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/poll.h>
17 #include <linux/sched.h>
19 #include "kernfs-internal.h"
22 * There's one sysfs_open_file for each open file and one sysfs_open_dirent
23 * for each sysfs_dirent with one or more open files.
25 * sysfs_dirent->s_attr.open points to sysfs_open_dirent. s_attr.open is
26 * protected by sysfs_open_dirent_lock.
28 * filp->private_data points to seq_file whose ->private points to
29 * sysfs_open_file. sysfs_open_files are chained at
30 * sysfs_open_dirent->files, which is protected by sysfs_open_file_mutex.
32 static DEFINE_SPINLOCK(sysfs_open_dirent_lock
);
33 static DEFINE_MUTEX(sysfs_open_file_mutex
);
35 struct sysfs_open_dirent
{
38 wait_queue_head_t poll
;
39 struct list_head files
; /* goes through sysfs_open_file.list */
42 static struct sysfs_open_file
*sysfs_of(struct file
*file
)
44 return ((struct seq_file
*)file
->private_data
)->private;
48 * Determine the kernfs_ops for the given sysfs_dirent. This function must
49 * be called while holding an active reference.
51 static const struct kernfs_ops
*kernfs_ops(struct sysfs_dirent
*sd
)
53 if (sd
->s_flags
& SYSFS_FLAG_LOCKDEP
)
54 lockdep_assert_held(sd
);
55 return sd
->s_attr
.ops
;
58 static void *kernfs_seq_start(struct seq_file
*sf
, loff_t
*ppos
)
60 struct sysfs_open_file
*of
= sf
->private;
61 const struct kernfs_ops
*ops
;
64 * @of->mutex nests outside active ref and is just to ensure that
65 * the ops aren't called concurrently for the same open file.
67 mutex_lock(&of
->mutex
);
68 if (!sysfs_get_active(of
->sd
))
69 return ERR_PTR(-ENODEV
);
71 ops
= kernfs_ops(of
->sd
);
73 return ops
->seq_start(sf
, ppos
);
76 * The same behavior and code as single_open(). Returns
77 * !NULL if pos is at the beginning; otherwise, NULL.
83 static void *kernfs_seq_next(struct seq_file
*sf
, void *v
, loff_t
*ppos
)
85 struct sysfs_open_file
*of
= sf
->private;
86 const struct kernfs_ops
*ops
= kernfs_ops(of
->sd
);
89 return ops
->seq_next(sf
, v
, ppos
);
92 * The same behavior and code as single_open(), always
93 * terminate after the initial read.
100 static void kernfs_seq_stop(struct seq_file
*sf
, void *v
)
102 struct sysfs_open_file
*of
= sf
->private;
103 const struct kernfs_ops
*ops
= kernfs_ops(of
->sd
);
106 ops
->seq_stop(sf
, v
);
108 sysfs_put_active(of
->sd
);
109 mutex_unlock(&of
->mutex
);
112 static int kernfs_seq_show(struct seq_file
*sf
, void *v
)
114 struct sysfs_open_file
*of
= sf
->private;
116 of
->event
= atomic_read(&of
->sd
->s_attr
.open
->event
);
118 return of
->sd
->s_attr
.ops
->seq_show(sf
, v
);
121 static const struct seq_operations kernfs_seq_ops
= {
122 .start
= kernfs_seq_start
,
123 .next
= kernfs_seq_next
,
124 .stop
= kernfs_seq_stop
,
125 .show
= kernfs_seq_show
,
129 * As reading a bin file can have side-effects, the exact offset and bytes
130 * specified in read(2) call should be passed to the read callback making
131 * it difficult to use seq_file. Implement simplistic custom buffering for
134 static ssize_t
kernfs_file_direct_read(struct sysfs_open_file
*of
,
135 char __user
*user_buf
, size_t count
,
138 ssize_t len
= min_t(size_t, count
, PAGE_SIZE
);
139 const struct kernfs_ops
*ops
;
142 buf
= kmalloc(len
, GFP_KERNEL
);
147 * @of->mutex nests outside active ref and is just to ensure that
148 * the ops aren't called concurrently for the same open file.
150 mutex_lock(&of
->mutex
);
151 if (!sysfs_get_active(of
->sd
)) {
153 mutex_unlock(&of
->mutex
);
157 ops
= kernfs_ops(of
->sd
);
159 len
= ops
->read(of
, buf
, len
, *ppos
);
163 sysfs_put_active(of
->sd
);
164 mutex_unlock(&of
->mutex
);
169 if (copy_to_user(user_buf
, buf
, len
)) {
182 * kernfs_file_read - kernfs vfs read callback
183 * @file: file pointer
184 * @user_buf: data to write
185 * @count: number of bytes
186 * @ppos: starting offset
188 static ssize_t
kernfs_file_read(struct file
*file
, char __user
*user_buf
,
189 size_t count
, loff_t
*ppos
)
191 struct sysfs_open_file
*of
= sysfs_of(file
);
193 if (of
->sd
->s_flags
& SYSFS_FLAG_HAS_SEQ_SHOW
)
194 return seq_read(file
, user_buf
, count
, ppos
);
196 return kernfs_file_direct_read(of
, user_buf
, count
, ppos
);
200 * kernfs_file_write - kernfs vfs write callback
201 * @file: file pointer
202 * @user_buf: data to write
203 * @count: number of bytes
204 * @ppos: starting offset
206 * Copy data in from userland and pass it to the matching kernfs write
209 * There is no easy way for us to know if userspace is only doing a partial
210 * write, so we don't support them. We expect the entire buffer to come on
211 * the first write. Hint: if you're writing a value, first read the file,
212 * modify only the the value you're changing, then write entire buffer
215 static ssize_t
kernfs_file_write(struct file
*file
, const char __user
*user_buf
,
216 size_t count
, loff_t
*ppos
)
218 struct sysfs_open_file
*of
= sysfs_of(file
);
219 ssize_t len
= min_t(size_t, count
, PAGE_SIZE
);
220 const struct kernfs_ops
*ops
;
223 buf
= kmalloc(len
+ 1, GFP_KERNEL
);
227 if (copy_from_user(buf
, user_buf
, len
)) {
231 buf
[len
] = '\0'; /* guarantee string termination */
234 * @of->mutex nests outside active ref and is just to ensure that
235 * the ops aren't called concurrently for the same open file.
237 mutex_lock(&of
->mutex
);
238 if (!sysfs_get_active(of
->sd
)) {
239 mutex_unlock(&of
->mutex
);
244 ops
= kernfs_ops(of
->sd
);
246 len
= ops
->write(of
, buf
, len
, *ppos
);
250 sysfs_put_active(of
->sd
);
251 mutex_unlock(&of
->mutex
);
260 static void kernfs_vma_open(struct vm_area_struct
*vma
)
262 struct file
*file
= vma
->vm_file
;
263 struct sysfs_open_file
*of
= sysfs_of(file
);
268 if (!sysfs_get_active(of
->sd
))
271 if (of
->vm_ops
->open
)
272 of
->vm_ops
->open(vma
);
274 sysfs_put_active(of
->sd
);
277 static int kernfs_vma_fault(struct vm_area_struct
*vma
, struct vm_fault
*vmf
)
279 struct file
*file
= vma
->vm_file
;
280 struct sysfs_open_file
*of
= sysfs_of(file
);
284 return VM_FAULT_SIGBUS
;
286 if (!sysfs_get_active(of
->sd
))
287 return VM_FAULT_SIGBUS
;
289 ret
= VM_FAULT_SIGBUS
;
290 if (of
->vm_ops
->fault
)
291 ret
= of
->vm_ops
->fault(vma
, vmf
);
293 sysfs_put_active(of
->sd
);
297 static int kernfs_vma_page_mkwrite(struct vm_area_struct
*vma
,
298 struct vm_fault
*vmf
)
300 struct file
*file
= vma
->vm_file
;
301 struct sysfs_open_file
*of
= sysfs_of(file
);
305 return VM_FAULT_SIGBUS
;
307 if (!sysfs_get_active(of
->sd
))
308 return VM_FAULT_SIGBUS
;
311 if (of
->vm_ops
->page_mkwrite
)
312 ret
= of
->vm_ops
->page_mkwrite(vma
, vmf
);
314 file_update_time(file
);
316 sysfs_put_active(of
->sd
);
320 static int kernfs_vma_access(struct vm_area_struct
*vma
, unsigned long addr
,
321 void *buf
, int len
, int write
)
323 struct file
*file
= vma
->vm_file
;
324 struct sysfs_open_file
*of
= sysfs_of(file
);
330 if (!sysfs_get_active(of
->sd
))
334 if (of
->vm_ops
->access
)
335 ret
= of
->vm_ops
->access(vma
, addr
, buf
, len
, write
);
337 sysfs_put_active(of
->sd
);
342 static int kernfs_vma_set_policy(struct vm_area_struct
*vma
,
343 struct mempolicy
*new)
345 struct file
*file
= vma
->vm_file
;
346 struct sysfs_open_file
*of
= sysfs_of(file
);
352 if (!sysfs_get_active(of
->sd
))
356 if (of
->vm_ops
->set_policy
)
357 ret
= of
->vm_ops
->set_policy(vma
, new);
359 sysfs_put_active(of
->sd
);
363 static struct mempolicy
*kernfs_vma_get_policy(struct vm_area_struct
*vma
,
366 struct file
*file
= vma
->vm_file
;
367 struct sysfs_open_file
*of
= sysfs_of(file
);
368 struct mempolicy
*pol
;
371 return vma
->vm_policy
;
373 if (!sysfs_get_active(of
->sd
))
374 return vma
->vm_policy
;
376 pol
= vma
->vm_policy
;
377 if (of
->vm_ops
->get_policy
)
378 pol
= of
->vm_ops
->get_policy(vma
, addr
);
380 sysfs_put_active(of
->sd
);
384 static int kernfs_vma_migrate(struct vm_area_struct
*vma
,
385 const nodemask_t
*from
, const nodemask_t
*to
,
388 struct file
*file
= vma
->vm_file
;
389 struct sysfs_open_file
*of
= sysfs_of(file
);
395 if (!sysfs_get_active(of
->sd
))
399 if (of
->vm_ops
->migrate
)
400 ret
= of
->vm_ops
->migrate(vma
, from
, to
, flags
);
402 sysfs_put_active(of
->sd
);
407 static const struct vm_operations_struct kernfs_vm_ops
= {
408 .open
= kernfs_vma_open
,
409 .fault
= kernfs_vma_fault
,
410 .page_mkwrite
= kernfs_vma_page_mkwrite
,
411 .access
= kernfs_vma_access
,
413 .set_policy
= kernfs_vma_set_policy
,
414 .get_policy
= kernfs_vma_get_policy
,
415 .migrate
= kernfs_vma_migrate
,
419 static int kernfs_file_mmap(struct file
*file
, struct vm_area_struct
*vma
)
421 struct sysfs_open_file
*of
= sysfs_of(file
);
422 const struct kernfs_ops
*ops
;
425 mutex_lock(&of
->mutex
);
428 if (!sysfs_get_active(of
->sd
))
431 ops
= kernfs_ops(of
->sd
);
433 rc
= ops
->mmap(of
, vma
);
438 * PowerPC's pci_mmap of legacy_mem uses shmem_zero_setup()
439 * to satisfy versions of X which crash if the mmap fails: that
440 * substitutes a new vm_file, and we don't then want bin_vm_ops.
442 if (vma
->vm_file
!= file
)
446 if (of
->mmapped
&& of
->vm_ops
!= vma
->vm_ops
)
450 * It is not possible to successfully wrap close.
451 * So error if someone is trying to use close.
454 if (vma
->vm_ops
&& vma
->vm_ops
->close
)
459 of
->vm_ops
= vma
->vm_ops
;
460 vma
->vm_ops
= &kernfs_vm_ops
;
462 sysfs_put_active(of
->sd
);
464 mutex_unlock(&of
->mutex
);
470 * sysfs_get_open_dirent - get or create sysfs_open_dirent
471 * @sd: target sysfs_dirent
472 * @of: sysfs_open_file for this instance of open
474 * If @sd->s_attr.open exists, increment its reference count;
475 * otherwise, create one. @of is chained to the files list.
478 * Kernel thread context (may sleep).
481 * 0 on success, -errno on failure.
483 static int sysfs_get_open_dirent(struct sysfs_dirent
*sd
,
484 struct sysfs_open_file
*of
)
486 struct sysfs_open_dirent
*od
, *new_od
= NULL
;
489 mutex_lock(&sysfs_open_file_mutex
);
490 spin_lock_irq(&sysfs_open_dirent_lock
);
492 if (!sd
->s_attr
.open
&& new_od
) {
493 sd
->s_attr
.open
= new_od
;
497 od
= sd
->s_attr
.open
;
499 atomic_inc(&od
->refcnt
);
500 list_add_tail(&of
->list
, &od
->files
);
503 spin_unlock_irq(&sysfs_open_dirent_lock
);
504 mutex_unlock(&sysfs_open_file_mutex
);
511 /* not there, initialize a new one and retry */
512 new_od
= kmalloc(sizeof(*new_od
), GFP_KERNEL
);
516 atomic_set(&new_od
->refcnt
, 0);
517 atomic_set(&new_od
->event
, 1);
518 init_waitqueue_head(&new_od
->poll
);
519 INIT_LIST_HEAD(&new_od
->files
);
524 * sysfs_put_open_dirent - put sysfs_open_dirent
525 * @sd: target sysfs_dirent
526 * @of: associated sysfs_open_file
528 * Put @sd->s_attr.open and unlink @of from the files list. If
529 * reference count reaches zero, disassociate and free it.
534 static void sysfs_put_open_dirent(struct sysfs_dirent
*sd
,
535 struct sysfs_open_file
*of
)
537 struct sysfs_open_dirent
*od
= sd
->s_attr
.open
;
540 mutex_lock(&sysfs_open_file_mutex
);
541 spin_lock_irqsave(&sysfs_open_dirent_lock
, flags
);
546 if (atomic_dec_and_test(&od
->refcnt
))
547 sd
->s_attr
.open
= NULL
;
551 spin_unlock_irqrestore(&sysfs_open_dirent_lock
, flags
);
552 mutex_unlock(&sysfs_open_file_mutex
);
557 static int kernfs_file_open(struct inode
*inode
, struct file
*file
)
559 struct sysfs_dirent
*attr_sd
= file
->f_path
.dentry
->d_fsdata
;
560 const struct kernfs_ops
*ops
;
561 struct sysfs_open_file
*of
;
562 bool has_read
, has_write
, has_mmap
;
565 if (!sysfs_get_active(attr_sd
))
568 ops
= kernfs_ops(attr_sd
);
570 has_read
= ops
->seq_show
|| ops
->read
|| ops
->mmap
;
571 has_write
= ops
->write
|| ops
->mmap
;
572 has_mmap
= ops
->mmap
;
574 /* check perms and supported operations */
575 if ((file
->f_mode
& FMODE_WRITE
) &&
576 (!(inode
->i_mode
& S_IWUGO
) || !has_write
))
579 if ((file
->f_mode
& FMODE_READ
) &&
580 (!(inode
->i_mode
& S_IRUGO
) || !has_read
))
583 /* allocate a sysfs_open_file for the file */
585 of
= kzalloc(sizeof(struct sysfs_open_file
), GFP_KERNEL
);
590 * The following is done to give a different lockdep key to
591 * @of->mutex for files which implement mmap. This is a rather
592 * crude way to avoid false positive lockdep warning around
593 * mm->mmap_sem - mmap nests @of->mutex under mm->mmap_sem and
594 * reading /sys/block/sda/trace/act_mask grabs sr_mutex, under
595 * which mm->mmap_sem nests, while holding @of->mutex. As each
596 * open file has a separate mutex, it's okay as long as those don't
597 * happen on the same file. At this point, we can't easily give
598 * each file a separate locking class. Let's differentiate on
599 * whether the file has mmap or not for now.
602 mutex_init(&of
->mutex
);
604 mutex_init(&of
->mutex
);
610 * Always instantiate seq_file even if read access doesn't use
611 * seq_file or is not requested. This unifies private data access
612 * and readable regular files are the vast majority anyway.
615 error
= seq_open(file
, &kernfs_seq_ops
);
617 error
= seq_open(file
, NULL
);
621 ((struct seq_file
*)file
->private_data
)->private = of
;
623 /* seq_file clears PWRITE unconditionally, restore it if WRITE */
624 if (file
->f_mode
& FMODE_WRITE
)
625 file
->f_mode
|= FMODE_PWRITE
;
627 /* make sure we have open dirent struct */
628 error
= sysfs_get_open_dirent(attr_sd
, of
);
632 /* open succeeded, put active references */
633 sysfs_put_active(attr_sd
);
637 seq_release(inode
, file
);
641 sysfs_put_active(attr_sd
);
645 static int kernfs_file_release(struct inode
*inode
, struct file
*filp
)
647 struct sysfs_dirent
*sd
= filp
->f_path
.dentry
->d_fsdata
;
648 struct sysfs_open_file
*of
= sysfs_of(filp
);
650 sysfs_put_open_dirent(sd
, of
);
651 seq_release(inode
, filp
);
657 void sysfs_unmap_bin_file(struct sysfs_dirent
*sd
)
659 struct sysfs_open_dirent
*od
;
660 struct sysfs_open_file
*of
;
662 if (!(sd
->s_flags
& SYSFS_FLAG_HAS_MMAP
))
665 spin_lock_irq(&sysfs_open_dirent_lock
);
666 od
= sd
->s_attr
.open
;
668 atomic_inc(&od
->refcnt
);
669 spin_unlock_irq(&sysfs_open_dirent_lock
);
673 mutex_lock(&sysfs_open_file_mutex
);
674 list_for_each_entry(of
, &od
->files
, list
) {
675 struct inode
*inode
= file_inode(of
->file
);
676 unmap_mapping_range(inode
->i_mapping
, 0, 0, 1);
678 mutex_unlock(&sysfs_open_file_mutex
);
680 sysfs_put_open_dirent(sd
, NULL
);
683 /* Sysfs attribute files are pollable. The idea is that you read
684 * the content and then you use 'poll' or 'select' to wait for
685 * the content to change. When the content changes (assuming the
686 * manager for the kobject supports notification), poll will
687 * return POLLERR|POLLPRI, and select will return the fd whether
688 * it is waiting for read, write, or exceptions.
689 * Once poll/select indicates that the value has changed, you
690 * need to close and re-open the file, or seek to 0 and read again.
691 * Reminder: this only works for attributes which actively support
692 * it, and it is not possible to test an attribute from userspace
693 * to see if it supports poll (Neither 'poll' nor 'select' return
694 * an appropriate error code). When in doubt, set a suitable timeout value.
696 static unsigned int kernfs_file_poll(struct file
*filp
, poll_table
*wait
)
698 struct sysfs_open_file
*of
= sysfs_of(filp
);
699 struct sysfs_dirent
*attr_sd
= filp
->f_path
.dentry
->d_fsdata
;
700 struct sysfs_open_dirent
*od
= attr_sd
->s_attr
.open
;
702 /* need parent for the kobj, grab both */
703 if (!sysfs_get_active(attr_sd
))
706 poll_wait(filp
, &od
->poll
, wait
);
708 sysfs_put_active(attr_sd
);
710 if (of
->event
!= atomic_read(&od
->event
))
713 return DEFAULT_POLLMASK
;
716 return DEFAULT_POLLMASK
|POLLERR
|POLLPRI
;
720 * kernfs_notify - notify a kernfs file
721 * @sd: file to notify
723 * Notify @sd such that poll(2) on @sd wakes up.
725 void kernfs_notify(struct sysfs_dirent
*sd
)
727 struct sysfs_open_dirent
*od
;
730 spin_lock_irqsave(&sysfs_open_dirent_lock
, flags
);
732 if (!WARN_ON(sysfs_type(sd
) != SYSFS_KOBJ_ATTR
)) {
733 od
= sd
->s_attr
.open
;
735 atomic_inc(&od
->event
);
736 wake_up_interruptible(&od
->poll
);
740 spin_unlock_irqrestore(&sysfs_open_dirent_lock
, flags
);
742 EXPORT_SYMBOL_GPL(kernfs_notify
);
744 const struct file_operations kernfs_file_operations
= {
745 .read
= kernfs_file_read
,
746 .write
= kernfs_file_write
,
747 .llseek
= generic_file_llseek
,
748 .mmap
= kernfs_file_mmap
,
749 .open
= kernfs_file_open
,
750 .release
= kernfs_file_release
,
751 .poll
= kernfs_file_poll
,
755 * kernfs_create_file_ns_key - create a file
756 * @parent: directory to create the file in
757 * @name: name of the file
758 * @mode: mode of the file
759 * @size: size of the file
760 * @ops: kernfs operations for the file
761 * @priv: private data for the file
762 * @ns: optional namespace tag of the file
763 * @key: lockdep key for the file's active_ref, %NULL to disable lockdep
765 * Returns the created node on success, ERR_PTR() value on error.
767 struct sysfs_dirent
*kernfs_create_file_ns_key(struct sysfs_dirent
*parent
,
769 umode_t mode
, loff_t size
,
770 const struct kernfs_ops
*ops
,
771 void *priv
, const void *ns
,
772 struct lock_class_key
*key
)
774 struct sysfs_addrm_cxt acxt
;
775 struct sysfs_dirent
*sd
;
778 sd
= sysfs_new_dirent(kernfs_root(parent
), name
,
779 (mode
& S_IALLUGO
) | S_IFREG
, SYSFS_KOBJ_ATTR
);
781 return ERR_PTR(-ENOMEM
);
783 sd
->s_attr
.ops
= ops
;
784 sd
->s_attr
.size
= size
;
788 #ifdef CONFIG_DEBUG_LOCK_ALLOC
790 lockdep_init_map(&sd
->dep_map
, "s_active", key
, 0);
791 sd
->s_flags
|= SYSFS_FLAG_LOCKDEP
;
796 * sd->s_attr.ops is accesible only while holding active ref. We
797 * need to know whether some ops are implemented outside active
798 * ref. Cache their existence in flags.
801 sd
->s_flags
|= SYSFS_FLAG_HAS_SEQ_SHOW
;
803 sd
->s_flags
|= SYSFS_FLAG_HAS_MMAP
;
805 sysfs_addrm_start(&acxt
);
806 rc
= sysfs_add_one(&acxt
, sd
, parent
);
807 sysfs_addrm_finish(&acxt
);