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/buffer_head.h>
  29#include <linux/module.h>
  30#include <linux/syscalls.h>
  31#include <linux/uio.h>
  32#include <linux/security.h>
  33#include <linux/gfp.h>
 
 
 
  34
  35/*
  36 * Attempt to steal a page from a pipe buffer. This should perhaps go into
  37 * a vm helper function, it's already simplified quite a bit by the
  38 * addition of remove_mapping(). If success is returned, the caller may
  39 * attempt to reuse this page for another destination.
  40 */
  41static int page_cache_pipe_buf_steal(struct pipe_inode_info *pipe,
  42				     struct pipe_buffer *buf)
  43{
  44	struct page *page = buf->page;
  45	struct address_space *mapping;
  46
  47	lock_page(page);
  48
  49	mapping = page_mapping(page);
  50	if (mapping) {
  51		WARN_ON(!PageUptodate(page));
  52
  53		/*
  54		 * At least for ext2 with nobh option, we need to wait on
  55		 * writeback completing on this page, since we'll remove it
  56		 * from the pagecache.  Otherwise truncate wont wait on the
  57		 * page, allowing the disk blocks to be reused by someone else
  58		 * before we actually wrote our data to them. fs corruption
  59		 * ensues.
  60		 */
  61		wait_on_page_writeback(page);
  62
  63		if (page_has_private(page) &&
  64		    !try_to_release_page(page, GFP_KERNEL))
  65			goto out_unlock;
  66
  67		/*
  68		 * If we succeeded in removing the mapping, set LRU flag
  69		 * and return good.
  70		 */
  71		if (remove_mapping(mapping, page)) {
  72			buf->flags |= PIPE_BUF_FLAG_LRU;
  73			return 0;
  74		}
  75	}
  76
  77	/*
  78	 * Raced with truncate or failed to remove page from current
  79	 * address space, unlock and return failure.
  80	 */
  81out_unlock:
  82	unlock_page(page);
  83	return 1;
  84}
  85
  86static void page_cache_pipe_buf_release(struct pipe_inode_info *pipe,
  87					struct pipe_buffer *buf)
  88{
  89	page_cache_release(buf->page);
  90	buf->flags &= ~PIPE_BUF_FLAG_LRU;
  91}
  92
  93/*
  94 * Check whether the contents of buf is OK to access. Since the content
  95 * is a page cache page, IO may be in flight.
  96 */
  97static int page_cache_pipe_buf_confirm(struct pipe_inode_info *pipe,
  98				       struct pipe_buffer *buf)
  99{
 100	struct page *page = buf->page;
 101	int err;
 102
 103	if (!PageUptodate(page)) {
 104		lock_page(page);
 105
 106		/*
 107		 * Page got truncated/unhashed. This will cause a 0-byte
 108		 * splice, if this is the first page.
 109		 */
 110		if (!page->mapping) {
 111			err = -ENODATA;
 112			goto error;
 113		}
 114
 115		/*
 116		 * Uh oh, read-error from disk.
 117		 */
 118		if (!PageUptodate(page)) {
 119			err = -EIO;
 120			goto error;
 121		}
 122
 123		/*
 124		 * Page is ok afterall, we are done.
 125		 */
 126		unlock_page(page);
 127	}
 128
 129	return 0;
 130error:
 131	unlock_page(page);
 132	return err;
 133}
 134
 135const struct pipe_buf_operations page_cache_pipe_buf_ops = {
 136	.can_merge = 0,
 137	.map = generic_pipe_buf_map,
 138	.unmap = generic_pipe_buf_unmap,
 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	.map = generic_pipe_buf_map,
 158	.unmap = generic_pipe_buf_unmap,
 159	.confirm = generic_pipe_buf_confirm,
 160	.release = page_cache_pipe_buf_release,
 161	.steal = user_page_pipe_buf_steal,
 162	.get = generic_pipe_buf_get,
 163};
 164
 165static void wakeup_pipe_readers(struct pipe_inode_info *pipe)
 166{
 167	smp_mb();
 168	if (waitqueue_active(&pipe->wait))
 169		wake_up_interruptible(&pipe->wait);
 170	kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 171}
 172
 173/**
 174 * splice_to_pipe - fill passed data into a pipe
 175 * @pipe:	pipe to fill
 176 * @spd:	data to fill
 177 *
 178 * Description:
 179 *    @spd contains a map of pages and len/offset tuples, along with
 180 *    the struct pipe_buf_operations associated with these pages. This
 181 *    function will link that data to the pipe.
 182 *
 183 */
 184ssize_t splice_to_pipe(struct pipe_inode_info *pipe,
 185		       struct splice_pipe_desc *spd)
 186{
 187	unsigned int spd_pages = spd->nr_pages;
 188	int ret, do_wakeup, page_nr;
 189
 190	ret = 0;
 191	do_wakeup = 0;
 192	page_nr = 0;
 193
 194	pipe_lock(pipe);
 195
 196	for (;;) {
 197		if (!pipe->readers) {
 198			send_sig(SIGPIPE, current, 0);
 199			if (!ret)
 200				ret = -EPIPE;
 201			break;
 202		}
 203
 204		if (pipe->nrbufs < pipe->buffers) {
 205			int newbuf = (pipe->curbuf + pipe->nrbufs) & (pipe->buffers - 1);
 206			struct pipe_buffer *buf = pipe->bufs + newbuf;
 207
 208			buf->page = spd->pages[page_nr];
 209			buf->offset = spd->partial[page_nr].offset;
 210			buf->len = spd->partial[page_nr].len;
 211			buf->private = spd->partial[page_nr].private;
 212			buf->ops = spd->ops;
 213			if (spd->flags & SPLICE_F_GIFT)
 214				buf->flags |= PIPE_BUF_FLAG_GIFT;
 215
 216			pipe->nrbufs++;
 217			page_nr++;
 218			ret += buf->len;
 219
 220			if (pipe->inode)
 221				do_wakeup = 1;
 222
 223			if (!--spd->nr_pages)
 224				break;
 225			if (pipe->nrbufs < pipe->buffers)
 226				continue;
 
 227
 228			break;
 229		}
 
 
 
 
 
 
 
 
 
 
 
 
 230
 231		if (spd->flags & SPLICE_F_NONBLOCK) {
 232			if (!ret)
 233				ret = -EAGAIN;
 234			break;
 235		}
 236
 237		if (signal_pending(current)) {
 238			if (!ret)
 239				ret = -ERESTARTSYS;
 240			break;
 241		}
 242
 243		if (do_wakeup) {
 244			smp_mb();
 245			if (waitqueue_active(&pipe->wait))
 246				wake_up_interruptible_sync(&pipe->wait);
 247			kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 248			do_wakeup = 0;
 249		}
 250
 251		pipe->waiting_writers++;
 252		pipe_wait(pipe);
 253		pipe->waiting_writers--;
 254	}
 255
 256	pipe_unlock(pipe);
 257
 258	if (do_wakeup)
 259		wakeup_pipe_readers(pipe);
 260
 
 261	while (page_nr < spd_pages)
 262		spd->spd_release(spd, page_nr++);
 263
 264	return ret;
 265}
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 266
 267void spd_release_page(struct splice_pipe_desc *spd, unsigned int i)
 268{
 269	page_cache_release(spd->pages[i]);
 270}
 271
 272/*
 273 * Check if we need to grow the arrays holding pages and partial page
 274 * descriptions.
 275 */
 276int splice_grow_spd(struct pipe_inode_info *pipe, struct splice_pipe_desc *spd)
 277{
 278	if (pipe->buffers <= PIPE_DEF_BUFFERS)
 
 
 
 279		return 0;
 280
 281	spd->pages = kmalloc(pipe->buffers * sizeof(struct page *), GFP_KERNEL);
 282	spd->partial = kmalloc(pipe->buffers * sizeof(struct partial_page), GFP_KERNEL);
 283
 284	if (spd->pages && spd->partial)
 285		return 0;
 286
 287	kfree(spd->pages);
 288	kfree(spd->partial);
 289	return -ENOMEM;
 290}
 291
 292void splice_shrink_spd(struct pipe_inode_info *pipe,
 293		       struct splice_pipe_desc *spd)
 294{
 295	if (pipe->buffers <= PIPE_DEF_BUFFERS)
 296		return;
 297
 298	kfree(spd->pages);
 299	kfree(spd->partial);
 300}
 301
 302static int
 303__generic_file_splice_read(struct file *in, loff_t *ppos,
 304			   struct pipe_inode_info *pipe, size_t len,
 305			   unsigned int flags)
 306{
 307	struct address_space *mapping = in->f_mapping;
 308	unsigned int loff, nr_pages, req_pages;
 309	struct page *pages[PIPE_DEF_BUFFERS];
 310	struct partial_page partial[PIPE_DEF_BUFFERS];
 311	struct page *page;
 312	pgoff_t index, end_index;
 313	loff_t isize;
 314	int error, page_nr;
 315	struct splice_pipe_desc spd = {
 316		.pages = pages,
 317		.partial = partial,
 318		.flags = flags,
 319		.ops = &page_cache_pipe_buf_ops,
 320		.spd_release = spd_release_page,
 321	};
 322
 323	if (splice_grow_spd(pipe, &spd))
 324		return -ENOMEM;
 325
 326	index = *ppos >> PAGE_CACHE_SHIFT;
 327	loff = *ppos & ~PAGE_CACHE_MASK;
 328	req_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 329	nr_pages = min(req_pages, pipe->buffers);
 330
 331	/*
 332	 * Lookup the (hopefully) full range of pages we need.
 333	 */
 334	spd.nr_pages = find_get_pages_contig(mapping, index, nr_pages, spd.pages);
 335	index += spd.nr_pages;
 336
 337	/*
 338	 * If find_get_pages_contig() returned fewer pages than we needed,
 339	 * readahead/allocate the rest and fill in the holes.
 340	 */
 341	if (spd.nr_pages < nr_pages)
 342		page_cache_sync_readahead(mapping, &in->f_ra, in,
 343				index, req_pages - spd.nr_pages);
 344
 345	error = 0;
 346	while (spd.nr_pages < nr_pages) {
 347		/*
 348		 * Page could be there, find_get_pages_contig() breaks on
 349		 * the first hole.
 350		 */
 351		page = find_get_page(mapping, index);
 352		if (!page) {
 353			/*
 354			 * page didn't exist, allocate one.
 355			 */
 356			page = page_cache_alloc_cold(mapping);
 357			if (!page)
 358				break;
 359
 360			error = add_to_page_cache_lru(page, mapping, index,
 361						GFP_KERNEL);
 362			if (unlikely(error)) {
 363				page_cache_release(page);
 364				if (error == -EEXIST)
 365					continue;
 366				break;
 367			}
 368			/*
 369			 * add_to_page_cache() locks the page, unlock it
 370			 * to avoid convoluting the logic below even more.
 371			 */
 372			unlock_page(page);
 373		}
 374
 375		spd.pages[spd.nr_pages++] = page;
 376		index++;
 377	}
 378
 379	/*
 380	 * Now loop over the map and see if we need to start IO on any
 381	 * pages, fill in the partial map, etc.
 382	 */
 383	index = *ppos >> PAGE_CACHE_SHIFT;
 384	nr_pages = spd.nr_pages;
 385	spd.nr_pages = 0;
 386	for (page_nr = 0; page_nr < nr_pages; page_nr++) {
 387		unsigned int this_len;
 388
 389		if (!len)
 390			break;
 391
 392		/*
 393		 * this_len is the max we'll use from this page
 394		 */
 395		this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff);
 396		page = spd.pages[page_nr];
 397
 398		if (PageReadahead(page))
 399			page_cache_async_readahead(mapping, &in->f_ra, in,
 400					page, index, req_pages - page_nr);
 401
 402		/*
 403		 * If the page isn't uptodate, we may need to start io on it
 404		 */
 405		if (!PageUptodate(page)) {
 406			lock_page(page);
 407
 408			/*
 409			 * Page was truncated, or invalidated by the
 410			 * filesystem.  Redo the find/create, but this time the
 411			 * page is kept locked, so there's no chance of another
 412			 * race with truncate/invalidate.
 413			 */
 414			if (!page->mapping) {
 415				unlock_page(page);
 416				page = find_or_create_page(mapping, index,
 417						mapping_gfp_mask(mapping));
 418
 419				if (!page) {
 420					error = -ENOMEM;
 421					break;
 422				}
 423				page_cache_release(spd.pages[page_nr]);
 424				spd.pages[page_nr] = page;
 425			}
 426			/*
 427			 * page was already under io and is now done, great
 428			 */
 429			if (PageUptodate(page)) {
 430				unlock_page(page);
 431				goto fill_it;
 432			}
 433
 434			/*
 435			 * need to read in the page
 436			 */
 437			error = mapping->a_ops->readpage(in, page);
 438			if (unlikely(error)) {
 439				/*
 440				 * We really should re-lookup the page here,
 441				 * but it complicates things a lot. Instead
 442				 * lets just do what we already stored, and
 443				 * we'll get it the next time we are called.
 444				 */
 445				if (error == AOP_TRUNCATED_PAGE)
 446					error = 0;
 447
 448				break;
 449			}
 450		}
 451fill_it:
 452		/*
 453		 * i_size must be checked after PageUptodate.
 454		 */
 455		isize = i_size_read(mapping->host);
 456		end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
 457		if (unlikely(!isize || index > end_index))
 458			break;
 459
 460		/*
 461		 * if this is the last page, see if we need to shrink
 462		 * the length and stop
 463		 */
 464		if (end_index == index) {
 465			unsigned int plen;
 466
 467			/*
 468			 * max good bytes in this page
 469			 */
 470			plen = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
 471			if (plen <= loff)
 472				break;
 473
 474			/*
 475			 * force quit after adding this page
 476			 */
 477			this_len = min(this_len, plen - loff);
 478			len = this_len;
 479		}
 480
 481		spd.partial[page_nr].offset = loff;
 482		spd.partial[page_nr].len = this_len;
 483		len -= this_len;
 484		loff = 0;
 485		spd.nr_pages++;
 486		index++;
 487	}
 488
 489	/*
 490	 * Release any pages at the end, if we quit early. 'page_nr' is how far
 491	 * we got, 'nr_pages' is how many pages are in the map.
 492	 */
 493	while (page_nr < nr_pages)
 494		page_cache_release(spd.pages[page_nr++]);
 495	in->f_ra.prev_pos = (loff_t)index << PAGE_CACHE_SHIFT;
 496
 497	if (spd.nr_pages)
 498		error = splice_to_pipe(pipe, &spd);
 499
 500	splice_shrink_spd(pipe, &spd);
 501	return error;
 502}
 503
 504/**
 505 * generic_file_splice_read - splice data from file to a pipe
 506 * @in:		file to splice from
 507 * @ppos:	position in @in
 508 * @pipe:	pipe to splice to
 509 * @len:	number of bytes to splice
 510 * @flags:	splice modifier flags
 511 *
 512 * Description:
 513 *    Will read pages from given file and fill them into a pipe. Can be
 514 *    used as long as the address_space operations for the source implements
 515 *    a readpage() hook.
 516 *
 517 */
 518ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
 519				 struct pipe_inode_info *pipe, size_t len,
 520				 unsigned int flags)
 521{
 522	loff_t isize, left;
 523	int ret;
 524
 525	isize = i_size_read(in->f_mapping->host);
 526	if (unlikely(*ppos >= isize))
 527		return 0;
 528
 529	left = isize - *ppos;
 530	if (unlikely(left < len))
 531		len = left;
 532
 533	ret = __generic_file_splice_read(in, ppos, pipe, len, flags);
 534	if (ret > 0) {
 535		*ppos += ret;
 536		file_accessed(in);
 
 
 
 
 
 
 
 
 
 
 537	}
 538
 539	return ret;
 540}
 541EXPORT_SYMBOL(generic_file_splice_read);
 542
 543static const struct pipe_buf_operations default_pipe_buf_ops = {
 544	.can_merge = 0,
 545	.map = generic_pipe_buf_map,
 546	.unmap = generic_pipe_buf_unmap,
 547	.confirm = generic_pipe_buf_confirm,
 548	.release = generic_pipe_buf_release,
 549	.steal = generic_pipe_buf_steal,
 550	.get = generic_pipe_buf_get,
 551};
 552
 553static ssize_t kernel_readv(struct file *file, const struct iovec *vec,
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 554			    unsigned long vlen, loff_t offset)
 555{
 556	mm_segment_t old_fs;
 557	loff_t pos = offset;
 558	ssize_t res;
 559
 560	old_fs = get_fs();
 561	set_fs(get_ds());
 562	/* The cast to a user pointer is valid due to the set_fs() */
 563	res = vfs_readv(file, (const struct iovec __user *)vec, vlen, &pos);
 564	set_fs(old_fs);
 565
 566	return res;
 567}
 568
 569static ssize_t kernel_write(struct file *file, const char *buf, size_t count,
 570			    loff_t pos)
 571{
 572	mm_segment_t old_fs;
 573	ssize_t res;
 574
 575	old_fs = get_fs();
 576	set_fs(get_ds());
 577	/* The cast to a user pointer is valid due to the set_fs() */
 578	res = vfs_write(file, (const char __user *)buf, count, &pos);
 579	set_fs(old_fs);
 580
 581	return res;
 582}
 
 583
 584ssize_t default_file_splice_read(struct file *in, loff_t *ppos,
 585				 struct pipe_inode_info *pipe, size_t len,
 586				 unsigned int flags)
 587{
 
 
 
 588	unsigned int nr_pages;
 589	unsigned int nr_freed;
 590	size_t offset;
 591	struct page *pages[PIPE_DEF_BUFFERS];
 592	struct partial_page partial[PIPE_DEF_BUFFERS];
 593	struct iovec *vec, __vec[PIPE_DEF_BUFFERS];
 594	ssize_t res;
 595	size_t this_len;
 596	int error;
 597	int i;
 598	struct splice_pipe_desc spd = {
 599		.pages = pages,
 600		.partial = partial,
 601		.flags = flags,
 602		.ops = &default_pipe_buf_ops,
 603		.spd_release = spd_release_page,
 604	};
 605
 606	if (splice_grow_spd(pipe, &spd))
 
 
 
 
 
 
 
 
 
 
 
 
 607		return -ENOMEM;
 608
 609	res = -ENOMEM;
 
 
 610	vec = __vec;
 611	if (pipe->buffers > PIPE_DEF_BUFFERS) {
 612		vec = kmalloc(pipe->buffers * sizeof(struct iovec), GFP_KERNEL);
 613		if (!vec)
 614			goto shrink_ret;
 
 
 615	}
 616
 617	offset = *ppos & ~PAGE_CACHE_MASK;
 618	nr_pages = (len + offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 619
 620	for (i = 0; i < nr_pages && i < pipe->buffers && len; i++) {
 621		struct page *page;
 622
 623		page = alloc_page(GFP_USER);
 624		error = -ENOMEM;
 625		if (!page)
 626			goto err;
 627
 628		this_len = min_t(size_t, len, PAGE_CACHE_SIZE - offset);
 629		vec[i].iov_base = (void __user *) page_address(page);
 630		vec[i].iov_len = this_len;
 631		spd.pages[i] = page;
 632		spd.nr_pages++;
 633		len -= this_len;
 634		offset = 0;
 635	}
 636
 637	res = kernel_readv(in, vec, spd.nr_pages, *ppos);
 638	if (res < 0) {
 639		error = res;
 640		goto err;
 641	}
 642
 643	error = 0;
 644	if (!res)
 645		goto err;
 646
 647	nr_freed = 0;
 648	for (i = 0; i < spd.nr_pages; i++) {
 649		this_len = min_t(size_t, vec[i].iov_len, res);
 650		spd.partial[i].offset = 0;
 651		spd.partial[i].len = this_len;
 652		if (!this_len) {
 653			__free_page(spd.pages[i]);
 654			spd.pages[i] = NULL;
 655			nr_freed++;
 656		}
 657		res -= this_len;
 658	}
 659	spd.nr_pages -= nr_freed;
 660
 661	res = splice_to_pipe(pipe, &spd);
 662	if (res > 0)
 663		*ppos += res;
 
 664
 665shrink_ret:
 666	if (vec != __vec)
 667		kfree(vec);
 668	splice_shrink_spd(pipe, &spd);
 
 
 
 
 669	return res;
 670
 671err:
 672	for (i = 0; i < spd.nr_pages; i++)
 673		__free_page(spd.pages[i]);
 674
 675	res = error;
 676	goto shrink_ret;
 677}
 678EXPORT_SYMBOL(default_file_splice_read);
 679
 680/*
 681 * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
 682 * using sendpage(). Return the number of bytes sent.
 683 */
 684static int pipe_to_sendpage(struct pipe_inode_info *pipe,
 685			    struct pipe_buffer *buf, struct splice_desc *sd)
 686{
 687	struct file *file = sd->u.file;
 688	loff_t pos = sd->pos;
 689	int more;
 690
 691	if (!likely(file->f_op && file->f_op->sendpage))
 692		return -EINVAL;
 693
 694	more = (sd->flags & SPLICE_F_MORE) || sd->len < sd->total_len;
 695	return file->f_op->sendpage(file, buf->page, buf->offset,
 696				    sd->len, &pos, more);
 697}
 698
 699/*
 700 * This is a little more tricky than the file -> pipe splicing. There are
 701 * basically three cases:
 702 *
 703 *	- Destination page already exists in the address space and there
 704 *	  are users of it. For that case we have no other option that
 705 *	  copying the data. Tough luck.
 706 *	- Destination page already exists in the address space, but there
 707 *	  are no users of it. Make sure it's uptodate, then drop it. Fall
 708 *	  through to last case.
 709 *	- Destination page does not exist, we can add the pipe page to
 710 *	  the page cache and avoid the copy.
 711 *
 712 * If asked to move pages to the output file (SPLICE_F_MOVE is set in
 713 * sd->flags), we attempt to migrate pages from the pipe to the output
 714 * file address space page cache. This is possible if no one else has
 715 * the pipe page referenced outside of the pipe and page cache. If
 716 * SPLICE_F_MOVE isn't set, or we cannot move the page, we simply create
 717 * a new page in the output file page cache and fill/dirty that.
 718 */
 719int pipe_to_file(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
 720		 struct splice_desc *sd)
 721{
 722	struct file *file = sd->u.file;
 723	struct address_space *mapping = file->f_mapping;
 724	unsigned int offset, this_len;
 725	struct page *page;
 726	void *fsdata;
 727	int ret;
 728
 729	offset = sd->pos & ~PAGE_CACHE_MASK;
 730
 731	this_len = sd->len;
 732	if (this_len + offset > PAGE_CACHE_SIZE)
 733		this_len = PAGE_CACHE_SIZE - offset;
 734
 735	ret = pagecache_write_begin(file, mapping, sd->pos, this_len,
 736				AOP_FLAG_UNINTERRUPTIBLE, &page, &fsdata);
 737	if (unlikely(ret))
 738		goto out;
 739
 740	if (buf->page != page) {
 741		/*
 742		 * Careful, ->map() uses KM_USER0!
 743		 */
 744		char *src = buf->ops->map(pipe, buf, 1);
 745		char *dst = kmap_atomic(page, KM_USER1);
 746
 747		memcpy(dst + offset, src + buf->offset, this_len);
 748		flush_dcache_page(page);
 749		kunmap_atomic(dst, KM_USER1);
 750		buf->ops->unmap(pipe, buf, src);
 751	}
 752	ret = pagecache_write_end(file, mapping, sd->pos, this_len, this_len,
 753				page, fsdata);
 754out:
 755	return ret;
 756}
 757EXPORT_SYMBOL(pipe_to_file);
 758
 759static void wakeup_pipe_writers(struct pipe_inode_info *pipe)
 760{
 761	smp_mb();
 762	if (waitqueue_active(&pipe->wait))
 763		wake_up_interruptible(&pipe->wait);
 764	kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 765}
 766
 767/**
 768 * splice_from_pipe_feed - feed available data from a pipe to a file
 769 * @pipe:	pipe to splice from
 770 * @sd:		information to @actor
 771 * @actor:	handler that splices the data
 772 *
 773 * Description:
 774 *    This function loops over the pipe and calls @actor to do the
 775 *    actual moving of a single struct pipe_buffer to the desired
 776 *    destination.  It returns when there's no more buffers left in
 777 *    the pipe or if the requested number of bytes (@sd->total_len)
 778 *    have been copied.  It returns a positive number (one) if the
 779 *    pipe needs to be filled with more data, zero if the required
 780 *    number of bytes have been copied and -errno on error.
 781 *
 782 *    This, together with splice_from_pipe_{begin,end,next}, may be
 783 *    used to implement the functionality of __splice_from_pipe() when
 784 *    locking is required around copying the pipe buffers to the
 785 *    destination.
 786 */
 787int splice_from_pipe_feed(struct pipe_inode_info *pipe, struct splice_desc *sd,
 788			  splice_actor *actor)
 789{
 790	int ret;
 791
 792	while (pipe->nrbufs) {
 793		struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
 794		const struct pipe_buf_operations *ops = buf->ops;
 795
 796		sd->len = buf->len;
 797		if (sd->len > sd->total_len)
 798			sd->len = sd->total_len;
 799
 800		ret = buf->ops->confirm(pipe, buf);
 801		if (unlikely(ret)) {
 802			if (ret == -ENODATA)
 803				ret = 0;
 804			return ret;
 805		}
 806
 807		ret = actor(pipe, buf, sd);
 808		if (ret <= 0)
 809			return ret;
 810
 811		buf->offset += ret;
 812		buf->len -= ret;
 813
 814		sd->num_spliced += ret;
 815		sd->len -= ret;
 816		sd->pos += ret;
 817		sd->total_len -= ret;
 818
 819		if (!buf->len) {
 820			buf->ops = NULL;
 821			ops->release(pipe, buf);
 822			pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1);
 823			pipe->nrbufs--;
 824			if (pipe->inode)
 825				sd->need_wakeup = true;
 826		}
 827
 828		if (!sd->total_len)
 829			return 0;
 830	}
 831
 832	return 1;
 833}
 834EXPORT_SYMBOL(splice_from_pipe_feed);
 835
 836/**
 837 * splice_from_pipe_next - wait for some data to splice from
 838 * @pipe:	pipe to splice from
 839 * @sd:		information about the splice operation
 840 *
 841 * Description:
 842 *    This function will wait for some data and return a positive
 843 *    value (one) if pipe buffers are available.  It will return zero
 844 *    or -errno if no more data needs to be spliced.
 845 */
 846int splice_from_pipe_next(struct pipe_inode_info *pipe, struct splice_desc *sd)
 847{
 
 
 
 
 
 
 
 848	while (!pipe->nrbufs) {
 849		if (!pipe->writers)
 850			return 0;
 851
 852		if (!pipe->waiting_writers && sd->num_spliced)
 853			return 0;
 854
 855		if (sd->flags & SPLICE_F_NONBLOCK)
 856			return -EAGAIN;
 857
 858		if (signal_pending(current))
 859			return -ERESTARTSYS;
 860
 861		if (sd->need_wakeup) {
 862			wakeup_pipe_writers(pipe);
 863			sd->need_wakeup = false;
 864		}
 865
 866		pipe_wait(pipe);
 867	}
 868
 869	return 1;
 870}
 871EXPORT_SYMBOL(splice_from_pipe_next);
 872
 873/**
 874 * splice_from_pipe_begin - start splicing from pipe
 875 * @sd:		information about the splice operation
 876 *
 877 * Description:
 878 *    This function should be called before a loop containing
 879 *    splice_from_pipe_next() and splice_from_pipe_feed() to
 880 *    initialize the necessary fields of @sd.
 881 */
 882void splice_from_pipe_begin(struct splice_desc *sd)
 883{
 884	sd->num_spliced = 0;
 885	sd->need_wakeup = false;
 886}
 887EXPORT_SYMBOL(splice_from_pipe_begin);
 888
 889/**
 890 * splice_from_pipe_end - finish splicing from pipe
 891 * @pipe:	pipe to splice from
 892 * @sd:		information about the splice operation
 893 *
 894 * Description:
 895 *    This function will wake up pipe writers if necessary.  It should
 896 *    be called after a loop containing splice_from_pipe_next() and
 897 *    splice_from_pipe_feed().
 898 */
 899void splice_from_pipe_end(struct pipe_inode_info *pipe, struct splice_desc *sd)
 900{
 901	if (sd->need_wakeup)
 902		wakeup_pipe_writers(pipe);
 903}
 904EXPORT_SYMBOL(splice_from_pipe_end);
 905
 906/**
 907 * __splice_from_pipe - splice data from a pipe to given actor
 908 * @pipe:	pipe to splice from
 909 * @sd:		information to @actor
 910 * @actor:	handler that splices the data
 911 *
 912 * Description:
 913 *    This function does little more than loop over the pipe and call
 914 *    @actor to do the actual moving of a single struct pipe_buffer to
 915 *    the desired destination. See pipe_to_file, pipe_to_sendpage, or
 916 *    pipe_to_user.
 917 *
 918 */
 919ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd,
 920			   splice_actor *actor)
 921{
 922	int ret;
 923
 924	splice_from_pipe_begin(sd);
 925	do {
 
 926		ret = splice_from_pipe_next(pipe, sd);
 927		if (ret > 0)
 928			ret = splice_from_pipe_feed(pipe, sd, actor);
 929	} while (ret > 0);
 930	splice_from_pipe_end(pipe, sd);
 931
 932	return sd->num_spliced ? sd->num_spliced : ret;
 933}
 934EXPORT_SYMBOL(__splice_from_pipe);
 935
 936/**
 937 * splice_from_pipe - splice data from a pipe to a file
 938 * @pipe:	pipe to splice from
 939 * @out:	file to splice to
 940 * @ppos:	position in @out
 941 * @len:	how many bytes to splice
 942 * @flags:	splice modifier flags
 943 * @actor:	handler that splices the data
 944 *
 945 * Description:
 946 *    See __splice_from_pipe. This function locks the pipe inode,
 947 *    otherwise it's identical to __splice_from_pipe().
 948 *
 949 */
 950ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
 951			 loff_t *ppos, size_t len, unsigned int flags,
 952			 splice_actor *actor)
 953{
 954	ssize_t ret;
 955	struct splice_desc sd = {
 956		.total_len = len,
 957		.flags = flags,
 958		.pos = *ppos,
 959		.u.file = out,
 960	};
 961
 962	pipe_lock(pipe);
 963	ret = __splice_from_pipe(pipe, &sd, actor);
 964	pipe_unlock(pipe);
 965
 966	return ret;
 967}
 968
 969/**
 970 * generic_file_splice_write - splice data from a pipe to a file
 971 * @pipe:	pipe info
 972 * @out:	file to write to
 973 * @ppos:	position in @out
 974 * @len:	number of bytes to splice
 975 * @flags:	splice modifier flags
 976 *
 977 * Description:
 978 *    Will either move or copy pages (determined by @flags options) from
 979 *    the given pipe inode to the given file.
 
 980 *
 981 */
 982ssize_t
 983generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
 984			  loff_t *ppos, size_t len, unsigned int flags)
 985{
 986	struct address_space *mapping = out->f_mapping;
 987	struct inode *inode = mapping->host;
 988	struct splice_desc sd = {
 989		.total_len = len,
 990		.flags = flags,
 991		.pos = *ppos,
 992		.u.file = out,
 993	};
 
 
 
 994	ssize_t ret;
 995
 
 
 
 996	pipe_lock(pipe);
 997
 998	splice_from_pipe_begin(&sd);
 999	do {
 
 
 
 
1000		ret = splice_from_pipe_next(pipe, &sd);
1001		if (ret <= 0)
1002			break;
1003
1004		mutex_lock_nested(&inode->i_mutex, I_MUTEX_CHILD);
1005		ret = file_remove_suid(out);
1006		if (!ret) {
1007			file_update_time(out);
1008			ret = splice_from_pipe_feed(pipe, &sd, pipe_to_file);
 
 
 
 
1009		}
1010		mutex_unlock(&inode->i_mutex);
1011	} while (ret > 0);
1012	splice_from_pipe_end(pipe, &sd);
1013
1014	pipe_unlock(pipe);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1015
1016	if (sd.num_spliced)
1017		ret = sd.num_spliced;
 
 
 
1018
1019	if (ret > 0) {
1020		unsigned long nr_pages;
1021		int err;
 
 
1022
1023		nr_pages = (ret + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 
 
1024
1025		err = generic_write_sync(out, *ppos, ret);
1026		if (err)
1027			ret = err;
1028		else
1029			*ppos += ret;
1030		balance_dirty_pages_ratelimited_nr(mapping, nr_pages);
 
 
 
 
 
 
 
 
 
 
 
1031	}
 
 
 
 
 
 
 
 
1032
1033	return ret;
1034}
1035
1036EXPORT_SYMBOL(generic_file_splice_write);
1037
1038static int write_pipe_buf(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
1039			  struct splice_desc *sd)
1040{
1041	int ret;
1042	void *data;
 
1043
1044	data = buf->ops->map(pipe, buf, 0);
1045	ret = kernel_write(sd->u.file, data + buf->offset, sd->len, sd->pos);
1046	buf->ops->unmap(pipe, buf, data);
1047
1048	return ret;
1049}
1050
1051static ssize_t default_file_splice_write(struct pipe_inode_info *pipe,
1052					 struct file *out, loff_t *ppos,
1053					 size_t len, unsigned int flags)
1054{
1055	ssize_t ret;
1056
1057	ret = splice_from_pipe(pipe, out, ppos, len, flags, write_pipe_buf);
1058	if (ret > 0)
1059		*ppos += ret;
1060
1061	return ret;
1062}
1063
1064/**
1065 * generic_splice_sendpage - splice data from a pipe to a socket
1066 * @pipe:	pipe to splice from
1067 * @out:	socket to write to
1068 * @ppos:	position in @out
1069 * @len:	number of bytes to splice
1070 * @flags:	splice modifier flags
1071 *
1072 * Description:
1073 *    Will send @len bytes from the pipe to a network socket. No data copying
1074 *    is involved.
1075 *
1076 */
1077ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
1078				loff_t *ppos, size_t len, unsigned int flags)
1079{
1080	return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
1081}
1082
1083EXPORT_SYMBOL(generic_splice_sendpage);
1084
1085/*
1086 * Attempt to initiate a splice from pipe to file.
1087 */
1088static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
1089			   loff_t *ppos, size_t len, unsigned int flags)
1090{
1091	ssize_t (*splice_write)(struct pipe_inode_info *, struct file *,
1092				loff_t *, size_t, unsigned int);
1093	int ret;
1094
1095	if (unlikely(!(out->f_mode & FMODE_WRITE)))
1096		return -EBADF;
1097
1098	if (unlikely(out->f_flags & O_APPEND))
1099		return -EINVAL;
1100
1101	ret = rw_verify_area(WRITE, out, ppos, len);
1102	if (unlikely(ret < 0))
1103		return ret;
1104
1105	if (out->f_op && out->f_op->splice_write)
1106		splice_write = out->f_op->splice_write;
1107	else
1108		splice_write = default_file_splice_write;
1109
1110	return splice_write(pipe, out, ppos, len, flags);
1111}
1112
1113/*
1114 * Attempt to initiate a splice from a file to a pipe.
1115 */
1116static long do_splice_to(struct file *in, loff_t *ppos,
1117			 struct pipe_inode_info *pipe, size_t len,
1118			 unsigned int flags)
1119{
1120	ssize_t (*splice_read)(struct file *, loff_t *,
1121			       struct pipe_inode_info *, size_t, unsigned int);
1122	int ret;
1123
1124	if (unlikely(!(in->f_mode & FMODE_READ)))
1125		return -EBADF;
1126
1127	ret = rw_verify_area(READ, in, ppos, len);
1128	if (unlikely(ret < 0))
1129		return ret;
1130
1131	if (in->f_op && in->f_op->splice_read)
 
 
 
1132		splice_read = in->f_op->splice_read;
1133	else
1134		splice_read = default_file_splice_read;
1135
1136	return splice_read(in, ppos, pipe, len, flags);
1137}
1138
1139/**
1140 * splice_direct_to_actor - splices data directly between two non-pipes
1141 * @in:		file to splice from
1142 * @sd:		actor information on where to splice to
1143 * @actor:	handles the data splicing
1144 *
1145 * Description:
1146 *    This is a special case helper to splice directly between two
1147 *    points, without requiring an explicit pipe. Internally an allocated
1148 *    pipe is cached in the process, and reused during the lifetime of
1149 *    that process.
1150 *
1151 */
1152ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
1153			       splice_direct_actor *actor)
1154{
1155	struct pipe_inode_info *pipe;
1156	long ret, bytes;
1157	umode_t i_mode;
1158	size_t len;
1159	int i, flags;
1160
1161	/*
1162	 * We require the input being a regular file, as we don't want to
1163	 * randomly drop data for eg socket -> socket splicing. Use the
1164	 * piped splicing for that!
1165	 */
1166	i_mode = in->f_path.dentry->d_inode->i_mode;
1167	if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode)))
1168		return -EINVAL;
1169
1170	/*
1171	 * neither in nor out is a pipe, setup an internal pipe attached to
1172	 * 'out' and transfer the wanted data from 'in' to 'out' through that
1173	 */
1174	pipe = current->splice_pipe;
1175	if (unlikely(!pipe)) {
1176		pipe = alloc_pipe_info(NULL);
1177		if (!pipe)
1178			return -ENOMEM;
1179
1180		/*
1181		 * We don't have an immediate reader, but we'll read the stuff
1182		 * out of the pipe right after the splice_to_pipe(). So set
1183		 * PIPE_READERS appropriately.
1184		 */
1185		pipe->readers = 1;
1186
1187		current->splice_pipe = pipe;
1188	}
1189
1190	/*
1191	 * Do the splice.
1192	 */
1193	ret = 0;
1194	bytes = 0;
1195	len = sd->total_len;
1196	flags = sd->flags;
1197
1198	/*
1199	 * Don't block on output, we have to drain the direct pipe.
1200	 */
1201	sd->flags &= ~SPLICE_F_NONBLOCK;
 
1202
1203	while (len) {
1204		size_t read_len;
1205		loff_t pos = sd->pos, prev_pos = pos;
1206
1207		ret = do_splice_to(in, &pos, pipe, len, flags);
1208		if (unlikely(ret <= 0))
1209			goto out_release;
1210
1211		read_len = ret;
1212		sd->total_len = read_len;
1213
1214		/*
 
 
 
 
 
 
 
 
 
1215		 * NOTE: nonblocking mode only applies to the input. We
1216		 * must not do the output in nonblocking mode as then we
1217		 * could get stuck data in the internal pipe:
1218		 */
1219		ret = actor(pipe, sd);
1220		if (unlikely(ret <= 0)) {
1221			sd->pos = prev_pos;
1222			goto out_release;
1223		}
1224
1225		bytes += ret;
1226		len -= ret;
1227		sd->pos = pos;
1228
1229		if (ret < read_len) {
1230			sd->pos = prev_pos + ret;
1231			goto out_release;
1232		}
1233	}
1234
1235done:
1236	pipe->nrbufs = pipe->curbuf = 0;
1237	file_accessed(in);
1238	return bytes;
1239
1240out_release:
1241	/*
1242	 * If we did an incomplete transfer we must release
1243	 * the pipe buffers in question:
1244	 */
1245	for (i = 0; i < pipe->buffers; i++) {
1246		struct pipe_buffer *buf = pipe->bufs + i;
1247
1248		if (buf->ops) {
1249			buf->ops->release(pipe, buf);
1250			buf->ops = NULL;
1251		}
1252	}
1253
1254	if (!bytes)
1255		bytes = ret;
1256
1257	goto done;
1258}
1259EXPORT_SYMBOL(splice_direct_to_actor);
1260
1261static int direct_splice_actor(struct pipe_inode_info *pipe,
1262			       struct splice_desc *sd)
1263{
1264	struct file *file = sd->u.file;
1265
1266	return do_splice_from(pipe, file, &file->f_pos, sd->total_len,
1267			      sd->flags);
1268}
1269
1270/**
1271 * do_splice_direct - splices data directly between two files
1272 * @in:		file to splice from
1273 * @ppos:	input file offset
1274 * @out:	file to splice to
 
1275 * @len:	number of bytes to splice
1276 * @flags:	splice modifier flags
1277 *
1278 * Description:
1279 *    For use by do_sendfile(). splice can easily emulate sendfile, but
1280 *    doing it in the application would incur an extra system call
1281 *    (splice in + splice out, as compared to just sendfile()). So this helper
1282 *    can splice directly through a process-private pipe.
1283 *
1284 */
1285long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
1286		      size_t len, unsigned int flags)
1287{
1288	struct splice_desc sd = {
1289		.len		= len,
1290		.total_len	= len,
1291		.flags		= flags,
1292		.pos		= *ppos,
1293		.u.file		= out,
 
1294	};
1295	long ret;
1296
 
 
 
 
 
 
 
 
 
 
1297	ret = splice_direct_to_actor(in, &sd, direct_splice_actor);
1298	if (ret > 0)
1299		*ppos = sd.pos;
1300
1301	return ret;
1302}
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1303
1304static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1305			       struct pipe_inode_info *opipe,
1306			       size_t len, unsigned int flags);
1307
1308/*
1309 * Determine where to splice to/from.
1310 */
1311static long do_splice(struct file *in, loff_t __user *off_in,
1312		      struct file *out, loff_t __user *off_out,
1313		      size_t len, unsigned int flags)
1314{
1315	struct pipe_inode_info *ipipe;
1316	struct pipe_inode_info *opipe;
1317	loff_t offset, *off;
1318	long ret;
1319
1320	ipipe = get_pipe_info(in);
1321	opipe = get_pipe_info(out);
1322
1323	if (ipipe && opipe) {
1324		if (off_in || off_out)
1325			return -ESPIPE;
1326
1327		if (!(in->f_mode & FMODE_READ))
1328			return -EBADF;
1329
1330		if (!(out->f_mode & FMODE_WRITE))
1331			return -EBADF;
1332
1333		/* Splicing to self would be fun, but... */
1334		if (ipipe == opipe)
1335			return -EINVAL;
1336
1337		return splice_pipe_to_pipe(ipipe, opipe, len, flags);
1338	}
1339
1340	if (ipipe) {
1341		if (off_in)
1342			return -ESPIPE;
1343		if (off_out) {
1344			if (!(out->f_mode & FMODE_PWRITE))
1345				return -EINVAL;
1346			if (copy_from_user(&offset, off_out, sizeof(loff_t)))
1347				return -EFAULT;
1348			off = &offset;
1349		} else
1350			off = &out->f_pos;
 
 
 
1351
1352		ret = do_splice_from(ipipe, out, off, len, flags);
 
 
 
 
 
1353
1354		if (off_out && copy_to_user(off_out, off, sizeof(loff_t)))
 
 
 
 
 
 
1355			ret = -EFAULT;
1356
1357		return ret;
1358	}
1359
1360	if (opipe) {
1361		if (off_out)
1362			return -ESPIPE;
1363		if (off_in) {
1364			if (!(in->f_mode & FMODE_PREAD))
1365				return -EINVAL;
1366			if (copy_from_user(&offset, off_in, sizeof(loff_t)))
1367				return -EFAULT;
1368			off = &offset;
1369		} else
1370			off = &in->f_pos;
1371
1372		ret = do_splice_to(in, off, opipe, len, flags);
1373
1374		if (off_in && copy_to_user(off_in, off, sizeof(loff_t)))
 
 
 
 
 
 
 
 
 
1375			ret = -EFAULT;
1376
1377		return ret;
1378	}
1379
1380	return -EINVAL;
1381}
1382
1383/*
1384 * Map an iov into an array of pages and offset/length tupples. With the
1385 * partial_page structure, we can map several non-contiguous ranges into
1386 * our ones pages[] map instead of splitting that operation into pieces.
1387 * Could easily be exported as a generic helper for other users, in which
1388 * case one would probably want to add a 'max_nr_pages' parameter as well.
1389 */
1390static int get_iovec_page_array(const struct iovec __user *iov,
1391				unsigned int nr_vecs, struct page **pages,
1392				struct partial_page *partial, int aligned,
1393				unsigned int pipe_buffers)
1394{
1395	int buffers = 0, error = 0;
1396
1397	while (nr_vecs) {
1398		unsigned long off, npages;
1399		struct iovec entry;
1400		void __user *base;
1401		size_t len;
1402		int i;
1403
1404		error = -EFAULT;
1405		if (copy_from_user(&entry, iov, sizeof(entry)))
1406			break;
1407
1408		base = entry.iov_base;
1409		len = entry.iov_len;
1410
1411		/*
1412		 * Sanity check this iovec. 0 read succeeds.
1413		 */
1414		error = 0;
1415		if (unlikely(!len))
1416			break;
1417		error = -EFAULT;
1418		if (!access_ok(VERIFY_READ, base, len))
1419			break;
1420
1421		/*
1422		 * Get this base offset and number of pages, then map
1423		 * in the user pages.
1424		 */
1425		off = (unsigned long) base & ~PAGE_MASK;
1426
1427		/*
1428		 * If asked for alignment, the offset must be zero and the
1429		 * length a multiple of the PAGE_SIZE.
1430		 */
1431		error = -EINVAL;
1432		if (aligned && (off || len & ~PAGE_MASK))
1433			break;
1434
1435		npages = (off + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1436		if (npages > pipe_buffers - buffers)
1437			npages = pipe_buffers - buffers;
1438
1439		error = get_user_pages_fast((unsigned long)base, npages,
1440					0, &pages[buffers]);
1441
1442		if (unlikely(error <= 0))
1443			break;
1444
1445		/*
1446		 * Fill this contiguous range into the partial page map.
1447		 */
1448		for (i = 0; i < error; i++) {
1449			const int plen = min_t(size_t, len, PAGE_SIZE - off);
1450
1451			partial[buffers].offset = off;
1452			partial[buffers].len = plen;
1453
1454			off = 0;
1455			len -= plen;
1456			buffers++;
1457		}
1458
1459		/*
1460		 * We didn't complete this iov, stop here since it probably
1461		 * means we have to move some of this into a pipe to
1462		 * be able to continue.
1463		 */
1464		if (len)
1465			break;
1466
1467		/*
1468		 * Don't continue if we mapped fewer pages than we asked for,
1469		 * or if we mapped the max number of pages that we have
1470		 * room for.
1471		 */
1472		if (error < npages || buffers == pipe_buffers)
1473			break;
1474
1475		nr_vecs--;
1476		iov++;
1477	}
1478
1479	if (buffers)
1480		return buffers;
1481
1482	return error;
1483}
1484
1485static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
1486			struct splice_desc *sd)
1487{
1488	char *src;
1489	int ret;
1490
1491	/*
1492	 * See if we can use the atomic maps, by prefaulting in the
1493	 * pages and doing an atomic copy
1494	 */
1495	if (!fault_in_pages_writeable(sd->u.userptr, sd->len)) {
1496		src = buf->ops->map(pipe, buf, 1);
1497		ret = __copy_to_user_inatomic(sd->u.userptr, src + buf->offset,
1498							sd->len);
1499		buf->ops->unmap(pipe, buf, src);
1500		if (!ret) {
1501			ret = sd->len;
1502			goto out;
1503		}
1504	}
1505
1506	/*
1507	 * No dice, use slow non-atomic map and copy
1508 	 */
1509	src = buf->ops->map(pipe, buf, 0);
1510
1511	ret = sd->len;
1512	if (copy_to_user(sd->u.userptr, src + buf->offset, sd->len))
1513		ret = -EFAULT;
1514
1515	buf->ops->unmap(pipe, buf, src);
1516out:
1517	if (ret > 0)
1518		sd->u.userptr += ret;
1519	return ret;
1520}
1521
1522/*
1523 * For lack of a better implementation, implement vmsplice() to userspace
1524 * as a simple copy of the pipes pages to the user iov.
1525 */
1526static long vmsplice_to_user(struct file *file, const struct iovec __user *iov,
1527			     unsigned long nr_segs, unsigned int flags)
1528{
1529	struct pipe_inode_info *pipe;
1530	struct splice_desc sd;
1531	ssize_t size;
1532	int error;
1533	long ret;
 
 
 
1534
1535	pipe = get_pipe_info(file);
1536	if (!pipe)
1537		return -EBADF;
1538
1539	pipe_lock(pipe);
1540
1541	error = ret = 0;
1542	while (nr_segs) {
1543		void __user *base;
1544		size_t len;
1545
1546		/*
1547		 * Get user address base and length for this iovec.
1548		 */
1549		error = get_user(base, &iov->iov_base);
1550		if (unlikely(error))
1551			break;
1552		error = get_user(len, &iov->iov_len);
1553		if (unlikely(error))
1554			break;
1555
1556		/*
1557		 * Sanity check this iovec. 0 read succeeds.
1558		 */
1559		if (unlikely(!len))
1560			break;
1561		if (unlikely(!base)) {
1562			error = -EFAULT;
1563			break;
1564		}
1565
1566		if (unlikely(!access_ok(VERIFY_WRITE, base, len))) {
1567			error = -EFAULT;
1568			break;
1569		}
1570
1571		sd.len = 0;
1572		sd.total_len = len;
1573		sd.flags = flags;
1574		sd.u.userptr = base;
1575		sd.pos = 0;
1576
1577		size = __splice_from_pipe(pipe, &sd, pipe_to_user);
1578		if (size < 0) {
1579			if (!ret)
1580				ret = size;
1581
1582			break;
1583		}
1584
1585		ret += size;
1586
1587		if (size < len)
1588			break;
1589
1590		nr_segs--;
1591		iov++;
 
 
 
 
 
 
 
 
1592	}
1593
1594	pipe_unlock(pipe);
1595
1596	if (!ret)
1597		ret = error;
1598
1599	return ret;
1600}
1601
1602/*
1603 * vmsplice splices a user address range into a pipe. It can be thought of
1604 * as splice-from-memory, where the regular splice is splice-from-file (or
1605 * to file). In both cases the output is a pipe, naturally.
1606 */
1607static long vmsplice_to_pipe(struct file *file, const struct iovec __user *iov,
1608			     unsigned long nr_segs, unsigned int flags)
1609{
1610	struct pipe_inode_info *pipe;
1611	struct page *pages[PIPE_DEF_BUFFERS];
1612	struct partial_page partial[PIPE_DEF_BUFFERS];
1613	struct splice_pipe_desc spd = {
1614		.pages = pages,
1615		.partial = partial,
1616		.flags = flags,
1617		.ops = &user_page_pipe_buf_ops,
1618		.spd_release = spd_release_page,
1619	};
1620	long ret;
 
 
 
 
1621
1622	pipe = get_pipe_info(file);
1623	if (!pipe)
1624		return -EBADF;
1625
1626	if (splice_grow_spd(pipe, &spd))
1627		return -ENOMEM;
1628
1629	spd.nr_pages = get_iovec_page_array(iov, nr_segs, spd.pages,
1630					    spd.partial, flags & SPLICE_F_GIFT,
1631					    pipe->buffers);
1632	if (spd.nr_pages <= 0)
1633		ret = spd.nr_pages;
1634	else
1635		ret = splice_to_pipe(pipe, &spd);
1636
1637	splice_shrink_spd(pipe, &spd);
 
 
 
 
 
 
 
1638	return ret;
1639}
1640
1641/*
1642 * Note that vmsplice only really supports true splicing _from_ user memory
1643 * to a pipe, not the other way around. Splicing from user memory is a simple
1644 * operation that can be supported without any funky alignment restrictions
1645 * or nasty vm tricks. We simply map in the user memory and fill them into
1646 * a pipe. The reverse isn't quite as easy, though. There are two possible
1647 * solutions for that:
1648 *
1649 *	- memcpy() the data internally, at which point we might as well just
1650 *	  do a regular read() on the buffer anyway.
1651 *	- Lots of nasty vm tricks, that are neither fast nor flexible (it
1652 *	  has restriction limitations on both ends of the pipe).
1653 *
1654 * Currently we punt and implement it as a normal copy, see pipe_to_user().
1655 *
1656 */
1657SYSCALL_DEFINE4(vmsplice, int, fd, const struct iovec __user *, iov,
1658		unsigned long, nr_segs, unsigned int, flags)
1659{
1660	struct file *file;
1661	long error;
1662	int fput;
1663
1664	if (unlikely(nr_segs > UIO_MAXIOV))
1665		return -EINVAL;
1666	else if (unlikely(!nr_segs))
1667		return 0;
1668
1669	error = -EBADF;
1670	file = fget_light(fd, &fput);
1671	if (file) {
1672		if (file->f_mode & FMODE_WRITE)
1673			error = vmsplice_to_pipe(file, iov, nr_segs, flags);
1674		else if (file->f_mode & FMODE_READ)
1675			error = vmsplice_to_user(file, iov, nr_segs, flags);
1676
1677		fput_light(file, fput);
1678	}
1679
1680	return error;
1681}
1682
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1683SYSCALL_DEFINE6(splice, int, fd_in, loff_t __user *, off_in,
1684		int, fd_out, loff_t __user *, off_out,
1685		size_t, len, unsigned int, flags)
1686{
 
1687	long error;
1688	struct file *in, *out;
1689	int fput_in, fput_out;
1690
1691	if (unlikely(!len))
1692		return 0;
1693
1694	error = -EBADF;
1695	in = fget_light(fd_in, &fput_in);
1696	if (in) {
1697		if (in->f_mode & FMODE_READ) {
1698			out = fget_light(fd_out, &fput_out);
1699			if (out) {
1700				if (out->f_mode & FMODE_WRITE)
1701					error = do_splice(in, off_in,
1702							  out, off_out,
1703							  len, flags);
1704				fput_light(out, fput_out);
1705			}
1706		}
1707
1708		fput_light(in, fput_in);
1709	}
1710
1711	return error;
1712}
1713
1714/*
1715 * Make sure there's data to read. Wait for input if we can, otherwise
1716 * return an appropriate error.
1717 */
1718static int ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1719{
1720	int ret;
1721
1722	/*
1723	 * Check ->nrbufs without the inode lock first. This function
1724	 * is speculative anyways, so missing one is ok.
1725	 */
1726	if (pipe->nrbufs)
1727		return 0;
1728
1729	ret = 0;
1730	pipe_lock(pipe);
1731
1732	while (!pipe->nrbufs) {
1733		if (signal_pending(current)) {
1734			ret = -ERESTARTSYS;
1735			break;
1736		}
1737		if (!pipe->writers)
1738			break;
1739		if (!pipe->waiting_writers) {
1740			if (flags & SPLICE_F_NONBLOCK) {
1741				ret = -EAGAIN;
1742				break;
1743			}
1744		}
1745		pipe_wait(pipe);
1746	}
1747
1748	pipe_unlock(pipe);
1749	return ret;
1750}
1751
1752/*
1753 * Make sure there's writeable room. Wait for room if we can, otherwise
1754 * return an appropriate error.
1755 */
1756static int opipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1757{
1758	int ret;
1759
1760	/*
1761	 * Check ->nrbufs without the inode lock first. This function
1762	 * is speculative anyways, so missing one is ok.
1763	 */
1764	if (pipe->nrbufs < pipe->buffers)
1765		return 0;
1766
1767	ret = 0;
1768	pipe_lock(pipe);
1769
1770	while (pipe->nrbufs >= pipe->buffers) {
1771		if (!pipe->readers) {
1772			send_sig(SIGPIPE, current, 0);
1773			ret = -EPIPE;
1774			break;
1775		}
1776		if (flags & SPLICE_F_NONBLOCK) {
1777			ret = -EAGAIN;
1778			break;
1779		}
1780		if (signal_pending(current)) {
1781			ret = -ERESTARTSYS;
1782			break;
1783		}
1784		pipe->waiting_writers++;
1785		pipe_wait(pipe);
1786		pipe->waiting_writers--;
1787	}
1788
1789	pipe_unlock(pipe);
1790	return ret;
1791}
1792
1793/*
1794 * Splice contents of ipipe to opipe.
1795 */
1796static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1797			       struct pipe_inode_info *opipe,
1798			       size_t len, unsigned int flags)
1799{
1800	struct pipe_buffer *ibuf, *obuf;
1801	int ret = 0, nbuf;
1802	bool input_wakeup = false;
1803
1804
1805retry:
1806	ret = ipipe_prep(ipipe, flags);
1807	if (ret)
1808		return ret;
1809
1810	ret = opipe_prep(opipe, flags);
1811	if (ret)
1812		return ret;
1813
1814	/*
1815	 * Potential ABBA deadlock, work around it by ordering lock
1816	 * grabbing by pipe info address. Otherwise two different processes
1817	 * could deadlock (one doing tee from A -> B, the other from B -> A).
1818	 */
1819	pipe_double_lock(ipipe, opipe);
1820
1821	do {
1822		if (!opipe->readers) {
1823			send_sig(SIGPIPE, current, 0);
1824			if (!ret)
1825				ret = -EPIPE;
1826			break;
1827		}
1828
1829		if (!ipipe->nrbufs && !ipipe->writers)
1830			break;
1831
1832		/*
1833		 * Cannot make any progress, because either the input
1834		 * pipe is empty or the output pipe is full.
1835		 */
1836		if (!ipipe->nrbufs || opipe->nrbufs >= opipe->buffers) {
1837			/* Already processed some buffers, break */
1838			if (ret)
1839				break;
1840
1841			if (flags & SPLICE_F_NONBLOCK) {
1842				ret = -EAGAIN;
1843				break;
1844			}
1845
1846			/*
1847			 * We raced with another reader/writer and haven't
1848			 * managed to process any buffers.  A zero return
1849			 * value means EOF, so retry instead.
1850			 */
1851			pipe_unlock(ipipe);
1852			pipe_unlock(opipe);
1853			goto retry;
1854		}
1855
1856		ibuf = ipipe->bufs + ipipe->curbuf;
1857		nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1);
1858		obuf = opipe->bufs + nbuf;
1859
1860		if (len >= ibuf->len) {
1861			/*
1862			 * Simply move the whole buffer from ipipe to opipe
1863			 */
1864			*obuf = *ibuf;
1865			ibuf->ops = NULL;
1866			opipe->nrbufs++;
1867			ipipe->curbuf = (ipipe->curbuf + 1) & (ipipe->buffers - 1);
1868			ipipe->nrbufs--;
1869			input_wakeup = true;
1870		} else {
1871			/*
1872			 * Get a reference to this pipe buffer,
1873			 * so we can copy the contents over.
1874			 */
1875			ibuf->ops->get(ipipe, ibuf);
1876			*obuf = *ibuf;
1877
1878			/*
1879			 * Don't inherit the gift flag, we need to
1880			 * prevent multiple steals of this page.
1881			 */
1882			obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1883
1884			obuf->len = len;
1885			opipe->nrbufs++;
1886			ibuf->offset += obuf->len;
1887			ibuf->len -= obuf->len;
1888		}
1889		ret += obuf->len;
1890		len -= obuf->len;
1891	} while (len);
1892
1893	pipe_unlock(ipipe);
1894	pipe_unlock(opipe);
1895
1896	/*
1897	 * If we put data in the output pipe, wakeup any potential readers.
1898	 */
1899	if (ret > 0)
1900		wakeup_pipe_readers(opipe);
1901
1902	if (input_wakeup)
1903		wakeup_pipe_writers(ipipe);
1904
1905	return ret;
1906}
1907
1908/*
1909 * Link contents of ipipe to opipe.
1910 */
1911static int link_pipe(struct pipe_inode_info *ipipe,
1912		     struct pipe_inode_info *opipe,
1913		     size_t len, unsigned int flags)
1914{
1915	struct pipe_buffer *ibuf, *obuf;
1916	int ret = 0, i = 0, nbuf;
1917
1918	/*
1919	 * Potential ABBA deadlock, work around it by ordering lock
1920	 * grabbing by pipe info address. Otherwise two different processes
1921	 * could deadlock (one doing tee from A -> B, the other from B -> A).
1922	 */
1923	pipe_double_lock(ipipe, opipe);
1924
1925	do {
1926		if (!opipe->readers) {
1927			send_sig(SIGPIPE, current, 0);
1928			if (!ret)
1929				ret = -EPIPE;
1930			break;
1931		}
1932
1933		/*
1934		 * If we have iterated all input buffers or ran out of
1935		 * output room, break.
1936		 */
1937		if (i >= ipipe->nrbufs || opipe->nrbufs >= opipe->buffers)
1938			break;
1939
1940		ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (ipipe->buffers-1));
1941		nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1);
1942
1943		/*
1944		 * Get a reference to this pipe buffer,
1945		 * so we can copy the contents over.
1946		 */
1947		ibuf->ops->get(ipipe, ibuf);
1948
1949		obuf = opipe->bufs + nbuf;
1950		*obuf = *ibuf;
1951
1952		/*
1953		 * Don't inherit the gift flag, we need to
1954		 * prevent multiple steals of this page.
1955		 */
1956		obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1957
1958		if (obuf->len > len)
1959			obuf->len = len;
1960
1961		opipe->nrbufs++;
1962		ret += obuf->len;
1963		len -= obuf->len;
1964		i++;
1965	} while (len);
1966
1967	/*
1968	 * return EAGAIN if we have the potential of some data in the
1969	 * future, otherwise just return 0
1970	 */
1971	if (!ret && ipipe->waiting_writers && (flags & SPLICE_F_NONBLOCK))
1972		ret = -EAGAIN;
1973
1974	pipe_unlock(ipipe);
1975	pipe_unlock(opipe);
1976
1977	/*
1978	 * If we put data in the output pipe, wakeup any potential readers.
1979	 */
1980	if (ret > 0)
1981		wakeup_pipe_readers(opipe);
1982
1983	return ret;
1984}
1985
1986/*
1987 * This is a tee(1) implementation that works on pipes. It doesn't copy
1988 * any data, it simply references the 'in' pages on the 'out' pipe.
1989 * The 'flags' used are the SPLICE_F_* variants, currently the only
1990 * applicable one is SPLICE_F_NONBLOCK.
1991 */
1992static long do_tee(struct file *in, struct file *out, size_t len,
1993		   unsigned int flags)
1994{
1995	struct pipe_inode_info *ipipe = get_pipe_info(in);
1996	struct pipe_inode_info *opipe = get_pipe_info(out);
1997	int ret = -EINVAL;
1998
1999	/*
2000	 * Duplicate the contents of ipipe to opipe without actually
2001	 * copying the data.
2002	 */
2003	if (ipipe && opipe && ipipe != opipe) {
2004		/*
2005		 * Keep going, unless we encounter an error. The ipipe/opipe
2006		 * ordering doesn't really matter.
2007		 */
2008		ret = ipipe_prep(ipipe, flags);
2009		if (!ret) {
2010			ret = opipe_prep(opipe, flags);
2011			if (!ret)
2012				ret = link_pipe(ipipe, opipe, len, flags);
2013		}
2014	}
2015
2016	return ret;
2017}
2018
2019SYSCALL_DEFINE4(tee, int, fdin, int, fdout, size_t, len, unsigned int, flags)
2020{
2021	struct file *in;
2022	int error, fput_in;
2023
2024	if (unlikely(!len))
2025		return 0;
2026
2027	error = -EBADF;
2028	in = fget_light(fdin, &fput_in);
2029	if (in) {
2030		if (in->f_mode & FMODE_READ) {
2031			int fput_out;
2032			struct file *out = fget_light(fdout, &fput_out);
2033
2034			if (out) {
2035				if (out->f_mode & FMODE_WRITE)
2036					error = do_tee(in, out, len, flags);
2037				fput_light(out, fput_out);
2038			}
2039		}
2040 		fput_light(in, fput_in);
2041 	}
2042
2043	return error;
2044}