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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
24#include <linux/uaccess.h>
25
26#include "internal.h"
27
28int simple_getattr(const struct path *path, struct kstat *stat,
29 u32 request_mask, unsigned int query_flags)
30{
31 struct inode *inode = d_inode(path->dentry);
32 generic_fillattr(inode, stat);
33 stat->blocks = inode->i_mapping->nrpages << (PAGE_SHIFT - 9);
34 return 0;
35}
36EXPORT_SYMBOL(simple_getattr);
37
38int simple_statfs(struct dentry *dentry, struct kstatfs *buf)
39{
40 buf->f_type = dentry->d_sb->s_magic;
41 buf->f_bsize = PAGE_SIZE;
42 buf->f_namelen = NAME_MAX;
43 return 0;
44}
45EXPORT_SYMBOL(simple_statfs);
46
47/*
48 * Retaining negative dentries for an in-memory filesystem just wastes
49 * memory and lookup time: arrange for them to be deleted immediately.
50 */
51int always_delete_dentry(const struct dentry *dentry)
52{
53 return 1;
54}
55EXPORT_SYMBOL(always_delete_dentry);
56
57const struct dentry_operations simple_dentry_operations = {
58 .d_delete = always_delete_dentry,
59};
60EXPORT_SYMBOL(simple_dentry_operations);
61
62/*
63 * Lookup the data. This is trivial - if the dentry didn't already
64 * exist, we know it is negative. Set d_op to delete negative dentries.
65 */
66struct dentry *simple_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
67{
68 if (dentry->d_name.len > NAME_MAX)
69 return ERR_PTR(-ENAMETOOLONG);
70 if (!dentry->d_sb->s_d_op)
71 d_set_d_op(dentry, &simple_dentry_operations);
72 d_add(dentry, NULL);
73 return NULL;
74}
75EXPORT_SYMBOL(simple_lookup);
76
77int dcache_dir_open(struct inode *inode, struct file *file)
78{
79 file->private_data = d_alloc_cursor(file->f_path.dentry);
80
81 return file->private_data ? 0 : -ENOMEM;
82}
83EXPORT_SYMBOL(dcache_dir_open);
84
85int dcache_dir_close(struct inode *inode, struct file *file)
86{
87 dput(file->private_data);
88 return 0;
89}
90EXPORT_SYMBOL(dcache_dir_close);
91
92/* parent is locked at least shared */
93/*
94 * Returns an element of siblings' list.
95 * We are looking for <count>th positive after <p>; if
96 * found, dentry is grabbed and returned to caller.
97 * If no such element exists, NULL is returned.
98 */
99static struct dentry *scan_positives(struct dentry *cursor,
100 struct list_head *p,
101 loff_t count,
102 struct dentry *last)
103{
104 struct dentry *dentry = cursor->d_parent, *found = NULL;
105
106 spin_lock(&dentry->d_lock);
107 while ((p = p->next) != &dentry->d_subdirs) {
108 struct dentry *d = list_entry(p, struct dentry, d_child);
109 // we must at least skip cursors, to avoid livelocks
110 if (d->d_flags & DCACHE_DENTRY_CURSOR)
111 continue;
112 if (simple_positive(d) && !--count) {
113 spin_lock_nested(&d->d_lock, DENTRY_D_LOCK_NESTED);
114 if (simple_positive(d))
115 found = dget_dlock(d);
116 spin_unlock(&d->d_lock);
117 if (likely(found))
118 break;
119 count = 1;
120 }
121 if (need_resched()) {
122 list_move(&cursor->d_child, p);
123 p = &cursor->d_child;
124 spin_unlock(&dentry->d_lock);
125 cond_resched();
126 spin_lock(&dentry->d_lock);
127 }
128 }
129 spin_unlock(&dentry->d_lock);
130 dput(last);
131 return found;
132}
133
134loff_t dcache_dir_lseek(struct file *file, loff_t offset, int whence)
135{
136 struct dentry *dentry = file->f_path.dentry;
137 switch (whence) {
138 case 1:
139 offset += file->f_pos;
140 fallthrough;
141 case 0:
142 if (offset >= 0)
143 break;
144 fallthrough;
145 default:
146 return -EINVAL;
147 }
148 if (offset != file->f_pos) {
149 struct dentry *cursor = file->private_data;
150 struct dentry *to = NULL;
151
152 inode_lock_shared(dentry->d_inode);
153
154 if (offset > 2)
155 to = scan_positives(cursor, &dentry->d_subdirs,
156 offset - 2, NULL);
157 spin_lock(&dentry->d_lock);
158 if (to)
159 list_move(&cursor->d_child, &to->d_child);
160 else
161 list_del_init(&cursor->d_child);
162 spin_unlock(&dentry->d_lock);
163 dput(to);
164
165 file->f_pos = offset;
166
167 inode_unlock_shared(dentry->d_inode);
168 }
169 return offset;
170}
171EXPORT_SYMBOL(dcache_dir_lseek);
172
173/* Relationship between i_mode and the DT_xxx types */
174static inline unsigned char dt_type(struct inode *inode)
175{
176 return (inode->i_mode >> 12) & 15;
177}
178
179/*
180 * Directory is locked and all positive dentries in it are safe, since
181 * for ramfs-type trees they can't go away without unlink() or rmdir(),
182 * both impossible due to the lock on directory.
183 */
184
185int dcache_readdir(struct file *file, struct dir_context *ctx)
186{
187 struct dentry *dentry = file->f_path.dentry;
188 struct dentry *cursor = file->private_data;
189 struct list_head *anchor = &dentry->d_subdirs;
190 struct dentry *next = NULL;
191 struct list_head *p;
192
193 if (!dir_emit_dots(file, ctx))
194 return 0;
195
196 if (ctx->pos == 2)
197 p = anchor;
198 else if (!list_empty(&cursor->d_child))
199 p = &cursor->d_child;
200 else
201 return 0;
202
203 while ((next = scan_positives(cursor, p, 1, next)) != NULL) {
204 if (!dir_emit(ctx, next->d_name.name, next->d_name.len,
205 d_inode(next)->i_ino, dt_type(d_inode(next))))
206 break;
207 ctx->pos++;
208 p = &next->d_child;
209 }
210 spin_lock(&dentry->d_lock);
211 if (next)
212 list_move_tail(&cursor->d_child, &next->d_child);
213 else
214 list_del_init(&cursor->d_child);
215 spin_unlock(&dentry->d_lock);
216 dput(next);
217
218 return 0;
219}
220EXPORT_SYMBOL(dcache_readdir);
221
222ssize_t generic_read_dir(struct file *filp, char __user *buf, size_t siz, loff_t *ppos)
223{
224 return -EISDIR;
225}
226EXPORT_SYMBOL(generic_read_dir);
227
228const struct file_operations simple_dir_operations = {
229 .open = dcache_dir_open,
230 .release = dcache_dir_close,
231 .llseek = dcache_dir_lseek,
232 .read = generic_read_dir,
233 .iterate_shared = dcache_readdir,
234 .fsync = noop_fsync,
235};
236EXPORT_SYMBOL(simple_dir_operations);
237
238const struct inode_operations simple_dir_inode_operations = {
239 .lookup = simple_lookup,
240};
241EXPORT_SYMBOL(simple_dir_inode_operations);
242
243static struct dentry *find_next_child(struct dentry *parent, struct dentry *prev)
244{
245 struct dentry *child = NULL;
246 struct list_head *p = prev ? &prev->d_child : &parent->d_subdirs;
247
248 spin_lock(&parent->d_lock);
249 while ((p = p->next) != &parent->d_subdirs) {
250 struct dentry *d = container_of(p, struct dentry, d_child);
251 if (simple_positive(d)) {
252 spin_lock_nested(&d->d_lock, DENTRY_D_LOCK_NESTED);
253 if (simple_positive(d))
254 child = dget_dlock(d);
255 spin_unlock(&d->d_lock);
256 if (likely(child))
257 break;
258 }
259 }
260 spin_unlock(&parent->d_lock);
261 dput(prev);
262 return child;
263}
264
265void simple_recursive_removal(struct dentry *dentry,
266 void (*callback)(struct dentry *))
267{
268 struct dentry *this = dget(dentry);
269 while (true) {
270 struct dentry *victim = NULL, *child;
271 struct inode *inode = this->d_inode;
272
273 inode_lock(inode);
274 if (d_is_dir(this))
275 inode->i_flags |= S_DEAD;
276 while ((child = find_next_child(this, victim)) == NULL) {
277 // kill and ascend
278 // update metadata while it's still locked
279 inode->i_ctime = current_time(inode);
280 clear_nlink(inode);
281 inode_unlock(inode);
282 victim = this;
283 this = this->d_parent;
284 inode = this->d_inode;
285 inode_lock(inode);
286 if (simple_positive(victim)) {
287 d_invalidate(victim); // avoid lost mounts
288 if (d_is_dir(victim))
289 fsnotify_rmdir(inode, victim);
290 else
291 fsnotify_unlink(inode, victim);
292 if (callback)
293 callback(victim);
294 dput(victim); // unpin it
295 }
296 if (victim == dentry) {
297 inode->i_ctime = inode->i_mtime =
298 current_time(inode);
299 if (d_is_dir(dentry))
300 drop_nlink(inode);
301 inode_unlock(inode);
302 dput(dentry);
303 return;
304 }
305 }
306 inode_unlock(inode);
307 this = child;
308 }
309}
310EXPORT_SYMBOL(simple_recursive_removal);
311
312static const struct super_operations simple_super_operations = {
313 .statfs = simple_statfs,
314};
315
316static int pseudo_fs_fill_super(struct super_block *s, struct fs_context *fc)
317{
318 struct pseudo_fs_context *ctx = fc->fs_private;
319 struct inode *root;
320
321 s->s_maxbytes = MAX_LFS_FILESIZE;
322 s->s_blocksize = PAGE_SIZE;
323 s->s_blocksize_bits = PAGE_SHIFT;
324 s->s_magic = ctx->magic;
325 s->s_op = ctx->ops ?: &simple_super_operations;
326 s->s_xattr = ctx->xattr;
327 s->s_time_gran = 1;
328 root = new_inode(s);
329 if (!root)
330 return -ENOMEM;
331
332 /*
333 * since this is the first inode, make it number 1. New inodes created
334 * after this must take care not to collide with it (by passing
335 * max_reserved of 1 to iunique).
336 */
337 root->i_ino = 1;
338 root->i_mode = S_IFDIR | S_IRUSR | S_IWUSR;
339 root->i_atime = root->i_mtime = root->i_ctime = current_time(root);
340 s->s_root = d_make_root(root);
341 if (!s->s_root)
342 return -ENOMEM;
343 s->s_d_op = ctx->dops;
344 return 0;
345}
346
347static int pseudo_fs_get_tree(struct fs_context *fc)
348{
349 return get_tree_nodev(fc, pseudo_fs_fill_super);
350}
351
352static void pseudo_fs_free(struct fs_context *fc)
353{
354 kfree(fc->fs_private);
355}
356
357static const struct fs_context_operations pseudo_fs_context_ops = {
358 .free = pseudo_fs_free,
359 .get_tree = pseudo_fs_get_tree,
360};
361
362/*
363 * Common helper for pseudo-filesystems (sockfs, pipefs, bdev - stuff that
364 * will never be mountable)
365 */
366struct pseudo_fs_context *init_pseudo(struct fs_context *fc,
367 unsigned long magic)
368{
369 struct pseudo_fs_context *ctx;
370
371 ctx = kzalloc(sizeof(struct pseudo_fs_context), GFP_KERNEL);
372 if (likely(ctx)) {
373 ctx->magic = magic;
374 fc->fs_private = ctx;
375 fc->ops = &pseudo_fs_context_ops;
376 fc->sb_flags |= SB_NOUSER;
377 fc->global = true;
378 }
379 return ctx;
380}
381EXPORT_SYMBOL(init_pseudo);
382
383int simple_open(struct inode *inode, struct file *file)
384{
385 if (inode->i_private)
386 file->private_data = inode->i_private;
387 return 0;
388}
389EXPORT_SYMBOL(simple_open);
390
391int simple_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
392{
393 struct inode *inode = d_inode(old_dentry);
394
395 inode->i_ctime = dir->i_ctime = dir->i_mtime = current_time(inode);
396 inc_nlink(inode);
397 ihold(inode);
398 dget(dentry);
399 d_instantiate(dentry, inode);
400 return 0;
401}
402EXPORT_SYMBOL(simple_link);
403
404int simple_empty(struct dentry *dentry)
405{
406 struct dentry *child;
407 int ret = 0;
408
409 spin_lock(&dentry->d_lock);
410 list_for_each_entry(child, &dentry->d_subdirs, d_child) {
411 spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED);
412 if (simple_positive(child)) {
413 spin_unlock(&child->d_lock);
414 goto out;
415 }
416 spin_unlock(&child->d_lock);
417 }
418 ret = 1;
419out:
420 spin_unlock(&dentry->d_lock);
421 return ret;
422}
423EXPORT_SYMBOL(simple_empty);
424
425int simple_unlink(struct inode *dir, struct dentry *dentry)
426{
427 struct inode *inode = d_inode(dentry);
428
429 inode->i_ctime = dir->i_ctime = dir->i_mtime = current_time(inode);
430 drop_nlink(inode);
431 dput(dentry);
432 return 0;
433}
434EXPORT_SYMBOL(simple_unlink);
435
436int simple_rmdir(struct inode *dir, struct dentry *dentry)
437{
438 if (!simple_empty(dentry))
439 return -ENOTEMPTY;
440
441 drop_nlink(d_inode(dentry));
442 simple_unlink(dir, dentry);
443 drop_nlink(dir);
444 return 0;
445}
446EXPORT_SYMBOL(simple_rmdir);
447
448int simple_rename(struct inode *old_dir, struct dentry *old_dentry,
449 struct inode *new_dir, struct dentry *new_dentry,
450 unsigned int flags)
451{
452 struct inode *inode = d_inode(old_dentry);
453 int they_are_dirs = d_is_dir(old_dentry);
454
455 if (flags & ~RENAME_NOREPLACE)
456 return -EINVAL;
457
458 if (!simple_empty(new_dentry))
459 return -ENOTEMPTY;
460
461 if (d_really_is_positive(new_dentry)) {
462 simple_unlink(new_dir, new_dentry);
463 if (they_are_dirs) {
464 drop_nlink(d_inode(new_dentry));
465 drop_nlink(old_dir);
466 }
467 } else if (they_are_dirs) {
468 drop_nlink(old_dir);
469 inc_nlink(new_dir);
470 }
471
472 old_dir->i_ctime = old_dir->i_mtime = new_dir->i_ctime =
473 new_dir->i_mtime = inode->i_ctime = current_time(old_dir);
474
475 return 0;
476}
477EXPORT_SYMBOL(simple_rename);
478
479/**
480 * simple_setattr - setattr for simple filesystem
481 * @dentry: dentry
482 * @iattr: iattr structure
483 *
484 * Returns 0 on success, -error on failure.
485 *
486 * simple_setattr is a simple ->setattr implementation without a proper
487 * implementation of size changes.
488 *
489 * It can either be used for in-memory filesystems or special files
490 * on simple regular filesystems. Anything that needs to change on-disk
491 * or wire state on size changes needs its own setattr method.
492 */
493int simple_setattr(struct dentry *dentry, struct iattr *iattr)
494{
495 struct inode *inode = d_inode(dentry);
496 int error;
497
498 error = setattr_prepare(dentry, iattr);
499 if (error)
500 return error;
501
502 if (iattr->ia_valid & ATTR_SIZE)
503 truncate_setsize(inode, iattr->ia_size);
504 setattr_copy(inode, iattr);
505 mark_inode_dirty(inode);
506 return 0;
507}
508EXPORT_SYMBOL(simple_setattr);
509
510int simple_readpage(struct file *file, struct page *page)
511{
512 clear_highpage(page);
513 flush_dcache_page(page);
514 SetPageUptodate(page);
515 unlock_page(page);
516 return 0;
517}
518EXPORT_SYMBOL(simple_readpage);
519
520int simple_write_begin(struct file *file, struct address_space *mapping,
521 loff_t pos, unsigned len, unsigned flags,
522 struct page **pagep, void **fsdata)
523{
524 struct page *page;
525 pgoff_t index;
526
527 index = pos >> PAGE_SHIFT;
528
529 page = grab_cache_page_write_begin(mapping, index, flags);
530 if (!page)
531 return -ENOMEM;
532
533 *pagep = page;
534
535 if (!PageUptodate(page) && (len != PAGE_SIZE)) {
536 unsigned from = pos & (PAGE_SIZE - 1);
537
538 zero_user_segments(page, 0, from, from + len, PAGE_SIZE);
539 }
540 return 0;
541}
542EXPORT_SYMBOL(simple_write_begin);
543
544/**
545 * simple_write_end - .write_end helper for non-block-device FSes
546 * @file: See .write_end of address_space_operations
547 * @mapping: "
548 * @pos: "
549 * @len: "
550 * @copied: "
551 * @page: "
552 * @fsdata: "
553 *
554 * simple_write_end does the minimum needed for updating a page after writing is
555 * done. It has the same API signature as the .write_end of
556 * address_space_operations vector. So it can just be set onto .write_end for
557 * FSes that don't need any other processing. i_mutex is assumed to be held.
558 * Block based filesystems should use generic_write_end().
559 * NOTE: Even though i_size might get updated by this function, mark_inode_dirty
560 * is not called, so a filesystem that actually does store data in .write_inode
561 * should extend on what's done here with a call to mark_inode_dirty() in the
562 * case that i_size has changed.
563 *
564 * Use *ONLY* with simple_readpage()
565 */
566int simple_write_end(struct file *file, struct address_space *mapping,
567 loff_t pos, unsigned len, unsigned copied,
568 struct page *page, void *fsdata)
569{
570 struct inode *inode = page->mapping->host;
571 loff_t last_pos = pos + copied;
572
573 /* zero the stale part of the page if we did a short copy */
574 if (!PageUptodate(page)) {
575 if (copied < len) {
576 unsigned from = pos & (PAGE_SIZE - 1);
577
578 zero_user(page, from + copied, len - copied);
579 }
580 SetPageUptodate(page);
581 }
582 /*
583 * No need to use i_size_read() here, the i_size
584 * cannot change under us because we hold the i_mutex.
585 */
586 if (last_pos > inode->i_size)
587 i_size_write(inode, last_pos);
588
589 set_page_dirty(page);
590 unlock_page(page);
591 put_page(page);
592
593 return copied;
594}
595EXPORT_SYMBOL(simple_write_end);
596
597/*
598 * the inodes created here are not hashed. If you use iunique to generate
599 * unique inode values later for this filesystem, then you must take care
600 * to pass it an appropriate max_reserved value to avoid collisions.
601 */
602int simple_fill_super(struct super_block *s, unsigned long magic,
603 const struct tree_descr *files)
604{
605 struct inode *inode;
606 struct dentry *root;
607 struct dentry *dentry;
608 int i;
609
610 s->s_blocksize = PAGE_SIZE;
611 s->s_blocksize_bits = PAGE_SHIFT;
612 s->s_magic = magic;
613 s->s_op = &simple_super_operations;
614 s->s_time_gran = 1;
615
616 inode = new_inode(s);
617 if (!inode)
618 return -ENOMEM;
619 /*
620 * because the root inode is 1, the files array must not contain an
621 * entry at index 1
622 */
623 inode->i_ino = 1;
624 inode->i_mode = S_IFDIR | 0755;
625 inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
626 inode->i_op = &simple_dir_inode_operations;
627 inode->i_fop = &simple_dir_operations;
628 set_nlink(inode, 2);
629 root = d_make_root(inode);
630 if (!root)
631 return -ENOMEM;
632 for (i = 0; !files->name || files->name[0]; i++, files++) {
633 if (!files->name)
634 continue;
635
636 /* warn if it tries to conflict with the root inode */
637 if (unlikely(i == 1))
638 printk(KERN_WARNING "%s: %s passed in a files array"
639 "with an index of 1!\n", __func__,
640 s->s_type->name);
641
642 dentry = d_alloc_name(root, files->name);
643 if (!dentry)
644 goto out;
645 inode = new_inode(s);
646 if (!inode) {
647 dput(dentry);
648 goto out;
649 }
650 inode->i_mode = S_IFREG | files->mode;
651 inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
652 inode->i_fop = files->ops;
653 inode->i_ino = i;
654 d_add(dentry, inode);
655 }
656 s->s_root = root;
657 return 0;
658out:
659 d_genocide(root);
660 shrink_dcache_parent(root);
661 dput(root);
662 return -ENOMEM;
663}
664EXPORT_SYMBOL(simple_fill_super);
665
666static DEFINE_SPINLOCK(pin_fs_lock);
667
668int simple_pin_fs(struct file_system_type *type, struct vfsmount **mount, int *count)
669{
670 struct vfsmount *mnt = NULL;
671 spin_lock(&pin_fs_lock);
672 if (unlikely(!*mount)) {
673 spin_unlock(&pin_fs_lock);
674 mnt = vfs_kern_mount(type, SB_KERNMOUNT, type->name, NULL);
675 if (IS_ERR(mnt))
676 return PTR_ERR(mnt);
677 spin_lock(&pin_fs_lock);
678 if (!*mount)
679 *mount = mnt;
680 }
681 mntget(*mount);
682 ++*count;
683 spin_unlock(&pin_fs_lock);
684 mntput(mnt);
685 return 0;
686}
687EXPORT_SYMBOL(simple_pin_fs);
688
689void simple_release_fs(struct vfsmount **mount, int *count)
690{
691 struct vfsmount *mnt;
692 spin_lock(&pin_fs_lock);
693 mnt = *mount;
694 if (!--*count)
695 *mount = NULL;
696 spin_unlock(&pin_fs_lock);
697 mntput(mnt);
698}
699EXPORT_SYMBOL(simple_release_fs);
700
701/**
702 * simple_read_from_buffer - copy data from the buffer to user space
703 * @to: the user space buffer to read to
704 * @count: the maximum number of bytes to read
705 * @ppos: the current position in the buffer
706 * @from: the buffer to read from
707 * @available: the size of the buffer
708 *
709 * The simple_read_from_buffer() function reads up to @count bytes from the
710 * buffer @from at offset @ppos into the user space address starting at @to.
711 *
712 * On success, the number of bytes read is returned and the offset @ppos is
713 * advanced by this number, or negative value is returned on error.
714 **/
715ssize_t simple_read_from_buffer(void __user *to, size_t count, loff_t *ppos,
716 const void *from, size_t available)
717{
718 loff_t pos = *ppos;
719 size_t ret;
720
721 if (pos < 0)
722 return -EINVAL;
723 if (pos >= available || !count)
724 return 0;
725 if (count > available - pos)
726 count = available - pos;
727 ret = copy_to_user(to, from + pos, count);
728 if (ret == count)
729 return -EFAULT;
730 count -= ret;
731 *ppos = pos + count;
732 return count;
733}
734EXPORT_SYMBOL(simple_read_from_buffer);
735
736/**
737 * simple_write_to_buffer - copy data from user space to the buffer
738 * @to: the buffer to write to
739 * @available: the size of the buffer
740 * @ppos: the current position in the buffer
741 * @from: the user space buffer to read from
742 * @count: the maximum number of bytes to read
743 *
744 * The simple_write_to_buffer() function reads up to @count bytes from the user
745 * space address starting at @from into the buffer @to at offset @ppos.
746 *
747 * On success, the number of bytes written is returned and the offset @ppos is
748 * advanced by this number, or negative value is returned on error.
749 **/
750ssize_t simple_write_to_buffer(void *to, size_t available, loff_t *ppos,
751 const void __user *from, size_t count)
752{
753 loff_t pos = *ppos;
754 size_t res;
755
756 if (pos < 0)
757 return -EINVAL;
758 if (pos >= available || !count)
759 return 0;
760 if (count > available - pos)
761 count = available - pos;
762 res = copy_from_user(to + pos, from, count);
763 if (res == count)
764 return -EFAULT;
765 count -= res;
766 *ppos = pos + count;
767 return count;
768}
769EXPORT_SYMBOL(simple_write_to_buffer);
770
771/**
772 * memory_read_from_buffer - copy data from the buffer
773 * @to: the kernel space buffer to read to
774 * @count: the maximum number of bytes to read
775 * @ppos: the current position in the buffer
776 * @from: the buffer to read from
777 * @available: the size of the buffer
778 *
779 * The memory_read_from_buffer() function reads up to @count bytes from the
780 * buffer @from at offset @ppos into the kernel space address starting at @to.
781 *
782 * On success, the number of bytes read is returned and the offset @ppos is
783 * advanced by this number, or negative value is returned on error.
784 **/
785ssize_t memory_read_from_buffer(void *to, size_t count, loff_t *ppos,
786 const void *from, size_t available)
787{
788 loff_t pos = *ppos;
789
790 if (pos < 0)
791 return -EINVAL;
792 if (pos >= available)
793 return 0;
794 if (count > available - pos)
795 count = available - pos;
796 memcpy(to, from + pos, count);
797 *ppos = pos + count;
798
799 return count;
800}
801EXPORT_SYMBOL(memory_read_from_buffer);
802
803/*
804 * Transaction based IO.
805 * The file expects a single write which triggers the transaction, and then
806 * possibly a read which collects the result - which is stored in a
807 * file-local buffer.
808 */
809
810void simple_transaction_set(struct file *file, size_t n)
811{
812 struct simple_transaction_argresp *ar = file->private_data;
813
814 BUG_ON(n > SIMPLE_TRANSACTION_LIMIT);
815
816 /*
817 * The barrier ensures that ar->size will really remain zero until
818 * ar->data is ready for reading.
819 */
820 smp_mb();
821 ar->size = n;
822}
823EXPORT_SYMBOL(simple_transaction_set);
824
825char *simple_transaction_get(struct file *file, const char __user *buf, size_t size)
826{
827 struct simple_transaction_argresp *ar;
828 static DEFINE_SPINLOCK(simple_transaction_lock);
829
830 if (size > SIMPLE_TRANSACTION_LIMIT - 1)
831 return ERR_PTR(-EFBIG);
832
833 ar = (struct simple_transaction_argresp *)get_zeroed_page(GFP_KERNEL);
834 if (!ar)
835 return ERR_PTR(-ENOMEM);
836
837 spin_lock(&simple_transaction_lock);
838
839 /* only one write allowed per open */
840 if (file->private_data) {
841 spin_unlock(&simple_transaction_lock);
842 free_page((unsigned long)ar);
843 return ERR_PTR(-EBUSY);
844 }
845
846 file->private_data = ar;
847
848 spin_unlock(&simple_transaction_lock);
849
850 if (copy_from_user(ar->data, buf, size))
851 return ERR_PTR(-EFAULT);
852
853 return ar->data;
854}
855EXPORT_SYMBOL(simple_transaction_get);
856
857ssize_t simple_transaction_read(struct file *file, char __user *buf, size_t size, loff_t *pos)
858{
859 struct simple_transaction_argresp *ar = file->private_data;
860
861 if (!ar)
862 return 0;
863 return simple_read_from_buffer(buf, size, pos, ar->data, ar->size);
864}
865EXPORT_SYMBOL(simple_transaction_read);
866
867int simple_transaction_release(struct inode *inode, struct file *file)
868{
869 free_page((unsigned long)file->private_data);
870 return 0;
871}
872EXPORT_SYMBOL(simple_transaction_release);
873
874/* Simple attribute files */
875
876struct simple_attr {
877 int (*get)(void *, u64 *);
878 int (*set)(void *, u64);
879 char get_buf[24]; /* enough to store a u64 and "\n\0" */
880 char set_buf[24];
881 void *data;
882 const char *fmt; /* format for read operation */
883 struct mutex mutex; /* protects access to these buffers */
884};
885
886/* simple_attr_open is called by an actual attribute open file operation
887 * to set the attribute specific access operations. */
888int simple_attr_open(struct inode *inode, struct file *file,
889 int (*get)(void *, u64 *), int (*set)(void *, u64),
890 const char *fmt)
891{
892 struct simple_attr *attr;
893
894 attr = kzalloc(sizeof(*attr), GFP_KERNEL);
895 if (!attr)
896 return -ENOMEM;
897
898 attr->get = get;
899 attr->set = set;
900 attr->data = inode->i_private;
901 attr->fmt = fmt;
902 mutex_init(&attr->mutex);
903
904 file->private_data = attr;
905
906 return nonseekable_open(inode, file);
907}
908EXPORT_SYMBOL_GPL(simple_attr_open);
909
910int simple_attr_release(struct inode *inode, struct file *file)
911{
912 kfree(file->private_data);
913 return 0;
914}
915EXPORT_SYMBOL_GPL(simple_attr_release); /* GPL-only? This? Really? */
916
917/* read from the buffer that is filled with the get function */
918ssize_t simple_attr_read(struct file *file, char __user *buf,
919 size_t len, loff_t *ppos)
920{
921 struct simple_attr *attr;
922 size_t size;
923 ssize_t ret;
924
925 attr = file->private_data;
926
927 if (!attr->get)
928 return -EACCES;
929
930 ret = mutex_lock_interruptible(&attr->mutex);
931 if (ret)
932 return ret;
933
934 if (*ppos && attr->get_buf[0]) {
935 /* continued read */
936 size = strlen(attr->get_buf);
937 } else {
938 /* first read */
939 u64 val;
940 ret = attr->get(attr->data, &val);
941 if (ret)
942 goto out;
943
944 size = scnprintf(attr->get_buf, sizeof(attr->get_buf),
945 attr->fmt, (unsigned long long)val);
946 }
947
948 ret = simple_read_from_buffer(buf, len, ppos, attr->get_buf, size);
949out:
950 mutex_unlock(&attr->mutex);
951 return ret;
952}
953EXPORT_SYMBOL_GPL(simple_attr_read);
954
955/* interpret the buffer as a number to call the set function with */
956ssize_t simple_attr_write(struct file *file, const char __user *buf,
957 size_t len, loff_t *ppos)
958{
959 struct simple_attr *attr;
960 u64 val;
961 size_t size;
962 ssize_t ret;
963
964 attr = file->private_data;
965 if (!attr->set)
966 return -EACCES;
967
968 ret = mutex_lock_interruptible(&attr->mutex);
969 if (ret)
970 return ret;
971
972 ret = -EFAULT;
973 size = min(sizeof(attr->set_buf) - 1, len);
974 if (copy_from_user(attr->set_buf, buf, size))
975 goto out;
976
977 attr->set_buf[size] = '\0';
978 val = simple_strtoll(attr->set_buf, NULL, 0);
979 ret = attr->set(attr->data, val);
980 if (ret == 0)
981 ret = len; /* on success, claim we got the whole input */
982out:
983 mutex_unlock(&attr->mutex);
984 return ret;
985}
986EXPORT_SYMBOL_GPL(simple_attr_write);
987
988/**
989 * generic_fh_to_dentry - generic helper for the fh_to_dentry export operation
990 * @sb: filesystem to do the file handle conversion on
991 * @fid: file handle to convert
992 * @fh_len: length of the file handle in bytes
993 * @fh_type: type of file handle
994 * @get_inode: filesystem callback to retrieve inode
995 *
996 * This function decodes @fid as long as it has one of the well-known
997 * Linux filehandle types and calls @get_inode on it to retrieve the
998 * inode for the object specified in the file handle.
999 */
1000struct dentry *generic_fh_to_dentry(struct super_block *sb, struct fid *fid,
1001 int fh_len, int fh_type, struct inode *(*get_inode)
1002 (struct super_block *sb, u64 ino, u32 gen))
1003{
1004 struct inode *inode = NULL;
1005
1006 if (fh_len < 2)
1007 return NULL;
1008
1009 switch (fh_type) {
1010 case FILEID_INO32_GEN:
1011 case FILEID_INO32_GEN_PARENT:
1012 inode = get_inode(sb, fid->i32.ino, fid->i32.gen);
1013 break;
1014 }
1015
1016 return d_obtain_alias(inode);
1017}
1018EXPORT_SYMBOL_GPL(generic_fh_to_dentry);
1019
1020/**
1021 * generic_fh_to_parent - generic helper for the fh_to_parent export operation
1022 * @sb: filesystem to do the file handle conversion on
1023 * @fid: file handle to convert
1024 * @fh_len: length of the file handle in bytes
1025 * @fh_type: type of file handle
1026 * @get_inode: filesystem callback to retrieve inode
1027 *
1028 * This function decodes @fid as long as it has one of the well-known
1029 * Linux filehandle types and calls @get_inode on it to retrieve the
1030 * inode for the _parent_ object specified in the file handle if it
1031 * is specified in the file handle, or NULL otherwise.
1032 */
1033struct dentry *generic_fh_to_parent(struct super_block *sb, struct fid *fid,
1034 int fh_len, int fh_type, struct inode *(*get_inode)
1035 (struct super_block *sb, u64 ino, u32 gen))
1036{
1037 struct inode *inode = NULL;
1038
1039 if (fh_len <= 2)
1040 return NULL;
1041
1042 switch (fh_type) {
1043 case FILEID_INO32_GEN_PARENT:
1044 inode = get_inode(sb, fid->i32.parent_ino,
1045 (fh_len > 3 ? fid->i32.parent_gen : 0));
1046 break;
1047 }
1048
1049 return d_obtain_alias(inode);
1050}
1051EXPORT_SYMBOL_GPL(generic_fh_to_parent);
1052
1053/**
1054 * __generic_file_fsync - generic fsync implementation for simple filesystems
1055 *
1056 * @file: file to synchronize
1057 * @start: start offset in bytes
1058 * @end: end offset in bytes (inclusive)
1059 * @datasync: only synchronize essential metadata if true
1060 *
1061 * This is a generic implementation of the fsync method for simple
1062 * filesystems which track all non-inode metadata in the buffers list
1063 * hanging off the address_space structure.
1064 */
1065int __generic_file_fsync(struct file *file, loff_t start, loff_t end,
1066 int datasync)
1067{
1068 struct inode *inode = file->f_mapping->host;
1069 int err;
1070 int ret;
1071
1072 err = file_write_and_wait_range(file, start, end);
1073 if (err)
1074 return err;
1075
1076 inode_lock(inode);
1077 ret = sync_mapping_buffers(inode->i_mapping);
1078 if (!(inode->i_state & I_DIRTY_ALL))
1079 goto out;
1080 if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
1081 goto out;
1082
1083 err = sync_inode_metadata(inode, 1);
1084 if (ret == 0)
1085 ret = err;
1086
1087out:
1088 inode_unlock(inode);
1089 /* check and advance again to catch errors after syncing out buffers */
1090 err = file_check_and_advance_wb_err(file);
1091 if (ret == 0)
1092 ret = err;
1093 return ret;
1094}
1095EXPORT_SYMBOL(__generic_file_fsync);
1096
1097/**
1098 * generic_file_fsync - generic fsync implementation for simple filesystems
1099 * with flush
1100 * @file: file to synchronize
1101 * @start: start offset in bytes
1102 * @end: end offset in bytes (inclusive)
1103 * @datasync: only synchronize essential metadata if true
1104 *
1105 */
1106
1107int generic_file_fsync(struct file *file, loff_t start, loff_t end,
1108 int datasync)
1109{
1110 struct inode *inode = file->f_mapping->host;
1111 int err;
1112
1113 err = __generic_file_fsync(file, start, end, datasync);
1114 if (err)
1115 return err;
1116 return blkdev_issue_flush(inode->i_sb->s_bdev, GFP_KERNEL);
1117}
1118EXPORT_SYMBOL(generic_file_fsync);
1119
1120/**
1121 * generic_check_addressable - Check addressability of file system
1122 * @blocksize_bits: log of file system block size
1123 * @num_blocks: number of blocks in file system
1124 *
1125 * Determine whether a file system with @num_blocks blocks (and a
1126 * block size of 2**@blocksize_bits) is addressable by the sector_t
1127 * and page cache of the system. Return 0 if so and -EFBIG otherwise.
1128 */
1129int generic_check_addressable(unsigned blocksize_bits, u64 num_blocks)
1130{
1131 u64 last_fs_block = num_blocks - 1;
1132 u64 last_fs_page =
1133 last_fs_block >> (PAGE_SHIFT - blocksize_bits);
1134
1135 if (unlikely(num_blocks == 0))
1136 return 0;
1137
1138 if ((blocksize_bits < 9) || (blocksize_bits > PAGE_SHIFT))
1139 return -EINVAL;
1140
1141 if ((last_fs_block > (sector_t)(~0ULL) >> (blocksize_bits - 9)) ||
1142 (last_fs_page > (pgoff_t)(~0ULL))) {
1143 return -EFBIG;
1144 }
1145 return 0;
1146}
1147EXPORT_SYMBOL(generic_check_addressable);
1148
1149/*
1150 * No-op implementation of ->fsync for in-memory filesystems.
1151 */
1152int noop_fsync(struct file *file, loff_t start, loff_t end, int datasync)
1153{
1154 return 0;
1155}
1156EXPORT_SYMBOL(noop_fsync);
1157
1158int noop_set_page_dirty(struct page *page)
1159{
1160 /*
1161 * Unlike __set_page_dirty_no_writeback that handles dirty page
1162 * tracking in the page object, dax does all dirty tracking in
1163 * the inode address_space in response to mkwrite faults. In the
1164 * dax case we only need to worry about potentially dirty CPU
1165 * caches, not dirty page cache pages to write back.
1166 *
1167 * This callback is defined to prevent fallback to
1168 * __set_page_dirty_buffers() in set_page_dirty().
1169 */
1170 return 0;
1171}
1172EXPORT_SYMBOL_GPL(noop_set_page_dirty);
1173
1174void noop_invalidatepage(struct page *page, unsigned int offset,
1175 unsigned int length)
1176{
1177 /*
1178 * There is no page cache to invalidate in the dax case, however
1179 * we need this callback defined to prevent falling back to
1180 * block_invalidatepage() in do_invalidatepage().
1181 */
1182}
1183EXPORT_SYMBOL_GPL(noop_invalidatepage);
1184
1185ssize_t noop_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
1186{
1187 /*
1188 * iomap based filesystems support direct I/O without need for
1189 * this callback. However, it still needs to be set in
1190 * inode->a_ops so that open/fcntl know that direct I/O is
1191 * generally supported.
1192 */
1193 return -EINVAL;
1194}
1195EXPORT_SYMBOL_GPL(noop_direct_IO);
1196
1197/* Because kfree isn't assignment-compatible with void(void*) ;-/ */
1198void kfree_link(void *p)
1199{
1200 kfree(p);
1201}
1202EXPORT_SYMBOL(kfree_link);
1203
1204/*
1205 * nop .set_page_dirty method so that people can use .page_mkwrite on
1206 * anon inodes.
1207 */
1208static int anon_set_page_dirty(struct page *page)
1209{
1210 return 0;
1211};
1212
1213/*
1214 * A single inode exists for all anon_inode files. Contrary to pipes,
1215 * anon_inode inodes have no associated per-instance data, so we need
1216 * only allocate one of them.
1217 */
1218struct inode *alloc_anon_inode(struct super_block *s)
1219{
1220 static const struct address_space_operations anon_aops = {
1221 .set_page_dirty = anon_set_page_dirty,
1222 };
1223 struct inode *inode = new_inode_pseudo(s);
1224
1225 if (!inode)
1226 return ERR_PTR(-ENOMEM);
1227
1228 inode->i_ino = get_next_ino();
1229 inode->i_mapping->a_ops = &anon_aops;
1230
1231 /*
1232 * Mark the inode dirty from the very beginning,
1233 * that way it will never be moved to the dirty
1234 * list because mark_inode_dirty() will think
1235 * that it already _is_ on the dirty list.
1236 */
1237 inode->i_state = I_DIRTY;
1238 inode->i_mode = S_IRUSR | S_IWUSR;
1239 inode->i_uid = current_fsuid();
1240 inode->i_gid = current_fsgid();
1241 inode->i_flags |= S_PRIVATE;
1242 inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
1243 return inode;
1244}
1245EXPORT_SYMBOL(alloc_anon_inode);
1246
1247/**
1248 * simple_nosetlease - generic helper for prohibiting leases
1249 * @filp: file pointer
1250 * @arg: type of lease to obtain
1251 * @flp: new lease supplied for insertion
1252 * @priv: private data for lm_setup operation
1253 *
1254 * Generic helper for filesystems that do not wish to allow leases to be set.
1255 * All arguments are ignored and it just returns -EINVAL.
1256 */
1257int
1258simple_nosetlease(struct file *filp, long arg, struct file_lock **flp,
1259 void **priv)
1260{
1261 return -EINVAL;
1262}
1263EXPORT_SYMBOL(simple_nosetlease);
1264
1265/**
1266 * simple_get_link - generic helper to get the target of "fast" symlinks
1267 * @dentry: not used here
1268 * @inode: the symlink inode
1269 * @done: not used here
1270 *
1271 * Generic helper for filesystems to use for symlink inodes where a pointer to
1272 * the symlink target is stored in ->i_link. NOTE: this isn't normally called,
1273 * since as an optimization the path lookup code uses any non-NULL ->i_link
1274 * directly, without calling ->get_link(). But ->get_link() still must be set,
1275 * to mark the inode_operations as being for a symlink.
1276 *
1277 * Return: the symlink target
1278 */
1279const char *simple_get_link(struct dentry *dentry, struct inode *inode,
1280 struct delayed_call *done)
1281{
1282 return inode->i_link;
1283}
1284EXPORT_SYMBOL(simple_get_link);
1285
1286const struct inode_operations simple_symlink_inode_operations = {
1287 .get_link = simple_get_link,
1288};
1289EXPORT_SYMBOL(simple_symlink_inode_operations);
1290
1291/*
1292 * Operations for a permanently empty directory.
1293 */
1294static struct dentry *empty_dir_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
1295{
1296 return ERR_PTR(-ENOENT);
1297}
1298
1299static int empty_dir_getattr(const struct path *path, struct kstat *stat,
1300 u32 request_mask, unsigned int query_flags)
1301{
1302 struct inode *inode = d_inode(path->dentry);
1303 generic_fillattr(inode, stat);
1304 return 0;
1305}
1306
1307static int empty_dir_setattr(struct dentry *dentry, struct iattr *attr)
1308{
1309 return -EPERM;
1310}
1311
1312static ssize_t empty_dir_listxattr(struct dentry *dentry, char *list, size_t size)
1313{
1314 return -EOPNOTSUPP;
1315}
1316
1317static const struct inode_operations empty_dir_inode_operations = {
1318 .lookup = empty_dir_lookup,
1319 .permission = generic_permission,
1320 .setattr = empty_dir_setattr,
1321 .getattr = empty_dir_getattr,
1322 .listxattr = empty_dir_listxattr,
1323};
1324
1325static loff_t empty_dir_llseek(struct file *file, loff_t offset, int whence)
1326{
1327 /* An empty directory has two entries . and .. at offsets 0 and 1 */
1328 return generic_file_llseek_size(file, offset, whence, 2, 2);
1329}
1330
1331static int empty_dir_readdir(struct file *file, struct dir_context *ctx)
1332{
1333 dir_emit_dots(file, ctx);
1334 return 0;
1335}
1336
1337static const struct file_operations empty_dir_operations = {
1338 .llseek = empty_dir_llseek,
1339 .read = generic_read_dir,
1340 .iterate_shared = empty_dir_readdir,
1341 .fsync = noop_fsync,
1342};
1343
1344
1345void make_empty_dir_inode(struct inode *inode)
1346{
1347 set_nlink(inode, 2);
1348 inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO;
1349 inode->i_uid = GLOBAL_ROOT_UID;
1350 inode->i_gid = GLOBAL_ROOT_GID;
1351 inode->i_rdev = 0;
1352 inode->i_size = 0;
1353 inode->i_blkbits = PAGE_SHIFT;
1354 inode->i_blocks = 0;
1355
1356 inode->i_op = &empty_dir_inode_operations;
1357 inode->i_opflags &= ~IOP_XATTR;
1358 inode->i_fop = &empty_dir_operations;
1359}
1360
1361bool is_empty_dir_inode(struct inode *inode)
1362{
1363 return (inode->i_fop == &empty_dir_operations) &&
1364 (inode->i_op == &empty_dir_inode_operations);
1365}
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/iversion.h>
19#include <linux/writeback.h>
20#include <linux/buffer_head.h> /* sync_mapping_buffers */
21#include <linux/fs_context.h>
22#include <linux/pseudo_fs.h>
23#include <linux/fsnotify.h>
24#include <linux/unicode.h>
25#include <linux/fscrypt.h>
26
27#include <linux/uaccess.h>
28
29#include "internal.h"
30
31int simple_getattr(struct mnt_idmap *idmap, const struct path *path,
32 struct kstat *stat, u32 request_mask,
33 unsigned int query_flags)
34{
35 struct inode *inode = d_inode(path->dentry);
36 generic_fillattr(&nop_mnt_idmap, request_mask, inode, stat);
37 stat->blocks = inode->i_mapping->nrpages << (PAGE_SHIFT - 9);
38 return 0;
39}
40EXPORT_SYMBOL(simple_getattr);
41
42int simple_statfs(struct dentry *dentry, struct kstatfs *buf)
43{
44 u64 id = huge_encode_dev(dentry->d_sb->s_dev);
45
46 buf->f_fsid = u64_to_fsid(id);
47 buf->f_type = dentry->d_sb->s_magic;
48 buf->f_bsize = PAGE_SIZE;
49 buf->f_namelen = NAME_MAX;
50 return 0;
51}
52EXPORT_SYMBOL(simple_statfs);
53
54/*
55 * Retaining negative dentries for an in-memory filesystem just wastes
56 * memory and lookup time: arrange for them to be deleted immediately.
57 */
58int always_delete_dentry(const struct dentry *dentry)
59{
60 return 1;
61}
62EXPORT_SYMBOL(always_delete_dentry);
63
64const struct dentry_operations simple_dentry_operations = {
65 .d_delete = always_delete_dentry,
66};
67EXPORT_SYMBOL(simple_dentry_operations);
68
69/*
70 * Lookup the data. This is trivial - if the dentry didn't already
71 * exist, we know it is negative. Set d_op to delete negative dentries.
72 */
73struct dentry *simple_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
74{
75 if (dentry->d_name.len > NAME_MAX)
76 return ERR_PTR(-ENAMETOOLONG);
77 if (!dentry->d_sb->s_d_op)
78 d_set_d_op(dentry, &simple_dentry_operations);
79 d_add(dentry, NULL);
80 return NULL;
81}
82EXPORT_SYMBOL(simple_lookup);
83
84int dcache_dir_open(struct inode *inode, struct file *file)
85{
86 file->private_data = d_alloc_cursor(file->f_path.dentry);
87
88 return file->private_data ? 0 : -ENOMEM;
89}
90EXPORT_SYMBOL(dcache_dir_open);
91
92int dcache_dir_close(struct inode *inode, struct file *file)
93{
94 dput(file->private_data);
95 return 0;
96}
97EXPORT_SYMBOL(dcache_dir_close);
98
99/* parent is locked at least shared */
100/*
101 * Returns an element of siblings' list.
102 * We are looking for <count>th positive after <p>; if
103 * found, dentry is grabbed and returned to caller.
104 * If no such element exists, NULL is returned.
105 */
106static struct dentry *scan_positives(struct dentry *cursor,
107 struct hlist_node **p,
108 loff_t count,
109 struct dentry *last)
110{
111 struct dentry *dentry = cursor->d_parent, *found = NULL;
112
113 spin_lock(&dentry->d_lock);
114 while (*p) {
115 struct dentry *d = hlist_entry(*p, struct dentry, d_sib);
116 p = &d->d_sib.next;
117 // we must at least skip cursors, to avoid livelocks
118 if (d->d_flags & DCACHE_DENTRY_CURSOR)
119 continue;
120 if (simple_positive(d) && !--count) {
121 spin_lock_nested(&d->d_lock, DENTRY_D_LOCK_NESTED);
122 if (simple_positive(d))
123 found = dget_dlock(d);
124 spin_unlock(&d->d_lock);
125 if (likely(found))
126 break;
127 count = 1;
128 }
129 if (need_resched()) {
130 if (!hlist_unhashed(&cursor->d_sib))
131 __hlist_del(&cursor->d_sib);
132 hlist_add_behind(&cursor->d_sib, &d->d_sib);
133 p = &cursor->d_sib.next;
134 spin_unlock(&dentry->d_lock);
135 cond_resched();
136 spin_lock(&dentry->d_lock);
137 }
138 }
139 spin_unlock(&dentry->d_lock);
140 dput(last);
141 return found;
142}
143
144loff_t dcache_dir_lseek(struct file *file, loff_t offset, int whence)
145{
146 struct dentry *dentry = file->f_path.dentry;
147 switch (whence) {
148 case 1:
149 offset += file->f_pos;
150 fallthrough;
151 case 0:
152 if (offset >= 0)
153 break;
154 fallthrough;
155 default:
156 return -EINVAL;
157 }
158 if (offset != file->f_pos) {
159 struct dentry *cursor = file->private_data;
160 struct dentry *to = NULL;
161
162 inode_lock_shared(dentry->d_inode);
163
164 if (offset > 2)
165 to = scan_positives(cursor, &dentry->d_children.first,
166 offset - 2, NULL);
167 spin_lock(&dentry->d_lock);
168 hlist_del_init(&cursor->d_sib);
169 if (to)
170 hlist_add_behind(&cursor->d_sib, &to->d_sib);
171 spin_unlock(&dentry->d_lock);
172 dput(to);
173
174 file->f_pos = offset;
175
176 inode_unlock_shared(dentry->d_inode);
177 }
178 return offset;
179}
180EXPORT_SYMBOL(dcache_dir_lseek);
181
182/*
183 * Directory is locked and all positive dentries in it are safe, since
184 * for ramfs-type trees they can't go away without unlink() or rmdir(),
185 * both impossible due to the lock on directory.
186 */
187
188int dcache_readdir(struct file *file, struct dir_context *ctx)
189{
190 struct dentry *dentry = file->f_path.dentry;
191 struct dentry *cursor = file->private_data;
192 struct dentry *next = NULL;
193 struct hlist_node **p;
194
195 if (!dir_emit_dots(file, ctx))
196 return 0;
197
198 if (ctx->pos == 2)
199 p = &dentry->d_children.first;
200 else
201 p = &cursor->d_sib.next;
202
203 while ((next = scan_positives(cursor, p, 1, next)) != NULL) {
204 if (!dir_emit(ctx, next->d_name.name, next->d_name.len,
205 d_inode(next)->i_ino,
206 fs_umode_to_dtype(d_inode(next)->i_mode)))
207 break;
208 ctx->pos++;
209 p = &next->d_sib.next;
210 }
211 spin_lock(&dentry->d_lock);
212 hlist_del_init(&cursor->d_sib);
213 if (next)
214 hlist_add_before(&cursor->d_sib, &next->d_sib);
215 spin_unlock(&dentry->d_lock);
216 dput(next);
217
218 return 0;
219}
220EXPORT_SYMBOL(dcache_readdir);
221
222ssize_t generic_read_dir(struct file *filp, char __user *buf, size_t siz, loff_t *ppos)
223{
224 return -EISDIR;
225}
226EXPORT_SYMBOL(generic_read_dir);
227
228const struct file_operations simple_dir_operations = {
229 .open = dcache_dir_open,
230 .release = dcache_dir_close,
231 .llseek = dcache_dir_lseek,
232 .read = generic_read_dir,
233 .iterate_shared = dcache_readdir,
234 .fsync = noop_fsync,
235};
236EXPORT_SYMBOL(simple_dir_operations);
237
238const struct inode_operations simple_dir_inode_operations = {
239 .lookup = simple_lookup,
240};
241EXPORT_SYMBOL(simple_dir_inode_operations);
242
243static void offset_set(struct dentry *dentry, u32 offset)
244{
245 dentry->d_fsdata = (void *)((uintptr_t)(offset));
246}
247
248static u32 dentry2offset(struct dentry *dentry)
249{
250 return (u32)((uintptr_t)(dentry->d_fsdata));
251}
252
253static struct lock_class_key simple_offset_xa_lock;
254
255/**
256 * simple_offset_init - initialize an offset_ctx
257 * @octx: directory offset map to be initialized
258 *
259 */
260void simple_offset_init(struct offset_ctx *octx)
261{
262 xa_init_flags(&octx->xa, XA_FLAGS_ALLOC1);
263 lockdep_set_class(&octx->xa.xa_lock, &simple_offset_xa_lock);
264
265 /* 0 is '.', 1 is '..', so always start with offset 2 */
266 octx->next_offset = 2;
267}
268
269/**
270 * simple_offset_add - Add an entry to a directory's offset map
271 * @octx: directory offset ctx to be updated
272 * @dentry: new dentry being added
273 *
274 * Returns zero on success. @so_ctx and the dentry offset are updated.
275 * Otherwise, a negative errno value is returned.
276 */
277int simple_offset_add(struct offset_ctx *octx, struct dentry *dentry)
278{
279 static const struct xa_limit limit = XA_LIMIT(2, U32_MAX);
280 u32 offset;
281 int ret;
282
283 if (dentry2offset(dentry) != 0)
284 return -EBUSY;
285
286 ret = xa_alloc_cyclic(&octx->xa, &offset, dentry, limit,
287 &octx->next_offset, GFP_KERNEL);
288 if (ret < 0)
289 return ret;
290
291 offset_set(dentry, offset);
292 return 0;
293}
294
295/**
296 * simple_offset_remove - Remove an entry to a directory's offset map
297 * @octx: directory offset ctx to be updated
298 * @dentry: dentry being removed
299 *
300 */
301void simple_offset_remove(struct offset_ctx *octx, struct dentry *dentry)
302{
303 u32 offset;
304
305 offset = dentry2offset(dentry);
306 if (offset == 0)
307 return;
308
309 xa_erase(&octx->xa, offset);
310 offset_set(dentry, 0);
311}
312
313/**
314 * simple_offset_rename_exchange - exchange rename with directory offsets
315 * @old_dir: parent of dentry being moved
316 * @old_dentry: dentry being moved
317 * @new_dir: destination parent
318 * @new_dentry: destination dentry
319 *
320 * Returns zero on success. Otherwise a negative errno is returned and the
321 * rename is rolled back.
322 */
323int simple_offset_rename_exchange(struct inode *old_dir,
324 struct dentry *old_dentry,
325 struct inode *new_dir,
326 struct dentry *new_dentry)
327{
328 struct offset_ctx *old_ctx = old_dir->i_op->get_offset_ctx(old_dir);
329 struct offset_ctx *new_ctx = new_dir->i_op->get_offset_ctx(new_dir);
330 u32 old_index = dentry2offset(old_dentry);
331 u32 new_index = dentry2offset(new_dentry);
332 int ret;
333
334 simple_offset_remove(old_ctx, old_dentry);
335 simple_offset_remove(new_ctx, new_dentry);
336
337 ret = simple_offset_add(new_ctx, old_dentry);
338 if (ret)
339 goto out_restore;
340
341 ret = simple_offset_add(old_ctx, new_dentry);
342 if (ret) {
343 simple_offset_remove(new_ctx, old_dentry);
344 goto out_restore;
345 }
346
347 ret = simple_rename_exchange(old_dir, old_dentry, new_dir, new_dentry);
348 if (ret) {
349 simple_offset_remove(new_ctx, old_dentry);
350 simple_offset_remove(old_ctx, new_dentry);
351 goto out_restore;
352 }
353 return 0;
354
355out_restore:
356 offset_set(old_dentry, old_index);
357 xa_store(&old_ctx->xa, old_index, old_dentry, GFP_KERNEL);
358 offset_set(new_dentry, new_index);
359 xa_store(&new_ctx->xa, new_index, new_dentry, GFP_KERNEL);
360 return ret;
361}
362
363/**
364 * simple_offset_destroy - Release offset map
365 * @octx: directory offset ctx that is about to be destroyed
366 *
367 * During fs teardown (eg. umount), a directory's offset map might still
368 * contain entries. xa_destroy() cleans out anything that remains.
369 */
370void simple_offset_destroy(struct offset_ctx *octx)
371{
372 xa_destroy(&octx->xa);
373}
374
375/**
376 * offset_dir_llseek - Advance the read position of a directory descriptor
377 * @file: an open directory whose position is to be updated
378 * @offset: a byte offset
379 * @whence: enumerator describing the starting position for this update
380 *
381 * SEEK_END, SEEK_DATA, and SEEK_HOLE are not supported for directories.
382 *
383 * Returns the updated read position if successful; otherwise a
384 * negative errno is returned and the read position remains unchanged.
385 */
386static loff_t offset_dir_llseek(struct file *file, loff_t offset, int whence)
387{
388 switch (whence) {
389 case SEEK_CUR:
390 offset += file->f_pos;
391 fallthrough;
392 case SEEK_SET:
393 if (offset >= 0)
394 break;
395 fallthrough;
396 default:
397 return -EINVAL;
398 }
399
400 /* In this case, ->private_data is protected by f_pos_lock */
401 file->private_data = NULL;
402 return vfs_setpos(file, offset, U32_MAX);
403}
404
405static struct dentry *offset_find_next(struct xa_state *xas)
406{
407 struct dentry *child, *found = NULL;
408
409 rcu_read_lock();
410 child = xas_next_entry(xas, U32_MAX);
411 if (!child)
412 goto out;
413 spin_lock(&child->d_lock);
414 if (simple_positive(child))
415 found = dget_dlock(child);
416 spin_unlock(&child->d_lock);
417out:
418 rcu_read_unlock();
419 return found;
420}
421
422static bool offset_dir_emit(struct dir_context *ctx, struct dentry *dentry)
423{
424 u32 offset = dentry2offset(dentry);
425 struct inode *inode = d_inode(dentry);
426
427 return ctx->actor(ctx, dentry->d_name.name, dentry->d_name.len, offset,
428 inode->i_ino, fs_umode_to_dtype(inode->i_mode));
429}
430
431static void *offset_iterate_dir(struct inode *inode, struct dir_context *ctx)
432{
433 struct offset_ctx *so_ctx = inode->i_op->get_offset_ctx(inode);
434 XA_STATE(xas, &so_ctx->xa, ctx->pos);
435 struct dentry *dentry;
436
437 while (true) {
438 dentry = offset_find_next(&xas);
439 if (!dentry)
440 return ERR_PTR(-ENOENT);
441
442 if (!offset_dir_emit(ctx, dentry)) {
443 dput(dentry);
444 break;
445 }
446
447 dput(dentry);
448 ctx->pos = xas.xa_index + 1;
449 }
450 return NULL;
451}
452
453/**
454 * offset_readdir - Emit entries starting at offset @ctx->pos
455 * @file: an open directory to iterate over
456 * @ctx: directory iteration context
457 *
458 * Caller must hold @file's i_rwsem to prevent insertion or removal of
459 * entries during this call.
460 *
461 * On entry, @ctx->pos contains an offset that represents the first entry
462 * to be read from the directory.
463 *
464 * The operation continues until there are no more entries to read, or
465 * until the ctx->actor indicates there is no more space in the caller's
466 * output buffer.
467 *
468 * On return, @ctx->pos contains an offset that will read the next entry
469 * in this directory when offset_readdir() is called again with @ctx.
470 *
471 * Return values:
472 * %0 - Complete
473 */
474static int offset_readdir(struct file *file, struct dir_context *ctx)
475{
476 struct dentry *dir = file->f_path.dentry;
477
478 lockdep_assert_held(&d_inode(dir)->i_rwsem);
479
480 if (!dir_emit_dots(file, ctx))
481 return 0;
482
483 /* In this case, ->private_data is protected by f_pos_lock */
484 if (ctx->pos == 2)
485 file->private_data = NULL;
486 else if (file->private_data == ERR_PTR(-ENOENT))
487 return 0;
488 file->private_data = offset_iterate_dir(d_inode(dir), ctx);
489 return 0;
490}
491
492const struct file_operations simple_offset_dir_operations = {
493 .llseek = offset_dir_llseek,
494 .iterate_shared = offset_readdir,
495 .read = generic_read_dir,
496 .fsync = noop_fsync,
497};
498
499static struct dentry *find_next_child(struct dentry *parent, struct dentry *prev)
500{
501 struct dentry *child = NULL, *d;
502
503 spin_lock(&parent->d_lock);
504 d = prev ? d_next_sibling(prev) : d_first_child(parent);
505 hlist_for_each_entry_from(d, d_sib) {
506 if (simple_positive(d)) {
507 spin_lock_nested(&d->d_lock, DENTRY_D_LOCK_NESTED);
508 if (simple_positive(d))
509 child = dget_dlock(d);
510 spin_unlock(&d->d_lock);
511 if (likely(child))
512 break;
513 }
514 }
515 spin_unlock(&parent->d_lock);
516 dput(prev);
517 return child;
518}
519
520void simple_recursive_removal(struct dentry *dentry,
521 void (*callback)(struct dentry *))
522{
523 struct dentry *this = dget(dentry);
524 while (true) {
525 struct dentry *victim = NULL, *child;
526 struct inode *inode = this->d_inode;
527
528 inode_lock(inode);
529 if (d_is_dir(this))
530 inode->i_flags |= S_DEAD;
531 while ((child = find_next_child(this, victim)) == NULL) {
532 // kill and ascend
533 // update metadata while it's still locked
534 inode_set_ctime_current(inode);
535 clear_nlink(inode);
536 inode_unlock(inode);
537 victim = this;
538 this = this->d_parent;
539 inode = this->d_inode;
540 inode_lock(inode);
541 if (simple_positive(victim)) {
542 d_invalidate(victim); // avoid lost mounts
543 if (d_is_dir(victim))
544 fsnotify_rmdir(inode, victim);
545 else
546 fsnotify_unlink(inode, victim);
547 if (callback)
548 callback(victim);
549 dput(victim); // unpin it
550 }
551 if (victim == dentry) {
552 inode_set_mtime_to_ts(inode,
553 inode_set_ctime_current(inode));
554 if (d_is_dir(dentry))
555 drop_nlink(inode);
556 inode_unlock(inode);
557 dput(dentry);
558 return;
559 }
560 }
561 inode_unlock(inode);
562 this = child;
563 }
564}
565EXPORT_SYMBOL(simple_recursive_removal);
566
567static const struct super_operations simple_super_operations = {
568 .statfs = simple_statfs,
569};
570
571static int pseudo_fs_fill_super(struct super_block *s, struct fs_context *fc)
572{
573 struct pseudo_fs_context *ctx = fc->fs_private;
574 struct inode *root;
575
576 s->s_maxbytes = MAX_LFS_FILESIZE;
577 s->s_blocksize = PAGE_SIZE;
578 s->s_blocksize_bits = PAGE_SHIFT;
579 s->s_magic = ctx->magic;
580 s->s_op = ctx->ops ?: &simple_super_operations;
581 s->s_xattr = ctx->xattr;
582 s->s_time_gran = 1;
583 root = new_inode(s);
584 if (!root)
585 return -ENOMEM;
586
587 /*
588 * since this is the first inode, make it number 1. New inodes created
589 * after this must take care not to collide with it (by passing
590 * max_reserved of 1 to iunique).
591 */
592 root->i_ino = 1;
593 root->i_mode = S_IFDIR | S_IRUSR | S_IWUSR;
594 simple_inode_init_ts(root);
595 s->s_root = d_make_root(root);
596 if (!s->s_root)
597 return -ENOMEM;
598 s->s_d_op = ctx->dops;
599 return 0;
600}
601
602static int pseudo_fs_get_tree(struct fs_context *fc)
603{
604 return get_tree_nodev(fc, pseudo_fs_fill_super);
605}
606
607static void pseudo_fs_free(struct fs_context *fc)
608{
609 kfree(fc->fs_private);
610}
611
612static const struct fs_context_operations pseudo_fs_context_ops = {
613 .free = pseudo_fs_free,
614 .get_tree = pseudo_fs_get_tree,
615};
616
617/*
618 * Common helper for pseudo-filesystems (sockfs, pipefs, bdev - stuff that
619 * will never be mountable)
620 */
621struct pseudo_fs_context *init_pseudo(struct fs_context *fc,
622 unsigned long magic)
623{
624 struct pseudo_fs_context *ctx;
625
626 ctx = kzalloc(sizeof(struct pseudo_fs_context), GFP_KERNEL);
627 if (likely(ctx)) {
628 ctx->magic = magic;
629 fc->fs_private = ctx;
630 fc->ops = &pseudo_fs_context_ops;
631 fc->sb_flags |= SB_NOUSER;
632 fc->global = true;
633 }
634 return ctx;
635}
636EXPORT_SYMBOL(init_pseudo);
637
638int simple_open(struct inode *inode, struct file *file)
639{
640 if (inode->i_private)
641 file->private_data = inode->i_private;
642 return 0;
643}
644EXPORT_SYMBOL(simple_open);
645
646int simple_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
647{
648 struct inode *inode = d_inode(old_dentry);
649
650 inode_set_mtime_to_ts(dir,
651 inode_set_ctime_to_ts(dir, inode_set_ctime_current(inode)));
652 inc_nlink(inode);
653 ihold(inode);
654 dget(dentry);
655 d_instantiate(dentry, inode);
656 return 0;
657}
658EXPORT_SYMBOL(simple_link);
659
660int simple_empty(struct dentry *dentry)
661{
662 struct dentry *child;
663 int ret = 0;
664
665 spin_lock(&dentry->d_lock);
666 hlist_for_each_entry(child, &dentry->d_children, d_sib) {
667 spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED);
668 if (simple_positive(child)) {
669 spin_unlock(&child->d_lock);
670 goto out;
671 }
672 spin_unlock(&child->d_lock);
673 }
674 ret = 1;
675out:
676 spin_unlock(&dentry->d_lock);
677 return ret;
678}
679EXPORT_SYMBOL(simple_empty);
680
681int simple_unlink(struct inode *dir, struct dentry *dentry)
682{
683 struct inode *inode = d_inode(dentry);
684
685 inode_set_mtime_to_ts(dir,
686 inode_set_ctime_to_ts(dir, inode_set_ctime_current(inode)));
687 drop_nlink(inode);
688 dput(dentry);
689 return 0;
690}
691EXPORT_SYMBOL(simple_unlink);
692
693int simple_rmdir(struct inode *dir, struct dentry *dentry)
694{
695 if (!simple_empty(dentry))
696 return -ENOTEMPTY;
697
698 drop_nlink(d_inode(dentry));
699 simple_unlink(dir, dentry);
700 drop_nlink(dir);
701 return 0;
702}
703EXPORT_SYMBOL(simple_rmdir);
704
705/**
706 * simple_rename_timestamp - update the various inode timestamps for rename
707 * @old_dir: old parent directory
708 * @old_dentry: dentry that is being renamed
709 * @new_dir: new parent directory
710 * @new_dentry: target for rename
711 *
712 * POSIX mandates that the old and new parent directories have their ctime and
713 * mtime updated, and that inodes of @old_dentry and @new_dentry (if any), have
714 * their ctime updated.
715 */
716void simple_rename_timestamp(struct inode *old_dir, struct dentry *old_dentry,
717 struct inode *new_dir, struct dentry *new_dentry)
718{
719 struct inode *newino = d_inode(new_dentry);
720
721 inode_set_mtime_to_ts(old_dir, inode_set_ctime_current(old_dir));
722 if (new_dir != old_dir)
723 inode_set_mtime_to_ts(new_dir,
724 inode_set_ctime_current(new_dir));
725 inode_set_ctime_current(d_inode(old_dentry));
726 if (newino)
727 inode_set_ctime_current(newino);
728}
729EXPORT_SYMBOL_GPL(simple_rename_timestamp);
730
731int simple_rename_exchange(struct inode *old_dir, struct dentry *old_dentry,
732 struct inode *new_dir, struct dentry *new_dentry)
733{
734 bool old_is_dir = d_is_dir(old_dentry);
735 bool new_is_dir = d_is_dir(new_dentry);
736
737 if (old_dir != new_dir && old_is_dir != new_is_dir) {
738 if (old_is_dir) {
739 drop_nlink(old_dir);
740 inc_nlink(new_dir);
741 } else {
742 drop_nlink(new_dir);
743 inc_nlink(old_dir);
744 }
745 }
746 simple_rename_timestamp(old_dir, old_dentry, new_dir, new_dentry);
747 return 0;
748}
749EXPORT_SYMBOL_GPL(simple_rename_exchange);
750
751int simple_rename(struct mnt_idmap *idmap, struct inode *old_dir,
752 struct dentry *old_dentry, struct inode *new_dir,
753 struct dentry *new_dentry, unsigned int flags)
754{
755 int they_are_dirs = d_is_dir(old_dentry);
756
757 if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE))
758 return -EINVAL;
759
760 if (flags & RENAME_EXCHANGE)
761 return simple_rename_exchange(old_dir, old_dentry, new_dir, new_dentry);
762
763 if (!simple_empty(new_dentry))
764 return -ENOTEMPTY;
765
766 if (d_really_is_positive(new_dentry)) {
767 simple_unlink(new_dir, new_dentry);
768 if (they_are_dirs) {
769 drop_nlink(d_inode(new_dentry));
770 drop_nlink(old_dir);
771 }
772 } else if (they_are_dirs) {
773 drop_nlink(old_dir);
774 inc_nlink(new_dir);
775 }
776
777 simple_rename_timestamp(old_dir, old_dentry, new_dir, new_dentry);
778 return 0;
779}
780EXPORT_SYMBOL(simple_rename);
781
782/**
783 * simple_setattr - setattr for simple filesystem
784 * @idmap: idmap of the target mount
785 * @dentry: dentry
786 * @iattr: iattr structure
787 *
788 * Returns 0 on success, -error on failure.
789 *
790 * simple_setattr is a simple ->setattr implementation without a proper
791 * implementation of size changes.
792 *
793 * It can either be used for in-memory filesystems or special files
794 * on simple regular filesystems. Anything that needs to change on-disk
795 * or wire state on size changes needs its own setattr method.
796 */
797int simple_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
798 struct iattr *iattr)
799{
800 struct inode *inode = d_inode(dentry);
801 int error;
802
803 error = setattr_prepare(idmap, dentry, iattr);
804 if (error)
805 return error;
806
807 if (iattr->ia_valid & ATTR_SIZE)
808 truncate_setsize(inode, iattr->ia_size);
809 setattr_copy(idmap, inode, iattr);
810 mark_inode_dirty(inode);
811 return 0;
812}
813EXPORT_SYMBOL(simple_setattr);
814
815static int simple_read_folio(struct file *file, struct folio *folio)
816{
817 folio_zero_range(folio, 0, folio_size(folio));
818 flush_dcache_folio(folio);
819 folio_mark_uptodate(folio);
820 folio_unlock(folio);
821 return 0;
822}
823
824int simple_write_begin(struct file *file, struct address_space *mapping,
825 loff_t pos, unsigned len,
826 struct page **pagep, void **fsdata)
827{
828 struct folio *folio;
829
830 folio = __filemap_get_folio(mapping, pos / PAGE_SIZE, FGP_WRITEBEGIN,
831 mapping_gfp_mask(mapping));
832 if (IS_ERR(folio))
833 return PTR_ERR(folio);
834
835 *pagep = &folio->page;
836
837 if (!folio_test_uptodate(folio) && (len != folio_size(folio))) {
838 size_t from = offset_in_folio(folio, pos);
839
840 folio_zero_segments(folio, 0, from,
841 from + len, folio_size(folio));
842 }
843 return 0;
844}
845EXPORT_SYMBOL(simple_write_begin);
846
847/**
848 * simple_write_end - .write_end helper for non-block-device FSes
849 * @file: See .write_end of address_space_operations
850 * @mapping: "
851 * @pos: "
852 * @len: "
853 * @copied: "
854 * @page: "
855 * @fsdata: "
856 *
857 * simple_write_end does the minimum needed for updating a page after writing is
858 * done. It has the same API signature as the .write_end of
859 * address_space_operations vector. So it can just be set onto .write_end for
860 * FSes that don't need any other processing. i_mutex is assumed to be held.
861 * Block based filesystems should use generic_write_end().
862 * NOTE: Even though i_size might get updated by this function, mark_inode_dirty
863 * is not called, so a filesystem that actually does store data in .write_inode
864 * should extend on what's done here with a call to mark_inode_dirty() in the
865 * case that i_size has changed.
866 *
867 * Use *ONLY* with simple_read_folio()
868 */
869static int simple_write_end(struct file *file, struct address_space *mapping,
870 loff_t pos, unsigned len, unsigned copied,
871 struct page *page, void *fsdata)
872{
873 struct folio *folio = page_folio(page);
874 struct inode *inode = folio->mapping->host;
875 loff_t last_pos = pos + copied;
876
877 /* zero the stale part of the folio if we did a short copy */
878 if (!folio_test_uptodate(folio)) {
879 if (copied < len) {
880 size_t from = offset_in_folio(folio, pos);
881
882 folio_zero_range(folio, from + copied, len - copied);
883 }
884 folio_mark_uptodate(folio);
885 }
886 /*
887 * No need to use i_size_read() here, the i_size
888 * cannot change under us because we hold the i_mutex.
889 */
890 if (last_pos > inode->i_size)
891 i_size_write(inode, last_pos);
892
893 folio_mark_dirty(folio);
894 folio_unlock(folio);
895 folio_put(folio);
896
897 return copied;
898}
899
900/*
901 * Provides ramfs-style behavior: data in the pagecache, but no writeback.
902 */
903const struct address_space_operations ram_aops = {
904 .read_folio = simple_read_folio,
905 .write_begin = simple_write_begin,
906 .write_end = simple_write_end,
907 .dirty_folio = noop_dirty_folio,
908};
909EXPORT_SYMBOL(ram_aops);
910
911/*
912 * the inodes created here are not hashed. If you use iunique to generate
913 * unique inode values later for this filesystem, then you must take care
914 * to pass it an appropriate max_reserved value to avoid collisions.
915 */
916int simple_fill_super(struct super_block *s, unsigned long magic,
917 const struct tree_descr *files)
918{
919 struct inode *inode;
920 struct dentry *dentry;
921 int i;
922
923 s->s_blocksize = PAGE_SIZE;
924 s->s_blocksize_bits = PAGE_SHIFT;
925 s->s_magic = magic;
926 s->s_op = &simple_super_operations;
927 s->s_time_gran = 1;
928
929 inode = new_inode(s);
930 if (!inode)
931 return -ENOMEM;
932 /*
933 * because the root inode is 1, the files array must not contain an
934 * entry at index 1
935 */
936 inode->i_ino = 1;
937 inode->i_mode = S_IFDIR | 0755;
938 simple_inode_init_ts(inode);
939 inode->i_op = &simple_dir_inode_operations;
940 inode->i_fop = &simple_dir_operations;
941 set_nlink(inode, 2);
942 s->s_root = d_make_root(inode);
943 if (!s->s_root)
944 return -ENOMEM;
945 for (i = 0; !files->name || files->name[0]; i++, files++) {
946 if (!files->name)
947 continue;
948
949 /* warn if it tries to conflict with the root inode */
950 if (unlikely(i == 1))
951 printk(KERN_WARNING "%s: %s passed in a files array"
952 "with an index of 1!\n", __func__,
953 s->s_type->name);
954
955 dentry = d_alloc_name(s->s_root, files->name);
956 if (!dentry)
957 return -ENOMEM;
958 inode = new_inode(s);
959 if (!inode) {
960 dput(dentry);
961 return -ENOMEM;
962 }
963 inode->i_mode = S_IFREG | files->mode;
964 simple_inode_init_ts(inode);
965 inode->i_fop = files->ops;
966 inode->i_ino = i;
967 d_add(dentry, inode);
968 }
969 return 0;
970}
971EXPORT_SYMBOL(simple_fill_super);
972
973static DEFINE_SPINLOCK(pin_fs_lock);
974
975int simple_pin_fs(struct file_system_type *type, struct vfsmount **mount, int *count)
976{
977 struct vfsmount *mnt = NULL;
978 spin_lock(&pin_fs_lock);
979 if (unlikely(!*mount)) {
980 spin_unlock(&pin_fs_lock);
981 mnt = vfs_kern_mount(type, SB_KERNMOUNT, type->name, NULL);
982 if (IS_ERR(mnt))
983 return PTR_ERR(mnt);
984 spin_lock(&pin_fs_lock);
985 if (!*mount)
986 *mount = mnt;
987 }
988 mntget(*mount);
989 ++*count;
990 spin_unlock(&pin_fs_lock);
991 mntput(mnt);
992 return 0;
993}
994EXPORT_SYMBOL(simple_pin_fs);
995
996void simple_release_fs(struct vfsmount **mount, int *count)
997{
998 struct vfsmount *mnt;
999 spin_lock(&pin_fs_lock);
1000 mnt = *mount;
1001 if (!--*count)
1002 *mount = NULL;
1003 spin_unlock(&pin_fs_lock);
1004 mntput(mnt);
1005}
1006EXPORT_SYMBOL(simple_release_fs);
1007
1008/**
1009 * simple_read_from_buffer - copy data from the buffer to user space
1010 * @to: the user space buffer to read to
1011 * @count: the maximum number of bytes to read
1012 * @ppos: the current position in the buffer
1013 * @from: the buffer to read from
1014 * @available: the size of the buffer
1015 *
1016 * The simple_read_from_buffer() function reads up to @count bytes from the
1017 * buffer @from at offset @ppos into the user space address starting at @to.
1018 *
1019 * On success, the number of bytes read is returned and the offset @ppos is
1020 * advanced by this number, or negative value is returned on error.
1021 **/
1022ssize_t simple_read_from_buffer(void __user *to, size_t count, loff_t *ppos,
1023 const void *from, size_t available)
1024{
1025 loff_t pos = *ppos;
1026 size_t ret;
1027
1028 if (pos < 0)
1029 return -EINVAL;
1030 if (pos >= available || !count)
1031 return 0;
1032 if (count > available - pos)
1033 count = available - pos;
1034 ret = copy_to_user(to, from + pos, count);
1035 if (ret == count)
1036 return -EFAULT;
1037 count -= ret;
1038 *ppos = pos + count;
1039 return count;
1040}
1041EXPORT_SYMBOL(simple_read_from_buffer);
1042
1043/**
1044 * simple_write_to_buffer - copy data from user space to the buffer
1045 * @to: the buffer to write to
1046 * @available: the size of the buffer
1047 * @ppos: the current position in the buffer
1048 * @from: the user space buffer to read from
1049 * @count: the maximum number of bytes to read
1050 *
1051 * The simple_write_to_buffer() function reads up to @count bytes from the user
1052 * space address starting at @from into the buffer @to at offset @ppos.
1053 *
1054 * On success, the number of bytes written is returned and the offset @ppos is
1055 * advanced by this number, or negative value is returned on error.
1056 **/
1057ssize_t simple_write_to_buffer(void *to, size_t available, loff_t *ppos,
1058 const void __user *from, size_t count)
1059{
1060 loff_t pos = *ppos;
1061 size_t res;
1062
1063 if (pos < 0)
1064 return -EINVAL;
1065 if (pos >= available || !count)
1066 return 0;
1067 if (count > available - pos)
1068 count = available - pos;
1069 res = copy_from_user(to + pos, from, count);
1070 if (res == count)
1071 return -EFAULT;
1072 count -= res;
1073 *ppos = pos + count;
1074 return count;
1075}
1076EXPORT_SYMBOL(simple_write_to_buffer);
1077
1078/**
1079 * memory_read_from_buffer - copy data from the buffer
1080 * @to: the kernel space buffer to read to
1081 * @count: the maximum number of bytes to read
1082 * @ppos: the current position in the buffer
1083 * @from: the buffer to read from
1084 * @available: the size of the buffer
1085 *
1086 * The memory_read_from_buffer() function reads up to @count bytes from the
1087 * buffer @from at offset @ppos into the kernel space address starting at @to.
1088 *
1089 * On success, the number of bytes read is returned and the offset @ppos is
1090 * advanced by this number, or negative value is returned on error.
1091 **/
1092ssize_t memory_read_from_buffer(void *to, size_t count, loff_t *ppos,
1093 const void *from, size_t available)
1094{
1095 loff_t pos = *ppos;
1096
1097 if (pos < 0)
1098 return -EINVAL;
1099 if (pos >= available)
1100 return 0;
1101 if (count > available - pos)
1102 count = available - pos;
1103 memcpy(to, from + pos, count);
1104 *ppos = pos + count;
1105
1106 return count;
1107}
1108EXPORT_SYMBOL(memory_read_from_buffer);
1109
1110/*
1111 * Transaction based IO.
1112 * The file expects a single write which triggers the transaction, and then
1113 * possibly a read which collects the result - which is stored in a
1114 * file-local buffer.
1115 */
1116
1117void simple_transaction_set(struct file *file, size_t n)
1118{
1119 struct simple_transaction_argresp *ar = file->private_data;
1120
1121 BUG_ON(n > SIMPLE_TRANSACTION_LIMIT);
1122
1123 /*
1124 * The barrier ensures that ar->size will really remain zero until
1125 * ar->data is ready for reading.
1126 */
1127 smp_mb();
1128 ar->size = n;
1129}
1130EXPORT_SYMBOL(simple_transaction_set);
1131
1132char *simple_transaction_get(struct file *file, const char __user *buf, size_t size)
1133{
1134 struct simple_transaction_argresp *ar;
1135 static DEFINE_SPINLOCK(simple_transaction_lock);
1136
1137 if (size > SIMPLE_TRANSACTION_LIMIT - 1)
1138 return ERR_PTR(-EFBIG);
1139
1140 ar = (struct simple_transaction_argresp *)get_zeroed_page(GFP_KERNEL);
1141 if (!ar)
1142 return ERR_PTR(-ENOMEM);
1143
1144 spin_lock(&simple_transaction_lock);
1145
1146 /* only one write allowed per open */
1147 if (file->private_data) {
1148 spin_unlock(&simple_transaction_lock);
1149 free_page((unsigned long)ar);
1150 return ERR_PTR(-EBUSY);
1151 }
1152
1153 file->private_data = ar;
1154
1155 spin_unlock(&simple_transaction_lock);
1156
1157 if (copy_from_user(ar->data, buf, size))
1158 return ERR_PTR(-EFAULT);
1159
1160 return ar->data;
1161}
1162EXPORT_SYMBOL(simple_transaction_get);
1163
1164ssize_t simple_transaction_read(struct file *file, char __user *buf, size_t size, loff_t *pos)
1165{
1166 struct simple_transaction_argresp *ar = file->private_data;
1167
1168 if (!ar)
1169 return 0;
1170 return simple_read_from_buffer(buf, size, pos, ar->data, ar->size);
1171}
1172EXPORT_SYMBOL(simple_transaction_read);
1173
1174int simple_transaction_release(struct inode *inode, struct file *file)
1175{
1176 free_page((unsigned long)file->private_data);
1177 return 0;
1178}
1179EXPORT_SYMBOL(simple_transaction_release);
1180
1181/* Simple attribute files */
1182
1183struct simple_attr {
1184 int (*get)(void *, u64 *);
1185 int (*set)(void *, u64);
1186 char get_buf[24]; /* enough to store a u64 and "\n\0" */
1187 char set_buf[24];
1188 void *data;
1189 const char *fmt; /* format for read operation */
1190 struct mutex mutex; /* protects access to these buffers */
1191};
1192
1193/* simple_attr_open is called by an actual attribute open file operation
1194 * to set the attribute specific access operations. */
1195int simple_attr_open(struct inode *inode, struct file *file,
1196 int (*get)(void *, u64 *), int (*set)(void *, u64),
1197 const char *fmt)
1198{
1199 struct simple_attr *attr;
1200
1201 attr = kzalloc(sizeof(*attr), GFP_KERNEL);
1202 if (!attr)
1203 return -ENOMEM;
1204
1205 attr->get = get;
1206 attr->set = set;
1207 attr->data = inode->i_private;
1208 attr->fmt = fmt;
1209 mutex_init(&attr->mutex);
1210
1211 file->private_data = attr;
1212
1213 return nonseekable_open(inode, file);
1214}
1215EXPORT_SYMBOL_GPL(simple_attr_open);
1216
1217int simple_attr_release(struct inode *inode, struct file *file)
1218{
1219 kfree(file->private_data);
1220 return 0;
1221}
1222EXPORT_SYMBOL_GPL(simple_attr_release); /* GPL-only? This? Really? */
1223
1224/* read from the buffer that is filled with the get function */
1225ssize_t simple_attr_read(struct file *file, char __user *buf,
1226 size_t len, loff_t *ppos)
1227{
1228 struct simple_attr *attr;
1229 size_t size;
1230 ssize_t ret;
1231
1232 attr = file->private_data;
1233
1234 if (!attr->get)
1235 return -EACCES;
1236
1237 ret = mutex_lock_interruptible(&attr->mutex);
1238 if (ret)
1239 return ret;
1240
1241 if (*ppos && attr->get_buf[0]) {
1242 /* continued read */
1243 size = strlen(attr->get_buf);
1244 } else {
1245 /* first read */
1246 u64 val;
1247 ret = attr->get(attr->data, &val);
1248 if (ret)
1249 goto out;
1250
1251 size = scnprintf(attr->get_buf, sizeof(attr->get_buf),
1252 attr->fmt, (unsigned long long)val);
1253 }
1254
1255 ret = simple_read_from_buffer(buf, len, ppos, attr->get_buf, size);
1256out:
1257 mutex_unlock(&attr->mutex);
1258 return ret;
1259}
1260EXPORT_SYMBOL_GPL(simple_attr_read);
1261
1262/* interpret the buffer as a number to call the set function with */
1263static ssize_t simple_attr_write_xsigned(struct file *file, const char __user *buf,
1264 size_t len, loff_t *ppos, bool is_signed)
1265{
1266 struct simple_attr *attr;
1267 unsigned long long val;
1268 size_t size;
1269 ssize_t ret;
1270
1271 attr = file->private_data;
1272 if (!attr->set)
1273 return -EACCES;
1274
1275 ret = mutex_lock_interruptible(&attr->mutex);
1276 if (ret)
1277 return ret;
1278
1279 ret = -EFAULT;
1280 size = min(sizeof(attr->set_buf) - 1, len);
1281 if (copy_from_user(attr->set_buf, buf, size))
1282 goto out;
1283
1284 attr->set_buf[size] = '\0';
1285 if (is_signed)
1286 ret = kstrtoll(attr->set_buf, 0, &val);
1287 else
1288 ret = kstrtoull(attr->set_buf, 0, &val);
1289 if (ret)
1290 goto out;
1291 ret = attr->set(attr->data, val);
1292 if (ret == 0)
1293 ret = len; /* on success, claim we got the whole input */
1294out:
1295 mutex_unlock(&attr->mutex);
1296 return ret;
1297}
1298
1299ssize_t simple_attr_write(struct file *file, const char __user *buf,
1300 size_t len, loff_t *ppos)
1301{
1302 return simple_attr_write_xsigned(file, buf, len, ppos, false);
1303}
1304EXPORT_SYMBOL_GPL(simple_attr_write);
1305
1306ssize_t simple_attr_write_signed(struct file *file, const char __user *buf,
1307 size_t len, loff_t *ppos)
1308{
1309 return simple_attr_write_xsigned(file, buf, len, ppos, true);
1310}
1311EXPORT_SYMBOL_GPL(simple_attr_write_signed);
1312
1313/**
1314 * generic_encode_ino32_fh - generic export_operations->encode_fh function
1315 * @inode: the object to encode
1316 * @fh: where to store the file handle fragment
1317 * @max_len: maximum length to store there (in 4 byte units)
1318 * @parent: parent directory inode, if wanted
1319 *
1320 * This generic encode_fh function assumes that the 32 inode number
1321 * is suitable for locating an inode, and that the generation number
1322 * can be used to check that it is still valid. It places them in the
1323 * filehandle fragment where export_decode_fh expects to find them.
1324 */
1325int generic_encode_ino32_fh(struct inode *inode, __u32 *fh, int *max_len,
1326 struct inode *parent)
1327{
1328 struct fid *fid = (void *)fh;
1329 int len = *max_len;
1330 int type = FILEID_INO32_GEN;
1331
1332 if (parent && (len < 4)) {
1333 *max_len = 4;
1334 return FILEID_INVALID;
1335 } else if (len < 2) {
1336 *max_len = 2;
1337 return FILEID_INVALID;
1338 }
1339
1340 len = 2;
1341 fid->i32.ino = inode->i_ino;
1342 fid->i32.gen = inode->i_generation;
1343 if (parent) {
1344 fid->i32.parent_ino = parent->i_ino;
1345 fid->i32.parent_gen = parent->i_generation;
1346 len = 4;
1347 type = FILEID_INO32_GEN_PARENT;
1348 }
1349 *max_len = len;
1350 return type;
1351}
1352EXPORT_SYMBOL_GPL(generic_encode_ino32_fh);
1353
1354/**
1355 * generic_fh_to_dentry - generic helper for the fh_to_dentry export operation
1356 * @sb: filesystem to do the file handle conversion on
1357 * @fid: file handle to convert
1358 * @fh_len: length of the file handle in bytes
1359 * @fh_type: type of file handle
1360 * @get_inode: filesystem callback to retrieve inode
1361 *
1362 * This function decodes @fid as long as it has one of the well-known
1363 * Linux filehandle types and calls @get_inode on it to retrieve the
1364 * inode for the object specified in the file handle.
1365 */
1366struct dentry *generic_fh_to_dentry(struct super_block *sb, struct fid *fid,
1367 int fh_len, int fh_type, struct inode *(*get_inode)
1368 (struct super_block *sb, u64 ino, u32 gen))
1369{
1370 struct inode *inode = NULL;
1371
1372 if (fh_len < 2)
1373 return NULL;
1374
1375 switch (fh_type) {
1376 case FILEID_INO32_GEN:
1377 case FILEID_INO32_GEN_PARENT:
1378 inode = get_inode(sb, fid->i32.ino, fid->i32.gen);
1379 break;
1380 }
1381
1382 return d_obtain_alias(inode);
1383}
1384EXPORT_SYMBOL_GPL(generic_fh_to_dentry);
1385
1386/**
1387 * generic_fh_to_parent - generic helper for the fh_to_parent export operation
1388 * @sb: filesystem to do the file handle conversion on
1389 * @fid: file handle to convert
1390 * @fh_len: length of the file handle in bytes
1391 * @fh_type: type of file handle
1392 * @get_inode: filesystem callback to retrieve inode
1393 *
1394 * This function decodes @fid as long as it has one of the well-known
1395 * Linux filehandle types and calls @get_inode on it to retrieve the
1396 * inode for the _parent_ object specified in the file handle if it
1397 * is specified in the file handle, or NULL otherwise.
1398 */
1399struct dentry *generic_fh_to_parent(struct super_block *sb, struct fid *fid,
1400 int fh_len, int fh_type, struct inode *(*get_inode)
1401 (struct super_block *sb, u64 ino, u32 gen))
1402{
1403 struct inode *inode = NULL;
1404
1405 if (fh_len <= 2)
1406 return NULL;
1407
1408 switch (fh_type) {
1409 case FILEID_INO32_GEN_PARENT:
1410 inode = get_inode(sb, fid->i32.parent_ino,
1411 (fh_len > 3 ? fid->i32.parent_gen : 0));
1412 break;
1413 }
1414
1415 return d_obtain_alias(inode);
1416}
1417EXPORT_SYMBOL_GPL(generic_fh_to_parent);
1418
1419/**
1420 * __generic_file_fsync - generic fsync implementation for simple filesystems
1421 *
1422 * @file: file to synchronize
1423 * @start: start offset in bytes
1424 * @end: end offset in bytes (inclusive)
1425 * @datasync: only synchronize essential metadata if true
1426 *
1427 * This is a generic implementation of the fsync method for simple
1428 * filesystems which track all non-inode metadata in the buffers list
1429 * hanging off the address_space structure.
1430 */
1431int __generic_file_fsync(struct file *file, loff_t start, loff_t end,
1432 int datasync)
1433{
1434 struct inode *inode = file->f_mapping->host;
1435 int err;
1436 int ret;
1437
1438 err = file_write_and_wait_range(file, start, end);
1439 if (err)
1440 return err;
1441
1442 inode_lock(inode);
1443 ret = sync_mapping_buffers(inode->i_mapping);
1444 if (!(inode->i_state & I_DIRTY_ALL))
1445 goto out;
1446 if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
1447 goto out;
1448
1449 err = sync_inode_metadata(inode, 1);
1450 if (ret == 0)
1451 ret = err;
1452
1453out:
1454 inode_unlock(inode);
1455 /* check and advance again to catch errors after syncing out buffers */
1456 err = file_check_and_advance_wb_err(file);
1457 if (ret == 0)
1458 ret = err;
1459 return ret;
1460}
1461EXPORT_SYMBOL(__generic_file_fsync);
1462
1463/**
1464 * generic_file_fsync - generic fsync implementation for simple filesystems
1465 * with flush
1466 * @file: file to synchronize
1467 * @start: start offset in bytes
1468 * @end: end offset in bytes (inclusive)
1469 * @datasync: only synchronize essential metadata if true
1470 *
1471 */
1472
1473int generic_file_fsync(struct file *file, loff_t start, loff_t end,
1474 int datasync)
1475{
1476 struct inode *inode = file->f_mapping->host;
1477 int err;
1478
1479 err = __generic_file_fsync(file, start, end, datasync);
1480 if (err)
1481 return err;
1482 return blkdev_issue_flush(inode->i_sb->s_bdev);
1483}
1484EXPORT_SYMBOL(generic_file_fsync);
1485
1486/**
1487 * generic_check_addressable - Check addressability of file system
1488 * @blocksize_bits: log of file system block size
1489 * @num_blocks: number of blocks in file system
1490 *
1491 * Determine whether a file system with @num_blocks blocks (and a
1492 * block size of 2**@blocksize_bits) is addressable by the sector_t
1493 * and page cache of the system. Return 0 if so and -EFBIG otherwise.
1494 */
1495int generic_check_addressable(unsigned blocksize_bits, u64 num_blocks)
1496{
1497 u64 last_fs_block = num_blocks - 1;
1498 u64 last_fs_page =
1499 last_fs_block >> (PAGE_SHIFT - blocksize_bits);
1500
1501 if (unlikely(num_blocks == 0))
1502 return 0;
1503
1504 if ((blocksize_bits < 9) || (blocksize_bits > PAGE_SHIFT))
1505 return -EINVAL;
1506
1507 if ((last_fs_block > (sector_t)(~0ULL) >> (blocksize_bits - 9)) ||
1508 (last_fs_page > (pgoff_t)(~0ULL))) {
1509 return -EFBIG;
1510 }
1511 return 0;
1512}
1513EXPORT_SYMBOL(generic_check_addressable);
1514
1515/*
1516 * No-op implementation of ->fsync for in-memory filesystems.
1517 */
1518int noop_fsync(struct file *file, loff_t start, loff_t end, int datasync)
1519{
1520 return 0;
1521}
1522EXPORT_SYMBOL(noop_fsync);
1523
1524ssize_t noop_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
1525{
1526 /*
1527 * iomap based filesystems support direct I/O without need for
1528 * this callback. However, it still needs to be set in
1529 * inode->a_ops so that open/fcntl know that direct I/O is
1530 * generally supported.
1531 */
1532 return -EINVAL;
1533}
1534EXPORT_SYMBOL_GPL(noop_direct_IO);
1535
1536/* Because kfree isn't assignment-compatible with void(void*) ;-/ */
1537void kfree_link(void *p)
1538{
1539 kfree(p);
1540}
1541EXPORT_SYMBOL(kfree_link);
1542
1543struct inode *alloc_anon_inode(struct super_block *s)
1544{
1545 static const struct address_space_operations anon_aops = {
1546 .dirty_folio = noop_dirty_folio,
1547 };
1548 struct inode *inode = new_inode_pseudo(s);
1549
1550 if (!inode)
1551 return ERR_PTR(-ENOMEM);
1552
1553 inode->i_ino = get_next_ino();
1554 inode->i_mapping->a_ops = &anon_aops;
1555
1556 /*
1557 * Mark the inode dirty from the very beginning,
1558 * that way it will never be moved to the dirty
1559 * list because mark_inode_dirty() will think
1560 * that it already _is_ on the dirty list.
1561 */
1562 inode->i_state = I_DIRTY;
1563 inode->i_mode = S_IRUSR | S_IWUSR;
1564 inode->i_uid = current_fsuid();
1565 inode->i_gid = current_fsgid();
1566 inode->i_flags |= S_PRIVATE;
1567 simple_inode_init_ts(inode);
1568 return inode;
1569}
1570EXPORT_SYMBOL(alloc_anon_inode);
1571
1572/**
1573 * simple_nosetlease - generic helper for prohibiting leases
1574 * @filp: file pointer
1575 * @arg: type of lease to obtain
1576 * @flp: new lease supplied for insertion
1577 * @priv: private data for lm_setup operation
1578 *
1579 * Generic helper for filesystems that do not wish to allow leases to be set.
1580 * All arguments are ignored and it just returns -EINVAL.
1581 */
1582int
1583simple_nosetlease(struct file *filp, int arg, struct file_lock **flp,
1584 void **priv)
1585{
1586 return -EINVAL;
1587}
1588EXPORT_SYMBOL(simple_nosetlease);
1589
1590/**
1591 * simple_get_link - generic helper to get the target of "fast" symlinks
1592 * @dentry: not used here
1593 * @inode: the symlink inode
1594 * @done: not used here
1595 *
1596 * Generic helper for filesystems to use for symlink inodes where a pointer to
1597 * the symlink target is stored in ->i_link. NOTE: this isn't normally called,
1598 * since as an optimization the path lookup code uses any non-NULL ->i_link
1599 * directly, without calling ->get_link(). But ->get_link() still must be set,
1600 * to mark the inode_operations as being for a symlink.
1601 *
1602 * Return: the symlink target
1603 */
1604const char *simple_get_link(struct dentry *dentry, struct inode *inode,
1605 struct delayed_call *done)
1606{
1607 return inode->i_link;
1608}
1609EXPORT_SYMBOL(simple_get_link);
1610
1611const struct inode_operations simple_symlink_inode_operations = {
1612 .get_link = simple_get_link,
1613};
1614EXPORT_SYMBOL(simple_symlink_inode_operations);
1615
1616/*
1617 * Operations for a permanently empty directory.
1618 */
1619static struct dentry *empty_dir_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
1620{
1621 return ERR_PTR(-ENOENT);
1622}
1623
1624static int empty_dir_getattr(struct mnt_idmap *idmap,
1625 const struct path *path, struct kstat *stat,
1626 u32 request_mask, unsigned int query_flags)
1627{
1628 struct inode *inode = d_inode(path->dentry);
1629 generic_fillattr(&nop_mnt_idmap, request_mask, inode, stat);
1630 return 0;
1631}
1632
1633static int empty_dir_setattr(struct mnt_idmap *idmap,
1634 struct dentry *dentry, struct iattr *attr)
1635{
1636 return -EPERM;
1637}
1638
1639static ssize_t empty_dir_listxattr(struct dentry *dentry, char *list, size_t size)
1640{
1641 return -EOPNOTSUPP;
1642}
1643
1644static const struct inode_operations empty_dir_inode_operations = {
1645 .lookup = empty_dir_lookup,
1646 .permission = generic_permission,
1647 .setattr = empty_dir_setattr,
1648 .getattr = empty_dir_getattr,
1649 .listxattr = empty_dir_listxattr,
1650};
1651
1652static loff_t empty_dir_llseek(struct file *file, loff_t offset, int whence)
1653{
1654 /* An empty directory has two entries . and .. at offsets 0 and 1 */
1655 return generic_file_llseek_size(file, offset, whence, 2, 2);
1656}
1657
1658static int empty_dir_readdir(struct file *file, struct dir_context *ctx)
1659{
1660 dir_emit_dots(file, ctx);
1661 return 0;
1662}
1663
1664static const struct file_operations empty_dir_operations = {
1665 .llseek = empty_dir_llseek,
1666 .read = generic_read_dir,
1667 .iterate_shared = empty_dir_readdir,
1668 .fsync = noop_fsync,
1669};
1670
1671
1672void make_empty_dir_inode(struct inode *inode)
1673{
1674 set_nlink(inode, 2);
1675 inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO;
1676 inode->i_uid = GLOBAL_ROOT_UID;
1677 inode->i_gid = GLOBAL_ROOT_GID;
1678 inode->i_rdev = 0;
1679 inode->i_size = 0;
1680 inode->i_blkbits = PAGE_SHIFT;
1681 inode->i_blocks = 0;
1682
1683 inode->i_op = &empty_dir_inode_operations;
1684 inode->i_opflags &= ~IOP_XATTR;
1685 inode->i_fop = &empty_dir_operations;
1686}
1687
1688bool is_empty_dir_inode(struct inode *inode)
1689{
1690 return (inode->i_fop == &empty_dir_operations) &&
1691 (inode->i_op == &empty_dir_inode_operations);
1692}
1693
1694#if IS_ENABLED(CONFIG_UNICODE)
1695/**
1696 * generic_ci_d_compare - generic d_compare implementation for casefolding filesystems
1697 * @dentry: dentry whose name we are checking against
1698 * @len: len of name of dentry
1699 * @str: str pointer to name of dentry
1700 * @name: Name to compare against
1701 *
1702 * Return: 0 if names match, 1 if mismatch, or -ERRNO
1703 */
1704static int generic_ci_d_compare(const struct dentry *dentry, unsigned int len,
1705 const char *str, const struct qstr *name)
1706{
1707 const struct dentry *parent = READ_ONCE(dentry->d_parent);
1708 const struct inode *dir = READ_ONCE(parent->d_inode);
1709 const struct super_block *sb = dentry->d_sb;
1710 const struct unicode_map *um = sb->s_encoding;
1711 struct qstr qstr = QSTR_INIT(str, len);
1712 char strbuf[DNAME_INLINE_LEN];
1713 int ret;
1714
1715 if (!dir || !IS_CASEFOLDED(dir))
1716 goto fallback;
1717 /*
1718 * If the dentry name is stored in-line, then it may be concurrently
1719 * modified by a rename. If this happens, the VFS will eventually retry
1720 * the lookup, so it doesn't matter what ->d_compare() returns.
1721 * However, it's unsafe to call utf8_strncasecmp() with an unstable
1722 * string. Therefore, we have to copy the name into a temporary buffer.
1723 */
1724 if (len <= DNAME_INLINE_LEN - 1) {
1725 memcpy(strbuf, str, len);
1726 strbuf[len] = 0;
1727 qstr.name = strbuf;
1728 /* prevent compiler from optimizing out the temporary buffer */
1729 barrier();
1730 }
1731 ret = utf8_strncasecmp(um, name, &qstr);
1732 if (ret >= 0)
1733 return ret;
1734
1735 if (sb_has_strict_encoding(sb))
1736 return -EINVAL;
1737fallback:
1738 if (len != name->len)
1739 return 1;
1740 return !!memcmp(str, name->name, len);
1741}
1742
1743/**
1744 * generic_ci_d_hash - generic d_hash implementation for casefolding filesystems
1745 * @dentry: dentry of the parent directory
1746 * @str: qstr of name whose hash we should fill in
1747 *
1748 * Return: 0 if hash was successful or unchanged, and -EINVAL on error
1749 */
1750static int generic_ci_d_hash(const struct dentry *dentry, struct qstr *str)
1751{
1752 const struct inode *dir = READ_ONCE(dentry->d_inode);
1753 struct super_block *sb = dentry->d_sb;
1754 const struct unicode_map *um = sb->s_encoding;
1755 int ret = 0;
1756
1757 if (!dir || !IS_CASEFOLDED(dir))
1758 return 0;
1759
1760 ret = utf8_casefold_hash(um, dentry, str);
1761 if (ret < 0 && sb_has_strict_encoding(sb))
1762 return -EINVAL;
1763 return 0;
1764}
1765
1766static const struct dentry_operations generic_ci_dentry_ops = {
1767 .d_hash = generic_ci_d_hash,
1768 .d_compare = generic_ci_d_compare,
1769};
1770#endif
1771
1772#ifdef CONFIG_FS_ENCRYPTION
1773static const struct dentry_operations generic_encrypted_dentry_ops = {
1774 .d_revalidate = fscrypt_d_revalidate,
1775};
1776#endif
1777
1778#if defined(CONFIG_FS_ENCRYPTION) && IS_ENABLED(CONFIG_UNICODE)
1779static const struct dentry_operations generic_encrypted_ci_dentry_ops = {
1780 .d_hash = generic_ci_d_hash,
1781 .d_compare = generic_ci_d_compare,
1782 .d_revalidate = fscrypt_d_revalidate,
1783};
1784#endif
1785
1786/**
1787 * generic_set_encrypted_ci_d_ops - helper for setting d_ops for given dentry
1788 * @dentry: dentry to set ops on
1789 *
1790 * Casefolded directories need d_hash and d_compare set, so that the dentries
1791 * contained in them are handled case-insensitively. Note that these operations
1792 * are needed on the parent directory rather than on the dentries in it, and
1793 * while the casefolding flag can be toggled on and off on an empty directory,
1794 * dentry_operations can't be changed later. As a result, if the filesystem has
1795 * casefolding support enabled at all, we have to give all dentries the
1796 * casefolding operations even if their inode doesn't have the casefolding flag
1797 * currently (and thus the casefolding ops would be no-ops for now).
1798 *
1799 * Encryption works differently in that the only dentry operation it needs is
1800 * d_revalidate, which it only needs on dentries that have the no-key name flag.
1801 * The no-key flag can't be set "later", so we don't have to worry about that.
1802 *
1803 * Finally, to maximize compatibility with overlayfs (which isn't compatible
1804 * with certain dentry operations) and to avoid taking an unnecessary
1805 * performance hit, we use custom dentry_operations for each possible
1806 * combination rather than always installing all operations.
1807 */
1808void generic_set_encrypted_ci_d_ops(struct dentry *dentry)
1809{
1810#ifdef CONFIG_FS_ENCRYPTION
1811 bool needs_encrypt_ops = dentry->d_flags & DCACHE_NOKEY_NAME;
1812#endif
1813#if IS_ENABLED(CONFIG_UNICODE)
1814 bool needs_ci_ops = dentry->d_sb->s_encoding;
1815#endif
1816#if defined(CONFIG_FS_ENCRYPTION) && IS_ENABLED(CONFIG_UNICODE)
1817 if (needs_encrypt_ops && needs_ci_ops) {
1818 d_set_d_op(dentry, &generic_encrypted_ci_dentry_ops);
1819 return;
1820 }
1821#endif
1822#ifdef CONFIG_FS_ENCRYPTION
1823 if (needs_encrypt_ops) {
1824 d_set_d_op(dentry, &generic_encrypted_dentry_ops);
1825 return;
1826 }
1827#endif
1828#if IS_ENABLED(CONFIG_UNICODE)
1829 if (needs_ci_ops) {
1830 d_set_d_op(dentry, &generic_ci_dentry_ops);
1831 return;
1832 }
1833#endif
1834}
1835EXPORT_SYMBOL(generic_set_encrypted_ci_d_ops);
1836
1837/**
1838 * inode_maybe_inc_iversion - increments i_version
1839 * @inode: inode with the i_version that should be updated
1840 * @force: increment the counter even if it's not necessary?
1841 *
1842 * Every time the inode is modified, the i_version field must be seen to have
1843 * changed by any observer.
1844 *
1845 * If "force" is set or the QUERIED flag is set, then ensure that we increment
1846 * the value, and clear the queried flag.
1847 *
1848 * In the common case where neither is set, then we can return "false" without
1849 * updating i_version.
1850 *
1851 * If this function returns false, and no other metadata has changed, then we
1852 * can avoid logging the metadata.
1853 */
1854bool inode_maybe_inc_iversion(struct inode *inode, bool force)
1855{
1856 u64 cur, new;
1857
1858 /*
1859 * The i_version field is not strictly ordered with any other inode
1860 * information, but the legacy inode_inc_iversion code used a spinlock
1861 * to serialize increments.
1862 *
1863 * Here, we add full memory barriers to ensure that any de-facto
1864 * ordering with other info is preserved.
1865 *
1866 * This barrier pairs with the barrier in inode_query_iversion()
1867 */
1868 smp_mb();
1869 cur = inode_peek_iversion_raw(inode);
1870 do {
1871 /* If flag is clear then we needn't do anything */
1872 if (!force && !(cur & I_VERSION_QUERIED))
1873 return false;
1874
1875 /* Since lowest bit is flag, add 2 to avoid it */
1876 new = (cur & ~I_VERSION_QUERIED) + I_VERSION_INCREMENT;
1877 } while (!atomic64_try_cmpxchg(&inode->i_version, &cur, new));
1878 return true;
1879}
1880EXPORT_SYMBOL(inode_maybe_inc_iversion);
1881
1882/**
1883 * inode_query_iversion - read i_version for later use
1884 * @inode: inode from which i_version should be read
1885 *
1886 * Read the inode i_version counter. This should be used by callers that wish
1887 * to store the returned i_version for later comparison. This will guarantee
1888 * that a later query of the i_version will result in a different value if
1889 * anything has changed.
1890 *
1891 * In this implementation, we fetch the current value, set the QUERIED flag and
1892 * then try to swap it into place with a cmpxchg, if it wasn't already set. If
1893 * that fails, we try again with the newly fetched value from the cmpxchg.
1894 */
1895u64 inode_query_iversion(struct inode *inode)
1896{
1897 u64 cur, new;
1898
1899 cur = inode_peek_iversion_raw(inode);
1900 do {
1901 /* If flag is already set, then no need to swap */
1902 if (cur & I_VERSION_QUERIED) {
1903 /*
1904 * This barrier (and the implicit barrier in the
1905 * cmpxchg below) pairs with the barrier in
1906 * inode_maybe_inc_iversion().
1907 */
1908 smp_mb();
1909 break;
1910 }
1911
1912 new = cur | I_VERSION_QUERIED;
1913 } while (!atomic64_try_cmpxchg(&inode->i_version, &cur, new));
1914 return cur >> I_VERSION_QUERIED_SHIFT;
1915}
1916EXPORT_SYMBOL(inode_query_iversion);
1917
1918ssize_t direct_write_fallback(struct kiocb *iocb, struct iov_iter *iter,
1919 ssize_t direct_written, ssize_t buffered_written)
1920{
1921 struct address_space *mapping = iocb->ki_filp->f_mapping;
1922 loff_t pos = iocb->ki_pos - buffered_written;
1923 loff_t end = iocb->ki_pos - 1;
1924 int err;
1925
1926 /*
1927 * If the buffered write fallback returned an error, we want to return
1928 * the number of bytes which were written by direct I/O, or the error
1929 * code if that was zero.
1930 *
1931 * Note that this differs from normal direct-io semantics, which will
1932 * return -EFOO even if some bytes were written.
1933 */
1934 if (unlikely(buffered_written < 0)) {
1935 if (direct_written)
1936 return direct_written;
1937 return buffered_written;
1938 }
1939
1940 /*
1941 * We need to ensure that the page cache pages are written to disk and
1942 * invalidated to preserve the expected O_DIRECT semantics.
1943 */
1944 err = filemap_write_and_wait_range(mapping, pos, end);
1945 if (err < 0) {
1946 /*
1947 * We don't know how much we wrote, so just return the number of
1948 * bytes which were direct-written
1949 */
1950 iocb->ki_pos -= buffered_written;
1951 if (direct_written)
1952 return direct_written;
1953 return err;
1954 }
1955 invalidate_mapping_pages(mapping, pos >> PAGE_SHIFT, end >> PAGE_SHIFT);
1956 return direct_written + buffered_written;
1957}
1958EXPORT_SYMBOL_GPL(direct_write_fallback);
1959
1960/**
1961 * simple_inode_init_ts - initialize the timestamps for a new inode
1962 * @inode: inode to be initialized
1963 *
1964 * When a new inode is created, most filesystems set the timestamps to the
1965 * current time. Add a helper to do this.
1966 */
1967struct timespec64 simple_inode_init_ts(struct inode *inode)
1968{
1969 struct timespec64 ts = inode_set_ctime_current(inode);
1970
1971 inode_set_atime_to_ts(inode, ts);
1972 inode_set_mtime_to_ts(inode, ts);
1973 return ts;
1974}
1975EXPORT_SYMBOL(simple_inode_init_ts);