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-rw-r--r--fs/relayfs/relay.c431
1 files changed, 431 insertions, 0 deletions
diff --git a/fs/relayfs/relay.c b/fs/relayfs/relay.c
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1/*
2 * Public API and common code for RelayFS.
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 * This file is released under the GPL.
10 */
11
12#include <linux/errno.h>
13#include <linux/stddef.h>
14#include <linux/slab.h>
15#include <linux/module.h>
16#include <linux/string.h>
17#include <linux/relayfs_fs.h>
18#include "relay.h"
19#include "buffers.h"
20
21/**
22 * relay_buf_empty - boolean, is the channel buffer empty?
23 * @buf: channel buffer
24 *
25 * Returns 1 if the buffer is empty, 0 otherwise.
26 */
27int relay_buf_empty(struct rchan_buf *buf)
28{
29 return (buf->subbufs_produced - buf->subbufs_consumed) ? 0 : 1;
30}
31
32/**
33 * relay_buf_full - boolean, is the channel buffer full?
34 * @buf: channel buffer
35 *
36 * Returns 1 if the buffer is full, 0 otherwise.
37 */
38int relay_buf_full(struct rchan_buf *buf)
39{
40 size_t ready = buf->subbufs_produced - buf->subbufs_consumed;
41 return (ready >= buf->chan->n_subbufs) ? 1 : 0;
42}
43
44/*
45 * High-level relayfs kernel API and associated functions.
46 */
47
48/*
49 * rchan_callback implementations defining default channel behavior. Used
50 * in place of corresponding NULL values in client callback struct.
51 */
52
53/*
54 * subbuf_start() default callback. Does nothing.
55 */
56static int subbuf_start_default_callback (struct rchan_buf *buf,
57 void *subbuf,
58 void *prev_subbuf,
59 size_t prev_padding)
60{
61 if (relay_buf_full(buf))
62 return 0;
63
64 return 1;
65}
66
67/*
68 * buf_mapped() default callback. Does nothing.
69 */
70static void buf_mapped_default_callback(struct rchan_buf *buf,
71 struct file *filp)
72{
73}
74
75/*
76 * buf_unmapped() default callback. Does nothing.
77 */
78static void buf_unmapped_default_callback(struct rchan_buf *buf,
79 struct file *filp)
80{
81}
82
83/* relay channel default callbacks */
84static struct rchan_callbacks default_channel_callbacks = {
85 .subbuf_start = subbuf_start_default_callback,
86 .buf_mapped = buf_mapped_default_callback,
87 .buf_unmapped = buf_unmapped_default_callback,
88};
89
90/**
91 * wakeup_readers - wake up readers waiting on a channel
92 * @private: the channel buffer
93 *
94 * This is the work function used to defer reader waking. The
95 * reason waking is deferred is that calling directly from write
96 * causes problems if you're writing from say the scheduler.
97 */
98static void wakeup_readers(void *private)
99{
100 struct rchan_buf *buf = private;
101 wake_up_interruptible(&buf->read_wait);
102}
103
104/**
105 * __relay_reset - reset a channel buffer
106 * @buf: the channel buffer
107 * @init: 1 if this is a first-time initialization
108 *
109 * See relay_reset for description of effect.
110 */
111static inline void __relay_reset(struct rchan_buf *buf, unsigned int init)
112{
113 size_t i;
114
115 if (init) {
116 init_waitqueue_head(&buf->read_wait);
117 kref_init(&buf->kref);
118 INIT_WORK(&buf->wake_readers, NULL, NULL);
119 } else {
120 cancel_delayed_work(&buf->wake_readers);
121 flush_scheduled_work();
122 }
123
124 buf->subbufs_produced = 0;
125 buf->subbufs_consumed = 0;
126 buf->bytes_consumed = 0;
127 buf->finalized = 0;
128 buf->data = buf->start;
129 buf->offset = 0;
130
131 for (i = 0; i < buf->chan->n_subbufs; i++)
132 buf->padding[i] = 0;
133
134 buf->chan->cb->subbuf_start(buf, buf->data, NULL, 0);
135}
136
137/**
138 * relay_reset - reset the channel
139 * @chan: the channel
140 *
141 * This has the effect of erasing all data from all channel buffers
142 * and restarting the channel in its initial state. The buffers
143 * are not freed, so any mappings are still in effect.
144 *
145 * NOTE: Care should be taken that the channel isn't actually
146 * being used by anything when this call is made.
147 */
148void relay_reset(struct rchan *chan)
149{
150 unsigned int i;
151
152 if (!chan)
153 return;
154
155 for (i = 0; i < NR_CPUS; i++) {
156 if (!chan->buf[i])
157 continue;
158 __relay_reset(chan->buf[i], 0);
159 }
160}
161
162/**
163 * relay_open_buf - create a new channel buffer in relayfs
164 *
165 * Internal - used by relay_open().
166 */
167static struct rchan_buf *relay_open_buf(struct rchan *chan,
168 const char *filename,
169 struct dentry *parent)
170{
171 struct rchan_buf *buf;
172 struct dentry *dentry;
173
174 /* Create file in fs */
175 dentry = relayfs_create_file(filename, parent, S_IRUSR, chan);
176 if (!dentry)
177 return NULL;
178
179 buf = RELAYFS_I(dentry->d_inode)->buf;
180 buf->dentry = dentry;
181 __relay_reset(buf, 1);
182
183 return buf;
184}
185
186/**
187 * relay_close_buf - close a channel buffer
188 * @buf: channel buffer
189 *
190 * Marks the buffer finalized and restores the default callbacks.
191 * The channel buffer and channel buffer data structure are then freed
192 * automatically when the last reference is given up.
193 */
194static inline void relay_close_buf(struct rchan_buf *buf)
195{
196 buf->finalized = 1;
197 buf->chan->cb = &default_channel_callbacks;
198 cancel_delayed_work(&buf->wake_readers);
199 flush_scheduled_work();
200 kref_put(&buf->kref, relay_remove_buf);
201}
202
203static inline void setup_callbacks(struct rchan *chan,
204 struct rchan_callbacks *cb)
205{
206 if (!cb) {
207 chan->cb = &default_channel_callbacks;
208 return;
209 }
210
211 if (!cb->subbuf_start)
212 cb->subbuf_start = subbuf_start_default_callback;
213 if (!cb->buf_mapped)
214 cb->buf_mapped = buf_mapped_default_callback;
215 if (!cb->buf_unmapped)
216 cb->buf_unmapped = buf_unmapped_default_callback;
217 chan->cb = cb;
218}
219
220/**
221 * relay_open - create a new relayfs channel
222 * @base_filename: base name of files to create
223 * @parent: dentry of parent directory, NULL for root directory
224 * @subbuf_size: size of sub-buffers
225 * @n_subbufs: number of sub-buffers
226 * @cb: client callback functions
227 *
228 * Returns channel pointer if successful, NULL otherwise.
229 *
230 * Creates a channel buffer for each cpu using the sizes and
231 * attributes specified. The created channel buffer files
232 * will be named base_filename0...base_filenameN-1. File
233 * permissions will be S_IRUSR.
234 */
235struct rchan *relay_open(const char *base_filename,
236 struct dentry *parent,
237 size_t subbuf_size,
238 size_t n_subbufs,
239 struct rchan_callbacks *cb)
240{
241 unsigned int i;
242 struct rchan *chan;
243 char *tmpname;
244
245 if (!base_filename)
246 return NULL;
247
248 if (!(subbuf_size && n_subbufs))
249 return NULL;
250
251 chan = kcalloc(1, sizeof(struct rchan), GFP_KERNEL);
252 if (!chan)
253 return NULL;
254
255 chan->version = RELAYFS_CHANNEL_VERSION;
256 chan->n_subbufs = n_subbufs;
257 chan->subbuf_size = subbuf_size;
258 chan->alloc_size = FIX_SIZE(subbuf_size * n_subbufs);
259 setup_callbacks(chan, cb);
260 kref_init(&chan->kref);
261
262 tmpname = kmalloc(NAME_MAX + 1, GFP_KERNEL);
263 if (!tmpname)
264 goto free_chan;
265
266 for_each_online_cpu(i) {
267 sprintf(tmpname, "%s%d", base_filename, i);
268 chan->buf[i] = relay_open_buf(chan, tmpname, parent);
269 chan->buf[i]->cpu = i;
270 if (!chan->buf[i])
271 goto free_bufs;
272 }
273
274 kfree(tmpname);
275 return chan;
276
277free_bufs:
278 for (i = 0; i < NR_CPUS; i++) {
279 if (!chan->buf[i])
280 break;
281 relay_close_buf(chan->buf[i]);
282 }
283 kfree(tmpname);
284
285free_chan:
286 kref_put(&chan->kref, relay_destroy_channel);
287 return NULL;
288}
289
290/**
291 * relay_switch_subbuf - switch to a new sub-buffer
292 * @buf: channel buffer
293 * @length: size of current event
294 *
295 * Returns either the length passed in or 0 if full.
296
297 * Performs sub-buffer-switch tasks such as invoking callbacks,
298 * updating padding counts, waking up readers, etc.
299 */
300size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length)
301{
302 void *old, *new;
303 size_t old_subbuf, new_subbuf;
304
305 if (unlikely(length > buf->chan->subbuf_size))
306 goto toobig;
307
308 if (buf->offset != buf->chan->subbuf_size + 1) {
309 buf->prev_padding = buf->chan->subbuf_size - buf->offset;
310 old_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
311 buf->padding[old_subbuf] = buf->prev_padding;
312 buf->subbufs_produced++;
313 if (waitqueue_active(&buf->read_wait)) {
314 PREPARE_WORK(&buf->wake_readers, wakeup_readers, buf);
315 schedule_delayed_work(&buf->wake_readers, 1);
316 }
317 }
318
319 old = buf->data;
320 new_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
321 new = buf->start + new_subbuf * buf->chan->subbuf_size;
322 buf->offset = 0;
323 if (!buf->chan->cb->subbuf_start(buf, new, old, buf->prev_padding)) {
324 buf->offset = buf->chan->subbuf_size + 1;
325 return 0;
326 }
327 buf->data = new;
328 buf->padding[new_subbuf] = 0;
329
330 if (unlikely(length + buf->offset > buf->chan->subbuf_size))
331 goto toobig;
332
333 return length;
334
335toobig:
336 printk(KERN_WARNING "relayfs: event too large (%Zd)\n", length);
337 WARN_ON(1);
338 return 0;
339}
340
341/**
342 * relay_subbufs_consumed - update the buffer's sub-buffers-consumed count
343 * @chan: the channel
344 * @cpu: the cpu associated with the channel buffer to update
345 * @subbufs_consumed: number of sub-buffers to add to current buf's count
346 *
347 * Adds to the channel buffer's consumed sub-buffer count.
348 * subbufs_consumed should be the number of sub-buffers newly consumed,
349 * not the total consumed.
350 *
351 * NOTE: kernel clients don't need to call this function if the channel
352 * mode is 'overwrite'.
353 */
354void relay_subbufs_consumed(struct rchan *chan,
355 unsigned int cpu,
356 size_t subbufs_consumed)
357{
358 struct rchan_buf *buf;
359
360 if (!chan)
361 return;
362
363 if (cpu >= NR_CPUS || !chan->buf[cpu])
364 return;
365
366 buf = chan->buf[cpu];
367 buf->subbufs_consumed += subbufs_consumed;
368 if (buf->subbufs_consumed > buf->subbufs_produced)
369 buf->subbufs_consumed = buf->subbufs_produced;
370}
371
372/**
373 * relay_destroy_channel - free the channel struct
374 *
375 * Should only be called from kref_put().
376 */
377void relay_destroy_channel(struct kref *kref)
378{
379 struct rchan *chan = container_of(kref, struct rchan, kref);
380 kfree(chan);
381}
382
383/**
384 * relay_close - close the channel
385 * @chan: the channel
386 *
387 * Closes all channel buffers and frees the channel.
388 */
389void relay_close(struct rchan *chan)
390{
391 unsigned int i;
392
393 if (!chan)
394 return;
395
396 for (i = 0; i < NR_CPUS; i++) {
397 if (!chan->buf[i])
398 continue;
399 relay_close_buf(chan->buf[i]);
400 }
401
402 kref_put(&chan->kref, relay_destroy_channel);
403}
404
405/**
406 * relay_flush - close the channel
407 * @chan: the channel
408 *
409 * Flushes all channel buffers i.e. forces buffer switch.
410 */
411void relay_flush(struct rchan *chan)
412{
413 unsigned int i;
414
415 if (!chan)
416 return;
417
418 for (i = 0; i < NR_CPUS; i++) {
419 if (!chan->buf[i])
420 continue;
421 relay_switch_subbuf(chan->buf[i], 0);
422 }
423}
424
425EXPORT_SYMBOL_GPL(relay_open);
426EXPORT_SYMBOL_GPL(relay_close);
427EXPORT_SYMBOL_GPL(relay_flush);
428EXPORT_SYMBOL_GPL(relay_reset);
429EXPORT_SYMBOL_GPL(relay_subbufs_consumed);
430EXPORT_SYMBOL_GPL(relay_switch_subbuf);
431EXPORT_SYMBOL_GPL(relay_buf_full);