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Root/kernel/relay.c

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/module.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 int relay_buf_fault(struct vm_area_struct vma, struct vm_fault vmf)
43	{
44	struct page *page;
45	struct rchan_buf *buf = 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	if (is_vmalloc_addr(array))
85	vfree(array);
86	else
87	kfree(array);
88	}
89
90	/**
91	* relay_mmap_buf: - mmap channel buffer to process address space
92	* @buf: relay channel buffer
93	* @vma: vm_area_struct describing memory to be mapped
94	*
95	* Returns 0 if ok, negative on error
96	*
97	* Caller should already have grabbed mmap_sem.
98	*/
99	static int relay_mmap_buf(struct rchan_buf buf, struct vm_area_struct vma)
100	{
101	unsigned long length = vma->vm_end - vma->vm_start;
102	struct file *filp = vma->vm_file;
103
104	if (!buf)
105	return -EBADF;
106
107	if (length != (unsigned long)buf->chan->alloc_size)
108	return -EINVAL;
109
110	vma->vm_ops = &relay_file_mmap_ops;
111	vma->vm_flags \|= VM_DONTEXPAND;
112	vma->vm_private_data = buf;
113	buf->chan->cb->buf_mapped(buf, filp);
114
115	return 0;
116	}
117
118	/**
119	* relay_alloc_buf - allocate a channel buffer
120	* @buf: the buffer struct
121	* @size: total size of the buffer
122	*
123	* Returns a pointer to the resulting buffer, %NULL if unsuccessful. The
124	* passed in size will get page aligned, if it isn't already.
125	*/
126	static void relay_alloc_buf(struct rchan_buf buf, size_t *size)
127	{
128	void *mem;
129	unsigned int i, j, n_pages;
130
131	size = PAGE_ALIGN(size);
132	n_pages = *size >> PAGE_SHIFT;
133
134	buf->page_array = relay_alloc_page_array(n_pages);
135	if (!buf->page_array)
136	return NULL;
137
138	for (i = 0; i < n_pages; i++) {
139	buf->page_array[i] = alloc_page(GFP_KERNEL);
140	if (unlikely(!buf->page_array[i]))
141	goto depopulate;
142	set_page_private(buf->page_array[i], (unsigned long)buf);
143	}
144	mem = vmap(buf->page_array, n_pages, VM_MAP, PAGE_KERNEL);
145	if (!mem)
146	goto depopulate;
147
148	memset(mem, 0, *size);
149	buf->page_count = n_pages;
150	return mem;
151
152	depopulate:
153	for (j = 0; j < i; j++)
154	__free_page(buf->page_array[j]);
155	relay_free_page_array(buf->page_array);
156	return NULL;
157	}
158
159	/**
160	* relay_create_buf - allocate and initialize a channel buffer
161	* @chan: the relay channel
162	*
163	* Returns channel buffer if successful, %NULL otherwise.
164	*/
165	static struct rchan_buf relay_create_buf(struct rchan chan)
166	{
167	struct rchan_buf *buf = kzalloc(sizeof(struct rchan_buf), GFP_KERNEL);
168	if (!buf)
169	return NULL;
170
171	buf->padding = kmalloc(chan->n_subbufs * sizeof(size_t *), GFP_KERNEL);
172	if (!buf->padding)
173	goto free_buf;
174
175	buf->start = relay_alloc_buf(buf, &chan->alloc_size);
176	if (!buf->start)
177	goto free_buf;
178
179	buf->chan = chan;
180	kref_get(&buf->chan->kref);
181	return buf;
182
183	free_buf:
184	kfree(buf->padding);
185	kfree(buf);
186	return NULL;
187	}
188
189	/**
190	* relay_destroy_channel - free the channel struct
191	* @kref: target kernel reference that contains the relay channel
192	*
193	* Should only be called from kref_put().
194	*/
195	static void relay_destroy_channel(struct kref *kref)
196	{
197	struct rchan *chan = container_of(kref, struct rchan, kref);
198	kfree(chan);
199	}
200
201	/**
202	* relay_destroy_buf - destroy an rchan_buf struct and associated buffer
203	* @buf: the buffer struct
204	*/
205	static void relay_destroy_buf(struct rchan_buf *buf)
206	{
207	struct rchan *chan = buf->chan;
208	unsigned int i;
209
210	if (likely(buf->start)) {
211	vunmap(buf->start);
212	for (i = 0; i < buf->page_count; i++)
213	__free_page(buf->page_array[i]);
214	relay_free_page_array(buf->page_array);
215	}
216	chan->buf[buf->cpu] = NULL;
217	kfree(buf->padding);
218	kfree(buf);
219	kref_put(&chan->kref, relay_destroy_channel);
220	}
221
222	/**
223	* relay_remove_buf - remove a channel buffer
224	* @kref: target kernel reference that contains the relay buffer
225	*
226	* Removes the file from the fileystem, which also frees the
227	* rchan_buf_struct and the channel buffer. Should only be called from
228	* kref_put().
229	*/
230	static void relay_remove_buf(struct kref *kref)
231	{
232	struct rchan_buf *buf = container_of(kref, struct rchan_buf, kref);
233	buf->chan->cb->remove_buf_file(buf->dentry);
234	relay_destroy_buf(buf);
235	}
236
237	/**
238	* relay_buf_empty - boolean, is the channel buffer empty?
239	* @buf: channel buffer
240	*
241	* Returns 1 if the buffer is empty, 0 otherwise.
242	*/
243	static int relay_buf_empty(struct rchan_buf *buf)
244	{
245	return (buf->subbufs_produced - buf->subbufs_consumed) ? 0 : 1;
246	}
247
248	/**
249	* relay_buf_full - boolean, is the channel buffer full?
250	* @buf: channel buffer
251	*
252	* Returns 1 if the buffer is full, 0 otherwise.
253	*/
254	int relay_buf_full(struct rchan_buf *buf)
255	{
256	size_t ready = buf->subbufs_produced - buf->subbufs_consumed;
257	return (ready >= buf->chan->n_subbufs) ? 1 : 0;
258	}
259	EXPORT_SYMBOL_GPL(relay_buf_full);
260
261	/*
262	* High-level relay kernel API and associated functions.
263	*/
264
265	/*
266	* rchan_callback implementations defining default channel behavior. Used
267	* in place of corresponding NULL values in client callback struct.
268	*/
269
270	/*
271	* subbuf_start() default callback. Does nothing.
272	*/
273	static int subbuf_start_default_callback (struct rchan_buf *buf,
274	void *subbuf,
275	void *prev_subbuf,
276	size_t prev_padding)
277	{
278	if (relay_buf_full(buf))
279	return 0;
280
281	return 1;
282	}
283
284	/*
285	* buf_mapped() default callback. Does nothing.
286	*/
287	static void buf_mapped_default_callback(struct rchan_buf *buf,
288	struct file *filp)
289	{
290	}
291
292	/*
293	* buf_unmapped() default callback. Does nothing.
294	*/
295	static void buf_unmapped_default_callback(struct rchan_buf *buf,
296	struct file *filp)
297	{
298	}
299
300	/*
301	* create_buf_file_create() default callback. Does nothing.
302	*/
303	static struct dentry create_buf_file_default_callback(const char filename,
304	struct dentry *parent,
305	int mode,
306	struct rchan_buf *buf,
307	int *is_global)
308	{
309	return NULL;
310	}
311
312	/*
313	* remove_buf_file() default callback. Does nothing.
314	*/
315	static int remove_buf_file_default_callback(struct dentry *dentry)
316	{
317	return -EINVAL;
318	}
319
320	/* relay channel default callbacks */
321	static struct rchan_callbacks default_channel_callbacks = {
322	.subbuf_start = subbuf_start_default_callback,
323	.buf_mapped = buf_mapped_default_callback,
324	.buf_unmapped = buf_unmapped_default_callback,
325	.create_buf_file = create_buf_file_default_callback,
326	.remove_buf_file = remove_buf_file_default_callback,
327	};
328
329	/**
330	* wakeup_readers - wake up readers waiting on a channel
331	* @data: contains the channel buffer
332	*
333	* This is the timer function used to defer reader waking.
334	*/
335	static void wakeup_readers(unsigned long data)
336	{
337	struct rchan_buf buf = (struct rchan_buf )data;
338	wake_up_interruptible(&buf->read_wait);
339	}
340
341	/**
342	* __relay_reset - reset a channel buffer
343	* @buf: the channel buffer
344	* @init: 1 if this is a first-time initialization
345	*
346	* See relay_reset() for description of effect.
347	*/
348	static void __relay_reset(struct rchan_buf *buf, unsigned int init)
349	{
350	size_t i;
351
352	if (init) {
353	init_waitqueue_head(&buf->read_wait);
354	kref_init(&buf->kref);
355	setup_timer(&buf->timer, wakeup_readers, (unsigned long)buf);
356	} else
357	del_timer_sync(&buf->timer);
358
359	buf->subbufs_produced = 0;
360	buf->subbufs_consumed = 0;
361	buf->bytes_consumed = 0;
362	buf->finalized = 0;
363	buf->data = buf->start;
364	buf->offset = 0;
365
366	for (i = 0; i < buf->chan->n_subbufs; i++)
367	buf->padding[i] = 0;
368
369	buf->chan->cb->subbuf_start(buf, buf->data, NULL, 0);
370	}
371
372	/**
373	* relay_reset - reset the channel
374	* @chan: the channel
375	*
376	* This has the effect of erasing all data from all channel buffers
377	* and restarting the channel in its initial state. The buffers
378	* are not freed, so any mappings are still in effect.
379	*
380	* NOTE. Care should be taken that the channel isn't actually
381	* being used by anything when this call is made.
382	*/
383	void relay_reset(struct rchan *chan)
384	{
385	unsigned int i;
386
387	if (!chan)
388	return;
389
390	if (chan->is_global && chan->buf[0]) {
391	__relay_reset(chan->buf[0], 0);
392	return;
393	}
394
395	mutex_lock(&relay_channels_mutex);
396	for_each_possible_cpu(i)
397	if (chan->buf[i])
398	__relay_reset(chan->buf[i], 0);
399	mutex_unlock(&relay_channels_mutex);
400	}
401	EXPORT_SYMBOL_GPL(relay_reset);
402
403	static inline void relay_set_buf_dentry(struct rchan_buf *buf,
404	struct dentry *dentry)
405	{
406	buf->dentry = dentry;
407	buf->dentry->d_inode->i_size = buf->early_bytes;
408	}
409
410	static struct dentry relay_create_buf_file(struct rchan chan,
411	struct rchan_buf *buf,
412	unsigned int cpu)
413	{
414	struct dentry *dentry;
415	char *tmpname;
416
417	tmpname = kzalloc(NAME_MAX + 1, GFP_KERNEL);
418	if (!tmpname)
419	return NULL;
420	snprintf(tmpname, NAME_MAX, "%s%d", chan->base_filename, cpu);
421
422	/* Create file in fs */
423	dentry = chan->cb->create_buf_file(tmpname, chan->parent,
424	S_IRUSR, buf,
425	&chan->is_global);
426
427	kfree(tmpname);
428
429	return dentry;
430	}
431
432	/*
433	* relay_open_buf - create a new relay channel buffer
434	*
435	* used by relay_open() and CPU hotplug.
436	*/
437	static struct rchan_buf relay_open_buf(struct rchan chan, unsigned int cpu)
438	{
439	struct rchan_buf *buf = NULL;
440	struct dentry *dentry;
441
442	if (chan->is_global)
443	return chan->buf[0];
444
445	buf = relay_create_buf(chan);
446	if (!buf)
447	return NULL;
448
449	if (chan->has_base_filename) {
450	dentry = relay_create_buf_file(chan, buf, cpu);
451	if (!dentry)
452	goto free_buf;
453	relay_set_buf_dentry(buf, dentry);
454	}
455
456	buf->cpu = cpu;
457	__relay_reset(buf, 1);
458
459	if(chan->is_global) {
460	chan->buf[0] = buf;
461	buf->cpu = 0;
462	}
463
464	return buf;
465
466	free_buf:
467	relay_destroy_buf(buf);
468	return NULL;
469	}
470
471	/**
472	* relay_close_buf - close a channel buffer
473	* @buf: channel buffer
474	*
475	* Marks the buffer finalized and restores the default callbacks.
476	* The channel buffer and channel buffer data structure are then freed
477	* automatically when the last reference is given up.
478	*/
479	static void relay_close_buf(struct rchan_buf *buf)
480	{
481	buf->finalized = 1;
482	del_timer_sync(&buf->timer);
483	kref_put(&buf->kref, relay_remove_buf);
484	}
485
486	static void setup_callbacks(struct rchan *chan,
487	struct rchan_callbacks *cb)
488	{
489	if (!cb) {
490	chan->cb = &default_channel_callbacks;
491	return;
492	}
493
494	if (!cb->subbuf_start)
495	cb->subbuf_start = subbuf_start_default_callback;
496	if (!cb->buf_mapped)
497	cb->buf_mapped = buf_mapped_default_callback;
498	if (!cb->buf_unmapped)
499	cb->buf_unmapped = buf_unmapped_default_callback;
500	if (!cb->create_buf_file)
501	cb->create_buf_file = create_buf_file_default_callback;
502	if (!cb->remove_buf_file)
503	cb->remove_buf_file = remove_buf_file_default_callback;
504	chan->cb = cb;
505	}
506
507	/**
508	* relay_hotcpu_callback - CPU hotplug callback
509	* @nb: notifier block
510	* @action: hotplug action to take
511	* @hcpu: CPU number
512	*
513	* Returns the success/failure of the operation. (%NOTIFY_OK, %NOTIFY_BAD)
514	*/
515	static int __cpuinit relay_hotcpu_callback(struct notifier_block *nb,
516	unsigned long action,
517	void *hcpu)
518	{
519	unsigned int hotcpu = (unsigned long)hcpu;
520	struct rchan *chan;
521
522	switch(action) {
523	case CPU_UP_PREPARE:
524	case CPU_UP_PREPARE_FROZEN:
525	mutex_lock(&relay_channels_mutex);
526	list_for_each_entry(chan, &relay_channels, list) {
527	if (chan->buf[hotcpu])
528	continue;
529	chan->buf[hotcpu] = relay_open_buf(chan, hotcpu);
530	if(!chan->buf[hotcpu]) {
531	printk(KERN_ERR
532	"relay_hotcpu_callback: cpu %d buffer "
533	"creation failed\n", hotcpu);
534	mutex_unlock(&relay_channels_mutex);
535	return notifier_from_errno(-ENOMEM);
536	}
537	}
538	mutex_unlock(&relay_channels_mutex);
539	break;
540	case CPU_DEAD:
541	case CPU_DEAD_FROZEN:
542	/* No need to flush the cpu : will be flushed upon
543	* final relay_flush() call. */
544	break;
545	}
546	return NOTIFY_OK;
547	}
548
549	/**
550	* relay_open - create a new relay channel
551	* @base_filename: base name of files to create, %NULL for buffering only
552	* @parent: dentry of parent directory, %NULL for root directory or buffer
553	* @subbuf_size: size of sub-buffers
554	* @n_subbufs: number of sub-buffers
555	* @cb: client callback functions
556	* @private_data: user-defined data
557	*
558	* Returns channel pointer if successful, %NULL otherwise.
559	*
560	* Creates a channel buffer for each cpu using the sizes and
561	* attributes specified. The created channel buffer files
562	* will be named base_filename0...base_filenameN-1. File
563	* permissions will be %S_IRUSR.
564	*/
565	struct rchan relay_open(const char base_filename,
566	struct dentry *parent,
567	size_t subbuf_size,
568	size_t n_subbufs,
569	struct rchan_callbacks *cb,
570	void *private_data)
571	{
572	unsigned int i;
573	struct rchan *chan;
574
575	if (!(subbuf_size && n_subbufs))
576	return NULL;
577
578	chan = kzalloc(sizeof(struct rchan), GFP_KERNEL);
579	if (!chan)
580	return NULL;
581
582	chan->version = RELAYFS_CHANNEL_VERSION;
583	chan->n_subbufs = n_subbufs;
584	chan->subbuf_size = subbuf_size;
585	chan->alloc_size = FIX_SIZE(subbuf_size * n_subbufs);
586	chan->parent = parent;
587	chan->private_data = private_data;
588	if (base_filename) {
589	chan->has_base_filename = 1;
590	strlcpy(chan->base_filename, base_filename, NAME_MAX);
591	}
592	setup_callbacks(chan, cb);
593	kref_init(&chan->kref);
594
595	mutex_lock(&relay_channels_mutex);
596	for_each_online_cpu(i) {
597	chan->buf[i] = relay_open_buf(chan, i);
598	if (!chan->buf[i])
599	goto free_bufs;
600	}
601	list_add(&chan->list, &relay_channels);
602	mutex_unlock(&relay_channels_mutex);
603
604	return chan;
605
606	free_bufs:
607	for_each_possible_cpu(i) {
608	if (chan->buf[i])
609	relay_close_buf(chan->buf[i]);
610	}
611
612	kref_put(&chan->kref, relay_destroy_channel);
613	mutex_unlock(&relay_channels_mutex);
614	return NULL;
615	}
616	EXPORT_SYMBOL_GPL(relay_open);
617
618	struct rchan_percpu_buf_dispatcher {
619	struct rchan_buf *buf;
620	struct dentry *dentry;
621	};
622
623	/* Called in atomic context. */
624	static void __relay_set_buf_dentry(void *info)
625	{
626	struct rchan_percpu_buf_dispatcher *p = info;
627
628	relay_set_buf_dentry(p->buf, p->dentry);
629	}
630
631	/**
632	* relay_late_setup_files - triggers file creation
633	* @chan: channel to operate on
634	* @base_filename: base name of files to create
635	* @parent: dentry of parent directory, %NULL for root directory
636	*
637	* Returns 0 if successful, non-zero otherwise.
638	*
639	* Use to setup files for a previously buffer-only channel.
640	* Useful to do early tracing in kernel, before VFS is up, for example.
641	*/
642	int relay_late_setup_files(struct rchan *chan,
643	const char *base_filename,
644	struct dentry *parent)
645	{
646	int err = 0;
647	unsigned int i, curr_cpu;
648	unsigned long flags;
649	struct dentry *dentry;
650	struct rchan_percpu_buf_dispatcher disp;
651
652	if (!chan \|\| !base_filename)
653	return -EINVAL;
654
655	strlcpy(chan->base_filename, base_filename, NAME_MAX);
656
657	mutex_lock(&relay_channels_mutex);
658	/* Is chan already set up? */
659	if (unlikely(chan->has_base_filename)) {
660	mutex_unlock(&relay_channels_mutex);
661	return -EEXIST;
662	}
663	chan->has_base_filename = 1;
664	chan->parent = parent;
665	curr_cpu = get_cpu();
666	/*
667	* The CPU hotplug notifier ran before us and created buffers with
668	* no files associated. So it's safe to call relay_setup_buf_file()
669	* on all currently online CPUs.
670	*/
671	for_each_online_cpu(i) {
672	if (unlikely(!chan->buf[i])) {
673	WARN_ONCE(1, KERN_ERR "CPU has no buffer!\n");
674	err = -EINVAL;
675	break;
676	}
677
678	dentry = relay_create_buf_file(chan, chan->buf[i], i);
679	if (unlikely(!dentry)) {
680	err = -EINVAL;
681	break;
682	}
683
684	if (curr_cpu == i) {
685	local_irq_save(flags);
686	relay_set_buf_dentry(chan->buf[i], dentry);
687	local_irq_restore(flags);
688	} else {
689	disp.buf = chan->buf[i];
690	disp.dentry = dentry;
691	smp_mb();
692	/* relay_channels_mutex must be held, so wait. */
693	err = smp_call_function_single(i,
694	__relay_set_buf_dentry,
695	&disp, 1);
696	}
697	if (unlikely(err))
698	break;
699	}
700	put_cpu();
701	mutex_unlock(&relay_channels_mutex);
702
703	return err;
704	}
705
706	/**
707	* relay_switch_subbuf - switch to a new sub-buffer
708	* @buf: channel buffer
709	* @length: size of current event
710	*
711	* Returns either the length passed in or 0 if full.
712	*
713	* Performs sub-buffer-switch tasks such as invoking callbacks,
714	* updating padding counts, waking up readers, etc.
715	*/
716	size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length)
717	{
718	void old, new;
719	size_t old_subbuf, new_subbuf;
720
721	if (unlikely(length > buf->chan->subbuf_size))
722	goto toobig;
723
724	if (buf->offset != buf->chan->subbuf_size + 1) {
725	buf->prev_padding = buf->chan->subbuf_size - buf->offset;
726	old_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
727	buf->padding[old_subbuf] = buf->prev_padding;
728	buf->subbufs_produced++;
729	if (buf->dentry)
730	buf->dentry->d_inode->i_size +=
731	buf->chan->subbuf_size -
732	buf->padding[old_subbuf];
733	else
734	buf->early_bytes += buf->chan->subbuf_size -
735	buf->padding[old_subbuf];
736	smp_mb();
737	if (waitqueue_active(&buf->read_wait))
738	/*
739	* Calling wake_up_interruptible() from here
740	* will deadlock if we happen to be logging
741	* from the scheduler (trying to re-grab
742	* rq->lock), so defer it.
743	*/
744	mod_timer(&buf->timer, jiffies + 1);
745	}
746
747	old = buf->data;
748	new_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
749	new = buf->start + new_subbuf * buf->chan->subbuf_size;
750	buf->offset = 0;
751	if (!buf->chan->cb->subbuf_start(buf, new, old, buf->prev_padding)) {
752	buf->offset = buf->chan->subbuf_size + 1;
753	return 0;
754	}
755	buf->data = new;
756	buf->padding[new_subbuf] = 0;
757
758	if (unlikely(length + buf->offset > buf->chan->subbuf_size))
759	goto toobig;
760
761	return length;
762
763	toobig:
764	buf->chan->last_toobig = length;
765	return 0;
766	}
767	EXPORT_SYMBOL_GPL(relay_switch_subbuf);
768
769	/**
770	* relay_subbufs_consumed - update the buffer's sub-buffers-consumed count
771	* @chan: the channel
772	* @cpu: the cpu associated with the channel buffer to update
773	* @subbufs_consumed: number of sub-buffers to add to current buf's count
774	*
775	* Adds to the channel buffer's consumed sub-buffer count.
776	* subbufs_consumed should be the number of sub-buffers newly consumed,
777	* not the total consumed.
778	*
779	* NOTE. Kernel clients don't need to call this function if the channel
780	* mode is 'overwrite'.
781	*/
782	void relay_subbufs_consumed(struct rchan *chan,
783	unsigned int cpu,
784	size_t subbufs_consumed)
785	{
786	struct rchan_buf *buf;
787
788	if (!chan)
789	return;
790
791	if (cpu >= NR_CPUS \|\| !chan->buf[cpu] \|\|
792	subbufs_consumed > chan->n_subbufs)
793	return;
794
795	buf = chan->buf[cpu];
796	if (subbufs_consumed > buf->subbufs_produced - buf->subbufs_consumed)
797	buf->subbufs_consumed = buf->subbufs_produced;
798	else
799	buf->subbufs_consumed += subbufs_consumed;
800	}
801	EXPORT_SYMBOL_GPL(relay_subbufs_consumed);
802
803	/**
804	* relay_close - close the channel
805	* @chan: the channel
806	*
807	* Closes all channel buffers and frees the channel.
808	*/
809	void relay_close(struct rchan *chan)
810	{
811	unsigned int i;
812
813	if (!chan)
814	return;
815
816	mutex_lock(&relay_channels_mutex);
817	if (chan->is_global && chan->buf[0])
818	relay_close_buf(chan->buf[0]);
819	else
820	for_each_possible_cpu(i)
821	if (chan->buf[i])
822	relay_close_buf(chan->buf[i]);
823
824	if (chan->last_toobig)
825	printk(KERN_WARNING "relay: one or more items not logged "
826	"[item size (%Zd) > sub-buffer size (%Zd)]\n",
827	chan->last_toobig, chan->subbuf_size);
828
829	list_del(&chan->list);
830	kref_put(&chan->kref, relay_destroy_channel);
831	mutex_unlock(&relay_channels_mutex);
832	}
833	EXPORT_SYMBOL_GPL(relay_close);
834
835	/**
836	* relay_flush - close the channel
837	* @chan: the channel
838	*
839	* Flushes all channel buffers, i.e. forces buffer switch.
840	*/
841	void relay_flush(struct rchan *chan)
842	{
843	unsigned int i;
844
845	if (!chan)
846	return;
847
848	if (chan->is_global && chan->buf[0]) {
849	relay_switch_subbuf(chan->buf[0], 0);
850	return;
851	}
852
853	mutex_lock(&relay_channels_mutex);
854	for_each_possible_cpu(i)
855	if (chan->buf[i])
856	relay_switch_subbuf(chan->buf[i], 0);
857	mutex_unlock(&relay_channels_mutex);
858	}
859	EXPORT_SYMBOL_GPL(relay_flush);
860
861	/**
862	* relay_file_open - open file op for relay files
863	* @inode: the inode
864	* @filp: the file
865	*
866	* Increments the channel buffer refcount.
867	*/
868	static int relay_file_open(struct inode inode, struct file filp)
869	{
870	struct rchan_buf *buf = inode->i_private;
871	kref_get(&buf->kref);
872	filp->private_data = buf;
873
874	return nonseekable_open(inode, filp);
875	}
876
877	/**
878	* relay_file_mmap - mmap file op for relay files
879	* @filp: the file
880	* @vma: the vma describing what to map
881	*
882	* Calls upon relay_mmap_buf() to map the file into user space.
883	*/
884	static int relay_file_mmap(struct file filp, struct vm_area_struct vma)
885	{
886	struct rchan_buf *buf = filp->private_data;
887	return relay_mmap_buf(buf, vma);
888	}
889
890	/**
891	* relay_file_poll - poll file op for relay files
892	* @filp: the file
893	* @wait: poll table
894	*
895	* Poll implemention.
896	*/
897	static unsigned int relay_file_poll(struct file filp, poll_table wait)
898	{
899	unsigned int mask = 0;
900	struct rchan_buf *buf = filp->private_data;
901
902	if (buf->finalized)
903	return POLLERR;
904
905	if (filp->f_mode & FMODE_READ) {
906	poll_wait(filp, &buf->read_wait, wait);
907	if (!relay_buf_empty(buf))
908	mask \|= POLLIN \| POLLRDNORM;
909	}
910
911	return mask;
912	}
913
914	/**
915	* relay_file_release - release file op for relay files
916	* @inode: the inode
917	* @filp: the file
918	*
919	* Decrements the channel refcount, as the filesystem is
920	* no longer using it.
921	*/
922	static int relay_file_release(struct inode inode, struct file filp)
923	{
924	struct rchan_buf *buf = filp->private_data;
925	kref_put(&buf->kref, relay_remove_buf);
926
927	return 0;
928	}
929
930	/*
931	* relay_file_read_consume - update the consumed count for the buffer
932	*/
933	static void relay_file_read_consume(struct rchan_buf *buf,
934	size_t read_pos,
935	size_t bytes_consumed)
936	{
937	size_t subbuf_size = buf->chan->subbuf_size;
938	size_t n_subbufs = buf->chan->n_subbufs;
939	size_t read_subbuf;
940
941	if (buf->subbufs_produced == buf->subbufs_consumed &&
942	buf->offset == buf->bytes_consumed)
943	return;
944
945	if (buf->bytes_consumed + bytes_consumed > subbuf_size) {
946	relay_subbufs_consumed(buf->chan, buf->cpu, 1);
947	buf->bytes_consumed = 0;
948	}
949
950	buf->bytes_consumed += bytes_consumed;
951	if (!read_pos)
952	read_subbuf = buf->subbufs_consumed % n_subbufs;
953	else
954	read_subbuf = read_pos / buf->chan->subbuf_size;
955	if (buf->bytes_consumed + buf->padding[read_subbuf] == subbuf_size) {
956	if ((read_subbuf == buf->subbufs_produced % n_subbufs) &&
957	(buf->offset == subbuf_size))
958	return;
959	relay_subbufs_consumed(buf->chan, buf->cpu, 1);
960	buf->bytes_consumed = 0;
961	}
962	}
963
964	/*
965	* relay_file_read_avail - boolean, are there unconsumed bytes available?
966	*/
967	static int relay_file_read_avail(struct rchan_buf *buf, size_t read_pos)
968	{
969	size_t subbuf_size = buf->chan->subbuf_size;
970	size_t n_subbufs = buf->chan->n_subbufs;
971	size_t produced = buf->subbufs_produced;
972	size_t consumed = buf->subbufs_consumed;
973
974	relay_file_read_consume(buf, read_pos, 0);
975
976	consumed = buf->subbufs_consumed;
977
978	if (unlikely(buf->offset > subbuf_size)) {
979	if (produced == consumed)
980	return 0;
981	return 1;
982	}
983
984	if (unlikely(produced - consumed >= n_subbufs)) {
985	consumed = produced - n_subbufs + 1;
986	buf->subbufs_consumed = consumed;
987	buf->bytes_consumed = 0;
988	}
989
990	produced = (produced % n_subbufs) * subbuf_size + buf->offset;
991	consumed = (consumed % n_subbufs) * subbuf_size + buf->bytes_consumed;
992
993	if (consumed > produced)
994	produced += n_subbufs * subbuf_size;
995
996	if (consumed == produced) {
997	if (buf->offset == subbuf_size &&
998	buf->subbufs_produced > buf->subbufs_consumed)
999	return 1;
1000	return 0;
1001	}
1002
1003	return 1;
1004	}
1005
1006	/**
1007	* relay_file_read_subbuf_avail - return bytes available in sub-buffer
1008	* @read_pos: file read position
1009	* @buf: relay channel buffer
1010	*/
1011	static size_t relay_file_read_subbuf_avail(size_t read_pos,
1012	struct rchan_buf *buf)
1013	{
1014	size_t padding, avail = 0;
1015	size_t read_subbuf, read_offset, write_subbuf, write_offset;
1016	size_t subbuf_size = buf->chan->subbuf_size;
1017
1018	write_subbuf = (buf->data - buf->start) / subbuf_size;
1019	write_offset = buf->offset > subbuf_size ? subbuf_size : buf->offset;
1020	read_subbuf = read_pos / subbuf_size;
1021	read_offset = read_pos % subbuf_size;
1022	padding = buf->padding[read_subbuf];
1023
1024	if (read_subbuf == write_subbuf) {
1025	if (read_offset + padding < write_offset)
1026	avail = write_offset - (read_offset + padding);
1027	} else
1028	avail = (subbuf_size - padding) - read_offset;
1029
1030	return avail;
1031	}
1032
1033	/**
1034	* relay_file_read_start_pos - find the first available byte to read
1035	* @read_pos: file read position
1036	* @buf: relay channel buffer
1037	*
1038	* If the @read_pos is in the middle of padding, return the
1039	* position of the first actually available byte, otherwise
1040	* return the original value.
1041	*/
1042	static size_t relay_file_read_start_pos(size_t read_pos,
1043	struct rchan_buf *buf)
1044	{
1045	size_t read_subbuf, padding, padding_start, padding_end;
1046	size_t subbuf_size = buf->chan->subbuf_size;
1047	size_t n_subbufs = buf->chan->n_subbufs;
1048	size_t consumed = buf->subbufs_consumed % n_subbufs;
1049
1050	if (!read_pos)
1051	read_pos = consumed * subbuf_size + buf->bytes_consumed;
1052	read_subbuf = read_pos / subbuf_size;
1053	padding = buf->padding[read_subbuf];
1054	padding_start = (read_subbuf + 1) * subbuf_size - padding;
1055	padding_end = (read_subbuf + 1) * subbuf_size;
1056	if (read_pos >= padding_start && read_pos < padding_end) {
1057	read_subbuf = (read_subbuf + 1) % n_subbufs;
1058	read_pos = read_subbuf * subbuf_size;
1059	}
1060
1061	return read_pos;
1062	}
1063
1064	/**
1065	* relay_file_read_end_pos - return the new read position
1066	* @read_pos: file read position
1067	* @buf: relay channel buffer
1068	* @count: number of bytes to be read
1069	*/
1070	static size_t relay_file_read_end_pos(struct rchan_buf *buf,
1071	size_t read_pos,
1072	size_t count)
1073	{
1074	size_t read_subbuf, padding, end_pos;
1075	size_t subbuf_size = buf->chan->subbuf_size;
1076	size_t n_subbufs = buf->chan->n_subbufs;
1077
1078	read_subbuf = read_pos / subbuf_size;
1079	padding = buf->padding[read_subbuf];
1080	if (read_pos % subbuf_size + count + padding == subbuf_size)
1081	end_pos = (read_subbuf + 1) * subbuf_size;
1082	else
1083	end_pos = read_pos + count;
1084	if (end_pos >= subbuf_size * n_subbufs)
1085	end_pos = 0;
1086
1087	return end_pos;
1088	}
1089
1090	/*
1091	* subbuf_read_actor - read up to one subbuf's worth of data
1092	*/
1093	static int subbuf_read_actor(size_t read_start,
1094	struct rchan_buf *buf,
1095	size_t avail,
1096	read_descriptor_t *desc,
1097	read_actor_t actor)
1098	{
1099	void *from;
1100	int ret = 0;
1101
1102	from = buf->start + read_start;
1103	ret = avail;
1104	if (copy_to_user(desc->arg.buf, from, avail)) {
1105	desc->error = -EFAULT;
1106	ret = 0;
1107	}
1108	desc->arg.data += ret;
1109	desc->written += ret;
1110	desc->count -= ret;
1111
1112	return ret;
1113	}
1114
1115	typedef int (*subbuf_actor_t) (size_t read_start,
1116	struct rchan_buf *buf,
1117	size_t avail,
1118	read_descriptor_t *desc,
1119	read_actor_t actor);
1120
1121	/*
1122	* relay_file_read_subbufs - read count bytes, bridging subbuf boundaries
1123	*/
1124	static ssize_t relay_file_read_subbufs(struct file filp, loff_t ppos,
1125	subbuf_actor_t subbuf_actor,
1126	read_actor_t actor,
1127	read_descriptor_t *desc)
1128	{
1129	struct rchan_buf *buf = filp->private_data;
1130	size_t read_start, avail;
1131	int ret;
1132
1133	if (!desc->count)
1134	return 0;
1135
1136	mutex_lock(&filp->f_path.dentry->d_inode->i_mutex);
1137	do {
1138	if (!relay_file_read_avail(buf, *ppos))
1139	break;
1140
1141	read_start = relay_file_read_start_pos(*ppos, buf);
1142	avail = relay_file_read_subbuf_avail(read_start, buf);
1143	if (!avail)
1144	break;
1145
1146	avail = min(desc->count, avail);
1147	ret = subbuf_actor(read_start, buf, avail, desc, actor);
1148	if (desc->error < 0)
1149	break;
1150
1151	if (ret) {
1152	relay_file_read_consume(buf, read_start, ret);
1153	*ppos = relay_file_read_end_pos(buf, read_start, ret);
1154	}
1155	} while (desc->count && ret);
1156	mutex_unlock(&filp->f_path.dentry->d_inode->i_mutex);
1157
1158	return desc->written;
1159	}
1160
1161	static ssize_t relay_file_read(struct file *filp,
1162	char __user *buffer,
1163	size_t count,
1164	loff_t *ppos)
1165	{
1166	read_descriptor_t desc;
1167	desc.written = 0;
1168	desc.count = count;
1169	desc.arg.buf = buffer;
1170	desc.error = 0;
1171	return relay_file_read_subbufs(filp, ppos, subbuf_read_actor,
1172	NULL, &desc);
1173	}
1174
1175	static void relay_consume_bytes(struct rchan_buf *rbuf, int bytes_consumed)
1176	{
1177	rbuf->bytes_consumed += bytes_consumed;
1178
1179	if (rbuf->bytes_consumed >= rbuf->chan->subbuf_size) {
1180	relay_subbufs_consumed(rbuf->chan, rbuf->cpu, 1);
1181	rbuf->bytes_consumed %= rbuf->chan->subbuf_size;
1182	}
1183	}
1184
1185	static void relay_pipe_buf_release(struct pipe_inode_info *pipe,
1186	struct pipe_buffer *buf)
1187	{
1188	struct rchan_buf *rbuf;
1189
1190	rbuf = (struct rchan_buf *)page_private(buf->page);
1191	relay_consume_bytes(rbuf, buf->private);
1192	}
1193
1194	static const struct pipe_buf_operations relay_pipe_buf_ops = {
1195	.can_merge = 0,
1196	.map = generic_pipe_buf_map,
1197	.unmap = generic_pipe_buf_unmap,
1198	.confirm = generic_pipe_buf_confirm,
1199	.release = relay_pipe_buf_release,
1200	.steal = generic_pipe_buf_steal,
1201	.get = generic_pipe_buf_get,
1202	};
1203
1204	static void relay_page_release(struct splice_pipe_desc *spd, unsigned int i)
1205	{
1206	}
1207
1208	/*
1209	* subbuf_splice_actor - splice up to one subbuf's worth of data
1210	*/
1211	static ssize_t subbuf_splice_actor(struct file *in,
1212	loff_t *ppos,
1213	struct pipe_inode_info *pipe,
1214	size_t len,
1215	unsigned int flags,
1216	int *nonpad_ret)
1217	{
1218	unsigned int pidx, poff, total_len, subbuf_pages, nr_pages;
1219	struct rchan_buf *rbuf = in->private_data;
1220	unsigned int subbuf_size = rbuf->chan->subbuf_size;
1221	uint64_t pos = (uint64_t) *ppos;
1222	uint32_t alloc_size = (uint32_t) rbuf->chan->alloc_size;
1223	size_t read_start = (size_t) do_div(pos, alloc_size);
1224	size_t read_subbuf = read_start / subbuf_size;
1225	size_t padding = rbuf->padding[read_subbuf];
1226	size_t nonpad_end = read_subbuf * subbuf_size + subbuf_size - padding;
1227	struct page *pages[PIPE_DEF_BUFFERS];
1228	struct partial_page partial[PIPE_DEF_BUFFERS];
1229	struct splice_pipe_desc spd = {
1230	.pages = pages,
1231	.nr_pages = 0,
1232	.partial = partial,
1233	.flags = flags,
1234	.ops = &relay_pipe_buf_ops,
1235	.spd_release = relay_page_release,
1236	};
1237	ssize_t ret;
1238
1239	if (rbuf->subbufs_produced == rbuf->subbufs_consumed)
1240	return 0;
1241	if (splice_grow_spd(pipe, &spd))
1242	return -ENOMEM;
1243
1244	/*
1245	* Adjust read len, if longer than what is available
1246	*/
1247	if (len > (subbuf_size - read_start % subbuf_size))
1248	len = subbuf_size - read_start % subbuf_size;
1249
1250	subbuf_pages = rbuf->chan->alloc_size >> PAGE_SHIFT;
1251	pidx = (read_start / PAGE_SIZE) % subbuf_pages;
1252	poff = read_start & ~PAGE_MASK;
1253	nr_pages = min_t(unsigned int, subbuf_pages, pipe->buffers);
1254
1255	for (total_len = 0; spd.nr_pages < nr_pages; spd.nr_pages++) {
1256	unsigned int this_len, this_end, private;
1257	unsigned int cur_pos = read_start + total_len;
1258
1259	if (!len)
1260	break;
1261
1262	this_len = min_t(unsigned long, len, PAGE_SIZE - poff);
1263	private = this_len;
1264
1265	spd.pages[spd.nr_pages] = rbuf->page_array[pidx];
1266	spd.partial[spd.nr_pages].offset = poff;
1267
1268	this_end = cur_pos + this_len;
1269	if (this_end >= nonpad_end) {
1270	this_len = nonpad_end - cur_pos;
1271	private = this_len + padding;
1272	}
1273	spd.partial[spd.nr_pages].len = this_len;
1274	spd.partial[spd.nr_pages].private = private;
1275
1276	len -= this_len;
1277	total_len += this_len;
1278	poff = 0;
1279	pidx = (pidx + 1) % subbuf_pages;
1280
1281	if (this_end >= nonpad_end) {
1282	spd.nr_pages++;
1283	break;
1284	}
1285	}
1286
1287	ret = 0;
1288	if (!spd.nr_pages)
1289	goto out;
1290
1291	ret = *nonpad_ret = splice_to_pipe(pipe, &spd);
1292	if (ret < 0 \|\| ret < total_len)
1293	goto out;
1294
1295	if (read_start + ret == nonpad_end)
1296	ret += padding;
1297
1298	out:
1299	splice_shrink_spd(pipe, &spd);
1300	return ret;
1301	}
1302
1303	static ssize_t relay_file_splice_read(struct file *in,
1304	loff_t *ppos,
1305	struct pipe_inode_info *pipe,
1306	size_t len,
1307	unsigned int flags)
1308	{
1309	ssize_t spliced;
1310	int ret;
1311	int nonpad_ret = 0;
1312
1313	ret = 0;
1314	spliced = 0;
1315
1316	while (len && !spliced) {
1317	ret = subbuf_splice_actor(in, ppos, pipe, len, flags, &nonpad_ret);
1318	if (ret < 0)
1319	break;
1320	else if (!ret) {
1321	if (flags & SPLICE_F_NONBLOCK)
1322	ret = -EAGAIN;
1323	break;
1324	}
1325
1326	*ppos += ret;
1327	if (ret > len)
1328	len = 0;
1329	else
1330	len -= ret;
1331	spliced += nonpad_ret;
1332	nonpad_ret = 0;
1333	}
1334
1335	if (spliced)
1336	return spliced;
1337
1338	return ret;
1339	}
1340
1341	const struct file_operations relay_file_operations = {
1342	.open = relay_file_open,
1343	.poll = relay_file_poll,
1344	.mmap = relay_file_mmap,
1345	.read = relay_file_read,
1346	.llseek = no_llseek,
1347	.release = relay_file_release,
1348	.splice_read = relay_file_splice_read,
1349	};
1350	EXPORT_SYMBOL_GPL(relay_file_operations);
1351
1352	static __init int relay_init(void)
1353	{
1354
1355	hotcpu_notifier(relay_hotcpu_callback, 0);
1356	return 0;
1357	}
1358
1359	early_initcall(relay_init);
1360

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jz47xx
jz47xx-2.6.38
master

Tags:
od-2011-09-04
od-2011-09-18
v2.6.34-rc5
v2.6.34-rc6
v2.6.34-rc7
v3.9

Kernel

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Root/kernel/relay.c

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