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authorJens Axboe <axboe@suse.de>2006-03-30 08:15:30 -0500
committerLinus Torvalds <torvalds@g5.osdl.org>2006-03-30 15:28:18 -0500
commit5274f052e7b3dbd81935772eb551dfd0325dfa9d (patch)
treec79f813ec513660edb6f1e4a75cb366c6b84f53f /fs/splice.c
parent5d4fe2c1ce83c3e967ccc1ba3d580c1a5603a866 (diff)
[PATCH] Introduce sys_splice() system call
This adds support for the sys_splice system call. Using a pipe as a transport, it can connect to files or sockets (latter as output only). From the splice.c comments: "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. Signed-off-by: Jens Axboe <axboe@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'fs/splice.c')
-rw-r--r--fs/splice.c612
1 files changed, 612 insertions, 0 deletions
diff --git a/fs/splice.c b/fs/splice.c
new file mode 100644
index 000000000000..efa47c1c4e13
--- /dev/null
+++ b/fs/splice.c
@@ -0,0 +1,612 @@
1/*
2 * "splice": joining two ropes together by interweaving their strands.
3 *
4 * This is the "extended pipe" functionality, where a pipe is used as
5 * an arbitrary in-memory buffer. Think of a pipe as a small kernel
6 * buffer that you can use to transfer data from one end to the other.
7 *
8 * The traditional unix read/write is extended with a "splice()" operation
9 * that transfers data buffers to or from a pipe buffer.
10 *
11 * Named by Larry McVoy, original implementation from Linus, extended by
12 * Jens to support splicing to files and fixing the initial implementation
13 * bugs.
14 *
15 * Copyright (C) 2005 Jens Axboe <axboe@suse.de>
16 * Copyright (C) 2005 Linus Torvalds <torvalds@osdl.org>
17 *
18 */
19#include <linux/fs.h>
20#include <linux/file.h>
21#include <linux/pagemap.h>
22#include <linux/pipe_fs_i.h>
23#include <linux/mm_inline.h>
24
25/*
26 * Passed to the actors
27 */
28struct splice_desc {
29 unsigned int len, total_len; /* current and remaining length */
30 unsigned int flags; /* splice flags */
31 struct file *file; /* file to read/write */
32 loff_t pos; /* file position */
33};
34
35static void page_cache_pipe_buf_release(struct pipe_inode_info *info,
36 struct pipe_buffer *buf)
37{
38 page_cache_release(buf->page);
39 buf->page = NULL;
40}
41
42static void *page_cache_pipe_buf_map(struct file *file,
43 struct pipe_inode_info *info,
44 struct pipe_buffer *buf)
45{
46 struct page *page = buf->page;
47
48 lock_page(page);
49
50 if (!PageUptodate(page)) {
51 unlock_page(page);
52 return ERR_PTR(-EIO);
53 }
54
55 if (!page->mapping) {
56 unlock_page(page);
57 return ERR_PTR(-ENODATA);
58 }
59
60 return kmap(buf->page);
61}
62
63static void page_cache_pipe_buf_unmap(struct pipe_inode_info *info,
64 struct pipe_buffer *buf)
65{
66 unlock_page(buf->page);
67 kunmap(buf->page);
68}
69
70static struct pipe_buf_operations page_cache_pipe_buf_ops = {
71 .can_merge = 0,
72 .map = page_cache_pipe_buf_map,
73 .unmap = page_cache_pipe_buf_unmap,
74 .release = page_cache_pipe_buf_release,
75};
76
77static ssize_t move_to_pipe(struct inode *inode, struct page **pages,
78 int nr_pages, unsigned long offset,
79 unsigned long len)
80{
81 struct pipe_inode_info *info;
82 int ret, do_wakeup, i;
83
84 ret = 0;
85 do_wakeup = 0;
86 i = 0;
87
88 mutex_lock(PIPE_MUTEX(*inode));
89
90 info = inode->i_pipe;
91 for (;;) {
92 int bufs;
93
94 if (!PIPE_READERS(*inode)) {
95 send_sig(SIGPIPE, current, 0);
96 if (!ret)
97 ret = -EPIPE;
98 break;
99 }
100
101 bufs = info->nrbufs;
102 if (bufs < PIPE_BUFFERS) {
103 int newbuf = (info->curbuf + bufs) & (PIPE_BUFFERS - 1);
104 struct pipe_buffer *buf = info->bufs + newbuf;
105 struct page *page = pages[i++];
106 unsigned long this_len;
107
108 this_len = PAGE_CACHE_SIZE - offset;
109 if (this_len > len)
110 this_len = len;
111
112 buf->page = page;
113 buf->offset = offset;
114 buf->len = this_len;
115 buf->ops = &page_cache_pipe_buf_ops;
116 info->nrbufs = ++bufs;
117 do_wakeup = 1;
118
119 ret += this_len;
120 len -= this_len;
121 offset = 0;
122 if (!--nr_pages)
123 break;
124 if (!len)
125 break;
126 if (bufs < PIPE_BUFFERS)
127 continue;
128
129 break;
130 }
131
132 if (signal_pending(current)) {
133 if (!ret)
134 ret = -ERESTARTSYS;
135 break;
136 }
137
138 if (do_wakeup) {
139 wake_up_interruptible_sync(PIPE_WAIT(*inode));
140 kill_fasync(PIPE_FASYNC_READERS(*inode), SIGIO,
141 POLL_IN);
142 do_wakeup = 0;
143 }
144
145 PIPE_WAITING_WRITERS(*inode)++;
146 pipe_wait(inode);
147 PIPE_WAITING_WRITERS(*inode)--;
148 }
149
150 mutex_unlock(PIPE_MUTEX(*inode));
151
152 if (do_wakeup) {
153 wake_up_interruptible(PIPE_WAIT(*inode));
154 kill_fasync(PIPE_FASYNC_READERS(*inode), SIGIO, POLL_IN);
155 }
156
157 while (i < nr_pages)
158 page_cache_release(pages[i++]);
159
160 return ret;
161}
162
163static int __generic_file_splice_read(struct file *in, struct inode *pipe,
164 size_t len)
165{
166 struct address_space *mapping = in->f_mapping;
167 unsigned int offset, nr_pages;
168 struct page *pages[PIPE_BUFFERS], *shadow[PIPE_BUFFERS];
169 struct page *page;
170 pgoff_t index, pidx;
171 int i, j;
172
173 index = in->f_pos >> PAGE_CACHE_SHIFT;
174 offset = in->f_pos & ~PAGE_CACHE_MASK;
175 nr_pages = (len + offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
176
177 if (nr_pages > PIPE_BUFFERS)
178 nr_pages = PIPE_BUFFERS;
179
180 /*
181 * initiate read-ahead on this page range
182 */
183 do_page_cache_readahead(mapping, in, index, nr_pages);
184
185 /*
186 * Get as many pages from the page cache as possible..
187 * Start IO on the page cache entries we create (we
188 * can assume that any pre-existing ones we find have
189 * already had IO started on them).
190 */
191 i = find_get_pages(mapping, index, nr_pages, pages);
192
193 /*
194 * common case - we found all pages and they are contiguous,
195 * kick them off
196 */
197 if (i && (pages[i - 1]->index == index + i - 1))
198 goto splice_them;
199
200 /*
201 * fill shadow[] with pages at the right locations, so we only
202 * have to fill holes
203 */
204 memset(shadow, 0, i * sizeof(struct page *));
205 for (j = 0, pidx = index; j < i; pidx++, j++)
206 shadow[pages[j]->index - pidx] = pages[j];
207
208 /*
209 * now fill in the holes
210 */
211 for (i = 0, pidx = index; i < nr_pages; pidx++, i++) {
212 int error;
213
214 if (shadow[i])
215 continue;
216
217 /*
218 * no page there, look one up / create it
219 */
220 page = find_or_create_page(mapping, pidx,
221 mapping_gfp_mask(mapping));
222 if (!page)
223 break;
224
225 if (PageUptodate(page))
226 unlock_page(page);
227 else {
228 error = mapping->a_ops->readpage(in, page);
229
230 if (unlikely(error)) {
231 page_cache_release(page);
232 break;
233 }
234 }
235 shadow[i] = page;
236 }
237
238 if (!i) {
239 for (i = 0; i < nr_pages; i++) {
240 if (shadow[i])
241 page_cache_release(shadow[i]);
242 }
243 return 0;
244 }
245
246 memcpy(pages, shadow, i * sizeof(struct page *));
247
248 /*
249 * Now we splice them into the pipe..
250 */
251splice_them:
252 return move_to_pipe(pipe, pages, i, offset, len);
253}
254
255ssize_t generic_file_splice_read(struct file *in, struct inode *pipe,
256 size_t len, unsigned int flags)
257{
258 ssize_t spliced;
259 int ret;
260
261 ret = 0;
262 spliced = 0;
263 while (len) {
264 ret = __generic_file_splice_read(in, pipe, len);
265
266 if (ret <= 0)
267 break;
268
269 in->f_pos += ret;
270 len -= ret;
271 spliced += ret;
272 }
273
274 if (spliced)
275 return spliced;
276
277 return ret;
278}
279
280/*
281 * Send 'len' bytes to socket from 'file' at position 'pos' using sendpage().
282 */
283static int pipe_to_sendpage(struct pipe_inode_info *info,
284 struct pipe_buffer *buf, struct splice_desc *sd)
285{
286 struct file *file = sd->file;
287 loff_t pos = sd->pos;
288 unsigned int offset;
289 ssize_t ret;
290 void *ptr;
291
292 /*
293 * sub-optimal, but we are limited by the pipe ->map. we don't
294 * need a kmap'ed buffer here, we just want to make sure we
295 * have the page pinned if the pipe page originates from the
296 * page cache
297 */
298 ptr = buf->ops->map(file, info, buf);
299 if (IS_ERR(ptr))
300 return PTR_ERR(ptr);
301
302 offset = pos & ~PAGE_CACHE_MASK;
303
304 ret = file->f_op->sendpage(file, buf->page, offset, sd->len, &pos,
305 sd->len < sd->total_len);
306
307 buf->ops->unmap(info, buf);
308 if (ret == sd->len)
309 return 0;
310
311 return -EIO;
312}
313
314/*
315 * This is a little more tricky than the file -> pipe splicing. There are
316 * basically three cases:
317 *
318 * - Destination page already exists in the address space and there
319 * are users of it. For that case we have no other option that
320 * copying the data. Tough luck.
321 * - Destination page already exists in the address space, but there
322 * are no users of it. Make sure it's uptodate, then drop it. Fall
323 * through to last case.
324 * - Destination page does not exist, we can add the pipe page to
325 * the page cache and avoid the copy.
326 *
327 * For now we just do the slower thing and always copy pages over, it's
328 * easier than migrating pages from the pipe to the target file. For the
329 * case of doing file | file splicing, the migrate approach had some LRU
330 * nastiness...
331 */
332static int pipe_to_file(struct pipe_inode_info *info, struct pipe_buffer *buf,
333 struct splice_desc *sd)
334{
335 struct file *file = sd->file;
336 struct address_space *mapping = file->f_mapping;
337 unsigned int offset;
338 struct page *page;
339 char *src, *dst;
340 pgoff_t index;
341 int ret;
342
343 /*
344 * after this, page will be locked and unmapped
345 */
346 src = buf->ops->map(file, info, buf);
347 if (IS_ERR(src))
348 return PTR_ERR(src);
349
350 index = sd->pos >> PAGE_CACHE_SHIFT;
351 offset = sd->pos & ~PAGE_CACHE_MASK;
352
353find_page:
354 ret = -ENOMEM;
355 page = find_or_create_page(mapping, index, mapping_gfp_mask(mapping));
356 if (!page)
357 goto out;
358
359 /*
360 * If the page is uptodate, it is also locked. If it isn't
361 * uptodate, we can mark it uptodate if we are filling the
362 * full page. Otherwise we need to read it in first...
363 */
364 if (!PageUptodate(page)) {
365 if (sd->len < PAGE_CACHE_SIZE) {
366 ret = mapping->a_ops->readpage(file, page);
367 if (unlikely(ret))
368 goto out;
369
370 lock_page(page);
371
372 if (!PageUptodate(page)) {
373 /*
374 * page got invalidated, repeat
375 */
376 if (!page->mapping) {
377 unlock_page(page);
378 page_cache_release(page);
379 goto find_page;
380 }
381 ret = -EIO;
382 goto out;
383 }
384 } else {
385 WARN_ON(!PageLocked(page));
386 SetPageUptodate(page);
387 }
388 }
389
390 ret = mapping->a_ops->prepare_write(file, page, 0, sd->len);
391 if (ret)
392 goto out;
393
394 dst = kmap_atomic(page, KM_USER0);
395 memcpy(dst + offset, src + buf->offset, sd->len);
396 flush_dcache_page(page);
397 kunmap_atomic(dst, KM_USER0);
398
399 ret = mapping->a_ops->commit_write(file, page, 0, sd->len);
400 if (ret < 0)
401 goto out;
402
403 set_page_dirty(page);
404 ret = write_one_page(page, 0);
405out:
406 if (ret < 0)
407 unlock_page(page);
408 page_cache_release(page);
409 buf->ops->unmap(info, buf);
410 return ret;
411}
412
413typedef int (splice_actor)(struct pipe_inode_info *, struct pipe_buffer *,
414 struct splice_desc *);
415
416static ssize_t move_from_pipe(struct inode *inode, struct file *out,
417 size_t len, unsigned int flags,
418 splice_actor *actor)
419{
420 struct pipe_inode_info *info;
421 int ret, do_wakeup, err;
422 struct splice_desc sd;
423
424 ret = 0;
425 do_wakeup = 0;
426
427 sd.total_len = len;
428 sd.flags = flags;
429 sd.file = out;
430 sd.pos = out->f_pos;
431
432 mutex_lock(PIPE_MUTEX(*inode));
433
434 info = inode->i_pipe;
435 for (;;) {
436 int bufs = info->nrbufs;
437
438 if (bufs) {
439 int curbuf = info->curbuf;
440 struct pipe_buffer *buf = info->bufs + curbuf;
441 struct pipe_buf_operations *ops = buf->ops;
442
443 sd.len = buf->len;
444 if (sd.len > sd.total_len)
445 sd.len = sd.total_len;
446
447 err = actor(info, buf, &sd);
448 if (err) {
449 if (!ret && err != -ENODATA)
450 ret = err;
451
452 break;
453 }
454
455 ret += sd.len;
456 buf->offset += sd.len;
457 buf->len -= sd.len;
458 if (!buf->len) {
459 buf->ops = NULL;
460 ops->release(info, buf);
461 curbuf = (curbuf + 1) & (PIPE_BUFFERS - 1);
462 info->curbuf = curbuf;
463 info->nrbufs = --bufs;
464 do_wakeup = 1;
465 }
466
467 sd.pos += sd.len;
468 sd.total_len -= sd.len;
469 if (!sd.total_len)
470 break;
471 }
472
473 if (bufs)
474 continue;
475 if (!PIPE_WRITERS(*inode))
476 break;
477 if (!PIPE_WAITING_WRITERS(*inode)) {
478 if (ret)
479 break;
480 }
481
482 if (signal_pending(current)) {
483 if (!ret)
484 ret = -ERESTARTSYS;
485 break;
486 }
487
488 if (do_wakeup) {
489 wake_up_interruptible_sync(PIPE_WAIT(*inode));
490 kill_fasync(PIPE_FASYNC_WRITERS(*inode),SIGIO,POLL_OUT);
491 do_wakeup = 0;
492 }
493
494 pipe_wait(inode);
495 }
496
497 mutex_unlock(PIPE_MUTEX(*inode));
498
499 if (do_wakeup) {
500 wake_up_interruptible(PIPE_WAIT(*inode));
501 kill_fasync(PIPE_FASYNC_WRITERS(*inode), SIGIO, POLL_OUT);
502 }
503
504 mutex_lock(&out->f_mapping->host->i_mutex);
505 out->f_pos = sd.pos;
506 mutex_unlock(&out->f_mapping->host->i_mutex);
507 return ret;
508
509}
510
511ssize_t generic_file_splice_write(struct inode *inode, struct file *out,
512 size_t len, unsigned int flags)
513{
514 return move_from_pipe(inode, out, len, flags, pipe_to_file);
515}
516
517ssize_t generic_splice_sendpage(struct inode *inode, struct file *out,
518 size_t len, unsigned int flags)
519{
520 return move_from_pipe(inode, out, len, flags, pipe_to_sendpage);
521}
522
523static long do_splice_from(struct inode *pipe, struct file *out, size_t len,
524 unsigned int flags)
525{
526 loff_t pos;
527 int ret;
528
529 if (!out->f_op || !out->f_op->splice_write)
530 return -EINVAL;
531
532 if (!(out->f_mode & FMODE_WRITE))
533 return -EBADF;
534
535 pos = out->f_pos;
536 ret = rw_verify_area(WRITE, out, &pos, len);
537 if (unlikely(ret < 0))
538 return ret;
539
540 return out->f_op->splice_write(pipe, out, len, flags);
541}
542
543static long do_splice_to(struct file *in, struct inode *pipe, size_t len,
544 unsigned int flags)
545{
546 loff_t pos, isize, left;
547 int ret;
548
549 if (!in->f_op || !in->f_op->splice_read)
550 return -EINVAL;
551
552 if (!(in->f_mode & FMODE_READ))
553 return -EBADF;
554
555 pos = in->f_pos;
556 ret = rw_verify_area(READ, in, &pos, len);
557 if (unlikely(ret < 0))
558 return ret;
559
560 isize = i_size_read(in->f_mapping->host);
561 if (unlikely(in->f_pos >= isize))
562 return 0;
563
564 left = isize - in->f_pos;
565 if (left < len)
566 len = left;
567
568 return in->f_op->splice_read(in, pipe, len, flags);
569}
570
571static long do_splice(struct file *in, struct file *out, size_t len,
572 unsigned int flags)
573{
574 struct inode *pipe;
575
576 pipe = in->f_dentry->d_inode;
577 if (pipe->i_pipe)
578 return do_splice_from(pipe, out, len, flags);
579
580 pipe = out->f_dentry->d_inode;
581 if (pipe->i_pipe)
582 return do_splice_to(in, pipe, len, flags);
583
584 return -EINVAL;
585}
586
587asmlinkage long sys_splice(int fdin, int fdout, size_t len, unsigned int flags)
588{
589 long error;
590 struct file *in, *out;
591 int fput_in, fput_out;
592
593 if (unlikely(!len))
594 return 0;
595
596 error = -EBADF;
597 in = fget_light(fdin, &fput_in);
598 if (in) {
599 if (in->f_mode & FMODE_READ) {
600 out = fget_light(fdout, &fput_out);
601 if (out) {
602 if (out->f_mode & FMODE_WRITE)
603 error = do_splice(in, out, len, flags);
604 fput_light(out, fput_out);
605 }
606 }
607
608 fput_light(in, fput_in);
609 }
610
611 return error;
612}