Linux 4.15.6
[linux/fpc-iii.git] / kernel / events / ring_buffer.c
blob141aa2ca87288dfbf08c702c6edd2b411fe0b546
1 /*
2 * Performance events ring-buffer code:
4 * Copyright (C) 2008 Thomas Gleixner <tglx@linutronix.de>
5 * Copyright (C) 2008-2011 Red Hat, Inc., Ingo Molnar
6 * Copyright (C) 2008-2011 Red Hat, Inc., Peter Zijlstra
7 * Copyright © 2009 Paul Mackerras, IBM Corp. <paulus@au1.ibm.com>
9 * For licensing details see kernel-base/COPYING
12 #include <linux/perf_event.h>
13 #include <linux/vmalloc.h>
14 #include <linux/slab.h>
15 #include <linux/circ_buf.h>
16 #include <linux/poll.h>
18 #include "internal.h"
20 static void perf_output_wakeup(struct perf_output_handle *handle)
22 atomic_set(&handle->rb->poll, POLLIN);
24 handle->event->pending_wakeup = 1;
25 irq_work_queue(&handle->event->pending);
29 * We need to ensure a later event_id doesn't publish a head when a former
30 * event isn't done writing. However since we need to deal with NMIs we
31 * cannot fully serialize things.
33 * We only publish the head (and generate a wakeup) when the outer-most
34 * event completes.
36 static void perf_output_get_handle(struct perf_output_handle *handle)
38 struct ring_buffer *rb = handle->rb;
40 preempt_disable();
41 local_inc(&rb->nest);
42 handle->wakeup = local_read(&rb->wakeup);
45 static void perf_output_put_handle(struct perf_output_handle *handle)
47 struct ring_buffer *rb = handle->rb;
48 unsigned long head;
50 again:
51 head = local_read(&rb->head);
54 * IRQ/NMI can happen here, which means we can miss a head update.
57 if (!local_dec_and_test(&rb->nest))
58 goto out;
61 * Since the mmap() consumer (userspace) can run on a different CPU:
63 * kernel user
65 * if (LOAD ->data_tail) { LOAD ->data_head
66 * (A) smp_rmb() (C)
67 * STORE $data LOAD $data
68 * smp_wmb() (B) smp_mb() (D)
69 * STORE ->data_head STORE ->data_tail
70 * }
72 * Where A pairs with D, and B pairs with C.
74 * In our case (A) is a control dependency that separates the load of
75 * the ->data_tail and the stores of $data. In case ->data_tail
76 * indicates there is no room in the buffer to store $data we do not.
78 * D needs to be a full barrier since it separates the data READ
79 * from the tail WRITE.
81 * For B a WMB is sufficient since it separates two WRITEs, and for C
82 * an RMB is sufficient since it separates two READs.
84 * See perf_output_begin().
86 smp_wmb(); /* B, matches C */
87 rb->user_page->data_head = head;
90 * Now check if we missed an update -- rely on previous implied
91 * compiler barriers to force a re-read.
93 if (unlikely(head != local_read(&rb->head))) {
94 local_inc(&rb->nest);
95 goto again;
98 if (handle->wakeup != local_read(&rb->wakeup))
99 perf_output_wakeup(handle);
101 out:
102 preempt_enable();
105 static bool __always_inline
106 ring_buffer_has_space(unsigned long head, unsigned long tail,
107 unsigned long data_size, unsigned int size,
108 bool backward)
110 if (!backward)
111 return CIRC_SPACE(head, tail, data_size) >= size;
112 else
113 return CIRC_SPACE(tail, head, data_size) >= size;
116 static int __always_inline
117 __perf_output_begin(struct perf_output_handle *handle,
118 struct perf_event *event, unsigned int size,
119 bool backward)
121 struct ring_buffer *rb;
122 unsigned long tail, offset, head;
123 int have_lost, page_shift;
124 struct {
125 struct perf_event_header header;
126 u64 id;
127 u64 lost;
128 } lost_event;
130 rcu_read_lock();
132 * For inherited events we send all the output towards the parent.
134 if (event->parent)
135 event = event->parent;
137 rb = rcu_dereference(event->rb);
138 if (unlikely(!rb))
139 goto out;
141 if (unlikely(rb->paused)) {
142 if (rb->nr_pages)
143 local_inc(&rb->lost);
144 goto out;
147 handle->rb = rb;
148 handle->event = event;
150 have_lost = local_read(&rb->lost);
151 if (unlikely(have_lost)) {
152 size += sizeof(lost_event);
153 if (event->attr.sample_id_all)
154 size += event->id_header_size;
157 perf_output_get_handle(handle);
159 do {
160 tail = READ_ONCE(rb->user_page->data_tail);
161 offset = head = local_read(&rb->head);
162 if (!rb->overwrite) {
163 if (unlikely(!ring_buffer_has_space(head, tail,
164 perf_data_size(rb),
165 size, backward)))
166 goto fail;
170 * The above forms a control dependency barrier separating the
171 * @tail load above from the data stores below. Since the @tail
172 * load is required to compute the branch to fail below.
174 * A, matches D; the full memory barrier userspace SHOULD issue
175 * after reading the data and before storing the new tail
176 * position.
178 * See perf_output_put_handle().
181 if (!backward)
182 head += size;
183 else
184 head -= size;
185 } while (local_cmpxchg(&rb->head, offset, head) != offset);
187 if (backward) {
188 offset = head;
189 head = (u64)(-head);
193 * We rely on the implied barrier() by local_cmpxchg() to ensure
194 * none of the data stores below can be lifted up by the compiler.
197 if (unlikely(head - local_read(&rb->wakeup) > rb->watermark))
198 local_add(rb->watermark, &rb->wakeup);
200 page_shift = PAGE_SHIFT + page_order(rb);
202 handle->page = (offset >> page_shift) & (rb->nr_pages - 1);
203 offset &= (1UL << page_shift) - 1;
204 handle->addr = rb->data_pages[handle->page] + offset;
205 handle->size = (1UL << page_shift) - offset;
207 if (unlikely(have_lost)) {
208 struct perf_sample_data sample_data;
210 lost_event.header.size = sizeof(lost_event);
211 lost_event.header.type = PERF_RECORD_LOST;
212 lost_event.header.misc = 0;
213 lost_event.id = event->id;
214 lost_event.lost = local_xchg(&rb->lost, 0);
216 perf_event_header__init_id(&lost_event.header,
217 &sample_data, event);
218 perf_output_put(handle, lost_event);
219 perf_event__output_id_sample(event, handle, &sample_data);
222 return 0;
224 fail:
225 local_inc(&rb->lost);
226 perf_output_put_handle(handle);
227 out:
228 rcu_read_unlock();
230 return -ENOSPC;
233 int perf_output_begin_forward(struct perf_output_handle *handle,
234 struct perf_event *event, unsigned int size)
236 return __perf_output_begin(handle, event, size, false);
239 int perf_output_begin_backward(struct perf_output_handle *handle,
240 struct perf_event *event, unsigned int size)
242 return __perf_output_begin(handle, event, size, true);
245 int perf_output_begin(struct perf_output_handle *handle,
246 struct perf_event *event, unsigned int size)
249 return __perf_output_begin(handle, event, size,
250 unlikely(is_write_backward(event)));
253 unsigned int perf_output_copy(struct perf_output_handle *handle,
254 const void *buf, unsigned int len)
256 return __output_copy(handle, buf, len);
259 unsigned int perf_output_skip(struct perf_output_handle *handle,
260 unsigned int len)
262 return __output_skip(handle, NULL, len);
265 void perf_output_end(struct perf_output_handle *handle)
267 perf_output_put_handle(handle);
268 rcu_read_unlock();
271 static void
272 ring_buffer_init(struct ring_buffer *rb, long watermark, int flags)
274 long max_size = perf_data_size(rb);
276 if (watermark)
277 rb->watermark = min(max_size, watermark);
279 if (!rb->watermark)
280 rb->watermark = max_size / 2;
282 if (flags & RING_BUFFER_WRITABLE)
283 rb->overwrite = 0;
284 else
285 rb->overwrite = 1;
287 atomic_set(&rb->refcount, 1);
289 INIT_LIST_HEAD(&rb->event_list);
290 spin_lock_init(&rb->event_lock);
293 * perf_output_begin() only checks rb->paused, therefore
294 * rb->paused must be true if we have no pages for output.
296 if (!rb->nr_pages)
297 rb->paused = 1;
300 void perf_aux_output_flag(struct perf_output_handle *handle, u64 flags)
303 * OVERWRITE is determined by perf_aux_output_end() and can't
304 * be passed in directly.
306 if (WARN_ON_ONCE(flags & PERF_AUX_FLAG_OVERWRITE))
307 return;
309 handle->aux_flags |= flags;
311 EXPORT_SYMBOL_GPL(perf_aux_output_flag);
314 * This is called before hardware starts writing to the AUX area to
315 * obtain an output handle and make sure there's room in the buffer.
316 * When the capture completes, call perf_aux_output_end() to commit
317 * the recorded data to the buffer.
319 * The ordering is similar to that of perf_output_{begin,end}, with
320 * the exception of (B), which should be taken care of by the pmu
321 * driver, since ordering rules will differ depending on hardware.
323 * Call this from pmu::start(); see the comment in perf_aux_output_end()
324 * about its use in pmu callbacks. Both can also be called from the PMI
325 * handler if needed.
327 void *perf_aux_output_begin(struct perf_output_handle *handle,
328 struct perf_event *event)
330 struct perf_event *output_event = event;
331 unsigned long aux_head, aux_tail;
332 struct ring_buffer *rb;
334 if (output_event->parent)
335 output_event = output_event->parent;
338 * Since this will typically be open across pmu::add/pmu::del, we
339 * grab ring_buffer's refcount instead of holding rcu read lock
340 * to make sure it doesn't disappear under us.
342 rb = ring_buffer_get(output_event);
343 if (!rb)
344 return NULL;
346 if (!rb_has_aux(rb))
347 goto err;
350 * If aux_mmap_count is zero, the aux buffer is in perf_mmap_close(),
351 * about to get freed, so we leave immediately.
353 * Checking rb::aux_mmap_count and rb::refcount has to be done in
354 * the same order, see perf_mmap_close. Otherwise we end up freeing
355 * aux pages in this path, which is a bug, because in_atomic().
357 if (!atomic_read(&rb->aux_mmap_count))
358 goto err;
360 if (!atomic_inc_not_zero(&rb->aux_refcount))
361 goto err;
364 * Nesting is not supported for AUX area, make sure nested
365 * writers are caught early
367 if (WARN_ON_ONCE(local_xchg(&rb->aux_nest, 1)))
368 goto err_put;
370 aux_head = rb->aux_head;
372 handle->rb = rb;
373 handle->event = event;
374 handle->head = aux_head;
375 handle->size = 0;
376 handle->aux_flags = 0;
379 * In overwrite mode, AUX data stores do not depend on aux_tail,
380 * therefore (A) control dependency barrier does not exist. The
381 * (B) <-> (C) ordering is still observed by the pmu driver.
383 if (!rb->aux_overwrite) {
384 aux_tail = READ_ONCE(rb->user_page->aux_tail);
385 handle->wakeup = rb->aux_wakeup + rb->aux_watermark;
386 if (aux_head - aux_tail < perf_aux_size(rb))
387 handle->size = CIRC_SPACE(aux_head, aux_tail, perf_aux_size(rb));
390 * handle->size computation depends on aux_tail load; this forms a
391 * control dependency barrier separating aux_tail load from aux data
392 * store that will be enabled on successful return
394 if (!handle->size) { /* A, matches D */
395 event->pending_disable = 1;
396 perf_output_wakeup(handle);
397 local_set(&rb->aux_nest, 0);
398 goto err_put;
402 return handle->rb->aux_priv;
404 err_put:
405 /* can't be last */
406 rb_free_aux(rb);
408 err:
409 ring_buffer_put(rb);
410 handle->event = NULL;
412 return NULL;
414 EXPORT_SYMBOL_GPL(perf_aux_output_begin);
416 static bool __always_inline rb_need_aux_wakeup(struct ring_buffer *rb)
418 if (rb->aux_overwrite)
419 return false;
421 if (rb->aux_head - rb->aux_wakeup >= rb->aux_watermark) {
422 rb->aux_wakeup = rounddown(rb->aux_head, rb->aux_watermark);
423 return true;
426 return false;
430 * Commit the data written by hardware into the ring buffer by adjusting
431 * aux_head and posting a PERF_RECORD_AUX into the perf buffer. It is the
432 * pmu driver's responsibility to observe ordering rules of the hardware,
433 * so that all the data is externally visible before this is called.
435 * Note: this has to be called from pmu::stop() callback, as the assumption
436 * of the AUX buffer management code is that after pmu::stop(), the AUX
437 * transaction must be stopped and therefore drop the AUX reference count.
439 void perf_aux_output_end(struct perf_output_handle *handle, unsigned long size)
441 bool wakeup = !!(handle->aux_flags & PERF_AUX_FLAG_TRUNCATED);
442 struct ring_buffer *rb = handle->rb;
443 unsigned long aux_head;
445 /* in overwrite mode, driver provides aux_head via handle */
446 if (rb->aux_overwrite) {
447 handle->aux_flags |= PERF_AUX_FLAG_OVERWRITE;
449 aux_head = handle->head;
450 rb->aux_head = aux_head;
451 } else {
452 handle->aux_flags &= ~PERF_AUX_FLAG_OVERWRITE;
454 aux_head = rb->aux_head;
455 rb->aux_head += size;
458 if (size || handle->aux_flags) {
460 * Only send RECORD_AUX if we have something useful to communicate
463 perf_event_aux_event(handle->event, aux_head, size,
464 handle->aux_flags);
467 rb->user_page->aux_head = rb->aux_head;
468 if (rb_need_aux_wakeup(rb))
469 wakeup = true;
471 if (wakeup) {
472 if (handle->aux_flags & PERF_AUX_FLAG_TRUNCATED)
473 handle->event->pending_disable = 1;
474 perf_output_wakeup(handle);
477 handle->event = NULL;
479 local_set(&rb->aux_nest, 0);
480 /* can't be last */
481 rb_free_aux(rb);
482 ring_buffer_put(rb);
484 EXPORT_SYMBOL_GPL(perf_aux_output_end);
487 * Skip over a given number of bytes in the AUX buffer, due to, for example,
488 * hardware's alignment constraints.
490 int perf_aux_output_skip(struct perf_output_handle *handle, unsigned long size)
492 struct ring_buffer *rb = handle->rb;
494 if (size > handle->size)
495 return -ENOSPC;
497 rb->aux_head += size;
499 rb->user_page->aux_head = rb->aux_head;
500 if (rb_need_aux_wakeup(rb)) {
501 perf_output_wakeup(handle);
502 handle->wakeup = rb->aux_wakeup + rb->aux_watermark;
505 handle->head = rb->aux_head;
506 handle->size -= size;
508 return 0;
510 EXPORT_SYMBOL_GPL(perf_aux_output_skip);
512 void *perf_get_aux(struct perf_output_handle *handle)
514 /* this is only valid between perf_aux_output_begin and *_end */
515 if (!handle->event)
516 return NULL;
518 return handle->rb->aux_priv;
520 EXPORT_SYMBOL_GPL(perf_get_aux);
522 #define PERF_AUX_GFP (GFP_KERNEL | __GFP_ZERO | __GFP_NOWARN | __GFP_NORETRY)
524 static struct page *rb_alloc_aux_page(int node, int order)
526 struct page *page;
528 if (order > MAX_ORDER)
529 order = MAX_ORDER;
531 do {
532 page = alloc_pages_node(node, PERF_AUX_GFP, order);
533 } while (!page && order--);
535 if (page && order) {
537 * Communicate the allocation size to the driver:
538 * if we managed to secure a high-order allocation,
539 * set its first page's private to this order;
540 * !PagePrivate(page) means it's just a normal page.
542 split_page(page, order);
543 SetPagePrivate(page);
544 set_page_private(page, order);
547 return page;
550 static void rb_free_aux_page(struct ring_buffer *rb, int idx)
552 struct page *page = virt_to_page(rb->aux_pages[idx]);
554 ClearPagePrivate(page);
555 page->mapping = NULL;
556 __free_page(page);
559 static void __rb_free_aux(struct ring_buffer *rb)
561 int pg;
564 * Should never happen, the last reference should be dropped from
565 * perf_mmap_close() path, which first stops aux transactions (which
566 * in turn are the atomic holders of aux_refcount) and then does the
567 * last rb_free_aux().
569 WARN_ON_ONCE(in_atomic());
571 if (rb->aux_priv) {
572 rb->free_aux(rb->aux_priv);
573 rb->free_aux = NULL;
574 rb->aux_priv = NULL;
577 if (rb->aux_nr_pages) {
578 for (pg = 0; pg < rb->aux_nr_pages; pg++)
579 rb_free_aux_page(rb, pg);
581 kfree(rb->aux_pages);
582 rb->aux_nr_pages = 0;
586 int rb_alloc_aux(struct ring_buffer *rb, struct perf_event *event,
587 pgoff_t pgoff, int nr_pages, long watermark, int flags)
589 bool overwrite = !(flags & RING_BUFFER_WRITABLE);
590 int node = (event->cpu == -1) ? -1 : cpu_to_node(event->cpu);
591 int ret = -ENOMEM, max_order = 0;
593 if (!has_aux(event))
594 return -EOPNOTSUPP;
596 if (event->pmu->capabilities & PERF_PMU_CAP_AUX_NO_SG) {
598 * We need to start with the max_order that fits in nr_pages,
599 * not the other way around, hence ilog2() and not get_order.
601 max_order = ilog2(nr_pages);
604 * PMU requests more than one contiguous chunks of memory
605 * for SW double buffering
607 if ((event->pmu->capabilities & PERF_PMU_CAP_AUX_SW_DOUBLEBUF) &&
608 !overwrite) {
609 if (!max_order)
610 return -EINVAL;
612 max_order--;
616 rb->aux_pages = kzalloc_node(nr_pages * sizeof(void *), GFP_KERNEL, node);
617 if (!rb->aux_pages)
618 return -ENOMEM;
620 rb->free_aux = event->pmu->free_aux;
621 for (rb->aux_nr_pages = 0; rb->aux_nr_pages < nr_pages;) {
622 struct page *page;
623 int last, order;
625 order = min(max_order, ilog2(nr_pages - rb->aux_nr_pages));
626 page = rb_alloc_aux_page(node, order);
627 if (!page)
628 goto out;
630 for (last = rb->aux_nr_pages + (1 << page_private(page));
631 last > rb->aux_nr_pages; rb->aux_nr_pages++)
632 rb->aux_pages[rb->aux_nr_pages] = page_address(page++);
636 * In overwrite mode, PMUs that don't support SG may not handle more
637 * than one contiguous allocation, since they rely on PMI to do double
638 * buffering. In this case, the entire buffer has to be one contiguous
639 * chunk.
641 if ((event->pmu->capabilities & PERF_PMU_CAP_AUX_NO_SG) &&
642 overwrite) {
643 struct page *page = virt_to_page(rb->aux_pages[0]);
645 if (page_private(page) != max_order)
646 goto out;
649 rb->aux_priv = event->pmu->setup_aux(event->cpu, rb->aux_pages, nr_pages,
650 overwrite);
651 if (!rb->aux_priv)
652 goto out;
654 ret = 0;
657 * aux_pages (and pmu driver's private data, aux_priv) will be
658 * referenced in both producer's and consumer's contexts, thus
659 * we keep a refcount here to make sure either of the two can
660 * reference them safely.
662 atomic_set(&rb->aux_refcount, 1);
664 rb->aux_overwrite = overwrite;
665 rb->aux_watermark = watermark;
667 if (!rb->aux_watermark && !rb->aux_overwrite)
668 rb->aux_watermark = nr_pages << (PAGE_SHIFT - 1);
670 out:
671 if (!ret)
672 rb->aux_pgoff = pgoff;
673 else
674 __rb_free_aux(rb);
676 return ret;
679 void rb_free_aux(struct ring_buffer *rb)
681 if (atomic_dec_and_test(&rb->aux_refcount))
682 __rb_free_aux(rb);
685 #ifndef CONFIG_PERF_USE_VMALLOC
688 * Back perf_mmap() with regular GFP_KERNEL-0 pages.
691 static struct page *
692 __perf_mmap_to_page(struct ring_buffer *rb, unsigned long pgoff)
694 if (pgoff > rb->nr_pages)
695 return NULL;
697 if (pgoff == 0)
698 return virt_to_page(rb->user_page);
700 return virt_to_page(rb->data_pages[pgoff - 1]);
703 static void *perf_mmap_alloc_page(int cpu)
705 struct page *page;
706 int node;
708 node = (cpu == -1) ? cpu : cpu_to_node(cpu);
709 page = alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0);
710 if (!page)
711 return NULL;
713 return page_address(page);
716 struct ring_buffer *rb_alloc(int nr_pages, long watermark, int cpu, int flags)
718 struct ring_buffer *rb;
719 unsigned long size;
720 int i;
722 size = sizeof(struct ring_buffer);
723 size += nr_pages * sizeof(void *);
725 rb = kzalloc(size, GFP_KERNEL);
726 if (!rb)
727 goto fail;
729 rb->user_page = perf_mmap_alloc_page(cpu);
730 if (!rb->user_page)
731 goto fail_user_page;
733 for (i = 0; i < nr_pages; i++) {
734 rb->data_pages[i] = perf_mmap_alloc_page(cpu);
735 if (!rb->data_pages[i])
736 goto fail_data_pages;
739 rb->nr_pages = nr_pages;
741 ring_buffer_init(rb, watermark, flags);
743 return rb;
745 fail_data_pages:
746 for (i--; i >= 0; i--)
747 free_page((unsigned long)rb->data_pages[i]);
749 free_page((unsigned long)rb->user_page);
751 fail_user_page:
752 kfree(rb);
754 fail:
755 return NULL;
758 static void perf_mmap_free_page(unsigned long addr)
760 struct page *page = virt_to_page((void *)addr);
762 page->mapping = NULL;
763 __free_page(page);
766 void rb_free(struct ring_buffer *rb)
768 int i;
770 perf_mmap_free_page((unsigned long)rb->user_page);
771 for (i = 0; i < rb->nr_pages; i++)
772 perf_mmap_free_page((unsigned long)rb->data_pages[i]);
773 kfree(rb);
776 #else
777 static int data_page_nr(struct ring_buffer *rb)
779 return rb->nr_pages << page_order(rb);
782 static struct page *
783 __perf_mmap_to_page(struct ring_buffer *rb, unsigned long pgoff)
785 /* The '>' counts in the user page. */
786 if (pgoff > data_page_nr(rb))
787 return NULL;
789 return vmalloc_to_page((void *)rb->user_page + pgoff * PAGE_SIZE);
792 static void perf_mmap_unmark_page(void *addr)
794 struct page *page = vmalloc_to_page(addr);
796 page->mapping = NULL;
799 static void rb_free_work(struct work_struct *work)
801 struct ring_buffer *rb;
802 void *base;
803 int i, nr;
805 rb = container_of(work, struct ring_buffer, work);
806 nr = data_page_nr(rb);
808 base = rb->user_page;
809 /* The '<=' counts in the user page. */
810 for (i = 0; i <= nr; i++)
811 perf_mmap_unmark_page(base + (i * PAGE_SIZE));
813 vfree(base);
814 kfree(rb);
817 void rb_free(struct ring_buffer *rb)
819 schedule_work(&rb->work);
822 struct ring_buffer *rb_alloc(int nr_pages, long watermark, int cpu, int flags)
824 struct ring_buffer *rb;
825 unsigned long size;
826 void *all_buf;
828 size = sizeof(struct ring_buffer);
829 size += sizeof(void *);
831 rb = kzalloc(size, GFP_KERNEL);
832 if (!rb)
833 goto fail;
835 INIT_WORK(&rb->work, rb_free_work);
837 all_buf = vmalloc_user((nr_pages + 1) * PAGE_SIZE);
838 if (!all_buf)
839 goto fail_all_buf;
841 rb->user_page = all_buf;
842 rb->data_pages[0] = all_buf + PAGE_SIZE;
843 if (nr_pages) {
844 rb->nr_pages = 1;
845 rb->page_order = ilog2(nr_pages);
848 ring_buffer_init(rb, watermark, flags);
850 return rb;
852 fail_all_buf:
853 kfree(rb);
855 fail:
856 return NULL;
859 #endif
861 struct page *
862 perf_mmap_to_page(struct ring_buffer *rb, unsigned long pgoff)
864 if (rb->aux_nr_pages) {
865 /* above AUX space */
866 if (pgoff > rb->aux_pgoff + rb->aux_nr_pages)
867 return NULL;
869 /* AUX space */
870 if (pgoff >= rb->aux_pgoff)
871 return virt_to_page(rb->aux_pages[pgoff - rb->aux_pgoff]);
874 return __perf_mmap_to_page(rb, pgoff);