffer(buf, len, ppos, attr->get_buf, size);
951 out:
952         mutex_unlock(&attr->mutex);
953         return ret;
954 }
955 EXPORT_SYMBOL_GPL(simple_attr_read);
956 
957 /* interpret the buffer as a number to call the set function with */
958 ssize_t simple_attr_write(struct file *file, const char __user *buf,
959                           size_t len, loff_t *ppos)
960 {
961         struct simple_attr *attr;
962         unsigned long long val;
963         size_t size;
964         ssize_t ret;
965 
966         attr = file->private_data;
967         if (!attr->set)
968                 return -EACCES;
969 
970         ret = mutex_lock_interruptible(&attr->mutex);
971         if (ret)
972                 return ret;
973 
974         ret = -EFAULT;
975         size = min(sizeof(attr->set_buf) - 1, len);
976         if (copy_from_user(attr->set_buf, buf, size))
977                 goto out;
978 
979         attr->set_buf[size] = '\0';
980         ret = kstrtoull(attr->set_buf, 0, &val);
981         if (ret)
982                 goto out;
983         ret = attr->set(attr->data, val);
984         if (ret == 0)
985                 ret = len; /* on success, claim we got the whole input */
986 out:
987         mutex_unlock(&attr->mutex);
988         return ret;
989 }
990 EXPORT_SYMBOL_GPL(simple_attr_write);
991 
992 /**
993  * generic_fh_to_dentry - generic helper for the fh_to_dentry export operation
994  * @sb:         filesystem to do the file handle conversion on
995  * @fid:        file handle to convert
996  * @fh_len:     length of the file handle in bytes
997  * @fh_type:    type of file handle
998  * @get_inode:  filesystem callback to retrieve inode
999  *
1000  * This function decodes @fid as long as it has one of the well-known
1001  * Linux filehandle types and calls @get_inode on it to retrieve the
1002  * inode for the object specified in the file handle.
1003  */
1004 struct dentry *generic_fh_to_dentry(struct super_block *sb, struct fid *fid,
1005                 int fh_len, int fh_type, struct inode *(*get_inode)
1006                         (struct super_block *sb, u64 ino, u32 gen))
1007 {
1008         struct inode *inode = NULL;
1009 
1010         if (fh_len < 2)
1011                 return NULL;
1012 
1013         switch (fh_type) {
1014         case FILEID_INO32_GEN:
1015         case FILEID_INO32_GEN_PARENT:
1016                 inode = get_inode(sb, fid->i32.ino, fid->i32.gen);
1017                 break;
1018         }
1019 
1020         return d_obtain_alias(inode);
1021 }
1022 EXPORT_SYMBOL_GPL(generic_fh_to_dentry);
1023 
1024 /**
1025  * generic_fh_to_parent - generic helper for the fh_to_parent export operation
1026  * @sb:         filesystem to do the file handle conversion on
1027  * @fid:        file handle to convert
1028  * @fh_len:     length of the file handle in bytes
1029  * @fh_type:    type of file handle
1030  * @get_inode:  filesystem callback to retrieve inode
1031  *
1032  * This function decodes @fid as long as it has one of the well-known
1033  * Linux filehandle types and calls @get_inode on it to retrieve the
1034  * inode for the _parent_ object specified in the file handle if it
1035  * is specified in the file handle, or NULL otherwise.
1036  */
1037 struct dentry *generic_fh_to_parent(struct super_block *sb, struct fid *fid,
1038                 int fh_len, int fh_type, struct inode *(*get_inode)
1039                         (struct super_block *sb, u64 ino, u32 gen))
1040 {
1041         struct inode *inode = NULL;
1042 
1043         if (fh_len <= 2)
1044                 return NULL;
1045 
1046         switch (fh_type) {
1047         case FILEID_INO32_GEN_PARENT:
1048                 inode = get_inode(sb, fid->i32.parent_ino,
1049                                   (fh_len > 3 ? fid->i32.parent_gen : 0));
1050                 break;
1051         }
1052 
1053         return d_obtain_alias(inode);
1054 }
1055 EXPORT_SYMBOL_GPL(generic_fh_to_parent);
1056 
1057 /**
1058  * __generic_file_fsync - generic fsync implementation for simple filesystems
1059  *
1060  * @file:       file to synchronize
1061  * @start:      start offset in bytes
1062  * @end:        end offset in bytes (inclusive)
1063  * @datasync:   only synchronize essential metadata if true
1064  *
1065  * This is a generic implementation of the fsync method for simple
1066  * filesystems which track all non-inode metadata in the buffers list
1067  * hanging off the address_space structure.
1068  */
1069 int __generic_file_fsync(struct file *file, loff_t start, loff_t end,
1070                                  int datasync)
1071 {
1072         struct inode *inode = file->f_mapping->host;
1073         int err;
1074         int ret;
1075 
1076         err = file_write_and_wait_range(file, start, end);
1077         if (err)
1078                 return err;
1079 
1080         inode_lock(inode);
1081         ret = sync_mapping_buffers(inode->i_mapping);
1082         if (!(inode->i_state & I_DIRTY_ALL))
1083                 goto out;
1084         if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
1085                 goto out;
1086 
1087         err = sync_inode_metadata(inode, 1);
1088         if (ret == 0)
1089                 ret = err;
1090 
1091 out:
1092         inode_unlock(inode);
1093         /* check and advance again to catch errors after syncing out buffers */
1094         err = file_check_and_advance_wb_err(file);
1095         if (ret == 0)
1096                 ret = err;
1097         return ret;
1098 }
1099 EXPORT_SYMBOL(__generic_file_fsync);
1100 
1101 /**
1102  * generic_file_fsync - generic fsync implementation for simple filesystems
1103  *                      with flush
1104  * @file:       file to synchronize
1105  * @start:      start offset in bytes
1106  * @end:        end offset in bytes (inclusive)
1107  * @datasync:   only synchronize essential metadata if true
1108  *
1109  */
1110 
1111 int generic_file_fsync(struct file *file, loff_t start, loff_t end,
1112                        int datasync)
1113 {
1114         struct inode *inode = file->f_mapping->host;
1115         int err;
1116 
1117         err = __generic_file_fsync(file, start, end, datasync);
1118         if (err)
1119                 return err;
1120         return blkdev_issue_flush(inode->i_sb->s_bdev, GFP_KERNEL);
1121 }
1122 EXPORT_SYMBOL(generic_file_fsync);
1123 
1124 /**
1125  * generic_check_addressable - Check addressability of file system
1126  * @blocksize_bits:     log of file system block size
1127  * @num_blocks:         number of blocks in file system
1128  *
1129  * Determine whether a file system with @num_blocks blocks (and a
1130  * block size of 2**@blocksize_bits) is addressable by the sector_t
1131  * and page cache of the system.  Return 0 if so and -EFBIG otherwise.
1132  */
1133 int generic_check_addressable(unsigned blocksize_bits, u64 num_blocks)
1134 {
1135         u64 last_fs_block = num_blocks - 1;
1136         u64 last_fs_page =
1137                 last_fs_block >> (PAGE_SHIFT - blocksize_bits);
1138 
1139         if (unlikely(num_blocks == 0))
1140                 return 0;
1141 
1142         if ((blocksize_bits < 9) || (blocksize_bits > PAGE_SHIFT))
1143                 return -EINVAL;
1144 
1145         if ((last_fs_block > (sector_t)(~0ULL) >> (blocksize_bits - 9)) ||
1146             (last_fs_page > (pgoff_t)(~0ULL))) {
1147                 return -EFBIG;
1148         }
1149         return 0;
1150 }
1151 EXPORT_SYMBOL(generic_check_addressable);
1152 
1153 /*
1154  * No-op implementation of ->fsync for in-memory filesystems.
1155  */
1156 int noop_fsync(struct file *file, loff_t start, loff_t end, int datasync)
1157 {
1158         return 0;
1159 }
1160 EXPORT_SYMBOL(noop_fsync);
1161 
1162 int noop_set_page_dirty(struct page *page)
1163 {
1164         /*
1165          * Unlike __set_page_dirty_no_writeback that handles dirty page
1166          * tracking in the page object, dax does all dirty tracking in
1167          * the inode address_space in response to mkwrite faults. In the
1168          * dax case we only need to worry about potentially dirty CPU
1169          * caches, not dirty page cache pages to write back.
1170          *
1171          * This callback is defined to prevent fallback to
1172          * __set_page_dirty_buffers() in set_page_dirty().
1173          */
1174         return 0;
1175 }
1176 EXPORT_SYMBOL_GPL(noop_set_page_dirty);
1177 
1178 void noop_invalidatepage(struct page *page, unsigned int offset,
1179                 unsigned int length)
1180 {
1181         /*
1182          * There is no page cache to invalidate in the dax case, however
1183          * we need this callback defined to prevent falling back to
1184          * block_invalidatepage() in do_invalidatepage().
1185          */
1186 }
1187 EXPORT_SYMBOL_GPL(noop_invalidatepage);
1188 
1189 ssize_t noop_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
1190 {
1191         /*
1192          * iomap based filesystems support direct I/O without need for
1193          * this callback. However, it still needs to be set in
1194          * inode->a_ops so that open/fcntl know that direct I/O is
1195          * generally supported.
1196          */
1197         return -EINVAL;
1198 }
1199 EXPORT_SYMBOL_GPL(noop_direct_IO);
1200 
1201 /* Because kfree isn't assignment-compatible with void(void*) ;-/ */
1202 void kfree_link(void *p)
1203 {
1204         kfree(p);
1205 }
1206 EXPORT_SYMBOL(kfree_link);
1207 
1208 /*
1209  * nop .set_page_dirty method so that people can use .page_mkwrite on
1210  * anon inodes.
1211  */
1212 static int anon_set_page_dirty(struct page *page)
1213 {
1214         return 0;
1215 };
1216 
1217 /*
1218  * A single inode exists for all anon_inode files. Contrary to pipes,
1219  * anon_inode inodes have no associated per-instance data, so we need
1220  * only allocate one of them.
1221  */
1222 struct inode *alloc_anon_inode(struct super_block *s)
1223 {
1224         static const struct address_space_operations anon_aops = {
1225                 .set_page_dirty = anon_set_page_dirty,
1226         };
1227         struct inode *inode = new_inode_pseudo(s);
1228 
1229         if (!inode)
1230                 return ERR_PTR(-ENOMEM);
1231 
1232         inode->i_ino = get_next_ino();
1233         inode->i_mapping->a_ops = &anon_aops;
1234 
1235         /*
1236          * Mark the inode dirty from the very beginning,
1237          * that way it will never be moved to the dirty
1238          * list because mark_inode_dirty() will think
1239          * that it already _is_ on the dirty list.
1240          */
1241         inode->i_state = I_DIRTY;
1242         inode->i_mode = S_IRUSR | S_IWUSR;
1243         inode->i_uid = current_fsuid();
1244         inode->i_gid = current_fsgid();
1245         inode->i_flags |= S_PRIVATE;
1246         inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
1247         return inode;
1248 }
1249 EXPORT_SYMBOL(alloc_anon_inode);
1250 
1251 /**
1252  * simple_nosetlease - generic helper for prohibiting leases
1253  * @filp: file pointer
1254  * @arg: type of lease to obtain
1255  * @flp: new lease supplied for insertion
1256  * @priv: private data for lm_setup operation
1257  *
1258  * Generic helper for filesystems that do not wish to allow leases to be set.
1259  * All arguments are ignored and it just returns -EINVAL.
1260  */
1261 int
1262 simple_nosetlease(struct file *filp, long arg, struct file_lock **flp,
1263                   void **priv)
1264 {
1265         return -EINVAL;
1266 }
1267 EXPORT_SYMBOL(simple_nosetlease);
1268 
1269 /**
1270  * simple_get_link - generic helper to get the target of "fast" symlinks
1271  * @dentry: not used here
1272  * @inode: the symlink inode
1273  * @done: not used here
1274  *
1275  * Generic helper for filesystems to use for symlink inodes where a pointer to
1276  * the symlink target is stored in ->i_link.  NOTE: this isn't normally called,
1277  * since as an optimization the path lookup code uses any non-NULL ->i_link
1278  * directly, without calling ->get_link().  But ->get_link() still must be set,
1279  * to mark the inode_operations as being for a symlink.
1280  *
1281  * Return: the symlink target
1282  */
1283 const char *simple_get_link(struct dentry *dentry, struct inode *inode,
1284                             struct delayed_call *done)
1285 {
1286         return inode->i_link;
1287 }
1288 EXPORT_SYMBOL(simple_get_link);
1289 
1290 const struct inode_operations simple_symlink_inode_operations = {
1291         .get_link = simple_get_link,
1292 };
1293 EXPORT_SYMBOL(simple_symlink_inode_operations);
1294 
1295 /*
1296  * Operations for a permanently empty directory.
1297  */
1298 static struct dentry *empty_dir_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
1299 {
1300         return ERR_PTR(-ENOENT);
1301 }
1302 
1303 static int empty_dir_getattr(const struct path *path, struct kstat *stat,
1304                              u32 request_mask, unsigned int query_flags)
1305 {
1306         struct inode *inode = d_inode(path->dentry);
1307         generic_fillattr(inode, stat);
1308         return 0;
1309 }
1310 
1311 static int empty_dir_setattr(struct dentry *dentry, struct iattr *attr)
1312 {
1313         return -EPERM;
1314 }
1315 
1316 static ssize_t empty_dir_listxattr(struct dentry *dentry, char *list, size_t size)
1317 {
1318         return -EOPNOTSUPP;
1319 }
1320 
1321 static const struct inode_operations empty_dir_inode_operations = {
1322         .lookup         = empty_dir_lookup,
1323         .permission     = generic_permission,
1324         .setattr        = empty_dir_setattr,
1325         .getattr        = empty_dir_getattr,
1326         .listxattr      = empty_dir_listxattr,
1327 };
1328 
1329 static loff_t empty_dir_llseek(struct file *file, loff_t offset, int whence)
1330 {
1331         /* An empty directory has two entries . and .. at offsets 0 and 1 */
1332         return generic_file_llseek_size(file, offset, whence, 2, 2);
1333 }
1334 
1335 static int empty_dir_readdir(struct file *file, struct dir_context *ctx)
1336 {
1337         dir_emit_dots(file, ctx);
1338         return 0;
1339 }
1340 
1341 static const struct file_operations empty_dir_operations = {
1342         .llseek         = empty_dir_llseek,
1343         .read           = generic_read_dir,
1344         .iterate_shared = empty_dir_readdir,
1345         .fsync          = noop_fsync,
1346 };
1347 
1348 
1349 void make_empty_dir_inode(struct inode *inode)
1350 {
1351         set_nlink(inode, 2);
1352         inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO;
1353         inode->i_uid = GLOBAL_ROOT_UID;
1354         inode->i_gid = GLOBAL_ROOT_GID;
1355         inode->i_rdev = 0;
1356         inode->i_size = 0;
1357         inode->i_blkbits = PAGE_SHIFT;
1358         inode->i_blocks = 0;
1359 
1360         inode->i_op = &empty_dir_inode_operations;
1361         inode->i_opflags &= ~IOP_XATTR;
1362         inode->i_fop = &empty_dir_operations;
1363 }
1364 
1365 bool is_empty_dir_inode(struct inode *inode)
1366 {
1367         return (inode->i_fop == &empty_dir_operations) &&
1368                 (inode->i_op == &empty_dir_inode_operations);
1369 }
1370 
1371 #ifdef CONFIG_UNICODE
1372 /*
1373  * Determine if the name of a dentry should be casefolded.
1374  *
1375  * Return: if names will need casefolding
1376  */
1377 static bool needs_casefold(const struct inode *dir)
1378 {
1379         return IS_CASEFOLDED(dir) && dir->i_sb->s_encoding;
1380 }
1381 
1382 /**
1383  * generic_ci_d_compare - generic d_compare implementation for casefolding filesystems
1384  * @dentry:     dentry whose name we are checking against
1385  * @len:        len of name of dentry
1386  * @str:        str pointer to name of dentry
1387  * @name:       Name to compare against
1388  *
1389  * Return: 0 if names match, 1 if mismatch, or -ERRNO
1390  */
1391 int generic_ci_d_compare(const struct dentry *dentry, unsigned int len,
1392                           const char *str, const struct qstr *name)
1393 {
1394         const struct dentry *parent = READ_ONCE(dentry->d_parent);
1395         const struct inode *dir = READ_ONCE(parent->d_inode);
1396         const struct super_block *sb = dentry->d_sb;
1397         const struct unicode_map *um = sb->s_encoding;
1398         struct qstr qstr = QSTR_INIT(str, len);
1399         char strbuf[DNAME_INLINE_LEN];
1400         int ret;
1401 
1402         if (!dir || !needs_casefold(dir))
1403                 goto fallback;
1404         /*
1405          * If the dentry name is stored in-line, then it may be concurrently
1406          * modified by a rename.  If this happens, the VFS will eventually retry
1407          * the lookup, so it doesn't matter what ->d_compare() returns.
1408          * However, it's unsafe to call utf8_strncasecmp() with an unstable
1409          * string.  Therefore, we have to copy the name into a temporary buffer.
1410          */
1411         if (len <= DNAME_INLINE_LEN - 1) {
1412                 memcpy(strbuf, str, len);
1413                 strbuf[len] = 0;
1414                 qstr.name = strbuf;
1415                 /* prevent compiler from optimizing out the temporary buffer */
1416                 barrier();
1417         }
1418         ret = utf8_strncasecmp(um, name, &qstr);
1419         if (ret >= 0)
1420                 return ret;
1421 
1422         if (sb_has_strict_encoding(sb))
1423                 return -EINVAL;
1424 fallback:
1425         if (len != name->len)
1426                 return 1;
1427         return !!memcmp(str, name->name, len);
1428 }
1429 EXPORT_SYMBOL(generic_ci_d_compare);
1430 
1431 /**
1432  * generic_ci_d_hash - generic d_hash implementation for casefolding filesystems
1433  * @dentry:     dentry of the parent directory
1434  * @str:        qstr of name whose hash we should fill in
1435  *
1436  * Return: 0 if hash was successful or unchanged, and -EINVAL on error
1437  */
1438 int generic_ci_d_hash(const struct dentry *dentry, struct qstr *str)
1439 {
1440         const struct inode *dir = READ_ONCE(dentry->d_inode);
1441         struct super_block *sb = dentry->d_sb;
1442         const struct unicode_map *um = sb->s_encoding;
1443         int ret = 0;
1444 
1445         if (!dir || !needs_casefold(dir))
1446                 return 0;
1447 
1448         ret = utf8_casefold_hash(um, dentry, str);
1449         if (ret < 0 && sb_has_strict_encoding(sb))
1450                 return -EINVAL;
1451         return 0;
1452 }
1453 EXPORT_SYMBOL(generic_ci_d_hash);
1454 #endif
1455 

~ [ source navigation ] ~ [ diff markup ] ~ [ identifier search ] ~

kernel.org | git.kernel.org | LWN.net | Project Home | Wiki (Japanese) | Wiki (English) | SVN repository | Mail admin

Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.

osdn.jp