Revert "relay: fix splice problem"
[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/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 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         struct page **array;
74         size_t pa_size = n_pages * sizeof(struct page *);
75
76         if (pa_size > PAGE_SIZE) {
77                 array = vmalloc(pa_size);
78                 if (array)
79                         memset(array, 0, pa_size);
80         } else {
81                 array = kzalloc(pa_size, GFP_KERNEL);
82         }
83         return array;
84 }
85
86 /*
87  * free an array of pointers of struct page
88  */
89 static void relay_free_page_array(struct page **array)
90 {
91         if (is_vmalloc_addr(array))
92                 vfree(array);
93         else
94                 kfree(array);
95 }
96
97 /**
98  *      relay_mmap_buf: - mmap channel buffer to process address space
99  *      @buf: relay channel buffer
100  *      @vma: vm_area_struct describing memory to be mapped
101  *
102  *      Returns 0 if ok, negative on error
103  *
104  *      Caller should already have grabbed mmap_sem.
105  */
106 static int relay_mmap_buf(struct rchan_buf *buf, struct vm_area_struct *vma)
107 {
108         unsigned long length = vma->vm_end - vma->vm_start;
109         struct file *filp = vma->vm_file;
110
111         if (!buf)
112                 return -EBADF;
113
114         if (length != (unsigned long)buf->chan->alloc_size)
115                 return -EINVAL;
116
117         vma->vm_ops = &relay_file_mmap_ops;
118         vma->vm_flags |= VM_DONTEXPAND;
119         vma->vm_private_data = buf;
120         buf->chan->cb->buf_mapped(buf, filp);
121
122         return 0;
123 }
124
125 /**
126  *      relay_alloc_buf - allocate a channel buffer
127  *      @buf: the buffer struct
128  *      @size: total size of the buffer
129  *
130  *      Returns a pointer to the resulting buffer, %NULL if unsuccessful. The
131  *      passed in size will get page aligned, if it isn't already.
132  */
133 static void *relay_alloc_buf(struct rchan_buf *buf, size_t *size)
134 {
135         void *mem;
136         unsigned int i, j, n_pages;
137
138         *size = PAGE_ALIGN(*size);
139         n_pages = *size >> PAGE_SHIFT;
140
141         buf->page_array = relay_alloc_page_array(n_pages);
142         if (!buf->page_array)
143                 return NULL;
144
145         for (i = 0; i < n_pages; i++) {
146                 buf->page_array[i] = alloc_page(GFP_KERNEL);
147                 if (unlikely(!buf->page_array[i]))
148                         goto depopulate;
149                 set_page_private(buf->page_array[i], (unsigned long)buf);
150         }
151         mem = vmap(buf->page_array, n_pages, VM_MAP, PAGE_KERNEL);
152         if (!mem)
153                 goto depopulate;
154
155         memset(mem, 0, *size);
156         buf->page_count = n_pages;
157         return mem;
158
159 depopulate:
160         for (j = 0; j < i; j++)
161                 __free_page(buf->page_array[j]);
162         relay_free_page_array(buf->page_array);
163         return NULL;
164 }
165
166 /**
167  *      relay_create_buf - allocate and initialize a channel buffer
168  *      @chan: the relay channel
169  *
170  *      Returns channel buffer if successful, %NULL otherwise.
171  */
172 static struct rchan_buf *relay_create_buf(struct rchan *chan)
173 {
174         struct rchan_buf *buf = kzalloc(sizeof(struct rchan_buf), GFP_KERNEL);
175         if (!buf)
176                 return NULL;
177
178         buf->padding = kmalloc(chan->n_subbufs * sizeof(size_t *), GFP_KERNEL);
179         if (!buf->padding)
180                 goto free_buf;
181
182         buf->start = relay_alloc_buf(buf, &chan->alloc_size);
183         if (!buf->start)
184                 goto free_buf;
185
186         buf->chan = chan;
187         kref_get(&buf->chan->kref);
188         return buf;
189
190 free_buf:
191         kfree(buf->padding);
192         kfree(buf);
193         return NULL;
194 }
195
196 /**
197  *      relay_destroy_channel - free the channel struct
198  *      @kref: target kernel reference that contains the relay channel
199  *
200  *      Should only be called from kref_put().
201  */
202 static void relay_destroy_channel(struct kref *kref)
203 {
204         struct rchan *chan = container_of(kref, struct rchan, kref);
205         kfree(chan);
206 }
207
208 /**
209  *      relay_destroy_buf - destroy an rchan_buf struct and associated buffer
210  *      @buf: the buffer struct
211  */
212 static void relay_destroy_buf(struct rchan_buf *buf)
213 {
214         struct rchan *chan = buf->chan;
215         unsigned int i;
216
217         if (likely(buf->start)) {
218                 vunmap(buf->start);
219                 for (i = 0; i < buf->page_count; i++)
220                         __free_page(buf->page_array[i]);
221                 relay_free_page_array(buf->page_array);
222         }
223         chan->buf[buf->cpu] = NULL;
224         kfree(buf->padding);
225         kfree(buf);
226         kref_put(&chan->kref, relay_destroy_channel);
227 }
228
229 /**
230  *      relay_remove_buf - remove a channel buffer
231  *      @kref: target kernel reference that contains the relay buffer
232  *
233  *      Removes the file from the fileystem, which also frees the
234  *      rchan_buf_struct and the channel buffer.  Should only be called from
235  *      kref_put().
236  */
237 static void relay_remove_buf(struct kref *kref)
238 {
239         struct rchan_buf *buf = container_of(kref, struct rchan_buf, kref);
240         buf->chan->cb->remove_buf_file(buf->dentry);
241         relay_destroy_buf(buf);
242 }
243
244 /**
245  *      relay_buf_empty - boolean, is the channel buffer empty?
246  *      @buf: channel buffer
247  *
248  *      Returns 1 if the buffer is empty, 0 otherwise.
249  */
250 static int relay_buf_empty(struct rchan_buf *buf)
251 {
252         return (buf->subbufs_produced - buf->subbufs_consumed) ? 0 : 1;
253 }
254
255 /**
256  *      relay_buf_full - boolean, is the channel buffer full?
257  *      @buf: channel buffer
258  *
259  *      Returns 1 if the buffer is full, 0 otherwise.
260  */
261 int relay_buf_full(struct rchan_buf *buf)
262 {
263         size_t ready = buf->subbufs_produced - buf->subbufs_consumed;
264         return (ready >= buf->chan->n_subbufs) ? 1 : 0;
265 }
266 EXPORT_SYMBOL_GPL(relay_buf_full);
267
268 /*
269  * High-level relay kernel API and associated functions.
270  */
271
272 /*
273  * rchan_callback implementations defining default channel behavior.  Used
274  * in place of corresponding NULL values in client callback struct.
275  */
276
277 /*
278  * subbuf_start() default callback.  Does nothing.
279  */
280 static int subbuf_start_default_callback (struct rchan_buf *buf,
281                                           void *subbuf,
282                                           void *prev_subbuf,
283                                           size_t prev_padding)
284 {
285         if (relay_buf_full(buf))
286                 return 0;
287
288         return 1;
289 }
290
291 /*
292  * buf_mapped() default callback.  Does nothing.
293  */
294 static void buf_mapped_default_callback(struct rchan_buf *buf,
295                                         struct file *filp)
296 {
297 }
298
299 /*
300  * buf_unmapped() default callback.  Does nothing.
301  */
302 static void buf_unmapped_default_callback(struct rchan_buf *buf,
303                                           struct file *filp)
304 {
305 }
306
307 /*
308  * create_buf_file_create() default callback.  Does nothing.
309  */
310 static struct dentry *create_buf_file_default_callback(const char *filename,
311                                                        struct dentry *parent,
312                                                        int mode,
313                                                        struct rchan_buf *buf,
314                                                        int *is_global)
315 {
316         return NULL;
317 }
318
319 /*
320  * remove_buf_file() default callback.  Does nothing.
321  */
322 static int remove_buf_file_default_callback(struct dentry *dentry)
323 {
324         return -EINVAL;
325 }
326
327 /* relay channel default callbacks */
328 static struct rchan_callbacks default_channel_callbacks = {
329         .subbuf_start = subbuf_start_default_callback,
330         .buf_mapped = buf_mapped_default_callback,
331         .buf_unmapped = buf_unmapped_default_callback,
332         .create_buf_file = create_buf_file_default_callback,
333         .remove_buf_file = remove_buf_file_default_callback,
334 };
335
336 /**
337  *      wakeup_readers - wake up readers waiting on a channel
338  *      @data: contains the channel buffer
339  *
340  *      This is the timer function used to defer reader waking.
341  */
342 static void wakeup_readers(unsigned long data)
343 {
344         struct rchan_buf *buf = (struct rchan_buf *)data;
345         wake_up_interruptible(&buf->read_wait);
346 }
347
348 /**
349  *      __relay_reset - reset a channel buffer
350  *      @buf: the channel buffer
351  *      @init: 1 if this is a first-time initialization
352  *
353  *      See relay_reset() for description of effect.
354  */
355 static void __relay_reset(struct rchan_buf *buf, unsigned int init)
356 {
357         size_t i;
358
359         if (init) {
360                 init_waitqueue_head(&buf->read_wait);
361                 kref_init(&buf->kref);
362                 setup_timer(&buf->timer, wakeup_readers, (unsigned long)buf);
363         } else
364                 del_timer_sync(&buf->timer);
365
366         buf->subbufs_produced = 0;
367         buf->subbufs_consumed = 0;
368         buf->bytes_consumed = 0;
369         buf->finalized = 0;
370         buf->data = buf->start;
371         buf->offset = 0;
372
373         for (i = 0; i < buf->chan->n_subbufs; i++)
374                 buf->padding[i] = 0;
375
376         buf->chan->cb->subbuf_start(buf, buf->data, NULL, 0);
377 }
378
379 /**
380  *      relay_reset - reset the channel
381  *      @chan: the channel
382  *
383  *      This has the effect of erasing all data from all channel buffers
384  *      and restarting the channel in its initial state.  The buffers
385  *      are not freed, so any mappings are still in effect.
386  *
387  *      NOTE. Care should be taken that the channel isn't actually
388  *      being used by anything when this call is made.
389  */
390 void relay_reset(struct rchan *chan)
391 {
392         unsigned int i;
393
394         if (!chan)
395                 return;
396
397         if (chan->is_global && chan->buf[0]) {
398                 __relay_reset(chan->buf[0], 0);
399                 return;
400         }
401
402         mutex_lock(&relay_channels_mutex);
403         for_each_online_cpu(i)
404                 if (chan->buf[i])
405                         __relay_reset(chan->buf[i], 0);
406         mutex_unlock(&relay_channels_mutex);
407 }
408 EXPORT_SYMBOL_GPL(relay_reset);
409
410 /*
411  *      relay_open_buf - create a new relay channel buffer
412  *
413  *      used by relay_open() and CPU hotplug.
414  */
415 static struct rchan_buf *relay_open_buf(struct rchan *chan, unsigned int cpu)
416 {
417         struct rchan_buf *buf = NULL;
418         struct dentry *dentry;
419         char *tmpname;
420
421         if (chan->is_global)
422                 return chan->buf[0];
423
424         tmpname = kzalloc(NAME_MAX + 1, GFP_KERNEL);
425         if (!tmpname)
426                 goto end;
427         snprintf(tmpname, NAME_MAX, "%s%d", chan->base_filename, cpu);
428
429         buf = relay_create_buf(chan);
430         if (!buf)
431                 goto free_name;
432
433         buf->cpu = cpu;
434         __relay_reset(buf, 1);
435
436         /* Create file in fs */
437         dentry = chan->cb->create_buf_file(tmpname, chan->parent, S_IRUSR,
438                                            buf, &chan->is_global);
439         if (!dentry)
440                 goto free_buf;
441
442         buf->dentry = dentry;
443
444         if(chan->is_global) {
445                 chan->buf[0] = buf;
446                 buf->cpu = 0;
447         }
448
449         goto free_name;
450
451 free_buf:
452         relay_destroy_buf(buf);
453         buf = NULL;
454 free_name:
455         kfree(tmpname);
456 end:
457         return buf;
458 }
459
460 /**
461  *      relay_close_buf - close a channel buffer
462  *      @buf: channel buffer
463  *
464  *      Marks the buffer finalized and restores the default callbacks.
465  *      The channel buffer and channel buffer data structure are then freed
466  *      automatically when the last reference is given up.
467  */
468 static void relay_close_buf(struct rchan_buf *buf)
469 {
470         buf->finalized = 1;
471         del_timer_sync(&buf->timer);
472         kref_put(&buf->kref, relay_remove_buf);
473 }
474
475 static void setup_callbacks(struct rchan *chan,
476                                    struct rchan_callbacks *cb)
477 {
478         if (!cb) {
479                 chan->cb = &default_channel_callbacks;
480                 return;
481         }
482
483         if (!cb->subbuf_start)
484                 cb->subbuf_start = subbuf_start_default_callback;
485         if (!cb->buf_mapped)
486                 cb->buf_mapped = buf_mapped_default_callback;
487         if (!cb->buf_unmapped)
488                 cb->buf_unmapped = buf_unmapped_default_callback;
489         if (!cb->create_buf_file)
490                 cb->create_buf_file = create_buf_file_default_callback;
491         if (!cb->remove_buf_file)
492                 cb->remove_buf_file = remove_buf_file_default_callback;
493         chan->cb = cb;
494 }
495
496 /**
497  *      relay_hotcpu_callback - CPU hotplug callback
498  *      @nb: notifier block
499  *      @action: hotplug action to take
500  *      @hcpu: CPU number
501  *
502  *      Returns the success/failure of the operation. (%NOTIFY_OK, %NOTIFY_BAD)
503  */
504 static int __cpuinit relay_hotcpu_callback(struct notifier_block *nb,
505                                 unsigned long action,
506                                 void *hcpu)
507 {
508         unsigned int hotcpu = (unsigned long)hcpu;
509         struct rchan *chan;
510
511         switch(action) {
512         case CPU_UP_PREPARE:
513         case CPU_UP_PREPARE_FROZEN:
514                 mutex_lock(&relay_channels_mutex);
515                 list_for_each_entry(chan, &relay_channels, list) {
516                         if (chan->buf[hotcpu])
517                                 continue;
518                         chan->buf[hotcpu] = relay_open_buf(chan, hotcpu);
519                         if(!chan->buf[hotcpu]) {
520                                 printk(KERN_ERR
521                                         "relay_hotcpu_callback: cpu %d buffer "
522                                         "creation failed\n", hotcpu);
523                                 mutex_unlock(&relay_channels_mutex);
524                                 return NOTIFY_BAD;
525                         }
526                 }
527                 mutex_unlock(&relay_channels_mutex);
528                 break;
529         case CPU_DEAD:
530         case CPU_DEAD_FROZEN:
531                 /* No need to flush the cpu : will be flushed upon
532                  * final relay_flush() call. */
533                 break;
534         }
535         return NOTIFY_OK;
536 }
537
538 /**
539  *      relay_open - create a new relay channel
540  *      @base_filename: base name of files to create
541  *      @parent: dentry of parent directory, %NULL for root directory
542  *      @subbuf_size: size of sub-buffers
543  *      @n_subbufs: number of sub-buffers
544  *      @cb: client callback functions
545  *      @private_data: user-defined data
546  *
547  *      Returns channel pointer if successful, %NULL otherwise.
548  *
549  *      Creates a channel buffer for each cpu using the sizes and
550  *      attributes specified.  The created channel buffer files
551  *      will be named base_filename0...base_filenameN-1.  File
552  *      permissions will be %S_IRUSR.
553  */
554 struct rchan *relay_open(const char *base_filename,
555                          struct dentry *parent,
556                          size_t subbuf_size,
557                          size_t n_subbufs,
558                          struct rchan_callbacks *cb,
559                          void *private_data)
560 {
561         unsigned int i;
562         struct rchan *chan;
563         if (!base_filename)
564                 return NULL;
565
566         if (!(subbuf_size && n_subbufs))
567                 return NULL;
568
569         chan = kzalloc(sizeof(struct rchan), GFP_KERNEL);
570         if (!chan)
571                 return NULL;
572
573         chan->version = RELAYFS_CHANNEL_VERSION;
574         chan->n_subbufs = n_subbufs;
575         chan->subbuf_size = subbuf_size;
576         chan->alloc_size = FIX_SIZE(subbuf_size * n_subbufs);
577         chan->parent = parent;
578         chan->private_data = private_data;
579         strlcpy(chan->base_filename, base_filename, NAME_MAX);
580         setup_callbacks(chan, cb);
581         kref_init(&chan->kref);
582
583         mutex_lock(&relay_channels_mutex);
584         for_each_online_cpu(i) {
585                 chan->buf[i] = relay_open_buf(chan, i);
586                 if (!chan->buf[i])
587                         goto free_bufs;
588         }
589         list_add(&chan->list, &relay_channels);
590         mutex_unlock(&relay_channels_mutex);
591
592         return chan;
593
594 free_bufs:
595         for_each_online_cpu(i) {
596                 if (!chan->buf[i])
597                         break;
598                 relay_close_buf(chan->buf[i]);
599         }
600
601         kref_put(&chan->kref, relay_destroy_channel);
602         mutex_unlock(&relay_channels_mutex);
603         return NULL;
604 }
605 EXPORT_SYMBOL_GPL(relay_open);
606
607 /**
608  *      relay_switch_subbuf - switch to a new sub-buffer
609  *      @buf: channel buffer
610  *      @length: size of current event
611  *
612  *      Returns either the length passed in or 0 if full.
613  *
614  *      Performs sub-buffer-switch tasks such as invoking callbacks,
615  *      updating padding counts, waking up readers, etc.
616  */
617 size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length)
618 {
619         void *old, *new;
620         size_t old_subbuf, new_subbuf;
621
622         if (unlikely(length > buf->chan->subbuf_size))
623                 goto toobig;
624
625         if (buf->offset != buf->chan->subbuf_size + 1) {
626                 buf->prev_padding = buf->chan->subbuf_size - buf->offset;
627                 old_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
628                 buf->padding[old_subbuf] = buf->prev_padding;
629                 buf->subbufs_produced++;
630                 buf->dentry->d_inode->i_size += buf->chan->subbuf_size -
631                         buf->padding[old_subbuf];
632                 smp_mb();
633                 if (waitqueue_active(&buf->read_wait))
634                         /*
635                          * Calling wake_up_interruptible() from here
636                          * will deadlock if we happen to be logging
637                          * from the scheduler (trying to re-grab
638                          * rq->lock), so defer it.
639                          */
640                         __mod_timer(&buf->timer, jiffies + 1);
641         }
642
643         old = buf->data;
644         new_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
645         new = buf->start + new_subbuf * buf->chan->subbuf_size;
646         buf->offset = 0;
647         if (!buf->chan->cb->subbuf_start(buf, new, old, buf->prev_padding)) {
648                 buf->offset = buf->chan->subbuf_size + 1;
649                 return 0;
650         }
651         buf->data = new;
652         buf->padding[new_subbuf] = 0;
653
654         if (unlikely(length + buf->offset > buf->chan->subbuf_size))
655                 goto toobig;
656
657         return length;
658
659 toobig:
660         buf->chan->last_toobig = length;
661         return 0;
662 }
663 EXPORT_SYMBOL_GPL(relay_switch_subbuf);
664
665 /**
666  *      relay_subbufs_consumed - update the buffer's sub-buffers-consumed count
667  *      @chan: the channel
668  *      @cpu: the cpu associated with the channel buffer to update
669  *      @subbufs_consumed: number of sub-buffers to add to current buf's count
670  *
671  *      Adds to the channel buffer's consumed sub-buffer count.
672  *      subbufs_consumed should be the number of sub-buffers newly consumed,
673  *      not the total consumed.
674  *
675  *      NOTE. Kernel clients don't need to call this function if the channel
676  *      mode is 'overwrite'.
677  */
678 void relay_subbufs_consumed(struct rchan *chan,
679                             unsigned int cpu,
680                             size_t subbufs_consumed)
681 {
682         struct rchan_buf *buf;
683
684         if (!chan)
685                 return;
686
687         if (cpu >= NR_CPUS || !chan->buf[cpu])
688                 return;
689
690         buf = chan->buf[cpu];
691         buf->subbufs_consumed += subbufs_consumed;
692         if (buf->subbufs_consumed > buf->subbufs_produced)
693                 buf->subbufs_consumed = buf->subbufs_produced;
694 }
695 EXPORT_SYMBOL_GPL(relay_subbufs_consumed);
696
697 /**
698  *      relay_close - close the channel
699  *      @chan: the channel
700  *
701  *      Closes all channel buffers and frees the channel.
702  */
703 void relay_close(struct rchan *chan)
704 {
705         unsigned int i;
706
707         if (!chan)
708                 return;
709
710         mutex_lock(&relay_channels_mutex);
711         if (chan->is_global && chan->buf[0])
712                 relay_close_buf(chan->buf[0]);
713         else
714                 for_each_possible_cpu(i)
715                         if (chan->buf[i])
716                                 relay_close_buf(chan->buf[i]);
717
718         if (chan->last_toobig)
719                 printk(KERN_WARNING "relay: one or more items not logged "
720                        "[item size (%Zd) > sub-buffer size (%Zd)]\n",
721                        chan->last_toobig, chan->subbuf_size);
722
723         list_del(&chan->list);
724         kref_put(&chan->kref, relay_destroy_channel);
725         mutex_unlock(&relay_channels_mutex);
726 }
727 EXPORT_SYMBOL_GPL(relay_close);
728
729 /**
730  *      relay_flush - close the channel
731  *      @chan: the channel
732  *
733  *      Flushes all channel buffers, i.e. forces buffer switch.
734  */
735 void relay_flush(struct rchan *chan)
736 {
737         unsigned int i;
738
739         if (!chan)
740                 return;
741
742         if (chan->is_global && chan->buf[0]) {
743                 relay_switch_subbuf(chan->buf[0], 0);
744                 return;
745         }
746
747         mutex_lock(&relay_channels_mutex);
748         for_each_possible_cpu(i)
749                 if (chan->buf[i])
750                         relay_switch_subbuf(chan->buf[i], 0);
751         mutex_unlock(&relay_channels_mutex);
752 }
753 EXPORT_SYMBOL_GPL(relay_flush);
754
755 /**
756  *      relay_file_open - open file op for relay files
757  *      @inode: the inode
758  *      @filp: the file
759  *
760  *      Increments the channel buffer refcount.
761  */
762 static int relay_file_open(struct inode *inode, struct file *filp)
763 {
764         struct rchan_buf *buf = inode->i_private;
765         kref_get(&buf->kref);
766         filp->private_data = buf;
767
768         return nonseekable_open(inode, filp);
769 }
770
771 /**
772  *      relay_file_mmap - mmap file op for relay files
773  *      @filp: the file
774  *      @vma: the vma describing what to map
775  *
776  *      Calls upon relay_mmap_buf() to map the file into user space.
777  */
778 static int relay_file_mmap(struct file *filp, struct vm_area_struct *vma)
779 {
780         struct rchan_buf *buf = filp->private_data;
781         return relay_mmap_buf(buf, vma);
782 }
783
784 /**
785  *      relay_file_poll - poll file op for relay files
786  *      @filp: the file
787  *      @wait: poll table
788  *
789  *      Poll implemention.
790  */
791 static unsigned int relay_file_poll(struct file *filp, poll_table *wait)
792 {
793         unsigned int mask = 0;
794         struct rchan_buf *buf = filp->private_data;
795
796         if (buf->finalized)
797                 return POLLERR;
798
799         if (filp->f_mode & FMODE_READ) {
800                 poll_wait(filp, &buf->read_wait, wait);
801                 if (!relay_buf_empty(buf))
802                         mask |= POLLIN | POLLRDNORM;
803         }
804
805         return mask;
806 }
807
808 /**
809  *      relay_file_release - release file op for relay files
810  *      @inode: the inode
811  *      @filp: the file
812  *
813  *      Decrements the channel refcount, as the filesystem is
814  *      no longer using it.
815  */
816 static int relay_file_release(struct inode *inode, struct file *filp)
817 {
818         struct rchan_buf *buf = filp->private_data;
819         kref_put(&buf->kref, relay_remove_buf);
820
821         return 0;
822 }
823
824 /*
825  *      relay_file_read_consume - update the consumed count for the buffer
826  */
827 static void relay_file_read_consume(struct rchan_buf *buf,
828                                     size_t read_pos,
829                                     size_t bytes_consumed)
830 {
831         size_t subbuf_size = buf->chan->subbuf_size;
832         size_t n_subbufs = buf->chan->n_subbufs;
833         size_t read_subbuf;
834
835         if (buf->bytes_consumed + bytes_consumed > subbuf_size) {
836                 relay_subbufs_consumed(buf->chan, buf->cpu, 1);
837                 buf->bytes_consumed = 0;
838         }
839
840         buf->bytes_consumed += bytes_consumed;
841         if (!read_pos)
842                 read_subbuf = buf->subbufs_consumed % n_subbufs;
843         else
844                 read_subbuf = read_pos / buf->chan->subbuf_size;
845         if (buf->bytes_consumed + buf->padding[read_subbuf] == subbuf_size) {
846                 if ((read_subbuf == buf->subbufs_produced % n_subbufs) &&
847                     (buf->offset == subbuf_size))
848                         return;
849                 relay_subbufs_consumed(buf->chan, buf->cpu, 1);
850                 buf->bytes_consumed = 0;
851         }
852 }
853
854 /*
855  *      relay_file_read_avail - boolean, are there unconsumed bytes available?
856  */
857 static int relay_file_read_avail(struct rchan_buf *buf, size_t read_pos)
858 {
859         size_t subbuf_size = buf->chan->subbuf_size;
860         size_t n_subbufs = buf->chan->n_subbufs;
861         size_t produced = buf->subbufs_produced;
862         size_t consumed = buf->subbufs_consumed;
863
864         relay_file_read_consume(buf, read_pos, 0);
865
866         if (unlikely(buf->offset > subbuf_size)) {
867                 if (produced == consumed)
868                         return 0;
869                 return 1;
870         }
871
872         if (unlikely(produced - consumed >= n_subbufs)) {
873                 consumed = produced - n_subbufs + 1;
874                 buf->subbufs_consumed = consumed;
875                 buf->bytes_consumed = 0;
876         }
877
878         produced = (produced % n_subbufs) * subbuf_size + buf->offset;
879         consumed = (consumed % n_subbufs) * subbuf_size + buf->bytes_consumed;
880
881         if (consumed > produced)
882                 produced += n_subbufs * subbuf_size;
883
884         if (consumed == produced)
885                 return 0;
886
887         return 1;
888 }
889
890 /**
891  *      relay_file_read_subbuf_avail - return bytes available in sub-buffer
892  *      @read_pos: file read position
893  *      @buf: relay channel buffer
894  */
895 static size_t relay_file_read_subbuf_avail(size_t read_pos,
896                                            struct rchan_buf *buf)
897 {
898         size_t padding, avail = 0;
899         size_t read_subbuf, read_offset, write_subbuf, write_offset;
900         size_t subbuf_size = buf->chan->subbuf_size;
901
902         write_subbuf = (buf->data - buf->start) / subbuf_size;
903         write_offset = buf->offset > subbuf_size ? subbuf_size : buf->offset;
904         read_subbuf = read_pos / subbuf_size;
905         read_offset = read_pos % subbuf_size;
906         padding = buf->padding[read_subbuf];
907
908         if (read_subbuf == write_subbuf) {
909                 if (read_offset + padding < write_offset)
910                         avail = write_offset - (read_offset + padding);
911         } else
912                 avail = (subbuf_size - padding) - read_offset;
913
914         return avail;
915 }
916
917 /**
918  *      relay_file_read_start_pos - find the first available byte to read
919  *      @read_pos: file read position
920  *      @buf: relay channel buffer
921  *
922  *      If the @read_pos is in the middle of padding, return the
923  *      position of the first actually available byte, otherwise
924  *      return the original value.
925  */
926 static size_t relay_file_read_start_pos(size_t read_pos,
927                                         struct rchan_buf *buf)
928 {
929         size_t read_subbuf, padding, padding_start, padding_end;
930         size_t subbuf_size = buf->chan->subbuf_size;
931         size_t n_subbufs = buf->chan->n_subbufs;
932         size_t consumed = buf->subbufs_consumed % n_subbufs;
933
934         if (!read_pos)
935                 read_pos = consumed * subbuf_size + buf->bytes_consumed;
936         read_subbuf = read_pos / subbuf_size;
937         padding = buf->padding[read_subbuf];
938         padding_start = (read_subbuf + 1) * subbuf_size - padding;
939         padding_end = (read_subbuf + 1) * subbuf_size;
940         if (read_pos >= padding_start && read_pos < padding_end) {
941                 read_subbuf = (read_subbuf + 1) % n_subbufs;
942                 read_pos = read_subbuf * subbuf_size;
943         }
944
945         return read_pos;
946 }
947
948 /**
949  *      relay_file_read_end_pos - return the new read position
950  *      @read_pos: file read position
951  *      @buf: relay channel buffer
952  *      @count: number of bytes to be read
953  */
954 static size_t relay_file_read_end_pos(struct rchan_buf *buf,
955                                       size_t read_pos,
956                                       size_t count)
957 {
958         size_t read_subbuf, padding, end_pos;
959         size_t subbuf_size = buf->chan->subbuf_size;
960         size_t n_subbufs = buf->chan->n_subbufs;
961
962         read_subbuf = read_pos / subbuf_size;
963         padding = buf->padding[read_subbuf];
964         if (read_pos % subbuf_size + count + padding == subbuf_size)
965                 end_pos = (read_subbuf + 1) * subbuf_size;
966         else
967                 end_pos = read_pos + count;
968         if (end_pos >= subbuf_size * n_subbufs)
969                 end_pos = 0;
970
971         return end_pos;
972 }
973
974 /*
975  *      subbuf_read_actor - read up to one subbuf's worth of data
976  */
977 static int subbuf_read_actor(size_t read_start,
978                              struct rchan_buf *buf,
979                              size_t avail,
980                              read_descriptor_t *desc,
981                              read_actor_t actor)
982 {
983         void *from;
984         int ret = 0;
985
986         from = buf->start + read_start;
987         ret = avail;
988         if (copy_to_user(desc->arg.buf, from, avail)) {
989                 desc->error = -EFAULT;
990                 ret = 0;
991         }
992         desc->arg.data += ret;
993         desc->written += ret;
994         desc->count -= ret;
995
996         return ret;
997 }
998
999 typedef int (*subbuf_actor_t) (size_t read_start,
1000                                struct rchan_buf *buf,
1001                                size_t avail,
1002                                read_descriptor_t *desc,
1003                                read_actor_t actor);
1004
1005 /*
1006  *      relay_file_read_subbufs - read count bytes, bridging subbuf boundaries
1007  */
1008 static ssize_t relay_file_read_subbufs(struct file *filp, loff_t *ppos,
1009                                         subbuf_actor_t subbuf_actor,
1010                                         read_actor_t actor,
1011                                         read_descriptor_t *desc)
1012 {
1013         struct rchan_buf *buf = filp->private_data;
1014         size_t read_start, avail;
1015         int ret;
1016
1017         if (!desc->count)
1018                 return 0;
1019
1020         mutex_lock(&filp->f_path.dentry->d_inode->i_mutex);
1021         do {
1022                 if (!relay_file_read_avail(buf, *ppos))
1023                         break;
1024
1025                 read_start = relay_file_read_start_pos(*ppos, buf);
1026                 avail = relay_file_read_subbuf_avail(read_start, buf);
1027                 if (!avail)
1028                         break;
1029
1030                 avail = min(desc->count, avail);
1031                 ret = subbuf_actor(read_start, buf, avail, desc, actor);
1032                 if (desc->error < 0)
1033                         break;
1034
1035                 if (ret) {
1036                         relay_file_read_consume(buf, read_start, ret);
1037                         *ppos = relay_file_read_end_pos(buf, read_start, ret);
1038                 }
1039         } while (desc->count && ret);
1040         mutex_unlock(&filp->f_path.dentry->d_inode->i_mutex);
1041
1042         return desc->written;
1043 }
1044
1045 static ssize_t relay_file_read(struct file *filp,
1046                                char __user *buffer,
1047                                size_t count,
1048                                loff_t *ppos)
1049 {
1050         read_descriptor_t desc;
1051         desc.written = 0;
1052         desc.count = count;
1053         desc.arg.buf = buffer;
1054         desc.error = 0;
1055         return relay_file_read_subbufs(filp, ppos, subbuf_read_actor,
1056                                        NULL, &desc);
1057 }
1058
1059 static void relay_consume_bytes(struct rchan_buf *rbuf, int bytes_consumed)
1060 {
1061         rbuf->bytes_consumed += bytes_consumed;
1062
1063         if (rbuf->bytes_consumed >= rbuf->chan->subbuf_size) {
1064                 relay_subbufs_consumed(rbuf->chan, rbuf->cpu, 1);
1065                 rbuf->bytes_consumed %= rbuf->chan->subbuf_size;
1066         }
1067 }
1068
1069 static void relay_pipe_buf_release(struct pipe_inode_info *pipe,
1070                                    struct pipe_buffer *buf)
1071 {
1072         struct rchan_buf *rbuf;
1073
1074         rbuf = (struct rchan_buf *)page_private(buf->page);
1075         relay_consume_bytes(rbuf, buf->private);
1076 }
1077
1078 static struct pipe_buf_operations relay_pipe_buf_ops = {
1079         .can_merge = 0,
1080         .map = generic_pipe_buf_map,
1081         .unmap = generic_pipe_buf_unmap,
1082         .confirm = generic_pipe_buf_confirm,
1083         .release = relay_pipe_buf_release,
1084         .steal = generic_pipe_buf_steal,
1085         .get = generic_pipe_buf_get,
1086 };
1087
1088 static void relay_page_release(struct splice_pipe_desc *spd, unsigned int i)
1089 {
1090 }
1091
1092 /*
1093  *      subbuf_splice_actor - splice up to one subbuf's worth of data
1094  */
1095 static int subbuf_splice_actor(struct file *in,
1096                                loff_t *ppos,
1097                                struct pipe_inode_info *pipe,
1098                                size_t len,
1099                                unsigned int flags,
1100                                int *nonpad_ret)
1101 {
1102         unsigned int pidx, poff, total_len, subbuf_pages, nr_pages, ret;
1103         struct rchan_buf *rbuf = in->private_data;
1104         unsigned int subbuf_size = rbuf->chan->subbuf_size;
1105         uint64_t pos = (uint64_t) *ppos;
1106         uint32_t alloc_size = (uint32_t) rbuf->chan->alloc_size;
1107         size_t read_start = (size_t) do_div(pos, alloc_size);
1108         size_t read_subbuf = read_start / subbuf_size;
1109         size_t padding = rbuf->padding[read_subbuf];
1110         size_t nonpad_end = read_subbuf * subbuf_size + subbuf_size - padding;
1111         struct page *pages[PIPE_BUFFERS];
1112         struct partial_page partial[PIPE_BUFFERS];
1113         struct splice_pipe_desc spd = {
1114                 .pages = pages,
1115                 .nr_pages = 0,
1116                 .partial = partial,
1117                 .flags = flags,
1118                 .ops = &relay_pipe_buf_ops,
1119                 .spd_release = relay_page_release,
1120         };
1121
1122         if (rbuf->subbufs_produced == rbuf->subbufs_consumed)
1123                 return 0;
1124
1125         /*
1126          * Adjust read len, if longer than what is available
1127          */
1128         if (len > (subbuf_size - read_start % subbuf_size))
1129                 len = subbuf_size - read_start % subbuf_size;
1130
1131         subbuf_pages = rbuf->chan->alloc_size >> PAGE_SHIFT;
1132         pidx = (read_start / PAGE_SIZE) % subbuf_pages;
1133         poff = read_start & ~PAGE_MASK;
1134         nr_pages = min_t(unsigned int, subbuf_pages, PIPE_BUFFERS);
1135
1136         for (total_len = 0; spd.nr_pages < nr_pages; spd.nr_pages++) {
1137                 unsigned int this_len, this_end, private;
1138                 unsigned int cur_pos = read_start + total_len;
1139
1140                 if (!len)
1141                         break;
1142
1143                 this_len = min_t(unsigned long, len, PAGE_SIZE - poff);
1144                 private = this_len;
1145
1146                 spd.pages[spd.nr_pages] = rbuf->page_array[pidx];
1147                 spd.partial[spd.nr_pages].offset = poff;
1148
1149                 this_end = cur_pos + this_len;
1150                 if (this_end >= nonpad_end) {
1151                         this_len = nonpad_end - cur_pos;
1152                         private = this_len + padding;
1153                 }
1154                 spd.partial[spd.nr_pages].len = this_len;
1155                 spd.partial[spd.nr_pages].private = private;
1156
1157                 len -= this_len;
1158                 total_len += this_len;
1159                 poff = 0;
1160                 pidx = (pidx + 1) % subbuf_pages;
1161
1162                 if (this_end >= nonpad_end) {
1163                         spd.nr_pages++;
1164                         break;
1165                 }
1166         }
1167
1168         if (!spd.nr_pages)
1169                 return 0;
1170
1171         ret = *nonpad_ret = splice_to_pipe(pipe, &spd);
1172         if (ret < 0 || ret < total_len)
1173                 return ret;
1174
1175         if (read_start + ret == nonpad_end)
1176                 ret += padding;
1177
1178         return ret;
1179 }
1180
1181 static ssize_t relay_file_splice_read(struct file *in,
1182                                       loff_t *ppos,
1183                                       struct pipe_inode_info *pipe,
1184                                       size_t len,
1185                                       unsigned int flags)
1186 {
1187         ssize_t spliced;
1188         int ret;
1189         int nonpad_ret = 0;
1190
1191         ret = 0;
1192         spliced = 0;
1193
1194         while (len) {
1195                 ret = subbuf_splice_actor(in, ppos, pipe, len, flags, &nonpad_ret);
1196                 if (ret < 0)
1197                         break;
1198                 else if (!ret) {
1199                         if (spliced)
1200                                 break;
1201                         if (flags & SPLICE_F_NONBLOCK) {
1202                                 ret = -EAGAIN;
1203                                 break;
1204                         }
1205                 }
1206
1207                 *ppos += ret;
1208                 if (ret > len)
1209                         len = 0;
1210                 else
1211                         len -= ret;
1212                 spliced += nonpad_ret;
1213                 nonpad_ret = 0;
1214         }
1215
1216         if (spliced)
1217                 return spliced;
1218
1219         return ret;
1220 }
1221
1222 const struct file_operations relay_file_operations = {
1223         .open           = relay_file_open,
1224         .poll           = relay_file_poll,
1225         .mmap           = relay_file_mmap,
1226         .read           = relay_file_read,
1227         .llseek         = no_llseek,
1228         .release        = relay_file_release,
1229         .splice_read    = relay_file_splice_read,
1230 };
1231 EXPORT_SYMBOL_GPL(relay_file_operations);
1232
1233 static __init int relay_init(void)
1234 {
1235
1236         hotcpu_notifier(relay_hotcpu_callback, 0);
1237         return 0;
1238 }
1239
1240 module_init(relay_init);