5 The text below describes the locking rules for VFS-related methods.
6 It is (believed to be) up-to-date. *Please*, if you change anything in
7 prototypes or locking protocols - update this file. And update the relevant
8 instances in the tree, don't leave that to maintainers of filesystems/devices/
9 etc. At the very least, put the list of dubious cases in the end of this file.
10 Don't turn it into log - maintainers of out-of-the-tree code are supposed to
11 be able to use diff(1).
13 Thing currently missing here: socket operations. Alexey?
20 int (*d_revalidate)(struct dentry *, unsigned int);
21 int (*d_weak_revalidate)(struct dentry *, unsigned int);
22 int (*d_hash)(const struct dentry *, struct qstr *);
23 int (*d_compare)(const struct dentry *,
24 unsigned int, const char *, const struct qstr *);
25 int (*d_delete)(struct dentry *);
26 int (*d_init)(struct dentry *);
27 void (*d_release)(struct dentry *);
28 void (*d_iput)(struct dentry *, struct inode *);
29 char *(*d_dname)((struct dentry *dentry, char *buffer, int buflen);
30 struct vfsmount *(*d_automount)(struct path *path);
31 int (*d_manage)(const struct path *, bool);
32 struct dentry *(*d_real)(struct dentry *, const struct inode *);
36 ================== =========== ======== ============== ========
37 ops rename_lock ->d_lock may block rcu-walk
38 ================== =========== ======== ============== ========
39 d_revalidate: no no yes (ref-walk) maybe
40 d_weak_revalidate: no no yes no
42 d_compare: yes no no maybe
43 d_delete: no yes no no
45 d_release: no no yes no
49 d_automount: no no yes no
50 d_manage: no no yes (ref-walk) maybe
52 ================== =========== ======== ============== ========
59 int (*create) (struct inode *,struct dentry *,umode_t, bool);
60 struct dentry * (*lookup) (struct inode *,struct dentry *, unsigned int);
61 int (*link) (struct dentry *,struct inode *,struct dentry *);
62 int (*unlink) (struct inode *,struct dentry *);
63 int (*symlink) (struct inode *,struct dentry *,const char *);
64 int (*mkdir) (struct inode *,struct dentry *,umode_t);
65 int (*rmdir) (struct inode *,struct dentry *);
66 int (*mknod) (struct inode *,struct dentry *,umode_t,dev_t);
67 int (*rename) (struct inode *, struct dentry *,
68 struct inode *, struct dentry *, unsigned int);
69 int (*readlink) (struct dentry *, char __user *,int);
70 const char *(*get_link) (struct dentry *, struct inode *, struct delayed_call *);
71 void (*truncate) (struct inode *);
72 int (*permission) (struct inode *, int, unsigned int);
73 struct posix_acl * (*get_acl)(struct inode *, int, bool);
74 int (*setattr) (struct dentry *, struct iattr *);
75 int (*getattr) (const struct path *, struct kstat *, u32, unsigned int);
76 ssize_t (*listxattr) (struct dentry *, char *, size_t);
77 int (*fiemap)(struct inode *, struct fiemap_extent_info *, u64 start, u64 len);
78 void (*update_time)(struct inode *, struct timespec *, int);
79 int (*atomic_open)(struct inode *, struct dentry *,
80 struct file *, unsigned open_flag,
82 int (*tmpfile) (struct user_namespace *, struct inode *,
83 struct file *, umode_t);
84 int (*fileattr_set)(struct user_namespace *mnt_userns,
85 struct dentry *dentry, struct fileattr *fa);
86 int (*fileattr_get)(struct dentry *dentry, struct fileattr *fa);
91 ============= =============================================
93 ============= =============================================
96 link: exclusive (both)
100 unlink: exclusive (both)
101 rmdir: exclusive (both)(see below)
102 rename: exclusive (both parents, some children) (see below)
106 permission: no (may not block if called in rcu-walk mode)
112 atomic_open: shared (exclusive if O_CREAT is set in open flags)
114 fileattr_get: no or exclusive
115 fileattr_set: exclusive
116 ============= =============================================
119 Additionally, ->rmdir(), ->unlink() and ->rename() have ->i_rwsem
121 cross-directory ->rename() has (per-superblock) ->s_vfs_rename_sem.
122 ->unlink() and ->rename() have ->i_rwsem exclusive on all non-directories
124 ->rename() has ->i_rwsem exclusive on any subdirectory that changes parent.
126 See Documentation/filesystems/directory-locking.rst for more detailed discussion
127 of the locking scheme for directory operations.
129 xattr_handler operations
130 ========================
134 bool (*list)(struct dentry *dentry);
135 int (*get)(const struct xattr_handler *handler, struct dentry *dentry,
136 struct inode *inode, const char *name, void *buffer,
138 int (*set)(const struct xattr_handler *handler,
139 struct user_namespace *mnt_userns,
140 struct dentry *dentry, struct inode *inode, const char *name,
141 const void *buffer, size_t size, int flags);
159 struct inode *(*alloc_inode)(struct super_block *sb);
160 void (*free_inode)(struct inode *);
161 void (*destroy_inode)(struct inode *);
162 void (*dirty_inode) (struct inode *, int flags);
163 int (*write_inode) (struct inode *, struct writeback_control *wbc);
164 int (*drop_inode) (struct inode *);
165 void (*evict_inode) (struct inode *);
166 void (*put_super) (struct super_block *);
167 int (*sync_fs)(struct super_block *sb, int wait);
168 int (*freeze_fs) (struct super_block *);
169 int (*unfreeze_fs) (struct super_block *);
170 int (*statfs) (struct dentry *, struct kstatfs *);
171 int (*remount_fs) (struct super_block *, int *, char *);
172 void (*umount_begin) (struct super_block *);
173 int (*show_options)(struct seq_file *, struct dentry *);
174 ssize_t (*quota_read)(struct super_block *, int, char *, size_t, loff_t);
175 ssize_t (*quota_write)(struct super_block *, int, const char *, size_t, loff_t);
178 All may block [not true, see below]
180 ====================== ============ ========================
182 ====================== ============ ========================
184 free_inode: called from RCU callback
188 drop_inode: !!!inode->i_lock!!!
194 statfs: maybe(read) (see below)
197 show_options: no (namespace_sem)
198 quota_read: no (see below)
199 quota_write: no (see below)
200 ====================== ============ ========================
202 ->statfs() has s_umount (shared) when called by ustat(2) (native or
203 compat), but that's an accident of bad API; s_umount is used to pin
204 the superblock down when we only have dev_t given us by userland to
205 identify the superblock. Everything else (statfs(), fstatfs(), etc.)
206 doesn't hold it when calling ->statfs() - superblock is pinned down
207 by resolving the pathname passed to syscall.
209 ->quota_read() and ->quota_write() functions are both guaranteed to
210 be the only ones operating on the quota file by the quota code (via
211 dqio_sem) (unless an admin really wants to screw up something and
212 writes to quota files with quotas on). For other details about locking
213 see also dquot_operations section.
220 struct dentry *(*mount) (struct file_system_type *, int,
221 const char *, void *);
222 void (*kill_sb) (struct super_block *);
233 ->mount() returns ERR_PTR or the root dentry; its superblock should be locked
236 ->kill_sb() takes a write-locked superblock, does all shutdown work on it,
237 unlocks and drops the reference.
239 address_space_operations
240 ========================
243 int (*writepage)(struct page *page, struct writeback_control *wbc);
244 int (*read_folio)(struct file *, struct folio *);
245 int (*writepages)(struct address_space *, struct writeback_control *);
246 bool (*dirty_folio)(struct address_space *, struct folio *folio);
247 void (*readahead)(struct readahead_control *);
248 int (*write_begin)(struct file *, struct address_space *mapping,
249 loff_t pos, unsigned len,
250 struct page **pagep, void **fsdata);
251 int (*write_end)(struct file *, struct address_space *mapping,
252 loff_t pos, unsigned len, unsigned copied,
253 struct page *page, void *fsdata);
254 sector_t (*bmap)(struct address_space *, sector_t);
255 void (*invalidate_folio) (struct folio *, size_t start, size_t len);
256 bool (*release_folio)(struct folio *, gfp_t);
257 void (*free_folio)(struct folio *);
258 int (*direct_IO)(struct kiocb *, struct iov_iter *iter);
259 int (*migrate_folio)(struct address_space *, struct folio *dst,
260 struct folio *src, enum migrate_mode);
261 int (*launder_folio)(struct folio *);
262 bool (*is_partially_uptodate)(struct folio *, size_t from, size_t count);
263 int (*error_remove_page)(struct address_space *, struct page *);
264 int (*swap_activate)(struct swap_info_struct *sis, struct file *f, sector_t *span)
265 int (*swap_deactivate)(struct file *);
266 int (*swap_rw)(struct kiocb *iocb, struct iov_iter *iter);
269 All except dirty_folio and free_folio may block
271 ====================== ======================== ========= ===============
272 ops folio locked i_rwsem invalidate_lock
273 ====================== ======================== ========= ===============
274 writepage: yes, unlocks (see below)
275 read_folio: yes, unlocks shared
278 readahead: yes, unlocks shared
279 write_begin: locks the page exclusive
280 write_end: yes, unlocks exclusive
282 invalidate_folio: yes exclusive
286 migrate_folio: yes (both)
288 is_partially_uptodate: yes
289 error_remove_page: yes
292 swap_rw: yes, unlocks
293 ====================== ======================== ========= ===============
295 ->write_begin(), ->write_end() and ->read_folio() may be called from
296 the request handler (/dev/loop).
298 ->read_folio() unlocks the folio, either synchronously or via I/O
301 ->readahead() unlocks the folios that I/O is attempted on like ->read_folio().
303 ->writepage() is used for two purposes: for "memory cleansing" and for
304 "sync". These are quite different operations and the behaviour may differ
305 depending upon the mode.
307 If writepage is called for sync (wbc->sync_mode != WBC_SYNC_NONE) then
308 it *must* start I/O against the page, even if that would involve
309 blocking on in-progress I/O.
311 If writepage is called for memory cleansing (sync_mode ==
312 WBC_SYNC_NONE) then its role is to get as much writeout underway as
313 possible. So writepage should try to avoid blocking against
314 currently-in-progress I/O.
316 If the filesystem is not called for "sync" and it determines that it
317 would need to block against in-progress I/O to be able to start new I/O
318 against the page the filesystem should redirty the page with
319 redirty_page_for_writepage(), then unlock the page and return zero.
320 This may also be done to avoid internal deadlocks, but rarely.
322 If the filesystem is called for sync then it must wait on any
323 in-progress I/O and then start new I/O.
325 The filesystem should unlock the page synchronously, before returning to the
326 caller, unless ->writepage() returns special WRITEPAGE_ACTIVATE
327 value. WRITEPAGE_ACTIVATE means that page cannot really be written out
328 currently, and VM should stop calling ->writepage() on this page for some
329 time. VM does this by moving page to the head of the active list, hence the
332 Unless the filesystem is going to redirty_page_for_writepage(), unlock the page
333 and return zero, writepage *must* run set_page_writeback() against the page,
334 followed by unlocking it. Once set_page_writeback() has been run against the
335 page, write I/O can be submitted and the write I/O completion handler must run
336 end_page_writeback() once the I/O is complete. If no I/O is submitted, the
337 filesystem must run end_page_writeback() against the page before returning from
340 That is: after 2.5.12, pages which are under writeout are *not* locked. Note,
341 if the filesystem needs the page to be locked during writeout, that is ok, too,
342 the page is allowed to be unlocked at any point in time between the calls to
343 set_page_writeback() and end_page_writeback().
345 Note, failure to run either redirty_page_for_writepage() or the combination of
346 set_page_writeback()/end_page_writeback() on a page submitted to writepage
347 will leave the page itself marked clean but it will be tagged as dirty in the
348 radix tree. This incoherency can lead to all sorts of hard-to-debug problems
349 in the filesystem like having dirty inodes at umount and losing written data.
351 ->writepages() is used for periodic writeback and for syscall-initiated
352 sync operations. The address_space should start I/O against at least
353 ``*nr_to_write`` pages. ``*nr_to_write`` must be decremented for each page
354 which is written. The address_space implementation may write more (or less)
355 pages than ``*nr_to_write`` asks for, but it should try to be reasonably close.
356 If nr_to_write is NULL, all dirty pages must be written.
358 writepages should _only_ write pages which are present on
361 ->dirty_folio() is called from various places in the kernel when
362 the target folio is marked as needing writeback. The folio cannot be
363 truncated because either the caller holds the folio lock, or the caller
364 has found the folio while holding the page table lock which will block
367 ->bmap() is currently used by legacy ioctl() (FIBMAP) provided by some
368 filesystems and by the swapper. The latter will eventually go away. Please,
369 keep it that way and don't breed new callers.
371 ->invalidate_folio() is called when the filesystem must attempt to drop
372 some or all of the buffers from the page when it is being truncated. It
373 returns zero on success. The filesystem must exclusively acquire
374 invalidate_lock before invalidating page cache in truncate / hole punch
375 path (and thus calling into ->invalidate_folio) to block races between page
376 cache invalidation and page cache filling functions (fault, read, ...).
378 ->release_folio() is called when the kernel is about to try to drop the
379 buffers from the folio in preparation for freeing it. It returns false to
380 indicate that the buffers are (or may be) freeable. If ->release_folio is
381 NULL, the kernel assumes that the fs has no private interest in the buffers.
383 ->free_folio() is called when the kernel has dropped the folio
386 ->launder_folio() may be called prior to releasing a folio if
387 it is still found to be dirty. It returns zero if the folio was successfully
388 cleaned, or an error value if not. Note that in order to prevent the folio
389 getting mapped back in and redirtied, it needs to be kept locked
390 across the entire operation.
392 ->swap_activate() will be called to prepare the given file for swap. It
393 should perform any validation and preparation necessary to ensure that
394 writes can be performed with minimal memory allocation. It should call
395 add_swap_extent(), or the helper iomap_swapfile_activate(), and return
396 the number of extents added. If IO should be submitted through
397 ->swap_rw(), it should set SWP_FS_OPS, otherwise IO will be submitted
398 directly to the block device ``sis->bdev``.
400 ->swap_deactivate() will be called in the sys_swapoff()
401 path after ->swap_activate() returned success.
403 ->swap_rw will be called for swap IO if SWP_FS_OPS was set by ->swap_activate().
410 void (*fl_copy_lock)(struct file_lock *, struct file_lock *);
411 void (*fl_release_private)(struct file_lock *);
416 =================== ============= =========
417 ops inode->i_lock may block
418 =================== ============= =========
420 fl_release_private: maybe maybe[1]_
421 =================== ============= =========
424 ->fl_release_private for flock or POSIX locks is currently allowed
425 to block. Leases however can still be freed while the i_lock is held and
426 so fl_release_private called on a lease should not block.
428 lock_manager_operations
429 =======================
433 void (*lm_notify)(struct file_lock *); /* unblock callback */
434 int (*lm_grant)(struct file_lock *, struct file_lock *, int);
435 void (*lm_break)(struct file_lock *); /* break_lease callback */
436 int (*lm_change)(struct file_lock **, int);
437 bool (*lm_breaker_owns_lease)(struct file_lock *);
438 bool (*lm_lock_expirable)(struct file_lock *);
439 void (*lm_expire_lock)(void);
443 ====================== ============= ================= =========
444 ops flc_lock blocked_lock_lock may block
445 ====================== ============= ================= =========
450 lm_breaker_owns_lease: yes no no
451 lm_lock_expirable yes no no
452 lm_expire_lock no no yes
453 ====================== ============= ================= =========
460 void (*b_end_io)(struct buffer_head *bh, int uptodate);
464 called from interrupts. In other words, extreme care is needed here.
465 bh is locked, but that's all warranties we have here. Currently only RAID1,
466 highmem, fs/buffer.c, and fs/ntfs/aops.c are providing these. Block devices
467 call this method upon the IO completion.
469 block_device_operations
470 =======================
473 int (*open) (struct block_device *, fmode_t);
474 int (*release) (struct gendisk *, fmode_t);
475 int (*ioctl) (struct block_device *, fmode_t, unsigned, unsigned long);
476 int (*compat_ioctl) (struct block_device *, fmode_t, unsigned, unsigned long);
477 int (*direct_access) (struct block_device *, sector_t, void **,
479 void (*unlock_native_capacity) (struct gendisk *);
480 int (*getgeo)(struct block_device *, struct hd_geometry *);
481 void (*swap_slot_free_notify) (struct block_device *, unsigned long);
485 ======================= ===================
487 ======================= ===================
493 unlock_native_capacity: no
495 swap_slot_free_notify: no (see below)
496 ======================= ===================
498 swap_slot_free_notify is called with swap_lock and sometimes the page lock
507 loff_t (*llseek) (struct file *, loff_t, int);
508 ssize_t (*read) (struct file *, char __user *, size_t, loff_t *);
509 ssize_t (*write) (struct file *, const char __user *, size_t, loff_t *);
510 ssize_t (*read_iter) (struct kiocb *, struct iov_iter *);
511 ssize_t (*write_iter) (struct kiocb *, struct iov_iter *);
512 int (*iopoll) (struct kiocb *kiocb, bool spin);
513 int (*iterate) (struct file *, struct dir_context *);
514 int (*iterate_shared) (struct file *, struct dir_context *);
515 __poll_t (*poll) (struct file *, struct poll_table_struct *);
516 long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long);
517 long (*compat_ioctl) (struct file *, unsigned int, unsigned long);
518 int (*mmap) (struct file *, struct vm_area_struct *);
519 int (*open) (struct inode *, struct file *);
520 int (*flush) (struct file *);
521 int (*release) (struct inode *, struct file *);
522 int (*fsync) (struct file *, loff_t start, loff_t end, int datasync);
523 int (*fasync) (int, struct file *, int);
524 int (*lock) (struct file *, int, struct file_lock *);
525 ssize_t (*sendpage) (struct file *, struct page *, int, size_t,
527 unsigned long (*get_unmapped_area)(struct file *, unsigned long,
528 unsigned long, unsigned long, unsigned long);
529 int (*check_flags)(int);
530 int (*flock) (struct file *, int, struct file_lock *);
531 ssize_t (*splice_write)(struct pipe_inode_info *, struct file *, loff_t *,
532 size_t, unsigned int);
533 ssize_t (*splice_read)(struct file *, loff_t *, struct pipe_inode_info *,
534 size_t, unsigned int);
535 int (*setlease)(struct file *, long, struct file_lock **, void **);
536 long (*fallocate)(struct file *, int, loff_t, loff_t);
537 void (*show_fdinfo)(struct seq_file *m, struct file *f);
538 unsigned (*mmap_capabilities)(struct file *);
539 ssize_t (*copy_file_range)(struct file *, loff_t, struct file *,
540 loff_t, size_t, unsigned int);
541 loff_t (*remap_file_range)(struct file *file_in, loff_t pos_in,
542 struct file *file_out, loff_t pos_out,
543 loff_t len, unsigned int remap_flags);
544 int (*fadvise)(struct file *, loff_t, loff_t, int);
549 ->llseek() locking has moved from llseek to the individual llseek
550 implementations. If your fs is not using generic_file_llseek, you
551 need to acquire and release the appropriate locks in your ->llseek().
552 For many filesystems, it is probably safe to acquire the inode
553 mutex or just to use i_size_read() instead.
554 Note: this does not protect the file->f_pos against concurrent modifications
555 since this is something the userspace has to take care about.
557 ->iterate() is called with i_rwsem exclusive.
559 ->iterate_shared() is called with i_rwsem at least shared.
561 ->fasync() is responsible for maintaining the FASYNC bit in filp->f_flags.
562 Most instances call fasync_helper(), which does that maintenance, so it's
563 not normally something one needs to worry about. Return values > 0 will be
564 mapped to zero in the VFS layer.
566 ->readdir() and ->ioctl() on directories must be changed. Ideally we would
567 move ->readdir() to inode_operations and use a separate method for directory
568 ->ioctl() or kill the latter completely. One of the problems is that for
569 anything that resembles union-mount we won't have a struct file for all
570 components. And there are other reasons why the current interface is a mess...
572 ->read on directories probably must go away - we should just enforce -EISDIR
573 in sys_read() and friends.
575 ->setlease operations should call generic_setlease() before or after setting
576 the lease within the individual filesystem to record the result of the
579 ->fallocate implementation must be really careful to maintain page cache
580 consistency when punching holes or performing other operations that invalidate
581 page cache contents. Usually the filesystem needs to call
582 truncate_inode_pages_range() to invalidate relevant range of the page cache.
583 However the filesystem usually also needs to update its internal (and on disk)
584 view of file offset -> disk block mapping. Until this update is finished, the
585 filesystem needs to block page faults and reads from reloading now-stale page
586 cache contents from the disk. Since VFS acquires mapping->invalidate_lock in
587 shared mode when loading pages from disk (filemap_fault(), filemap_read(),
588 readahead paths), the fallocate implementation must take the invalidate_lock to
591 ->copy_file_range and ->remap_file_range implementations need to serialize
592 against modifications of file data while the operation is running. For
593 blocking changes through write(2) and similar operations inode->i_rwsem can be
594 used. To block changes to file contents via a memory mapping during the
595 operation, the filesystem must take mapping->invalidate_lock to coordinate
603 int (*write_dquot) (struct dquot *);
604 int (*acquire_dquot) (struct dquot *);
605 int (*release_dquot) (struct dquot *);
606 int (*mark_dirty) (struct dquot *);
607 int (*write_info) (struct super_block *, int);
609 These operations are intended to be more or less wrapping functions that ensure
610 a proper locking wrt the filesystem and call the generic quota operations.
612 What filesystem should expect from the generic quota functions:
614 ============== ============ =========================
615 ops FS recursion Held locks when called
616 ============== ============ =========================
617 write_dquot: yes dqonoff_sem or dqptr_sem
618 acquire_dquot: yes dqonoff_sem or dqptr_sem
619 release_dquot: yes dqonoff_sem or dqptr_sem
621 write_info: yes dqonoff_sem
622 ============== ============ =========================
624 FS recursion means calling ->quota_read() and ->quota_write() from superblock
627 More details about quota locking can be found in fs/dquot.c.
634 void (*open)(struct vm_area_struct*);
635 void (*close)(struct vm_area_struct*);
636 vm_fault_t (*fault)(struct vm_area_struct*, struct vm_fault *);
637 vm_fault_t (*page_mkwrite)(struct vm_area_struct *, struct vm_fault *);
638 vm_fault_t (*pfn_mkwrite)(struct vm_area_struct *, struct vm_fault *);
639 int (*access)(struct vm_area_struct *, unsigned long, void*, int, int);
643 ============= ========= ===========================
644 ops mmap_lock PageLocked(page)
645 ============= ========= ===========================
648 fault: yes can return with page locked
650 page_mkwrite: yes can return with page locked
653 ============= ========= ===========================
655 ->fault() is called when a previously not present pte is about to be faulted
656 in. The filesystem must find and return the page associated with the passed in
657 "pgoff" in the vm_fault structure. If it is possible that the page may be
658 truncated and/or invalidated, then the filesystem must lock invalidate_lock,
659 then ensure the page is not already truncated (invalidate_lock will block
660 subsequent truncate), and then return with VM_FAULT_LOCKED, and the page
661 locked. The VM will unlock the page.
663 ->map_pages() is called when VM asks to map easy accessible pages.
664 Filesystem should find and map pages associated with offsets from "start_pgoff"
665 till "end_pgoff". ->map_pages() is called with page table locked and must
666 not block. If it's not possible to reach a page without blocking,
667 filesystem should skip it. Filesystem should use do_set_pte() to setup
668 page table entry. Pointer to entry associated with the page is passed in
669 "pte" field in vm_fault structure. Pointers to entries for other offsets
670 should be calculated relative to "pte".
672 ->page_mkwrite() is called when a previously read-only pte is about to become
673 writeable. The filesystem again must ensure that there are no
674 truncate/invalidate races or races with operations such as ->remap_file_range
675 or ->copy_file_range, and then return with the page locked. Usually
676 mapping->invalidate_lock is suitable for proper serialization. If the page has
677 been truncated, the filesystem should not look up a new page like the ->fault()
678 handler, but simply return with VM_FAULT_NOPAGE, which will cause the VM to
681 ->pfn_mkwrite() is the same as page_mkwrite but when the pte is
682 VM_PFNMAP or VM_MIXEDMAP with a page-less entry. Expected return is
683 VM_FAULT_NOPAGE. Or one of the VM_FAULT_ERROR types. The default behavior
684 after this call is to make the pte read-write, unless pfn_mkwrite returns
687 ->access() is called when get_user_pages() fails in
688 access_process_vm(), typically used to debug a process through
689 /proc/pid/mem or ptrace. This function is needed only for
690 VM_IO | VM_PFNMAP VMAs.
692 --------------------------------------------------------------------------------
696 (if you break something or notice that it is broken and do not fix it yourself
697 - at least put it here)