splice.c 46.4 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>
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#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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		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)
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{
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	unsigned int spd_pages = spd->nr_pages;
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	int ret, do_wakeup, page_nr;
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	ret = 0;
	do_wakeup = 0;
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	page_nr = 0;
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192
	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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221
			if (!--spd->nr_pages)
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				break;
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			if (pipe->nrbufs < pipe->buffers)
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				continue;

			break;
		}

229
		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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	if (do_wakeup)
		wakeup_pipe_readers(pipe);
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259
	while (page_nr < spd_pages)
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		spd->spd_release(spd, page_nr++);
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	return ret;
}
264
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)
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{
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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)
295
{
296
	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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Fengguang Wu 已提交
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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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	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,
341
	 * readahead/allocate the rest and fill in the holes.
342
	 */
343
	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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347
	error = 0;
348
	while (spd.nr_pages < nr_pages) {
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		/*
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		 * Page could be there, find_get_pages_contig() breaks on
		 * the first hole.
352
		 */
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		page = find_get_page(mapping, index);
		if (!page) {
			/*
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			 * 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,
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				   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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		}

377
		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);
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		page = spd.pages[page_nr];
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400
		if (PageReadahead(page))
401
			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)) {
408
			lock_page(page);
409 410

			/*
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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.
415 416 417
			 */
			if (!page->mapping) {
				unlock_page(page);
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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);
440
			if (unlikely(error)) {
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				/*
				 * We really should re-lookup the page here,
				 * but it complicates things a lot. Instead
				 * lets just do what we already stored, and
				 * we'll get it the next time we are called.
				 */
447
				if (error == AOP_TRUNCATED_PAGE)
448 449
					error = 0;

450 451
				break;
			}
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		}
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;
468 469

			/*
470
			 * max good bytes in this page
471
			 */
472 473
			plen = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
			if (plen <= loff)
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				break;

			/*
477
			 * force quit after adding this page
478
			 */
479 480
			this_len = min(this_len, plen - loff);
			len = this_len;
481
		}
482

483 484
		spd.partial[page_nr].offset = loff;
		spd.partial[page_nr].len = this_len;
485
		len -= this_len;
486
		loff = 0;
487 488
		spd.nr_pages++;
		index++;
489 490
	}

491
	/*
492
	 * Release any pages at the end, if we quit early. 'page_nr' is how far
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	 * we got, 'nr_pages' is how many pages are in the map.
	 */
	while (page_nr < nr_pages)
496
		page_cache_release(spd.pages[page_nr++]);
497
	in->f_ra.prev_pos = (loff_t)index << PAGE_CACHE_SHIFT;
498

499
	if (spd.nr_pages)
500
		error = splice_to_pipe(pipe, &spd);
501

502
	splice_shrink_spd(&spd);
503
	return error;
504 505
}

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/**
 * generic_file_splice_read - splice data from file to a pipe
 * @in:		file to splice from
509
 * @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.
 *
519
 */
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ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
				 struct pipe_inode_info *pipe, size_t len,
				 unsigned int flags)
523
{
524
	loff_t isize, left;
525
	int ret;
526

527 528 529
	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;
537

538
	ret = __generic_file_splice_read(in, ppos, pipe, len, flags);
539
	if (ret > 0) {
540
		*ppos += ret;
541 542
		file_accessed(in);
	}
543 544 545

	return ret;
}
546 547
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;
}

588
ssize_t kernel_write(struct file *file, const char *buf, size_t count,
589
			    loff_t pos)
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{
	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() */
597
	res = vfs_write(file, (__force const char __user *)buf, count, &pos);
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	set_fs(old_fs);

	return res;
}
602
EXPORT_SYMBOL(kernel_write);
603

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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,
621
		.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;

641
	for (i = 0; i < nr_pages && i < spd.nr_pages_max && len; i++) {
642 643
		struct page *page;

644
		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);
650
		vec[i].iov_base = (void __user *) page_address(page);
651
		vec[i].iov_len = this_len;
652
		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;
661
		goto err;
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Andrew Morton 已提交
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	}
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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);
671 672
		spd.partial[i].offset = 0;
		spd.partial[i].len = this_len;
673
		if (!this_len) {
674 675
			__free_page(spd.pages[i]);
			spd.pages[i] = NULL;
676 677 678 679 680 681 682 683 684 685
			nr_freed++;
		}
		res -= this_len;
	}
	spd.nr_pages -= nr_freed;

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

686 687 688
shrink_ret:
	if (vec != __vec)
		kfree(vec);
689
	splice_shrink_spd(&spd);
690 691 692
	return res;

err:
693
	for (i = 0; i < spd.nr_pages; i++)
694
		__free_page(spd.pages[i]);
695

696 697
	res = error;
	goto shrink_ret;
698 699 700
}
EXPORT_SYMBOL(default_file_splice_read);

701
/*
702
 * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
J
Jens Axboe 已提交
703
 * using sendpage(). Return the number of bytes sent.
704
 */
705
static int pipe_to_sendpage(struct pipe_inode_info *pipe,
706 707
			    struct pipe_buffer *buf, struct splice_desc *sd)
{
708
	struct file *file = sd->u.file;
709
	loff_t pos = sd->pos;
710
	int more;
711

A
Al Viro 已提交
712
	if (!likely(file->f_op->sendpage))
713 714
		return -EINVAL;

715
	more = (sd->flags & SPLICE_F_MORE) ? MSG_MORE : 0;
716 717

	if (sd->len < sd->total_len && pipe->nrbufs > 1)
718
		more |= MSG_SENDPAGE_NOTLAST;
719

720 721
	return file->f_op->sendpage(file, buf->page, buf->offset,
				    sd->len, &pos, more);
722 723
}

724 725 726 727 728 729 730 731
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);
}

732
/**
733
 * splice_from_pipe_feed - feed available data from a pipe to a file
734 735 736 737 738
 * @pipe:	pipe to splice from
 * @sd:		information to @actor
 * @actor:	handler that splices the data
 *
 * Description:
739 740 741 742 743 744 745
 *    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.
746
 *
747 748 749 750
 *    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.
751
 */
A
Al Viro 已提交
752
static int splice_from_pipe_feed(struct pipe_inode_info *pipe, struct splice_desc *sd,
753
			  splice_actor *actor)
754
{
755
	int ret;
756

757 758 759
	while (pipe->nrbufs) {
		struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
		const struct pipe_buf_operations *ops = buf->ops;
760

761 762 763
		sd->len = buf->len;
		if (sd->len > sd->total_len)
			sd->len = sd->total_len;
764

765 766
		ret = buf->ops->confirm(pipe, buf);
		if (unlikely(ret)) {
767 768 769 770
			if (ret == -ENODATA)
				ret = 0;
			return ret;
		}
771 772 773 774 775

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

776 777 778 779 780 781 782 783 784 785 786
		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);
787
			pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1);
788
			pipe->nrbufs--;
A
Al Viro 已提交
789
			if (pipe->files)
790 791
				sd->need_wakeup = true;
		}
792

793 794 795
		if (!sd->total_len)
			return 0;
	}
796

797 798
	return 1;
}
799

800 801 802 803 804 805 806 807 808 809
/**
 * 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
810
static int splice_from_pipe_next(struct pipe_inode_info *pipe, struct splice_desc *sd)
811
{
812 813 814 815 816 817 818
	/*
	 * Check for signal early to make process killable when there are
	 * always buffers available
	 */
	if (signal_pending(current))
		return -ERESTARTSYS;

819 820 821
	while (!pipe->nrbufs) {
		if (!pipe->writers)
			return 0;
J
Jens Axboe 已提交
822

823 824
		if (!pipe->waiting_writers && sd->num_spliced)
			return 0;
I
Ingo Molnar 已提交
825

826 827
		if (sd->flags & SPLICE_F_NONBLOCK)
			return -EAGAIN;
828

829 830
		if (signal_pending(current))
			return -ERESTARTSYS;
831

832 833 834
		if (sd->need_wakeup) {
			wakeup_pipe_writers(pipe);
			sd->need_wakeup = false;
835 836
		}

837 838
		pipe_wait(pipe);
	}
839

840 841
	return 1;
}
842

843 844
/**
 * splice_from_pipe_begin - start splicing from pipe
845
 * @sd:		information about the splice operation
846 847 848 849 850 851
 *
 * 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
852
static void splice_from_pipe_begin(struct splice_desc *sd)
853 854 855 856
{
	sd->num_spliced = 0;
	sd->need_wakeup = false;
}
857

858 859 860 861 862 863 864 865 866 867
/**
 * 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
868
static void splice_from_pipe_end(struct pipe_inode_info *pipe, struct splice_desc *sd)
869 870 871 872
{
	if (sd->need_wakeup)
		wakeup_pipe_writers(pipe);
}
873

874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890
/**
 * __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;
891

892 893
	splice_from_pipe_begin(sd);
	do {
J
Jan Kara 已提交
894
		cond_resched();
895 896 897 898 899 900 901
		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;
902
}
M
Mark Fasheh 已提交
903
EXPORT_SYMBOL(__splice_from_pipe);
904

905 906 907 908 909 910 911 912 913 914
/**
 * 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:
915
 *    See __splice_from_pipe. This function locks the pipe inode,
916 917 918
 *    otherwise it's identical to __splice_from_pipe().
 *
 */
919 920 921 922 923
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
924 925 926 927
	struct splice_desc sd = {
		.total_len = len,
		.flags = flags,
		.pos = *ppos,
928
		.u.file = out,
J
Jens Axboe 已提交
929
	};
930

931
	pipe_lock(pipe);
J
Jens Axboe 已提交
932
	ret = __splice_from_pipe(pipe, &sd, actor);
933
	pipe_unlock(pipe);
934 935 936 937

	return ret;
}

A
Al Viro 已提交
938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017
/**
 * 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
1018 1019
		iov_iter_bvec(&from, ITER_BVEC | WRITE, array, n,
			      sd.total_len - left);
1020
		ret = vfs_iter_write(out, &from, &sd.pos);
A
Al Viro 已提交
1021 1022 1023 1024 1025
		if (ret <= 0)
			break;

		sd.num_spliced += ret;
		sd.total_len -= ret;
1026
		*ppos = sd.pos;
A
Al Viro 已提交
1027 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

		/* 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);

1062 1063
static int write_pipe_buf(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
			  struct splice_desc *sd)
1064
{
1065 1066
	int ret;
	void *data;
1067
	loff_t tmp = sd->pos;
1068

A
Al Viro 已提交
1069
	data = kmap(buf->page);
1070
	ret = __kernel_write(sd->u.file, data + buf->offset, sd->len, &tmp);
A
Al Viro 已提交
1071
	kunmap(buf->page);
1072 1073

	return ret;
1074 1075 1076 1077 1078 1079
}

static ssize_t default_file_splice_write(struct pipe_inode_info *pipe,
					 struct file *out, loff_t *ppos,
					 size_t len, unsigned int flags)
{
1080
	ssize_t ret;
1081

1082 1083 1084
	ret = splice_from_pipe(pipe, out, ppos, len, flags, write_pipe_buf);
	if (ret > 0)
		*ppos += ret;
1085

1086
	return ret;
1087 1088
}

1089 1090
/**
 * generic_splice_sendpage - splice data from a pipe to a socket
1091
 * @pipe:	pipe to splice from
1092
 * @out:	socket to write to
1093
 * @ppos:	position in @out
1094 1095 1096
 * @len:	number of bytes to splice
 * @flags:	splice modifier flags
 *
1097 1098 1099
 * Description:
 *    Will send @len bytes from the pipe to a network socket. No data copying
 *    is involved.
1100 1101
 *
 */
1102
ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
1103
				loff_t *ppos, size_t len, unsigned int flags)
1104
{
1105
	return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
1106 1107
}

1108
EXPORT_SYMBOL(generic_splice_sendpage);
J
Jeff Garzik 已提交
1109

1110 1111 1112
/*
 * Attempt to initiate a splice from pipe to file.
 */
1113
static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
1114
			   loff_t *ppos, size_t len, unsigned int flags)
1115
{
1116 1117
	ssize_t (*splice_write)(struct pipe_inode_info *, struct file *,
				loff_t *, size_t, unsigned int);
1118

A
Al Viro 已提交
1119
	if (out->f_op->splice_write)
1120 1121
		splice_write = out->f_op->splice_write;
	else
1122 1123
		splice_write = default_file_splice_write;

1124
	return splice_write(pipe, out, ppos, len, flags);
1125 1126
}

1127 1128 1129
/*
 * Attempt to initiate a splice from a file to a pipe.
 */
1130 1131 1132
static long do_splice_to(struct file *in, loff_t *ppos,
			 struct pipe_inode_info *pipe, size_t len,
			 unsigned int flags)
1133
{
1134 1135
	ssize_t (*splice_read)(struct file *, loff_t *,
			       struct pipe_inode_info *, size_t, unsigned int);
1136 1137
	int ret;

1138
	if (unlikely(!(in->f_mode & FMODE_READ)))
1139 1140
		return -EBADF;

1141
	ret = rw_verify_area(READ, in, ppos, len);
1142 1143 1144
	if (unlikely(ret < 0))
		return ret;

A
Al Viro 已提交
1145
	if (in->f_op->splice_read)
1146 1147
		splice_read = in->f_op->splice_read;
	else
1148 1149 1150
		splice_read = default_file_splice_read;

	return splice_read(in, ppos, pipe, len, flags);
1151 1152
}

1153 1154 1155 1156 1157 1158 1159 1160 1161
/**
 * 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
1162
 *    pipe is cached in the process, and reused during the lifetime of
1163 1164
 *    that process.
 *
J
Jens Axboe 已提交
1165 1166 1167
 */
ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
			       splice_direct_actor *actor)
1168 1169 1170 1171
{
	struct pipe_inode_info *pipe;
	long ret, bytes;
	umode_t i_mode;
J
Jens Axboe 已提交
1172
	size_t len;
1173
	int i, flags, more;
1174 1175 1176 1177 1178 1179

	/*
	 * 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
1180
	i_mode = file_inode(in)->i_mode;
1181 1182 1183 1184 1185 1186 1187 1188
	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;
1189
	if (unlikely(!pipe)) {
A
Al Viro 已提交
1190
		pipe = alloc_pipe_info();
1191 1192 1193 1194 1195
		if (!pipe)
			return -ENOMEM;

		/*
		 * We don't have an immediate reader, but we'll read the stuff
1196
		 * out of the pipe right after the splice_to_pipe(). So set
1197 1198 1199 1200 1201 1202 1203 1204
		 * PIPE_READERS appropriately.
		 */
		pipe->readers = 1;

		current->splice_pipe = pipe;
	}

	/*
I
Ingo Molnar 已提交
1205
	 * Do the splice.
1206 1207 1208
	 */
	ret = 0;
	bytes = 0;
J
Jens Axboe 已提交
1209 1210 1211 1212 1213 1214 1215
	len = sd->total_len;
	flags = sd->flags;

	/*
	 * Don't block on output, we have to drain the direct pipe.
	 */
	sd->flags &= ~SPLICE_F_NONBLOCK;
1216
	more = sd->flags & SPLICE_F_MORE;
1217 1218

	while (len) {
1219
		size_t read_len;
1220
		loff_t pos = sd->pos, prev_pos = pos;
1221

1222
		ret = do_splice_to(in, &pos, pipe, len, flags);
1223
		if (unlikely(ret <= 0))
1224 1225 1226
			goto out_release;

		read_len = ret;
J
Jens Axboe 已提交
1227
		sd->total_len = read_len;
1228

1229 1230 1231 1232 1233 1234 1235 1236 1237
		/*
		 * 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;
1238 1239 1240 1241 1242
		/*
		 * 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
1243
		ret = actor(pipe, sd);
1244 1245
		if (unlikely(ret <= 0)) {
			sd->pos = prev_pos;
1246
			goto out_release;
1247
		}
1248 1249 1250

		bytes += ret;
		len -= ret;
1251
		sd->pos = pos;
1252

1253 1254
		if (ret < read_len) {
			sd->pos = prev_pos + ret;
1255
			goto out_release;
1256
		}
1257 1258
	}

1259
done:
1260
	pipe->nrbufs = pipe->curbuf = 0;
1261
	file_accessed(in);
1262 1263 1264 1265 1266 1267 1268
	return bytes;

out_release:
	/*
	 * If we did an incomplete transfer we must release
	 * the pipe buffers in question:
	 */
1269
	for (i = 0; i < pipe->buffers; i++) {
1270 1271 1272 1273 1274 1275 1276 1277
		struct pipe_buffer *buf = pipe->bufs + i;

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

1278 1279
	if (!bytes)
		bytes = ret;
J
Jens Axboe 已提交
1280

1281
	goto done;
J
Jens Axboe 已提交
1282 1283 1284 1285 1286 1287
}
EXPORT_SYMBOL(splice_direct_to_actor);

static int direct_splice_actor(struct pipe_inode_info *pipe,
			       struct splice_desc *sd)
{
1288
	struct file *file = sd->u.file;
J
Jens Axboe 已提交
1289

1290
	return do_splice_from(pipe, file, sd->opos, sd->total_len,
1291
			      sd->flags);
J
Jens Axboe 已提交
1292 1293
}

1294 1295 1296 1297 1298
/**
 * do_splice_direct - splices data directly between two files
 * @in:		file to splice from
 * @ppos:	input file offset
 * @out:	file to splice to
1299
 * @opos:	output file offset
1300 1301 1302 1303 1304 1305 1306 1307 1308 1309
 * @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
1310
long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
1311
		      loff_t *opos, size_t len, unsigned int flags)
J
Jens Axboe 已提交
1312 1313 1314 1315 1316 1317
{
	struct splice_desc sd = {
		.len		= len,
		.total_len	= len,
		.flags		= flags,
		.pos		= *ppos,
1318
		.u.file		= out,
1319
		.opos		= opos,
J
Jens Axboe 已提交
1320
	};
1321
	long ret;
J
Jens Axboe 已提交
1322

1323 1324 1325 1326 1327 1328 1329 1330 1331 1332
	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
1333
	ret = splice_direct_to_actor(in, &sd, direct_splice_actor);
1334
	if (ret > 0)
1335
		*ppos = sd.pos;
1336

J
Jens Axboe 已提交
1337
	return ret;
1338
}
1339
EXPORT_SYMBOL(do_splice_direct);
1340

1341 1342 1343
static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
			       struct pipe_inode_info *opipe,
			       size_t len, unsigned int flags);
1344

1345 1346 1347
/*
 * Determine where to splice to/from.
 */
1348 1349 1350
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)
1351
{
1352 1353
	struct pipe_inode_info *ipipe;
	struct pipe_inode_info *opipe;
1354
	loff_t offset;
J
Jens Axboe 已提交
1355
	long ret;
1356

1357 1358
	ipipe = get_pipe_info(in);
	opipe = get_pipe_info(out);
1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377

	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) {
1378 1379
		if (off_in)
			return -ESPIPE;
1380
		if (off_out) {
1381
			if (!(out->f_mode & FMODE_PWRITE))
1382
				return -EINVAL;
1383
			if (copy_from_user(&offset, off_out, sizeof(loff_t)))
1384
				return -EFAULT;
1385 1386 1387
		} else {
			offset = out->f_pos;
		}
1388

1389 1390 1391 1392 1393 1394 1395 1396 1397 1398
		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;

1399
		file_start_write(out);
1400
		ret = do_splice_from(ipipe, out, &offset, len, flags);
1401
		file_end_write(out);
J
Jens Axboe 已提交
1402

1403 1404 1405
		if (!off_out)
			out->f_pos = offset;
		else if (copy_to_user(off_out, &offset, sizeof(loff_t)))
J
Jens Axboe 已提交
1406 1407 1408
			ret = -EFAULT;

		return ret;
1409
	}
1410

1411
	if (opipe) {
1412 1413
		if (off_out)
			return -ESPIPE;
1414
		if (off_in) {
1415
			if (!(in->f_mode & FMODE_PREAD))
1416
				return -EINVAL;
1417
			if (copy_from_user(&offset, off_in, sizeof(loff_t)))
1418
				return -EFAULT;
1419 1420 1421
		} else {
			offset = in->f_pos;
		}
1422

1423
		ret = do_splice_to(in, &offset, opipe, len, flags);
J
Jens Axboe 已提交
1424

1425 1426 1427
		if (!off_in)
			in->f_pos = offset;
		else if (copy_to_user(off_in, &offset, sizeof(loff_t)))
J
Jens Axboe 已提交
1428 1429 1430
			ret = -EFAULT;

		return ret;
1431
	}
1432 1433 1434 1435

	return -EINVAL;
}

1436 1437 1438 1439 1440 1441 1442 1443 1444
/*
 * 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,
1445
				struct partial_page *partial, bool aligned,
1446
				unsigned int pipe_buffers)
1447 1448 1449 1450 1451
{
	int buffers = 0, error = 0;

	while (nr_vecs) {
		unsigned long off, npages;
1452
		struct iovec entry;
1453 1454 1455 1456
		void __user *base;
		size_t len;
		int i;

1457
		error = -EFAULT;
N
Nick Piggin 已提交
1458
		if (copy_from_user(&entry, iov, sizeof(entry)))
1459 1460
			break;

1461 1462 1463
		base = entry.iov_base;
		len = entry.iov_len;

1464 1465 1466
		/*
		 * Sanity check this iovec. 0 read succeeds.
		 */
1467
		error = 0;
1468 1469 1470
		if (unlikely(!len))
			break;
		error = -EFAULT;
1471
		if (!access_ok(VERIFY_READ, base, len))
1472 1473 1474 1475 1476 1477 1478
			break;

		/*
		 * Get this base offset and number of pages, then map
		 * in the user pages.
		 */
		off = (unsigned long) base & ~PAGE_MASK;
1479 1480 1481 1482 1483 1484 1485 1486 1487

		/*
		 * 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;

1488
		npages = (off + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1489 1490
		if (npages > pipe_buffers - buffers)
			npages = pipe_buffers - buffers;
1491

N
Nick Piggin 已提交
1492 1493
		error = get_user_pages_fast((unsigned long)base, npages,
					0, &pages[buffers]);
1494 1495 1496 1497 1498 1499 1500 1501

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

		/*
		 * Fill this contiguous range into the partial page map.
		 */
		for (i = 0; i < error; i++) {
1502
			const int plen = min_t(size_t, len, PAGE_SIZE - off);
1503 1504 1505 1506 1507 1508 1509 1510 1511 1512 1513 1514 1515 1516 1517 1518 1519 1520 1521 1522 1523 1524

			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.
		 */
1525
		if (error < npages || buffers == pipe_buffers)
1526 1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537
			break;

		nr_vecs--;
		iov++;
	}

	if (buffers)
		return buffers;

	return error;
}

1538 1539 1540
static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
			struct splice_desc *sd)
{
1541 1542
	int n = copy_page_to_iter(buf->page, buf->offset, sd->len, sd->u.data);
	return n == sd->len ? n : -EFAULT;
1543 1544 1545 1546 1547 1548
}

/*
 * For lack of a better implementation, implement vmsplice() to userspace
 * as a simple copy of the pipes pages to the user iov.
 */
1549
static long vmsplice_to_user(struct file *file, const struct iovec __user *uiov,
1550 1551 1552 1553 1554
			     unsigned long nr_segs, unsigned int flags)
{
	struct pipe_inode_info *pipe;
	struct splice_desc sd;
	long ret;
1555 1556 1557
	struct iovec iovstack[UIO_FASTIOV];
	struct iovec *iov = iovstack;
	struct iov_iter iter;
1558

1559
	pipe = get_pipe_info(file);
1560 1561 1562
	if (!pipe)
		return -EBADF;

1563 1564 1565 1566
	ret = import_iovec(READ, uiov, nr_segs,
			   ARRAY_SIZE(iovstack), &iov, &iter);
	if (ret < 0)
		return ret;
1567

1568
	sd.total_len = iov_iter_count(&iter);
1569 1570 1571 1572
	sd.len = 0;
	sd.flags = flags;
	sd.u.data = &iter;
	sd.pos = 0;
1573

1574 1575 1576 1577 1578
	if (sd.total_len) {
		pipe_lock(pipe);
		ret = __splice_from_pipe(pipe, &sd, pipe_to_user);
		pipe_unlock(pipe);
	}
1579

1580
	kfree(iov);
1581 1582 1583
	return ret;
}

1584 1585 1586 1587 1588
/*
 * 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.
 */
1589 1590
static long vmsplice_to_pipe(struct file *file, const struct iovec __user *iov,
			     unsigned long nr_segs, unsigned int flags)
1591
{
1592
	struct pipe_inode_info *pipe;
1593 1594
	struct page *pages[PIPE_DEF_BUFFERS];
	struct partial_page partial[PIPE_DEF_BUFFERS];
1595 1596 1597
	struct splice_pipe_desc spd = {
		.pages = pages,
		.partial = partial,
1598
		.nr_pages_max = PIPE_DEF_BUFFERS,
1599 1600
		.flags = flags,
		.ops = &user_page_pipe_buf_ops,
1601
		.spd_release = spd_release_page,
1602
	};
1603
	long ret;
1604

1605
	pipe = get_pipe_info(file);
1606
	if (!pipe)
1607 1608
		return -EBADF;

1609 1610 1611 1612
	if (splice_grow_spd(pipe, &spd))
		return -ENOMEM;

	spd.nr_pages = get_iovec_page_array(iov, nr_segs, spd.pages,
1613
					    spd.partial, false,
1614
					    spd.nr_pages_max);
1615
	if (spd.nr_pages <= 0)
1616 1617 1618
		ret = spd.nr_pages;
	else
		ret = splice_to_pipe(pipe, &spd);
1619

1620
	splice_shrink_spd(&spd);
1621
	return ret;
1622 1623
}

1624 1625 1626 1627 1628 1629 1630 1631 1632 1633 1634 1635 1636 1637 1638 1639
/*
 * 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().
 *
 */
1640 1641
SYSCALL_DEFINE4(vmsplice, int, fd, const struct iovec __user *, iov,
		unsigned long, nr_segs, unsigned int, flags)
1642
{
1643
	struct fd f;
1644 1645
	long error;

1646 1647 1648 1649 1650
	if (unlikely(nr_segs > UIO_MAXIOV))
		return -EINVAL;
	else if (unlikely(!nr_segs))
		return 0;

1651
	error = -EBADF;
1652 1653 1654 1655 1656 1657 1658 1659
	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);
1660 1661 1662 1663 1664
	}

	return error;
}

1665 1666 1667 1668 1669 1670 1671 1672 1673 1674 1675 1676 1677 1678 1679 1680 1681 1682 1683 1684 1685
#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

1686 1687 1688
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)
1689
{
1690
	struct fd in, out;
1691 1692 1693 1694 1695 1696
	long error;

	if (unlikely(!len))
		return 0;

	error = -EBADF;
1697 1698 1699 1700 1701 1702 1703 1704
	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,
1705
							  len, flags);
1706
				fdput(out);
1707 1708
			}
		}
1709
		fdput(in);
1710 1711 1712
	}
	return error;
}
1713

1714 1715 1716 1717
/*
 * Make sure there's data to read. Wait for input if we can, otherwise
 * return an appropriate error.
 */
1718
static int ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1719 1720 1721 1722 1723 1724 1725 1726 1727 1728 1729
{
	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;
1730
	pipe_lock(pipe);
1731 1732 1733 1734 1735 1736 1737 1738 1739 1740 1741 1742 1743 1744 1745 1746 1747

	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);
	}

1748
	pipe_unlock(pipe);
1749 1750 1751 1752 1753 1754 1755
	return ret;
}

/*
 * Make sure there's writeable room. Wait for room if we can, otherwise
 * return an appropriate error.
 */
1756
static int opipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1757 1758 1759 1760 1761 1762 1763
{
	int ret;

	/*
	 * Check ->nrbufs without the inode lock first. This function
	 * is speculative anyways, so missing one is ok.
	 */
1764
	if (pipe->nrbufs < pipe->buffers)
1765 1766 1767
		return 0;

	ret = 0;
1768
	pipe_lock(pipe);
1769

1770
	while (pipe->nrbufs >= pipe->buffers) {
1771 1772 1773 1774 1775 1776 1777 1778 1779 1780 1781 1782 1783 1784 1785 1786 1787 1788
		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--;
	}

1789
	pipe_unlock(pipe);
1790 1791 1792
	return ret;
}

1793 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
/*
 * 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.
		 */
1836
		if (!ipipe->nrbufs || opipe->nrbufs >= opipe->buffers) {
1837 1838 1839 1840 1841 1842 1843 1844 1845 1846 1847 1848 1849 1850 1851 1852 1853 1854 1855 1856
			/* 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;
1857
		nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1);
1858 1859 1860 1861 1862 1863 1864 1865 1866
		obuf = opipe->bufs + nbuf;

		if (len >= ibuf->len) {
			/*
			 * Simply move the whole buffer from ipipe to opipe
			 */
			*obuf = *ibuf;
			ibuf->ops = NULL;
			opipe->nrbufs++;
1867
			ipipe->curbuf = (ipipe->curbuf + 1) & (ipipe->buffers - 1);
1868 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
			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
1899 1900 1901
	if (ret > 0)
		wakeup_pipe_readers(opipe);

1902 1903 1904 1905 1906 1907
	if (input_wakeup)
		wakeup_pipe_writers(ipipe);

	return ret;
}

1908 1909 1910 1911 1912 1913 1914 1915
/*
 * 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;
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 1922
	 * could deadlock (one doing tee from A -> B, the other from B -> A).
	 */
1923
	pipe_double_lock(ipipe, opipe);
1924

1925
	do {
1926 1927 1928 1929 1930 1931 1932
		if (!opipe->readers) {
			send_sig(SIGPIPE, current, 0);
			if (!ret)
				ret = -EPIPE;
			break;
		}

1933 1934 1935 1936
		/*
		 * If we have iterated all input buffers or ran out of
		 * output room, break.
		 */
1937
		if (i >= ipipe->nrbufs || opipe->nrbufs >= opipe->buffers)
1938
			break;
1939

1940 1941
		ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (ipipe->buffers-1));
		nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1);
1942 1943

		/*
1944 1945
		 * Get a reference to this pipe buffer,
		 * so we can copy the contents over.
1946
		 */
1947 1948 1949 1950 1951
		ibuf->ops->get(ipipe, ibuf);

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

1952
		/*
1953 1954
		 * Don't inherit the gift flag, we need to
		 * prevent multiple steals of this page.
1955
		 */
1956
		obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1957

1958 1959
		if (obuf->len > len)
			obuf->len = len;
1960

1961 1962 1963 1964 1965
		opipe->nrbufs++;
		ret += obuf->len;
		len -= obuf->len;
		i++;
	} while (len);
1966

1967 1968 1969 1970 1971 1972 1973
	/*
	 * 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;

1974 1975
	pipe_unlock(ipipe);
	pipe_unlock(opipe);
1976

1977 1978 1979
	/*
	 * If we put data in the output pipe, wakeup any potential readers.
	 */
N
Namhyung Kim 已提交
1980 1981
	if (ret > 0)
		wakeup_pipe_readers(opipe);
1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994

	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)
{
1995 1996
	struct pipe_inode_info *ipipe = get_pipe_info(in);
	struct pipe_inode_info *opipe = get_pipe_info(out);
1997
	int ret = -EINVAL;
1998 1999

	/*
2000 2001
	 * Duplicate the contents of ipipe to opipe without actually
	 * copying the data.
2002
	 */
2003 2004 2005 2006 2007
	if (ipipe && opipe && ipipe != opipe) {
		/*
		 * Keep going, unless we encounter an error. The ipipe/opipe
		 * ordering doesn't really matter.
		 */
2008
		ret = ipipe_prep(ipipe, flags);
2009
		if (!ret) {
2010
			ret = opipe_prep(opipe, flags);
2011
			if (!ret)
2012 2013 2014
				ret = link_pipe(ipipe, opipe, len, flags);
		}
	}
2015

2016
	return ret;
2017 2018
}

2019
SYSCALL_DEFINE4(tee, int, fdin, int, fdout, size_t, len, unsigned int, flags)
2020
{
2021 2022
	struct fd in;
	int error;
2023 2024 2025 2026 2027

	if (unlikely(!len))
		return 0;

	error = -EBADF;
2028 2029 2030 2031 2032 2033 2034 2035 2036
	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);
2037 2038
			}
		}
2039
 		fdput(in);
2040 2041 2042 2043
 	}

	return error;
}