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TOMOYO Linux Cross Reference
Linux/fs/kernfs/file.c

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

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