Root/kernel/relay.c

1/*
2 * Public API and common code for kernel->userspace relay file support.
3 *
4 * See Documentation/filesystems/relay.txt for an overview.
5 *
6 * Copyright (C) 2002-2005 - Tom Zanussi (zanussi@us.ibm.com), IBM Corp
7 * Copyright (C) 1999-2005 - Karim Yaghmour (karim@opersys.com)
8 *
9 * Moved to kernel/relay.c by Paul Mundt, 2006.
10 * November 2006 - CPU hotplug support by Mathieu Desnoyers
11 * (mathieu.desnoyers@polymtl.ca)
12 *
13 * This file is released under the GPL.
14 */
15#include <linux/errno.h>
16#include <linux/stddef.h>
17#include <linux/slab.h>
18#include <linux/export.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 */
27static DEFINE_MUTEX(relay_channels_mutex);
28static LIST_HEAD(relay_channels);
29
30/*
31 * close() vm_op implementation for relay file mapping.
32 */
33static 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 */
42static 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 */
63static const struct vm_operations_struct relay_file_mmap_ops = {
64    .fault = relay_buf_fault,
65    .close = relay_file_mmap_close,
66};
67
68/*
69 * allocate an array of pointers of struct page
70 */
71static struct page **relay_alloc_page_array(unsigned int n_pages)
72{
73    const size_t pa_size = n_pages * sizeof(struct page *);
74    if (pa_size > PAGE_SIZE)
75        return vzalloc(pa_size);
76    return kzalloc(pa_size, GFP_KERNEL);
77}
78
79/*
80 * free an array of pointers of struct page
81 */
82static void relay_free_page_array(struct page **array)
83{
84    if (is_vmalloc_addr(array))
85        vfree(array);
86    else
87        kfree(array);
88}
89
90/**
91 * relay_mmap_buf: - mmap channel buffer to process address space
92 * @buf: relay channel buffer
93 * @vma: vm_area_struct describing memory to be mapped
94 *
95 * Returns 0 if ok, negative on error
96 *
97 * Caller should already have grabbed mmap_sem.
98 */
99static int relay_mmap_buf(struct rchan_buf *buf, struct vm_area_struct *vma)
100{
101    unsigned long length = vma->vm_end - vma->vm_start;
102    struct file *filp = vma->vm_file;
103
104    if (!buf)
105        return -EBADF;
106
107    if (length != (unsigned long)buf->chan->alloc_size)
108        return -EINVAL;
109
110    vma->vm_ops = &relay_file_mmap_ops;
111    vma->vm_flags |= VM_DONTEXPAND;
112    vma->vm_private_data = buf;
113    buf->chan->cb->buf_mapped(buf, filp);
114
115    return 0;
116}
117
118/**
119 * relay_alloc_buf - allocate a channel buffer
120 * @buf: the buffer struct
121 * @size: total size of the buffer
122 *
123 * Returns a pointer to the resulting buffer, %NULL if unsuccessful. The
124 * passed in size will get page aligned, if it isn't already.
125 */
126static void *relay_alloc_buf(struct rchan_buf *buf, size_t *size)
127{
128    void *mem;
129    unsigned int i, j, n_pages;
130
131    *size = PAGE_ALIGN(*size);
132    n_pages = *size >> PAGE_SHIFT;
133
134    buf->page_array = relay_alloc_page_array(n_pages);
135    if (!buf->page_array)
136        return NULL;
137
138    for (i = 0; i < n_pages; i++) {
139        buf->page_array[i] = alloc_page(GFP_KERNEL);
140        if (unlikely(!buf->page_array[i]))
141            goto depopulate;
142        set_page_private(buf->page_array[i], (unsigned long)buf);
143    }
144    mem = vmap(buf->page_array, n_pages, VM_MAP, PAGE_KERNEL);
145    if (!mem)
146        goto depopulate;
147
148    memset(mem, 0, *size);
149    buf->page_count = n_pages;
150    return mem;
151
152depopulate:
153    for (j = 0; j < i; j++)
154        __free_page(buf->page_array[j]);
155    relay_free_page_array(buf->page_array);
156    return NULL;
157}
158
159/**
160 * relay_create_buf - allocate and initialize a channel buffer
161 * @chan: the relay channel
162 *
163 * Returns channel buffer if successful, %NULL otherwise.
164 */
165static struct rchan_buf *relay_create_buf(struct rchan *chan)
166{
167    struct rchan_buf *buf;
168
169    if (chan->n_subbufs > UINT_MAX / sizeof(size_t *))
170        return NULL;
171
172    buf = kzalloc(sizeof(struct rchan_buf), GFP_KERNEL);
173    if (!buf)
174        return NULL;
175    buf->padding = kmalloc(chan->n_subbufs * sizeof(size_t *), GFP_KERNEL);
176    if (!buf->padding)
177        goto free_buf;
178
179    buf->start = relay_alloc_buf(buf, &chan->alloc_size);
180    if (!buf->start)
181        goto free_buf;
182
183    buf->chan = chan;
184    kref_get(&buf->chan->kref);
185    return buf;
186
187free_buf:
188    kfree(buf->padding);
189    kfree(buf);
190    return NULL;
191}
192
193/**
194 * relay_destroy_channel - free the channel struct
195 * @kref: target kernel reference that contains the relay channel
196 *
197 * Should only be called from kref_put().
198 */
199static void relay_destroy_channel(struct kref *kref)
200{
201    struct rchan *chan = container_of(kref, struct rchan, kref);
202    kfree(chan);
203}
204
205/**
206 * relay_destroy_buf - destroy an rchan_buf struct and associated buffer
207 * @buf: the buffer struct
208 */
209static void relay_destroy_buf(struct rchan_buf *buf)
210{
211    struct rchan *chan = buf->chan;
212    unsigned int i;
213
214    if (likely(buf->start)) {
215        vunmap(buf->start);
216        for (i = 0; i < buf->page_count; i++)
217            __free_page(buf->page_array[i]);
218        relay_free_page_array(buf->page_array);
219    }
220    chan->buf[buf->cpu] = NULL;
221    kfree(buf->padding);
222    kfree(buf);
223    kref_put(&chan->kref, relay_destroy_channel);
224}
225
226/**
227 * relay_remove_buf - remove a channel buffer
228 * @kref: target kernel reference that contains the relay buffer
229 *
230 * Removes the file from the fileystem, which also frees the
231 * rchan_buf_struct and the channel buffer. Should only be called from
232 * kref_put().
233 */
234static void relay_remove_buf(struct kref *kref)
235{
236    struct rchan_buf *buf = container_of(kref, struct rchan_buf, kref);
237    buf->chan->cb->remove_buf_file(buf->dentry);
238    relay_destroy_buf(buf);
239}
240
241/**
242 * relay_buf_empty - boolean, is the channel buffer empty?
243 * @buf: channel buffer
244 *
245 * Returns 1 if the buffer is empty, 0 otherwise.
246 */
247static int relay_buf_empty(struct rchan_buf *buf)
248{
249    return (buf->subbufs_produced - buf->subbufs_consumed) ? 0 : 1;
250}
251
252/**
253 * relay_buf_full - boolean, is the channel buffer full?
254 * @buf: channel buffer
255 *
256 * Returns 1 if the buffer is full, 0 otherwise.
257 */
258int relay_buf_full(struct rchan_buf *buf)
259{
260    size_t ready = buf->subbufs_produced - buf->subbufs_consumed;
261    return (ready >= buf->chan->n_subbufs) ? 1 : 0;
262}
263EXPORT_SYMBOL_GPL(relay_buf_full);
264
265/*
266 * High-level relay kernel API and associated functions.
267 */
268
269/*
270 * rchan_callback implementations defining default channel behavior. Used
271 * in place of corresponding NULL values in client callback struct.
272 */
273
274/*
275 * subbuf_start() default callback. Does nothing.
276 */
277static int subbuf_start_default_callback (struct rchan_buf *buf,
278                      void *subbuf,
279                      void *prev_subbuf,
280                      size_t prev_padding)
281{
282    if (relay_buf_full(buf))
283        return 0;
284
285    return 1;
286}
287
288/*
289 * buf_mapped() default callback. Does nothing.
290 */
291static void buf_mapped_default_callback(struct rchan_buf *buf,
292                    struct file *filp)
293{
294}
295
296/*
297 * buf_unmapped() default callback. Does nothing.
298 */
299static void buf_unmapped_default_callback(struct rchan_buf *buf,
300                      struct file *filp)
301{
302}
303
304/*
305 * create_buf_file_create() default callback. Does nothing.
306 */
307static struct dentry *create_buf_file_default_callback(const char *filename,
308                               struct dentry *parent,
309                               umode_t mode,
310                               struct rchan_buf *buf,
311                               int *is_global)
312{
313    return NULL;
314}
315
316/*
317 * remove_buf_file() default callback. Does nothing.
318 */
319static int remove_buf_file_default_callback(struct dentry *dentry)
320{
321    return -EINVAL;
322}
323
324/* relay channel default callbacks */
325static struct rchan_callbacks default_channel_callbacks = {
326    .subbuf_start = subbuf_start_default_callback,
327    .buf_mapped = buf_mapped_default_callback,
328    .buf_unmapped = buf_unmapped_default_callback,
329    .create_buf_file = create_buf_file_default_callback,
330    .remove_buf_file = remove_buf_file_default_callback,
331};
332
333/**
334 * wakeup_readers - wake up readers waiting on a channel
335 * @data: contains the channel buffer
336 *
337 * This is the timer function used to defer reader waking.
338 */
339static void wakeup_readers(unsigned long data)
340{
341    struct rchan_buf *buf = (struct rchan_buf *)data;
342    wake_up_interruptible(&buf->read_wait);
343}
344
345/**
346 * __relay_reset - reset a channel buffer
347 * @buf: the channel buffer
348 * @init: 1 if this is a first-time initialization
349 *
350 * See relay_reset() for description of effect.
351 */
352static void __relay_reset(struct rchan_buf *buf, unsigned int init)
353{
354    size_t i;
355
356    if (init) {
357        init_waitqueue_head(&buf->read_wait);
358        kref_init(&buf->kref);
359        setup_timer(&buf->timer, wakeup_readers, (unsigned long)buf);
360    } else
361        del_timer_sync(&buf->timer);
362
363    buf->subbufs_produced = 0;
364    buf->subbufs_consumed = 0;
365    buf->bytes_consumed = 0;
366    buf->finalized = 0;
367    buf->data = buf->start;
368    buf->offset = 0;
369
370    for (i = 0; i < buf->chan->n_subbufs; i++)
371        buf->padding[i] = 0;
372
373    buf->chan->cb->subbuf_start(buf, buf->data, NULL, 0);
374}
375
376/**
377 * relay_reset - reset the channel
378 * @chan: the channel
379 *
380 * This has the effect of erasing all data from all channel buffers
381 * and restarting the channel in its initial state. The buffers
382 * are not freed, so any mappings are still in effect.
383 *
384 * NOTE. Care should be taken that the channel isn't actually
385 * being used by anything when this call is made.
386 */
387void relay_reset(struct rchan *chan)
388{
389    unsigned int i;
390
391    if (!chan)
392        return;
393
394    if (chan->is_global && chan->buf[0]) {
395        __relay_reset(chan->buf[0], 0);
396        return;
397    }
398
399    mutex_lock(&relay_channels_mutex);
400    for_each_possible_cpu(i)
401        if (chan->buf[i])
402            __relay_reset(chan->buf[i], 0);
403    mutex_unlock(&relay_channels_mutex);
404}
405EXPORT_SYMBOL_GPL(relay_reset);
406
407static inline void relay_set_buf_dentry(struct rchan_buf *buf,
408                    struct dentry *dentry)
409{
410    buf->dentry = dentry;
411    buf->dentry->d_inode->i_size = buf->early_bytes;
412}
413
414static struct dentry *relay_create_buf_file(struct rchan *chan,
415                        struct rchan_buf *buf,
416                        unsigned int cpu)
417{
418    struct dentry *dentry;
419    char *tmpname;
420
421    tmpname = kzalloc(NAME_MAX + 1, GFP_KERNEL);
422    if (!tmpname)
423        return NULL;
424    snprintf(tmpname, NAME_MAX, "%s%d", chan->base_filename, cpu);
425
426    /* Create file in fs */
427    dentry = chan->cb->create_buf_file(tmpname, chan->parent,
428                       S_IRUSR, buf,
429                       &chan->is_global);
430
431    kfree(tmpname);
432
433    return dentry;
434}
435
436/*
437 * relay_open_buf - create a new relay channel buffer
438 *
439 * used by relay_open() and CPU hotplug.
440 */
441static struct rchan_buf *relay_open_buf(struct rchan *chan, unsigned int cpu)
442{
443     struct rchan_buf *buf = NULL;
444    struct dentry *dentry;
445
446     if (chan->is_global)
447        return chan->buf[0];
448
449    buf = relay_create_buf(chan);
450    if (!buf)
451        return NULL;
452
453    if (chan->has_base_filename) {
454        dentry = relay_create_buf_file(chan, buf, cpu);
455        if (!dentry)
456            goto free_buf;
457        relay_set_buf_dentry(buf, dentry);
458    }
459
460     buf->cpu = cpu;
461     __relay_reset(buf, 1);
462
463     if(chan->is_global) {
464         chan->buf[0] = buf;
465         buf->cpu = 0;
466      }
467
468    return buf;
469
470free_buf:
471     relay_destroy_buf(buf);
472    return NULL;
473}
474
475/**
476 * relay_close_buf - close a channel buffer
477 * @buf: channel buffer
478 *
479 * Marks the buffer finalized and restores the default callbacks.
480 * The channel buffer and channel buffer data structure are then freed
481 * automatically when the last reference is given up.
482 */
483static void relay_close_buf(struct rchan_buf *buf)
484{
485    buf->finalized = 1;
486    del_timer_sync(&buf->timer);
487    kref_put(&buf->kref, relay_remove_buf);
488}
489
490static void setup_callbacks(struct rchan *chan,
491                   struct rchan_callbacks *cb)
492{
493    if (!cb) {
494        chan->cb = &default_channel_callbacks;
495        return;
496    }
497
498    if (!cb->subbuf_start)
499        cb->subbuf_start = subbuf_start_default_callback;
500    if (!cb->buf_mapped)
501        cb->buf_mapped = buf_mapped_default_callback;
502    if (!cb->buf_unmapped)
503        cb->buf_unmapped = buf_unmapped_default_callback;
504    if (!cb->create_buf_file)
505        cb->create_buf_file = create_buf_file_default_callback;
506    if (!cb->remove_buf_file)
507        cb->remove_buf_file = remove_buf_file_default_callback;
508    chan->cb = cb;
509}
510
511/**
512 * relay_hotcpu_callback - CPU hotplug callback
513 * @nb: notifier block
514 * @action: hotplug action to take
515 * @hcpu: CPU number
516 *
517 * Returns the success/failure of the operation. (%NOTIFY_OK, %NOTIFY_BAD)
518 */
519static int __cpuinit relay_hotcpu_callback(struct notifier_block *nb,
520                unsigned long action,
521                void *hcpu)
522{
523    unsigned int hotcpu = (unsigned long)hcpu;
524    struct rchan *chan;
525
526    switch(action) {
527    case CPU_UP_PREPARE:
528    case CPU_UP_PREPARE_FROZEN:
529        mutex_lock(&relay_channels_mutex);
530        list_for_each_entry(chan, &relay_channels, list) {
531            if (chan->buf[hotcpu])
532                continue;
533            chan->buf[hotcpu] = relay_open_buf(chan, hotcpu);
534            if(!chan->buf[hotcpu]) {
535                printk(KERN_ERR
536                    "relay_hotcpu_callback: cpu %d buffer "
537                    "creation failed\n", hotcpu);
538                mutex_unlock(&relay_channels_mutex);
539                return notifier_from_errno(-ENOMEM);
540            }
541        }
542        mutex_unlock(&relay_channels_mutex);
543        break;
544    case CPU_DEAD:
545    case CPU_DEAD_FROZEN:
546        /* No need to flush the cpu : will be flushed upon
547         * final relay_flush() call. */
548        break;
549    }
550    return NOTIFY_OK;
551}
552
553/**
554 * relay_open - create a new relay channel
555 * @base_filename: base name of files to create, %NULL for buffering only
556 * @parent: dentry of parent directory, %NULL for root directory or buffer
557 * @subbuf_size: size of sub-buffers
558 * @n_subbufs: number of sub-buffers
559 * @cb: client callback functions
560 * @private_data: user-defined data
561 *
562 * Returns channel pointer if successful, %NULL otherwise.
563 *
564 * Creates a channel buffer for each cpu using the sizes and
565 * attributes specified. The created channel buffer files
566 * will be named base_filename0...base_filenameN-1. File
567 * permissions will be %S_IRUSR.
568 */
569struct rchan *relay_open(const char *base_filename,
570             struct dentry *parent,
571             size_t subbuf_size,
572             size_t n_subbufs,
573             struct rchan_callbacks *cb,
574             void *private_data)
575{
576    unsigned int i;
577    struct rchan *chan;
578
579    if (!(subbuf_size && n_subbufs))
580        return NULL;
581    if (subbuf_size > UINT_MAX / n_subbufs)
582        return NULL;
583
584    chan = kzalloc(sizeof(struct rchan), GFP_KERNEL);
585    if (!chan)
586        return NULL;
587
588    chan->version = RELAYFS_CHANNEL_VERSION;
589    chan->n_subbufs = n_subbufs;
590    chan->subbuf_size = subbuf_size;
591    chan->alloc_size = FIX_SIZE(subbuf_size * n_subbufs);
592    chan->parent = parent;
593    chan->private_data = private_data;
594    if (base_filename) {
595        chan->has_base_filename = 1;
596        strlcpy(chan->base_filename, base_filename, NAME_MAX);
597    }
598    setup_callbacks(chan, cb);
599    kref_init(&chan->kref);
600
601    mutex_lock(&relay_channels_mutex);
602    for_each_online_cpu(i) {
603        chan->buf[i] = relay_open_buf(chan, i);
604        if (!chan->buf[i])
605            goto free_bufs;
606    }
607    list_add(&chan->list, &relay_channels);
608    mutex_unlock(&relay_channels_mutex);
609
610    return chan;
611
612free_bufs:
613    for_each_possible_cpu(i) {
614        if (chan->buf[i])
615            relay_close_buf(chan->buf[i]);
616    }
617
618    kref_put(&chan->kref, relay_destroy_channel);
619    mutex_unlock(&relay_channels_mutex);
620    return NULL;
621}
622EXPORT_SYMBOL_GPL(relay_open);
623
624struct rchan_percpu_buf_dispatcher {
625    struct rchan_buf *buf;
626    struct dentry *dentry;
627};
628
629/* Called in atomic context. */
630static void __relay_set_buf_dentry(void *info)
631{
632    struct rchan_percpu_buf_dispatcher *p = info;
633
634    relay_set_buf_dentry(p->buf, p->dentry);
635}
636
637/**
638 * relay_late_setup_files - triggers file creation
639 * @chan: channel to operate on
640 * @base_filename: base name of files to create
641 * @parent: dentry of parent directory, %NULL for root directory
642 *
643 * Returns 0 if successful, non-zero otherwise.
644 *
645 * Use to setup files for a previously buffer-only channel.
646 * Useful to do early tracing in kernel, before VFS is up, for example.
647 */
648int relay_late_setup_files(struct rchan *chan,
649               const char *base_filename,
650               struct dentry *parent)
651{
652    int err = 0;
653    unsigned int i, curr_cpu;
654    unsigned long flags;
655    struct dentry *dentry;
656    struct rchan_percpu_buf_dispatcher disp;
657
658    if (!chan || !base_filename)
659        return -EINVAL;
660
661    strlcpy(chan->base_filename, base_filename, NAME_MAX);
662
663    mutex_lock(&relay_channels_mutex);
664    /* Is chan already set up? */
665    if (unlikely(chan->has_base_filename)) {
666        mutex_unlock(&relay_channels_mutex);
667        return -EEXIST;
668    }
669    chan->has_base_filename = 1;
670    chan->parent = parent;
671    curr_cpu = get_cpu();
672    /*
673     * The CPU hotplug notifier ran before us and created buffers with
674     * no files associated. So it's safe to call relay_setup_buf_file()
675     * on all currently online CPUs.
676     */
677    for_each_online_cpu(i) {
678        if (unlikely(!chan->buf[i])) {
679            WARN_ONCE(1, KERN_ERR "CPU has no buffer!\n");
680            err = -EINVAL;
681            break;
682        }
683
684        dentry = relay_create_buf_file(chan, chan->buf[i], i);
685        if (unlikely(!dentry)) {
686            err = -EINVAL;
687            break;
688        }
689
690        if (curr_cpu == i) {
691            local_irq_save(flags);
692            relay_set_buf_dentry(chan->buf[i], dentry);
693            local_irq_restore(flags);
694        } else {
695            disp.buf = chan->buf[i];
696            disp.dentry = dentry;
697            smp_mb();
698            /* relay_channels_mutex must be held, so wait. */
699            err = smp_call_function_single(i,
700                               __relay_set_buf_dentry,
701                               &disp, 1);
702        }
703        if (unlikely(err))
704            break;
705    }
706    put_cpu();
707    mutex_unlock(&relay_channels_mutex);
708
709    return err;
710}
711
712/**
713 * relay_switch_subbuf - switch to a new sub-buffer
714 * @buf: channel buffer
715 * @length: size of current event
716 *
717 * Returns either the length passed in or 0 if full.
718 *
719 * Performs sub-buffer-switch tasks such as invoking callbacks,
720 * updating padding counts, waking up readers, etc.
721 */
722size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length)
723{
724    void *old, *new;
725    size_t old_subbuf, new_subbuf;
726
727    if (unlikely(length > buf->chan->subbuf_size))
728        goto toobig;
729
730    if (buf->offset != buf->chan->subbuf_size + 1) {
731        buf->prev_padding = buf->chan->subbuf_size - buf->offset;
732        old_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
733        buf->padding[old_subbuf] = buf->prev_padding;
734        buf->subbufs_produced++;
735        if (buf->dentry)
736            buf->dentry->d_inode->i_size +=
737                buf->chan->subbuf_size -
738                buf->padding[old_subbuf];
739        else
740            buf->early_bytes += buf->chan->subbuf_size -
741                        buf->padding[old_subbuf];
742        smp_mb();
743        if (waitqueue_active(&buf->read_wait))
744            /*
745             * Calling wake_up_interruptible() from here
746             * will deadlock if we happen to be logging
747             * from the scheduler (trying to re-grab
748             * rq->lock), so defer it.
749             */
750            mod_timer(&buf->timer, jiffies + 1);
751    }
752
753    old = buf->data;
754    new_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
755    new = buf->start + new_subbuf * buf->chan->subbuf_size;
756    buf->offset = 0;
757    if (!buf->chan->cb->subbuf_start(buf, new, old, buf->prev_padding)) {
758        buf->offset = buf->chan->subbuf_size + 1;
759        return 0;
760    }
761    buf->data = new;
762    buf->padding[new_subbuf] = 0;
763
764    if (unlikely(length + buf->offset > buf->chan->subbuf_size))
765        goto toobig;
766
767    return length;
768
769toobig:
770    buf->chan->last_toobig = length;
771    return 0;
772}
773EXPORT_SYMBOL_GPL(relay_switch_subbuf);
774
775/**
776 * relay_subbufs_consumed - update the buffer's sub-buffers-consumed count
777 * @chan: the channel
778 * @cpu: the cpu associated with the channel buffer to update
779 * @subbufs_consumed: number of sub-buffers to add to current buf's count
780 *
781 * Adds to the channel buffer's consumed sub-buffer count.
782 * subbufs_consumed should be the number of sub-buffers newly consumed,
783 * not the total consumed.
784 *
785 * NOTE. Kernel clients don't need to call this function if the channel
786 * mode is 'overwrite'.
787 */
788void relay_subbufs_consumed(struct rchan *chan,
789                unsigned int cpu,
790                size_t subbufs_consumed)
791{
792    struct rchan_buf *buf;
793
794    if (!chan)
795        return;
796
797    if (cpu >= NR_CPUS || !chan->buf[cpu] ||
798                    subbufs_consumed > chan->n_subbufs)
799        return;
800
801    buf = chan->buf[cpu];
802    if (subbufs_consumed > buf->subbufs_produced - buf->subbufs_consumed)
803        buf->subbufs_consumed = buf->subbufs_produced;
804    else
805        buf->subbufs_consumed += subbufs_consumed;
806}
807EXPORT_SYMBOL_GPL(relay_subbufs_consumed);
808
809/**
810 * relay_close - close the channel
811 * @chan: the channel
812 *
813 * Closes all channel buffers and frees the channel.
814 */
815void relay_close(struct rchan *chan)
816{
817    unsigned int i;
818
819    if (!chan)
820        return;
821
822    mutex_lock(&relay_channels_mutex);
823    if (chan->is_global && chan->buf[0])
824        relay_close_buf(chan->buf[0]);
825    else
826        for_each_possible_cpu(i)
827            if (chan->buf[i])
828                relay_close_buf(chan->buf[i]);
829
830    if (chan->last_toobig)
831        printk(KERN_WARNING "relay: one or more items not logged "
832               "[item size (%Zd) > sub-buffer size (%Zd)]\n",
833               chan->last_toobig, chan->subbuf_size);
834
835    list_del(&chan->list);
836    kref_put(&chan->kref, relay_destroy_channel);
837    mutex_unlock(&relay_channels_mutex);
838}
839EXPORT_SYMBOL_GPL(relay_close);
840
841/**
842 * relay_flush - close the channel
843 * @chan: the channel
844 *
845 * Flushes all channel buffers, i.e. forces buffer switch.
846 */
847void relay_flush(struct rchan *chan)
848{
849    unsigned int i;
850
851    if (!chan)
852        return;
853
854    if (chan->is_global && chan->buf[0]) {
855        relay_switch_subbuf(chan->buf[0], 0);
856        return;
857    }
858
859    mutex_lock(&relay_channels_mutex);
860    for_each_possible_cpu(i)
861        if (chan->buf[i])
862            relay_switch_subbuf(chan->buf[i], 0);
863    mutex_unlock(&relay_channels_mutex);
864}
865EXPORT_SYMBOL_GPL(relay_flush);
866
867/**
868 * relay_file_open - open file op for relay files
869 * @inode: the inode
870 * @filp: the file
871 *
872 * Increments the channel buffer refcount.
873 */
874static int relay_file_open(struct inode *inode, struct file *filp)
875{
876    struct rchan_buf *buf = inode->i_private;
877    kref_get(&buf->kref);
878    filp->private_data = buf;
879
880    return nonseekable_open(inode, filp);
881}
882
883/**
884 * relay_file_mmap - mmap file op for relay files
885 * @filp: the file
886 * @vma: the vma describing what to map
887 *
888 * Calls upon relay_mmap_buf() to map the file into user space.
889 */
890static int relay_file_mmap(struct file *filp, struct vm_area_struct *vma)
891{
892    struct rchan_buf *buf = filp->private_data;
893    return relay_mmap_buf(buf, vma);
894}
895
896/**
897 * relay_file_poll - poll file op for relay files
898 * @filp: the file
899 * @wait: poll table
900 *
901 * Poll implemention.
902 */
903static unsigned int relay_file_poll(struct file *filp, poll_table *wait)
904{
905    unsigned int mask = 0;
906    struct rchan_buf *buf = filp->private_data;
907
908    if (buf->finalized)
909        return POLLERR;
910
911    if (filp->f_mode & FMODE_READ) {
912        poll_wait(filp, &buf->read_wait, wait);
913        if (!relay_buf_empty(buf))
914            mask |= POLLIN | POLLRDNORM;
915    }
916
917    return mask;
918}
919
920/**
921 * relay_file_release - release file op for relay files
922 * @inode: the inode
923 * @filp: the file
924 *
925 * Decrements the channel refcount, as the filesystem is
926 * no longer using it.
927 */
928static int relay_file_release(struct inode *inode, struct file *filp)
929{
930    struct rchan_buf *buf = filp->private_data;
931    kref_put(&buf->kref, relay_remove_buf);
932
933    return 0;
934}
935
936/*
937 * relay_file_read_consume - update the consumed count for the buffer
938 */
939static void relay_file_read_consume(struct rchan_buf *buf,
940                    size_t read_pos,
941                    size_t bytes_consumed)
942{
943    size_t subbuf_size = buf->chan->subbuf_size;
944    size_t n_subbufs = buf->chan->n_subbufs;
945    size_t read_subbuf;
946
947    if (buf->subbufs_produced == buf->subbufs_consumed &&
948        buf->offset == buf->bytes_consumed)
949        return;
950
951    if (buf->bytes_consumed + bytes_consumed > subbuf_size) {
952        relay_subbufs_consumed(buf->chan, buf->cpu, 1);
953        buf->bytes_consumed = 0;
954    }
955
956    buf->bytes_consumed += bytes_consumed;
957    if (!read_pos)
958        read_subbuf = buf->subbufs_consumed % n_subbufs;
959    else
960        read_subbuf = read_pos / buf->chan->subbuf_size;
961    if (buf->bytes_consumed + buf->padding[read_subbuf] == subbuf_size) {
962        if ((read_subbuf == buf->subbufs_produced % n_subbufs) &&
963            (buf->offset == subbuf_size))
964            return;
965        relay_subbufs_consumed(buf->chan, buf->cpu, 1);
966        buf->bytes_consumed = 0;
967    }
968}
969
970/*
971 * relay_file_read_avail - boolean, are there unconsumed bytes available?
972 */
973static int relay_file_read_avail(struct rchan_buf *buf, size_t read_pos)
974{
975    size_t subbuf_size = buf->chan->subbuf_size;
976    size_t n_subbufs = buf->chan->n_subbufs;
977    size_t produced = buf->subbufs_produced;
978    size_t consumed = buf->subbufs_consumed;
979
980    relay_file_read_consume(buf, read_pos, 0);
981
982    consumed = buf->subbufs_consumed;
983
984    if (unlikely(buf->offset > subbuf_size)) {
985        if (produced == consumed)
986            return 0;
987        return 1;
988    }
989
990    if (unlikely(produced - consumed >= n_subbufs)) {
991        consumed = produced - n_subbufs + 1;
992        buf->subbufs_consumed = consumed;
993        buf->bytes_consumed = 0;
994    }
995
996    produced = (produced % n_subbufs) * subbuf_size + buf->offset;
997    consumed = (consumed % n_subbufs) * subbuf_size + buf->bytes_consumed;
998
999    if (consumed > produced)
1000        produced += n_subbufs * subbuf_size;
1001
1002    if (consumed == produced) {
1003        if (buf->offset == subbuf_size &&
1004            buf->subbufs_produced > buf->subbufs_consumed)
1005            return 1;
1006        return 0;
1007    }
1008
1009    return 1;
1010}
1011
1012/**
1013 * relay_file_read_subbuf_avail - return bytes available in sub-buffer
1014 * @read_pos: file read position
1015 * @buf: relay channel buffer
1016 */
1017static size_t relay_file_read_subbuf_avail(size_t read_pos,
1018                       struct rchan_buf *buf)
1019{
1020    size_t padding, avail = 0;
1021    size_t read_subbuf, read_offset, write_subbuf, write_offset;
1022    size_t subbuf_size = buf->chan->subbuf_size;
1023
1024    write_subbuf = (buf->data - buf->start) / subbuf_size;
1025    write_offset = buf->offset > subbuf_size ? subbuf_size : buf->offset;
1026    read_subbuf = read_pos / subbuf_size;
1027    read_offset = read_pos % subbuf_size;
1028    padding = buf->padding[read_subbuf];
1029
1030    if (read_subbuf == write_subbuf) {
1031        if (read_offset + padding < write_offset)
1032            avail = write_offset - (read_offset + padding);
1033    } else
1034        avail = (subbuf_size - padding) - read_offset;
1035
1036    return avail;
1037}
1038
1039/**
1040 * relay_file_read_start_pos - find the first available byte to read
1041 * @read_pos: file read position
1042 * @buf: relay channel buffer
1043 *
1044 * If the @read_pos is in the middle of padding, return the
1045 * position of the first actually available byte, otherwise
1046 * return the original value.
1047 */
1048static size_t relay_file_read_start_pos(size_t read_pos,
1049                    struct rchan_buf *buf)
1050{
1051    size_t read_subbuf, padding, padding_start, padding_end;
1052    size_t subbuf_size = buf->chan->subbuf_size;
1053    size_t n_subbufs = buf->chan->n_subbufs;
1054    size_t consumed = buf->subbufs_consumed % n_subbufs;
1055
1056    if (!read_pos)
1057        read_pos = consumed * subbuf_size + buf->bytes_consumed;
1058    read_subbuf = read_pos / subbuf_size;
1059    padding = buf->padding[read_subbuf];
1060    padding_start = (read_subbuf + 1) * subbuf_size - padding;
1061    padding_end = (read_subbuf + 1) * subbuf_size;
1062    if (read_pos >= padding_start && read_pos < padding_end) {
1063        read_subbuf = (read_subbuf + 1) % n_subbufs;
1064        read_pos = read_subbuf * subbuf_size;
1065    }
1066
1067    return read_pos;
1068}
1069
1070/**
1071 * relay_file_read_end_pos - return the new read position
1072 * @read_pos: file read position
1073 * @buf: relay channel buffer
1074 * @count: number of bytes to be read
1075 */
1076static size_t relay_file_read_end_pos(struct rchan_buf *buf,
1077                      size_t read_pos,
1078                      size_t count)
1079{
1080    size_t read_subbuf, padding, end_pos;
1081    size_t subbuf_size = buf->chan->subbuf_size;
1082    size_t n_subbufs = buf->chan->n_subbufs;
1083
1084    read_subbuf = read_pos / subbuf_size;
1085    padding = buf->padding[read_subbuf];
1086    if (read_pos % subbuf_size + count + padding == subbuf_size)
1087        end_pos = (read_subbuf + 1) * subbuf_size;
1088    else
1089        end_pos = read_pos + count;
1090    if (end_pos >= subbuf_size * n_subbufs)
1091        end_pos = 0;
1092
1093    return end_pos;
1094}
1095
1096/*
1097 * subbuf_read_actor - read up to one subbuf's worth of data
1098 */
1099static int subbuf_read_actor(size_t read_start,
1100                 struct rchan_buf *buf,
1101                 size_t avail,
1102                 read_descriptor_t *desc,
1103                 read_actor_t actor)
1104{
1105    void *from;
1106    int ret = 0;
1107
1108    from = buf->start + read_start;
1109    ret = avail;
1110    if (copy_to_user(desc->arg.buf, from, avail)) {
1111        desc->error = -EFAULT;
1112        ret = 0;
1113    }
1114    desc->arg.data += ret;
1115    desc->written += ret;
1116    desc->count -= ret;
1117
1118    return ret;
1119}
1120
1121typedef int (*subbuf_actor_t) (size_t read_start,
1122                   struct rchan_buf *buf,
1123                   size_t avail,
1124                   read_descriptor_t *desc,
1125                   read_actor_t actor);
1126
1127/*
1128 * relay_file_read_subbufs - read count bytes, bridging subbuf boundaries
1129 */
1130static ssize_t relay_file_read_subbufs(struct file *filp, loff_t *ppos,
1131                    subbuf_actor_t subbuf_actor,
1132                    read_actor_t actor,
1133                    read_descriptor_t *desc)
1134{
1135    struct rchan_buf *buf = filp->private_data;
1136    size_t read_start, avail;
1137    int ret;
1138
1139    if (!desc->count)
1140        return 0;
1141
1142    mutex_lock(&filp->f_path.dentry->d_inode->i_mutex);
1143    do {
1144        if (!relay_file_read_avail(buf, *ppos))
1145            break;
1146
1147        read_start = relay_file_read_start_pos(*ppos, buf);
1148        avail = relay_file_read_subbuf_avail(read_start, buf);
1149        if (!avail)
1150            break;
1151
1152        avail = min(desc->count, avail);
1153        ret = subbuf_actor(read_start, buf, avail, desc, actor);
1154        if (desc->error < 0)
1155            break;
1156
1157        if (ret) {
1158            relay_file_read_consume(buf, read_start, ret);
1159            *ppos = relay_file_read_end_pos(buf, read_start, ret);
1160        }
1161    } while (desc->count && ret);
1162    mutex_unlock(&filp->f_path.dentry->d_inode->i_mutex);
1163
1164    return desc->written;
1165}
1166
1167static ssize_t relay_file_read(struct file *filp,
1168                   char __user *buffer,
1169                   size_t count,
1170                   loff_t *ppos)
1171{
1172    read_descriptor_t desc;
1173    desc.written = 0;
1174    desc.count = count;
1175    desc.arg.buf = buffer;
1176    desc.error = 0;
1177    return relay_file_read_subbufs(filp, ppos, subbuf_read_actor,
1178                       NULL, &desc);
1179}
1180
1181static void relay_consume_bytes(struct rchan_buf *rbuf, int bytes_consumed)
1182{
1183    rbuf->bytes_consumed += bytes_consumed;
1184
1185    if (rbuf->bytes_consumed >= rbuf->chan->subbuf_size) {
1186        relay_subbufs_consumed(rbuf->chan, rbuf->cpu, 1);
1187        rbuf->bytes_consumed %= rbuf->chan->subbuf_size;
1188    }
1189}
1190
1191static void relay_pipe_buf_release(struct pipe_inode_info *pipe,
1192                   struct pipe_buffer *buf)
1193{
1194    struct rchan_buf *rbuf;
1195
1196    rbuf = (struct rchan_buf *)page_private(buf->page);
1197    relay_consume_bytes(rbuf, buf->private);
1198}
1199
1200static const struct pipe_buf_operations relay_pipe_buf_ops = {
1201    .can_merge = 0,
1202    .map = generic_pipe_buf_map,
1203    .unmap = generic_pipe_buf_unmap,
1204    .confirm = generic_pipe_buf_confirm,
1205    .release = relay_pipe_buf_release,
1206    .steal = generic_pipe_buf_steal,
1207    .get = generic_pipe_buf_get,
1208};
1209
1210static void relay_page_release(struct splice_pipe_desc *spd, unsigned int i)
1211{
1212}
1213
1214/*
1215 * subbuf_splice_actor - splice up to one subbuf's worth of data
1216 */
1217static ssize_t subbuf_splice_actor(struct file *in,
1218                   loff_t *ppos,
1219                   struct pipe_inode_info *pipe,
1220                   size_t len,
1221                   unsigned int flags,
1222                   int *nonpad_ret)
1223{
1224    unsigned int pidx, poff, total_len, subbuf_pages, nr_pages;
1225    struct rchan_buf *rbuf = in->private_data;
1226    unsigned int subbuf_size = rbuf->chan->subbuf_size;
1227    uint64_t pos = (uint64_t) *ppos;
1228    uint32_t alloc_size = (uint32_t) rbuf->chan->alloc_size;
1229    size_t read_start = (size_t) do_div(pos, alloc_size);
1230    size_t read_subbuf = read_start / subbuf_size;
1231    size_t padding = rbuf->padding[read_subbuf];
1232    size_t nonpad_end = read_subbuf * subbuf_size + subbuf_size - padding;
1233    struct page *pages[PIPE_DEF_BUFFERS];
1234    struct partial_page partial[PIPE_DEF_BUFFERS];
1235    struct splice_pipe_desc spd = {
1236        .pages = pages,
1237        .nr_pages = 0,
1238        .nr_pages_max = PIPE_DEF_BUFFERS,
1239        .partial = partial,
1240        .flags = flags,
1241        .ops = &relay_pipe_buf_ops,
1242        .spd_release = relay_page_release,
1243    };
1244    ssize_t ret;
1245
1246    if (rbuf->subbufs_produced == rbuf->subbufs_consumed)
1247        return 0;
1248    if (splice_grow_spd(pipe, &spd))
1249        return -ENOMEM;
1250
1251    /*
1252     * Adjust read len, if longer than what is available
1253     */
1254    if (len > (subbuf_size - read_start % subbuf_size))
1255        len = subbuf_size - read_start % subbuf_size;
1256
1257    subbuf_pages = rbuf->chan->alloc_size >> PAGE_SHIFT;
1258    pidx = (read_start / PAGE_SIZE) % subbuf_pages;
1259    poff = read_start & ~PAGE_MASK;
1260    nr_pages = min_t(unsigned int, subbuf_pages, pipe->buffers);
1261
1262    for (total_len = 0; spd.nr_pages < nr_pages; spd.nr_pages++) {
1263        unsigned int this_len, this_end, private;
1264        unsigned int cur_pos = read_start + total_len;
1265
1266        if (!len)
1267            break;
1268
1269        this_len = min_t(unsigned long, len, PAGE_SIZE - poff);
1270        private = this_len;
1271
1272        spd.pages[spd.nr_pages] = rbuf->page_array[pidx];
1273        spd.partial[spd.nr_pages].offset = poff;
1274
1275        this_end = cur_pos + this_len;
1276        if (this_end >= nonpad_end) {
1277            this_len = nonpad_end - cur_pos;
1278            private = this_len + padding;
1279        }
1280        spd.partial[spd.nr_pages].len = this_len;
1281        spd.partial[spd.nr_pages].private = private;
1282
1283        len -= this_len;
1284        total_len += this_len;
1285        poff = 0;
1286        pidx = (pidx + 1) % subbuf_pages;
1287
1288        if (this_end >= nonpad_end) {
1289            spd.nr_pages++;
1290            break;
1291        }
1292    }
1293
1294    ret = 0;
1295    if (!spd.nr_pages)
1296        goto out;
1297
1298    ret = *nonpad_ret = splice_to_pipe(pipe, &spd);
1299    if (ret < 0 || ret < total_len)
1300        goto out;
1301
1302        if (read_start + ret == nonpad_end)
1303                ret += padding;
1304
1305out:
1306    splice_shrink_spd(&spd);
1307    return ret;
1308}
1309
1310static ssize_t relay_file_splice_read(struct file *in,
1311                      loff_t *ppos,
1312                      struct pipe_inode_info *pipe,
1313                      size_t len,
1314                      unsigned int flags)
1315{
1316    ssize_t spliced;
1317    int ret;
1318    int nonpad_ret = 0;
1319
1320    ret = 0;
1321    spliced = 0;
1322
1323    while (len && !spliced) {
1324        ret = subbuf_splice_actor(in, ppos, pipe, len, flags, &nonpad_ret);
1325        if (ret < 0)
1326            break;
1327        else if (!ret) {
1328            if (flags & SPLICE_F_NONBLOCK)
1329                ret = -EAGAIN;
1330            break;
1331        }
1332
1333        *ppos += ret;
1334        if (ret > len)
1335            len = 0;
1336        else
1337            len -= ret;
1338        spliced += nonpad_ret;
1339        nonpad_ret = 0;
1340    }
1341
1342    if (spliced)
1343        return spliced;
1344
1345    return ret;
1346}
1347
1348const struct file_operations relay_file_operations = {
1349    .open = relay_file_open,
1350    .poll = relay_file_poll,
1351    .mmap = relay_file_mmap,
1352    .read = relay_file_read,
1353    .llseek = no_llseek,
1354    .release = relay_file_release,
1355    .splice_read = relay_file_splice_read,
1356};
1357EXPORT_SYMBOL_GPL(relay_file_operations);
1358
1359static __init int relay_init(void)
1360{
1361
1362    hotcpu_notifier(relay_hotcpu_callback, 0);
1363    return 0;
1364}
1365
1366early_initcall(relay_init);
1367

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