1/*
  2 * fs/kernfs/file.c - kernfs file implementation
  3 *
  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>
  7 *
  8 * This file is released under the GPLv2.
  9 */
 10
 11#include <linux/fs.h>
 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>
 17#include <linux/fsnotify.h>
 18
 19#include "kernfs-internal.h"
 20
 21/*
 22 * There's one kernfs_open_file for each open file and one kernfs_open_node
 23 * for each kernfs_node with one or more open files.
 24 *
 25 * kernfs_node->attr.open points to kernfs_open_node.  attr.open is
 26 * protected by kernfs_open_node_lock.
 27 *
 28 * filp->private_data points to seq_file whose ->private points to
 29 * kernfs_open_file.  kernfs_open_files are chained at
 30 * kernfs_open_node->files, which is protected by kernfs_open_file_mutex.
 31 */
 32static DEFINE_SPINLOCK(kernfs_open_node_lock);
 33static DEFINE_MUTEX(kernfs_open_file_mutex);
 34
 35struct kernfs_open_node {
 36	atomic_t		refcnt;
 37	atomic_t		event;
 38	wait_queue_head_t	poll;
 39	struct list_head	files; /* goes through kernfs_open_file.list */
 40};
 41
 42/*
 43 * kernfs_notify() may be called from any context and bounces notifications
 44 * through a work item.  To minimize space overhead in kernfs_node, the
 45 * pending queue is implemented as a singly linked list of kernfs_nodes.
 46 * The list is terminated with the self pointer so that whether a
 47 * kernfs_node is on the list or not can be determined by testing the next
 48 * pointer for NULL.
 49 */
 50#define KERNFS_NOTIFY_EOL			((void *)&kernfs_notify_list)
 51
 52static DEFINE_SPINLOCK(kernfs_notify_lock);
 53static struct kernfs_node *kernfs_notify_list = KERNFS_NOTIFY_EOL;
 54
 55static struct kernfs_open_file *kernfs_of(struct file *file)
 56{
 57	return ((struct seq_file *)file->private_data)->private;
 58}
 59
 60/*
 61 * Determine the kernfs_ops for the given kernfs_node.  This function must
 62 * be called while holding an active reference.
 63 */
 64static const struct kernfs_ops *kernfs_ops(struct kernfs_node *kn)
 65{
 66	if (kn->flags & KERNFS_LOCKDEP)
 67		lockdep_assert_held(kn);
 68	return kn->attr.ops;
 69}
 70
 71/*
 72 * As kernfs_seq_stop() is also called after kernfs_seq_start() or
 73 * kernfs_seq_next() failure, it needs to distinguish whether it's stopping
 74 * a seq_file iteration which is fully initialized with an active reference
 75 * or an aborted kernfs_seq_start() due to get_active failure.  The
 76 * position pointer is the only context for each seq_file iteration and
 77 * thus the stop condition should be encoded in it.  As the return value is
 78 * directly visible to userland, ERR_PTR(-ENODEV) is the only acceptable
 79 * choice to indicate get_active failure.
 80 *
 81 * Unfortunately, this is complicated due to the optional custom seq_file
 82 * operations which may return ERR_PTR(-ENODEV) too.  kernfs_seq_stop()
 83 * can't distinguish whether ERR_PTR(-ENODEV) is from get_active failure or
 84 * custom seq_file operations and thus can't decide whether put_active
 85 * should be performed or not only on ERR_PTR(-ENODEV).
 86 *
 87 * This is worked around by factoring out the custom seq_stop() and
 88 * put_active part into kernfs_seq_stop_active(), skipping it from
 89 * kernfs_seq_stop() if ERR_PTR(-ENODEV) while invoking it directly after
 90 * custom seq_file operations fail with ERR_PTR(-ENODEV) - this ensures
 91 * that kernfs_seq_stop_active() is skipped only after get_active failure.
 92 */
 93static void kernfs_seq_stop_active(struct seq_file *sf, void *v)
 94{
 95	struct kernfs_open_file *of = sf->private;
 96	const struct kernfs_ops *ops = kernfs_ops(of->kn);
 97
 98	if (ops->seq_stop)
 99		ops->seq_stop(sf, v);
100	kernfs_put_active(of->kn);
101}
102
103static void *kernfs_seq_start(struct seq_file *sf, loff_t *ppos)
104{
105	struct kernfs_open_file *of = sf->private;
106	const struct kernfs_ops *ops;
107
108	/*
109	 * @of->mutex nests outside active ref and is primarily to ensure that
110	 * the ops aren't called concurrently for the same open file.
111	 */
112	mutex_lock(&of->mutex);
113	if (!kernfs_get_active(of->kn))
114		return ERR_PTR(-ENODEV);
115
116	ops = kernfs_ops(of->kn);
117	if (ops->seq_start) {
118		void *next = ops->seq_start(sf, ppos);
119		/* see the comment above kernfs_seq_stop_active() */
120		if (next == ERR_PTR(-ENODEV))
121			kernfs_seq_stop_active(sf, next);
122		return next;
123	} else {
124		/*
125		 * The same behavior and code as single_open().  Returns
126		 * !NULL if pos is at the beginning; otherwise, NULL.
127		 */
128		return NULL + !*ppos;
129	}
130}
131
132static void *kernfs_seq_next(struct seq_file *sf, void *v, loff_t *ppos)
133{
134	struct kernfs_open_file *of = sf->private;
135	const struct kernfs_ops *ops = kernfs_ops(of->kn);
136
137	if (ops->seq_next) {
138		void *next = ops->seq_next(sf, v, ppos);
139		/* see the comment above kernfs_seq_stop_active() */
140		if (next == ERR_PTR(-ENODEV))
141			kernfs_seq_stop_active(sf, next);
142		return next;
143	} else {
144		/*
145		 * The same behavior and code as single_open(), always
146		 * terminate after the initial read.
147		 */
148		++*ppos;
149		return NULL;
150	}
151}
152
153static void kernfs_seq_stop(struct seq_file *sf, void *v)
154{
155	struct kernfs_open_file *of = sf->private;
156
157	if (v != ERR_PTR(-ENODEV))
158		kernfs_seq_stop_active(sf, v);
159	mutex_unlock(&of->mutex);
160}
161
162static int kernfs_seq_show(struct seq_file *sf, void *v)
163{
164	struct kernfs_open_file *of = sf->private;
165
166	of->event = atomic_read(&of->kn->attr.open->event);
167
168	return of->kn->attr.ops->seq_show(sf, v);
169}
170
171static const struct seq_operations kernfs_seq_ops = {
172	.start = kernfs_seq_start,
173	.next = kernfs_seq_next,
174	.stop = kernfs_seq_stop,
175	.show = kernfs_seq_show,
176};
177
178/*
179 * As reading a bin file can have side-effects, the exact offset and bytes
180 * specified in read(2) call should be passed to the read callback making
181 * it difficult to use seq_file.  Implement simplistic custom buffering for
182 * bin files.
183 */
184static ssize_t kernfs_file_direct_read(struct kernfs_open_file *of,
185				       char __user *user_buf, size_t count,
186				       loff_t *ppos)
187{
188	ssize_t len = min_t(size_t, count, PAGE_SIZE);
189	const struct kernfs_ops *ops;
190	char *buf;
191
192	buf = of->prealloc_buf;
193	if (buf)
194		mutex_lock(&of->prealloc_mutex);
195	else
196		buf = kmalloc(len, GFP_KERNEL);
197	if (!buf)
198		return -ENOMEM;
199
200	/*
201	 * @of->mutex nests outside active ref and is used both to ensure that
202	 * the ops aren't called concurrently for the same open file.
203	 */
204	mutex_lock(&of->mutex);
205	if (!kernfs_get_active(of->kn)) {
206		len = -ENODEV;
207		mutex_unlock(&of->mutex);
208		goto out_free;
209	}
210
211	of->event = atomic_read(&of->kn->attr.open->event);
212	ops = kernfs_ops(of->kn);
213	if (ops->read)
214		len = ops->read(of, buf, len, *ppos);
215	else
216		len = -EINVAL;
217
218	kernfs_put_active(of->kn);
219	mutex_unlock(&of->mutex);
220
221	if (len < 0)
222		goto out_free;
223
224	if (copy_to_user(user_buf, buf, len)) {
225		len = -EFAULT;
226		goto out_free;
227	}
228
229	*ppos += len;
230
231 out_free:
232	if (buf == of->prealloc_buf)
233		mutex_unlock(&of->prealloc_mutex);
234	else
235		kfree(buf);
236	return len;
237}
238
239/**
240 * kernfs_fop_read - kernfs vfs read callback
241 * @file: file pointer
242 * @user_buf: data to write
243 * @count: number of bytes
244 * @ppos: starting offset
245 */
246static ssize_t kernfs_fop_read(struct file *file, char __user *user_buf,
247			       size_t count, loff_t *ppos)
248{
249	struct kernfs_open_file *of = kernfs_of(file);
250
251	if (of->kn->flags & KERNFS_HAS_SEQ_SHOW)
252		return seq_read(file, user_buf, count, ppos);
253	else
254		return kernfs_file_direct_read(of, user_buf, count, ppos);
255}
256
257/**
258 * kernfs_fop_write - kernfs vfs write callback
259 * @file: file pointer
260 * @user_buf: data to write
261 * @count: number of bytes
262 * @ppos: starting offset
263 *
264 * Copy data in from userland and pass it to the matching kernfs write
265 * operation.
266 *
267 * There is no easy way for us to know if userspace is only doing a partial
268 * write, so we don't support them. We expect the entire buffer to come on
269 * the first write.  Hint: if you're writing a value, first read the file,
270 * modify only the the value you're changing, then write entire buffer
271 * back.
272 */
273static ssize_t kernfs_fop_write(struct file *file, const char __user *user_buf,
274				size_t count, loff_t *ppos)
275{
276	struct kernfs_open_file *of = kernfs_of(file);
277	const struct kernfs_ops *ops;
278	size_t len;
279	char *buf;
280
281	if (of->atomic_write_len) {
282		len = count;
283		if (len > of->atomic_write_len)
284			return -E2BIG;
285	} else {
286		len = min_t(size_t, count, PAGE_SIZE);
287	}
288
289	buf = of->prealloc_buf;
290	if (buf)
291		mutex_lock(&of->prealloc_mutex);
292	else
293		buf = kmalloc(len + 1, GFP_KERNEL);
294	if (!buf)
295		return -ENOMEM;
296
297	if (copy_from_user(buf, user_buf, len)) {
298		len = -EFAULT;
299		goto out_free;
300	}
301	buf[len] = '\0';	/* guarantee string termination */
302
303	/*
304	 * @of->mutex nests outside active ref and is used both to ensure that
305	 * the ops aren't called concurrently for the same open file.
306	 */
307	mutex_lock(&of->mutex);
308	if (!kernfs_get_active(of->kn)) {
309		mutex_unlock(&of->mutex);
310		len = -ENODEV;
311		goto out_free;
312	}
313
314	ops = kernfs_ops(of->kn);
315	if (ops->write)
316		len = ops->write(of, buf, len, *ppos);
317	else
318		len = -EINVAL;
319
320	kernfs_put_active(of->kn);
321	mutex_unlock(&of->mutex);
322
323	if (len > 0)
324		*ppos += len;
325
326out_free:
327	if (buf == of->prealloc_buf)
328		mutex_unlock(&of->prealloc_mutex);
329	else
330		kfree(buf);
331	return len;
332}
333
334static void kernfs_vma_open(struct vm_area_struct *vma)
335{
336	struct file *file = vma->vm_file;
337	struct kernfs_open_file *of = kernfs_of(file);
338
339	if (!of->vm_ops)
340		return;
341
342	if (!kernfs_get_active(of->kn))
343		return;
344
345	if (of->vm_ops->open)
346		of->vm_ops->open(vma);
347
348	kernfs_put_active(of->kn);
349}
350
351static int kernfs_vma_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
352{
353	struct file *file = vma->vm_file;
354	struct kernfs_open_file *of = kernfs_of(file);
355	int ret;
356
357	if (!of->vm_ops)
358		return VM_FAULT_SIGBUS;
359
360	if (!kernfs_get_active(of->kn))
361		return VM_FAULT_SIGBUS;
362
363	ret = VM_FAULT_SIGBUS;
364	if (of->vm_ops->fault)
365		ret = of->vm_ops->fault(vma, vmf);
366
367	kernfs_put_active(of->kn);
368	return ret;
369}
370
371static int kernfs_vma_page_mkwrite(struct vm_area_struct *vma,
372				   struct vm_fault *vmf)
373{
374	struct file *file = vma->vm_file;
375	struct kernfs_open_file *of = kernfs_of(file);
376	int ret;
377
378	if (!of->vm_ops)
379		return VM_FAULT_SIGBUS;
380
381	if (!kernfs_get_active(of->kn))
382		return VM_FAULT_SIGBUS;
383
384	ret = 0;
385	if (of->vm_ops->page_mkwrite)
386		ret = of->vm_ops->page_mkwrite(vma, vmf);
387	else
388		file_update_time(file);
389
390	kernfs_put_active(of->kn);
391	return ret;
392}
393
394static int kernfs_vma_access(struct vm_area_struct *vma, unsigned long addr,
395			     void *buf, int len, int write)
396{
397	struct file *file = vma->vm_file;
398	struct kernfs_open_file *of = kernfs_of(file);
399	int ret;
400
401	if (!of->vm_ops)
402		return -EINVAL;
403
404	if (!kernfs_get_active(of->kn))
405		return -EINVAL;
406
407	ret = -EINVAL;
408	if (of->vm_ops->access)
409		ret = of->vm_ops->access(vma, addr, buf, len, write);
410
411	kernfs_put_active(of->kn);
412	return ret;
413}
414
415#ifdef CONFIG_NUMA
416static int kernfs_vma_set_policy(struct vm_area_struct *vma,
417				 struct mempolicy *new)
418{
419	struct file *file = vma->vm_file;
420	struct kernfs_open_file *of = kernfs_of(file);
421	int ret;
422
423	if (!of->vm_ops)
424		return 0;
425
426	if (!kernfs_get_active(of->kn))
427		return -EINVAL;
428
429	ret = 0;
430	if (of->vm_ops->set_policy)
431		ret = of->vm_ops->set_policy(vma, new);
432
433	kernfs_put_active(of->kn);
434	return ret;
435}
436
437static struct mempolicy *kernfs_vma_get_policy(struct vm_area_struct *vma,
438					       unsigned long addr)
439{
440	struct file *file = vma->vm_file;
441	struct kernfs_open_file *of = kernfs_of(file);
442	struct mempolicy *pol;
443
444	if (!of->vm_ops)
445		return vma->vm_policy;
446
447	if (!kernfs_get_active(of->kn))
448		return vma->vm_policy;
449
450	pol = vma->vm_policy;
451	if (of->vm_ops->get_policy)
452		pol = of->vm_ops->get_policy(vma, addr);
453
454	kernfs_put_active(of->kn);
455	return pol;
456}
457
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
458#endif
459
460static const struct vm_operations_struct kernfs_vm_ops = {
461	.open		= kernfs_vma_open,
462	.fault		= kernfs_vma_fault,
463	.page_mkwrite	= kernfs_vma_page_mkwrite,
464	.access		= kernfs_vma_access,
465#ifdef CONFIG_NUMA
466	.set_policy	= kernfs_vma_set_policy,
467	.get_policy	= kernfs_vma_get_policy,
 
468#endif
469};
470
471static int kernfs_fop_mmap(struct file *file, struct vm_area_struct *vma)
472{
473	struct kernfs_open_file *of = kernfs_of(file);
474	const struct kernfs_ops *ops;
475	int rc;
476
477	/*
478	 * mmap path and of->mutex are prone to triggering spurious lockdep
479	 * warnings and we don't want to add spurious locking dependency
480	 * between the two.  Check whether mmap is actually implemented
481	 * without grabbing @of->mutex by testing HAS_MMAP flag.  See the
482	 * comment in kernfs_file_open() for more details.
483	 */
484	if (!(of->kn->flags & KERNFS_HAS_MMAP))
485		return -ENODEV;
486
487	mutex_lock(&of->mutex);
488
489	rc = -ENODEV;
490	if (!kernfs_get_active(of->kn))
491		goto out_unlock;
492
493	ops = kernfs_ops(of->kn);
494	rc = ops->mmap(of, vma);
495	if (rc)
496		goto out_put;
497
498	/*
499	 * PowerPC's pci_mmap of legacy_mem uses shmem_zero_setup()
500	 * to satisfy versions of X which crash if the mmap fails: that
501	 * substitutes a new vm_file, and we don't then want bin_vm_ops.
502	 */
503	if (vma->vm_file != file)
504		goto out_put;
505
506	rc = -EINVAL;
507	if (of->mmapped && of->vm_ops != vma->vm_ops)
508		goto out_put;
509
510	/*
511	 * It is not possible to successfully wrap close.
512	 * So error if someone is trying to use close.
513	 */
514	rc = -EINVAL;
515	if (vma->vm_ops && vma->vm_ops->close)
516		goto out_put;
517
518	rc = 0;
519	of->mmapped = 1;
520	of->vm_ops = vma->vm_ops;
521	vma->vm_ops = &kernfs_vm_ops;
522out_put:
523	kernfs_put_active(of->kn);
524out_unlock:
525	mutex_unlock(&of->mutex);
526
527	return rc;
528}
529
530/**
531 *	kernfs_get_open_node - get or create kernfs_open_node
532 *	@kn: target kernfs_node
533 *	@of: kernfs_open_file for this instance of open
534 *
535 *	If @kn->attr.open exists, increment its reference count; otherwise,
536 *	create one.  @of is chained to the files list.
537 *
538 *	LOCKING:
539 *	Kernel thread context (may sleep).
540 *
541 *	RETURNS:
542 *	0 on success, -errno on failure.
543 */
544static int kernfs_get_open_node(struct kernfs_node *kn,
545				struct kernfs_open_file *of)
546{
547	struct kernfs_open_node *on, *new_on = NULL;
548
549 retry:
550	mutex_lock(&kernfs_open_file_mutex);
551	spin_lock_irq(&kernfs_open_node_lock);
552
553	if (!kn->attr.open && new_on) {
554		kn->attr.open = new_on;
555		new_on = NULL;
556	}
557
558	on = kn->attr.open;
559	if (on) {
560		atomic_inc(&on->refcnt);
561		list_add_tail(&of->list, &on->files);
562	}
563
564	spin_unlock_irq(&kernfs_open_node_lock);
565	mutex_unlock(&kernfs_open_file_mutex);
566
567	if (on) {
568		kfree(new_on);
569		return 0;
570	}
571
572	/* not there, initialize a new one and retry */
573	new_on = kmalloc(sizeof(*new_on), GFP_KERNEL);
574	if (!new_on)
575		return -ENOMEM;
576
577	atomic_set(&new_on->refcnt, 0);
578	atomic_set(&new_on->event, 1);
579	init_waitqueue_head(&new_on->poll);
580	INIT_LIST_HEAD(&new_on->files);
581	goto retry;
582}
583
584/**
585 *	kernfs_put_open_node - put kernfs_open_node
586 *	@kn: target kernfs_nodet
587 *	@of: associated kernfs_open_file
588 *
589 *	Put @kn->attr.open and unlink @of from the files list.  If
590 *	reference count reaches zero, disassociate and free it.
591 *
592 *	LOCKING:
593 *	None.
594 */
595static void kernfs_put_open_node(struct kernfs_node *kn,
596				 struct kernfs_open_file *of)
597{
598	struct kernfs_open_node *on = kn->attr.open;
599	unsigned long flags;
600
601	mutex_lock(&kernfs_open_file_mutex);
602	spin_lock_irqsave(&kernfs_open_node_lock, flags);
603
604	if (of)
605		list_del(&of->list);
606
607	if (atomic_dec_and_test(&on->refcnt))
608		kn->attr.open = NULL;
609	else
610		on = NULL;
611
612	spin_unlock_irqrestore(&kernfs_open_node_lock, flags);
613	mutex_unlock(&kernfs_open_file_mutex);
614
615	kfree(on);
616}
617
618static int kernfs_fop_open(struct inode *inode, struct file *file)
619{
620	struct kernfs_node *kn = file->f_path.dentry->d_fsdata;
621	struct kernfs_root *root = kernfs_root(kn);
622	const struct kernfs_ops *ops;
623	struct kernfs_open_file *of;
624	bool has_read, has_write, has_mmap;
625	int error = -EACCES;
626
627	if (!kernfs_get_active(kn))
628		return -ENODEV;
629
630	ops = kernfs_ops(kn);
631
632	has_read = ops->seq_show || ops->read || ops->mmap;
633	has_write = ops->write || ops->mmap;
634	has_mmap = ops->mmap;
635
636	/* see the flag definition for details */
637	if (root->flags & KERNFS_ROOT_EXTRA_OPEN_PERM_CHECK) {
638		if ((file->f_mode & FMODE_WRITE) &&
639		    (!(inode->i_mode & S_IWUGO) || !has_write))
640			goto err_out;
641
642		if ((file->f_mode & FMODE_READ) &&
643		    (!(inode->i_mode & S_IRUGO) || !has_read))
644			goto err_out;
645	}
646
647	/* allocate a kernfs_open_file for the file */
648	error = -ENOMEM;
649	of = kzalloc(sizeof(struct kernfs_open_file), GFP_KERNEL);
650	if (!of)
651		goto err_out;
652
653	/*
654	 * The following is done to give a different lockdep key to
655	 * @of->mutex for files which implement mmap.  This is a rather
656	 * crude way to avoid false positive lockdep warning around
657	 * mm->mmap_sem - mmap nests @of->mutex under mm->mmap_sem and
658	 * reading /sys/block/sda/trace/act_mask grabs sr_mutex, under
659	 * which mm->mmap_sem nests, while holding @of->mutex.  As each
660	 * open file has a separate mutex, it's okay as long as those don't
661	 * happen on the same file.  At this point, we can't easily give
662	 * each file a separate locking class.  Let's differentiate on
663	 * whether the file has mmap or not for now.
664	 *
665	 * Both paths of the branch look the same.  They're supposed to
666	 * look that way and give @of->mutex different static lockdep keys.
667	 */
668	if (has_mmap)
669		mutex_init(&of->mutex);
670	else
671		mutex_init(&of->mutex);
672
673	of->kn = kn;
674	of->file = file;
675
676	/*
677	 * Write path needs to atomic_write_len outside active reference.
678	 * Cache it in open_file.  See kernfs_fop_write() for details.
679	 */
680	of->atomic_write_len = ops->atomic_write_len;
681
682	error = -EINVAL;
683	/*
684	 * ->seq_show is incompatible with ->prealloc,
685	 * as seq_read does its own allocation.
686	 * ->read must be used instead.
687	 */
688	if (ops->prealloc && ops->seq_show)
689		goto err_free;
690	if (ops->prealloc) {
691		int len = of->atomic_write_len ?: PAGE_SIZE;
692		of->prealloc_buf = kmalloc(len + 1, GFP_KERNEL);
693		error = -ENOMEM;
694		if (!of->prealloc_buf)
695			goto err_free;
696		mutex_init(&of->prealloc_mutex);
697	}
698
699	/*
700	 * Always instantiate seq_file even if read access doesn't use
701	 * seq_file or is not requested.  This unifies private data access
702	 * and readable regular files are the vast majority anyway.
703	 */
704	if (ops->seq_show)
705		error = seq_open(file, &kernfs_seq_ops);
706	else
707		error = seq_open(file, NULL);
708	if (error)
709		goto err_free;
710
711	((struct seq_file *)file->private_data)->private = of;
712
713	/* seq_file clears PWRITE unconditionally, restore it if WRITE */
714	if (file->f_mode & FMODE_WRITE)
715		file->f_mode |= FMODE_PWRITE;
716
717	/* make sure we have open node struct */
718	error = kernfs_get_open_node(kn, of);
719	if (error)
720		goto err_close;
721
722	/* open succeeded, put active references */
723	kernfs_put_active(kn);
724	return 0;
725
726err_close:
727	seq_release(inode, file);
728err_free:
729	kfree(of->prealloc_buf);
730	kfree(of);
731err_out:
732	kernfs_put_active(kn);
733	return error;
734}
735
736static int kernfs_fop_release(struct inode *inode, struct file *filp)
737{
738	struct kernfs_node *kn = filp->f_path.dentry->d_fsdata;
739	struct kernfs_open_file *of = kernfs_of(filp);
740
741	kernfs_put_open_node(kn, of);
742	seq_release(inode, filp);
743	kfree(of->prealloc_buf);
744	kfree(of);
745
746	return 0;
747}
748
749void kernfs_unmap_bin_file(struct kernfs_node *kn)
750{
751	struct kernfs_open_node *on;
752	struct kernfs_open_file *of;
753
754	if (!(kn->flags & KERNFS_HAS_MMAP))
755		return;
756
757	spin_lock_irq(&kernfs_open_node_lock);
758	on = kn->attr.open;
759	if (on)
760		atomic_inc(&on->refcnt);
761	spin_unlock_irq(&kernfs_open_node_lock);
762	if (!on)
763		return;
764
765	mutex_lock(&kernfs_open_file_mutex);
766	list_for_each_entry(of, &on->files, list) {
767		struct inode *inode = file_inode(of->file);
768		unmap_mapping_range(inode->i_mapping, 0, 0, 1);
769	}
770	mutex_unlock(&kernfs_open_file_mutex);
771
772	kernfs_put_open_node(kn, NULL);
773}
774
775/*
776 * Kernfs attribute files are pollable.  The idea is that you read
777 * the content and then you use 'poll' or 'select' to wait for
778 * the content to change.  When the content changes (assuming the
779 * manager for the kobject supports notification), poll will
780 * return POLLERR|POLLPRI, and select will return the fd whether
781 * it is waiting for read, write, or exceptions.
782 * Once poll/select indicates that the value has changed, you
783 * need to close and re-open the file, or seek to 0 and read again.
784 * Reminder: this only works for attributes which actively support
785 * it, and it is not possible to test an attribute from userspace
786 * to see if it supports poll (Neither 'poll' nor 'select' return
787 * an appropriate error code).  When in doubt, set a suitable timeout value.
788 */
789static unsigned int kernfs_fop_poll(struct file *filp, poll_table *wait)
790{
791	struct kernfs_open_file *of = kernfs_of(filp);
792	struct kernfs_node *kn = filp->f_path.dentry->d_fsdata;
793	struct kernfs_open_node *on = kn->attr.open;
794
 
795	if (!kernfs_get_active(kn))
796		goto trigger;
797
798	poll_wait(filp, &on->poll, wait);
799
800	kernfs_put_active(kn);
801
802	if (of->event != atomic_read(&on->event))
803		goto trigger;
804
805	return DEFAULT_POLLMASK;
806
807 trigger:
808	return DEFAULT_POLLMASK|POLLERR|POLLPRI;
809}
810
811static void kernfs_notify_workfn(struct work_struct *work)
812{
813	struct kernfs_node *kn;
814	struct kernfs_open_node *on;
815	struct kernfs_super_info *info;
816repeat:
817	/* pop one off the notify_list */
818	spin_lock_irq(&kernfs_notify_lock);
819	kn = kernfs_notify_list;
820	if (kn == KERNFS_NOTIFY_EOL) {
821		spin_unlock_irq(&kernfs_notify_lock);
822		return;
823	}
824	kernfs_notify_list = kn->attr.notify_next;
825	kn->attr.notify_next = NULL;
826	spin_unlock_irq(&kernfs_notify_lock);
827
828	/* kick poll */
829	spin_lock_irq(&kernfs_open_node_lock);
830
831	on = kn->attr.open;
832	if (on) {
833		atomic_inc(&on->event);
834		wake_up_interruptible(&on->poll);
835	}
836
837	spin_unlock_irq(&kernfs_open_node_lock);
838
839	/* kick fsnotify */
840	mutex_lock(&kernfs_mutex);
841
842	list_for_each_entry(info, &kernfs_root(kn)->supers, node) {
843		struct kernfs_node *parent;
844		struct inode *inode;
845
846		/*
847		 * We want fsnotify_modify() on @kn but as the
848		 * modifications aren't originating from userland don't
849		 * have the matching @file available.  Look up the inodes
850		 * and generate the events manually.
851		 */
852		inode = ilookup(info->sb, kn->ino);
853		if (!inode)
854			continue;
855
856		parent = kernfs_get_parent(kn);
857		if (parent) {
858			struct inode *p_inode;
859
860			p_inode = ilookup(info->sb, parent->ino);
861			if (p_inode) {
862				fsnotify(p_inode, FS_MODIFY | FS_EVENT_ON_CHILD,
863					 inode, FSNOTIFY_EVENT_INODE, kn->name, 0);
864				iput(p_inode);
865			}
866
867			kernfs_put(parent);
868		}
869
870		fsnotify(inode, FS_MODIFY, inode, FSNOTIFY_EVENT_INODE,
871			 kn->name, 0);
872		iput(inode);
873	}
874
875	mutex_unlock(&kernfs_mutex);
876	kernfs_put(kn);
877	goto repeat;
878}
879
880/**
881 * kernfs_notify - notify a kernfs file
882 * @kn: file to notify
883 *
884 * Notify @kn such that poll(2) on @kn wakes up.  Maybe be called from any
885 * context.
886 */
887void kernfs_notify(struct kernfs_node *kn)
888{
889	static DECLARE_WORK(kernfs_notify_work, kernfs_notify_workfn);
890	unsigned long flags;
891
892	if (WARN_ON(kernfs_type(kn) != KERNFS_FILE))
893		return;
894
895	spin_lock_irqsave(&kernfs_notify_lock, flags);
896	if (!kn->attr.notify_next) {
897		kernfs_get(kn);
898		kn->attr.notify_next = kernfs_notify_list;
899		kernfs_notify_list = kn;
900		schedule_work(&kernfs_notify_work);
901	}
902	spin_unlock_irqrestore(&kernfs_notify_lock, flags);
 
903}
904EXPORT_SYMBOL_GPL(kernfs_notify);
905
906const struct file_operations kernfs_file_fops = {
907	.read		= kernfs_fop_read,
908	.write		= kernfs_fop_write,
909	.llseek		= generic_file_llseek,
910	.mmap		= kernfs_fop_mmap,
911	.open		= kernfs_fop_open,
912	.release	= kernfs_fop_release,
913	.poll		= kernfs_fop_poll,
914	.fsync		= noop_fsync,
915};
916
917/**
918 * __kernfs_create_file - kernfs internal function to create a file
919 * @parent: directory to create the file in
920 * @name: name of the file
921 * @mode: mode of the file
922 * @size: size of the file
923 * @ops: kernfs operations for the file
924 * @priv: private data for the file
925 * @ns: optional namespace tag of the file
 
926 * @key: lockdep key for the file's active_ref, %NULL to disable lockdep
927 *
928 * Returns the created node on success, ERR_PTR() value on error.
929 */
930struct kernfs_node *__kernfs_create_file(struct kernfs_node *parent,
931					 const char *name,
932					 umode_t mode, loff_t size,
933					 const struct kernfs_ops *ops,
934					 void *priv, const void *ns,
 
935					 struct lock_class_key *key)
936{
937	struct kernfs_node *kn;
938	unsigned flags;
939	int rc;
940
941	flags = KERNFS_FILE;
 
 
942
943	kn = kernfs_new_node(parent, name, (mode & S_IALLUGO) | S_IFREG, flags);
944	if (!kn)
945		return ERR_PTR(-ENOMEM);
946
947	kn->attr.ops = ops;
948	kn->attr.size = size;
949	kn->ns = ns;
950	kn->priv = priv;
951
952#ifdef CONFIG_DEBUG_LOCK_ALLOC
953	if (key) {
954		lockdep_init_map(&kn->dep_map, "s_active", key, 0);
955		kn->flags |= KERNFS_LOCKDEP;
956	}
957#endif
958
959	/*
960	 * kn->attr.ops is accesible only while holding active ref.  We
961	 * need to know whether some ops are implemented outside active
962	 * ref.  Cache their existence in flags.
963	 */
964	if (ops->seq_show)
965		kn->flags |= KERNFS_HAS_SEQ_SHOW;
966	if (ops->mmap)
967		kn->flags |= KERNFS_HAS_MMAP;
968
969	rc = kernfs_add_one(kn);
970	if (rc) {
971		kernfs_put(kn);
972		return ERR_PTR(rc);
973	}
974	return kn;
975}