summaryrefslogtreecommitdiffstats
path: root/fs/splice.c
blob: 7c2bbf18d7a7c3622679bbf6e6a7f0bc0a78c7fa (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
/*
 * "splice": joining two ropes together by interweaving their strands.
 *
 * This is the "extended pipe" functionality, where a pipe is used as
 * an arbitrary in-memory buffer. Think of a pipe as a small kernel
 * buffer that you can use to transfer data from one end to the other.
 *
 * The traditional unix read/write is extended with a "splice()" operation
 * that transfers data buffers to or from a pipe buffer.
 *
 * Named by Larry McVoy, original implementation from Linus, extended by
 * Jens to support splicing to files and fixing the initial implementation
 * bugs.
 *
 * Copyright (C) 2005 Jens Axboe <axboe@suse.de>
 * Copyright (C) 2005 Linus Torvalds <torvalds@osdl.org>
 *
 */
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/pagemap.h>
#include <linux/pipe_fs_i.h>
#include <linux/mm_inline.h>
#include <linux/swap.h>
#include <linux/module.h>

/*
 * Passed to the actors
 */
struct splice_desc {
	unsigned int len, total_len;	/* current and remaining length */
	unsigned int flags;		/* splice flags */
	struct file *file;		/* file to read/write */
	loff_t pos;			/* file position */
};

static int page_cache_pipe_buf_steal(struct pipe_inode_info *info,
				     struct pipe_buffer *buf)
{
	struct page *page = buf->page;

	WARN_ON(!PageLocked(page));
	WARN_ON(!PageUptodate(page));

	if (!remove_mapping(page_mapping(page), page))
		return 1;

	if (PageLRU(page)) {
		struct zone *zone = page_zone(page);

		spin_lock_irq(&zone->lru_lock);
		BUG_ON(!PageLRU(page));
		__ClearPageLRU(page);
		del_page_from_lru(zone, page);
		spin_unlock_irq(&zone->lru_lock);
	}

	buf->stolen = 1;
	return 0;
}

static void page_cache_pipe_buf_release(struct pipe_inode_info *info,
					struct pipe_buffer *buf)
{
	page_cache_release(buf->page);
	buf->page = NULL;
	buf->stolen = 0;
}

static void *page_cache_pipe_buf_map(struct file *file,
				     struct pipe_inode_info *info,
				     struct pipe_buffer *buf)
{
	struct page *page = buf->page;

	lock_page(page);

	if (!PageUptodate(page)) {
		unlock_page(page);
		return ERR_PTR(-EIO);
	}

	if (!page->mapping) {
		unlock_page(page);
		return ERR_PTR(-ENODATA);
	}

	return kmap(buf->page);
}

static void page_cache_pipe_buf_unmap(struct pipe_inode_info *info,
				      struct pipe_buffer *buf)
{
	if (!buf->stolen)
		unlock_page(buf->page);
	kunmap(buf->page);
}

static struct pipe_buf_operations page_cache_pipe_buf_ops = {
	.can_merge = 0,
	.map = page_cache_pipe_buf_map,
	.unmap = page_cache_pipe_buf_unmap,
	.release = page_cache_pipe_buf_release,
	.steal = page_cache_pipe_buf_steal,
};

static ssize_t move_to_pipe(struct inode *inode, struct page **pages,
			    int nr_pages, unsigned long offset,
			    unsigned long len)
{
	struct pipe_inode_info *info;
	int ret, do_wakeup, i;

	ret = 0;
	do_wakeup = 0;
	i = 0;

	mutex_lock(PIPE_MUTEX(*inode));

	info = inode->i_pipe;
	for (;;) {
		int bufs;

		if (!PIPE_READERS(*inode)) {
			send_sig(SIGPIPE, current, 0);
			if (!ret)
				ret = -EPIPE;
			break;
		}

		bufs = info->nrbufs;
		if (bufs < PIPE_BUFFERS) {
			int newbuf = (info->curbuf + bufs) & (PIPE_BUFFERS - 1);
			struct pipe_buffer *buf = info->bufs + newbuf;
			struct page *page = pages[i++];
			unsigned long this_len;

			this_len = PAGE_CACHE_SIZE - offset;
			if (this_len > len)
				this_len = len;

			buf->page = page;
			buf->offset = offset;
			buf->len = this_len;
			buf->ops = &page_cache_pipe_buf_ops;
			info->nrbufs = ++bufs;
			do_wakeup = 1;

			ret += this_len;
			len -= this_len;
			offset = 0;
			if (!--nr_pages)
				break;
			if (!len)
				break;
			if (bufs < PIPE_BUFFERS)
				continue;

			break;
		}

		if (signal_pending(current)) {
			if (!ret)
				ret = -ERESTARTSYS;
			break;
		}

		if (do_wakeup) {
			wake_up_interruptible_sync(PIPE_WAIT(*inode));
			kill_fasync(PIPE_FASYNC_READERS(*inode), SIGIO,
				    POLL_IN);
			do_wakeup = 0;
		}

		PIPE_WAITING_WRITERS(*inode)++;
		pipe_wait(inode);
		PIPE_WAITING_WRITERS(*inode)--;
	}

	mutex_unlock(PIPE_MUTEX(*inode));

	if (do_wakeup) {
		wake_up_interruptible(PIPE_WAIT(*inode));
		kill_fasync(PIPE_FASYNC_READERS(*inode), SIGIO, POLL_IN);
	}

	while (i < nr_pages)
		page_cache_release(pages[i++]);

	return ret;
}

static int __generic_file_splice_read(struct file *in, struct inode *pipe,
				      size_t len)
{
	struct address_space *mapping = in->f_mapping;
	unsigned int offset, nr_pages;
	struct page *pages[PIPE_BUFFERS], *shadow[PIPE_BUFFERS];
	struct page *page;
	pgoff_t index, pidx;
	int i, j;

	index = in->f_pos >> PAGE_CACHE_SHIFT;
	offset = in->f_pos & ~PAGE_CACHE_MASK;
	nr_pages = (len + offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;

	if (nr_pages > PIPE_BUFFERS)
		nr_pages = PIPE_BUFFERS;

	/*
	 * initiate read-ahead on this page range
	 */
	do_page_cache_readahead(mapping, in, index, nr_pages);

	/*
	 * Get as many pages from the page cache as possible..
	 * Start IO on the page cache entries we create (we
	 * can assume that any pre-existing ones we find have
	 * already had IO started on them).
	 */
	i = find_get_pages(mapping, index, nr_pages, pages);

	/*
	 * common case - we found all pages and they are contiguous,
	 * kick them off
	 */
	if (i && (pages[i - 1]->index == index + i - 1))
		goto splice_them;

	/*
	 * fill shadow[] with pages at the right locations, so we only
	 * have to fill holes
	 */
	memset(shadow, 0, i * sizeof(struct page *));
	for (j = 0, pidx = index; j < i; pidx++, j++)
		shadow[pages[j]->index - pidx] = pages[j];

	/*
	 * now fill in the holes
	 */
	for (i = 0, pidx = index; i < nr_pages; pidx++, i++) {
		int error;

		if (shadow[i])
			continue;

		/*
		 * no page there, look one up / create it
		 */
		page = find_or_create_page(mapping, pidx,
						   mapping_gfp_mask(mapping));
		if (!page)
			break;

		if (PageUptodate(page))
			unlock_page(page);
		else {
			error = mapping->a_ops->readpage(in, page);

			if (unlikely(error)) {
				page_cache_release(page);
				break;
			}
		}
		shadow[i] = page;
	}

	if (!i) {
		for (i = 0; i < nr_pages; i++) {
			 if (shadow[i])
				page_cache_release(shadow[i]);
		}
		return 0;
	}

	memcpy(pages, shadow, i * sizeof(struct page *));

	/*
	 * Now we splice them into the pipe..
	 */
splice_them:
	return move_to_pipe(pipe, pages, i, offset, len);
}

ssize_t generic_file_splice_read(struct file *in, struct inode *pipe,
				 size_t len, unsigned int flags)
{
	ssize_t spliced;
	int ret;

	ret = 0;
	spliced = 0;
	while (len) {
		ret = __generic_file_splice_read(in, pipe, len);

		if (ret <= 0)
			break;

		in->f_pos += ret;
		len -= ret;
		spliced += ret;
	}

	if (spliced)
		return spliced;

	return ret;
}

/*
 * Send 'len' bytes to socket from 'file' at position 'pos' using sendpage().
 */
static int pipe_to_sendpage(struct pipe_inode_info *info,
			    struct pipe_buffer *buf, struct splice_desc *sd)
{
	struct file *file = sd->file;
	loff_t pos = sd->pos;
	unsigned int offset;
	ssize_t ret;
	void *ptr;

	/*
	 * sub-optimal, but we are limited by the pipe ->map. we don't
	 * need a kmap'ed buffer here, we just want to make sure we
	 * have the page pinned if the pipe page originates from the
	 * page cache
	 */
	ptr = buf->ops->map(file, info, buf);
	if (IS_ERR(ptr))
		return PTR_ERR(ptr);

	offset = pos & ~PAGE_CACHE_MASK;

	ret = file->f_op->sendpage(file, buf->page, offset, sd->len, &pos,
					sd->len < sd->total_len);

	buf->ops->unmap(info, buf);
	if (ret == sd->len)
		return 0;

	return -EIO;
}

/*
 * This is a little more tricky than the file -> pipe splicing. There are
 * basically three cases:
 *
 *	- Destination page already exists in the address space and there
 *	  are users of it. For that case we have no other option that
 *	  copying the data. Tough luck.
 *	- Destination page already exists in the address space, but there
 *	  are no users of it. Make sure it's uptodate, then drop it. Fall
 *	  through to last case.
 *	- Destination page does not exist, we can add the pipe page to
 *	  the page cache and avoid the copy.
 *
 * For now we just do the slower thing and always copy pages over, it's
 * easier than migrating pages from the pipe to the target file. For the
 * case of doing file | file splicing, the migrate approach had some LRU
 * nastiness...
 */
static int pipe_to_file(struct pipe_inode_info *info, struct pipe_buffer *buf,
			struct splice_desc *sd)
{
	struct file *file = sd->file;
	struct address_space *mapping = file->f_mapping;
	unsigned int offset;
	struct page *page;
	pgoff_t index;
	char *src;
	int ret;

	/*
	 * after this, page will be locked and unmapped
	 */
	src = buf->ops->map(file, info, buf);
	if (IS_ERR(src))
		return PTR_ERR(src);

	index = sd->pos >> PAGE_CACHE_SHIFT;
	offset = sd->pos & ~PAGE_CACHE_MASK;

	/*
	 * reuse buf page, if SPLICE_F_MOVE is set
	 */
	if (sd->flags & SPLICE_F_MOVE) {
		if (buf->ops->steal(info, buf))
			goto find_page;

		page = buf->page;
		if (add_to_page_cache_lru(page, mapping, index,
						mapping_gfp_mask(mapping)))
			goto find_page;
	} else {
find_page:
		ret = -ENOMEM;
		page = find_or_create_page(mapping, index,
						mapping_gfp_mask(mapping));
		if (!page)
			goto out;

		/*
		 * If the page is uptodate, it is also locked. If it isn't
		 * uptodate, we can mark it uptodate if we are filling the
		 * full page. Otherwise we need to read it in first...
		 */
		if (!PageUptodate(page)) {
			if (sd->len < PAGE_CACHE_SIZE) {
				ret = mapping->a_ops->readpage(file, page);
				if (unlikely(ret))
					goto out;

				lock_page(page);

				if (!PageUptodate(page)) {
					/*
					 * page got invalidated, repeat
					 */
					if (!page->mapping) {
						unlock_page(page);
						page_cache_release(page);
						goto find_page;
					}
					ret = -EIO;
					goto out;
				}
			} else {
				WARN_ON(!PageLocked(page));
				SetPageUptodate(page);
			}
		}
	}

	ret = mapping->a_ops->prepare_write(file, page, 0, sd->len);
	if (ret)
		goto out;

	if (!buf->stolen) {
		char *dst = kmap_atomic(page, KM_USER0);

		memcpy(dst + offset, src + buf->offset, sd->len);
		flush_dcache_page(page);
		kunmap_atomic(dst, KM_USER0);
	}

	ret = mapping->a_ops->commit_write(file, page, 0, sd->len);
	if (ret < 0)
		goto out;

	set_page_dirty(page);
	ret = write_one_page(page, 0);
out:
	if (ret < 0)
		unlock_page(page);
	if (!buf->stolen)
		page_cache_release(page);
	buf->ops->unmap(info, buf);
	return ret;
}

typedef int (splice_actor)(struct pipe_inode_info *, struct pipe_buffer *,
			   struct splice_desc *);

static ssize_t move_from_pipe(struct inode *inode, struct file *out,
			      size_t len, unsigned int flags,
			      splice_actor *actor)
{
	struct pipe_inode_info *info;
	int ret, do_wakeup, err;
	struct splice_desc sd;

	ret = 0;
	do_wakeup = 0;

	sd.total_len = len;
	sd.flags = flags;
	sd.file = out;
	sd.pos = out->f_pos;

	mutex_lock(PIPE_MUTEX(*inode));

	info = inode->i_pipe;
	for (;;) {
		int bufs = info->nrbufs;

		if (bufs) {
			int curbuf = info->curbuf;
			struct pipe_buffer *buf = info->bufs + curbuf;
			struct pipe_buf_operations *ops = buf->ops;

			sd.len = buf->len;
			if (sd.len > sd.total_len)
				sd.len = sd.total_len;

			err = actor(info, buf, &sd);
			if (err) {
				if (!ret && err != -ENODATA)
					ret = err;

				break;
			}

			ret += sd.len;
			buf->offset += sd.len;
			buf->len -= sd.len;
			if (!buf->len) {
				buf->ops = NULL;
				ops->release(info, buf);
				curbuf = (curbuf + 1) & (PIPE_BUFFERS - 1);
				info->curbuf = curbuf;
				info->nrbufs = --bufs;
				do_wakeup = 1;
			}

			sd.pos += sd.len;
			sd.total_len -= sd.len;
			if (!sd.total_len)
				break;
		}

		if (bufs)
			continue;
		if (!PIPE_WRITERS(*inode))
			break;
		if (!PIPE_WAITING_WRITERS(*inode)) {
			if (ret)
				break;
		}

		if (signal_pending(current)) {
			if (!ret)
				ret = -ERESTARTSYS;
			break;
		}

		if (do_wakeup) {
			wake_up_interruptible_sync(PIPE_WAIT(*inode));
			kill_fasync(PIPE_FASYNC_WRITERS(*inode),SIGIO,POLL_OUT);
			do_wakeup = 0;
		}

		pipe_wait(inode);
	}

	mutex_unlock(PIPE_MUTEX(*inode));

	if (do_wakeup) {
		wake_up_interruptible(PIPE_WAIT(*inode));
		kill_fasync(PIPE_FASYNC_WRITERS(*inode), SIGIO, POLL_OUT);
	}

	mutex_lock(&out->f_mapping->host->i_mutex);
	out->f_pos = sd.pos;
	mutex_unlock(&out->f_mapping->host->i_mutex);
	return ret;

}

ssize_t generic_file_splice_write(struct inode *inode, struct file *out,
				  size_t len, unsigned int flags)
{
	return move_from_pipe(inode, out, len, flags, pipe_to_file);
}

ssize_t generic_splice_sendpage(struct inode *inode, struct file *out,
				size_t len, unsigned int flags)
{
	return move_from_pipe(inode, out, len, flags, pipe_to_sendpage);
}

EXPORT_SYMBOL(generic_file_splice_write);
EXPORT_SYMBOL(generic_file_splice_read);

static long do_splice_from(struct inode *pipe, struct file *out, size_t len,
			   unsigned int flags)
{
	loff_t pos;
	int ret;

	if (!out->f_op || !out->f_op->splice_write)
		return -EINVAL;

	if (!(out->f_mode & FMODE_WRITE))
		return -EBADF;

	pos = out->f_pos;
	ret = rw_verify_area(WRITE, out, &pos, len);
	if (unlikely(ret < 0))
		return ret;

	return out->f_op->splice_write(pipe, out, len, flags);
}

static long do_splice_to(struct file *in, struct inode *pipe, size_t len,
			 unsigned int flags)
{
	loff_t pos, isize, left;
	int ret;

	if (!in->f_op || !in->f_op->splice_read)
		return -EINVAL;

	if (!(in->f_mode & FMODE_READ))
		return -EBADF;

	pos = in->f_pos;
	ret = rw_verify_area(READ, in, &pos, len);
	if (unlikely(ret < 0))
		return ret;

	isize = i_size_read(in->f_mapping->host);
	if (unlikely(in->f_pos >= isize))
		return 0;
	
	left = isize - in->f_pos;
	if (left < len)
		len = left;

	return in->f_op->splice_read(in, pipe, len, flags);
}

static long do_splice(struct file *in, struct file *out, size_t len,
		      unsigned int flags)
{
	struct inode *pipe;

	pipe = in->f_dentry->d_inode;
	if (pipe->i_pipe)
		return do_splice_from(pipe, out, len, flags);

	pipe = out->f_dentry->d_inode;
	if (pipe->i_pipe)
		return do_splice_to(in, pipe, len, flags);

	return -EINVAL;
}

asmlinkage long sys_splice(int fdin, int fdout, size_t len, unsigned int flags)
{
	long error;
	struct file *in, *out;
	int fput_in, fput_out;

	if (unlikely(!len))
		return 0;

	error = -EBADF;
	in = fget_light(fdin, &fput_in);
	if (in) {
		if (in->f_mode & FMODE_READ) {
			out = fget_light(fdout, &fput_out);
			if (out) {
				if (out->f_mode & FMODE_WRITE)
					error = do_splice(in, out, len, flags);
				fput_light(out, fput_out);
			}
		}

		fput_light(in, fput_in);
	}

	return error;
}
OpenPOWER on IntegriCloud