2 * "splice": joining two ropes together by interweaving their strands.
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.
8 * The traditional unix read/write is extended with a "splice()" operation
9 * that transfers data buffers to or from a pipe buffer.
11 * Named by Larry McVoy, original implementation from Linus, extended by
12 * Jens to support splicing to files and fixing the initial implementation
15 * Copyright (C) 2005 Jens Axboe <axboe@suse.de>
16 * Copyright (C) 2005 Linus Torvalds <torvalds@osdl.org>
20 #include <linux/file.h>
21 #include <linux/pagemap.h>
22 #include <linux/pipe_fs_i.h>
23 #include <linux/mm_inline.h>
24 #include <linux/swap.h>
25 #include <linux/module.h>
28 * Passed to the actors
31 unsigned int len, total_len; /* current and remaining length */
32 unsigned int flags; /* splice flags */
33 struct file *file; /* file to read/write */
34 loff_t pos; /* file position */
37 static int page_cache_pipe_buf_steal(struct pipe_inode_info *info,
38 struct pipe_buffer *buf)
40 struct page *page = buf->page;
42 WARN_ON(!PageLocked(page));
43 WARN_ON(!PageUptodate(page));
45 if (!remove_mapping(page_mapping(page), page))
49 struct zone *zone = page_zone(page);
51 spin_lock_irq(&zone->lru_lock);
52 BUG_ON(!PageLRU(page));
54 del_page_from_lru(zone, page);
55 spin_unlock_irq(&zone->lru_lock);
62 static void page_cache_pipe_buf_release(struct pipe_inode_info *info,
63 struct pipe_buffer *buf)
65 page_cache_release(buf->page);
70 static void *page_cache_pipe_buf_map(struct file *file,
71 struct pipe_inode_info *info,
72 struct pipe_buffer *buf)
74 struct page *page = buf->page;
78 if (!PageUptodate(page)) {
85 return ERR_PTR(-ENODATA);
88 return kmap(buf->page);
91 static void page_cache_pipe_buf_unmap(struct pipe_inode_info *info,
92 struct pipe_buffer *buf)
95 unlock_page(buf->page);
99 static struct pipe_buf_operations page_cache_pipe_buf_ops = {
101 .map = page_cache_pipe_buf_map,
102 .unmap = page_cache_pipe_buf_unmap,
103 .release = page_cache_pipe_buf_release,
104 .steal = page_cache_pipe_buf_steal,
107 static ssize_t move_to_pipe(struct inode *inode, struct page **pages,
108 int nr_pages, unsigned long offset,
109 unsigned long len, unsigned int flags)
111 struct pipe_inode_info *info;
112 int ret, do_wakeup, i;
118 mutex_lock(PIPE_MUTEX(*inode));
120 info = inode->i_pipe;
124 if (!PIPE_READERS(*inode)) {
125 send_sig(SIGPIPE, current, 0);
132 if (bufs < PIPE_BUFFERS) {
133 int newbuf = (info->curbuf + bufs) & (PIPE_BUFFERS - 1);
134 struct pipe_buffer *buf = info->bufs + newbuf;
135 struct page *page = pages[i++];
136 unsigned long this_len;
138 this_len = PAGE_CACHE_SIZE - offset;
143 buf->offset = offset;
145 buf->ops = &page_cache_pipe_buf_ops;
146 info->nrbufs = ++bufs;
156 if (bufs < PIPE_BUFFERS)
162 if (flags & SPLICE_F_NONBLOCK) {
168 if (signal_pending(current)) {
175 wake_up_interruptible_sync(PIPE_WAIT(*inode));
176 kill_fasync(PIPE_FASYNC_READERS(*inode), SIGIO,
181 PIPE_WAITING_WRITERS(*inode)++;
183 PIPE_WAITING_WRITERS(*inode)--;
186 mutex_unlock(PIPE_MUTEX(*inode));
189 wake_up_interruptible(PIPE_WAIT(*inode));
190 kill_fasync(PIPE_FASYNC_READERS(*inode), SIGIO, POLL_IN);
194 page_cache_release(pages[i++]);
199 static int __generic_file_splice_read(struct file *in, struct inode *pipe,
200 size_t len, unsigned int flags)
202 struct address_space *mapping = in->f_mapping;
203 unsigned int offset, nr_pages;
204 struct page *pages[PIPE_BUFFERS], *shadow[PIPE_BUFFERS];
209 index = in->f_pos >> PAGE_CACHE_SHIFT;
210 offset = in->f_pos & ~PAGE_CACHE_MASK;
211 nr_pages = (len + offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
213 if (nr_pages > PIPE_BUFFERS)
214 nr_pages = PIPE_BUFFERS;
217 * initiate read-ahead on this page range
219 do_page_cache_readahead(mapping, in, index, nr_pages);
222 * Get as many pages from the page cache as possible..
223 * Start IO on the page cache entries we create (we
224 * can assume that any pre-existing ones we find have
225 * already had IO started on them).
227 i = find_get_pages(mapping, index, nr_pages, pages);
230 * common case - we found all pages and they are contiguous,
233 if (i && (pages[i - 1]->index == index + i - 1))
237 * fill shadow[] with pages at the right locations, so we only
240 memset(shadow, 0, i * sizeof(struct page *));
241 for (j = 0, pidx = index; j < i; pidx++, j++)
242 shadow[pages[j]->index - pidx] = pages[j];
245 * now fill in the holes
247 for (i = 0, pidx = index; i < nr_pages; pidx++, i++) {
254 * no page there, look one up / create it
256 page = find_or_create_page(mapping, pidx,
257 mapping_gfp_mask(mapping));
261 if (PageUptodate(page))
264 error = mapping->a_ops->readpage(in, page);
266 if (unlikely(error)) {
267 page_cache_release(page);
275 for (i = 0; i < nr_pages; i++) {
277 page_cache_release(shadow[i]);
282 memcpy(pages, shadow, i * sizeof(struct page *));
285 * Now we splice them into the pipe..
288 return move_to_pipe(pipe, pages, i, offset, len, flags);
291 ssize_t generic_file_splice_read(struct file *in, struct inode *pipe,
292 size_t len, unsigned int flags)
300 ret = __generic_file_splice_read(in, pipe, len, flags);
309 if (!(flags & SPLICE_F_NONBLOCK))
322 * Send 'len' bytes to socket from 'file' at position 'pos' using sendpage().
324 static int pipe_to_sendpage(struct pipe_inode_info *info,
325 struct pipe_buffer *buf, struct splice_desc *sd)
327 struct file *file = sd->file;
328 loff_t pos = sd->pos;
334 * sub-optimal, but we are limited by the pipe ->map. we don't
335 * need a kmap'ed buffer here, we just want to make sure we
336 * have the page pinned if the pipe page originates from the
339 ptr = buf->ops->map(file, info, buf);
343 offset = pos & ~PAGE_CACHE_MASK;
345 ret = file->f_op->sendpage(file, buf->page, offset, sd->len, &pos,
346 sd->len < sd->total_len);
348 buf->ops->unmap(info, buf);
356 * This is a little more tricky than the file -> pipe splicing. There are
357 * basically three cases:
359 * - Destination page already exists in the address space and there
360 * are users of it. For that case we have no other option that
361 * copying the data. Tough luck.
362 * - Destination page already exists in the address space, but there
363 * are no users of it. Make sure it's uptodate, then drop it. Fall
364 * through to last case.
365 * - Destination page does not exist, we can add the pipe page to
366 * the page cache and avoid the copy.
368 * For now we just do the slower thing and always copy pages over, it's
369 * easier than migrating pages from the pipe to the target file. For the
370 * case of doing file | file splicing, the migrate approach had some LRU
373 static int pipe_to_file(struct pipe_inode_info *info, struct pipe_buffer *buf,
374 struct splice_desc *sd)
376 struct file *file = sd->file;
377 struct address_space *mapping = file->f_mapping;
385 * after this, page will be locked and unmapped
387 src = buf->ops->map(file, info, buf);
391 index = sd->pos >> PAGE_CACHE_SHIFT;
392 offset = sd->pos & ~PAGE_CACHE_MASK;
395 * reuse buf page, if SPLICE_F_MOVE is set
397 if (sd->flags & SPLICE_F_MOVE) {
398 if (buf->ops->steal(info, buf))
402 if (add_to_page_cache_lru(page, mapping, index,
403 mapping_gfp_mask(mapping)))
408 page = find_or_create_page(mapping, index,
409 mapping_gfp_mask(mapping));
414 * If the page is uptodate, it is also locked. If it isn't
415 * uptodate, we can mark it uptodate if we are filling the
416 * full page. Otherwise we need to read it in first...
418 if (!PageUptodate(page)) {
419 if (sd->len < PAGE_CACHE_SIZE) {
420 ret = mapping->a_ops->readpage(file, page);
426 if (!PageUptodate(page)) {
428 * page got invalidated, repeat
430 if (!page->mapping) {
432 page_cache_release(page);
439 WARN_ON(!PageLocked(page));
440 SetPageUptodate(page);
445 ret = mapping->a_ops->prepare_write(file, page, 0, sd->len);
450 char *dst = kmap_atomic(page, KM_USER0);
452 memcpy(dst + offset, src + buf->offset, sd->len);
453 flush_dcache_page(page);
454 kunmap_atomic(dst, KM_USER0);
457 ret = mapping->a_ops->commit_write(file, page, 0, sd->len);
461 set_page_dirty(page);
462 ret = write_one_page(page, 0);
467 page_cache_release(page);
468 buf->ops->unmap(info, buf);
472 typedef int (splice_actor)(struct pipe_inode_info *, struct pipe_buffer *,
473 struct splice_desc *);
475 static ssize_t move_from_pipe(struct inode *inode, struct file *out,
476 size_t len, unsigned int flags,
479 struct pipe_inode_info *info;
480 int ret, do_wakeup, err;
481 struct splice_desc sd;
491 mutex_lock(PIPE_MUTEX(*inode));
493 info = inode->i_pipe;
495 int bufs = info->nrbufs;
498 int curbuf = info->curbuf;
499 struct pipe_buffer *buf = info->bufs + curbuf;
500 struct pipe_buf_operations *ops = buf->ops;
503 if (sd.len > sd.total_len)
504 sd.len = sd.total_len;
506 err = actor(info, buf, &sd);
508 if (!ret && err != -ENODATA)
515 buf->offset += sd.len;
519 ops->release(info, buf);
520 curbuf = (curbuf + 1) & (PIPE_BUFFERS - 1);
521 info->curbuf = curbuf;
522 info->nrbufs = --bufs;
527 sd.total_len -= sd.len;
534 if (!PIPE_WRITERS(*inode))
536 if (!PIPE_WAITING_WRITERS(*inode)) {
541 if (flags & SPLICE_F_NONBLOCK) {
547 if (signal_pending(current)) {
554 wake_up_interruptible_sync(PIPE_WAIT(*inode));
555 kill_fasync(PIPE_FASYNC_WRITERS(*inode),SIGIO,POLL_OUT);
562 mutex_unlock(PIPE_MUTEX(*inode));
565 wake_up_interruptible(PIPE_WAIT(*inode));
566 kill_fasync(PIPE_FASYNC_WRITERS(*inode), SIGIO, POLL_OUT);
569 mutex_lock(&out->f_mapping->host->i_mutex);
571 mutex_unlock(&out->f_mapping->host->i_mutex);
576 ssize_t generic_file_splice_write(struct inode *inode, struct file *out,
577 size_t len, unsigned int flags)
579 return move_from_pipe(inode, out, len, flags, pipe_to_file);
582 ssize_t generic_splice_sendpage(struct inode *inode, struct file *out,
583 size_t len, unsigned int flags)
585 return move_from_pipe(inode, out, len, flags, pipe_to_sendpage);
588 EXPORT_SYMBOL(generic_file_splice_write);
589 EXPORT_SYMBOL(generic_file_splice_read);
591 static long do_splice_from(struct inode *pipe, struct file *out, size_t len,
597 if (!out->f_op || !out->f_op->splice_write)
600 if (!(out->f_mode & FMODE_WRITE))
604 ret = rw_verify_area(WRITE, out, &pos, len);
605 if (unlikely(ret < 0))
608 return out->f_op->splice_write(pipe, out, len, flags);
611 static long do_splice_to(struct file *in, struct inode *pipe, size_t len,
614 loff_t pos, isize, left;
617 if (!in->f_op || !in->f_op->splice_read)
620 if (!(in->f_mode & FMODE_READ))
624 ret = rw_verify_area(READ, in, &pos, len);
625 if (unlikely(ret < 0))
628 isize = i_size_read(in->f_mapping->host);
629 if (unlikely(in->f_pos >= isize))
632 left = isize - in->f_pos;
636 return in->f_op->splice_read(in, pipe, len, flags);
639 static long do_splice(struct file *in, struct file *out, size_t len,
644 pipe = in->f_dentry->d_inode;
646 return do_splice_from(pipe, out, len, flags);
648 pipe = out->f_dentry->d_inode;
650 return do_splice_to(in, pipe, len, flags);
655 asmlinkage long sys_splice(int fdin, int fdout, size_t len, unsigned int flags)
658 struct file *in, *out;
659 int fput_in, fput_out;
665 in = fget_light(fdin, &fput_in);
667 if (in->f_mode & FMODE_READ) {
668 out = fget_light(fdout, &fput_out);
670 if (out->f_mode & FMODE_WRITE)
671 error = do_splice(in, out, len, flags);
672 fput_light(out, fput_out);
676 fput_light(in, fput_in);