2 * ring_buffer_backend.c
4 * Copyright (C) 2005-2010 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
6 * Dual LGPL v2.1/GPL v2 license.
9 #include <linux/stddef.h>
10 #include <linux/module.h>
11 #include <linux/string.h>
12 #include <linux/bitops.h>
13 #include <linux/delay.h>
14 #include <linux/errno.h>
15 #include <linux/slab.h>
16 #include <linux/cpu.h>
19 #include "../../wrapper/vmalloc.h" /* for wrapper_vmalloc_sync_all() */
20 #include "../../wrapper/ringbuffer/config.h"
21 #include "../../wrapper/ringbuffer/backend.h"
22 #include "../../wrapper/ringbuffer/frontend.h"
25 * lib_ring_buffer_backend_allocate - allocate a channel buffer
26 * @config: ring buffer instance configuration
27 * @buf: the buffer struct
28 * @size: total size of the buffer
29 * @num_subbuf: number of subbuffers
30 * @extra_reader_sb: need extra subbuffer for reader
33 int lib_ring_buffer_backend_allocate(const struct lib_ring_buffer_config
*config
,
34 struct lib_ring_buffer_backend
*bufb
,
35 size_t size
, size_t num_subbuf
,
38 struct channel_backend
*chanb
= &bufb
->chan
->backend
;
39 unsigned long j
, num_pages
, num_pages_per_subbuf
, page_idx
= 0;
40 unsigned long subbuf_size
, mmap_offset
= 0;
41 unsigned long num_subbuf_alloc
;
46 num_pages
= size
>> PAGE_SHIFT
;
47 num_pages_per_subbuf
= num_pages
>> get_count_order(num_subbuf
);
48 subbuf_size
= chanb
->subbuf_size
;
49 num_subbuf_alloc
= num_subbuf
;
51 if (extra_reader_sb
) {
52 num_pages
+= num_pages_per_subbuf
; /* Add pages for reader */
56 pages
= kmalloc_node(ALIGN(sizeof(*pages
) * num_pages
,
57 1 << INTERNODE_CACHE_SHIFT
),
58 GFP_KERNEL
, cpu_to_node(max(bufb
->cpu
, 0)));
62 virt
= kmalloc_node(ALIGN(sizeof(*virt
) * num_pages
,
63 1 << INTERNODE_CACHE_SHIFT
),
64 GFP_KERNEL
, cpu_to_node(max(bufb
->cpu
, 0)));
68 bufb
->array
= kmalloc_node(ALIGN(sizeof(*bufb
->array
)
70 1 << INTERNODE_CACHE_SHIFT
),
71 GFP_KERNEL
, cpu_to_node(max(bufb
->cpu
, 0)));
72 if (unlikely(!bufb
->array
))
75 for (i
= 0; i
< num_pages
; i
++) {
76 pages
[i
] = alloc_pages_node(cpu_to_node(max(bufb
->cpu
, 0)),
77 GFP_KERNEL
| __GFP_ZERO
, 0);
78 if (unlikely(!pages
[i
]))
80 virt
[i
] = page_address(pages
[i
]);
82 bufb
->num_pages_per_subbuf
= num_pages_per_subbuf
;
84 /* Allocate backend pages array elements */
85 for (i
= 0; i
< num_subbuf_alloc
; i
++) {
88 sizeof(struct lib_ring_buffer_backend_pages
) +
89 sizeof(struct lib_ring_buffer_backend_page
)
90 * num_pages_per_subbuf
,
91 1 << INTERNODE_CACHE_SHIFT
),
92 GFP_KERNEL
, cpu_to_node(max(bufb
->cpu
, 0)));
97 /* Allocate write-side subbuffer table */
98 bufb
->buf_wsb
= kzalloc_node(ALIGN(
99 sizeof(struct lib_ring_buffer_backend_subbuffer
)
101 1 << INTERNODE_CACHE_SHIFT
),
102 GFP_KERNEL
, cpu_to_node(max(bufb
->cpu
, 0)));
103 if (unlikely(!bufb
->buf_wsb
))
106 for (i
= 0; i
< num_subbuf
; i
++)
107 bufb
->buf_wsb
[i
].id
= subbuffer_id(config
, 0, 1, i
);
109 /* Assign read-side subbuffer table */
111 bufb
->buf_rsb
.id
= subbuffer_id(config
, 0, 1,
112 num_subbuf_alloc
- 1);
114 bufb
->buf_rsb
.id
= subbuffer_id(config
, 0, 1, 0);
116 /* Assign pages to page index */
117 for (i
= 0; i
< num_subbuf_alloc
; i
++) {
118 for (j
= 0; j
< num_pages_per_subbuf
; j
++) {
119 CHAN_WARN_ON(chanb
, page_idx
> num_pages
);
120 bufb
->array
[i
]->p
[j
].virt
= virt
[page_idx
];
121 bufb
->array
[i
]->p
[j
].page
= pages
[page_idx
];
124 if (config
->output
== RING_BUFFER_MMAP
) {
125 bufb
->array
[i
]->mmap_offset
= mmap_offset
;
126 mmap_offset
+= subbuf_size
;
131 * If kmalloc ever uses vmalloc underneath, make sure the buffer pages
134 wrapper_vmalloc_sync_all();
140 for (i
= 0; (i
< num_subbuf_alloc
&& bufb
->array
[i
]); i
++)
141 kfree(bufb
->array
[i
]);
143 /* Free all allocated pages */
144 for (i
= 0; (i
< num_pages
&& pages
[i
]); i
++)
145 __free_page(pages
[i
]);
155 int lib_ring_buffer_backend_create(struct lib_ring_buffer_backend
*bufb
,
156 struct channel_backend
*chanb
, int cpu
)
158 const struct lib_ring_buffer_config
*config
= chanb
->config
;
160 bufb
->chan
= container_of(chanb
, struct channel
, backend
);
163 return lib_ring_buffer_backend_allocate(config
, bufb
, chanb
->buf_size
,
165 chanb
->extra_reader_sb
);
168 void lib_ring_buffer_backend_free(struct lib_ring_buffer_backend
*bufb
)
170 struct channel_backend
*chanb
= &bufb
->chan
->backend
;
171 unsigned long i
, j
, num_subbuf_alloc
;
173 num_subbuf_alloc
= chanb
->num_subbuf
;
174 if (chanb
->extra_reader_sb
)
177 kfree(bufb
->buf_wsb
);
178 for (i
= 0; i
< num_subbuf_alloc
; i
++) {
179 for (j
= 0; j
< bufb
->num_pages_per_subbuf
; j
++)
180 __free_page(bufb
->array
[i
]->p
[j
].page
);
181 kfree(bufb
->array
[i
]);
187 void lib_ring_buffer_backend_reset(struct lib_ring_buffer_backend
*bufb
)
189 struct channel_backend
*chanb
= &bufb
->chan
->backend
;
190 const struct lib_ring_buffer_config
*config
= chanb
->config
;
191 unsigned long num_subbuf_alloc
;
194 num_subbuf_alloc
= chanb
->num_subbuf
;
195 if (chanb
->extra_reader_sb
)
198 for (i
= 0; i
< chanb
->num_subbuf
; i
++)
199 bufb
->buf_wsb
[i
].id
= subbuffer_id(config
, 0, 1, i
);
200 if (chanb
->extra_reader_sb
)
201 bufb
->buf_rsb
.id
= subbuffer_id(config
, 0, 1,
202 num_subbuf_alloc
- 1);
204 bufb
->buf_rsb
.id
= subbuffer_id(config
, 0, 1, 0);
206 for (i
= 0; i
< num_subbuf_alloc
; i
++) {
207 /* Don't reset mmap_offset */
208 v_set(config
, &bufb
->array
[i
]->records_commit
, 0);
209 v_set(config
, &bufb
->array
[i
]->records_unread
, 0);
210 bufb
->array
[i
]->data_size
= 0;
211 /* Don't reset backend page and virt addresses */
213 /* Don't reset num_pages_per_subbuf, cpu, allocated */
214 v_set(config
, &bufb
->records_read
, 0);
218 * The frontend is responsible for also calling ring_buffer_backend_reset for
219 * each buffer when calling channel_backend_reset.
221 void channel_backend_reset(struct channel_backend
*chanb
)
223 struct channel
*chan
= container_of(chanb
, struct channel
, backend
);
224 const struct lib_ring_buffer_config
*config
= chanb
->config
;
227 * Don't reset buf_size, subbuf_size, subbuf_size_order,
228 * num_subbuf_order, buf_size_order, extra_reader_sb, num_subbuf,
229 * priv, notifiers, config, cpumask and name.
231 chanb
->start_tsc
= config
->cb
.ring_buffer_clock_read(chan
);
234 #ifdef CONFIG_HOTPLUG_CPU
236 * lib_ring_buffer_cpu_hp_callback - CPU hotplug callback
237 * @nb: notifier block
238 * @action: hotplug action to take
241 * Returns the success/failure of the operation. (%NOTIFY_OK, %NOTIFY_BAD)
244 int __cpuinit
lib_ring_buffer_cpu_hp_callback(struct notifier_block
*nb
,
245 unsigned long action
,
248 unsigned int cpu
= (unsigned long)hcpu
;
249 struct channel_backend
*chanb
= container_of(nb
, struct channel_backend
,
251 const struct lib_ring_buffer_config
*config
= chanb
->config
;
252 struct lib_ring_buffer
*buf
;
255 CHAN_WARN_ON(chanb
, config
->alloc
== RING_BUFFER_ALLOC_GLOBAL
);
259 case CPU_UP_PREPARE_FROZEN
:
260 buf
= per_cpu_ptr(chanb
->buf
, cpu
);
261 ret
= lib_ring_buffer_create(buf
, chanb
, cpu
);
264 "ring_buffer_cpu_hp_callback: cpu %d "
265 "buffer creation failed\n", cpu
);
270 case CPU_DEAD_FROZEN
:
271 /* No need to do a buffer switch here, because it will happen
272 * when tracing is stopped, or will be done by switch timer CPU
281 * channel_backend_init - initialize a channel backend
282 * @chanb: channel backend
283 * @name: channel name
284 * @config: client ring buffer configuration
285 * @priv: client private data
286 * @parent: dentry of parent directory, %NULL for root directory
287 * @subbuf_size: size of sub-buffers (> PAGE_SIZE, power of 2)
288 * @num_subbuf: number of sub-buffers (power of 2)
290 * Returns channel pointer if successful, %NULL otherwise.
292 * Creates per-cpu channel buffers using the sizes and attributes
293 * specified. The created channel buffer files will be named
294 * name_0...name_N-1. File permissions will be %S_IRUSR.
296 * Called with CPU hotplug disabled.
298 int channel_backend_init(struct channel_backend
*chanb
,
300 const struct lib_ring_buffer_config
*config
,
301 void *priv
, size_t subbuf_size
, size_t num_subbuf
)
303 struct channel
*chan
= container_of(chanb
, struct channel
, backend
);
310 if (!(subbuf_size
&& num_subbuf
))
313 /* Check that the subbuffer size is larger than a page. */
314 if (subbuf_size
< PAGE_SIZE
)
318 * Make sure the number of subbuffers and subbuffer size are power of 2.
320 CHAN_WARN_ON(chanb
, hweight32(subbuf_size
) != 1);
321 CHAN_WARN_ON(chanb
, hweight32(num_subbuf
) != 1);
323 ret
= subbuffer_id_check_index(config
, num_subbuf
);
328 chanb
->buf_size
= num_subbuf
* subbuf_size
;
329 chanb
->subbuf_size
= subbuf_size
;
330 chanb
->buf_size_order
= get_count_order(chanb
->buf_size
);
331 chanb
->subbuf_size_order
= get_count_order(subbuf_size
);
332 chanb
->num_subbuf_order
= get_count_order(num_subbuf
);
333 chanb
->extra_reader_sb
=
334 (config
->mode
== RING_BUFFER_OVERWRITE
) ? 1 : 0;
335 chanb
->num_subbuf
= num_subbuf
;
336 strlcpy(chanb
->name
, name
, NAME_MAX
);
337 chanb
->config
= config
;
339 if (config
->alloc
== RING_BUFFER_ALLOC_PER_CPU
) {
340 if (!zalloc_cpumask_var(&chanb
->cpumask
, GFP_KERNEL
))
344 if (config
->alloc
== RING_BUFFER_ALLOC_PER_CPU
) {
345 /* Allocating the buffer per-cpu structures */
346 chanb
->buf
= alloc_percpu(struct lib_ring_buffer
);
351 * In case of non-hotplug cpu, if the ring-buffer is allocated
352 * in early initcall, it will not be notified of secondary cpus.
353 * In that off case, we need to allocate for all possible cpus.
355 #ifdef CONFIG_HOTPLUG_CPU
357 * buf->backend.allocated test takes care of concurrent CPU
359 * Priority higher than frontend, so we create the ring buffer
360 * before we start the timer.
362 chanb
->cpu_hp_notifier
.notifier_call
=
363 lib_ring_buffer_cpu_hp_callback
;
364 chanb
->cpu_hp_notifier
.priority
= 5;
365 register_hotcpu_notifier(&chanb
->cpu_hp_notifier
);
368 for_each_online_cpu(i
) {
369 ret
= lib_ring_buffer_create(per_cpu_ptr(chanb
->buf
, i
),
372 goto free_bufs
; /* cpu hotplug locked */
376 for_each_possible_cpu(i
) {
377 ret
= lib_ring_buffer_create(per_cpu_ptr(chanb
->buf
, i
),
380 goto free_bufs
; /* cpu hotplug locked */
384 chanb
->buf
= kzalloc(sizeof(struct lib_ring_buffer
), GFP_KERNEL
);
387 ret
= lib_ring_buffer_create(chanb
->buf
, chanb
, -1);
391 chanb
->start_tsc
= config
->cb
.ring_buffer_clock_read(chan
);
396 if (config
->alloc
== RING_BUFFER_ALLOC_PER_CPU
) {
397 for_each_possible_cpu(i
) {
398 struct lib_ring_buffer
*buf
= per_cpu_ptr(chanb
->buf
, i
);
400 if (!buf
->backend
.allocated
)
402 lib_ring_buffer_free(buf
);
404 #ifdef CONFIG_HOTPLUG_CPU
407 free_percpu(chanb
->buf
);
411 if (config
->alloc
== RING_BUFFER_ALLOC_PER_CPU
)
412 free_cpumask_var(chanb
->cpumask
);
417 * channel_backend_unregister_notifiers - unregister notifiers
422 void channel_backend_unregister_notifiers(struct channel_backend
*chanb
)
424 const struct lib_ring_buffer_config
*config
= chanb
->config
;
426 if (config
->alloc
== RING_BUFFER_ALLOC_PER_CPU
)
427 unregister_hotcpu_notifier(&chanb
->cpu_hp_notifier
);
431 * channel_backend_free - destroy the channel
434 * Destroy all channel buffers and frees the channel.
436 void channel_backend_free(struct channel_backend
*chanb
)
438 const struct lib_ring_buffer_config
*config
= chanb
->config
;
441 if (config
->alloc
== RING_BUFFER_ALLOC_PER_CPU
) {
442 for_each_possible_cpu(i
) {
443 struct lib_ring_buffer
*buf
= per_cpu_ptr(chanb
->buf
, i
);
445 if (!buf
->backend
.allocated
)
447 lib_ring_buffer_free(buf
);
449 free_cpumask_var(chanb
->cpumask
);
450 free_percpu(chanb
->buf
);
452 struct lib_ring_buffer
*buf
= chanb
->buf
;
454 CHAN_WARN_ON(chanb
, !buf
->backend
.allocated
);
455 lib_ring_buffer_free(buf
);
461 * lib_ring_buffer_write - write data to a ring_buffer buffer.
462 * @bufb : buffer backend
463 * @offset : offset within the buffer
464 * @src : source address
465 * @len : length to write
466 * @pagecpy : page size copied so far
468 void _lib_ring_buffer_write(struct lib_ring_buffer_backend
*bufb
, size_t offset
,
469 const void *src
, size_t len
, ssize_t pagecpy
)
471 struct channel_backend
*chanb
= &bufb
->chan
->backend
;
472 const struct lib_ring_buffer_config
*config
= chanb
->config
;
474 struct lib_ring_buffer_backend_pages
*rpages
;
475 unsigned long sb_bindex
, id
;
481 sbidx
= offset
>> chanb
->subbuf_size_order
;
482 index
= (offset
& (chanb
->subbuf_size
- 1)) >> PAGE_SHIFT
;
485 * Underlying layer should never ask for writes across
488 CHAN_WARN_ON(chanb
, offset
>= chanb
->buf_size
);
490 pagecpy
= min_t(size_t, len
, PAGE_SIZE
- (offset
& ~PAGE_MASK
));
491 id
= bufb
->buf_wsb
[sbidx
].id
;
492 sb_bindex
= subbuffer_id_get_index(config
, id
);
493 rpages
= bufb
->array
[sb_bindex
];
494 CHAN_WARN_ON(chanb
, config
->mode
== RING_BUFFER_OVERWRITE
495 && subbuffer_id_is_noref(config
, id
));
496 lib_ring_buffer_do_copy(config
,
497 rpages
->p
[index
].virt
498 + (offset
& ~PAGE_MASK
),
500 } while (unlikely(len
!= pagecpy
));
502 EXPORT_SYMBOL_GPL(_lib_ring_buffer_write
);
505 * lib_ring_buffer_read - read data from ring_buffer_buffer.
506 * @bufb : buffer backend
507 * @offset : offset within the buffer
508 * @dest : destination address
509 * @len : length to copy to destination
511 * Should be protected by get_subbuf/put_subbuf.
512 * Returns the length copied.
514 size_t lib_ring_buffer_read(struct lib_ring_buffer_backend
*bufb
, size_t offset
,
515 void *dest
, size_t len
)
517 struct channel_backend
*chanb
= &bufb
->chan
->backend
;
518 const struct lib_ring_buffer_config
*config
= chanb
->config
;
520 ssize_t pagecpy
, orig_len
;
521 struct lib_ring_buffer_backend_pages
*rpages
;
522 unsigned long sb_bindex
, id
;
525 offset
&= chanb
->buf_size
- 1;
526 index
= (offset
& (chanb
->subbuf_size
- 1)) >> PAGE_SHIFT
;
530 pagecpy
= min_t(size_t, len
, PAGE_SIZE
- (offset
& ~PAGE_MASK
));
531 id
= bufb
->buf_rsb
.id
;
532 sb_bindex
= subbuffer_id_get_index(config
, id
);
533 rpages
= bufb
->array
[sb_bindex
];
534 CHAN_WARN_ON(chanb
, config
->mode
== RING_BUFFER_OVERWRITE
535 && subbuffer_id_is_noref(config
, id
));
536 memcpy(dest
, rpages
->p
[index
].virt
+ (offset
& ~PAGE_MASK
),
543 index
= (offset
& (chanb
->subbuf_size
- 1)) >> PAGE_SHIFT
;
545 * Underlying layer should never ask for reads across
548 CHAN_WARN_ON(chanb
, offset
>= chanb
->buf_size
);
552 EXPORT_SYMBOL_GPL(lib_ring_buffer_read
);
555 * __lib_ring_buffer_copy_to_user - read data from ring_buffer to userspace
556 * @bufb : buffer backend
557 * @offset : offset within the buffer
558 * @dest : destination userspace address
559 * @len : length to copy to destination
561 * Should be protected by get_subbuf/put_subbuf.
562 * access_ok() must have been performed on dest addresses prior to call this
564 * Returns -EFAULT on error, 0 if ok.
566 int __lib_ring_buffer_copy_to_user(struct lib_ring_buffer_backend
*bufb
,
567 size_t offset
, void __user
*dest
, size_t len
)
569 struct channel_backend
*chanb
= &bufb
->chan
->backend
;
570 const struct lib_ring_buffer_config
*config
= chanb
->config
;
573 struct lib_ring_buffer_backend_pages
*rpages
;
574 unsigned long sb_bindex
, id
;
576 offset
&= chanb
->buf_size
- 1;
577 index
= (offset
& (chanb
->subbuf_size
- 1)) >> PAGE_SHIFT
;
581 pagecpy
= min_t(size_t, len
, PAGE_SIZE
- (offset
& ~PAGE_MASK
));
582 id
= bufb
->buf_rsb
.id
;
583 sb_bindex
= subbuffer_id_get_index(config
, id
);
584 rpages
= bufb
->array
[sb_bindex
];
585 CHAN_WARN_ON(chanb
, config
->mode
== RING_BUFFER_OVERWRITE
586 && subbuffer_id_is_noref(config
, id
));
587 if (__copy_to_user(dest
,
588 rpages
->p
[index
].virt
+ (offset
& ~PAGE_MASK
),
596 index
= (offset
& (chanb
->subbuf_size
- 1)) >> PAGE_SHIFT
;
598 * Underlying layer should never ask for reads across
601 CHAN_WARN_ON(chanb
, offset
>= chanb
->buf_size
);
605 EXPORT_SYMBOL_GPL(__lib_ring_buffer_copy_to_user
);
608 * lib_ring_buffer_read_cstr - read a C-style string from ring_buffer.
609 * @bufb : buffer backend
610 * @offset : offset within the buffer
611 * @dest : destination address
612 * @len : destination's length
614 * return string's length
615 * Should be protected by get_subbuf/put_subbuf.
617 int lib_ring_buffer_read_cstr(struct lib_ring_buffer_backend
*bufb
, size_t offset
,
618 void *dest
, size_t len
)
620 struct channel_backend
*chanb
= &bufb
->chan
->backend
;
621 const struct lib_ring_buffer_config
*config
= chanb
->config
;
623 ssize_t pagecpy
, pagelen
, strpagelen
, orig_offset
;
625 struct lib_ring_buffer_backend_pages
*rpages
;
626 unsigned long sb_bindex
, id
;
628 offset
&= chanb
->buf_size
- 1;
629 index
= (offset
& (chanb
->subbuf_size
- 1)) >> PAGE_SHIFT
;
630 orig_offset
= offset
;
632 id
= bufb
->buf_rsb
.id
;
633 sb_bindex
= subbuffer_id_get_index(config
, id
);
634 rpages
= bufb
->array
[sb_bindex
];
635 CHAN_WARN_ON(chanb
, config
->mode
== RING_BUFFER_OVERWRITE
636 && subbuffer_id_is_noref(config
, id
));
637 str
= (char *)rpages
->p
[index
].virt
+ (offset
& ~PAGE_MASK
);
638 pagelen
= PAGE_SIZE
- (offset
& ~PAGE_MASK
);
639 strpagelen
= strnlen(str
, pagelen
);
641 pagecpy
= min_t(size_t, len
, strpagelen
);
643 memcpy(dest
, str
, pagecpy
);
648 offset
+= strpagelen
;
649 index
= (offset
& (chanb
->subbuf_size
- 1)) >> PAGE_SHIFT
;
650 if (strpagelen
< pagelen
)
653 * Underlying layer should never ask for reads across
656 CHAN_WARN_ON(chanb
, offset
>= chanb
->buf_size
);
659 ((char *)dest
)[0] = 0;
660 return offset
- orig_offset
;
662 EXPORT_SYMBOL_GPL(lib_ring_buffer_read_cstr
);
665 * lib_ring_buffer_read_get_page - Get a whole page to read from
666 * @bufb : buffer backend
667 * @offset : offset within the buffer
668 * @virt : pointer to page address (output)
670 * Should be protected by get_subbuf/put_subbuf.
671 * Returns the pointer to the page struct pointer.
673 struct page
**lib_ring_buffer_read_get_page(struct lib_ring_buffer_backend
*bufb
,
674 size_t offset
, void ***virt
)
677 struct lib_ring_buffer_backend_pages
*rpages
;
678 struct channel_backend
*chanb
= &bufb
->chan
->backend
;
679 const struct lib_ring_buffer_config
*config
= chanb
->config
;
680 unsigned long sb_bindex
, id
;
682 offset
&= chanb
->buf_size
- 1;
683 index
= (offset
& (chanb
->subbuf_size
- 1)) >> PAGE_SHIFT
;
684 id
= bufb
->buf_rsb
.id
;
685 sb_bindex
= subbuffer_id_get_index(config
, id
);
686 rpages
= bufb
->array
[sb_bindex
];
687 CHAN_WARN_ON(chanb
, config
->mode
== RING_BUFFER_OVERWRITE
688 && subbuffer_id_is_noref(config
, id
));
689 *virt
= &rpages
->p
[index
].virt
;
690 return &rpages
->p
[index
].page
;
692 EXPORT_SYMBOL_GPL(lib_ring_buffer_read_get_page
);
695 * lib_ring_buffer_read_offset_address - get address of a buffer location
696 * @bufb : buffer backend
697 * @offset : offset within the buffer.
699 * Return the address where a given offset is located (for read).
700 * Should be used to get the current subbuffer header pointer. Given we know
701 * it's never on a page boundary, it's safe to write directly to this address,
702 * as long as the write is never bigger than a page size.
704 void *lib_ring_buffer_read_offset_address(struct lib_ring_buffer_backend
*bufb
,
708 struct lib_ring_buffer_backend_pages
*rpages
;
709 struct channel_backend
*chanb
= &bufb
->chan
->backend
;
710 const struct lib_ring_buffer_config
*config
= chanb
->config
;
711 unsigned long sb_bindex
, id
;
713 offset
&= chanb
->buf_size
- 1;
714 index
= (offset
& (chanb
->subbuf_size
- 1)) >> PAGE_SHIFT
;
715 id
= bufb
->buf_rsb
.id
;
716 sb_bindex
= subbuffer_id_get_index(config
, id
);
717 rpages
= bufb
->array
[sb_bindex
];
718 CHAN_WARN_ON(chanb
, config
->mode
== RING_BUFFER_OVERWRITE
719 && subbuffer_id_is_noref(config
, id
));
720 return rpages
->p
[index
].virt
+ (offset
& ~PAGE_MASK
);
722 EXPORT_SYMBOL_GPL(lib_ring_buffer_read_offset_address
);
725 * lib_ring_buffer_offset_address - get address of a location within the buffer
726 * @bufb : buffer backend
727 * @offset : offset within the buffer.
729 * Return the address where a given offset is located.
730 * Should be used to get the current subbuffer header pointer. Given we know
731 * it's always at the beginning of a page, it's safe to write directly to this
732 * address, as long as the write is never bigger than a page size.
734 void *lib_ring_buffer_offset_address(struct lib_ring_buffer_backend
*bufb
,
738 struct lib_ring_buffer_backend_pages
*rpages
;
739 struct channel_backend
*chanb
= &bufb
->chan
->backend
;
740 const struct lib_ring_buffer_config
*config
= chanb
->config
;
741 unsigned long sb_bindex
, id
;
743 offset
&= chanb
->buf_size
- 1;
744 sbidx
= offset
>> chanb
->subbuf_size_order
;
745 index
= (offset
& (chanb
->subbuf_size
- 1)) >> PAGE_SHIFT
;
746 id
= bufb
->buf_wsb
[sbidx
].id
;
747 sb_bindex
= subbuffer_id_get_index(config
, id
);
748 rpages
= bufb
->array
[sb_bindex
];
749 CHAN_WARN_ON(chanb
, config
->mode
== RING_BUFFER_OVERWRITE
750 && subbuffer_id_is_noref(config
, id
));
751 return rpages
->p
[index
].virt
+ (offset
& ~PAGE_MASK
);
753 EXPORT_SYMBOL_GPL(lib_ring_buffer_offset_address
);