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, network, direct splicing, etc and
  13 * fixing lots of bugs.
  14 *
  15 * Copyright (C) 2005-2006 Jens Axboe <axboe@kernel.dk>
  16 * Copyright (C) 2005-2006 Linus Torvalds <torvalds@osdl.org>
  17 * Copyright (C) 2006 Ingo Molnar <mingo@elte.hu>
  18 *
  19 */
 
  20#include <linux/fs.h>
  21#include <linux/file.h>
  22#include <linux/pagemap.h>
  23#include <linux/splice.h>
  24#include <linux/memcontrol.h>
  25#include <linux/mm_inline.h>
  26#include <linux/swap.h>
  27#include <linux/writeback.h>
  28#include <linux/export.h>
  29#include <linux/syscalls.h>
  30#include <linux/uio.h>
  31#include <linux/security.h>
  32#include <linux/gfp.h>
  33#include <linux/socket.h>
  34#include <linux/compat.h>
 
  35#include "internal.h"
  36
  37/*
  38 * Attempt to steal a page from a pipe buffer. This should perhaps go into
  39 * a vm helper function, it's already simplified quite a bit by the
  40 * addition of remove_mapping(). If success is returned, the caller may
  41 * attempt to reuse this page for another destination.
  42 */
  43static int page_cache_pipe_buf_steal(struct pipe_inode_info *pipe,
  44				     struct pipe_buffer *buf)
  45{
  46	struct page *page = buf->page;
  47	struct address_space *mapping;
  48
  49	lock_page(page);
  50
  51	mapping = page_mapping(page);
  52	if (mapping) {
  53		WARN_ON(!PageUptodate(page));
  54
  55		/*
  56		 * At least for ext2 with nobh option, we need to wait on
  57		 * writeback completing on this page, since we'll remove it
  58		 * from the pagecache.  Otherwise truncate wont wait on the
  59		 * page, allowing the disk blocks to be reused by someone else
  60		 * before we actually wrote our data to them. fs corruption
  61		 * ensues.
  62		 */
  63		wait_on_page_writeback(page);
  64
  65		if (page_has_private(page) &&
  66		    !try_to_release_page(page, GFP_KERNEL))
  67			goto out_unlock;
  68
  69		/*
  70		 * If we succeeded in removing the mapping, set LRU flag
  71		 * and return good.
  72		 */
  73		if (remove_mapping(mapping, page)) {
  74			buf->flags |= PIPE_BUF_FLAG_LRU;
  75			return 0;
  76		}
  77	}
  78
  79	/*
  80	 * Raced with truncate or failed to remove page from current
  81	 * address space, unlock and return failure.
  82	 */
  83out_unlock:
  84	unlock_page(page);
  85	return 1;
  86}
  87
  88static void page_cache_pipe_buf_release(struct pipe_inode_info *pipe,
  89					struct pipe_buffer *buf)
  90{
  91	put_page(buf->page);
  92	buf->flags &= ~PIPE_BUF_FLAG_LRU;
  93}
  94
  95/*
  96 * Check whether the contents of buf is OK to access. Since the content
  97 * is a page cache page, IO may be in flight.
  98 */
  99static int page_cache_pipe_buf_confirm(struct pipe_inode_info *pipe,
 100				       struct pipe_buffer *buf)
 101{
 102	struct page *page = buf->page;
 103	int err;
 104
 105	if (!PageUptodate(page)) {
 106		lock_page(page);
 107
 108		/*
 109		 * Page got truncated/unhashed. This will cause a 0-byte
 110		 * splice, if this is the first page.
 111		 */
 112		if (!page->mapping) {
 113			err = -ENODATA;
 114			goto error;
 115		}
 116
 117		/*
 118		 * Uh oh, read-error from disk.
 119		 */
 120		if (!PageUptodate(page)) {
 121			err = -EIO;
 122			goto error;
 123		}
 124
 125		/*
 126		 * Page is ok afterall, we are done.
 127		 */
 128		unlock_page(page);
 129	}
 130
 131	return 0;
 132error:
 133	unlock_page(page);
 134	return err;
 135}
 136
 137const struct pipe_buf_operations page_cache_pipe_buf_ops = {
 138	.can_merge = 0,
 139	.confirm = page_cache_pipe_buf_confirm,
 140	.release = page_cache_pipe_buf_release,
 141	.steal = page_cache_pipe_buf_steal,
 142	.get = generic_pipe_buf_get,
 143};
 144
 145static int user_page_pipe_buf_steal(struct pipe_inode_info *pipe,
 146				    struct pipe_buffer *buf)
 147{
 148	if (!(buf->flags & PIPE_BUF_FLAG_GIFT))
 149		return 1;
 150
 151	buf->flags |= PIPE_BUF_FLAG_LRU;
 152	return generic_pipe_buf_steal(pipe, buf);
 153}
 154
 155static const struct pipe_buf_operations user_page_pipe_buf_ops = {
 156	.can_merge = 0,
 157	.confirm = generic_pipe_buf_confirm,
 158	.release = page_cache_pipe_buf_release,
 159	.steal = user_page_pipe_buf_steal,
 160	.get = generic_pipe_buf_get,
 161};
 162
 163static void wakeup_pipe_readers(struct pipe_inode_info *pipe)
 164{
 165	smp_mb();
 166	if (waitqueue_active(&pipe->wait))
 167		wake_up_interruptible(&pipe->wait);
 168	kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 169}
 170
 171/**
 172 * splice_to_pipe - fill passed data into a pipe
 173 * @pipe:	pipe to fill
 174 * @spd:	data to fill
 175 *
 176 * Description:
 177 *    @spd contains a map of pages and len/offset tuples, along with
 178 *    the struct pipe_buf_operations associated with these pages. This
 179 *    function will link that data to the pipe.
 180 *
 181 */
 182ssize_t splice_to_pipe(struct pipe_inode_info *pipe,
 183		       struct splice_pipe_desc *spd)
 184{
 185	unsigned int spd_pages = spd->nr_pages;
 186	int ret, do_wakeup, page_nr;
 
 
 
 187
 188	if (!spd_pages)
 189		return 0;
 190
 191	ret = 0;
 192	do_wakeup = 0;
 193	page_nr = 0;
 194
 195	pipe_lock(pipe);
 196
 197	for (;;) {
 198		if (!pipe->readers) {
 199			send_sig(SIGPIPE, current, 0);
 200			if (!ret)
 201				ret = -EPIPE;
 202			break;
 203		}
 204
 205		if (pipe->nrbufs < pipe->buffers) {
 206			int newbuf = (pipe->curbuf + pipe->nrbufs) & (pipe->buffers - 1);
 207			struct pipe_buffer *buf = pipe->bufs + newbuf;
 208
 209			buf->page = spd->pages[page_nr];
 210			buf->offset = spd->partial[page_nr].offset;
 211			buf->len = spd->partial[page_nr].len;
 212			buf->private = spd->partial[page_nr].private;
 213			buf->ops = spd->ops;
 214			if (spd->flags & SPLICE_F_GIFT)
 215				buf->flags |= PIPE_BUF_FLAG_GIFT;
 216
 217			pipe->nrbufs++;
 218			page_nr++;
 219			ret += buf->len;
 220
 221			if (pipe->files)
 222				do_wakeup = 1;
 223
 224			if (!--spd->nr_pages)
 225				break;
 226			if (pipe->nrbufs < pipe->buffers)
 227				continue;
 228
 229			break;
 230		}
 
 
 
 
 231
 232		if (spd->flags & SPLICE_F_NONBLOCK) {
 233			if (!ret)
 234				ret = -EAGAIN;
 235			break;
 236		}
 237
 238		if (signal_pending(current)) {
 239			if (!ret)
 240				ret = -ERESTARTSYS;
 241			break;
 242		}
 243
 244		if (do_wakeup) {
 245			smp_mb();
 246			if (waitqueue_active(&pipe->wait))
 247				wake_up_interruptible_sync(&pipe->wait);
 248			kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 249			do_wakeup = 0;
 250		}
 251
 252		pipe->waiting_writers++;
 253		pipe_wait(pipe);
 254		pipe->waiting_writers--;
 255	}
 256
 257	pipe_unlock(pipe);
 258
 259	if (do_wakeup)
 260		wakeup_pipe_readers(pipe);
 261
 
 262	while (page_nr < spd_pages)
 263		spd->spd_release(spd, page_nr++);
 264
 265	return ret;
 266}
 267EXPORT_SYMBOL_GPL(splice_to_pipe);
 268
 269void spd_release_page(struct splice_pipe_desc *spd, unsigned int i)
 270{
 271	put_page(spd->pages[i]);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 272}
 
 273
 274/*
 275 * Check if we need to grow the arrays holding pages and partial page
 276 * descriptions.
 277 */
 278int splice_grow_spd(const struct pipe_inode_info *pipe, struct splice_pipe_desc *spd)
 279{
 280	unsigned int buffers = ACCESS_ONCE(pipe->buffers);
 281
 282	spd->nr_pages_max = buffers;
 283	if (buffers <= PIPE_DEF_BUFFERS)
 284		return 0;
 285
 286	spd->pages = kmalloc(buffers * sizeof(struct page *), GFP_KERNEL);
 287	spd->partial = kmalloc(buffers * sizeof(struct partial_page), GFP_KERNEL);
 
 288
 289	if (spd->pages && spd->partial)
 290		return 0;
 291
 292	kfree(spd->pages);
 293	kfree(spd->partial);
 294	return -ENOMEM;
 295}
 296
 297void splice_shrink_spd(struct splice_pipe_desc *spd)
 298{
 299	if (spd->nr_pages_max <= PIPE_DEF_BUFFERS)
 300		return;
 301
 302	kfree(spd->pages);
 303	kfree(spd->partial);
 304}
 305
 306static int
 307__generic_file_splice_read(struct file *in, loff_t *ppos,
 308			   struct pipe_inode_info *pipe, size_t len,
 309			   unsigned int flags)
 310{
 311	struct address_space *mapping = in->f_mapping;
 312	unsigned int loff, nr_pages, req_pages;
 313	struct page *pages[PIPE_DEF_BUFFERS];
 314	struct partial_page partial[PIPE_DEF_BUFFERS];
 315	struct page *page;
 316	pgoff_t index, end_index;
 317	loff_t isize;
 318	int error, page_nr;
 319	struct splice_pipe_desc spd = {
 320		.pages = pages,
 321		.partial = partial,
 322		.nr_pages_max = PIPE_DEF_BUFFERS,
 323		.flags = flags,
 324		.ops = &page_cache_pipe_buf_ops,
 325		.spd_release = spd_release_page,
 326	};
 327
 328	if (splice_grow_spd(pipe, &spd))
 329		return -ENOMEM;
 330
 331	index = *ppos >> PAGE_SHIFT;
 332	loff = *ppos & ~PAGE_MASK;
 333	req_pages = (len + loff + PAGE_SIZE - 1) >> PAGE_SHIFT;
 334	nr_pages = min(req_pages, spd.nr_pages_max);
 335
 336	/*
 337	 * Lookup the (hopefully) full range of pages we need.
 338	 */
 339	spd.nr_pages = find_get_pages_contig(mapping, index, nr_pages, spd.pages);
 340	index += spd.nr_pages;
 341
 342	/*
 343	 * If find_get_pages_contig() returned fewer pages than we needed,
 344	 * readahead/allocate the rest and fill in the holes.
 345	 */
 346	if (spd.nr_pages < nr_pages)
 347		page_cache_sync_readahead(mapping, &in->f_ra, in,
 348				index, req_pages - spd.nr_pages);
 349
 350	error = 0;
 351	while (spd.nr_pages < nr_pages) {
 352		/*
 353		 * Page could be there, find_get_pages_contig() breaks on
 354		 * the first hole.
 355		 */
 356		page = find_get_page(mapping, index);
 357		if (!page) {
 358			/*
 359			 * page didn't exist, allocate one.
 360			 */
 361			page = page_cache_alloc_cold(mapping);
 362			if (!page)
 363				break;
 364
 365			error = add_to_page_cache_lru(page, mapping, index,
 366				   mapping_gfp_constraint(mapping, GFP_KERNEL));
 367			if (unlikely(error)) {
 368				put_page(page);
 369				if (error == -EEXIST)
 370					continue;
 371				break;
 372			}
 373			/*
 374			 * add_to_page_cache() locks the page, unlock it
 375			 * to avoid convoluting the logic below even more.
 376			 */
 377			unlock_page(page);
 378		}
 379
 380		spd.pages[spd.nr_pages++] = page;
 381		index++;
 382	}
 383
 384	/*
 385	 * Now loop over the map and see if we need to start IO on any
 386	 * pages, fill in the partial map, etc.
 387	 */
 388	index = *ppos >> PAGE_SHIFT;
 389	nr_pages = spd.nr_pages;
 390	spd.nr_pages = 0;
 391	for (page_nr = 0; page_nr < nr_pages; page_nr++) {
 392		unsigned int this_len;
 393
 394		if (!len)
 395			break;
 396
 397		/*
 398		 * this_len is the max we'll use from this page
 399		 */
 400		this_len = min_t(unsigned long, len, PAGE_SIZE - loff);
 401		page = spd.pages[page_nr];
 402
 403		if (PageReadahead(page))
 404			page_cache_async_readahead(mapping, &in->f_ra, in,
 405					page, index, req_pages - page_nr);
 406
 407		/*
 408		 * If the page isn't uptodate, we may need to start io on it
 409		 */
 410		if (!PageUptodate(page)) {
 411			lock_page(page);
 412
 413			/*
 414			 * Page was truncated, or invalidated by the
 415			 * filesystem.  Redo the find/create, but this time the
 416			 * page is kept locked, so there's no chance of another
 417			 * race with truncate/invalidate.
 418			 */
 419			if (!page->mapping) {
 420				unlock_page(page);
 421retry_lookup:
 422				page = find_or_create_page(mapping, index,
 423						mapping_gfp_mask(mapping));
 424
 425				if (!page) {
 426					error = -ENOMEM;
 427					break;
 428				}
 429				put_page(spd.pages[page_nr]);
 430				spd.pages[page_nr] = page;
 431			}
 432			/*
 433			 * page was already under io and is now done, great
 434			 */
 435			if (PageUptodate(page)) {
 436				unlock_page(page);
 437				goto fill_it;
 438			}
 439
 440			/*
 441			 * need to read in the page
 442			 */
 443			error = mapping->a_ops->readpage(in, page);
 444			if (unlikely(error)) {
 445				/*
 446				 * Re-lookup the page
 447				 */
 448				if (error == AOP_TRUNCATED_PAGE)
 449					goto retry_lookup;
 450
 451				break;
 452			}
 453		}
 454fill_it:
 455		/*
 456		 * i_size must be checked after PageUptodate.
 457		 */
 458		isize = i_size_read(mapping->host);
 459		end_index = (isize - 1) >> PAGE_SHIFT;
 460		if (unlikely(!isize || index > end_index))
 461			break;
 462
 463		/*
 464		 * if this is the last page, see if we need to shrink
 465		 * the length and stop
 466		 */
 467		if (end_index == index) {
 468			unsigned int plen;
 469
 470			/*
 471			 * max good bytes in this page
 472			 */
 473			plen = ((isize - 1) & ~PAGE_MASK) + 1;
 474			if (plen <= loff)
 475				break;
 476
 477			/*
 478			 * force quit after adding this page
 479			 */
 480			this_len = min(this_len, plen - loff);
 481			len = this_len;
 482		}
 483
 484		spd.partial[page_nr].offset = loff;
 485		spd.partial[page_nr].len = this_len;
 486		len -= this_len;
 487		loff = 0;
 488		spd.nr_pages++;
 489		index++;
 490	}
 491
 492	/*
 493	 * Release any pages at the end, if we quit early. 'page_nr' is how far
 494	 * we got, 'nr_pages' is how many pages are in the map.
 495	 */
 496	while (page_nr < nr_pages)
 497		put_page(spd.pages[page_nr++]);
 498	in->f_ra.prev_pos = (loff_t)index << PAGE_SHIFT;
 499
 500	if (spd.nr_pages)
 501		error = splice_to_pipe(pipe, &spd);
 502
 503	splice_shrink_spd(&spd);
 504	return error;
 505}
 506
 507/**
 508 * generic_file_splice_read - splice data from file to a pipe
 509 * @in:		file to splice from
 510 * @ppos:	position in @in
 511 * @pipe:	pipe to splice to
 512 * @len:	number of bytes to splice
 513 * @flags:	splice modifier flags
 514 *
 515 * Description:
 516 *    Will read pages from given file and fill them into a pipe. Can be
 517 *    used as long as the address_space operations for the source implements
 518 *    a readpage() hook.
 519 *
 520 */
 521ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
 522				 struct pipe_inode_info *pipe, size_t len,
 523				 unsigned int flags)
 524{
 525	loff_t isize, left;
 
 526	int ret;
 527
 528	if (IS_DAX(in->f_mapping->host))
 529		return default_file_splice_read(in, ppos, pipe, len, flags);
 530
 531	isize = i_size_read(in->f_mapping->host);
 532	if (unlikely(*ppos >= isize))
 533		return 0;
 534
 535	left = isize - *ppos;
 536	if (unlikely(left < len))
 537		len = left;
 538
 539	ret = __generic_file_splice_read(in, ppos, pipe, len, flags);
 540	if (ret > 0) {
 541		*ppos += ret;
 542		file_accessed(in);
 
 
 
 
 
 
 
 
 
 543	}
 544
 545	return ret;
 546}
 547EXPORT_SYMBOL(generic_file_splice_read);
 548
 549static const struct pipe_buf_operations default_pipe_buf_ops = {
 550	.can_merge = 0,
 551	.confirm = generic_pipe_buf_confirm,
 552	.release = generic_pipe_buf_release,
 553	.steal = generic_pipe_buf_steal,
 554	.get = generic_pipe_buf_get,
 555};
 556
 557static int generic_pipe_buf_nosteal(struct pipe_inode_info *pipe,
 558				    struct pipe_buffer *buf)
 559{
 560	return 1;
 561}
 562
 563/* Pipe buffer operations for a socket and similar. */
 564const struct pipe_buf_operations nosteal_pipe_buf_ops = {
 565	.can_merge = 0,
 566	.confirm = generic_pipe_buf_confirm,
 567	.release = generic_pipe_buf_release,
 568	.steal = generic_pipe_buf_nosteal,
 569	.get = generic_pipe_buf_get,
 570};
 571EXPORT_SYMBOL(nosteal_pipe_buf_ops);
 572
 573static ssize_t kernel_readv(struct file *file, const struct iovec *vec,
 574			    unsigned long vlen, loff_t offset)
 575{
 576	mm_segment_t old_fs;
 577	loff_t pos = offset;
 578	ssize_t res;
 579
 580	old_fs = get_fs();
 581	set_fs(get_ds());
 582	/* The cast to a user pointer is valid due to the set_fs() */
 583	res = vfs_readv(file, (const struct iovec __user *)vec, vlen, &pos, 0);
 584	set_fs(old_fs);
 585
 586	return res;
 587}
 588
 589ssize_t kernel_write(struct file *file, const char *buf, size_t count,
 590			    loff_t pos)
 591{
 592	mm_segment_t old_fs;
 593	ssize_t res;
 594
 595	old_fs = get_fs();
 596	set_fs(get_ds());
 597	/* The cast to a user pointer is valid due to the set_fs() */
 598	res = vfs_write(file, (__force const char __user *)buf, count, &pos);
 599	set_fs(old_fs);
 600
 601	return res;
 602}
 603EXPORT_SYMBOL(kernel_write);
 604
 605ssize_t default_file_splice_read(struct file *in, loff_t *ppos,
 606				 struct pipe_inode_info *pipe, size_t len,
 607				 unsigned int flags)
 608{
 609	unsigned int nr_pages;
 610	unsigned int nr_freed;
 611	size_t offset;
 612	struct page *pages[PIPE_DEF_BUFFERS];
 613	struct partial_page partial[PIPE_DEF_BUFFERS];
 614	struct iovec *vec, __vec[PIPE_DEF_BUFFERS];
 615	ssize_t res;
 616	size_t this_len;
 617	int error;
 618	int i;
 619	struct splice_pipe_desc spd = {
 620		.pages = pages,
 621		.partial = partial,
 622		.nr_pages_max = PIPE_DEF_BUFFERS,
 623		.flags = flags,
 624		.ops = &default_pipe_buf_ops,
 625		.spd_release = spd_release_page,
 626	};
 627
 628	if (splice_grow_spd(pipe, &spd))
 629		return -ENOMEM;
 630
 631	res = -ENOMEM;
 632	vec = __vec;
 633	if (spd.nr_pages_max > PIPE_DEF_BUFFERS) {
 634		vec = kmalloc(spd.nr_pages_max * sizeof(struct iovec), GFP_KERNEL);
 635		if (!vec)
 636			goto shrink_ret;
 637	}
 638
 639	offset = *ppos & ~PAGE_MASK;
 640	nr_pages = (len + offset + PAGE_SIZE - 1) >> PAGE_SHIFT;
 641
 642	for (i = 0; i < nr_pages && i < spd.nr_pages_max && len; i++) {
 643		struct page *page;
 644
 645		page = alloc_page(GFP_USER);
 646		error = -ENOMEM;
 647		if (!page)
 648			goto err;
 649
 650		this_len = min_t(size_t, len, PAGE_SIZE - offset);
 651		vec[i].iov_base = (void __user *) page_address(page);
 652		vec[i].iov_len = this_len;
 653		spd.pages[i] = page;
 654		spd.nr_pages++;
 655		len -= this_len;
 656		offset = 0;
 657	}
 658
 659	res = kernel_readv(in, vec, spd.nr_pages, *ppos);
 660	if (res < 0) {
 661		error = res;
 662		goto err;
 663	}
 664
 665	error = 0;
 666	if (!res)
 667		goto err;
 668
 669	nr_freed = 0;
 670	for (i = 0; i < spd.nr_pages; i++) {
 671		this_len = min_t(size_t, vec[i].iov_len, res);
 672		spd.partial[i].offset = 0;
 673		spd.partial[i].len = this_len;
 674		if (!this_len) {
 675			__free_page(spd.pages[i]);
 676			spd.pages[i] = NULL;
 677			nr_freed++;
 678		}
 679		res -= this_len;
 680	}
 681	spd.nr_pages -= nr_freed;
 682
 683	res = splice_to_pipe(pipe, &spd);
 684	if (res > 0)
 685		*ppos += res;
 686
 687shrink_ret:
 688	if (vec != __vec)
 689		kfree(vec);
 690	splice_shrink_spd(&spd);
 691	return res;
 692
 693err:
 694	for (i = 0; i < spd.nr_pages; i++)
 695		__free_page(spd.pages[i]);
 696
 697	res = error;
 698	goto shrink_ret;
 699}
 700EXPORT_SYMBOL(default_file_splice_read);
 701
 702/*
 703 * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
 704 * using sendpage(). Return the number of bytes sent.
 705 */
 706static int pipe_to_sendpage(struct pipe_inode_info *pipe,
 707			    struct pipe_buffer *buf, struct splice_desc *sd)
 708{
 709	struct file *file = sd->u.file;
 710	loff_t pos = sd->pos;
 711	int more;
 712
 713	if (!likely(file->f_op->sendpage))
 714		return -EINVAL;
 715
 716	more = (sd->flags & SPLICE_F_MORE) ? MSG_MORE : 0;
 717
 718	if (sd->len < sd->total_len && pipe->nrbufs > 1)
 
 719		more |= MSG_SENDPAGE_NOTLAST;
 720
 721	return file->f_op->sendpage(file, buf->page, buf->offset,
 722				    sd->len, &pos, more);
 723}
 724
 725static void wakeup_pipe_writers(struct pipe_inode_info *pipe)
 726{
 727	smp_mb();
 728	if (waitqueue_active(&pipe->wait))
 729		wake_up_interruptible(&pipe->wait);
 730	kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 731}
 732
 733/**
 734 * splice_from_pipe_feed - feed available data from a pipe to a file
 735 * @pipe:	pipe to splice from
 736 * @sd:		information to @actor
 737 * @actor:	handler that splices the data
 738 *
 739 * Description:
 740 *    This function loops over the pipe and calls @actor to do the
 741 *    actual moving of a single struct pipe_buffer to the desired
 742 *    destination.  It returns when there's no more buffers left in
 743 *    the pipe or if the requested number of bytes (@sd->total_len)
 744 *    have been copied.  It returns a positive number (one) if the
 745 *    pipe needs to be filled with more data, zero if the required
 746 *    number of bytes have been copied and -errno on error.
 747 *
 748 *    This, together with splice_from_pipe_{begin,end,next}, may be
 749 *    used to implement the functionality of __splice_from_pipe() when
 750 *    locking is required around copying the pipe buffers to the
 751 *    destination.
 752 */
 753static int splice_from_pipe_feed(struct pipe_inode_info *pipe, struct splice_desc *sd,
 754			  splice_actor *actor)
 755{
 
 
 
 756	int ret;
 757
 758	while (pipe->nrbufs) {
 759		struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
 760		const struct pipe_buf_operations *ops = buf->ops;
 761
 762		sd->len = buf->len;
 763		if (sd->len > sd->total_len)
 764			sd->len = sd->total_len;
 765
 766		ret = buf->ops->confirm(pipe, buf);
 767		if (unlikely(ret)) {
 768			if (ret == -ENODATA)
 769				ret = 0;
 770			return ret;
 771		}
 772
 773		ret = actor(pipe, buf, sd);
 774		if (ret <= 0)
 775			return ret;
 776
 777		buf->offset += ret;
 778		buf->len -= ret;
 779
 780		sd->num_spliced += ret;
 781		sd->len -= ret;
 782		sd->pos += ret;
 783		sd->total_len -= ret;
 784
 785		if (!buf->len) {
 786			buf->ops = NULL;
 787			ops->release(pipe, buf);
 788			pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1);
 789			pipe->nrbufs--;
 790			if (pipe->files)
 791				sd->need_wakeup = true;
 792		}
 793
 794		if (!sd->total_len)
 795			return 0;
 796	}
 797
 798	return 1;
 799}
 800
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 801/**
 802 * splice_from_pipe_next - wait for some data to splice from
 803 * @pipe:	pipe to splice from
 804 * @sd:		information about the splice operation
 805 *
 806 * Description:
 807 *    This function will wait for some data and return a positive
 808 *    value (one) if pipe buffers are available.  It will return zero
 809 *    or -errno if no more data needs to be spliced.
 810 */
 811static int splice_from_pipe_next(struct pipe_inode_info *pipe, struct splice_desc *sd)
 812{
 813	/*
 814	 * Check for signal early to make process killable when there are
 815	 * always buffers available
 816	 */
 817	if (signal_pending(current))
 818		return -ERESTARTSYS;
 819
 820	while (!pipe->nrbufs) {
 
 821		if (!pipe->writers)
 822			return 0;
 823
 824		if (!pipe->waiting_writers && sd->num_spliced)
 825			return 0;
 826
 827		if (sd->flags & SPLICE_F_NONBLOCK)
 828			return -EAGAIN;
 829
 830		if (signal_pending(current))
 831			return -ERESTARTSYS;
 832
 833		if (sd->need_wakeup) {
 834			wakeup_pipe_writers(pipe);
 835			sd->need_wakeup = false;
 836		}
 837
 838		pipe_wait(pipe);
 839	}
 840
 
 
 
 841	return 1;
 842}
 843
 844/**
 845 * splice_from_pipe_begin - start splicing from pipe
 846 * @sd:		information about the splice operation
 847 *
 848 * Description:
 849 *    This function should be called before a loop containing
 850 *    splice_from_pipe_next() and splice_from_pipe_feed() to
 851 *    initialize the necessary fields of @sd.
 852 */
 853static void splice_from_pipe_begin(struct splice_desc *sd)
 854{
 855	sd->num_spliced = 0;
 856	sd->need_wakeup = false;
 857}
 858
 859/**
 860 * splice_from_pipe_end - finish splicing from pipe
 861 * @pipe:	pipe to splice from
 862 * @sd:		information about the splice operation
 863 *
 864 * Description:
 865 *    This function will wake up pipe writers if necessary.  It should
 866 *    be called after a loop containing splice_from_pipe_next() and
 867 *    splice_from_pipe_feed().
 868 */
 869static void splice_from_pipe_end(struct pipe_inode_info *pipe, struct splice_desc *sd)
 870{
 871	if (sd->need_wakeup)
 872		wakeup_pipe_writers(pipe);
 873}
 874
 875/**
 876 * __splice_from_pipe - splice data from a pipe to given actor
 877 * @pipe:	pipe to splice from
 878 * @sd:		information to @actor
 879 * @actor:	handler that splices the data
 880 *
 881 * Description:
 882 *    This function does little more than loop over the pipe and call
 883 *    @actor to do the actual moving of a single struct pipe_buffer to
 884 *    the desired destination. See pipe_to_file, pipe_to_sendpage, or
 885 *    pipe_to_user.
 886 *
 887 */
 888ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd,
 889			   splice_actor *actor)
 890{
 891	int ret;
 892
 893	splice_from_pipe_begin(sd);
 894	do {
 895		cond_resched();
 896		ret = splice_from_pipe_next(pipe, sd);
 897		if (ret > 0)
 898			ret = splice_from_pipe_feed(pipe, sd, actor);
 899	} while (ret > 0);
 900	splice_from_pipe_end(pipe, sd);
 901
 902	return sd->num_spliced ? sd->num_spliced : ret;
 903}
 904EXPORT_SYMBOL(__splice_from_pipe);
 905
 906/**
 907 * splice_from_pipe - splice data from a pipe to a file
 908 * @pipe:	pipe to splice from
 909 * @out:	file to splice to
 910 * @ppos:	position in @out
 911 * @len:	how many bytes to splice
 912 * @flags:	splice modifier flags
 913 * @actor:	handler that splices the data
 914 *
 915 * Description:
 916 *    See __splice_from_pipe. This function locks the pipe inode,
 917 *    otherwise it's identical to __splice_from_pipe().
 918 *
 919 */
 920ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
 921			 loff_t *ppos, size_t len, unsigned int flags,
 922			 splice_actor *actor)
 923{
 924	ssize_t ret;
 925	struct splice_desc sd = {
 926		.total_len = len,
 927		.flags = flags,
 928		.pos = *ppos,
 929		.u.file = out,
 930	};
 931
 932	pipe_lock(pipe);
 933	ret = __splice_from_pipe(pipe, &sd, actor);
 934	pipe_unlock(pipe);
 935
 936	return ret;
 937}
 938
 939/**
 940 * iter_file_splice_write - splice data from a pipe to a file
 941 * @pipe:	pipe info
 942 * @out:	file to write to
 943 * @ppos:	position in @out
 944 * @len:	number of bytes to splice
 945 * @flags:	splice modifier flags
 946 *
 947 * Description:
 948 *    Will either move or copy pages (determined by @flags options) from
 949 *    the given pipe inode to the given file.
 950 *    This one is ->write_iter-based.
 951 *
 952 */
 953ssize_t
 954iter_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
 955			  loff_t *ppos, size_t len, unsigned int flags)
 956{
 957	struct splice_desc sd = {
 958		.total_len = len,
 959		.flags = flags,
 960		.pos = *ppos,
 961		.u.file = out,
 962	};
 963	int nbufs = pipe->buffers;
 964	struct bio_vec *array = kcalloc(nbufs, sizeof(struct bio_vec),
 965					GFP_KERNEL);
 966	ssize_t ret;
 967
 968	if (unlikely(!array))
 969		return -ENOMEM;
 970
 971	pipe_lock(pipe);
 972
 973	splice_from_pipe_begin(&sd);
 974	while (sd.total_len) {
 975		struct iov_iter from;
 
 976		size_t left;
 977		int n, idx;
 978
 979		ret = splice_from_pipe_next(pipe, &sd);
 980		if (ret <= 0)
 981			break;
 982
 983		if (unlikely(nbufs < pipe->buffers)) {
 984			kfree(array);
 985			nbufs = pipe->buffers;
 986			array = kcalloc(nbufs, sizeof(struct bio_vec),
 987					GFP_KERNEL);
 988			if (!array) {
 989				ret = -ENOMEM;
 990				break;
 991			}
 992		}
 993
 
 
 
 
 994		/* build the vector */
 995		left = sd.total_len;
 996		for (n = 0, idx = pipe->curbuf; left && n < pipe->nrbufs; n++, idx++) {
 997			struct pipe_buffer *buf = pipe->bufs + idx;
 998			size_t this_len = buf->len;
 999
1000			if (this_len > left)
1001				this_len = left;
1002
1003			if (idx == pipe->buffers - 1)
1004				idx = -1;
1005
1006			ret = buf->ops->confirm(pipe, buf);
1007			if (unlikely(ret)) {
1008				if (ret == -ENODATA)
1009					ret = 0;
1010				goto done;
1011			}
1012
1013			array[n].bv_page = buf->page;
1014			array[n].bv_len = this_len;
1015			array[n].bv_offset = buf->offset;
1016			left -= this_len;
 
1017		}
1018
1019		iov_iter_bvec(&from, ITER_BVEC | WRITE, array, n,
1020			      sd.total_len - left);
1021		ret = vfs_iter_write(out, &from, &sd.pos);
1022		if (ret <= 0)
1023			break;
1024
1025		sd.num_spliced += ret;
1026		sd.total_len -= ret;
1027		*ppos = sd.pos;
1028
1029		/* dismiss the fully eaten buffers, adjust the partial one */
 
1030		while (ret) {
1031			struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
1032			if (ret >= buf->len) {
1033				const struct pipe_buf_operations *ops = buf->ops;
1034				ret -= buf->len;
1035				buf->len = 0;
1036				buf->ops = NULL;
1037				ops->release(pipe, buf);
1038				pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1);
1039				pipe->nrbufs--;
1040				if (pipe->files)
1041					sd.need_wakeup = true;
1042			} else {
1043				buf->offset += ret;
1044				buf->len -= ret;
1045				ret = 0;
1046			}
1047		}
1048	}
1049done:
1050	kfree(array);
1051	splice_from_pipe_end(pipe, &sd);
1052
1053	pipe_unlock(pipe);
1054
1055	if (sd.num_spliced)
1056		ret = sd.num_spliced;
1057
1058	return ret;
1059}
1060
1061EXPORT_SYMBOL(iter_file_splice_write);
1062
1063static int write_pipe_buf(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
1064			  struct splice_desc *sd)
1065{
1066	int ret;
1067	void *data;
1068	loff_t tmp = sd->pos;
1069
1070	data = kmap(buf->page);
1071	ret = __kernel_write(sd->u.file, data + buf->offset, sd->len, &tmp);
1072	kunmap(buf->page);
1073
1074	return ret;
1075}
1076
1077static ssize_t default_file_splice_write(struct pipe_inode_info *pipe,
1078					 struct file *out, loff_t *ppos,
1079					 size_t len, unsigned int flags)
1080{
1081	ssize_t ret;
1082
1083	ret = splice_from_pipe(pipe, out, ppos, len, flags, write_pipe_buf);
1084	if (ret > 0)
1085		*ppos += ret;
1086
1087	return ret;
1088}
1089
1090/**
1091 * generic_splice_sendpage - splice data from a pipe to a socket
1092 * @pipe:	pipe to splice from
1093 * @out:	socket to write to
1094 * @ppos:	position in @out
1095 * @len:	number of bytes to splice
1096 * @flags:	splice modifier flags
1097 *
1098 * Description:
1099 *    Will send @len bytes from the pipe to a network socket. No data copying
1100 *    is involved.
1101 *
1102 */
1103ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
1104				loff_t *ppos, size_t len, unsigned int flags)
1105{
1106	return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
1107}
1108
1109EXPORT_SYMBOL(generic_splice_sendpage);
1110
 
 
 
 
 
 
 
 
1111/*
1112 * Attempt to initiate a splice from pipe to file.
1113 */
1114static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
1115			   loff_t *ppos, size_t len, unsigned int flags)
1116{
1117	ssize_t (*splice_write)(struct pipe_inode_info *, struct file *,
1118				loff_t *, size_t, unsigned int);
1119
1120	if (out->f_op->splice_write)
1121		splice_write = out->f_op->splice_write;
1122	else
1123		splice_write = default_file_splice_write;
1124
1125	return splice_write(pipe, out, ppos, len, flags);
1126}
1127
1128/*
1129 * Attempt to initiate a splice from a file to a pipe.
1130 */
1131static long do_splice_to(struct file *in, loff_t *ppos,
1132			 struct pipe_inode_info *pipe, size_t len,
1133			 unsigned int flags)
1134{
1135	ssize_t (*splice_read)(struct file *, loff_t *,
1136			       struct pipe_inode_info *, size_t, unsigned int);
1137	int ret;
1138
1139	if (unlikely(!(in->f_mode & FMODE_READ)))
1140		return -EBADF;
1141
 
 
 
 
1142	ret = rw_verify_area(READ, in, ppos, len);
1143	if (unlikely(ret < 0))
1144		return ret;
1145
1146	if (unlikely(len > MAX_RW_COUNT))
1147		len = MAX_RW_COUNT;
1148
1149	if (in->f_op->splice_read)
1150		splice_read = in->f_op->splice_read;
1151	else
1152		splice_read = default_file_splice_read;
1153
1154	return splice_read(in, ppos, pipe, len, flags);
1155}
1156
1157/**
1158 * splice_direct_to_actor - splices data directly between two non-pipes
1159 * @in:		file to splice from
1160 * @sd:		actor information on where to splice to
1161 * @actor:	handles the data splicing
1162 *
1163 * Description:
1164 *    This is a special case helper to splice directly between two
1165 *    points, without requiring an explicit pipe. Internally an allocated
1166 *    pipe is cached in the process, and reused during the lifetime of
1167 *    that process.
1168 *
1169 */
1170ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
1171			       splice_direct_actor *actor)
1172{
1173	struct pipe_inode_info *pipe;
1174	long ret, bytes;
1175	umode_t i_mode;
1176	size_t len;
1177	int i, flags, more;
1178
1179	/*
1180	 * We require the input being a regular file, as we don't want to
1181	 * randomly drop data for eg socket -> socket splicing. Use the
1182	 * piped splicing for that!
1183	 */
1184	i_mode = file_inode(in)->i_mode;
1185	if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode)))
1186		return -EINVAL;
1187
1188	/*
1189	 * neither in nor out is a pipe, setup an internal pipe attached to
1190	 * 'out' and transfer the wanted data from 'in' to 'out' through that
1191	 */
1192	pipe = current->splice_pipe;
1193	if (unlikely(!pipe)) {
1194		pipe = alloc_pipe_info();
1195		if (!pipe)
1196			return -ENOMEM;
1197
1198		/*
1199		 * We don't have an immediate reader, but we'll read the stuff
1200		 * out of the pipe right after the splice_to_pipe(). So set
1201		 * PIPE_READERS appropriately.
1202		 */
1203		pipe->readers = 1;
1204
1205		current->splice_pipe = pipe;
1206	}
1207
1208	/*
1209	 * Do the splice.
1210	 */
1211	ret = 0;
1212	bytes = 0;
1213	len = sd->total_len;
1214	flags = sd->flags;
1215
1216	/*
1217	 * Don't block on output, we have to drain the direct pipe.
1218	 */
1219	sd->flags &= ~SPLICE_F_NONBLOCK;
1220	more = sd->flags & SPLICE_F_MORE;
1221
 
 
1222	while (len) {
1223		size_t read_len;
1224		loff_t pos = sd->pos, prev_pos = pos;
1225
1226		ret = do_splice_to(in, &pos, pipe, len, flags);
1227		if (unlikely(ret <= 0))
1228			goto out_release;
1229
1230		read_len = ret;
1231		sd->total_len = read_len;
1232
1233		/*
1234		 * If more data is pending, set SPLICE_F_MORE
1235		 * If this is the last data and SPLICE_F_MORE was not set
1236		 * initially, clears it.
1237		 */
1238		if (read_len < len)
1239			sd->flags |= SPLICE_F_MORE;
1240		else if (!more)
1241			sd->flags &= ~SPLICE_F_MORE;
1242		/*
1243		 * NOTE: nonblocking mode only applies to the input. We
1244		 * must not do the output in nonblocking mode as then we
1245		 * could get stuck data in the internal pipe:
1246		 */
1247		ret = actor(pipe, sd);
1248		if (unlikely(ret <= 0)) {
1249			sd->pos = prev_pos;
1250			goto out_release;
1251		}
1252
1253		bytes += ret;
1254		len -= ret;
1255		sd->pos = pos;
1256
1257		if (ret < read_len) {
1258			sd->pos = prev_pos + ret;
1259			goto out_release;
1260		}
1261	}
1262
1263done:
1264	pipe->nrbufs = pipe->curbuf = 0;
1265	file_accessed(in);
1266	return bytes;
1267
1268out_release:
1269	/*
1270	 * If we did an incomplete transfer we must release
1271	 * the pipe buffers in question:
1272	 */
1273	for (i = 0; i < pipe->buffers; i++) {
1274		struct pipe_buffer *buf = pipe->bufs + i;
1275
1276		if (buf->ops) {
1277			buf->ops->release(pipe, buf);
1278			buf->ops = NULL;
1279		}
1280	}
1281
1282	if (!bytes)
1283		bytes = ret;
1284
1285	goto done;
1286}
1287EXPORT_SYMBOL(splice_direct_to_actor);
1288
1289static int direct_splice_actor(struct pipe_inode_info *pipe,
1290			       struct splice_desc *sd)
1291{
1292	struct file *file = sd->u.file;
1293
1294	return do_splice_from(pipe, file, sd->opos, sd->total_len,
1295			      sd->flags);
1296}
1297
1298/**
1299 * do_splice_direct - splices data directly between two files
1300 * @in:		file to splice from
1301 * @ppos:	input file offset
1302 * @out:	file to splice to
1303 * @opos:	output file offset
1304 * @len:	number of bytes to splice
1305 * @flags:	splice modifier flags
1306 *
1307 * Description:
1308 *    For use by do_sendfile(). splice can easily emulate sendfile, but
1309 *    doing it in the application would incur an extra system call
1310 *    (splice in + splice out, as compared to just sendfile()). So this helper
1311 *    can splice directly through a process-private pipe.
1312 *
1313 */
1314long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
1315		      loff_t *opos, size_t len, unsigned int flags)
1316{
1317	struct splice_desc sd = {
1318		.len		= len,
1319		.total_len	= len,
1320		.flags		= flags,
1321		.pos		= *ppos,
1322		.u.file		= out,
1323		.opos		= opos,
1324	};
1325	long ret;
1326
1327	if (unlikely(!(out->f_mode & FMODE_WRITE)))
1328		return -EBADF;
1329
1330	if (unlikely(out->f_flags & O_APPEND))
1331		return -EINVAL;
1332
1333	ret = rw_verify_area(WRITE, out, opos, len);
1334	if (unlikely(ret < 0))
1335		return ret;
1336
1337	ret = splice_direct_to_actor(in, &sd, direct_splice_actor);
1338	if (ret > 0)
1339		*ppos = sd.pos;
1340
1341	return ret;
1342}
1343EXPORT_SYMBOL(do_splice_direct);
1344
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1345static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1346			       struct pipe_inode_info *opipe,
1347			       size_t len, unsigned int flags);
1348
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1349/*
1350 * Determine where to splice to/from.
1351 */
1352static long do_splice(struct file *in, loff_t __user *off_in,
1353		      struct file *out, loff_t __user *off_out,
1354		      size_t len, unsigned int flags)
1355{
1356	struct pipe_inode_info *ipipe;
1357	struct pipe_inode_info *opipe;
1358	loff_t offset;
1359	long ret;
1360
1361	ipipe = get_pipe_info(in);
1362	opipe = get_pipe_info(out);
 
 
 
 
1363
1364	if (ipipe && opipe) {
1365		if (off_in || off_out)
1366			return -ESPIPE;
1367
1368		if (!(in->f_mode & FMODE_READ))
1369			return -EBADF;
1370
1371		if (!(out->f_mode & FMODE_WRITE))
1372			return -EBADF;
1373
1374		/* Splicing to self would be fun, but... */
1375		if (ipipe == opipe)
1376			return -EINVAL;
1377
 
 
 
1378		return splice_pipe_to_pipe(ipipe, opipe, len, flags);
1379	}
1380
1381	if (ipipe) {
1382		if (off_in)
1383			return -ESPIPE;
1384		if (off_out) {
1385			if (!(out->f_mode & FMODE_PWRITE))
1386				return -EINVAL;
1387			if (copy_from_user(&offset, off_out, sizeof(loff_t)))
1388				return -EFAULT;
1389		} else {
1390			offset = out->f_pos;
1391		}
1392
1393		if (unlikely(!(out->f_mode & FMODE_WRITE)))
1394			return -EBADF;
1395
1396		if (unlikely(out->f_flags & O_APPEND))
1397			return -EINVAL;
1398
1399		ret = rw_verify_area(WRITE, out, &offset, len);
1400		if (unlikely(ret < 0))
1401			return ret;
1402
 
 
 
1403		file_start_write(out);
1404		ret = do_splice_from(ipipe, out, &offset, len, flags);
1405		file_end_write(out);
1406
1407		if (!off_out)
1408			out->f_pos = offset;
1409		else if (copy_to_user(off_out, &offset, sizeof(loff_t)))
1410			ret = -EFAULT;
1411
1412		return ret;
1413	}
1414
1415	if (opipe) {
1416		if (off_out)
1417			return -ESPIPE;
1418		if (off_in) {
1419			if (!(in->f_mode & FMODE_PREAD))
1420				return -EINVAL;
1421			if (copy_from_user(&offset, off_in, sizeof(loff_t)))
1422				return -EFAULT;
1423		} else {
1424			offset = in->f_pos;
1425		}
1426
1427		ret = do_splice_to(in, &offset, opipe, len, flags);
 
1428
 
1429		if (!off_in)
1430			in->f_pos = offset;
1431		else if (copy_to_user(off_in, &offset, sizeof(loff_t)))
1432			ret = -EFAULT;
1433
1434		return ret;
1435	}
1436
1437	return -EINVAL;
1438}
1439
1440/*
1441 * Map an iov into an array of pages and offset/length tupples. With the
1442 * partial_page structure, we can map several non-contiguous ranges into
1443 * our ones pages[] map instead of splitting that operation into pieces.
1444 * Could easily be exported as a generic helper for other users, in which
1445 * case one would probably want to add a 'max_nr_pages' parameter as well.
1446 */
1447static int get_iovec_page_array(const struct iovec __user *iov,
1448				unsigned int nr_vecs, struct page **pages,
1449				struct partial_page *partial, bool aligned,
1450				unsigned int pipe_buffers)
1451{
1452	int buffers = 0, error = 0;
1453
1454	while (nr_vecs) {
1455		unsigned long off, npages;
1456		struct iovec entry;
1457		void __user *base;
1458		size_t len;
1459		int i;
1460
1461		error = -EFAULT;
1462		if (copy_from_user(&entry, iov, sizeof(entry)))
1463			break;
1464
1465		base = entry.iov_base;
1466		len = entry.iov_len;
 
 
1467
1468		/*
1469		 * Sanity check this iovec. 0 read succeeds.
1470		 */
1471		error = 0;
1472		if (unlikely(!len))
1473			break;
1474		error = -EFAULT;
1475		if (!access_ok(VERIFY_READ, base, len))
1476			break;
 
1477
1478		/*
1479		 * Get this base offset and number of pages, then map
1480		 * in the user pages.
1481		 */
1482		off = (unsigned long) base & ~PAGE_MASK;
1483
1484		/*
1485		 * If asked for alignment, the offset must be zero and the
1486		 * length a multiple of the PAGE_SIZE.
1487		 */
1488		error = -EINVAL;
1489		if (aligned && (off || len & ~PAGE_MASK))
1490			break;
1491
1492		npages = (off + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1493		if (npages > pipe_buffers - buffers)
1494			npages = pipe_buffers - buffers;
1495
1496		error = get_user_pages_fast((unsigned long)base, npages,
1497					0, &pages[buffers]);
 
 
 
 
 
 
 
 
1498
1499		if (unlikely(error <= 0))
 
 
 
 
 
 
 
 
1500			break;
1501
1502		/*
1503		 * Fill this contiguous range into the partial page map.
1504		 */
1505		for (i = 0; i < error; i++) {
1506			const int plen = min_t(size_t, len, PAGE_SIZE - off);
1507
1508			partial[buffers].offset = off;
1509			partial[buffers].len = plen;
1510
1511			off = 0;
1512			len -= plen;
1513			buffers++;
1514		}
1515
1516		/*
1517		 * We didn't complete this iov, stop here since it probably
1518		 * means we have to move some of this into a pipe to
1519		 * be able to continue.
1520		 */
1521		if (len)
1522			break;
1523
1524		/*
1525		 * Don't continue if we mapped fewer pages than we asked for,
1526		 * or if we mapped the max number of pages that we have
1527		 * room for.
1528		 */
1529		if (error < npages || buffers == pipe_buffers)
1530			break;
1531
1532		nr_vecs--;
1533		iov++;
 
1534	}
1535
1536	if (buffers)
1537		return buffers;
1538
1539	return error;
1540}
1541
1542static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
1543			struct splice_desc *sd)
1544{
1545	int n = copy_page_to_iter(buf->page, buf->offset, sd->len, sd->u.data);
1546	return n == sd->len ? n : -EFAULT;
1547}
1548
1549/*
1550 * For lack of a better implementation, implement vmsplice() to userspace
1551 * as a simple copy of the pipes pages to the user iov.
1552 */
1553static long vmsplice_to_user(struct file *file, const struct iovec __user *uiov,
1554			     unsigned long nr_segs, unsigned int flags)
1555{
1556	struct pipe_inode_info *pipe;
1557	struct splice_desc sd;
1558	long ret;
1559	struct iovec iovstack[UIO_FASTIOV];
1560	struct iovec *iov = iovstack;
1561	struct iov_iter iter;
 
1562
1563	pipe = get_pipe_info(file);
1564	if (!pipe)
1565		return -EBADF;
1566
1567	ret = import_iovec(READ, uiov, nr_segs,
1568			   ARRAY_SIZE(iovstack), &iov, &iter);
1569	if (ret < 0)
1570		return ret;
1571
1572	sd.total_len = iov_iter_count(&iter);
1573	sd.len = 0;
1574	sd.flags = flags;
1575	sd.u.data = &iter;
1576	sd.pos = 0;
1577
1578	if (sd.total_len) {
1579		pipe_lock(pipe);
1580		ret = __splice_from_pipe(pipe, &sd, pipe_to_user);
1581		pipe_unlock(pipe);
1582	}
1583
1584	kfree(iov);
1585	return ret;
1586}
1587
1588/*
1589 * vmsplice splices a user address range into a pipe. It can be thought of
1590 * as splice-from-memory, where the regular splice is splice-from-file (or
1591 * to file). In both cases the output is a pipe, naturally.
1592 */
1593static long vmsplice_to_pipe(struct file *file, const struct iovec __user *iov,
1594			     unsigned long nr_segs, unsigned int flags)
1595{
1596	struct pipe_inode_info *pipe;
1597	struct page *pages[PIPE_DEF_BUFFERS];
1598	struct partial_page partial[PIPE_DEF_BUFFERS];
1599	struct splice_pipe_desc spd = {
1600		.pages = pages,
1601		.partial = partial,
1602		.nr_pages_max = PIPE_DEF_BUFFERS,
1603		.flags = flags,
1604		.ops = &user_page_pipe_buf_ops,
1605		.spd_release = spd_release_page,
1606	};
1607	long ret;
1608
1609	pipe = get_pipe_info(file);
1610	if (!pipe)
1611		return -EBADF;
1612
1613	if (splice_grow_spd(pipe, &spd))
1614		return -ENOMEM;
1615
1616	spd.nr_pages = get_iovec_page_array(iov, nr_segs, spd.pages,
1617					    spd.partial, false,
1618					    spd.nr_pages_max);
1619	if (spd.nr_pages <= 0)
1620		ret = spd.nr_pages;
1621	else
1622		ret = splice_to_pipe(pipe, &spd);
1623
1624	splice_shrink_spd(&spd);
1625	return ret;
1626}
1627
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1628/*
1629 * Note that vmsplice only really supports true splicing _from_ user memory
1630 * to a pipe, not the other way around. Splicing from user memory is a simple
1631 * operation that can be supported without any funky alignment restrictions
1632 * or nasty vm tricks. We simply map in the user memory and fill them into
1633 * a pipe. The reverse isn't quite as easy, though. There are two possible
1634 * solutions for that:
1635 *
1636 *	- memcpy() the data internally, at which point we might as well just
1637 *	  do a regular read() on the buffer anyway.
1638 *	- Lots of nasty vm tricks, that are neither fast nor flexible (it
1639 *	  has restriction limitations on both ends of the pipe).
1640 *
1641 * Currently we punt and implement it as a normal copy, see pipe_to_user().
1642 *
1643 */
1644SYSCALL_DEFINE4(vmsplice, int, fd, const struct iovec __user *, iov,
1645		unsigned long, nr_segs, unsigned int, flags)
1646{
 
 
 
 
1647	struct fd f;
1648	long error;
1649
1650	if (unlikely(nr_segs > UIO_MAXIOV))
1651		return -EINVAL;
1652	else if (unlikely(!nr_segs))
1653		return 0;
1654
1655	error = -EBADF;
1656	f = fdget(fd);
1657	if (f.file) {
1658		if (f.file->f_mode & FMODE_WRITE)
1659			error = vmsplice_to_pipe(f.file, iov, nr_segs, flags);
1660		else if (f.file->f_mode & FMODE_READ)
1661			error = vmsplice_to_user(f.file, iov, nr_segs, flags);
 
 
 
1662
1663		fdput(f);
1664	}
 
 
 
 
1665
 
 
 
1666	return error;
1667}
1668
1669#ifdef CONFIG_COMPAT
1670COMPAT_SYSCALL_DEFINE4(vmsplice, int, fd, const struct compat_iovec __user *, iov32,
1671		    unsigned int, nr_segs, unsigned int, flags)
1672{
1673	unsigned i;
1674	struct iovec __user *iov;
1675	if (nr_segs > UIO_MAXIOV)
1676		return -EINVAL;
1677	iov = compat_alloc_user_space(nr_segs * sizeof(struct iovec));
1678	for (i = 0; i < nr_segs; i++) {
1679		struct compat_iovec v;
1680		if (get_user(v.iov_base, &iov32[i].iov_base) ||
1681		    get_user(v.iov_len, &iov32[i].iov_len) ||
1682		    put_user(compat_ptr(v.iov_base), &iov[i].iov_base) ||
1683		    put_user(v.iov_len, &iov[i].iov_len))
1684			return -EFAULT;
1685	}
1686	return sys_vmsplice(fd, iov, nr_segs, flags);
1687}
1688#endif
1689
1690SYSCALL_DEFINE6(splice, int, fd_in, loff_t __user *, off_in,
1691		int, fd_out, loff_t __user *, off_out,
1692		size_t, len, unsigned int, flags)
1693{
1694	struct fd in, out;
1695	long error;
1696
1697	if (unlikely(!len))
1698		return 0;
1699
 
 
 
1700	error = -EBADF;
1701	in = fdget(fd_in);
1702	if (in.file) {
1703		if (in.file->f_mode & FMODE_READ) {
1704			out = fdget(fd_out);
1705			if (out.file) {
1706				if (out.file->f_mode & FMODE_WRITE)
1707					error = do_splice(in.file, off_in,
1708							  out.file, off_out,
1709							  len, flags);
1710				fdput(out);
1711			}
1712		}
1713		fdput(in);
1714	}
1715	return error;
1716}
1717
1718/*
1719 * Make sure there's data to read. Wait for input if we can, otherwise
1720 * return an appropriate error.
1721 */
1722static int ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1723{
1724	int ret;
1725
1726	/*
1727	 * Check ->nrbufs without the inode lock first. This function
1728	 * is speculative anyways, so missing one is ok.
1729	 */
1730	if (pipe->nrbufs)
1731		return 0;
1732
1733	ret = 0;
1734	pipe_lock(pipe);
1735
1736	while (!pipe->nrbufs) {
1737		if (signal_pending(current)) {
1738			ret = -ERESTARTSYS;
1739			break;
1740		}
1741		if (!pipe->writers)
1742			break;
1743		if (!pipe->waiting_writers) {
1744			if (flags & SPLICE_F_NONBLOCK) {
1745				ret = -EAGAIN;
1746				break;
1747			}
1748		}
1749		pipe_wait(pipe);
1750	}
1751
1752	pipe_unlock(pipe);
1753	return ret;
1754}
1755
1756/*
1757 * Make sure there's writeable room. Wait for room if we can, otherwise
1758 * return an appropriate error.
1759 */
1760static int opipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1761{
1762	int ret;
1763
1764	/*
1765	 * Check ->nrbufs without the inode lock first. This function
1766	 * is speculative anyways, so missing one is ok.
1767	 */
1768	if (pipe->nrbufs < pipe->buffers)
1769		return 0;
1770
1771	ret = 0;
1772	pipe_lock(pipe);
1773
1774	while (pipe->nrbufs >= pipe->buffers) {
1775		if (!pipe->readers) {
1776			send_sig(SIGPIPE, current, 0);
1777			ret = -EPIPE;
1778			break;
1779		}
1780		if (flags & SPLICE_F_NONBLOCK) {
1781			ret = -EAGAIN;
1782			break;
1783		}
1784		if (signal_pending(current)) {
1785			ret = -ERESTARTSYS;
1786			break;
1787		}
1788		pipe->waiting_writers++;
1789		pipe_wait(pipe);
1790		pipe->waiting_writers--;
1791	}
1792
1793	pipe_unlock(pipe);
1794	return ret;
1795}
1796
1797/*
1798 * Splice contents of ipipe to opipe.
1799 */
1800static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1801			       struct pipe_inode_info *opipe,
1802			       size_t len, unsigned int flags)
1803{
1804	struct pipe_buffer *ibuf, *obuf;
1805	int ret = 0, nbuf;
 
 
 
1806	bool input_wakeup = false;
1807
1808
1809retry:
1810	ret = ipipe_prep(ipipe, flags);
1811	if (ret)
1812		return ret;
1813
1814	ret = opipe_prep(opipe, flags);
1815	if (ret)
1816		return ret;
1817
1818	/*
1819	 * Potential ABBA deadlock, work around it by ordering lock
1820	 * grabbing by pipe info address. Otherwise two different processes
1821	 * could deadlock (one doing tee from A -> B, the other from B -> A).
1822	 */
1823	pipe_double_lock(ipipe, opipe);
1824
 
 
 
 
 
1825	do {
 
 
1826		if (!opipe->readers) {
1827			send_sig(SIGPIPE, current, 0);
1828			if (!ret)
1829				ret = -EPIPE;
1830			break;
1831		}
1832
1833		if (!ipipe->nrbufs && !ipipe->writers)
 
 
 
1834			break;
1835
1836		/*
1837		 * Cannot make any progress, because either the input
1838		 * pipe is empty or the output pipe is full.
1839		 */
1840		if (!ipipe->nrbufs || opipe->nrbufs >= opipe->buffers) {
 
1841			/* Already processed some buffers, break */
1842			if (ret)
1843				break;
1844
1845			if (flags & SPLICE_F_NONBLOCK) {
1846				ret = -EAGAIN;
1847				break;
1848			}
1849
1850			/*
1851			 * We raced with another reader/writer and haven't
1852			 * managed to process any buffers.  A zero return
1853			 * value means EOF, so retry instead.
1854			 */
1855			pipe_unlock(ipipe);
1856			pipe_unlock(opipe);
1857			goto retry;
1858		}
1859
1860		ibuf = ipipe->bufs + ipipe->curbuf;
1861		nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1);
1862		obuf = opipe->bufs + nbuf;
1863
1864		if (len >= ibuf->len) {
1865			/*
1866			 * Simply move the whole buffer from ipipe to opipe
1867			 */
1868			*obuf = *ibuf;
1869			ibuf->ops = NULL;
1870			opipe->nrbufs++;
1871			ipipe->curbuf = (ipipe->curbuf + 1) & (ipipe->buffers - 1);
1872			ipipe->nrbufs--;
1873			input_wakeup = true;
 
 
 
1874		} else {
1875			/*
1876			 * Get a reference to this pipe buffer,
1877			 * so we can copy the contents over.
1878			 */
1879			ibuf->ops->get(ipipe, ibuf);
 
 
 
 
1880			*obuf = *ibuf;
1881
1882			/*
1883			 * Don't inherit the gift flag, we need to
1884			 * prevent multiple steals of this page.
1885			 */
1886			obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
 
1887
1888			obuf->len = len;
1889			opipe->nrbufs++;
1890			ibuf->offset += obuf->len;
1891			ibuf->len -= obuf->len;
 
 
1892		}
1893		ret += obuf->len;
1894		len -= obuf->len;
1895	} while (len);
1896
1897	pipe_unlock(ipipe);
1898	pipe_unlock(opipe);
1899
1900	/*
1901	 * If we put data in the output pipe, wakeup any potential readers.
1902	 */
1903	if (ret > 0)
1904		wakeup_pipe_readers(opipe);
1905
1906	if (input_wakeup)
1907		wakeup_pipe_writers(ipipe);
1908
1909	return ret;
1910}
1911
1912/*
1913 * Link contents of ipipe to opipe.
1914 */
1915static int link_pipe(struct pipe_inode_info *ipipe,
1916		     struct pipe_inode_info *opipe,
1917		     size_t len, unsigned int flags)
1918{
1919	struct pipe_buffer *ibuf, *obuf;
1920	int ret = 0, i = 0, nbuf;
 
 
 
1921
1922	/*
1923	 * Potential ABBA deadlock, work around it by ordering lock
1924	 * grabbing by pipe info address. Otherwise two different processes
1925	 * could deadlock (one doing tee from A -> B, the other from B -> A).
1926	 */
1927	pipe_double_lock(ipipe, opipe);
1928
 
 
 
 
 
1929	do {
1930		if (!opipe->readers) {
1931			send_sig(SIGPIPE, current, 0);
1932			if (!ret)
1933				ret = -EPIPE;
1934			break;
1935		}
1936
 
 
 
1937		/*
1938		 * If we have iterated all input buffers or ran out of
1939		 * output room, break.
1940		 */
1941		if (i >= ipipe->nrbufs || opipe->nrbufs >= opipe->buffers)
 
1942			break;
1943
1944		ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (ipipe->buffers-1));
1945		nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1);
1946
1947		/*
1948		 * Get a reference to this pipe buffer,
1949		 * so we can copy the contents over.
1950		 */
1951		ibuf->ops->get(ipipe, ibuf);
 
 
 
 
1952
1953		obuf = opipe->bufs + nbuf;
1954		*obuf = *ibuf;
1955
1956		/*
1957		 * Don't inherit the gift flag, we need to
1958		 * prevent multiple steals of this page.
1959		 */
1960		obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
 
1961
1962		if (obuf->len > len)
1963			obuf->len = len;
1964
1965		opipe->nrbufs++;
1966		ret += obuf->len;
1967		len -= obuf->len;
1968		i++;
1969	} while (len);
1970
1971	/*
1972	 * return EAGAIN if we have the potential of some data in the
1973	 * future, otherwise just return 0
1974	 */
1975	if (!ret && ipipe->waiting_writers && (flags & SPLICE_F_NONBLOCK))
1976		ret = -EAGAIN;
1977
1978	pipe_unlock(ipipe);
1979	pipe_unlock(opipe);
1980
1981	/*
1982	 * If we put data in the output pipe, wakeup any potential readers.
1983	 */
1984	if (ret > 0)
1985		wakeup_pipe_readers(opipe);
1986
1987	return ret;
1988}
1989
1990/*
1991 * This is a tee(1) implementation that works on pipes. It doesn't copy
1992 * any data, it simply references the 'in' pages on the 'out' pipe.
1993 * The 'flags' used are the SPLICE_F_* variants, currently the only
1994 * applicable one is SPLICE_F_NONBLOCK.
1995 */
1996static long do_tee(struct file *in, struct file *out, size_t len,
1997		   unsigned int flags)
1998{
1999	struct pipe_inode_info *ipipe = get_pipe_info(in);
2000	struct pipe_inode_info *opipe = get_pipe_info(out);
2001	int ret = -EINVAL;
2002
 
 
 
 
2003	/*
2004	 * Duplicate the contents of ipipe to opipe without actually
2005	 * copying the data.
2006	 */
2007	if (ipipe && opipe && ipipe != opipe) {
 
 
 
2008		/*
2009		 * Keep going, unless we encounter an error. The ipipe/opipe
2010		 * ordering doesn't really matter.
2011		 */
2012		ret = ipipe_prep(ipipe, flags);
2013		if (!ret) {
2014			ret = opipe_prep(opipe, flags);
2015			if (!ret)
2016				ret = link_pipe(ipipe, opipe, len, flags);
2017		}
2018	}
2019
2020	return ret;
2021}
2022
2023SYSCALL_DEFINE4(tee, int, fdin, int, fdout, size_t, len, unsigned int, flags)
2024{
2025	struct fd in;
2026	int error;
2027
 
 
 
2028	if (unlikely(!len))
2029		return 0;
2030
2031	error = -EBADF;
2032	in = fdget(fdin);
2033	if (in.file) {
2034		if (in.file->f_mode & FMODE_READ) {
2035			struct fd out = fdget(fdout);
2036			if (out.file) {
2037				if (out.file->f_mode & FMODE_WRITE)
2038					error = do_tee(in.file, out.file,
2039							len, flags);
2040				fdput(out);
2041			}
2042		}
2043 		fdput(in);
2044 	}
2045
2046	return error;
2047}