relay: use plain timer instead of delayed work
[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
25 /* list of open channels, for cpu hotplug */
26 static DEFINE_MUTEX(relay_channels_mutex);
27 static LIST_HEAD(relay_channels);
28
29 /*
30  * close() vm_op implementation for relay file mapping.
31  */
32 static void relay_file_mmap_close(struct vm_area_struct *vma)
33 {
34         struct rchan_buf *buf = vma->vm_private_data;
35         buf->chan->cb->buf_unmapped(buf, vma->vm_file);
36 }
37
38 /*
39  * nopage() vm_op implementation for relay file mapping.
40  */
41 static struct page *relay_buf_nopage(struct vm_area_struct *vma,
42                                      unsigned long address,
43                                      int *type)
44 {
45         struct page *page;
46         struct rchan_buf *buf = vma->vm_private_data;
47         unsigned long offset = address - vma->vm_start;
48
49         if (address > vma->vm_end)
50                 return NOPAGE_SIGBUS; /* Disallow mremap */
51         if (!buf)
52                 return NOPAGE_OOM;
53
54         page = vmalloc_to_page(buf->start + offset);
55         if (!page)
56                 return NOPAGE_OOM;
57         get_page(page);
58
59         if (type)
60                 *type = VM_FAULT_MINOR;
61
62         return page;
63 }
64
65 /*
66  * vm_ops for relay file mappings.
67  */
68 static struct vm_operations_struct relay_file_mmap_ops = {
69         .nopage = relay_buf_nopage,
70         .close = relay_file_mmap_close,
71 };
72
73 /**
74  *      relay_mmap_buf: - mmap channel buffer to process address space
75  *      @buf: relay channel buffer
76  *      @vma: vm_area_struct describing memory to be mapped
77  *
78  *      Returns 0 if ok, negative on error
79  *
80  *      Caller should already have grabbed mmap_sem.
81  */
82 int relay_mmap_buf(struct rchan_buf *buf, struct vm_area_struct *vma)
83 {
84         unsigned long length = vma->vm_end - vma->vm_start;
85         struct file *filp = vma->vm_file;
86
87         if (!buf)
88                 return -EBADF;
89
90         if (length != (unsigned long)buf->chan->alloc_size)
91                 return -EINVAL;
92
93         vma->vm_ops = &relay_file_mmap_ops;
94         vma->vm_private_data = buf;
95         buf->chan->cb->buf_mapped(buf, filp);
96
97         return 0;
98 }
99
100 /**
101  *      relay_alloc_buf - allocate a channel buffer
102  *      @buf: the buffer struct
103  *      @size: total size of the buffer
104  *
105  *      Returns a pointer to the resulting buffer, %NULL if unsuccessful. The
106  *      passed in size will get page aligned, if it isn't already.
107  */
108 static void *relay_alloc_buf(struct rchan_buf *buf, size_t *size)
109 {
110         void *mem;
111         unsigned int i, j, n_pages;
112
113         *size = PAGE_ALIGN(*size);
114         n_pages = *size >> PAGE_SHIFT;
115
116         buf->page_array = kcalloc(n_pages, sizeof(struct page *), GFP_KERNEL);
117         if (!buf->page_array)
118                 return NULL;
119
120         for (i = 0; i < n_pages; i++) {
121                 buf->page_array[i] = alloc_page(GFP_KERNEL);
122                 if (unlikely(!buf->page_array[i]))
123                         goto depopulate;
124         }
125         mem = vmap(buf->page_array, n_pages, VM_MAP, PAGE_KERNEL);
126         if (!mem)
127                 goto depopulate;
128
129         memset(mem, 0, *size);
130         buf->page_count = n_pages;
131         return mem;
132
133 depopulate:
134         for (j = 0; j < i; j++)
135                 __free_page(buf->page_array[j]);
136         kfree(buf->page_array);
137         return NULL;
138 }
139
140 /**
141  *      relay_create_buf - allocate and initialize a channel buffer
142  *      @chan: the relay channel
143  *
144  *      Returns channel buffer if successful, %NULL otherwise.
145  */
146 struct rchan_buf *relay_create_buf(struct rchan *chan)
147 {
148         struct rchan_buf *buf = kzalloc(sizeof(struct rchan_buf), GFP_KERNEL);
149         if (!buf)
150                 return NULL;
151
152         buf->padding = kmalloc(chan->n_subbufs * sizeof(size_t *), GFP_KERNEL);
153         if (!buf->padding)
154                 goto free_buf;
155
156         buf->start = relay_alloc_buf(buf, &chan->alloc_size);
157         if (!buf->start)
158                 goto free_buf;
159
160         buf->chan = chan;
161         kref_get(&buf->chan->kref);
162         return buf;
163
164 free_buf:
165         kfree(buf->padding);
166         kfree(buf);
167         return NULL;
168 }
169
170 /**
171  *      relay_destroy_channel - free the channel struct
172  *      @kref: target kernel reference that contains the relay channel
173  *
174  *      Should only be called from kref_put().
175  */
176 void relay_destroy_channel(struct kref *kref)
177 {
178         struct rchan *chan = container_of(kref, struct rchan, kref);
179         kfree(chan);
180 }
181
182 /**
183  *      relay_destroy_buf - destroy an rchan_buf struct and associated buffer
184  *      @buf: the buffer struct
185  */
186 void relay_destroy_buf(struct rchan_buf *buf)
187 {
188         struct rchan *chan = buf->chan;
189         unsigned int i;
190
191         if (likely(buf->start)) {
192                 vunmap(buf->start);
193                 for (i = 0; i < buf->page_count; i++)
194                         __free_page(buf->page_array[i]);
195                 kfree(buf->page_array);
196         }
197         chan->buf[buf->cpu] = NULL;
198         kfree(buf->padding);
199         kfree(buf);
200         kref_put(&chan->kref, relay_destroy_channel);
201 }
202
203 /**
204  *      relay_remove_buf - remove a channel buffer
205  *      @kref: target kernel reference that contains the relay buffer
206  *
207  *      Removes the file from the fileystem, which also frees the
208  *      rchan_buf_struct and the channel buffer.  Should only be called from
209  *      kref_put().
210  */
211 void relay_remove_buf(struct kref *kref)
212 {
213         struct rchan_buf *buf = container_of(kref, struct rchan_buf, kref);
214         buf->chan->cb->remove_buf_file(buf->dentry);
215         relay_destroy_buf(buf);
216 }
217
218 /**
219  *      relay_buf_empty - boolean, is the channel buffer empty?
220  *      @buf: channel buffer
221  *
222  *      Returns 1 if the buffer is empty, 0 otherwise.
223  */
224 int relay_buf_empty(struct rchan_buf *buf)
225 {
226         return (buf->subbufs_produced - buf->subbufs_consumed) ? 0 : 1;
227 }
228 EXPORT_SYMBOL_GPL(relay_buf_empty);
229
230 /**
231  *      relay_buf_full - boolean, is the channel buffer full?
232  *      @buf: channel buffer
233  *
234  *      Returns 1 if the buffer is full, 0 otherwise.
235  */
236 int relay_buf_full(struct rchan_buf *buf)
237 {
238         size_t ready = buf->subbufs_produced - buf->subbufs_consumed;
239         return (ready >= buf->chan->n_subbufs) ? 1 : 0;
240 }
241 EXPORT_SYMBOL_GPL(relay_buf_full);
242
243 /*
244  * High-level relay kernel API and associated functions.
245  */
246
247 /*
248  * rchan_callback implementations defining default channel behavior.  Used
249  * in place of corresponding NULL values in client callback struct.
250  */
251
252 /*
253  * subbuf_start() default callback.  Does nothing.
254  */
255 static int subbuf_start_default_callback (struct rchan_buf *buf,
256                                           void *subbuf,
257                                           void *prev_subbuf,
258                                           size_t prev_padding)
259 {
260         if (relay_buf_full(buf))
261                 return 0;
262
263         return 1;
264 }
265
266 /*
267  * buf_mapped() default callback.  Does nothing.
268  */
269 static void buf_mapped_default_callback(struct rchan_buf *buf,
270                                         struct file *filp)
271 {
272 }
273
274 /*
275  * buf_unmapped() default callback.  Does nothing.
276  */
277 static void buf_unmapped_default_callback(struct rchan_buf *buf,
278                                           struct file *filp)
279 {
280 }
281
282 /*
283  * create_buf_file_create() default callback.  Does nothing.
284  */
285 static struct dentry *create_buf_file_default_callback(const char *filename,
286                                                        struct dentry *parent,
287                                                        int mode,
288                                                        struct rchan_buf *buf,
289                                                        int *is_global)
290 {
291         return NULL;
292 }
293
294 /*
295  * remove_buf_file() default callback.  Does nothing.
296  */
297 static int remove_buf_file_default_callback(struct dentry *dentry)
298 {
299         return -EINVAL;
300 }
301
302 /* relay channel default callbacks */
303 static struct rchan_callbacks default_channel_callbacks = {
304         .subbuf_start = subbuf_start_default_callback,
305         .buf_mapped = buf_mapped_default_callback,
306         .buf_unmapped = buf_unmapped_default_callback,
307         .create_buf_file = create_buf_file_default_callback,
308         .remove_buf_file = remove_buf_file_default_callback,
309 };
310
311 /**
312  *      wakeup_readers - wake up readers waiting on a channel
313  *      @data: contains the the channel buffer
314  *
315  *      This is the timer function used to defer reader waking.
316  */
317 static void wakeup_readers(unsigned long data)
318 {
319         struct rchan_buf *buf = (struct rchan_buf *)data;
320         wake_up_interruptible(&buf->read_wait);
321 }
322
323 /**
324  *      __relay_reset - reset a channel buffer
325  *      @buf: the channel buffer
326  *      @init: 1 if this is a first-time initialization
327  *
328  *      See relay_reset() for description of effect.
329  */
330 static void __relay_reset(struct rchan_buf *buf, unsigned int init)
331 {
332         size_t i;
333
334         if (init) {
335                 init_waitqueue_head(&buf->read_wait);
336                 kref_init(&buf->kref);
337                 setup_timer(&buf->timer, wakeup_readers, (unsigned long)buf);
338         } else
339                 del_timer_sync(&buf->timer);
340
341         buf->subbufs_produced = 0;
342         buf->subbufs_consumed = 0;
343         buf->bytes_consumed = 0;
344         buf->finalized = 0;
345         buf->data = buf->start;
346         buf->offset = 0;
347
348         for (i = 0; i < buf->chan->n_subbufs; i++)
349                 buf->padding[i] = 0;
350
351         buf->chan->cb->subbuf_start(buf, buf->data, NULL, 0);
352 }
353
354 /**
355  *      relay_reset - reset the channel
356  *      @chan: the channel
357  *
358  *      This has the effect of erasing all data from all channel buffers
359  *      and restarting the channel in its initial state.  The buffers
360  *      are not freed, so any mappings are still in effect.
361  *
362  *      NOTE. Care should be taken that the channel isn't actually
363  *      being used by anything when this call is made.
364  */
365 void relay_reset(struct rchan *chan)
366 {
367         unsigned int i;
368
369         if (!chan)
370                 return;
371
372         if (chan->is_global && chan->buf[0]) {
373                 __relay_reset(chan->buf[0], 0);
374                 return;
375         }
376
377         mutex_lock(&relay_channels_mutex);
378         for_each_online_cpu(i)
379                 if (chan->buf[i])
380                         __relay_reset(chan->buf[i], 0);
381         mutex_unlock(&relay_channels_mutex);
382 }
383 EXPORT_SYMBOL_GPL(relay_reset);
384
385 /*
386  *      relay_open_buf - create a new relay channel buffer
387  *
388  *      used by relay_open() and CPU hotplug.
389  */
390 static struct rchan_buf *relay_open_buf(struct rchan *chan, unsigned int cpu)
391 {
392         struct rchan_buf *buf = NULL;
393         struct dentry *dentry;
394         char *tmpname;
395
396         if (chan->is_global)
397                 return chan->buf[0];
398
399         tmpname = kzalloc(NAME_MAX + 1, GFP_KERNEL);
400         if (!tmpname)
401                 goto end;
402         snprintf(tmpname, NAME_MAX, "%s%d", chan->base_filename, cpu);
403
404         buf = relay_create_buf(chan);
405         if (!buf)
406                 goto free_name;
407
408         buf->cpu = cpu;
409         __relay_reset(buf, 1);
410
411         /* Create file in fs */
412         dentry = chan->cb->create_buf_file(tmpname, chan->parent, S_IRUSR,
413                                            buf, &chan->is_global);
414         if (!dentry)
415                 goto free_buf;
416
417         buf->dentry = dentry;
418
419         if(chan->is_global) {
420                 chan->buf[0] = buf;
421                 buf->cpu = 0;
422         }
423
424         goto free_name;
425
426 free_buf:
427         relay_destroy_buf(buf);
428 free_name:
429         kfree(tmpname);
430 end:
431         return buf;
432 }
433
434 /**
435  *      relay_close_buf - close a channel buffer
436  *      @buf: channel buffer
437  *
438  *      Marks the buffer finalized and restores the default callbacks.
439  *      The channel buffer and channel buffer data structure are then freed
440  *      automatically when the last reference is given up.
441  */
442 static void relay_close_buf(struct rchan_buf *buf)
443 {
444         buf->finalized = 1;
445         del_timer_sync(&buf->timer);
446         kref_put(&buf->kref, relay_remove_buf);
447 }
448
449 static void setup_callbacks(struct rchan *chan,
450                                    struct rchan_callbacks *cb)
451 {
452         if (!cb) {
453                 chan->cb = &default_channel_callbacks;
454                 return;
455         }
456
457         if (!cb->subbuf_start)
458                 cb->subbuf_start = subbuf_start_default_callback;
459         if (!cb->buf_mapped)
460                 cb->buf_mapped = buf_mapped_default_callback;
461         if (!cb->buf_unmapped)
462                 cb->buf_unmapped = buf_unmapped_default_callback;
463         if (!cb->create_buf_file)
464                 cb->create_buf_file = create_buf_file_default_callback;
465         if (!cb->remove_buf_file)
466                 cb->remove_buf_file = remove_buf_file_default_callback;
467         chan->cb = cb;
468 }
469
470 /**
471  *      relay_hotcpu_callback - CPU hotplug callback
472  *      @nb: notifier block
473  *      @action: hotplug action to take
474  *      @hcpu: CPU number
475  *
476  *      Returns the success/failure of the operation. (%NOTIFY_OK, %NOTIFY_BAD)
477  */
478 static int __cpuinit relay_hotcpu_callback(struct notifier_block *nb,
479                                 unsigned long action,
480                                 void *hcpu)
481 {
482         unsigned int hotcpu = (unsigned long)hcpu;
483         struct rchan *chan;
484
485         switch(action) {
486         case CPU_UP_PREPARE:
487                 mutex_lock(&relay_channels_mutex);
488                 list_for_each_entry(chan, &relay_channels, list) {
489                         if (chan->buf[hotcpu])
490                                 continue;
491                         chan->buf[hotcpu] = relay_open_buf(chan, hotcpu);
492                         if(!chan->buf[hotcpu]) {
493                                 printk(KERN_ERR
494                                         "relay_hotcpu_callback: cpu %d buffer "
495                                         "creation failed\n", hotcpu);
496                                 mutex_unlock(&relay_channels_mutex);
497                                 return NOTIFY_BAD;
498                         }
499                 }
500                 mutex_unlock(&relay_channels_mutex);
501                 break;
502         case CPU_DEAD:
503                 /* No need to flush the cpu : will be flushed upon
504                  * final relay_flush() call. */
505                 break;
506         }
507         return NOTIFY_OK;
508 }
509
510 /**
511  *      relay_open - create a new relay channel
512  *      @base_filename: base name of files to create
513  *      @parent: dentry of parent directory, %NULL for root directory
514  *      @subbuf_size: size of sub-buffers
515  *      @n_subbufs: number of sub-buffers
516  *      @cb: client callback functions
517  *      @private_data: user-defined data
518  *
519  *      Returns channel pointer if successful, %NULL otherwise.
520  *
521  *      Creates a channel buffer for each cpu using the sizes and
522  *      attributes specified.  The created channel buffer files
523  *      will be named base_filename0...base_filenameN-1.  File
524  *      permissions will be %S_IRUSR.
525  */
526 struct rchan *relay_open(const char *base_filename,
527                          struct dentry *parent,
528                          size_t subbuf_size,
529                          size_t n_subbufs,
530                          struct rchan_callbacks *cb,
531                          void *private_data)
532 {
533         unsigned int i;
534         struct rchan *chan;
535         if (!base_filename)
536                 return NULL;
537
538         if (!(subbuf_size && n_subbufs))
539                 return NULL;
540
541         chan = kzalloc(sizeof(struct rchan), GFP_KERNEL);
542         if (!chan)
543                 return NULL;
544
545         chan->version = RELAYFS_CHANNEL_VERSION;
546         chan->n_subbufs = n_subbufs;
547         chan->subbuf_size = subbuf_size;
548         chan->alloc_size = FIX_SIZE(subbuf_size * n_subbufs);
549         chan->parent = parent;
550         chan->private_data = private_data;
551         strlcpy(chan->base_filename, base_filename, NAME_MAX);
552         setup_callbacks(chan, cb);
553         kref_init(&chan->kref);
554
555         mutex_lock(&relay_channels_mutex);
556         for_each_online_cpu(i) {
557                 chan->buf[i] = relay_open_buf(chan, i);
558                 if (!chan->buf[i])
559                         goto free_bufs;
560         }
561         list_add(&chan->list, &relay_channels);
562         mutex_unlock(&relay_channels_mutex);
563
564         return chan;
565
566 free_bufs:
567         for_each_online_cpu(i) {
568                 if (!chan->buf[i])
569                         break;
570                 relay_close_buf(chan->buf[i]);
571         }
572
573         kref_put(&chan->kref, relay_destroy_channel);
574         mutex_unlock(&relay_channels_mutex);
575         return NULL;
576 }
577 EXPORT_SYMBOL_GPL(relay_open);
578
579 /**
580  *      relay_switch_subbuf - switch to a new sub-buffer
581  *      @buf: channel buffer
582  *      @length: size of current event
583  *
584  *      Returns either the length passed in or 0 if full.
585  *
586  *      Performs sub-buffer-switch tasks such as invoking callbacks,
587  *      updating padding counts, waking up readers, etc.
588  */
589 size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length)
590 {
591         void *old, *new;
592         size_t old_subbuf, new_subbuf;
593
594         if (unlikely(length > buf->chan->subbuf_size))
595                 goto toobig;
596
597         if (buf->offset != buf->chan->subbuf_size + 1) {
598                 buf->prev_padding = buf->chan->subbuf_size - buf->offset;
599                 old_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
600                 buf->padding[old_subbuf] = buf->prev_padding;
601                 buf->subbufs_produced++;
602                 buf->dentry->d_inode->i_size += buf->chan->subbuf_size -
603                         buf->padding[old_subbuf];
604                 smp_mb();
605                 if (waitqueue_active(&buf->read_wait))
606                         /*
607                          * Calling wake_up_interruptible() from here
608                          * will deadlock if we happen to be logging
609                          * from the scheduler (trying to re-grab
610                          * rq->lock), so defer it.
611                          */
612                         __mod_timer(&buf->timer, jiffies + 1);
613         }
614
615         old = buf->data;
616         new_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
617         new = buf->start + new_subbuf * buf->chan->subbuf_size;
618         buf->offset = 0;
619         if (!buf->chan->cb->subbuf_start(buf, new, old, buf->prev_padding)) {
620                 buf->offset = buf->chan->subbuf_size + 1;
621                 return 0;
622         }
623         buf->data = new;
624         buf->padding[new_subbuf] = 0;
625
626         if (unlikely(length + buf->offset > buf->chan->subbuf_size))
627                 goto toobig;
628
629         return length;
630
631 toobig:
632         buf->chan->last_toobig = length;
633         return 0;
634 }
635 EXPORT_SYMBOL_GPL(relay_switch_subbuf);
636
637 /**
638  *      relay_subbufs_consumed - update the buffer's sub-buffers-consumed count
639  *      @chan: the channel
640  *      @cpu: the cpu associated with the channel buffer to update
641  *      @subbufs_consumed: number of sub-buffers to add to current buf's count
642  *
643  *      Adds to the channel buffer's consumed sub-buffer count.
644  *      subbufs_consumed should be the number of sub-buffers newly consumed,
645  *      not the total consumed.
646  *
647  *      NOTE. Kernel clients don't need to call this function if the channel
648  *      mode is 'overwrite'.
649  */
650 void relay_subbufs_consumed(struct rchan *chan,
651                             unsigned int cpu,
652                             size_t subbufs_consumed)
653 {
654         struct rchan_buf *buf;
655
656         if (!chan)
657                 return;
658
659         if (cpu >= NR_CPUS || !chan->buf[cpu])
660                 return;
661
662         buf = chan->buf[cpu];
663         buf->subbufs_consumed += subbufs_consumed;
664         if (buf->subbufs_consumed > buf->subbufs_produced)
665                 buf->subbufs_consumed = buf->subbufs_produced;
666 }
667 EXPORT_SYMBOL_GPL(relay_subbufs_consumed);
668
669 /**
670  *      relay_close - close the channel
671  *      @chan: the channel
672  *
673  *      Closes all channel buffers and frees the channel.
674  */
675 void relay_close(struct rchan *chan)
676 {
677         unsigned int i;
678
679         if (!chan)
680                 return;
681
682         mutex_lock(&relay_channels_mutex);
683         if (chan->is_global && chan->buf[0])
684                 relay_close_buf(chan->buf[0]);
685         else
686                 for_each_possible_cpu(i)
687                         if (chan->buf[i])
688                                 relay_close_buf(chan->buf[i]);
689
690         if (chan->last_toobig)
691                 printk(KERN_WARNING "relay: one or more items not logged "
692                        "[item size (%Zd) > sub-buffer size (%Zd)]\n",
693                        chan->last_toobig, chan->subbuf_size);
694
695         list_del(&chan->list);
696         kref_put(&chan->kref, relay_destroy_channel);
697         mutex_unlock(&relay_channels_mutex);
698 }
699 EXPORT_SYMBOL_GPL(relay_close);
700
701 /**
702  *      relay_flush - close the channel
703  *      @chan: the channel
704  *
705  *      Flushes all channel buffers, i.e. forces buffer switch.
706  */
707 void relay_flush(struct rchan *chan)
708 {
709         unsigned int i;
710
711         if (!chan)
712                 return;
713
714         if (chan->is_global && chan->buf[0]) {
715                 relay_switch_subbuf(chan->buf[0], 0);
716                 return;
717         }
718
719         mutex_lock(&relay_channels_mutex);
720         for_each_possible_cpu(i)
721                 if (chan->buf[i])
722                         relay_switch_subbuf(chan->buf[i], 0);
723         mutex_unlock(&relay_channels_mutex);
724 }
725 EXPORT_SYMBOL_GPL(relay_flush);
726
727 /**
728  *      relay_file_open - open file op for relay files
729  *      @inode: the inode
730  *      @filp: the file
731  *
732  *      Increments the channel buffer refcount.
733  */
734 static int relay_file_open(struct inode *inode, struct file *filp)
735 {
736         struct rchan_buf *buf = inode->i_private;
737         kref_get(&buf->kref);
738         filp->private_data = buf;
739
740         return 0;
741 }
742
743 /**
744  *      relay_file_mmap - mmap file op for relay files
745  *      @filp: the file
746  *      @vma: the vma describing what to map
747  *
748  *      Calls upon relay_mmap_buf() to map the file into user space.
749  */
750 static int relay_file_mmap(struct file *filp, struct vm_area_struct *vma)
751 {
752         struct rchan_buf *buf = filp->private_data;
753         return relay_mmap_buf(buf, vma);
754 }
755
756 /**
757  *      relay_file_poll - poll file op for relay files
758  *      @filp: the file
759  *      @wait: poll table
760  *
761  *      Poll implemention.
762  */
763 static unsigned int relay_file_poll(struct file *filp, poll_table *wait)
764 {
765         unsigned int mask = 0;
766         struct rchan_buf *buf = filp->private_data;
767
768         if (buf->finalized)
769                 return POLLERR;
770
771         if (filp->f_mode & FMODE_READ) {
772                 poll_wait(filp, &buf->read_wait, wait);
773                 if (!relay_buf_empty(buf))
774                         mask |= POLLIN | POLLRDNORM;
775         }
776
777         return mask;
778 }
779
780 /**
781  *      relay_file_release - release file op for relay files
782  *      @inode: the inode
783  *      @filp: the file
784  *
785  *      Decrements the channel refcount, as the filesystem is
786  *      no longer using it.
787  */
788 static int relay_file_release(struct inode *inode, struct file *filp)
789 {
790         struct rchan_buf *buf = filp->private_data;
791         kref_put(&buf->kref, relay_remove_buf);
792
793         return 0;
794 }
795
796 /*
797  *      relay_file_read_consume - update the consumed count for the buffer
798  */
799 static void relay_file_read_consume(struct rchan_buf *buf,
800                                     size_t read_pos,
801                                     size_t bytes_consumed)
802 {
803         size_t subbuf_size = buf->chan->subbuf_size;
804         size_t n_subbufs = buf->chan->n_subbufs;
805         size_t read_subbuf;
806
807         if (buf->bytes_consumed + bytes_consumed > subbuf_size) {
808                 relay_subbufs_consumed(buf->chan, buf->cpu, 1);
809                 buf->bytes_consumed = 0;
810         }
811
812         buf->bytes_consumed += bytes_consumed;
813         read_subbuf = read_pos / buf->chan->subbuf_size;
814         if (buf->bytes_consumed + buf->padding[read_subbuf] == subbuf_size) {
815                 if ((read_subbuf == buf->subbufs_produced % n_subbufs) &&
816                     (buf->offset == subbuf_size))
817                         return;
818                 relay_subbufs_consumed(buf->chan, buf->cpu, 1);
819                 buf->bytes_consumed = 0;
820         }
821 }
822
823 /*
824  *      relay_file_read_avail - boolean, are there unconsumed bytes available?
825  */
826 static int relay_file_read_avail(struct rchan_buf *buf, size_t read_pos)
827 {
828         size_t subbuf_size = buf->chan->subbuf_size;
829         size_t n_subbufs = buf->chan->n_subbufs;
830         size_t produced = buf->subbufs_produced;
831         size_t consumed = buf->subbufs_consumed;
832
833         relay_file_read_consume(buf, read_pos, 0);
834
835         if (unlikely(buf->offset > subbuf_size)) {
836                 if (produced == consumed)
837                         return 0;
838                 return 1;
839         }
840
841         if (unlikely(produced - consumed >= n_subbufs)) {
842                 consumed = (produced / n_subbufs) * n_subbufs;
843                 buf->subbufs_consumed = consumed;
844         }
845         
846         produced = (produced % n_subbufs) * subbuf_size + buf->offset;
847         consumed = (consumed % n_subbufs) * subbuf_size + buf->bytes_consumed;
848
849         if (consumed > produced)
850                 produced += n_subbufs * subbuf_size;
851         
852         if (consumed == produced)
853                 return 0;
854
855         return 1;
856 }
857
858 /**
859  *      relay_file_read_subbuf_avail - return bytes available in sub-buffer
860  *      @read_pos: file read position
861  *      @buf: relay channel buffer
862  */
863 static size_t relay_file_read_subbuf_avail(size_t read_pos,
864                                            struct rchan_buf *buf)
865 {
866         size_t padding, avail = 0;
867         size_t read_subbuf, read_offset, write_subbuf, write_offset;
868         size_t subbuf_size = buf->chan->subbuf_size;
869
870         write_subbuf = (buf->data - buf->start) / subbuf_size;
871         write_offset = buf->offset > subbuf_size ? subbuf_size : buf->offset;
872         read_subbuf = read_pos / subbuf_size;
873         read_offset = read_pos % subbuf_size;
874         padding = buf->padding[read_subbuf];
875
876         if (read_subbuf == write_subbuf) {
877                 if (read_offset + padding < write_offset)
878                         avail = write_offset - (read_offset + padding);
879         } else
880                 avail = (subbuf_size - padding) - read_offset;
881
882         return avail;
883 }
884
885 /**
886  *      relay_file_read_start_pos - find the first available byte to read
887  *      @read_pos: file read position
888  *      @buf: relay channel buffer
889  *
890  *      If the @read_pos is in the middle of padding, return the
891  *      position of the first actually available byte, otherwise
892  *      return the original value.
893  */
894 static size_t relay_file_read_start_pos(size_t read_pos,
895                                         struct rchan_buf *buf)
896 {
897         size_t read_subbuf, padding, padding_start, padding_end;
898         size_t subbuf_size = buf->chan->subbuf_size;
899         size_t n_subbufs = buf->chan->n_subbufs;
900
901         read_subbuf = read_pos / subbuf_size;
902         padding = buf->padding[read_subbuf];
903         padding_start = (read_subbuf + 1) * subbuf_size - padding;
904         padding_end = (read_subbuf + 1) * subbuf_size;
905         if (read_pos >= padding_start && read_pos < padding_end) {
906                 read_subbuf = (read_subbuf + 1) % n_subbufs;
907                 read_pos = read_subbuf * subbuf_size;
908         }
909
910         return read_pos;
911 }
912
913 /**
914  *      relay_file_read_end_pos - return the new read position
915  *      @read_pos: file read position
916  *      @buf: relay channel buffer
917  *      @count: number of bytes to be read
918  */
919 static size_t relay_file_read_end_pos(struct rchan_buf *buf,
920                                       size_t read_pos,
921                                       size_t count)
922 {
923         size_t read_subbuf, padding, end_pos;
924         size_t subbuf_size = buf->chan->subbuf_size;
925         size_t n_subbufs = buf->chan->n_subbufs;
926
927         read_subbuf = read_pos / subbuf_size;
928         padding = buf->padding[read_subbuf];
929         if (read_pos % subbuf_size + count + padding == subbuf_size)
930                 end_pos = (read_subbuf + 1) * subbuf_size;
931         else
932                 end_pos = read_pos + count;
933         if (end_pos >= subbuf_size * n_subbufs)
934                 end_pos = 0;
935
936         return end_pos;
937 }
938
939 /*
940  *      subbuf_read_actor - read up to one subbuf's worth of data
941  */
942 static int subbuf_read_actor(size_t read_start,
943                              struct rchan_buf *buf,
944                              size_t avail,
945                              read_descriptor_t *desc,
946                              read_actor_t actor)
947 {
948         void *from;
949         int ret = 0;
950
951         from = buf->start + read_start;
952         ret = avail;
953         if (copy_to_user(desc->arg.buf, from, avail)) {
954                 desc->error = -EFAULT;
955                 ret = 0;
956         }
957         desc->arg.data += ret;
958         desc->written += ret;
959         desc->count -= ret;
960
961         return ret;
962 }
963
964 /*
965  *      subbuf_send_actor - send up to one subbuf's worth of data
966  */
967 static int subbuf_send_actor(size_t read_start,
968                              struct rchan_buf *buf,
969                              size_t avail,
970                              read_descriptor_t *desc,
971                              read_actor_t actor)
972 {
973         unsigned long pidx, poff;
974         unsigned int subbuf_pages;
975         int ret = 0;
976
977         subbuf_pages = buf->chan->alloc_size >> PAGE_SHIFT;
978         pidx = (read_start / PAGE_SIZE) % subbuf_pages;
979         poff = read_start & ~PAGE_MASK;
980         while (avail) {
981                 struct page *p = buf->page_array[pidx];
982                 unsigned int len;
983
984                 len = PAGE_SIZE - poff;
985                 if (len > avail)
986                         len = avail;
987
988                 len = actor(desc, p, poff, len);
989                 if (desc->error)
990                         break;
991
992                 avail -= len;
993                 ret += len;
994                 poff = 0;
995                 pidx = (pidx + 1) % subbuf_pages;
996         }
997
998         return ret;
999 }
1000
1001 typedef int (*subbuf_actor_t) (size_t read_start,
1002                                struct rchan_buf *buf,
1003                                size_t avail,
1004                                read_descriptor_t *desc,
1005                                read_actor_t actor);
1006
1007 /*
1008  *      relay_file_read_subbufs - read count bytes, bridging subbuf boundaries
1009  */
1010 static ssize_t relay_file_read_subbufs(struct file *filp, loff_t *ppos,
1011                                         subbuf_actor_t subbuf_actor,
1012                                         read_actor_t actor,
1013                                         read_descriptor_t *desc)
1014 {
1015         struct rchan_buf *buf = filp->private_data;
1016         size_t read_start, avail;
1017         int ret;
1018
1019         if (!desc->count)
1020                 return 0;
1021
1022         mutex_lock(&filp->f_path.dentry->d_inode->i_mutex);
1023         do {
1024                 if (!relay_file_read_avail(buf, *ppos))
1025                         break;
1026
1027                 read_start = relay_file_read_start_pos(*ppos, buf);
1028                 avail = relay_file_read_subbuf_avail(read_start, buf);
1029                 if (!avail)
1030                         break;
1031
1032                 avail = min(desc->count, avail);
1033                 ret = subbuf_actor(read_start, buf, avail, desc, actor);
1034                 if (desc->error < 0)
1035                         break;
1036
1037                 if (ret) {
1038                         relay_file_read_consume(buf, read_start, ret);
1039                         *ppos = relay_file_read_end_pos(buf, read_start, ret);
1040                 }
1041         } while (desc->count && ret);
1042         mutex_unlock(&filp->f_path.dentry->d_inode->i_mutex);
1043
1044         return desc->written;
1045 }
1046
1047 static ssize_t relay_file_read(struct file *filp,
1048                                char __user *buffer,
1049                                size_t count,
1050                                loff_t *ppos)
1051 {
1052         read_descriptor_t desc;
1053         desc.written = 0;
1054         desc.count = count;
1055         desc.arg.buf = buffer;
1056         desc.error = 0;
1057         return relay_file_read_subbufs(filp, ppos, subbuf_read_actor,
1058                                        NULL, &desc);
1059 }
1060
1061 static ssize_t relay_file_sendfile(struct file *filp,
1062                                    loff_t *ppos,
1063                                    size_t count,
1064                                    read_actor_t actor,
1065                                    void *target)
1066 {
1067         read_descriptor_t desc;
1068         desc.written = 0;
1069         desc.count = count;
1070         desc.arg.data = target;
1071         desc.error = 0;
1072         return relay_file_read_subbufs(filp, ppos, subbuf_send_actor,
1073                                        actor, &desc);
1074 }
1075
1076 const struct file_operations relay_file_operations = {
1077         .open           = relay_file_open,
1078         .poll           = relay_file_poll,
1079         .mmap           = relay_file_mmap,
1080         .read           = relay_file_read,
1081         .llseek         = no_llseek,
1082         .release        = relay_file_release,
1083         .sendfile       = relay_file_sendfile,
1084 };
1085 EXPORT_SYMBOL_GPL(relay_file_operations);
1086
1087 static __init int relay_init(void)
1088 {
1089
1090         hotcpu_notifier(relay_hotcpu_callback, 0);
1091         return 0;
1092 }
1093
1094 module_init(relay_init);