2 * fs/kernfs/file.c - kernfs file implementation
4 * Copyright (c) 2001-3 Patrick Mochel
5 * Copyright (c) 2007 SUSE Linux Products GmbH
6 * Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org>
8 * This file is released under the GPLv2.
12 #include <linux/seq_file.h>
13 #include <linux/slab.h>
14 #include <linux/poll.h>
15 #include <linux/pagemap.h>
16 #include <linux/sched.h>
18 #include "kernfs-internal.h"
21 * There's one sysfs_open_file for each open file and one sysfs_open_dirent
22 * for each sysfs_dirent with one or more open files.
24 * sysfs_dirent->s_attr.open points to sysfs_open_dirent. s_attr.open is
25 * protected by sysfs_open_dirent_lock.
27 * filp->private_data points to seq_file whose ->private points to
28 * sysfs_open_file. sysfs_open_files are chained at
29 * sysfs_open_dirent->files, which is protected by sysfs_open_file_mutex.
31 static DEFINE_SPINLOCK(sysfs_open_dirent_lock
);
32 static DEFINE_MUTEX(sysfs_open_file_mutex
);
34 struct sysfs_open_dirent
{
37 wait_queue_head_t poll
;
38 struct list_head files
; /* goes through sysfs_open_file.list */
41 static struct sysfs_open_file
*sysfs_of(struct file
*file
)
43 return ((struct seq_file
*)file
->private_data
)->private;
47 * Determine the kernfs_ops for the given sysfs_dirent. This function must
48 * be called while holding an active reference.
50 static const struct kernfs_ops
*kernfs_ops(struct sysfs_dirent
*sd
)
52 if (sd
->s_flags
& SYSFS_FLAG_LOCKDEP
)
53 lockdep_assert_held(sd
);
54 return sd
->s_attr
.ops
;
57 static void *kernfs_seq_start(struct seq_file
*sf
, loff_t
*ppos
)
59 struct sysfs_open_file
*of
= sf
->private;
60 const struct kernfs_ops
*ops
;
63 * @of->mutex nests outside active ref and is just to ensure that
64 * the ops aren't called concurrently for the same open file.
66 mutex_lock(&of
->mutex
);
67 if (!sysfs_get_active(of
->sd
))
68 return ERR_PTR(-ENODEV
);
70 ops
= kernfs_ops(of
->sd
);
72 return ops
->seq_start(sf
, ppos
);
75 * The same behavior and code as single_open(). Returns
76 * !NULL if pos is at the beginning; otherwise, NULL.
82 static void *kernfs_seq_next(struct seq_file
*sf
, void *v
, loff_t
*ppos
)
84 struct sysfs_open_file
*of
= sf
->private;
85 const struct kernfs_ops
*ops
= kernfs_ops(of
->sd
);
88 return ops
->seq_next(sf
, v
, ppos
);
91 * The same behavior and code as single_open(), always
92 * terminate after the initial read.
99 static void kernfs_seq_stop(struct seq_file
*sf
, void *v
)
101 struct sysfs_open_file
*of
= sf
->private;
102 const struct kernfs_ops
*ops
= kernfs_ops(of
->sd
);
105 ops
->seq_stop(sf
, v
);
107 sysfs_put_active(of
->sd
);
108 mutex_unlock(&of
->mutex
);
111 static int kernfs_seq_show(struct seq_file
*sf
, void *v
)
113 struct sysfs_open_file
*of
= sf
->private;
115 of
->event
= atomic_read(&of
->sd
->s_attr
.open
->event
);
117 return of
->sd
->s_attr
.ops
->seq_show(sf
, v
);
120 static const struct seq_operations kernfs_seq_ops
= {
121 .start
= kernfs_seq_start
,
122 .next
= kernfs_seq_next
,
123 .stop
= kernfs_seq_stop
,
124 .show
= kernfs_seq_show
,
128 * As reading a bin file can have side-effects, the exact offset and bytes
129 * specified in read(2) call should be passed to the read callback making
130 * it difficult to use seq_file. Implement simplistic custom buffering for
133 static ssize_t
kernfs_file_direct_read(struct sysfs_open_file
*of
,
134 char __user
*user_buf
, size_t count
,
137 ssize_t len
= min_t(size_t, count
, PAGE_SIZE
);
138 const struct kernfs_ops
*ops
;
141 buf
= kmalloc(len
, GFP_KERNEL
);
146 * @of->mutex nests outside active ref and is just to ensure that
147 * the ops aren't called concurrently for the same open file.
149 mutex_lock(&of
->mutex
);
150 if (!sysfs_get_active(of
->sd
)) {
152 mutex_unlock(&of
->mutex
);
156 ops
= kernfs_ops(of
->sd
);
158 len
= ops
->read(of
, buf
, len
, *ppos
);
162 sysfs_put_active(of
->sd
);
163 mutex_unlock(&of
->mutex
);
168 if (copy_to_user(user_buf
, buf
, len
)) {
181 * kernfs_file_read - kernfs vfs read callback
182 * @file: file pointer
183 * @user_buf: data to write
184 * @count: number of bytes
185 * @ppos: starting offset
187 static ssize_t
kernfs_file_read(struct file
*file
, char __user
*user_buf
,
188 size_t count
, loff_t
*ppos
)
190 struct sysfs_open_file
*of
= sysfs_of(file
);
192 if (of
->sd
->s_flags
& SYSFS_FLAG_HAS_SEQ_SHOW
)
193 return seq_read(file
, user_buf
, count
, ppos
);
195 return kernfs_file_direct_read(of
, user_buf
, count
, ppos
);
199 * kernfs_file_write - kernfs vfs write callback
200 * @file: file pointer
201 * @user_buf: data to write
202 * @count: number of bytes
203 * @ppos: starting offset
205 * Copy data in from userland and pass it to the matching kernfs write
208 * There is no easy way for us to know if userspace is only doing a partial
209 * write, so we don't support them. We expect the entire buffer to come on
210 * the first write. Hint: if you're writing a value, first read the file,
211 * modify only the the value you're changing, then write entire buffer
214 static ssize_t
kernfs_file_write(struct file
*file
, const char __user
*user_buf
,
215 size_t count
, loff_t
*ppos
)
217 struct sysfs_open_file
*of
= sysfs_of(file
);
218 ssize_t len
= min_t(size_t, count
, PAGE_SIZE
);
219 const struct kernfs_ops
*ops
;
222 buf
= kmalloc(len
+ 1, GFP_KERNEL
);
226 if (copy_from_user(buf
, user_buf
, len
)) {
230 buf
[len
] = '\0'; /* guarantee string termination */
233 * @of->mutex nests outside active ref and is just to ensure that
234 * the ops aren't called concurrently for the same open file.
236 mutex_lock(&of
->mutex
);
237 if (!sysfs_get_active(of
->sd
)) {
238 mutex_unlock(&of
->mutex
);
243 ops
= kernfs_ops(of
->sd
);
245 len
= ops
->write(of
, buf
, len
, *ppos
);
249 sysfs_put_active(of
->sd
);
250 mutex_unlock(&of
->mutex
);
259 static void kernfs_vma_open(struct vm_area_struct
*vma
)
261 struct file
*file
= vma
->vm_file
;
262 struct sysfs_open_file
*of
= sysfs_of(file
);
267 if (!sysfs_get_active(of
->sd
))
270 if (of
->vm_ops
->open
)
271 of
->vm_ops
->open(vma
);
273 sysfs_put_active(of
->sd
);
276 static int kernfs_vma_fault(struct vm_area_struct
*vma
, struct vm_fault
*vmf
)
278 struct file
*file
= vma
->vm_file
;
279 struct sysfs_open_file
*of
= sysfs_of(file
);
283 return VM_FAULT_SIGBUS
;
285 if (!sysfs_get_active(of
->sd
))
286 return VM_FAULT_SIGBUS
;
288 ret
= VM_FAULT_SIGBUS
;
289 if (of
->vm_ops
->fault
)
290 ret
= of
->vm_ops
->fault(vma
, vmf
);
292 sysfs_put_active(of
->sd
);
296 static int kernfs_vma_page_mkwrite(struct vm_area_struct
*vma
,
297 struct vm_fault
*vmf
)
299 struct file
*file
= vma
->vm_file
;
300 struct sysfs_open_file
*of
= sysfs_of(file
);
304 return VM_FAULT_SIGBUS
;
306 if (!sysfs_get_active(of
->sd
))
307 return VM_FAULT_SIGBUS
;
310 if (of
->vm_ops
->page_mkwrite
)
311 ret
= of
->vm_ops
->page_mkwrite(vma
, vmf
);
313 file_update_time(file
);
315 sysfs_put_active(of
->sd
);
319 static int kernfs_vma_access(struct vm_area_struct
*vma
, unsigned long addr
,
320 void *buf
, int len
, int write
)
322 struct file
*file
= vma
->vm_file
;
323 struct sysfs_open_file
*of
= sysfs_of(file
);
329 if (!sysfs_get_active(of
->sd
))
333 if (of
->vm_ops
->access
)
334 ret
= of
->vm_ops
->access(vma
, addr
, buf
, len
, write
);
336 sysfs_put_active(of
->sd
);
341 static int kernfs_vma_set_policy(struct vm_area_struct
*vma
,
342 struct mempolicy
*new)
344 struct file
*file
= vma
->vm_file
;
345 struct sysfs_open_file
*of
= sysfs_of(file
);
351 if (!sysfs_get_active(of
->sd
))
355 if (of
->vm_ops
->set_policy
)
356 ret
= of
->vm_ops
->set_policy(vma
, new);
358 sysfs_put_active(of
->sd
);
362 static struct mempolicy
*kernfs_vma_get_policy(struct vm_area_struct
*vma
,
365 struct file
*file
= vma
->vm_file
;
366 struct sysfs_open_file
*of
= sysfs_of(file
);
367 struct mempolicy
*pol
;
370 return vma
->vm_policy
;
372 if (!sysfs_get_active(of
->sd
))
373 return vma
->vm_policy
;
375 pol
= vma
->vm_policy
;
376 if (of
->vm_ops
->get_policy
)
377 pol
= of
->vm_ops
->get_policy(vma
, addr
);
379 sysfs_put_active(of
->sd
);
383 static int kernfs_vma_migrate(struct vm_area_struct
*vma
,
384 const nodemask_t
*from
, const nodemask_t
*to
,
387 struct file
*file
= vma
->vm_file
;
388 struct sysfs_open_file
*of
= sysfs_of(file
);
394 if (!sysfs_get_active(of
->sd
))
398 if (of
->vm_ops
->migrate
)
399 ret
= of
->vm_ops
->migrate(vma
, from
, to
, flags
);
401 sysfs_put_active(of
->sd
);
406 static const struct vm_operations_struct kernfs_vm_ops
= {
407 .open
= kernfs_vma_open
,
408 .fault
= kernfs_vma_fault
,
409 .page_mkwrite
= kernfs_vma_page_mkwrite
,
410 .access
= kernfs_vma_access
,
412 .set_policy
= kernfs_vma_set_policy
,
413 .get_policy
= kernfs_vma_get_policy
,
414 .migrate
= kernfs_vma_migrate
,
418 static int kernfs_file_mmap(struct file
*file
, struct vm_area_struct
*vma
)
420 struct sysfs_open_file
*of
= sysfs_of(file
);
421 const struct kernfs_ops
*ops
;
424 mutex_lock(&of
->mutex
);
427 if (!sysfs_get_active(of
->sd
))
430 ops
= kernfs_ops(of
->sd
);
432 rc
= ops
->mmap(of
, vma
);
437 * PowerPC's pci_mmap of legacy_mem uses shmem_zero_setup()
438 * to satisfy versions of X which crash if the mmap fails: that
439 * substitutes a new vm_file, and we don't then want bin_vm_ops.
441 if (vma
->vm_file
!= file
)
445 if (of
->mmapped
&& of
->vm_ops
!= vma
->vm_ops
)
449 * It is not possible to successfully wrap close.
450 * So error if someone is trying to use close.
453 if (vma
->vm_ops
&& vma
->vm_ops
->close
)
458 of
->vm_ops
= vma
->vm_ops
;
459 vma
->vm_ops
= &kernfs_vm_ops
;
461 sysfs_put_active(of
->sd
);
463 mutex_unlock(&of
->mutex
);
469 * sysfs_get_open_dirent - get or create sysfs_open_dirent
470 * @sd: target sysfs_dirent
471 * @of: sysfs_open_file for this instance of open
473 * If @sd->s_attr.open exists, increment its reference count;
474 * otherwise, create one. @of is chained to the files list.
477 * Kernel thread context (may sleep).
480 * 0 on success, -errno on failure.
482 static int sysfs_get_open_dirent(struct sysfs_dirent
*sd
,
483 struct sysfs_open_file
*of
)
485 struct sysfs_open_dirent
*od
, *new_od
= NULL
;
488 mutex_lock(&sysfs_open_file_mutex
);
489 spin_lock_irq(&sysfs_open_dirent_lock
);
491 if (!sd
->s_attr
.open
&& new_od
) {
492 sd
->s_attr
.open
= new_od
;
496 od
= sd
->s_attr
.open
;
498 atomic_inc(&od
->refcnt
);
499 list_add_tail(&of
->list
, &od
->files
);
502 spin_unlock_irq(&sysfs_open_dirent_lock
);
503 mutex_unlock(&sysfs_open_file_mutex
);
510 /* not there, initialize a new one and retry */
511 new_od
= kmalloc(sizeof(*new_od
), GFP_KERNEL
);
515 atomic_set(&new_od
->refcnt
, 0);
516 atomic_set(&new_od
->event
, 1);
517 init_waitqueue_head(&new_od
->poll
);
518 INIT_LIST_HEAD(&new_od
->files
);
523 * sysfs_put_open_dirent - put sysfs_open_dirent
524 * @sd: target sysfs_dirent
525 * @of: associated sysfs_open_file
527 * Put @sd->s_attr.open and unlink @of from the files list. If
528 * reference count reaches zero, disassociate and free it.
533 static void sysfs_put_open_dirent(struct sysfs_dirent
*sd
,
534 struct sysfs_open_file
*of
)
536 struct sysfs_open_dirent
*od
= sd
->s_attr
.open
;
539 mutex_lock(&sysfs_open_file_mutex
);
540 spin_lock_irqsave(&sysfs_open_dirent_lock
, flags
);
545 if (atomic_dec_and_test(&od
->refcnt
))
546 sd
->s_attr
.open
= NULL
;
550 spin_unlock_irqrestore(&sysfs_open_dirent_lock
, flags
);
551 mutex_unlock(&sysfs_open_file_mutex
);
556 static int kernfs_file_open(struct inode
*inode
, struct file
*file
)
558 struct sysfs_dirent
*attr_sd
= file
->f_path
.dentry
->d_fsdata
;
559 const struct kernfs_ops
*ops
;
560 struct sysfs_open_file
*of
;
561 bool has_read
, has_write
, has_mmap
;
564 if (!sysfs_get_active(attr_sd
))
567 ops
= kernfs_ops(attr_sd
);
569 has_read
= ops
->seq_show
|| ops
->read
|| ops
->mmap
;
570 has_write
= ops
->write
|| ops
->mmap
;
571 has_mmap
= ops
->mmap
;
573 /* check perms and supported operations */
574 if ((file
->f_mode
& FMODE_WRITE
) &&
575 (!(inode
->i_mode
& S_IWUGO
) || !has_write
))
578 if ((file
->f_mode
& FMODE_READ
) &&
579 (!(inode
->i_mode
& S_IRUGO
) || !has_read
))
582 /* allocate a sysfs_open_file for the file */
584 of
= kzalloc(sizeof(struct sysfs_open_file
), GFP_KERNEL
);
589 * The following is done to give a different lockdep key to
590 * @of->mutex for files which implement mmap. This is a rather
591 * crude way to avoid false positive lockdep warning around
592 * mm->mmap_sem - mmap nests @of->mutex under mm->mmap_sem and
593 * reading /sys/block/sda/trace/act_mask grabs sr_mutex, under
594 * which mm->mmap_sem nests, while holding @of->mutex. As each
595 * open file has a separate mutex, it's okay as long as those don't
596 * happen on the same file. At this point, we can't easily give
597 * each file a separate locking class. Let's differentiate on
598 * whether the file has mmap or not for now.
601 mutex_init(&of
->mutex
);
603 mutex_init(&of
->mutex
);
609 * Always instantiate seq_file even if read access doesn't use
610 * seq_file or is not requested. This unifies private data access
611 * and readable regular files are the vast majority anyway.
614 error
= seq_open(file
, &kernfs_seq_ops
);
616 error
= seq_open(file
, NULL
);
620 ((struct seq_file
*)file
->private_data
)->private = of
;
622 /* seq_file clears PWRITE unconditionally, restore it if WRITE */
623 if (file
->f_mode
& FMODE_WRITE
)
624 file
->f_mode
|= FMODE_PWRITE
;
626 /* make sure we have open dirent struct */
627 error
= sysfs_get_open_dirent(attr_sd
, of
);
631 /* open succeeded, put active references */
632 sysfs_put_active(attr_sd
);
636 seq_release(inode
, file
);
640 sysfs_put_active(attr_sd
);
644 static int kernfs_file_release(struct inode
*inode
, struct file
*filp
)
646 struct sysfs_dirent
*sd
= filp
->f_path
.dentry
->d_fsdata
;
647 struct sysfs_open_file
*of
= sysfs_of(filp
);
649 sysfs_put_open_dirent(sd
, of
);
650 seq_release(inode
, filp
);
656 void sysfs_unmap_bin_file(struct sysfs_dirent
*sd
)
658 struct sysfs_open_dirent
*od
;
659 struct sysfs_open_file
*of
;
661 if (!(sd
->s_flags
& SYSFS_FLAG_HAS_MMAP
))
664 spin_lock_irq(&sysfs_open_dirent_lock
);
665 od
= sd
->s_attr
.open
;
667 atomic_inc(&od
->refcnt
);
668 spin_unlock_irq(&sysfs_open_dirent_lock
);
672 mutex_lock(&sysfs_open_file_mutex
);
673 list_for_each_entry(of
, &od
->files
, list
) {
674 struct inode
*inode
= file_inode(of
->file
);
675 unmap_mapping_range(inode
->i_mapping
, 0, 0, 1);
677 mutex_unlock(&sysfs_open_file_mutex
);
679 sysfs_put_open_dirent(sd
, NULL
);
682 /* Sysfs attribute files are pollable. The idea is that you read
683 * the content and then you use 'poll' or 'select' to wait for
684 * the content to change. When the content changes (assuming the
685 * manager for the kobject supports notification), poll will
686 * return POLLERR|POLLPRI, and select will return the fd whether
687 * it is waiting for read, write, or exceptions.
688 * Once poll/select indicates that the value has changed, you
689 * need to close and re-open the file, or seek to 0 and read again.
690 * Reminder: this only works for attributes which actively support
691 * it, and it is not possible to test an attribute from userspace
692 * to see if it supports poll (Neither 'poll' nor 'select' return
693 * an appropriate error code). When in doubt, set a suitable timeout value.
695 static unsigned int kernfs_file_poll(struct file
*filp
, poll_table
*wait
)
697 struct sysfs_open_file
*of
= sysfs_of(filp
);
698 struct sysfs_dirent
*attr_sd
= filp
->f_path
.dentry
->d_fsdata
;
699 struct sysfs_open_dirent
*od
= attr_sd
->s_attr
.open
;
701 /* need parent for the kobj, grab both */
702 if (!sysfs_get_active(attr_sd
))
705 poll_wait(filp
, &od
->poll
, wait
);
707 sysfs_put_active(attr_sd
);
709 if (of
->event
!= atomic_read(&od
->event
))
712 return DEFAULT_POLLMASK
;
715 return DEFAULT_POLLMASK
|POLLERR
|POLLPRI
;
719 * kernfs_notify - notify a kernfs file
720 * @sd: file to notify
722 * Notify @sd such that poll(2) on @sd wakes up.
724 void kernfs_notify(struct sysfs_dirent
*sd
)
726 struct sysfs_open_dirent
*od
;
729 spin_lock_irqsave(&sysfs_open_dirent_lock
, flags
);
731 if (!WARN_ON(sysfs_type(sd
) != SYSFS_KOBJ_ATTR
)) {
732 od
= sd
->s_attr
.open
;
734 atomic_inc(&od
->event
);
735 wake_up_interruptible(&od
->poll
);
739 spin_unlock_irqrestore(&sysfs_open_dirent_lock
, flags
);
741 EXPORT_SYMBOL_GPL(kernfs_notify
);
743 const struct file_operations kernfs_file_operations
= {
744 .read
= kernfs_file_read
,
745 .write
= kernfs_file_write
,
746 .llseek
= generic_file_llseek
,
747 .mmap
= kernfs_file_mmap
,
748 .open
= kernfs_file_open
,
749 .release
= kernfs_file_release
,
750 .poll
= kernfs_file_poll
,
754 * kernfs_create_file_ns_key - create a file
755 * @parent: directory to create the file in
756 * @name: name of the file
757 * @mode: mode of the file
758 * @size: size of the file
759 * @ops: kernfs operations for the file
760 * @priv: private data for the file
761 * @ns: optional namespace tag of the file
762 * @key: lockdep key for the file's active_ref, %NULL to disable lockdep
764 * Returns the created node on success, ERR_PTR() value on error.
766 struct sysfs_dirent
*kernfs_create_file_ns_key(struct sysfs_dirent
*parent
,
768 umode_t mode
, loff_t size
,
769 const struct kernfs_ops
*ops
,
770 void *priv
, const void *ns
,
771 struct lock_class_key
*key
)
773 struct sysfs_addrm_cxt acxt
;
774 struct sysfs_dirent
*sd
;
777 sd
= sysfs_new_dirent(kernfs_root(parent
), name
,
778 (mode
& S_IALLUGO
) | S_IFREG
, SYSFS_KOBJ_ATTR
);
780 return ERR_PTR(-ENOMEM
);
782 sd
->s_attr
.ops
= ops
;
783 sd
->s_attr
.size
= size
;
787 #ifdef CONFIG_DEBUG_LOCK_ALLOC
789 lockdep_init_map(&sd
->dep_map
, "s_active", key
, 0);
790 sd
->s_flags
|= SYSFS_FLAG_LOCKDEP
;
795 * sd->s_attr.ops is accesible only while holding active ref. We
796 * need to know whether some ops are implemented outside active
797 * ref. Cache their existence in flags.
800 sd
->s_flags
|= SYSFS_FLAG_HAS_SEQ_SHOW
;
802 sd
->s_flags
|= SYSFS_FLAG_HAS_MMAP
;
804 sysfs_addrm_start(&acxt
);
805 rc
= sysfs_add_one(&acxt
, sd
, parent
);
806 sysfs_addrm_finish(&acxt
);