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TOMOYO Linux Cross Reference
Linux/kernel/relay.c

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  1 /*
  2  * Public API and common code for kernel->userspace relay file support.
  3  *
  4  * See Documentation/filesystems/relay.txt for an overview.
  5  *
  6  * Copyright (C) 2002-2005 - Tom Zanussi (zanussi@us.ibm.com), IBM Corp
  7  * Copyright (C) 1999-2005 - Karim Yaghmour (karim@opersys.com)
  8  *
  9  * Moved to kernel/relay.c by Paul Mundt, 2006.
 10  * November 2006 - CPU hotplug support by Mathieu Desnoyers
 11  *      (mathieu.desnoyers@polymtl.ca)
 12  *
 13  * This file is released under the GPL.
 14  */
 15 #include <linux/errno.h>
 16 #include <linux/stddef.h>
 17 #include <linux/slab.h>
 18 #include <linux/export.h>
 19 #include <linux/string.h>
 20 #include <linux/relay.h>
 21 #include <linux/vmalloc.h>
 22 #include <linux/mm.h>
 23 #include <linux/cpu.h>
 24 #include <linux/splice.h>
 25 
 26 /* list of open channels, for cpu hotplug */
 27 static DEFINE_MUTEX(relay_channels_mutex);
 28 static LIST_HEAD(relay_channels);
 29 
 30 /*
 31  * close() vm_op implementation for relay file mapping.
 32  */
 33 static void relay_file_mmap_close(struct vm_area_struct *vma)
 34 {
 35         struct rchan_buf *buf = vma->vm_private_data;
 36         buf->chan->cb->buf_unmapped(buf, vma->vm_file);
 37 }
 38 
 39 /*
 40  * fault() vm_op implementation for relay file mapping.
 41  */
 42 static vm_fault_t relay_buf_fault(struct vm_fault *vmf)
 43 {
 44         struct page *page;
 45         struct rchan_buf *buf = vmf->vma->vm_private_data;
 46         pgoff_t pgoff = vmf->pgoff;
 47 
 48         if (!buf)
 49                 return VM_FAULT_OOM;
 50 
 51         page = vmalloc_to_page(buf->start + (pgoff << PAGE_SHIFT));
 52         if (!page)
 53                 return VM_FAULT_SIGBUS;
 54         get_page(page);
 55         vmf->page = page;
 56 
 57         return 0;
 58 }
 59 
 60 /*
 61  * vm_ops for relay file mappings.
 62  */
 63 static const struct vm_operations_struct relay_file_mmap_ops = {
 64         .fault = relay_buf_fault,
 65         .close = relay_file_mmap_close,
 66 };
 67 
 68 /*
 69  * allocate an array of pointers of struct page
 70  */
 71 static struct page **relay_alloc_page_array(unsigned int n_pages)
 72 {
 73         const size_t pa_size = n_pages * sizeof(struct page *);
 74         if (pa_size > PAGE_SIZE)
 75                 return vzalloc(pa_size);
 76         return kzalloc(pa_size, GFP_KERNEL);
 77 }
 78 
 79 /*
 80  * free an array of pointers of struct page
 81  */
 82 static void relay_free_page_array(struct page **array)
 83 {
 84         kvfree(array);
 85 }
 86 
 87 /**
 88  *      relay_mmap_buf: - mmap channel buffer to process address space
 89  *      @buf: relay channel buffer
 90  *      @vma: vm_area_struct describing memory to be mapped
 91  *
 92  *      Returns 0 if ok, negative on error
 93  *
 94  *      Caller should already have grabbed mmap_sem.
 95  */
 96 static int relay_mmap_buf(struct rchan_buf *buf, struct vm_area_struct *vma)
 97 {
 98         unsigned long length = vma->vm_end - vma->vm_start;
 99         struct file *filp = vma->vm_file;
100 
101         if (!buf)
102                 return -EBADF;
103 
104         if (length != (unsigned long)buf->chan->alloc_size)
105                 return -EINVAL;
106 
107         vma->vm_ops = &relay_file_mmap_ops;
108         vma->vm_flags |= VM_DONTEXPAND;
109         vma->vm_private_data = buf;
110         buf->chan->cb->buf_mapped(buf, filp);
111 
112         return 0;
113 }
114 
115 /**
116  *      relay_alloc_buf - allocate a channel buffer
117  *      @buf: the buffer struct
118  *      @size: total size of the buffer
119  *
120  *      Returns a pointer to the resulting buffer, %NULL if unsuccessful. The
121  *      passed in size will get page aligned, if it isn't already.
122  */
123 static void *relay_alloc_buf(struct rchan_buf *buf, size_t *size)
124 {
125         void *mem;
126         unsigned int i, j, n_pages;
127 
128         *size = PAGE_ALIGN(*size);
129         n_pages = *size >> PAGE_SHIFT;
130 
131         buf->page_array = relay_alloc_page_array(n_pages);
132         if (!buf->page_array)
133                 return NULL;
134 
135         for (i = 0; i < n_pages; i++) {
136                 buf->page_array[i] = alloc_page(GFP_KERNEL);
137                 if (unlikely(!buf->page_array[i]))
138                         goto depopulate;
139                 set_page_private(buf->page_array[i], (unsigned long)buf);
140         }
141         mem = vmap(buf->page_array, n_pages, VM_MAP, PAGE_KERNEL);
142         if (!mem)
143                 goto depopulate;
144 
145         memset(mem, 0, *size);
146         buf->page_count = n_pages;
147         return mem;
148 
149 depopulate:
150         for (j = 0; j < i; j++)
151                 __free_page(buf->page_array[j]);
152         relay_free_page_array(buf->page_array);
153         return NULL;
154 }
155 
156 /**
157  *      relay_create_buf - allocate and initialize a channel buffer
158  *      @chan: the relay channel
159  *
160  *      Returns channel buffer if successful, %NULL otherwise.
161  */
162 static struct rchan_buf *relay_create_buf(struct rchan *chan)
163 {
164         struct rchan_buf *buf;
165 
166         if (chan->n_subbufs > KMALLOC_MAX_SIZE / sizeof(size_t *))
167                 return NULL;
168 
169         buf = kzalloc(sizeof(struct rchan_buf), GFP_KERNEL);
170         if (!buf)
171                 return NULL;
172         buf->padding = kmalloc_array(chan->n_subbufs, sizeof(size_t *),
173                                      GFP_KERNEL);
174         if (!buf->padding)
175                 goto free_buf;
176 
177         buf->start = relay_alloc_buf(buf, &chan->alloc_size);
178         if (!buf->start)
179                 goto free_buf;
180 
181         buf->chan = chan;
182         kref_get(&buf->chan->kref);
183         return buf;
184 
185 free_buf:
186         kfree(buf->padding);
187         kfree(buf);
188         return NULL;
189 }
190 
191 /**
192  *      relay_destroy_channel - free the channel struct
193  *      @kref: target kernel reference that contains the relay channel
194  *
195  *      Should only be called from kref_put().
196  */
197 static void relay_destroy_channel(struct kref *kref)
198 {
199         struct rchan *chan = container_of(kref, struct rchan, kref);
200         free_percpu(chan->buf);
201         kfree(chan);
202 }
203 
204 /**
205  *      relay_destroy_buf - destroy an rchan_buf struct and associated buffer
206  *      @buf: the buffer struct
207  */
208 static void relay_destroy_buf(struct rchan_buf *buf)
209 {
210         struct rchan *chan = buf->chan;
211         unsigned int i;
212 
213         if (likely(buf->start)) {
214                 vunmap(buf->start);
215                 for (i = 0; i < buf->page_count; i++)
216                         __free_page(buf->page_array[i]);
217                 relay_free_page_array(buf->page_array);
218         }
219         *per_cpu_ptr(chan->buf, buf->cpu) = NULL;
220         kfree(buf->padding);
221         kfree(buf);
222         kref_put(&chan->kref, relay_destroy_channel);
223 }
224 
225 /**
226  *      relay_remove_buf - remove a channel buffer
227  *      @kref: target kernel reference that contains the relay buffer
228  *
229  *      Removes the file from the filesystem, which also frees the
230  *      rchan_buf_struct and the channel buffer.  Should only be called from
231  *      kref_put().
232  */
233 static void relay_remove_buf(struct kref *kref)
234 {
235         struct rchan_buf *buf = container_of(kref, struct rchan_buf, kref);
236         relay_destroy_buf(buf);
237 }
238 
239 /**
240  *      relay_buf_empty - boolean, is the channel buffer empty?
241  *      @buf: channel buffer
242  *
243  *      Returns 1 if the buffer is empty, 0 otherwise.
244  */
245 static int relay_buf_empty(struct rchan_buf *buf)
246 {
247         return (buf->subbufs_produced - buf->subbufs_consumed) ? 0 : 1;
248 }
249 
250 /**
251  *      relay_buf_full - boolean, is the channel buffer full?
252  *      @buf: channel buffer
253  *
254  *      Returns 1 if the buffer is full, 0 otherwise.
255  */
256 int relay_buf_full(struct rchan_buf *buf)
257 {
258         size_t ready = buf->subbufs_produced - buf->subbufs_consumed;
259         return (ready >= buf->chan->n_subbufs) ? 1 : 0;
260 }
261 EXPORT_SYMBOL_GPL(relay_buf_full);
262 
263 /*
264  * High-level relay kernel API and associated functions.
265  */
266 
267 /*
268  * rchan_callback implementations defining default channel behavior.  Used
269  * in place of corresponding NULL values in client callback struct.
270  */
271 
272 /*
273  * subbuf_start() default callback.  Does nothing.
274  */
275 static int subbuf_start_default_callback (struct rchan_buf *buf,
276                                           void *subbuf,
277                                           void *prev_subbuf,
278                                           size_t prev_padding)
279 {
280         if (relay_buf_full(buf))
281                 return 0;
282 
283         return 1;
284 }
285 
286 /*
287  * buf_mapped() default callback.  Does nothing.
288  */
289 static void buf_mapped_default_callback(struct rchan_buf *buf,
290                                         struct file *filp)
291 {
292 }
293 
294 /*
295  * buf_unmapped() default callback.  Does nothing.
296  */
297 static void buf_unmapped_default_callback(struct rchan_buf *buf,
298                                           struct file *filp)
299 {
300 }
301 
302 /*
303  * create_buf_file_create() default callback.  Does nothing.
304  */
305 static struct dentry *create_buf_file_default_callback(const char *filename,
306                                                        struct dentry *parent,
307                                                        umode_t mode,
308                                                        struct rchan_buf *buf,
309                                                        int *is_global)
310 {
311         return NULL;
312 }
313 
314 /*
315  * remove_buf_file() default callback.  Does nothing.
316  */
317 static int remove_buf_file_default_callback(struct dentry *dentry)
318 {
319         return -EINVAL;
320 }
321 
322 /* relay channel default callbacks */
323 static struct rchan_callbacks default_channel_callbacks = {
324         .subbuf_start = subbuf_start_default_callback,
325         .buf_mapped = buf_mapped_default_callback,
326         .buf_unmapped = buf_unmapped_default_callback,
327         .create_buf_file = create_buf_file_default_callback,
328         .remove_buf_file = remove_buf_file_default_callback,
329 };
330 
331 /**
332  *      wakeup_readers - wake up readers waiting on a channel
333  *      @work: contains the channel buffer
334  *
335  *      This is the function used to defer reader waking
336  */
337 static void wakeup_readers(struct irq_work *work)
338 {
339         struct rchan_buf *buf;
340 
341         buf = container_of(work, struct rchan_buf, wakeup_work);
342         wake_up_interruptible(&buf->read_wait);
343 }
344 
345 /**
346  *      __relay_reset - reset a channel buffer
347  *      @buf: the channel buffer
348  *      @init: 1 if this is a first-time initialization
349  *
350  *      See relay_reset() for description of effect.
351  */
352 static void __relay_reset(struct rchan_buf *buf, unsigned int init)
353 {
354         size_t i;
355 
356         if (init) {
357                 init_waitqueue_head(&buf->read_wait);
358                 kref_init(&buf->kref);
359                 init_irq_work(&buf->wakeup_work, wakeup_readers);
360         } else {
361                 irq_work_sync(&buf->wakeup_work);
362         }
363 
364         buf->subbufs_produced = 0;
365         buf->subbufs_consumed = 0;
366         buf->bytes_consumed = 0;
367         buf->finalized = 0;
368         buf->data = buf->start;
369         buf->offset = 0;
370 
371         for (i = 0; i < buf->chan->n_subbufs; i++)
372                 buf->padding[i] = 0;
373 
374         buf->chan->cb->subbuf_start(buf, buf->data, NULL, 0);
375 }
376 
377 /**
378  *      relay_reset - reset the channel
379  *      @chan: the channel
380  *
381  *      This has the effect of erasing all data from all channel buffers
382  *      and restarting the channel in its initial state.  The buffers
383  *      are not freed, so any mappings are still in effect.
384  *
385  *      NOTE. Care should be taken that the channel isn't actually
386  *      being used by anything when this call is made.
387  */
388 void relay_reset(struct rchan *chan)
389 {
390         struct rchan_buf *buf;
391         unsigned int i;
392 
393         if (!chan)
394                 return;
395 
396         if (chan->is_global && (buf = *per_cpu_ptr(chan->buf, 0))) {
397                 __relay_reset(buf, 0);
398                 return;
399         }
400 
401         mutex_lock(&relay_channels_mutex);
402         for_each_possible_cpu(i)
403                 if ((buf = *per_cpu_ptr(chan->buf, i)))
404                         __relay_reset(buf, 0);
405         mutex_unlock(&relay_channels_mutex);
406 }
407 EXPORT_SYMBOL_GPL(relay_reset);
408 
409 static inline void relay_set_buf_dentry(struct rchan_buf *buf,
410                                         struct dentry *dentry)
411 {
412         buf->dentry = dentry;
413         d_inode(buf->dentry)->i_size = buf->early_bytes;
414 }
415 
416 static struct dentry *relay_create_buf_file(struct rchan *chan,
417                                             struct rchan_buf *buf,
418                                             unsigned int cpu)
419 {
420         struct dentry *dentry;
421         char *tmpname;
422 
423         tmpname = kzalloc(NAME_MAX + 1, GFP_KERNEL);
424         if (!tmpname)
425                 return NULL;
426         snprintf(tmpname, NAME_MAX, "%s%d", chan->base_filename, cpu);
427 
428         /* Create file in fs */
429         dentry = chan->cb->create_buf_file(tmpname, chan->parent,
430                                            S_IRUSR, buf,
431                                            &chan->is_global);
432         if (IS_ERR(dentry))
433                 dentry = NULL;
434 
435         kfree(tmpname);
436 
437         return dentry;
438 }
439 
440 /*
441  *      relay_open_buf - create a new relay channel buffer
442  *
443  *      used by relay_open() and CPU hotplug.
444  */
445 static struct rchan_buf *relay_open_buf(struct rchan *chan, unsigned int cpu)
446 {
447         struct rchan_buf *buf = NULL;
448         struct dentry *dentry;
449 
450         if (chan->is_global)
451                 return *per_cpu_ptr(chan->buf, 0);
452 
453         buf = relay_create_buf(chan);
454         if (!buf)
455                 return NULL;
456 
457         if (chan->has_base_filename) {
458                 dentry = relay_create_buf_file(chan, buf, cpu);
459                 if (!dentry)
460                         goto free_buf;
461                 relay_set_buf_dentry(buf, dentry);
462         } else {
463                 /* Only retrieve global info, nothing more, nothing less */
464                 dentry = chan->cb->create_buf_file(NULL, NULL,
465                                                    S_IRUSR, buf,
466                                                    &chan->is_global);
467                 if (IS_ERR_OR_NULL(dentry))
468                         goto free_buf;
469         }
470 
471         buf->cpu = cpu;
472         __relay_reset(buf, 1);
473 
474         if(chan->is_global) {
475                 *per_cpu_ptr(chan->buf, 0) = buf;
476                 buf->cpu = 0;
477         }
478 
479         return buf;
480 
481 free_buf:
482         relay_destroy_buf(buf);
483         return NULL;
484 }
485 
486 /**
487  *      relay_close_buf - close a channel buffer
488  *      @buf: channel buffer
489  *
490  *      Marks the buffer finalized and restores the default callbacks.
491  *      The channel buffer and channel buffer data structure are then freed
492  *      automatically when the last reference is given up.
493  */
494 static void relay_close_buf(struct rchan_buf *buf)
495 {
496         buf->finalized = 1;
497         irq_work_sync(&buf->wakeup_work);
498         buf->chan->cb->remove_buf_file(buf->dentry);
499         kref_put(&buf->kref, relay_remove_buf);
500 }
501 
502 static void setup_callbacks(struct rchan *chan,
503                                    struct rchan_callbacks *cb)
504 {
505         if (!cb) {
506                 chan->cb = &default_channel_callbacks;
507                 return;
508         }
509 
510         if (!cb->subbuf_start)
511                 cb->subbuf_start = subbuf_start_default_callback;
512         if (!cb->buf_mapped)
513                 cb->buf_mapped = buf_mapped_default_callback;
514         if (!cb->buf_unmapped)
515                 cb->buf_unmapped = buf_unmapped_default_callback;
516         if (!cb->create_buf_file)
517                 cb->create_buf_file = create_buf_file_default_callback;
518         if (!cb->remove_buf_file)
519                 cb->remove_buf_file = remove_buf_file_default_callback;
520         chan->cb = cb;
521 }
522 
523 int relay_prepare_cpu(unsigned int cpu)
524 {
525         struct rchan *chan;
526         struct rchan_buf *buf;
527 
528         mutex_lock(&relay_channels_mutex);
529         list_for_each_entry(chan, &relay_channels, list) {
530                 if ((buf = *per_cpu_ptr(chan->buf, cpu)))
531                         continue;
532                 buf = relay_open_buf(chan, cpu);
533                 if (!buf) {
534                         pr_err("relay: cpu %d buffer creation failed\n", cpu);
535                         mutex_unlock(&relay_channels_mutex);
536                         return -ENOMEM;
537                 }
538                 *per_cpu_ptr(chan->buf, cpu) = buf;
539         }
540         mutex_unlock(&relay_channels_mutex);
541         return 0;
542 }
543 
544 /**
545  *      relay_open - create a new relay channel
546  *      @base_filename: base name of files to create, %NULL for buffering only
547  *      @parent: dentry of parent directory, %NULL for root directory or buffer
548  *      @subbuf_size: size of sub-buffers
549  *      @n_subbufs: number of sub-buffers
550  *      @cb: client callback functions
551  *      @private_data: user-defined data
552  *
553  *      Returns channel pointer if successful, %NULL otherwise.
554  *
555  *      Creates a channel buffer for each cpu using the sizes and
556  *      attributes specified.  The created channel buffer files
557  *      will be named base_filename0...base_filenameN-1.  File
558  *      permissions will be %S_IRUSR.
559  *
560  *      If opening a buffer (@parent = NULL) that you later wish to register
561  *      in a filesystem, call relay_late_setup_files() once the @parent dentry
562  *      is available.
563  */
564 struct rchan *relay_open(const char *base_filename,
565                          struct dentry *parent,
566                          size_t subbuf_size,
567                          size_t n_subbufs,
568                          struct rchan_callbacks *cb,
569                          void *private_data)
570 {
571         unsigned int i;
572         struct rchan *chan;
573         struct rchan_buf *buf;
574 
575         if (!(subbuf_size && n_subbufs))
576                 return NULL;
577         if (subbuf_size > UINT_MAX / n_subbufs)
578                 return NULL;
579 
580         chan = kzalloc(sizeof(struct rchan), GFP_KERNEL);
581         if (!chan)
582                 return NULL;
583 
584         chan->buf = alloc_percpu(struct rchan_buf *);
585         if (!chan->buf) {
586                 kfree(chan);
587                 return NULL;
588         }
589 
590         chan->version = RELAYFS_CHANNEL_VERSION;
591         chan->n_subbufs = n_subbufs;
592         chan->subbuf_size = subbuf_size;
593         chan->alloc_size = PAGE_ALIGN(subbuf_size * n_subbufs);
594         chan->parent = parent;
595         chan->private_data = private_data;
596         if (base_filename) {
597                 chan->has_base_filename = 1;
598                 strlcpy(chan->base_filename, base_filename, NAME_MAX);
599         }
600         setup_callbacks(chan, cb);
601         kref_init(&chan->kref);
602 
603         mutex_lock(&relay_channels_mutex);
604         for_each_online_cpu(i) {
605                 buf = relay_open_buf(chan, i);
606                 if (!buf)
607                         goto free_bufs;
608                 *per_cpu_ptr(chan->buf, i) = buf;
609         }
610         list_add(&chan->list, &relay_channels);
611         mutex_unlock(&relay_channels_mutex);
612 
613         return chan;
614 
615 free_bufs:
616         for_each_possible_cpu(i) {
617                 if ((buf = *per_cpu_ptr(chan->buf, i)))
618                         relay_close_buf(buf);
619         }
620 
621         kref_put(&chan->kref, relay_destroy_channel);
622         mutex_unlock(&relay_channels_mutex);
623         return NULL;
624 }
625 EXPORT_SYMBOL_GPL(relay_open);
626 
627 struct rchan_percpu_buf_dispatcher {
628         struct rchan_buf *buf;
629         struct dentry *dentry;
630 };
631 
632 /* Called in atomic context. */
633 static void __relay_set_buf_dentry(void *info)
634 {
635         struct rchan_percpu_buf_dispatcher *p = info;
636 
637         relay_set_buf_dentry(p->buf, p->dentry);
638 }
639 
640 /**
641  *      relay_late_setup_files - triggers file creation
642  *      @chan: channel to operate on
643  *      @base_filename: base name of files to create
644  *      @parent: dentry of parent directory, %NULL for root directory
645  *
646  *      Returns 0 if successful, non-zero otherwise.
647  *
648  *      Use to setup files for a previously buffer-only channel created
649  *      by relay_open() with a NULL parent dentry.
650  *
651  *      For example, this is useful for perfomring early tracing in kernel,
652  *      before VFS is up and then exposing the early results once the dentry
653  *      is available.
654  */
655 int relay_late_setup_files(struct rchan *chan,
656                            const char *base_filename,
657                            struct dentry *parent)
658 {
659         int err = 0;
660         unsigned int i, curr_cpu;
661         unsigned long flags;
662         struct dentry *dentry;
663         struct rchan_buf *buf;
664         struct rchan_percpu_buf_dispatcher disp;
665 
666         if (!chan || !base_filename)
667                 return -EINVAL;
668 
669         strlcpy(chan->base_filename, base_filename, NAME_MAX);
670 
671         mutex_lock(&relay_channels_mutex);
672         /* Is chan already set up? */
673         if (unlikely(chan->has_base_filename)) {
674                 mutex_unlock(&relay_channels_mutex);
675                 return -EEXIST;
676         }
677         chan->has_base_filename = 1;
678         chan->parent = parent;
679 
680         if (chan->is_global) {
681                 err = -EINVAL;
682                 buf = *per_cpu_ptr(chan->buf, 0);
683                 if (!WARN_ON_ONCE(!buf)) {
684                         dentry = relay_create_buf_file(chan, buf, 0);
685                         if (dentry && !WARN_ON_ONCE(!chan->is_global)) {
686                                 relay_set_buf_dentry(buf, dentry);
687                                 err = 0;
688                         }
689                 }
690                 mutex_unlock(&relay_channels_mutex);
691                 return err;
692         }
693 
694         curr_cpu = get_cpu();
695         /*
696          * The CPU hotplug notifier ran before us and created buffers with
697          * no files associated. So it's safe to call relay_setup_buf_file()
698          * on all currently online CPUs.
699          */
700         for_each_online_cpu(i) {
701                 buf = *per_cpu_ptr(chan->buf, i);
702                 if (unlikely(!buf)) {
703                         WARN_ONCE(1, KERN_ERR "CPU has no buffer!\n");
704                         err = -EINVAL;
705                         break;
706                 }
707 
708                 dentry = relay_create_buf_file(chan, buf, i);
709                 if (unlikely(!dentry)) {
710                         err = -EINVAL;
711                         break;
712                 }
713 
714                 if (curr_cpu == i) {
715                         local_irq_save(flags);
716                         relay_set_buf_dentry(buf, dentry);
717                         local_irq_restore(flags);
718                 } else {
719                         disp.buf = buf;
720                         disp.dentry = dentry;
721                         smp_mb();
722                         /* relay_channels_mutex must be held, so wait. */
723                         err = smp_call_function_single(i,
724                                                        __relay_set_buf_dentry,
725                                                        &disp, 1);
726                 }
727                 if (unlikely(err))
728                         break;
729         }
730         put_cpu();
731         mutex_unlock(&relay_channels_mutex);
732 
733         return err;
734 }
735 EXPORT_SYMBOL_GPL(relay_late_setup_files);
736 
737 /**
738  *      relay_switch_subbuf - switch to a new sub-buffer
739  *      @buf: channel buffer
740  *      @length: size of current event
741  *
742  *      Returns either the length passed in or 0 if full.
743  *
744  *      Performs sub-buffer-switch tasks such as invoking callbacks,
745  *      updating padding counts, waking up readers, etc.
746  */
747 size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length)
748 {
749         void *old, *new;
750         size_t old_subbuf, new_subbuf;
751 
752         if (unlikely(length > buf->chan->subbuf_size))
753                 goto toobig;
754 
755         if (buf->offset != buf->chan->subbuf_size + 1) {
756                 buf->prev_padding = buf->chan->subbuf_size - buf->offset;
757                 old_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
758                 buf->padding[old_subbuf] = buf->prev_padding;
759                 buf->subbufs_produced++;
760                 if (buf->dentry)
761                         d_inode(buf->dentry)->i_size +=
762                                 buf->chan->subbuf_size -
763                                 buf->padding[old_subbuf];
764                 else
765                         buf->early_bytes += buf->chan->subbuf_size -
766                                             buf->padding[old_subbuf];
767                 smp_mb();
768                 if (waitqueue_active(&buf->read_wait)) {
769                         /*
770                          * Calling wake_up_interruptible() from here
771                          * will deadlock if we happen to be logging
772                          * from the scheduler (trying to re-grab
773                          * rq->lock), so defer it.
774                          */
775                         irq_work_queue(&buf->wakeup_work);
776                 }
777         }
778 
779         old = buf->data;
780         new_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
781         new = buf->start + new_subbuf * buf->chan->subbuf_size;
782         buf->offset = 0;
783         if (!buf->chan->cb->subbuf_start(buf, new, old, buf->prev_padding)) {
784                 buf->offset = buf->chan->subbuf_size + 1;
785                 return 0;
786         }
787         buf->data = new;
788         buf->padding[new_subbuf] = 0;
789 
790         if (unlikely(length + buf->offset > buf->chan->subbuf_size))
791                 goto toobig;
792 
793         return length;
794 
795 toobig:
796         buf->chan->last_toobig = length;
797         return 0;
798 }
799 EXPORT_SYMBOL_GPL(relay_switch_subbuf);
800 
801 /**
802  *      relay_subbufs_consumed - update the buffer's sub-buffers-consumed count
803  *      @chan: the channel
804  *      @cpu: the cpu associated with the channel buffer to update
805  *      @subbufs_consumed: number of sub-buffers to add to current buf's count
806  *
807  *      Adds to the channel buffer's consumed sub-buffer count.
808  *      subbufs_consumed should be the number of sub-buffers newly consumed,
809  *      not the total consumed.
810  *
811  *      NOTE. Kernel clients don't need to call this function if the channel
812  *      mode is 'overwrite'.
813  */
814 void relay_subbufs_consumed(struct rchan *chan,
815                             unsigned int cpu,
816                             size_t subbufs_consumed)
817 {
818         struct rchan_buf *buf;
819 
820         if (!chan || cpu >= NR_CPUS)
821                 return;
822 
823         buf = *per_cpu_ptr(chan->buf, cpu);
824         if (!buf || subbufs_consumed > chan->n_subbufs)
825                 return;
826 
827         if (subbufs_consumed > buf->subbufs_produced - buf->subbufs_consumed)
828                 buf->subbufs_consumed = buf->subbufs_produced;
829         else
830                 buf->subbufs_consumed += subbufs_consumed;
831 }
832 EXPORT_SYMBOL_GPL(relay_subbufs_consumed);
833 
834 /**
835  *      relay_close - close the channel
836  *      @chan: the channel
837  *
838  *      Closes all channel buffers and frees the channel.
839  */
840 void relay_close(struct rchan *chan)
841 {
842         struct rchan_buf *buf;
843         unsigned int i;
844 
845         if (!chan)
846                 return;
847 
848         mutex_lock(&relay_channels_mutex);
849         if (chan->is_global && (buf = *per_cpu_ptr(chan->buf, 0)))
850                 relay_close_buf(buf);
851         else
852                 for_each_possible_cpu(i)
853                         if ((buf = *per_cpu_ptr(chan->buf, i)))
854                                 relay_close_buf(buf);
855 
856         if (chan->last_toobig)
857                 printk(KERN_WARNING "relay: one or more items not logged "
858                        "[item size (%zd) > sub-buffer size (%zd)]\n",
859                        chan->last_toobig, chan->subbuf_size);
860 
861         list_del(&chan->list);
862         kref_put(&chan->kref, relay_destroy_channel);
863         mutex_unlock(&relay_channels_mutex);
864 }
865 EXPORT_SYMBOL_GPL(relay_close);
866 
867 /**
868  *      relay_flush - close the channel
869  *      @chan: the channel
870  *
871  *      Flushes all channel buffers, i.e. forces buffer switch.
872  */
873 void relay_flush(struct rchan *chan)
874 {
875         struct rchan_buf *buf;
876         unsigned int i;
877 
878         if (!chan)
879                 return;
880 
881         if (chan->is_global && (buf = *per_cpu_ptr(chan->buf, 0))) {
882                 relay_switch_subbuf(buf, 0);
883                 return;
884         }
885 
886         mutex_lock(&relay_channels_mutex);
887         for_each_possible_cpu(i)
888                 if ((buf = *per_cpu_ptr(chan->buf, i)))
889                         relay_switch_subbuf(buf, 0);
890         mutex_unlock(&relay_channels_mutex);
891 }
892 EXPORT_SYMBOL_GPL(relay_flush);
893 
894 /**
895  *      relay_file_open - open file op for relay files
896  *      @inode: the inode
897  *      @filp: the file
898  *
899  *      Increments the channel buffer refcount.
900  */
901 static int relay_file_open(struct inode *inode, struct file *filp)
902 {
903         struct rchan_buf *buf = inode->i_private;
904         kref_get(&buf->kref);
905         filp->private_data = buf;
906 
907         return nonseekable_open(inode, filp);
908 }
909 
910 /**
911  *      relay_file_mmap - mmap file op for relay files
912  *      @filp: the file
913  *      @vma: the vma describing what to map
914  *
915  *      Calls upon relay_mmap_buf() to map the file into user space.
916  */
917 static int relay_file_mmap(struct file *filp, struct vm_area_struct *vma)
918 {
919         struct rchan_buf *buf = filp->private_data;
920         return relay_mmap_buf(buf, vma);
921 }
922 
923 /**
924  *      relay_file_poll - poll file op for relay files
925  *      @filp: the file
926  *      @wait: poll table
927  *
928  *      Poll implemention.
929  */
930 static __poll_t relay_file_poll(struct file *filp, poll_table *wait)
931 {
932         __poll_t mask = 0;
933         struct rchan_buf *buf = filp->private_data;
934 
935         if (buf->finalized)
936                 return EPOLLERR;
937 
938         if (filp->f_mode & FMODE_READ) {
939                 poll_wait(filp, &buf->read_wait, wait);
940                 if (!relay_buf_empty(buf))
941                         mask |= EPOLLIN | EPOLLRDNORM;
942         }
943 
944         return mask;
945 }
946 
947 /**
948  *      relay_file_release - release file op for relay files
949  *      @inode: the inode
950  *      @filp: the file
951  *
952  *      Decrements the channel refcount, as the filesystem is
953  *      no longer using it.
954  */
955 static int relay_file_release(struct inode *inode, struct file *filp)
956 {
957         struct rchan_buf *buf = filp->private_data;
958         kref_put(&buf->kref, relay_remove_buf);
959 
960         return 0;
961 }
962 
963 /*
964  *      relay_file_read_consume - update the consumed count for the buffer
965  */
966 static void relay_file_read_consume(struct rchan_buf *buf,
967                                     size_t read_pos,
968                                     size_t bytes_consumed)
969 {
970         size_t subbuf_size = buf->chan->subbuf_size;
971         size_t n_subbufs = buf->chan->n_subbufs;
972         size_t read_subbuf;
973 
974         if (buf->subbufs_produced == buf->subbufs_consumed &&
975             buf->offset == buf->bytes_consumed)
976                 return;
977 
978         if (buf->bytes_consumed + bytes_consumed > subbuf_size) {
979                 relay_subbufs_consumed(buf->chan, buf->cpu, 1);
980                 buf->bytes_consumed = 0;
981         }
982 
983         buf->bytes_consumed += bytes_consumed;
984         if (!read_pos)
985                 read_subbuf = buf->subbufs_consumed % n_subbufs;
986         else
987                 read_subbuf = read_pos / buf->chan->subbuf_size;
988         if (buf->bytes_consumed + buf->padding[read_subbuf] == subbuf_size) {
989                 if ((read_subbuf == buf->subbufs_produced % n_subbufs) &&
990                     (buf->offset == subbuf_size))
991                         return;
992                 relay_subbufs_consumed(buf->chan, buf->cpu, 1);
993                 buf->bytes_consumed = 0;
994         }
995 }
996 
997 /*
998  *      relay_file_read_avail - boolean, are there unconsumed bytes available?
999  */
1000 static int relay_file_read_avail(struct rchan_buf *buf, size_t read_pos)
1001 {
1002         size_t subbuf_size = buf->chan->subbuf_size;
1003         size_t n_subbufs = buf->chan->n_subbufs;
1004         size_t produced = buf->subbufs_produced;
1005         size_t consumed = buf->subbufs_consumed;
1006 
1007         relay_file_read_consume(buf, read_pos, 0);
1008 
1009         consumed = buf->subbufs_consumed;
1010 
1011         if (unlikely(buf->offset > subbuf_size)) {
1012                 if (produced == consumed)
1013                         return 0;
1014                 return 1;
1015         }
1016 
1017         if (unlikely(produced - consumed >= n_subbufs)) {
1018                 consumed = produced - n_subbufs + 1;
1019                 buf->subbufs_consumed = consumed;
1020                 buf->bytes_consumed = 0;
1021         }
1022 
1023         produced = (produced % n_subbufs) * subbuf_size + buf->offset;
1024         consumed = (consumed % n_subbufs) * subbuf_size + buf->bytes_consumed;
1025 
1026         if (consumed > produced)
1027                 produced += n_subbufs * subbuf_size;
1028 
1029         if (consumed == produced) {
1030                 if (buf->offset == subbuf_size &&
1031                     buf->subbufs_produced > buf->subbufs_consumed)
1032                         return 1;
1033                 return 0;
1034         }
1035 
1036         return 1;
1037 }
1038 
1039 /**
1040  *      relay_file_read_subbuf_avail - return bytes available in sub-buffer
1041  *      @read_pos: file read position
1042  *      @buf: relay channel buffer
1043  */
1044 static size_t relay_file_read_subbuf_avail(size_t read_pos,
1045                                            struct rchan_buf *buf)
1046 {
1047         size_t padding, avail = 0;
1048         size_t read_subbuf, read_offset, write_subbuf, write_offset;
1049         size_t subbuf_size = buf->chan->subbuf_size;
1050 
1051         write_subbuf = (buf->data - buf->start) / subbuf_size;
1052         write_offset = buf->offset > subbuf_size ? subbuf_size : buf->offset;
1053         read_subbuf = read_pos / subbuf_size;
1054         read_offset = read_pos % subbuf_size;
1055         padding = buf->padding[read_subbuf];
1056 
1057         if (read_subbuf == write_subbuf) {
1058                 if (read_offset + padding < write_offset)
1059                         avail = write_offset - (read_offset + padding);
1060         } else
1061                 avail = (subbuf_size - padding) - read_offset;
1062 
1063         return avail;
1064 }
1065 
1066 /**
1067  *      relay_file_read_start_pos - find the first available byte to read
1068  *      @read_pos: file read position
1069  *      @buf: relay channel buffer
1070  *
1071  *      If the @read_pos is in the middle of padding, return the
1072  *      position of the first actually available byte, otherwise
1073  *      return the original value.
1074  */
1075 static size_t relay_file_read_start_pos(size_t read_pos,
1076                                         struct rchan_buf *buf)
1077 {
1078         size_t read_subbuf, padding, padding_start, padding_end;
1079         size_t subbuf_size = buf->chan->subbuf_size;
1080         size_t n_subbufs = buf->chan->n_subbufs;
1081         size_t consumed = buf->subbufs_consumed % n_subbufs;
1082 
1083         if (!read_pos)
1084                 read_pos = consumed * subbuf_size + buf->bytes_consumed;
1085         read_subbuf = read_pos / subbuf_size;
1086         padding = buf->padding[read_subbuf];
1087         padding_start = (read_subbuf + 1) * subbuf_size - padding;
1088         padding_end = (read_subbuf + 1) * subbuf_size;
1089         if (read_pos >= padding_start && read_pos < padding_end) {
1090                 read_subbuf = (read_subbuf + 1) % n_subbufs;
1091                 read_pos = read_subbuf * subbuf_size;
1092         }
1093 
1094         return read_pos;
1095 }
1096 
1097 /**
1098  *      relay_file_read_end_pos - return the new read position
1099  *      @read_pos: file read position
1100  *      @buf: relay channel buffer
1101  *      @count: number of bytes to be read
1102  */
1103 static size_t relay_file_read_end_pos(struct rchan_buf *buf,
1104                                       size_t read_pos,
1105                                       size_t count)
1106 {
1107         size_t read_subbuf, padding, end_pos;
1108         size_t subbuf_size = buf->chan->subbuf_size;
1109         size_t n_subbufs = buf->chan->n_subbufs;
1110 
1111         read_subbuf = read_pos / subbuf_size;
1112         padding = buf->padding[read_subbuf];
1113         if (read_pos % subbuf_size + count + padding == subbuf_size)
1114                 end_pos = (read_subbuf + 1) * subbuf_size;
1115         else
1116                 end_pos = read_pos + count;
1117         if (end_pos >= subbuf_size * n_subbufs)
1118                 end_pos = 0;
1119 
1120         return end_pos;
1121 }
1122 
1123 static ssize_t relay_file_read(struct file *filp,
1124                                char __user *buffer,
1125                                size_t count,
1126                                loff_t *ppos)
1127 {
1128         struct rchan_buf *buf = filp->private_data;
1129         size_t read_start, avail;
1130         size_t written = 0;
1131         int ret;
1132 
1133         if (!count)
1134                 return 0;
1135 
1136         inode_lock(file_inode(filp));
1137         do {
1138                 void *from;
1139 
1140                 if (!relay_file_read_avail(buf, *ppos))
1141                         break;
1142 
1143                 read_start = relay_file_read_start_pos(*ppos, buf);
1144                 avail = relay_file_read_subbuf_avail(read_start, buf);
1145                 if (!avail)
1146                         break;
1147 
1148                 avail = min(count, avail);
1149                 from = buf->start + read_start;
1150                 ret = avail;
1151                 if (copy_to_user(buffer, from, avail))
1152                         break;
1153 
1154                 buffer += ret;
1155                 written += ret;
1156                 count -= ret;
1157 
1158                 relay_file_read_consume(buf, read_start, ret);
1159                 *ppos = relay_file_read_end_pos(buf, read_start, ret);
1160         } while (count);
1161         inode_unlock(file_inode(filp));
1162 
1163         return written;
1164 }
1165 
1166 static void relay_consume_bytes(struct rchan_buf *rbuf, int bytes_consumed)
1167 {
1168         rbuf->bytes_consumed += bytes_consumed;
1169 
1170         if (rbuf->bytes_consumed >= rbuf->chan->subbuf_size) {
1171                 relay_subbufs_consumed(rbuf->chan, rbuf->cpu, 1);
1172                 rbuf->bytes_consumed %= rbuf->chan->subbuf_size;
1173         }
1174 }
1175 
1176 static void relay_pipe_buf_release(struct pipe_inode_info *pipe,
1177                                    struct pipe_buffer *buf)
1178 {
1179         struct rchan_buf *rbuf;
1180 
1181         rbuf = (struct rchan_buf *)page_private(buf->page);
1182         relay_consume_bytes(rbuf, buf->private);
1183 }
1184 
1185 static const struct pipe_buf_operations relay_pipe_buf_ops = {
1186         .confirm = generic_pipe_buf_confirm,
1187         .release = relay_pipe_buf_release,
1188         .steal = generic_pipe_buf_steal,
1189         .get = generic_pipe_buf_get,
1190 };
1191 
1192 static void relay_page_release(struct splice_pipe_desc *spd, unsigned int i)
1193 {
1194 }
1195 
1196 /*
1197  *      subbuf_splice_actor - splice up to one subbuf's worth of data
1198  */
1199 static ssize_t subbuf_splice_actor(struct file *in,
1200                                loff_t *ppos,
1201                                struct pipe_inode_info *pipe,
1202                                size_t len,
1203                                unsigned int flags,
1204                                int *nonpad_ret)
1205 {
1206         unsigned int pidx, poff, total_len, subbuf_pages, nr_pages;
1207         struct rchan_buf *rbuf = in->private_data;
1208         unsigned int subbuf_size = rbuf->chan->subbuf_size;
1209         uint64_t pos = (uint64_t) *ppos;
1210         uint32_t alloc_size = (uint32_t) rbuf->chan->alloc_size;
1211         size_t read_start = (size_t) do_div(pos, alloc_size);
1212         size_t read_subbuf = read_start / subbuf_size;
1213         size_t padding = rbuf->padding[read_subbuf];
1214         size_t nonpad_end = read_subbuf * subbuf_size + subbuf_size - padding;
1215         struct page *pages[PIPE_DEF_BUFFERS];
1216         struct partial_page partial[PIPE_DEF_BUFFERS];
1217         struct splice_pipe_desc spd = {
1218                 .pages = pages,
1219                 .nr_pages = 0,
1220                 .nr_pages_max = PIPE_DEF_BUFFERS,
1221                 .partial = partial,
1222                 .ops = &relay_pipe_buf_ops,
1223                 .spd_release = relay_page_release,
1224         };
1225         ssize_t ret;
1226 
1227         if (rbuf->subbufs_produced == rbuf->subbufs_consumed)
1228                 return 0;
1229         if (splice_grow_spd(pipe, &spd))
1230                 return -ENOMEM;
1231 
1232         /*
1233          * Adjust read len, if longer than what is available
1234          */
1235         if (len > (subbuf_size - read_start % subbuf_size))
1236                 len = subbuf_size - read_start % subbuf_size;
1237 
1238         subbuf_pages = rbuf->chan->alloc_size >> PAGE_SHIFT;
1239         pidx = (read_start / PAGE_SIZE) % subbuf_pages;
1240         poff = read_start & ~PAGE_MASK;
1241         nr_pages = min_t(unsigned int, subbuf_pages, spd.nr_pages_max);
1242 
1243         for (total_len = 0; spd.nr_pages < nr_pages; spd.nr_pages++) {
1244                 unsigned int this_len, this_end, private;
1245                 unsigned int cur_pos = read_start + total_len;
1246 
1247                 if (!len)
1248                         break;
1249 
1250                 this_len = min_t(unsigned long, len, PAGE_SIZE - poff);
1251                 private = this_len;
1252 
1253                 spd.pages[spd.nr_pages] = rbuf->page_array[pidx];
1254                 spd.partial[spd.nr_pages].offset = poff;
1255 
1256                 this_end = cur_pos + this_len;
1257                 if (this_end >= nonpad_end) {
1258                         this_len = nonpad_end - cur_pos;
1259                         private = this_len + padding;
1260                 }
1261                 spd.partial[spd.nr_pages].len = this_len;
1262                 spd.partial[spd.nr_pages].private = private;
1263 
1264                 len -= this_len;
1265                 total_len += this_len;
1266                 poff = 0;
1267                 pidx = (pidx + 1) % subbuf_pages;
1268 
1269                 if (this_end >= nonpad_end) {
1270                         spd.nr_pages++;
1271                         break;
1272                 }
1273         }
1274 
1275         ret = 0;
1276         if (!spd.nr_pages)
1277                 goto out;
1278 
1279         ret = *nonpad_ret = splice_to_pipe(pipe, &spd);
1280         if (ret < 0 || ret < total_len)
1281                 goto out;
1282 
1283         if (read_start + ret == nonpad_end)
1284                 ret += padding;
1285 
1286 out:
1287         splice_shrink_spd(&spd);
1288         return ret;
1289 }
1290 
1291 static ssize_t relay_file_splice_read(struct file *in,
1292                                       loff_t *ppos,
1293                                       struct pipe_inode_info *pipe,
1294                                       size_t len,
1295                                       unsigned int flags)
1296 {
1297         ssize_t spliced;
1298         int ret;
1299         int nonpad_ret = 0;
1300 
1301         ret = 0;
1302         spliced = 0;
1303 
1304         while (len && !spliced) {
1305                 ret = subbuf_splice_actor(in, ppos, pipe, len, flags, &nonpad_ret);
1306                 if (ret < 0)
1307                         break;
1308                 else if (!ret) {
1309                         if (flags & SPLICE_F_NONBLOCK)
1310                                 ret = -EAGAIN;
1311                         break;
1312                 }
1313 
1314                 *ppos += ret;
1315                 if (ret > len)
1316                         len = 0;
1317                 else
1318                         len -= ret;
1319                 spliced += nonpad_ret;
1320                 nonpad_ret = 0;
1321         }
1322 
1323         if (spliced)
1324                 return spliced;
1325 
1326         return ret;
1327 }
1328 
1329 const struct file_operations relay_file_operations = {
1330         .open           = relay_file_open,
1331         .poll           = relay_file_poll,
1332         .mmap           = relay_file_mmap,
1333         .read           = relay_file_read,
1334         .llseek         = no_llseek,
1335         .release        = relay_file_release,
1336         .splice_read    = relay_file_splice_read,
1337 };
1338 EXPORT_SYMBOL_GPL(relay_file_operations);
1339 

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