relay: use splice_to_pipe() instead of open-coding the pipe loop
[linux-2.6.git] / kernel / relay.c
1 /*
2  * Public API and common code for kernel->userspace relay file support.
3  *
4  * See Documentation/filesystems/relayfs.txt for an overview of relayfs.
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  * nopage() vm_op implementation for relay file mapping.
41  */
42 static struct page *relay_buf_nopage(struct vm_area_struct *vma,
43                                      unsigned long address,
44                                      int *type)
45 {
46         struct page *page;
47         struct rchan_buf *buf = vma->vm_private_data;
48         unsigned long offset = address - vma->vm_start;
49
50         if (address > vma->vm_end)
51                 return NOPAGE_SIGBUS; /* Disallow mremap */
52         if (!buf)
53                 return NOPAGE_OOM;
54
55         page = vmalloc_to_page(buf->start + offset);
56         if (!page)
57                 return NOPAGE_OOM;
58         get_page(page);
59
60         if (type)
61                 *type = VM_FAULT_MINOR;
62
63         return page;
64 }
65
66 /*
67  * vm_ops for relay file mappings.
68  */
69 static struct vm_operations_struct relay_file_mmap_ops = {
70         .nopage = relay_buf_nopage,
71         .close = relay_file_mmap_close,
72 };
73
74 /**
75  *      relay_mmap_buf: - mmap channel buffer to process address space
76  *      @buf: relay channel buffer
77  *      @vma: vm_area_struct describing memory to be mapped
78  *
79  *      Returns 0 if ok, negative on error
80  *
81  *      Caller should already have grabbed mmap_sem.
82  */
83 int relay_mmap_buf(struct rchan_buf *buf, struct vm_area_struct *vma)
84 {
85         unsigned long length = vma->vm_end - vma->vm_start;
86         struct file *filp = vma->vm_file;
87
88         if (!buf)
89                 return -EBADF;
90
91         if (length != (unsigned long)buf->chan->alloc_size)
92                 return -EINVAL;
93
94         vma->vm_ops = &relay_file_mmap_ops;
95         vma->vm_private_data = buf;
96         buf->chan->cb->buf_mapped(buf, filp);
97
98         return 0;
99 }
100
101 /**
102  *      relay_alloc_buf - allocate a channel buffer
103  *      @buf: the buffer struct
104  *      @size: total size of the buffer
105  *
106  *      Returns a pointer to the resulting buffer, %NULL if unsuccessful. The
107  *      passed in size will get page aligned, if it isn't already.
108  */
109 static void *relay_alloc_buf(struct rchan_buf *buf, size_t *size)
110 {
111         void *mem;
112         unsigned int i, j, n_pages;
113
114         *size = PAGE_ALIGN(*size);
115         n_pages = *size >> PAGE_SHIFT;
116
117         buf->page_array = kcalloc(n_pages, sizeof(struct page *), GFP_KERNEL);
118         if (!buf->page_array)
119                 return NULL;
120
121         for (i = 0; i < n_pages; i++) {
122                 buf->page_array[i] = alloc_page(GFP_KERNEL);
123                 if (unlikely(!buf->page_array[i]))
124                         goto depopulate;
125                 set_page_private(buf->page_array[i], (unsigned long)buf);
126         }
127         mem = vmap(buf->page_array, n_pages, VM_MAP, PAGE_KERNEL);
128         if (!mem)
129                 goto depopulate;
130
131         memset(mem, 0, *size);
132         buf->page_count = n_pages;
133         return mem;
134
135 depopulate:
136         for (j = 0; j < i; j++)
137                 __free_page(buf->page_array[j]);
138         kfree(buf->page_array);
139         return NULL;
140 }
141
142 /**
143  *      relay_create_buf - allocate and initialize a channel buffer
144  *      @chan: the relay channel
145  *
146  *      Returns channel buffer if successful, %NULL otherwise.
147  */
148 struct rchan_buf *relay_create_buf(struct rchan *chan)
149 {
150         struct rchan_buf *buf = kzalloc(sizeof(struct rchan_buf), GFP_KERNEL);
151         if (!buf)
152                 return NULL;
153
154         buf->padding = kmalloc(chan->n_subbufs * sizeof(size_t *), GFP_KERNEL);
155         if (!buf->padding)
156                 goto free_buf;
157
158         buf->start = relay_alloc_buf(buf, &chan->alloc_size);
159         if (!buf->start)
160                 goto free_buf;
161
162         buf->chan = chan;
163         kref_get(&buf->chan->kref);
164         return buf;
165
166 free_buf:
167         kfree(buf->padding);
168         kfree(buf);
169         return NULL;
170 }
171
172 /**
173  *      relay_destroy_channel - free the channel struct
174  *      @kref: target kernel reference that contains the relay channel
175  *
176  *      Should only be called from kref_put().
177  */
178 void relay_destroy_channel(struct kref *kref)
179 {
180         struct rchan *chan = container_of(kref, struct rchan, kref);
181         kfree(chan);
182 }
183
184 /**
185  *      relay_destroy_buf - destroy an rchan_buf struct and associated buffer
186  *      @buf: the buffer struct
187  */
188 void relay_destroy_buf(struct rchan_buf *buf)
189 {
190         struct rchan *chan = buf->chan;
191         unsigned int i;
192
193         if (likely(buf->start)) {
194                 vunmap(buf->start);
195                 for (i = 0; i < buf->page_count; i++)
196                         __free_page(buf->page_array[i]);
197                 kfree(buf->page_array);
198         }
199         chan->buf[buf->cpu] = NULL;
200         kfree(buf->padding);
201         kfree(buf);
202         kref_put(&chan->kref, relay_destroy_channel);
203 }
204
205 /**
206  *      relay_remove_buf - remove a channel buffer
207  *      @kref: target kernel reference that contains the relay buffer
208  *
209  *      Removes the file from the fileystem, which also frees the
210  *      rchan_buf_struct and the channel buffer.  Should only be called from
211  *      kref_put().
212  */
213 void relay_remove_buf(struct kref *kref)
214 {
215         struct rchan_buf *buf = container_of(kref, struct rchan_buf, kref);
216         buf->chan->cb->remove_buf_file(buf->dentry);
217         relay_destroy_buf(buf);
218 }
219
220 /**
221  *      relay_buf_empty - boolean, is the channel buffer empty?
222  *      @buf: channel buffer
223  *
224  *      Returns 1 if the buffer is empty, 0 otherwise.
225  */
226 int relay_buf_empty(struct rchan_buf *buf)
227 {
228         return (buf->subbufs_produced - buf->subbufs_consumed) ? 0 : 1;
229 }
230 EXPORT_SYMBOL_GPL(relay_buf_empty);
231
232 /**
233  *      relay_buf_full - boolean, is the channel buffer full?
234  *      @buf: channel buffer
235  *
236  *      Returns 1 if the buffer is full, 0 otherwise.
237  */
238 int relay_buf_full(struct rchan_buf *buf)
239 {
240         size_t ready = buf->subbufs_produced - buf->subbufs_consumed;
241         return (ready >= buf->chan->n_subbufs) ? 1 : 0;
242 }
243 EXPORT_SYMBOL_GPL(relay_buf_full);
244
245 /*
246  * High-level relay kernel API and associated functions.
247  */
248
249 /*
250  * rchan_callback implementations defining default channel behavior.  Used
251  * in place of corresponding NULL values in client callback struct.
252  */
253
254 /*
255  * subbuf_start() default callback.  Does nothing.
256  */
257 static int subbuf_start_default_callback (struct rchan_buf *buf,
258                                           void *subbuf,
259                                           void *prev_subbuf,
260                                           size_t prev_padding)
261 {
262         if (relay_buf_full(buf))
263                 return 0;
264
265         return 1;
266 }
267
268 /*
269  * buf_mapped() default callback.  Does nothing.
270  */
271 static void buf_mapped_default_callback(struct rchan_buf *buf,
272                                         struct file *filp)
273 {
274 }
275
276 /*
277  * buf_unmapped() default callback.  Does nothing.
278  */
279 static void buf_unmapped_default_callback(struct rchan_buf *buf,
280                                           struct file *filp)
281 {
282 }
283
284 /*
285  * create_buf_file_create() default callback.  Does nothing.
286  */
287 static struct dentry *create_buf_file_default_callback(const char *filename,
288                                                        struct dentry *parent,
289                                                        int mode,
290                                                        struct rchan_buf *buf,
291                                                        int *is_global)
292 {
293         return NULL;
294 }
295
296 /*
297  * remove_buf_file() default callback.  Does nothing.
298  */
299 static int remove_buf_file_default_callback(struct dentry *dentry)
300 {
301         return -EINVAL;
302 }
303
304 /* relay channel default callbacks */
305 static struct rchan_callbacks default_channel_callbacks = {
306         .subbuf_start = subbuf_start_default_callback,
307         .buf_mapped = buf_mapped_default_callback,
308         .buf_unmapped = buf_unmapped_default_callback,
309         .create_buf_file = create_buf_file_default_callback,
310         .remove_buf_file = remove_buf_file_default_callback,
311 };
312
313 /**
314  *      wakeup_readers - wake up readers waiting on a channel
315  *      @data: contains the channel buffer
316  *
317  *      This is the timer function used to defer reader waking.
318  */
319 static void wakeup_readers(unsigned long data)
320 {
321         struct rchan_buf *buf = (struct rchan_buf *)data;
322         wake_up_interruptible(&buf->read_wait);
323 }
324
325 /**
326  *      __relay_reset - reset a channel buffer
327  *      @buf: the channel buffer
328  *      @init: 1 if this is a first-time initialization
329  *
330  *      See relay_reset() for description of effect.
331  */
332 static void __relay_reset(struct rchan_buf *buf, unsigned int init)
333 {
334         size_t i;
335
336         if (init) {
337                 init_waitqueue_head(&buf->read_wait);
338                 kref_init(&buf->kref);
339                 setup_timer(&buf->timer, wakeup_readers, (unsigned long)buf);
340         } else
341                 del_timer_sync(&buf->timer);
342
343         buf->subbufs_produced = 0;
344         buf->subbufs_consumed = 0;
345         buf->bytes_consumed = 0;
346         buf->finalized = 0;
347         buf->data = buf->start;
348         buf->offset = 0;
349
350         for (i = 0; i < buf->chan->n_subbufs; i++)
351                 buf->padding[i] = 0;
352
353         buf->chan->cb->subbuf_start(buf, buf->data, NULL, 0);
354 }
355
356 /**
357  *      relay_reset - reset the channel
358  *      @chan: the channel
359  *
360  *      This has the effect of erasing all data from all channel buffers
361  *      and restarting the channel in its initial state.  The buffers
362  *      are not freed, so any mappings are still in effect.
363  *
364  *      NOTE. Care should be taken that the channel isn't actually
365  *      being used by anything when this call is made.
366  */
367 void relay_reset(struct rchan *chan)
368 {
369         unsigned int i;
370
371         if (!chan)
372                 return;
373
374         if (chan->is_global && chan->buf[0]) {
375                 __relay_reset(chan->buf[0], 0);
376                 return;
377         }
378
379         mutex_lock(&relay_channels_mutex);
380         for_each_online_cpu(i)
381                 if (chan->buf[i])
382                         __relay_reset(chan->buf[i], 0);
383         mutex_unlock(&relay_channels_mutex);
384 }
385 EXPORT_SYMBOL_GPL(relay_reset);
386
387 /*
388  *      relay_open_buf - create a new relay channel buffer
389  *
390  *      used by relay_open() and CPU hotplug.
391  */
392 static struct rchan_buf *relay_open_buf(struct rchan *chan, unsigned int cpu)
393 {
394         struct rchan_buf *buf = NULL;
395         struct dentry *dentry;
396         char *tmpname;
397
398         if (chan->is_global)
399                 return chan->buf[0];
400
401         tmpname = kzalloc(NAME_MAX + 1, GFP_KERNEL);
402         if (!tmpname)
403                 goto end;
404         snprintf(tmpname, NAME_MAX, "%s%d", chan->base_filename, cpu);
405
406         buf = relay_create_buf(chan);
407         if (!buf)
408                 goto free_name;
409
410         buf->cpu = cpu;
411         __relay_reset(buf, 1);
412
413         /* Create file in fs */
414         dentry = chan->cb->create_buf_file(tmpname, chan->parent, S_IRUSR,
415                                            buf, &chan->is_global);
416         if (!dentry)
417                 goto free_buf;
418
419         buf->dentry = dentry;
420
421         if(chan->is_global) {
422                 chan->buf[0] = buf;
423                 buf->cpu = 0;
424         }
425
426         goto free_name;
427
428 free_buf:
429         relay_destroy_buf(buf);
430 free_name:
431         kfree(tmpname);
432 end:
433         return buf;
434 }
435
436 /**
437  *      relay_close_buf - close a channel buffer
438  *      @buf: channel buffer
439  *
440  *      Marks the buffer finalized and restores the default callbacks.
441  *      The channel buffer and channel buffer data structure are then freed
442  *      automatically when the last reference is given up.
443  */
444 static void relay_close_buf(struct rchan_buf *buf)
445 {
446         buf->finalized = 1;
447         del_timer_sync(&buf->timer);
448         kref_put(&buf->kref, relay_remove_buf);
449 }
450
451 static void setup_callbacks(struct rchan *chan,
452                                    struct rchan_callbacks *cb)
453 {
454         if (!cb) {
455                 chan->cb = &default_channel_callbacks;
456                 return;
457         }
458
459         if (!cb->subbuf_start)
460                 cb->subbuf_start = subbuf_start_default_callback;
461         if (!cb->buf_mapped)
462                 cb->buf_mapped = buf_mapped_default_callback;
463         if (!cb->buf_unmapped)
464                 cb->buf_unmapped = buf_unmapped_default_callback;
465         if (!cb->create_buf_file)
466                 cb->create_buf_file = create_buf_file_default_callback;
467         if (!cb->remove_buf_file)
468                 cb->remove_buf_file = remove_buf_file_default_callback;
469         chan->cb = cb;
470 }
471
472 /**
473  *      relay_hotcpu_callback - CPU hotplug callback
474  *      @nb: notifier block
475  *      @action: hotplug action to take
476  *      @hcpu: CPU number
477  *
478  *      Returns the success/failure of the operation. (%NOTIFY_OK, %NOTIFY_BAD)
479  */
480 static int __cpuinit relay_hotcpu_callback(struct notifier_block *nb,
481                                 unsigned long action,
482                                 void *hcpu)
483 {
484         unsigned int hotcpu = (unsigned long)hcpu;
485         struct rchan *chan;
486
487         switch(action) {
488         case CPU_UP_PREPARE:
489         case CPU_UP_PREPARE_FROZEN:
490                 mutex_lock(&relay_channels_mutex);
491                 list_for_each_entry(chan, &relay_channels, list) {
492                         if (chan->buf[hotcpu])
493                                 continue;
494                         chan->buf[hotcpu] = relay_open_buf(chan, hotcpu);
495                         if(!chan->buf[hotcpu]) {
496                                 printk(KERN_ERR
497                                         "relay_hotcpu_callback: cpu %d buffer "
498                                         "creation failed\n", hotcpu);
499                                 mutex_unlock(&relay_channels_mutex);
500                                 return NOTIFY_BAD;
501                         }
502                 }
503                 mutex_unlock(&relay_channels_mutex);
504                 break;
505         case CPU_DEAD:
506         case CPU_DEAD_FROZEN:
507                 /* No need to flush the cpu : will be flushed upon
508                  * final relay_flush() call. */
509                 break;
510         }
511         return NOTIFY_OK;
512 }
513
514 /**
515  *      relay_open - create a new relay channel
516  *      @base_filename: base name of files to create
517  *      @parent: dentry of parent directory, %NULL for root directory
518  *      @subbuf_size: size of sub-buffers
519  *      @n_subbufs: number of sub-buffers
520  *      @cb: client callback functions
521  *      @private_data: user-defined data
522  *
523  *      Returns channel pointer if successful, %NULL otherwise.
524  *
525  *      Creates a channel buffer for each cpu using the sizes and
526  *      attributes specified.  The created channel buffer files
527  *      will be named base_filename0...base_filenameN-1.  File
528  *      permissions will be %S_IRUSR.
529  */
530 struct rchan *relay_open(const char *base_filename,
531                          struct dentry *parent,
532                          size_t subbuf_size,
533                          size_t n_subbufs,
534                          struct rchan_callbacks *cb,
535                          void *private_data)
536 {
537         unsigned int i;
538         struct rchan *chan;
539         if (!base_filename)
540                 return NULL;
541
542         if (!(subbuf_size && n_subbufs))
543                 return NULL;
544
545         chan = kzalloc(sizeof(struct rchan), GFP_KERNEL);
546         if (!chan)
547                 return NULL;
548
549         chan->version = RELAYFS_CHANNEL_VERSION;
550         chan->n_subbufs = n_subbufs;
551         chan->subbuf_size = subbuf_size;
552         chan->alloc_size = FIX_SIZE(subbuf_size * n_subbufs);
553         chan->parent = parent;
554         chan->private_data = private_data;
555         strlcpy(chan->base_filename, base_filename, NAME_MAX);
556         setup_callbacks(chan, cb);
557         kref_init(&chan->kref);
558
559         mutex_lock(&relay_channels_mutex);
560         for_each_online_cpu(i) {
561                 chan->buf[i] = relay_open_buf(chan, i);
562                 if (!chan->buf[i])
563                         goto free_bufs;
564         }
565         list_add(&chan->list, &relay_channels);
566         mutex_unlock(&relay_channels_mutex);
567
568         return chan;
569
570 free_bufs:
571         for_each_online_cpu(i) {
572                 if (!chan->buf[i])
573                         break;
574                 relay_close_buf(chan->buf[i]);
575         }
576
577         kref_put(&chan->kref, relay_destroy_channel);
578         mutex_unlock(&relay_channels_mutex);
579         return NULL;
580 }
581 EXPORT_SYMBOL_GPL(relay_open);
582
583 /**
584  *      relay_switch_subbuf - switch to a new sub-buffer
585  *      @buf: channel buffer
586  *      @length: size of current event
587  *
588  *      Returns either the length passed in or 0 if full.
589  *
590  *      Performs sub-buffer-switch tasks such as invoking callbacks,
591  *      updating padding counts, waking up readers, etc.
592  */
593 size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length)
594 {
595         void *old, *new;
596         size_t old_subbuf, new_subbuf;
597
598         if (unlikely(length > buf->chan->subbuf_size))
599                 goto toobig;
600
601         if (buf->offset != buf->chan->subbuf_size + 1) {
602                 buf->prev_padding = buf->chan->subbuf_size - buf->offset;
603                 old_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
604                 buf->padding[old_subbuf] = buf->prev_padding;
605                 buf->subbufs_produced++;
606                 buf->dentry->d_inode->i_size += buf->chan->subbuf_size -
607                         buf->padding[old_subbuf];
608                 smp_mb();
609                 if (waitqueue_active(&buf->read_wait))
610                         /*
611                          * Calling wake_up_interruptible() from here
612                          * will deadlock if we happen to be logging
613                          * from the scheduler (trying to re-grab
614                          * rq->lock), so defer it.
615                          */
616                         __mod_timer(&buf->timer, jiffies + 1);
617         }
618
619         old = buf->data;
620         new_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
621         new = buf->start + new_subbuf * buf->chan->subbuf_size;
622         buf->offset = 0;
623         if (!buf->chan->cb->subbuf_start(buf, new, old, buf->prev_padding)) {
624                 buf->offset = buf->chan->subbuf_size + 1;
625                 return 0;
626         }
627         buf->data = new;
628         buf->padding[new_subbuf] = 0;
629
630         if (unlikely(length + buf->offset > buf->chan->subbuf_size))
631                 goto toobig;
632
633         return length;
634
635 toobig:
636         buf->chan->last_toobig = length;
637         return 0;
638 }
639 EXPORT_SYMBOL_GPL(relay_switch_subbuf);
640
641 /**
642  *      relay_subbufs_consumed - update the buffer's sub-buffers-consumed count
643  *      @chan: the channel
644  *      @cpu: the cpu associated with the channel buffer to update
645  *      @subbufs_consumed: number of sub-buffers to add to current buf's count
646  *
647  *      Adds to the channel buffer's consumed sub-buffer count.
648  *      subbufs_consumed should be the number of sub-buffers newly consumed,
649  *      not the total consumed.
650  *
651  *      NOTE. Kernel clients don't need to call this function if the channel
652  *      mode is 'overwrite'.
653  */
654 void relay_subbufs_consumed(struct rchan *chan,
655                             unsigned int cpu,
656                             size_t subbufs_consumed)
657 {
658         struct rchan_buf *buf;
659
660         if (!chan)
661                 return;
662
663         if (cpu >= NR_CPUS || !chan->buf[cpu])
664                 return;
665
666         buf = chan->buf[cpu];
667         buf->subbufs_consumed += subbufs_consumed;
668         if (buf->subbufs_consumed > buf->subbufs_produced)
669                 buf->subbufs_consumed = buf->subbufs_produced;
670 }
671 EXPORT_SYMBOL_GPL(relay_subbufs_consumed);
672
673 /**
674  *      relay_close - close the channel
675  *      @chan: the channel
676  *
677  *      Closes all channel buffers and frees the channel.
678  */
679 void relay_close(struct rchan *chan)
680 {
681         unsigned int i;
682
683         if (!chan)
684                 return;
685
686         mutex_lock(&relay_channels_mutex);
687         if (chan->is_global && chan->buf[0])
688                 relay_close_buf(chan->buf[0]);
689         else
690                 for_each_possible_cpu(i)
691                         if (chan->buf[i])
692                                 relay_close_buf(chan->buf[i]);
693
694         if (chan->last_toobig)
695                 printk(KERN_WARNING "relay: one or more items not logged "
696                        "[item size (%Zd) > sub-buffer size (%Zd)]\n",
697                        chan->last_toobig, chan->subbuf_size);
698
699         list_del(&chan->list);
700         kref_put(&chan->kref, relay_destroy_channel);
701         mutex_unlock(&relay_channels_mutex);
702 }
703 EXPORT_SYMBOL_GPL(relay_close);
704
705 /**
706  *      relay_flush - close the channel
707  *      @chan: the channel
708  *
709  *      Flushes all channel buffers, i.e. forces buffer switch.
710  */
711 void relay_flush(struct rchan *chan)
712 {
713         unsigned int i;
714
715         if (!chan)
716                 return;
717
718         if (chan->is_global && chan->buf[0]) {
719                 relay_switch_subbuf(chan->buf[0], 0);
720                 return;
721         }
722
723         mutex_lock(&relay_channels_mutex);
724         for_each_possible_cpu(i)
725                 if (chan->buf[i])
726                         relay_switch_subbuf(chan->buf[i], 0);
727         mutex_unlock(&relay_channels_mutex);
728 }
729 EXPORT_SYMBOL_GPL(relay_flush);
730
731 /**
732  *      relay_file_open - open file op for relay files
733  *      @inode: the inode
734  *      @filp: the file
735  *
736  *      Increments the channel buffer refcount.
737  */
738 static int relay_file_open(struct inode *inode, struct file *filp)
739 {
740         struct rchan_buf *buf = inode->i_private;
741         kref_get(&buf->kref);
742         filp->private_data = buf;
743
744         return 0;
745 }
746
747 /**
748  *      relay_file_mmap - mmap file op for relay files
749  *      @filp: the file
750  *      @vma: the vma describing what to map
751  *
752  *      Calls upon relay_mmap_buf() to map the file into user space.
753  */
754 static int relay_file_mmap(struct file *filp, struct vm_area_struct *vma)
755 {
756         struct rchan_buf *buf = filp->private_data;
757         return relay_mmap_buf(buf, vma);
758 }
759
760 /**
761  *      relay_file_poll - poll file op for relay files
762  *      @filp: the file
763  *      @wait: poll table
764  *
765  *      Poll implemention.
766  */
767 static unsigned int relay_file_poll(struct file *filp, poll_table *wait)
768 {
769         unsigned int mask = 0;
770         struct rchan_buf *buf = filp->private_data;
771
772         if (buf->finalized)
773                 return POLLERR;
774
775         if (filp->f_mode & FMODE_READ) {
776                 poll_wait(filp, &buf->read_wait, wait);
777                 if (!relay_buf_empty(buf))
778                         mask |= POLLIN | POLLRDNORM;
779         }
780
781         return mask;
782 }
783
784 /**
785  *      relay_file_release - release file op for relay files
786  *      @inode: the inode
787  *      @filp: the file
788  *
789  *      Decrements the channel refcount, as the filesystem is
790  *      no longer using it.
791  */
792 static int relay_file_release(struct inode *inode, struct file *filp)
793 {
794         struct rchan_buf *buf = filp->private_data;
795         kref_put(&buf->kref, relay_remove_buf);
796
797         return 0;
798 }
799
800 /*
801  *      relay_file_read_consume - update the consumed count for the buffer
802  */
803 static void relay_file_read_consume(struct rchan_buf *buf,
804                                     size_t read_pos,
805                                     size_t bytes_consumed)
806 {
807         size_t subbuf_size = buf->chan->subbuf_size;
808         size_t n_subbufs = buf->chan->n_subbufs;
809         size_t read_subbuf;
810
811         if (buf->bytes_consumed + bytes_consumed > subbuf_size) {
812                 relay_subbufs_consumed(buf->chan, buf->cpu, 1);
813                 buf->bytes_consumed = 0;
814         }
815
816         buf->bytes_consumed += bytes_consumed;
817         if (!read_pos)
818                 read_subbuf = buf->subbufs_consumed % n_subbufs;
819         else
820                 read_subbuf = read_pos / buf->chan->subbuf_size;
821         if (buf->bytes_consumed + buf->padding[read_subbuf] == subbuf_size) {
822                 if ((read_subbuf == buf->subbufs_produced % n_subbufs) &&
823                     (buf->offset == subbuf_size))
824                         return;
825                 relay_subbufs_consumed(buf->chan, buf->cpu, 1);
826                 buf->bytes_consumed = 0;
827         }
828 }
829
830 /*
831  *      relay_file_read_avail - boolean, are there unconsumed bytes available?
832  */
833 static int relay_file_read_avail(struct rchan_buf *buf, size_t read_pos)
834 {
835         size_t subbuf_size = buf->chan->subbuf_size;
836         size_t n_subbufs = buf->chan->n_subbufs;
837         size_t produced = buf->subbufs_produced;
838         size_t consumed = buf->subbufs_consumed;
839
840         relay_file_read_consume(buf, read_pos, 0);
841
842         if (unlikely(buf->offset > subbuf_size)) {
843                 if (produced == consumed)
844                         return 0;
845                 return 1;
846         }
847
848         if (unlikely(produced - consumed >= n_subbufs)) {
849                 consumed = produced - n_subbufs + 1;
850                 buf->subbufs_consumed = consumed;
851                 buf->bytes_consumed = 0;
852         }
853         
854         produced = (produced % n_subbufs) * subbuf_size + buf->offset;
855         consumed = (consumed % n_subbufs) * subbuf_size + buf->bytes_consumed;
856
857         if (consumed > produced)
858                 produced += n_subbufs * subbuf_size;
859         
860         if (consumed == produced)
861                 return 0;
862
863         return 1;
864 }
865
866 /**
867  *      relay_file_read_subbuf_avail - return bytes available in sub-buffer
868  *      @read_pos: file read position
869  *      @buf: relay channel buffer
870  */
871 static size_t relay_file_read_subbuf_avail(size_t read_pos,
872                                            struct rchan_buf *buf)
873 {
874         size_t padding, avail = 0;
875         size_t read_subbuf, read_offset, write_subbuf, write_offset;
876         size_t subbuf_size = buf->chan->subbuf_size;
877
878         write_subbuf = (buf->data - buf->start) / subbuf_size;
879         write_offset = buf->offset > subbuf_size ? subbuf_size : buf->offset;
880         read_subbuf = read_pos / subbuf_size;
881         read_offset = read_pos % subbuf_size;
882         padding = buf->padding[read_subbuf];
883
884         if (read_subbuf == write_subbuf) {
885                 if (read_offset + padding < write_offset)
886                         avail = write_offset - (read_offset + padding);
887         } else
888                 avail = (subbuf_size - padding) - read_offset;
889
890         return avail;
891 }
892
893 /**
894  *      relay_file_read_start_pos - find the first available byte to read
895  *      @read_pos: file read position
896  *      @buf: relay channel buffer
897  *
898  *      If the @read_pos is in the middle of padding, return the
899  *      position of the first actually available byte, otherwise
900  *      return the original value.
901  */
902 static size_t relay_file_read_start_pos(size_t read_pos,
903                                         struct rchan_buf *buf)
904 {
905         size_t read_subbuf, padding, padding_start, padding_end;
906         size_t subbuf_size = buf->chan->subbuf_size;
907         size_t n_subbufs = buf->chan->n_subbufs;
908         size_t consumed = buf->subbufs_consumed % n_subbufs;
909
910         if (!read_pos)
911                 read_pos = consumed * subbuf_size + buf->bytes_consumed;
912         read_subbuf = read_pos / subbuf_size;
913         padding = buf->padding[read_subbuf];
914         padding_start = (read_subbuf + 1) * subbuf_size - padding;
915         padding_end = (read_subbuf + 1) * subbuf_size;
916         if (read_pos >= padding_start && read_pos < padding_end) {
917                 read_subbuf = (read_subbuf + 1) % n_subbufs;
918                 read_pos = read_subbuf * subbuf_size;
919         }
920
921         return read_pos;
922 }
923
924 /**
925  *      relay_file_read_end_pos - return the new read position
926  *      @read_pos: file read position
927  *      @buf: relay channel buffer
928  *      @count: number of bytes to be read
929  */
930 static size_t relay_file_read_end_pos(struct rchan_buf *buf,
931                                       size_t read_pos,
932                                       size_t count)
933 {
934         size_t read_subbuf, padding, end_pos;
935         size_t subbuf_size = buf->chan->subbuf_size;
936         size_t n_subbufs = buf->chan->n_subbufs;
937
938         read_subbuf = read_pos / subbuf_size;
939         padding = buf->padding[read_subbuf];
940         if (read_pos % subbuf_size + count + padding == subbuf_size)
941                 end_pos = (read_subbuf + 1) * subbuf_size;
942         else
943                 end_pos = read_pos + count;
944         if (end_pos >= subbuf_size * n_subbufs)
945                 end_pos = 0;
946
947         return end_pos;
948 }
949
950 /*
951  *      subbuf_read_actor - read up to one subbuf's worth of data
952  */
953 static int subbuf_read_actor(size_t read_start,
954                              struct rchan_buf *buf,
955                              size_t avail,
956                              read_descriptor_t *desc,
957                              read_actor_t actor)
958 {
959         void *from;
960         int ret = 0;
961
962         from = buf->start + read_start;
963         ret = avail;
964         if (copy_to_user(desc->arg.buf, from, avail)) {
965                 desc->error = -EFAULT;
966                 ret = 0;
967         }
968         desc->arg.data += ret;
969         desc->written += ret;
970         desc->count -= ret;
971
972         return ret;
973 }
974
975 typedef int (*subbuf_actor_t) (size_t read_start,
976                                struct rchan_buf *buf,
977                                size_t avail,
978                                read_descriptor_t *desc,
979                                read_actor_t actor);
980
981 /*
982  *      relay_file_read_subbufs - read count bytes, bridging subbuf boundaries
983  */
984 static ssize_t relay_file_read_subbufs(struct file *filp, loff_t *ppos,
985                                         subbuf_actor_t subbuf_actor,
986                                         read_actor_t actor,
987                                         read_descriptor_t *desc)
988 {
989         struct rchan_buf *buf = filp->private_data;
990         size_t read_start, avail;
991         int ret;
992
993         if (!desc->count)
994                 return 0;
995
996         mutex_lock(&filp->f_path.dentry->d_inode->i_mutex);
997         do {
998                 if (!relay_file_read_avail(buf, *ppos))
999                         break;
1000
1001                 read_start = relay_file_read_start_pos(*ppos, buf);
1002                 avail = relay_file_read_subbuf_avail(read_start, buf);
1003                 if (!avail)
1004                         break;
1005
1006                 avail = min(desc->count, avail);
1007                 ret = subbuf_actor(read_start, buf, avail, desc, actor);
1008                 if (desc->error < 0)
1009                         break;
1010
1011                 if (ret) {
1012                         relay_file_read_consume(buf, read_start, ret);
1013                         *ppos = relay_file_read_end_pos(buf, read_start, ret);
1014                 }
1015         } while (desc->count && ret);
1016         mutex_unlock(&filp->f_path.dentry->d_inode->i_mutex);
1017
1018         return desc->written;
1019 }
1020
1021 static ssize_t relay_file_read(struct file *filp,
1022                                char __user *buffer,
1023                                size_t count,
1024                                loff_t *ppos)
1025 {
1026         read_descriptor_t desc;
1027         desc.written = 0;
1028         desc.count = count;
1029         desc.arg.buf = buffer;
1030         desc.error = 0;
1031         return relay_file_read_subbufs(filp, ppos, subbuf_read_actor,
1032                                        NULL, &desc);
1033 }
1034
1035 static void relay_consume_bytes(struct rchan_buf *rbuf, int bytes_consumed)
1036 {
1037         rbuf->bytes_consumed += bytes_consumed;
1038
1039         if (rbuf->bytes_consumed >= rbuf->chan->subbuf_size) {
1040                 relay_subbufs_consumed(rbuf->chan, rbuf->cpu, 1);
1041                 rbuf->bytes_consumed %= rbuf->chan->subbuf_size;
1042         }
1043 }
1044
1045 static void relay_pipe_buf_release(struct pipe_inode_info *pipe,
1046                                    struct pipe_buffer *buf)
1047 {
1048         struct rchan_buf *rbuf;
1049
1050         rbuf = (struct rchan_buf *)page_private(buf->page);
1051         relay_consume_bytes(rbuf, buf->private);
1052 }
1053
1054 static struct pipe_buf_operations relay_pipe_buf_ops = {
1055         .can_merge = 0,
1056         .map = generic_pipe_buf_map,
1057         .unmap = generic_pipe_buf_unmap,
1058         .pin = generic_pipe_buf_pin,
1059         .release = relay_pipe_buf_release,
1060         .steal = generic_pipe_buf_steal,
1061         .get = generic_pipe_buf_get,
1062 };
1063
1064 /**
1065  *      subbuf_splice_actor - splice up to one subbuf's worth of data
1066  */
1067 static int subbuf_splice_actor(struct file *in,
1068                                loff_t *ppos,
1069                                struct pipe_inode_info *pipe,
1070                                size_t len,
1071                                unsigned int flags,
1072                                int *nonpad_ret)
1073 {
1074         unsigned int pidx, poff, total_len, subbuf_pages, ret;
1075         struct rchan_buf *rbuf = in->private_data;
1076         unsigned int subbuf_size = rbuf->chan->subbuf_size;
1077         size_t read_start = ((size_t)*ppos) % rbuf->chan->alloc_size;
1078         size_t read_subbuf = read_start / subbuf_size;
1079         size_t padding = rbuf->padding[read_subbuf];
1080         size_t nonpad_end = read_subbuf * subbuf_size + subbuf_size - padding;
1081         struct page *pages[PIPE_BUFFERS];
1082         struct partial_page partial[PIPE_BUFFERS];
1083         struct splice_pipe_desc spd = {
1084                 .pages = pages,
1085                 .nr_pages = 0,
1086                 .partial = partial,
1087                 .flags = flags,
1088                 .ops = &relay_pipe_buf_ops,
1089         };
1090
1091         if (rbuf->subbufs_produced == rbuf->subbufs_consumed)
1092                 return 0;
1093
1094         /*
1095          * Adjust read len, if longer than what is available
1096          */
1097         if (len > (subbuf_size - read_start % subbuf_size))
1098                 len = subbuf_size - read_start % subbuf_size;
1099
1100         subbuf_pages = rbuf->chan->alloc_size >> PAGE_SHIFT;
1101         pidx = (read_start / PAGE_SIZE) % subbuf_pages;
1102         poff = read_start & ~PAGE_MASK;
1103
1104         for (total_len = 0; spd.nr_pages < subbuf_pages; spd.nr_pages++) {
1105                 unsigned int this_len, this_end, private;
1106                 unsigned int cur_pos = read_start + total_len;
1107
1108                 if (!len)
1109                         break;
1110
1111                 this_len = min_t(unsigned long, len, PAGE_SIZE - poff);
1112                 private = this_len;
1113
1114                 spd.pages[spd.nr_pages] = rbuf->page_array[pidx];
1115                 spd.partial[spd.nr_pages].offset = poff;
1116
1117                 this_end = cur_pos + this_len;
1118                 if (this_end >= nonpad_end) {
1119                         this_len = nonpad_end - cur_pos;
1120                         private = this_len + padding;
1121                 }
1122                 spd.partial[spd.nr_pages].len = this_len;
1123                 spd.partial[spd.nr_pages].private = private;
1124
1125                 len -= this_len;
1126                 total_len += this_len;
1127                 poff = 0;
1128                 pidx = (pidx + 1) % subbuf_pages;
1129
1130                 if (this_end >= nonpad_end) {
1131                         spd.nr_pages++;
1132                         break;
1133                 }
1134         }
1135
1136         if (!spd.nr_pages)
1137                 return 0;
1138
1139         ret = *nonpad_ret = splice_to_pipe(pipe, &spd);
1140         if (ret < 0 || ret < total_len)
1141                 return ret;
1142
1143         if (read_start + ret == nonpad_end)
1144                 ret += padding;
1145
1146         return ret;
1147 }
1148
1149 static ssize_t relay_file_splice_read(struct file *in,
1150                                       loff_t *ppos,
1151                                       struct pipe_inode_info *pipe,
1152                                       size_t len,
1153                                       unsigned int flags)
1154 {
1155         ssize_t spliced;
1156         int ret;
1157         int nonpad_ret = 0;
1158
1159         ret = 0;
1160         spliced = 0;
1161
1162         while (len) {
1163                 ret = subbuf_splice_actor(in, ppos, pipe, len, flags, &nonpad_ret);
1164                 if (ret < 0)
1165                         break;
1166                 else if (!ret) {
1167                         if (spliced)
1168                                 break;
1169                         if (flags & SPLICE_F_NONBLOCK) {
1170                                 ret = -EAGAIN;
1171                                 break;
1172                         }
1173                 }
1174
1175                 *ppos += ret;
1176                 if (ret > len)
1177                         len = 0;
1178                 else
1179                         len -= ret;
1180                 spliced += nonpad_ret;
1181                 nonpad_ret = 0;
1182         }
1183
1184         if (spliced)
1185                 return spliced;
1186
1187         return ret;
1188 }
1189
1190 const struct file_operations relay_file_operations = {
1191         .open           = relay_file_open,
1192         .poll           = relay_file_poll,
1193         .mmap           = relay_file_mmap,
1194         .read           = relay_file_read,
1195         .llseek         = no_llseek,
1196         .release        = relay_file_release,
1197         .splice_read    = relay_file_splice_read,
1198 };
1199 EXPORT_SYMBOL_GPL(relay_file_operations);
1200
1201 static __init int relay_init(void)
1202 {
1203
1204         hotcpu_notifier(relay_hotcpu_callback, 0);
1205         return 0;
1206 }
1207
1208 module_init(relay_init);