splice.c 46.2 KB
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/*
 * "splice": joining two ropes together by interweaving their strands.
 *
 * This is the "extended pipe" functionality, where a pipe is used as
 * an arbitrary in-memory buffer. Think of a pipe as a small kernel
 * buffer that you can use to transfer data from one end to the other.
 *
 * The traditional unix read/write is extended with a "splice()" operation
 * that transfers data buffers to or from a pipe buffer.
 *
 * Named by Larry McVoy, original implementation from Linus, extended by
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 * Jens to support splicing to files, network, direct splicing, etc and
 * fixing lots of bugs.
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 *
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 * Copyright (C) 2005-2006 Jens Axboe <axboe@kernel.dk>
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 * Copyright (C) 2005-2006 Linus Torvalds <torvalds@osdl.org>
 * Copyright (C) 2006 Ingo Molnar <mingo@elte.hu>
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 *
 */
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/pagemap.h>
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#include <linux/splice.h>
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KAMEZAWA Hiroyuki 已提交
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#include <linux/memcontrol.h>
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#include <linux/mm_inline.h>
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#include <linux/swap.h>
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#include <linux/writeback.h>
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#include <linux/export.h>
29
#include <linux/syscalls.h>
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#include <linux/uio.h>
31
#include <linux/security.h>
32
#include <linux/gfp.h>
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#include <linux/socket.h>
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#include <linux/compat.h>
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#include "internal.h"
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/*
 * Attempt to steal a page from a pipe buffer. This should perhaps go into
 * a vm helper function, it's already simplified quite a bit by the
 * addition of remove_mapping(). If success is returned, the caller may
 * attempt to reuse this page for another destination.
 */
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static int page_cache_pipe_buf_steal(struct pipe_inode_info *pipe,
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				     struct pipe_buffer *buf)
{
	struct page *page = buf->page;
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	struct address_space *mapping;
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49 50
	lock_page(page);

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	mapping = page_mapping(page);
	if (mapping) {
		WARN_ON(!PageUptodate(page));
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		/*
		 * At least for ext2 with nobh option, we need to wait on
		 * writeback completing on this page, since we'll remove it
		 * from the pagecache.  Otherwise truncate wont wait on the
		 * page, allowing the disk blocks to be reused by someone else
		 * before we actually wrote our data to them. fs corruption
		 * ensues.
		 */
		wait_on_page_writeback(page);
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65 66
		if (page_has_private(page) &&
		    !try_to_release_page(page, GFP_KERNEL))
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			goto out_unlock;
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		/*
		 * If we succeeded in removing the mapping, set LRU flag
		 * and return good.
		 */
		if (remove_mapping(mapping, page)) {
			buf->flags |= PIPE_BUF_FLAG_LRU;
			return 0;
		}
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	}
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	/*
	 * Raced with truncate or failed to remove page from current
	 * address space, unlock and return failure.
	 */
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out_unlock:
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	unlock_page(page);
	return 1;
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}

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static void page_cache_pipe_buf_release(struct pipe_inode_info *pipe,
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					struct pipe_buffer *buf)
{
	page_cache_release(buf->page);
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	buf->flags &= ~PIPE_BUF_FLAG_LRU;
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}

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/*
 * Check whether the contents of buf is OK to access. Since the content
 * is a page cache page, IO may be in flight.
 */
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static int page_cache_pipe_buf_confirm(struct pipe_inode_info *pipe,
				       struct pipe_buffer *buf)
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{
	struct page *page = buf->page;
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	int err;
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	if (!PageUptodate(page)) {
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		lock_page(page);

		/*
		 * Page got truncated/unhashed. This will cause a 0-byte
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		 * splice, if this is the first page.
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		 */
		if (!page->mapping) {
			err = -ENODATA;
			goto error;
		}
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		/*
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		 * Uh oh, read-error from disk.
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		 */
		if (!PageUptodate(page)) {
			err = -EIO;
			goto error;
		}

		/*
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		 * Page is ok afterall, we are done.
127
		 */
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		unlock_page(page);
	}

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	return 0;
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error:
	unlock_page(page);
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	return err;
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}

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const struct pipe_buf_operations page_cache_pipe_buf_ops = {
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	.can_merge = 0,
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	.confirm = page_cache_pipe_buf_confirm,
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	.release = page_cache_pipe_buf_release,
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	.steal = page_cache_pipe_buf_steal,
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	.get = generic_pipe_buf_get,
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};

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static int user_page_pipe_buf_steal(struct pipe_inode_info *pipe,
				    struct pipe_buffer *buf)
{
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	if (!(buf->flags & PIPE_BUF_FLAG_GIFT))
		return 1;

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	buf->flags |= PIPE_BUF_FLAG_LRU;
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	return generic_pipe_buf_steal(pipe, buf);
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}

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static const struct pipe_buf_operations user_page_pipe_buf_ops = {
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	.can_merge = 0,
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	.confirm = generic_pipe_buf_confirm,
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	.release = page_cache_pipe_buf_release,
	.steal = user_page_pipe_buf_steal,
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	.get = generic_pipe_buf_get,
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};

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static void wakeup_pipe_readers(struct pipe_inode_info *pipe)
{
	smp_mb();
	if (waitqueue_active(&pipe->wait))
		wake_up_interruptible(&pipe->wait);
	kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
}

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/**
 * splice_to_pipe - fill passed data into a pipe
 * @pipe:	pipe to fill
 * @spd:	data to fill
 *
 * Description:
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 *    @spd contains a map of pages and len/offset tuples, along with
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 *    the struct pipe_buf_operations associated with these pages. This
 *    function will link that data to the pipe.
 *
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 */
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ssize_t splice_to_pipe(struct pipe_inode_info *pipe,
		       struct splice_pipe_desc *spd)
184
{
185
	unsigned int spd_pages = spd->nr_pages;
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	int ret, do_wakeup, page_nr;
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	if (!spd_pages)
		return 0;

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	ret = 0;
	do_wakeup = 0;
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	page_nr = 0;
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195
	pipe_lock(pipe);
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	for (;;) {
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		if (!pipe->readers) {
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			send_sig(SIGPIPE, current, 0);
			if (!ret)
				ret = -EPIPE;
			break;
		}

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		if (pipe->nrbufs < pipe->buffers) {
			int newbuf = (pipe->curbuf + pipe->nrbufs) & (pipe->buffers - 1);
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			struct pipe_buffer *buf = pipe->bufs + newbuf;
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			buf->page = spd->pages[page_nr];
			buf->offset = spd->partial[page_nr].offset;
			buf->len = spd->partial[page_nr].len;
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			buf->private = spd->partial[page_nr].private;
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			buf->ops = spd->ops;
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			if (spd->flags & SPLICE_F_GIFT)
				buf->flags |= PIPE_BUF_FLAG_GIFT;

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			pipe->nrbufs++;
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			page_nr++;
			ret += buf->len;

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			if (pipe->files)
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				do_wakeup = 1;
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224
			if (!--spd->nr_pages)
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				break;
226
			if (pipe->nrbufs < pipe->buffers)
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				continue;

			break;
		}

232
		if (spd->flags & SPLICE_F_NONBLOCK) {
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			if (!ret)
				ret = -EAGAIN;
			break;
		}

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

		if (do_wakeup) {
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			smp_mb();
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			if (waitqueue_active(&pipe->wait))
				wake_up_interruptible_sync(&pipe->wait);
			kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
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			do_wakeup = 0;
		}

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		pipe->waiting_writers++;
		pipe_wait(pipe);
		pipe->waiting_writers--;
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	}

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	pipe_unlock(pipe);
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Namhyung Kim 已提交
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	if (do_wakeup)
		wakeup_pipe_readers(pipe);
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262
	while (page_nr < spd_pages)
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		spd->spd_release(spd, page_nr++);
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	return ret;
}
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EXPORT_SYMBOL_GPL(splice_to_pipe);
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void spd_release_page(struct splice_pipe_desc *spd, unsigned int i)
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{
	page_cache_release(spd->pages[i]);
}

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/*
 * Check if we need to grow the arrays holding pages and partial page
 * descriptions.
 */
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int splice_grow_spd(const struct pipe_inode_info *pipe, struct splice_pipe_desc *spd)
279
{
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	unsigned int buffers = ACCESS_ONCE(pipe->buffers);

	spd->nr_pages_max = buffers;
	if (buffers <= PIPE_DEF_BUFFERS)
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		return 0;

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	spd->pages = kmalloc(buffers * sizeof(struct page *), GFP_KERNEL);
	spd->partial = kmalloc(buffers * sizeof(struct partial_page), GFP_KERNEL);
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	if (spd->pages && spd->partial)
		return 0;

	kfree(spd->pages);
	kfree(spd->partial);
	return -ENOMEM;
}

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void splice_shrink_spd(struct splice_pipe_desc *spd)
298
{
299
	if (spd->nr_pages_max <= PIPE_DEF_BUFFERS)
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		return;

	kfree(spd->pages);
	kfree(spd->partial);
}

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static int
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__generic_file_splice_read(struct file *in, loff_t *ppos,
			   struct pipe_inode_info *pipe, size_t len,
			   unsigned int flags)
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{
	struct address_space *mapping = in->f_mapping;
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	unsigned int loff, nr_pages, req_pages;
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	struct page *pages[PIPE_DEF_BUFFERS];
	struct partial_page partial[PIPE_DEF_BUFFERS];
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	struct page *page;
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	pgoff_t index, end_index;
	loff_t isize;
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	int error, page_nr;
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	struct splice_pipe_desc spd = {
		.pages = pages,
		.partial = partial,
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		.nr_pages_max = PIPE_DEF_BUFFERS,
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		.flags = flags,
		.ops = &page_cache_pipe_buf_ops,
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		.spd_release = spd_release_page,
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	};
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	if (splice_grow_spd(pipe, &spd))
		return -ENOMEM;

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	index = *ppos >> PAGE_CACHE_SHIFT;
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	loff = *ppos & ~PAGE_CACHE_MASK;
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Fengguang Wu 已提交
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	req_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
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	nr_pages = min(req_pages, spd.nr_pages_max);
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	/*
	 * Lookup the (hopefully) full range of pages we need.
	 */
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	spd.nr_pages = find_get_pages_contig(mapping, index, nr_pages, spd.pages);
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	index += spd.nr_pages;
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	/*
	 * If find_get_pages_contig() returned fewer pages than we needed,
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	 * readahead/allocate the rest and fill in the holes.
345
	 */
346
	if (spd.nr_pages < nr_pages)
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		page_cache_sync_readahead(mapping, &in->f_ra, in,
				index, req_pages - spd.nr_pages);
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350
	error = 0;
351
	while (spd.nr_pages < nr_pages) {
352
		/*
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		 * Page could be there, find_get_pages_contig() breaks on
		 * the first hole.
355
		 */
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		page = find_get_page(mapping, index);
		if (!page) {
			/*
359
			 * page didn't exist, allocate one.
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			 */
			page = page_cache_alloc_cold(mapping);
			if (!page)
				break;

			error = add_to_page_cache_lru(page, mapping, index,
366
				   mapping_gfp_constraint(mapping, GFP_KERNEL));
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			if (unlikely(error)) {
				page_cache_release(page);
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				if (error == -EEXIST)
					continue;
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				break;
			}
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			/*
			 * add_to_page_cache() locks the page, unlock it
			 * to avoid convoluting the logic below even more.
			 */
			unlock_page(page);
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		}

380
		spd.pages[spd.nr_pages++] = page;
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		index++;
	}

	/*
	 * Now loop over the map and see if we need to start IO on any
	 * pages, fill in the partial map, etc.
	 */
	index = *ppos >> PAGE_CACHE_SHIFT;
	nr_pages = spd.nr_pages;
	spd.nr_pages = 0;
	for (page_nr = 0; page_nr < nr_pages; page_nr++) {
		unsigned int this_len;

		if (!len)
			break;

		/*
		 * this_len is the max we'll use from this page
		 */
		this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff);
401
		page = spd.pages[page_nr];
402

403
		if (PageReadahead(page))
404
			page_cache_async_readahead(mapping, &in->f_ra, in,
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Fengguang Wu 已提交
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					page, index, req_pages - page_nr);
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		/*
		 * If the page isn't uptodate, we may need to start io on it
		 */
		if (!PageUptodate(page)) {
411
			lock_page(page);
412 413

			/*
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			 * Page was truncated, or invalidated by the
			 * filesystem.  Redo the find/create, but this time the
			 * page is kept locked, so there's no chance of another
			 * race with truncate/invalidate.
418 419 420
			 */
			if (!page->mapping) {
				unlock_page(page);
421
retry_lookup:
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				page = find_or_create_page(mapping, index,
						mapping_gfp_mask(mapping));

				if (!page) {
					error = -ENOMEM;
					break;
				}
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				page_cache_release(spd.pages[page_nr]);
				spd.pages[page_nr] = page;
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			}
			/*
			 * page was already under io and is now done, great
			 */
			if (PageUptodate(page)) {
				unlock_page(page);
				goto fill_it;
			}
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			/*
			 * need to read in the page
			 */
			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

451 452
				break;
			}
453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468
		}
fill_it:
		/*
		 * i_size must be checked after PageUptodate.
		 */
		isize = i_size_read(mapping->host);
		end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
		if (unlikely(!isize || index > end_index))
			break;

		/*
		 * if this is the last page, see if we need to shrink
		 * the length and stop
		 */
		if (end_index == index) {
			unsigned int plen;
469 470

			/*
471
			 * max good bytes in this page
472
			 */
473 474
			plen = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
			if (plen <= loff)
475 476 477
				break;

			/*
478
			 * force quit after adding this page
479
			 */
480 481
			this_len = min(this_len, plen - loff);
			len = this_len;
482
		}
483

484 485
		spd.partial[page_nr].offset = loff;
		spd.partial[page_nr].len = this_len;
486
		len -= this_len;
487
		loff = 0;
488 489
		spd.nr_pages++;
		index++;
490 491
	}

492
	/*
493
	 * Release any pages at the end, if we quit early. 'page_nr' is how far
494 495 496
	 * we got, 'nr_pages' is how many pages are in the map.
	 */
	while (page_nr < nr_pages)
497
		page_cache_release(spd.pages[page_nr++]);
498
	in->f_ra.prev_pos = (loff_t)index << PAGE_CACHE_SHIFT;
499

500
	if (spd.nr_pages)
501
		error = splice_to_pipe(pipe, &spd);
502

503
	splice_shrink_spd(&spd);
504
	return error;
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}

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/**
 * generic_file_splice_read - splice data from file to a pipe
 * @in:		file to splice from
510
 * @ppos:	position in @in
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 * @pipe:	pipe to splice to
 * @len:	number of bytes to splice
 * @flags:	splice modifier flags
 *
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 * Description:
 *    Will read pages from given file and fill them into a pipe. Can be
 *    used as long as the address_space operations for the source implements
 *    a readpage() hook.
 *
520
 */
521 522 523
ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
				 struct pipe_inode_info *pipe, size_t len,
				 unsigned int flags)
524
{
525
	loff_t isize, left;
526
	int ret;
527

528 529 530
	if (IS_DAX(in->f_mapping->host))
		return default_file_splice_read(in, ppos, pipe, len, flags);

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	isize = i_size_read(in->f_mapping->host);
	if (unlikely(*ppos >= isize))
		return 0;

	left = isize - *ppos;
	if (unlikely(left < len))
		len = left;
538

539
	ret = __generic_file_splice_read(in, ppos, pipe, len, flags);
540
	if (ret > 0) {
541
		*ppos += ret;
542 543
		file_accessed(in);
	}
544 545 546

	return ret;
}
547 548
EXPORT_SYMBOL(generic_file_splice_read);

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static const struct pipe_buf_operations default_pipe_buf_ops = {
	.can_merge = 0,
	.confirm = generic_pipe_buf_confirm,
	.release = generic_pipe_buf_release,
	.steal = generic_pipe_buf_steal,
	.get = generic_pipe_buf_get,
};

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Miklos Szeredi 已提交
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static int generic_pipe_buf_nosteal(struct pipe_inode_info *pipe,
				    struct pipe_buffer *buf)
{
	return 1;
}

/* Pipe buffer operations for a socket and similar. */
const struct pipe_buf_operations nosteal_pipe_buf_ops = {
	.can_merge = 0,
	.confirm = generic_pipe_buf_confirm,
	.release = generic_pipe_buf_release,
	.steal = generic_pipe_buf_nosteal,
	.get = generic_pipe_buf_get,
};
EXPORT_SYMBOL(nosteal_pipe_buf_ops);

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static ssize_t kernel_readv(struct file *file, const struct iovec *vec,
			    unsigned long vlen, loff_t offset)
{
	mm_segment_t old_fs;
	loff_t pos = offset;
	ssize_t res;

	old_fs = get_fs();
	set_fs(get_ds());
	/* The cast to a user pointer is valid due to the set_fs() */
	res = vfs_readv(file, (const struct iovec __user *)vec, vlen, &pos);
	set_fs(old_fs);

	return res;
}

589
ssize_t kernel_write(struct file *file, const char *buf, size_t count,
590
			    loff_t pos)
591 592 593 594 595 596 597
{
	mm_segment_t old_fs;
	ssize_t res;

	old_fs = get_fs();
	set_fs(get_ds());
	/* 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);
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	set_fs(old_fs);

	return res;
}
603
EXPORT_SYMBOL(kernel_write);
604

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ssize_t default_file_splice_read(struct file *in, loff_t *ppos,
				 struct pipe_inode_info *pipe, size_t len,
				 unsigned int flags)
{
	unsigned int nr_pages;
	unsigned int nr_freed;
	size_t offset;
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	struct page *pages[PIPE_DEF_BUFFERS];
	struct partial_page partial[PIPE_DEF_BUFFERS];
	struct iovec *vec, __vec[PIPE_DEF_BUFFERS];
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	ssize_t res;
	size_t this_len;
	int error;
	int i;
	struct splice_pipe_desc spd = {
		.pages = pages,
		.partial = partial,
622
		.nr_pages_max = PIPE_DEF_BUFFERS,
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		.flags = flags,
		.ops = &default_pipe_buf_ops,
		.spd_release = spd_release_page,
	};

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	if (splice_grow_spd(pipe, &spd))
		return -ENOMEM;

	res = -ENOMEM;
	vec = __vec;
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	if (spd.nr_pages_max > PIPE_DEF_BUFFERS) {
		vec = kmalloc(spd.nr_pages_max * sizeof(struct iovec), GFP_KERNEL);
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		if (!vec)
			goto shrink_ret;
	}

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	offset = *ppos & ~PAGE_CACHE_MASK;
	nr_pages = (len + offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;

642
	for (i = 0; i < nr_pages && i < spd.nr_pages_max && len; i++) {
643 644
		struct page *page;

645
		page = alloc_page(GFP_USER);
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		error = -ENOMEM;
		if (!page)
			goto err;

		this_len = min_t(size_t, len, PAGE_CACHE_SIZE - offset);
651
		vec[i].iov_base = (void __user *) page_address(page);
652
		vec[i].iov_len = this_len;
653
		spd.pages[i] = page;
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		spd.nr_pages++;
		len -= this_len;
		offset = 0;
	}

	res = kernel_readv(in, vec, spd.nr_pages, *ppos);
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Andrew Morton 已提交
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	if (res < 0) {
		error = res;
662
		goto err;
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Andrew Morton 已提交
663
	}
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	error = 0;
	if (!res)
		goto err;

	nr_freed = 0;
	for (i = 0; i < spd.nr_pages; i++) {
		this_len = min_t(size_t, vec[i].iov_len, res);
672 673
		spd.partial[i].offset = 0;
		spd.partial[i].len = this_len;
674
		if (!this_len) {
675 676
			__free_page(spd.pages[i]);
			spd.pages[i] = NULL;
677 678 679 680 681 682 683 684 685 686
			nr_freed++;
		}
		res -= this_len;
	}
	spd.nr_pages -= nr_freed;

	res = splice_to_pipe(pipe, &spd);
	if (res > 0)
		*ppos += res;

687 688 689
shrink_ret:
	if (vec != __vec)
		kfree(vec);
690
	splice_shrink_spd(&spd);
691 692 693
	return res;

err:
694
	for (i = 0; i < spd.nr_pages; i++)
695
		__free_page(spd.pages[i]);
696

697 698
	res = error;
	goto shrink_ret;
699 700 701
}
EXPORT_SYMBOL(default_file_splice_read);

702
/*
703
 * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
J
Jens Axboe 已提交
704
 * using sendpage(). Return the number of bytes sent.
705
 */
706
static int pipe_to_sendpage(struct pipe_inode_info *pipe,
707 708
			    struct pipe_buffer *buf, struct splice_desc *sd)
{
709
	struct file *file = sd->u.file;
710
	loff_t pos = sd->pos;
711
	int more;
712

A
Al Viro 已提交
713
	if (!likely(file->f_op->sendpage))
714 715
		return -EINVAL;

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

721 722
	return file->f_op->sendpage(file, buf->page, buf->offset,
				    sd->len, &pos, more);
723 724
}

725 726 727 728 729 730 731 732
static void wakeup_pipe_writers(struct pipe_inode_info *pipe)
{
	smp_mb();
	if (waitqueue_active(&pipe->wait))
		wake_up_interruptible(&pipe->wait);
	kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
}

733
/**
734
 * splice_from_pipe_feed - feed available data from a pipe to a file
735 736 737 738 739
 * @pipe:	pipe to splice from
 * @sd:		information to @actor
 * @actor:	handler that splices the data
 *
 * Description:
740 741 742 743 744 745 746
 *    This function loops over the pipe and calls @actor to do the
 *    actual moving of a single struct pipe_buffer to the desired
 *    destination.  It returns when there's no more buffers left in
 *    the pipe or if the requested number of bytes (@sd->total_len)
 *    have been copied.  It returns a positive number (one) if the
 *    pipe needs to be filled with more data, zero if the required
 *    number of bytes have been copied and -errno on error.
747
 *
748 749 750 751
 *    This, together with splice_from_pipe_{begin,end,next}, may be
 *    used to implement the functionality of __splice_from_pipe() when
 *    locking is required around copying the pipe buffers to the
 *    destination.
752
 */
A
Al Viro 已提交
753
static int splice_from_pipe_feed(struct pipe_inode_info *pipe, struct splice_desc *sd,
754
			  splice_actor *actor)
755
{
756
	int ret;
757

758 759 760
	while (pipe->nrbufs) {
		struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
		const struct pipe_buf_operations *ops = buf->ops;
761

762 763 764
		sd->len = buf->len;
		if (sd->len > sd->total_len)
			sd->len = sd->total_len;
765

766 767
		ret = buf->ops->confirm(pipe, buf);
		if (unlikely(ret)) {
768 769 770 771
			if (ret == -ENODATA)
				ret = 0;
			return ret;
		}
772 773 774 775 776

		ret = actor(pipe, buf, sd);
		if (ret <= 0)
			return ret;

777 778 779 780 781 782 783 784 785 786 787
		buf->offset += ret;
		buf->len -= ret;

		sd->num_spliced += ret;
		sd->len -= ret;
		sd->pos += ret;
		sd->total_len -= ret;

		if (!buf->len) {
			buf->ops = NULL;
			ops->release(pipe, buf);
788
			pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1);
789
			pipe->nrbufs--;
A
Al Viro 已提交
790
			if (pipe->files)
791 792
				sd->need_wakeup = true;
		}
793

794 795 796
		if (!sd->total_len)
			return 0;
	}
797

798 799
	return 1;
}
800

801 802 803 804 805 806 807 808 809 810
/**
 * splice_from_pipe_next - wait for some data to splice from
 * @pipe:	pipe to splice from
 * @sd:		information about the splice operation
 *
 * Description:
 *    This function will wait for some data and return a positive
 *    value (one) if pipe buffers are available.  It will return zero
 *    or -errno if no more data needs to be spliced.
 */
A
Al Viro 已提交
811
static int splice_from_pipe_next(struct pipe_inode_info *pipe, struct splice_desc *sd)
812
{
813 814 815 816 817 818 819
	/*
	 * Check for signal early to make process killable when there are
	 * always buffers available
	 */
	if (signal_pending(current))
		return -ERESTARTSYS;

820 821 822
	while (!pipe->nrbufs) {
		if (!pipe->writers)
			return 0;
J
Jens Axboe 已提交
823

824 825
		if (!pipe->waiting_writers && sd->num_spliced)
			return 0;
I
Ingo Molnar 已提交
826

827 828
		if (sd->flags & SPLICE_F_NONBLOCK)
			return -EAGAIN;
829

830 831
		if (signal_pending(current))
			return -ERESTARTSYS;
832

833 834 835
		if (sd->need_wakeup) {
			wakeup_pipe_writers(pipe);
			sd->need_wakeup = false;
836 837
		}

838 839
		pipe_wait(pipe);
	}
840

841 842
	return 1;
}
843

844 845
/**
 * splice_from_pipe_begin - start splicing from pipe
846
 * @sd:		information about the splice operation
847 848 849 850 851 852
 *
 * Description:
 *    This function should be called before a loop containing
 *    splice_from_pipe_next() and splice_from_pipe_feed() to
 *    initialize the necessary fields of @sd.
 */
A
Al Viro 已提交
853
static void splice_from_pipe_begin(struct splice_desc *sd)
854 855 856 857
{
	sd->num_spliced = 0;
	sd->need_wakeup = false;
}
858

859 860 861 862 863 864 865 866 867 868
/**
 * splice_from_pipe_end - finish splicing from pipe
 * @pipe:	pipe to splice from
 * @sd:		information about the splice operation
 *
 * Description:
 *    This function will wake up pipe writers if necessary.  It should
 *    be called after a loop containing splice_from_pipe_next() and
 *    splice_from_pipe_feed().
 */
A
Al Viro 已提交
869
static void splice_from_pipe_end(struct pipe_inode_info *pipe, struct splice_desc *sd)
870 871 872 873
{
	if (sd->need_wakeup)
		wakeup_pipe_writers(pipe);
}
874

875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891
/**
 * __splice_from_pipe - splice data from a pipe to given actor
 * @pipe:	pipe to splice from
 * @sd:		information to @actor
 * @actor:	handler that splices the data
 *
 * Description:
 *    This function does little more than loop over the pipe and call
 *    @actor to do the actual moving of a single struct pipe_buffer to
 *    the desired destination. See pipe_to_file, pipe_to_sendpage, or
 *    pipe_to_user.
 *
 */
ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd,
			   splice_actor *actor)
{
	int ret;
892

893 894
	splice_from_pipe_begin(sd);
	do {
J
Jan Kara 已提交
895
		cond_resched();
896 897 898 899 900 901 902
		ret = splice_from_pipe_next(pipe, sd);
		if (ret > 0)
			ret = splice_from_pipe_feed(pipe, sd, actor);
	} while (ret > 0);
	splice_from_pipe_end(pipe, sd);

	return sd->num_spliced ? sd->num_spliced : ret;
903
}
M
Mark Fasheh 已提交
904
EXPORT_SYMBOL(__splice_from_pipe);
905

906 907 908 909 910 911 912 913 914 915
/**
 * splice_from_pipe - splice data from a pipe to a file
 * @pipe:	pipe to splice from
 * @out:	file to splice to
 * @ppos:	position in @out
 * @len:	how many bytes to splice
 * @flags:	splice modifier flags
 * @actor:	handler that splices the data
 *
 * Description:
916
 *    See __splice_from_pipe. This function locks the pipe inode,
917 918 919
 *    otherwise it's identical to __splice_from_pipe().
 *
 */
920 921 922 923 924
ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
			 loff_t *ppos, size_t len, unsigned int flags,
			 splice_actor *actor)
{
	ssize_t ret;
J
Jens Axboe 已提交
925 926 927 928
	struct splice_desc sd = {
		.total_len = len,
		.flags = flags,
		.pos = *ppos,
929
		.u.file = out,
J
Jens Axboe 已提交
930
	};
931

932
	pipe_lock(pipe);
J
Jens Axboe 已提交
933
	ret = __splice_from_pipe(pipe, &sd, actor);
934
	pipe_unlock(pipe);
935 936 937 938

	return ret;
}

A
Al Viro 已提交
939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018
/**
 * iter_file_splice_write - splice data from a pipe to a file
 * @pipe:	pipe info
 * @out:	file to write to
 * @ppos:	position in @out
 * @len:	number of bytes to splice
 * @flags:	splice modifier flags
 *
 * Description:
 *    Will either move or copy pages (determined by @flags options) from
 *    the given pipe inode to the given file.
 *    This one is ->write_iter-based.
 *
 */
ssize_t
iter_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
			  loff_t *ppos, size_t len, unsigned int flags)
{
	struct splice_desc sd = {
		.total_len = len,
		.flags = flags,
		.pos = *ppos,
		.u.file = out,
	};
	int nbufs = pipe->buffers;
	struct bio_vec *array = kcalloc(nbufs, sizeof(struct bio_vec),
					GFP_KERNEL);
	ssize_t ret;

	if (unlikely(!array))
		return -ENOMEM;

	pipe_lock(pipe);

	splice_from_pipe_begin(&sd);
	while (sd.total_len) {
		struct iov_iter from;
		size_t left;
		int n, idx;

		ret = splice_from_pipe_next(pipe, &sd);
		if (ret <= 0)
			break;

		if (unlikely(nbufs < pipe->buffers)) {
			kfree(array);
			nbufs = pipe->buffers;
			array = kcalloc(nbufs, sizeof(struct bio_vec),
					GFP_KERNEL);
			if (!array) {
				ret = -ENOMEM;
				break;
			}
		}

		/* build the vector */
		left = sd.total_len;
		for (n = 0, idx = pipe->curbuf; left && n < pipe->nrbufs; n++, idx++) {
			struct pipe_buffer *buf = pipe->bufs + idx;
			size_t this_len = buf->len;

			if (this_len > left)
				this_len = left;

			if (idx == pipe->buffers - 1)
				idx = -1;

			ret = buf->ops->confirm(pipe, buf);
			if (unlikely(ret)) {
				if (ret == -ENODATA)
					ret = 0;
				goto done;
			}

			array[n].bv_page = buf->page;
			array[n].bv_len = this_len;
			array[n].bv_offset = buf->offset;
			left -= this_len;
		}

A
Al Viro 已提交
1019 1020
		iov_iter_bvec(&from, ITER_BVEC | WRITE, array, n,
			      sd.total_len - left);
1021
		ret = vfs_iter_write(out, &from, &sd.pos);
A
Al Viro 已提交
1022 1023 1024 1025 1026
		if (ret <= 0)
			break;

		sd.num_spliced += ret;
		sd.total_len -= ret;
1027
		*ppos = sd.pos;
A
Al Viro 已提交
1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062

		/* dismiss the fully eaten buffers, adjust the partial one */
		while (ret) {
			struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
			if (ret >= buf->len) {
				const struct pipe_buf_operations *ops = buf->ops;
				ret -= buf->len;
				buf->len = 0;
				buf->ops = NULL;
				ops->release(pipe, buf);
				pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1);
				pipe->nrbufs--;
				if (pipe->files)
					sd.need_wakeup = true;
			} else {
				buf->offset += ret;
				buf->len -= ret;
				ret = 0;
			}
		}
	}
done:
	kfree(array);
	splice_from_pipe_end(pipe, &sd);

	pipe_unlock(pipe);

	if (sd.num_spliced)
		ret = sd.num_spliced;

	return ret;
}

EXPORT_SYMBOL(iter_file_splice_write);

1063 1064
static int write_pipe_buf(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
			  struct splice_desc *sd)
1065
{
1066 1067
	int ret;
	void *data;
1068
	loff_t tmp = sd->pos;
1069

A
Al Viro 已提交
1070
	data = kmap(buf->page);
1071
	ret = __kernel_write(sd->u.file, data + buf->offset, sd->len, &tmp);
A
Al Viro 已提交
1072
	kunmap(buf->page);
1073 1074

	return ret;
1075 1076 1077 1078 1079 1080
}

static ssize_t default_file_splice_write(struct pipe_inode_info *pipe,
					 struct file *out, loff_t *ppos,
					 size_t len, unsigned int flags)
{
1081
	ssize_t ret;
1082

1083 1084 1085
	ret = splice_from_pipe(pipe, out, ppos, len, flags, write_pipe_buf);
	if (ret > 0)
		*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 1096 1097
 * @len:	number of bytes to splice
 * @flags:	splice modifier flags
 *
1098 1099 1100
 * Description:
 *    Will send @len bytes from the pipe to a network socket. No data copying
 *    is involved.
1101 1102
 *
 */
1103
ssize_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
}

1109
EXPORT_SYMBOL(generic_splice_sendpage);
J
Jeff Garzik 已提交
1110

1111 1112 1113
/*
 * Attempt to initiate a splice from pipe to file.
 */
1114
static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
1115
			   loff_t *ppos, size_t len, unsigned int flags)
1116
{
1117 1118
	ssize_t (*splice_write)(struct pipe_inode_info *, struct file *,
				loff_t *, size_t, unsigned int);
1119

A
Al Viro 已提交
1120
	if (out->f_op->splice_write)
1121 1122
		splice_write = out->f_op->splice_write;
	else
1123 1124
		splice_write = default_file_splice_write;

1125
	return splice_write(pipe, out, ppos, len, flags);
1126 1127
}

1128 1129 1130
/*
 * Attempt to initiate a splice from a file to a pipe.
 */
1131 1132 1133
static long do_splice_to(struct file *in, loff_t *ppos,
			 struct pipe_inode_info *pipe, size_t len,
			 unsigned int flags)
1134
{
1135 1136
	ssize_t (*splice_read)(struct file *, loff_t *,
			       struct pipe_inode_info *, size_t, unsigned int);
1137 1138
	int ret;

1139
	if (unlikely(!(in->f_mode & FMODE_READ)))
1140 1141
		return -EBADF;

1142
	ret = rw_verify_area(READ, in, ppos, len);
1143 1144 1145
	if (unlikely(ret < 0))
		return ret;

A
Al Viro 已提交
1146
	if (in->f_op->splice_read)
1147 1148
		splice_read = in->f_op->splice_read;
	else
1149 1150 1151
		splice_read = default_file_splice_read;

	return splice_read(in, ppos, pipe, len, flags);
1152 1153
}

1154 1155 1156 1157 1158 1159 1160 1161 1162
/**
 * splice_direct_to_actor - splices data directly between two non-pipes
 * @in:		file to splice from
 * @sd:		actor information on where to splice to
 * @actor:	handles the data splicing
 *
 * Description:
 *    This is a special case helper to splice directly between two
 *    points, without requiring an explicit pipe. Internally an allocated
R
Randy Dunlap 已提交
1163
 *    pipe is cached in the process, and reused during the lifetime of
1164 1165
 *    that process.
 *
J
Jens Axboe 已提交
1166 1167 1168
 */
ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
			       splice_direct_actor *actor)
1169 1170 1171 1172
{
	struct pipe_inode_info *pipe;
	long ret, bytes;
	umode_t i_mode;
J
Jens Axboe 已提交
1173
	size_t len;
1174
	int i, flags, more;
1175 1176 1177 1178 1179 1180

	/*
	 * We require the input being a regular file, as we don't want to
	 * randomly drop data for eg socket -> socket splicing. Use the
	 * piped splicing for that!
	 */
A
Al Viro 已提交
1181
	i_mode = file_inode(in)->i_mode;
1182 1183 1184 1185 1186 1187 1188 1189
	if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode)))
		return -EINVAL;

	/*
	 * neither in nor out is a pipe, setup an internal pipe attached to
	 * 'out' and transfer the wanted data from 'in' to 'out' through that
	 */
	pipe = current->splice_pipe;
1190
	if (unlikely(!pipe)) {
A
Al Viro 已提交
1191
		pipe = alloc_pipe_info();
1192 1193 1194 1195 1196
		if (!pipe)
			return -ENOMEM;

		/*
		 * We don't have an immediate reader, but we'll read the stuff
1197
		 * out of the pipe right after the splice_to_pipe(). So set
1198 1199 1200 1201 1202 1203 1204 1205
		 * PIPE_READERS appropriately.
		 */
		pipe->readers = 1;

		current->splice_pipe = pipe;
	}

	/*
I
Ingo Molnar 已提交
1206
	 * Do the splice.
1207 1208 1209
	 */
	ret = 0;
	bytes = 0;
J
Jens Axboe 已提交
1210 1211 1212 1213 1214 1215 1216
	len = sd->total_len;
	flags = sd->flags;

	/*
	 * Don't block on output, we have to drain the direct pipe.
	 */
	sd->flags &= ~SPLICE_F_NONBLOCK;
1217
	more = sd->flags & SPLICE_F_MORE;
1218 1219

	while (len) {
1220
		size_t read_len;
1221
		loff_t pos = sd->pos, prev_pos = pos;
1222

1223
		ret = do_splice_to(in, &pos, pipe, len, flags);
1224
		if (unlikely(ret <= 0))
1225 1226 1227
			goto out_release;

		read_len = ret;
J
Jens Axboe 已提交
1228
		sd->total_len = read_len;
1229

1230 1231 1232 1233 1234 1235 1236 1237 1238
		/*
		 * If more data is pending, set SPLICE_F_MORE
		 * If this is the last data and SPLICE_F_MORE was not set
		 * initially, clears it.
		 */
		if (read_len < len)
			sd->flags |= SPLICE_F_MORE;
		else if (!more)
			sd->flags &= ~SPLICE_F_MORE;
1239 1240 1241 1242 1243
		/*
		 * NOTE: nonblocking mode only applies to the input. We
		 * must not do the output in nonblocking mode as then we
		 * could get stuck data in the internal pipe:
		 */
J
Jens Axboe 已提交
1244
		ret = actor(pipe, sd);
1245 1246
		if (unlikely(ret <= 0)) {
			sd->pos = prev_pos;
1247
			goto out_release;
1248
		}
1249 1250 1251

		bytes += ret;
		len -= ret;
1252
		sd->pos = pos;
1253

1254 1255
		if (ret < read_len) {
			sd->pos = prev_pos + ret;
1256
			goto out_release;
1257
		}
1258 1259
	}

1260
done:
1261
	pipe->nrbufs = pipe->curbuf = 0;
1262
	file_accessed(in);
1263 1264 1265 1266 1267 1268 1269
	return bytes;

out_release:
	/*
	 * If we did an incomplete transfer we must release
	 * the pipe buffers in question:
	 */
1270
	for (i = 0; i < pipe->buffers; i++) {
1271 1272 1273 1274 1275 1276 1277 1278
		struct pipe_buffer *buf = pipe->bufs + i;

		if (buf->ops) {
			buf->ops->release(pipe, buf);
			buf->ops = NULL;
		}
	}

1279 1280
	if (!bytes)
		bytes = ret;
J
Jens Axboe 已提交
1281

1282
	goto done;
J
Jens Axboe 已提交
1283 1284 1285 1286 1287 1288
}
EXPORT_SYMBOL(splice_direct_to_actor);

static int direct_splice_actor(struct pipe_inode_info *pipe,
			       struct splice_desc *sd)
{
1289
	struct file *file = sd->u.file;
J
Jens Axboe 已提交
1290

1291
	return do_splice_from(pipe, file, sd->opos, sd->total_len,
1292
			      sd->flags);
J
Jens Axboe 已提交
1293 1294
}

1295 1296 1297 1298 1299
/**
 * do_splice_direct - splices data directly between two files
 * @in:		file to splice from
 * @ppos:	input file offset
 * @out:	file to splice to
1300
 * @opos:	output file offset
1301 1302 1303 1304 1305 1306 1307 1308 1309 1310
 * @len:	number of bytes to splice
 * @flags:	splice modifier flags
 *
 * Description:
 *    For use by do_sendfile(). splice can easily emulate sendfile, but
 *    doing it in the application would incur an extra system call
 *    (splice in + splice out, as compared to just sendfile()). So this helper
 *    can splice directly through a process-private pipe.
 *
 */
J
Jens Axboe 已提交
1311
long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
1312
		      loff_t *opos, size_t len, unsigned int flags)
J
Jens Axboe 已提交
1313 1314 1315 1316 1317 1318
{
	struct splice_desc sd = {
		.len		= len,
		.total_len	= len,
		.flags		= flags,
		.pos		= *ppos,
1319
		.u.file		= out,
1320
		.opos		= opos,
J
Jens Axboe 已提交
1321
	};
1322
	long ret;
J
Jens Axboe 已提交
1323

1324 1325 1326 1327 1328 1329 1330 1331 1332 1333
	if (unlikely(!(out->f_mode & FMODE_WRITE)))
		return -EBADF;

	if (unlikely(out->f_flags & O_APPEND))
		return -EINVAL;

	ret = rw_verify_area(WRITE, out, opos, len);
	if (unlikely(ret < 0))
		return ret;

J
Jens Axboe 已提交
1334
	ret = splice_direct_to_actor(in, &sd, direct_splice_actor);
1335
	if (ret > 0)
1336
		*ppos = sd.pos;
1337

J
Jens Axboe 已提交
1338
	return ret;
1339
}
1340
EXPORT_SYMBOL(do_splice_direct);
1341

1342 1343 1344
static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
			       struct pipe_inode_info *opipe,
			       size_t len, unsigned int flags);
1345

1346 1347 1348
/*
 * Determine where to splice to/from.
 */
1349 1350 1351
static long do_splice(struct file *in, loff_t __user *off_in,
		      struct file *out, loff_t __user *off_out,
		      size_t len, unsigned int flags)
1352
{
1353 1354
	struct pipe_inode_info *ipipe;
	struct pipe_inode_info *opipe;
1355
	loff_t offset;
J
Jens Axboe 已提交
1356
	long ret;
1357

1358 1359
	ipipe = get_pipe_info(in);
	opipe = get_pipe_info(out);
1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378

	if (ipipe && opipe) {
		if (off_in || off_out)
			return -ESPIPE;

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

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

		/* Splicing to self would be fun, but... */
		if (ipipe == opipe)
			return -EINVAL;

		return splice_pipe_to_pipe(ipipe, opipe, len, flags);
	}

	if (ipipe) {
1379 1380
		if (off_in)
			return -ESPIPE;
1381
		if (off_out) {
1382
			if (!(out->f_mode & FMODE_PWRITE))
1383
				return -EINVAL;
1384
			if (copy_from_user(&offset, off_out, sizeof(loff_t)))
1385
				return -EFAULT;
1386 1387 1388
		} else {
			offset = out->f_pos;
		}
1389

1390 1391 1392 1393 1394 1395 1396 1397 1398 1399
		if (unlikely(!(out->f_mode & FMODE_WRITE)))
			return -EBADF;

		if (unlikely(out->f_flags & O_APPEND))
			return -EINVAL;

		ret = rw_verify_area(WRITE, out, &offset, len);
		if (unlikely(ret < 0))
			return ret;

1400
		file_start_write(out);
1401
		ret = do_splice_from(ipipe, out, &offset, len, flags);
1402
		file_end_write(out);
J
Jens Axboe 已提交
1403

1404 1405 1406
		if (!off_out)
			out->f_pos = offset;
		else if (copy_to_user(off_out, &offset, sizeof(loff_t)))
J
Jens Axboe 已提交
1407 1408 1409
			ret = -EFAULT;

		return ret;
1410
	}
1411

1412
	if (opipe) {
1413 1414
		if (off_out)
			return -ESPIPE;
1415
		if (off_in) {
1416
			if (!(in->f_mode & FMODE_PREAD))
1417
				return -EINVAL;
1418
			if (copy_from_user(&offset, off_in, sizeof(loff_t)))
1419
				return -EFAULT;
1420 1421 1422
		} else {
			offset = in->f_pos;
		}
1423

1424
		ret = do_splice_to(in, &offset, opipe, len, flags);
J
Jens Axboe 已提交
1425

1426 1427 1428
		if (!off_in)
			in->f_pos = offset;
		else if (copy_to_user(off_in, &offset, sizeof(loff_t)))
J
Jens Axboe 已提交
1429 1430 1431
			ret = -EFAULT;

		return ret;
1432
	}
1433 1434 1435 1436

	return -EINVAL;
}

1437 1438 1439 1440 1441 1442 1443 1444 1445
/*
 * Map an iov into an array of pages and offset/length tupples. With the
 * partial_page structure, we can map several non-contiguous ranges into
 * our ones pages[] map instead of splitting that operation into pieces.
 * Could easily be exported as a generic helper for other users, in which
 * case one would probably want to add a 'max_nr_pages' parameter as well.
 */
static int get_iovec_page_array(const struct iovec __user *iov,
				unsigned int nr_vecs, struct page **pages,
1446
				struct partial_page *partial, bool aligned,
1447
				unsigned int pipe_buffers)
1448 1449 1450 1451 1452
{
	int buffers = 0, error = 0;

	while (nr_vecs) {
		unsigned long off, npages;
1453
		struct iovec entry;
1454 1455 1456 1457
		void __user *base;
		size_t len;
		int i;

1458
		error = -EFAULT;
N
Nick Piggin 已提交
1459
		if (copy_from_user(&entry, iov, sizeof(entry)))
1460 1461
			break;

1462 1463 1464
		base = entry.iov_base;
		len = entry.iov_len;

1465 1466 1467
		/*
		 * Sanity check this iovec. 0 read succeeds.
		 */
1468
		error = 0;
1469 1470 1471
		if (unlikely(!len))
			break;
		error = -EFAULT;
1472
		if (!access_ok(VERIFY_READ, base, len))
1473 1474 1475 1476 1477 1478 1479
			break;

		/*
		 * Get this base offset and number of pages, then map
		 * in the user pages.
		 */
		off = (unsigned long) base & ~PAGE_MASK;
1480 1481 1482 1483 1484 1485 1486 1487 1488

		/*
		 * If asked for alignment, the offset must be zero and the
		 * length a multiple of the PAGE_SIZE.
		 */
		error = -EINVAL;
		if (aligned && (off || len & ~PAGE_MASK))
			break;

1489
		npages = (off + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1490 1491
		if (npages > pipe_buffers - buffers)
			npages = pipe_buffers - buffers;
1492

N
Nick Piggin 已提交
1493 1494
		error = get_user_pages_fast((unsigned long)base, npages,
					0, &pages[buffers]);
1495 1496 1497 1498 1499 1500 1501 1502

		if (unlikely(error <= 0))
			break;

		/*
		 * Fill this contiguous range into the partial page map.
		 */
		for (i = 0; i < error; i++) {
1503
			const int plen = min_t(size_t, len, PAGE_SIZE - off);
1504 1505 1506 1507 1508 1509 1510 1511 1512 1513 1514 1515 1516 1517 1518 1519 1520 1521 1522 1523 1524 1525

			partial[buffers].offset = off;
			partial[buffers].len = plen;

			off = 0;
			len -= plen;
			buffers++;
		}

		/*
		 * We didn't complete this iov, stop here since it probably
		 * means we have to move some of this into a pipe to
		 * be able to continue.
		 */
		if (len)
			break;

		/*
		 * Don't continue if we mapped fewer pages than we asked for,
		 * or if we mapped the max number of pages that we have
		 * room for.
		 */
1526
		if (error < npages || buffers == pipe_buffers)
1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 1538
			break;

		nr_vecs--;
		iov++;
	}

	if (buffers)
		return buffers;

	return error;
}

1539 1540 1541
static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
			struct splice_desc *sd)
{
1542 1543
	int n = copy_page_to_iter(buf->page, buf->offset, sd->len, sd->u.data);
	return n == sd->len ? n : -EFAULT;
1544 1545 1546 1547 1548 1549
}

/*
 * For lack of a better implementation, implement vmsplice() to userspace
 * as a simple copy of the pipes pages to the user iov.
 */
1550
static long vmsplice_to_user(struct file *file, const struct iovec __user *uiov,
1551 1552 1553 1554 1555
			     unsigned long nr_segs, unsigned int flags)
{
	struct pipe_inode_info *pipe;
	struct splice_desc sd;
	long ret;
1556 1557 1558
	struct iovec iovstack[UIO_FASTIOV];
	struct iovec *iov = iovstack;
	struct iov_iter iter;
1559

1560
	pipe = get_pipe_info(file);
1561 1562 1563
	if (!pipe)
		return -EBADF;

1564 1565 1566 1567
	ret = import_iovec(READ, uiov, nr_segs,
			   ARRAY_SIZE(iovstack), &iov, &iter);
	if (ret < 0)
		return ret;
1568

1569
	sd.total_len = iov_iter_count(&iter);
1570 1571 1572 1573
	sd.len = 0;
	sd.flags = flags;
	sd.u.data = &iter;
	sd.pos = 0;
1574

1575 1576 1577 1578 1579
	if (sd.total_len) {
		pipe_lock(pipe);
		ret = __splice_from_pipe(pipe, &sd, pipe_to_user);
		pipe_unlock(pipe);
	}
1580

1581
	kfree(iov);
1582 1583 1584
	return ret;
}

1585 1586 1587 1588 1589
/*
 * vmsplice splices a user address range into a pipe. It can be thought of
 * as splice-from-memory, where the regular splice is splice-from-file (or
 * to file). In both cases the output is a pipe, naturally.
 */
1590 1591
static long vmsplice_to_pipe(struct file *file, const struct iovec __user *iov,
			     unsigned long nr_segs, unsigned int flags)
1592
{
1593
	struct pipe_inode_info *pipe;
1594 1595
	struct page *pages[PIPE_DEF_BUFFERS];
	struct partial_page partial[PIPE_DEF_BUFFERS];
1596 1597 1598
	struct splice_pipe_desc spd = {
		.pages = pages,
		.partial = partial,
1599
		.nr_pages_max = PIPE_DEF_BUFFERS,
1600 1601
		.flags = flags,
		.ops = &user_page_pipe_buf_ops,
1602
		.spd_release = spd_release_page,
1603
	};
1604
	long ret;
1605

1606
	pipe = get_pipe_info(file);
1607
	if (!pipe)
1608 1609
		return -EBADF;

1610 1611 1612 1613
	if (splice_grow_spd(pipe, &spd))
		return -ENOMEM;

	spd.nr_pages = get_iovec_page_array(iov, nr_segs, spd.pages,
1614
					    spd.partial, false,
1615
					    spd.nr_pages_max);
1616
	if (spd.nr_pages <= 0)
1617 1618 1619
		ret = spd.nr_pages;
	else
		ret = splice_to_pipe(pipe, &spd);
1620

1621
	splice_shrink_spd(&spd);
1622
	return ret;
1623 1624
}

1625 1626 1627 1628 1629 1630 1631 1632 1633 1634 1635 1636 1637 1638 1639 1640
/*
 * Note that vmsplice only really supports true splicing _from_ user memory
 * to a pipe, not the other way around. Splicing from user memory is a simple
 * operation that can be supported without any funky alignment restrictions
 * or nasty vm tricks. We simply map in the user memory and fill them into
 * a pipe. The reverse isn't quite as easy, though. There are two possible
 * solutions for that:
 *
 *	- memcpy() the data internally, at which point we might as well just
 *	  do a regular read() on the buffer anyway.
 *	- Lots of nasty vm tricks, that are neither fast nor flexible (it
 *	  has restriction limitations on both ends of the pipe).
 *
 * Currently we punt and implement it as a normal copy, see pipe_to_user().
 *
 */
1641 1642
SYSCALL_DEFINE4(vmsplice, int, fd, const struct iovec __user *, iov,
		unsigned long, nr_segs, unsigned int, flags)
1643
{
1644
	struct fd f;
1645 1646
	long error;

1647 1648 1649 1650 1651
	if (unlikely(nr_segs > UIO_MAXIOV))
		return -EINVAL;
	else if (unlikely(!nr_segs))
		return 0;

1652
	error = -EBADF;
1653 1654 1655 1656 1657 1658 1659 1660
	f = fdget(fd);
	if (f.file) {
		if (f.file->f_mode & FMODE_WRITE)
			error = vmsplice_to_pipe(f.file, iov, nr_segs, flags);
		else if (f.file->f_mode & FMODE_READ)
			error = vmsplice_to_user(f.file, iov, nr_segs, flags);

		fdput(f);
1661 1662 1663 1664 1665
	}

	return error;
}

1666 1667 1668 1669 1670 1671 1672 1673 1674 1675 1676 1677 1678 1679 1680 1681 1682 1683 1684 1685 1686
#ifdef CONFIG_COMPAT
COMPAT_SYSCALL_DEFINE4(vmsplice, int, fd, const struct compat_iovec __user *, iov32,
		    unsigned int, nr_segs, unsigned int, flags)
{
	unsigned i;
	struct iovec __user *iov;
	if (nr_segs > UIO_MAXIOV)
		return -EINVAL;
	iov = compat_alloc_user_space(nr_segs * sizeof(struct iovec));
	for (i = 0; i < nr_segs; i++) {
		struct compat_iovec v;
		if (get_user(v.iov_base, &iov32[i].iov_base) ||
		    get_user(v.iov_len, &iov32[i].iov_len) ||
		    put_user(compat_ptr(v.iov_base), &iov[i].iov_base) ||
		    put_user(v.iov_len, &iov[i].iov_len))
			return -EFAULT;
	}
	return sys_vmsplice(fd, iov, nr_segs, flags);
}
#endif

1687 1688 1689
SYSCALL_DEFINE6(splice, int, fd_in, loff_t __user *, off_in,
		int, fd_out, loff_t __user *, off_out,
		size_t, len, unsigned int, flags)
1690
{
1691
	struct fd in, out;
1692 1693 1694 1695 1696 1697
	long error;

	if (unlikely(!len))
		return 0;

	error = -EBADF;
1698 1699 1700 1701 1702 1703 1704 1705
	in = fdget(fd_in);
	if (in.file) {
		if (in.file->f_mode & FMODE_READ) {
			out = fdget(fd_out);
			if (out.file) {
				if (out.file->f_mode & FMODE_WRITE)
					error = do_splice(in.file, off_in,
							  out.file, off_out,
1706
							  len, flags);
1707
				fdput(out);
1708 1709
			}
		}
1710
		fdput(in);
1711 1712 1713
	}
	return error;
}
1714

1715 1716 1717 1718
/*
 * Make sure there's data to read. Wait for input if we can, otherwise
 * return an appropriate error.
 */
1719
static int ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1720 1721 1722 1723 1724 1725 1726 1727 1728 1729 1730
{
	int ret;

	/*
	 * Check ->nrbufs without the inode lock first. This function
	 * is speculative anyways, so missing one is ok.
	 */
	if (pipe->nrbufs)
		return 0;

	ret = 0;
1731
	pipe_lock(pipe);
1732 1733 1734 1735 1736 1737 1738 1739 1740 1741 1742 1743 1744 1745 1746 1747 1748

	while (!pipe->nrbufs) {
		if (signal_pending(current)) {
			ret = -ERESTARTSYS;
			break;
		}
		if (!pipe->writers)
			break;
		if (!pipe->waiting_writers) {
			if (flags & SPLICE_F_NONBLOCK) {
				ret = -EAGAIN;
				break;
			}
		}
		pipe_wait(pipe);
	}

1749
	pipe_unlock(pipe);
1750 1751 1752 1753 1754 1755 1756
	return ret;
}

/*
 * Make sure there's writeable room. Wait for room if we can, otherwise
 * return an appropriate error.
 */
1757
static int opipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1758 1759 1760 1761 1762 1763 1764
{
	int ret;

	/*
	 * Check ->nrbufs without the inode lock first. This function
	 * is speculative anyways, so missing one is ok.
	 */
1765
	if (pipe->nrbufs < pipe->buffers)
1766 1767 1768
		return 0;

	ret = 0;
1769
	pipe_lock(pipe);
1770

1771
	while (pipe->nrbufs >= pipe->buffers) {
1772 1773 1774 1775 1776 1777 1778 1779 1780 1781 1782 1783 1784 1785 1786 1787 1788 1789
		if (!pipe->readers) {
			send_sig(SIGPIPE, current, 0);
			ret = -EPIPE;
			break;
		}
		if (flags & SPLICE_F_NONBLOCK) {
			ret = -EAGAIN;
			break;
		}
		if (signal_pending(current)) {
			ret = -ERESTARTSYS;
			break;
		}
		pipe->waiting_writers++;
		pipe_wait(pipe);
		pipe->waiting_writers--;
	}

1790
	pipe_unlock(pipe);
1791 1792 1793
	return ret;
}

1794 1795 1796 1797 1798 1799 1800 1801 1802 1803 1804 1805 1806 1807 1808 1809 1810 1811 1812 1813 1814 1815 1816 1817 1818 1819 1820 1821 1822 1823 1824 1825 1826 1827 1828 1829 1830 1831 1832 1833 1834 1835 1836
/*
 * Splice contents of ipipe to opipe.
 */
static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
			       struct pipe_inode_info *opipe,
			       size_t len, unsigned int flags)
{
	struct pipe_buffer *ibuf, *obuf;
	int ret = 0, nbuf;
	bool input_wakeup = false;


retry:
	ret = ipipe_prep(ipipe, flags);
	if (ret)
		return ret;

	ret = opipe_prep(opipe, flags);
	if (ret)
		return ret;

	/*
	 * Potential ABBA deadlock, work around it by ordering lock
	 * grabbing by pipe info address. Otherwise two different processes
	 * could deadlock (one doing tee from A -> B, the other from B -> A).
	 */
	pipe_double_lock(ipipe, opipe);

	do {
		if (!opipe->readers) {
			send_sig(SIGPIPE, current, 0);
			if (!ret)
				ret = -EPIPE;
			break;
		}

		if (!ipipe->nrbufs && !ipipe->writers)
			break;

		/*
		 * Cannot make any progress, because either the input
		 * pipe is empty or the output pipe is full.
		 */
1837
		if (!ipipe->nrbufs || opipe->nrbufs >= opipe->buffers) {
1838 1839 1840 1841 1842 1843 1844 1845 1846 1847 1848 1849 1850 1851 1852 1853 1854 1855 1856 1857
			/* Already processed some buffers, break */
			if (ret)
				break;

			if (flags & SPLICE_F_NONBLOCK) {
				ret = -EAGAIN;
				break;
			}

			/*
			 * We raced with another reader/writer and haven't
			 * managed to process any buffers.  A zero return
			 * value means EOF, so retry instead.
			 */
			pipe_unlock(ipipe);
			pipe_unlock(opipe);
			goto retry;
		}

		ibuf = ipipe->bufs + ipipe->curbuf;
1858
		nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1);
1859 1860 1861 1862 1863 1864 1865 1866 1867
		obuf = opipe->bufs + nbuf;

		if (len >= ibuf->len) {
			/*
			 * Simply move the whole buffer from ipipe to opipe
			 */
			*obuf = *ibuf;
			ibuf->ops = NULL;
			opipe->nrbufs++;
1868
			ipipe->curbuf = (ipipe->curbuf + 1) & (ipipe->buffers - 1);
1869 1870 1871 1872 1873 1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 1884 1885 1886 1887 1888 1889 1890 1891 1892 1893 1894 1895 1896 1897 1898 1899
			ipipe->nrbufs--;
			input_wakeup = true;
		} else {
			/*
			 * Get a reference to this pipe buffer,
			 * so we can copy the contents over.
			 */
			ibuf->ops->get(ipipe, ibuf);
			*obuf = *ibuf;

			/*
			 * Don't inherit the gift flag, we need to
			 * prevent multiple steals of this page.
			 */
			obuf->flags &= ~PIPE_BUF_FLAG_GIFT;

			obuf->len = len;
			opipe->nrbufs++;
			ibuf->offset += obuf->len;
			ibuf->len -= obuf->len;
		}
		ret += obuf->len;
		len -= obuf->len;
	} while (len);

	pipe_unlock(ipipe);
	pipe_unlock(opipe);

	/*
	 * If we put data in the output pipe, wakeup any potential readers.
	 */
N
Namhyung Kim 已提交
1900 1901 1902
	if (ret > 0)
		wakeup_pipe_readers(opipe);

1903 1904 1905 1906 1907 1908
	if (input_wakeup)
		wakeup_pipe_writers(ipipe);

	return ret;
}

1909 1910 1911 1912 1913 1914 1915 1916
/*
 * Link contents of ipipe to opipe.
 */
static int link_pipe(struct pipe_inode_info *ipipe,
		     struct pipe_inode_info *opipe,
		     size_t len, unsigned int flags)
{
	struct pipe_buffer *ibuf, *obuf;
1917
	int ret = 0, i = 0, nbuf;
1918 1919 1920

	/*
	 * Potential ABBA deadlock, work around it by ordering lock
1921
	 * grabbing by pipe info address. Otherwise two different processes
1922 1923
	 * could deadlock (one doing tee from A -> B, the other from B -> A).
	 */
1924
	pipe_double_lock(ipipe, opipe);
1925

1926
	do {
1927 1928 1929 1930 1931 1932 1933
		if (!opipe->readers) {
			send_sig(SIGPIPE, current, 0);
			if (!ret)
				ret = -EPIPE;
			break;
		}

1934 1935 1936 1937
		/*
		 * If we have iterated all input buffers or ran out of
		 * output room, break.
		 */
1938
		if (i >= ipipe->nrbufs || opipe->nrbufs >= opipe->buffers)
1939
			break;
1940

1941 1942
		ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (ipipe->buffers-1));
		nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1);
1943 1944

		/*
1945 1946
		 * Get a reference to this pipe buffer,
		 * so we can copy the contents over.
1947
		 */
1948 1949 1950 1951 1952
		ibuf->ops->get(ipipe, ibuf);

		obuf = opipe->bufs + nbuf;
		*obuf = *ibuf;

1953
		/*
1954 1955
		 * Don't inherit the gift flag, we need to
		 * prevent multiple steals of this page.
1956
		 */
1957
		obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1958

1959 1960
		if (obuf->len > len)
			obuf->len = len;
1961

1962 1963 1964 1965 1966
		opipe->nrbufs++;
		ret += obuf->len;
		len -= obuf->len;
		i++;
	} while (len);
1967

1968 1969 1970 1971 1972 1973 1974
	/*
	 * return EAGAIN if we have the potential of some data in the
	 * future, otherwise just return 0
	 */
	if (!ret && ipipe->waiting_writers && (flags & SPLICE_F_NONBLOCK))
		ret = -EAGAIN;

1975 1976
	pipe_unlock(ipipe);
	pipe_unlock(opipe);
1977

1978 1979 1980
	/*
	 * If we put data in the output pipe, wakeup any potential readers.
	 */
N
Namhyung Kim 已提交
1981 1982
	if (ret > 0)
		wakeup_pipe_readers(opipe);
1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995

	return ret;
}

/*
 * This is a tee(1) implementation that works on pipes. It doesn't copy
 * any data, it simply references the 'in' pages on the 'out' pipe.
 * The 'flags' used are the SPLICE_F_* variants, currently the only
 * applicable one is SPLICE_F_NONBLOCK.
 */
static long do_tee(struct file *in, struct file *out, size_t len,
		   unsigned int flags)
{
1996 1997
	struct pipe_inode_info *ipipe = get_pipe_info(in);
	struct pipe_inode_info *opipe = get_pipe_info(out);
1998
	int ret = -EINVAL;
1999 2000

	/*
2001 2002
	 * Duplicate the contents of ipipe to opipe without actually
	 * copying the data.
2003
	 */
2004 2005 2006 2007 2008
	if (ipipe && opipe && ipipe != opipe) {
		/*
		 * Keep going, unless we encounter an error. The ipipe/opipe
		 * ordering doesn't really matter.
		 */
2009
		ret = ipipe_prep(ipipe, flags);
2010
		if (!ret) {
2011
			ret = opipe_prep(opipe, flags);
2012
			if (!ret)
2013 2014 2015
				ret = link_pipe(ipipe, opipe, len, flags);
		}
	}
2016

2017
	return ret;
2018 2019
}

2020
SYSCALL_DEFINE4(tee, int, fdin, int, fdout, size_t, len, unsigned int, flags)
2021
{
2022 2023
	struct fd in;
	int error;
2024 2025 2026 2027 2028

	if (unlikely(!len))
		return 0;

	error = -EBADF;
2029 2030 2031 2032 2033 2034 2035 2036 2037
	in = fdget(fdin);
	if (in.file) {
		if (in.file->f_mode & FMODE_READ) {
			struct fd out = fdget(fdout);
			if (out.file) {
				if (out.file->f_mode & FMODE_WRITE)
					error = do_tee(in.file, out.file,
							len, flags);
				fdput(out);
2038 2039
			}
		}
2040
 		fdput(in);
2041 2042 2043 2044
 	}

	return error;
}