splice.c 47.1 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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#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>
30
#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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	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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	.map = generic_pipe_buf_map,
	.unmap = generic_pipe_buf_unmap,
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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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	.map = generic_pipe_buf_map,
	.unmap = generic_pipe_buf_unmap,
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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.
 *
185
 */
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ssize_t splice_to_pipe(struct pipe_inode_info *pipe,
		       struct splice_pipe_desc *spd)
188
{
189
	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;
195

196
	pipe_lock(pipe);
197 198

	for (;;) {
199
		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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225
			if (!--spd->nr_pages)
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				break;
227
			if (pipe->nrbufs < pipe->buffers)
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				continue;

			break;
		}

233
		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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263
	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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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.
 */
278
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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	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) {
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		/*
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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) {
			/*
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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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						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];
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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);
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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);
443
			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.
				 */
450
				if (error == AOP_TRUNCATED_PAGE)
451 452
					error = 0;

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				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;
471 472

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

			/*
480
			 * force quit after adding this page
481
			 */
482 483
			this_len = min(this_len, plen - loff);
			len = this_len;
484
		}
485

486 487
		spd.partial[page_nr].offset = loff;
		spd.partial[page_nr].len = this_len;
488
		len -= this_len;
489
		loff = 0;
490 491
		spd.nr_pages++;
		index++;
492 493
	}

494
	/*
495
	 * 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)
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		page_cache_release(spd.pages[page_nr++]);
500
	in->f_ra.prev_pos = (loff_t)index << PAGE_CACHE_SHIFT;
501

502
	if (spd.nr_pages)
503
		error = splice_to_pipe(pipe, &spd);
504

505
	splice_shrink_spd(&spd);
506
	return error;
507 508
}

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/**
 * generic_file_splice_read - splice data from file to a pipe
 * @in:		file to splice from
512
 * @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.
 *
522
 */
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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)
526
{
527
	loff_t isize, left;
528
	int ret;
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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;
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538
	ret = __generic_file_splice_read(in, ppos, pipe, len, flags);
539
	if (ret > 0) {
540
		*ppos += ret;
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		file_accessed(in);
	}
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	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,
	.map = generic_pipe_buf_map,
	.unmap = generic_pipe_buf_unmap,
	.confirm = generic_pipe_buf_confirm,
	.release = generic_pipe_buf_release,
	.steal = generic_pipe_buf_steal,
	.get = generic_pipe_buf_get,
};

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;
}

574
ssize_t kernel_write(struct file *file, const char *buf, size_t count,
575
			    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() */
583
	res = vfs_write(file, (__force const char __user *)buf, count, &pos);
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	set_fs(old_fs);

	return res;
}
588
EXPORT_SYMBOL(kernel_write);
589

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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,
607
		.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;

627
	for (i = 0; i < nr_pages && i < spd.nr_pages_max && len; i++) {
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		struct page *page;

630
		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);
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		vec[i].iov_base = (void __user *) page_address(page);
637
		vec[i].iov_len = this_len;
638
		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;
647
		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);
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		spd.partial[i].offset = 0;
		spd.partial[i].len = this_len;
659
		if (!this_len) {
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			__free_page(spd.pages[i]);
			spd.pages[i] = NULL;
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			nr_freed++;
		}
		res -= this_len;
	}
	spd.nr_pages -= nr_freed;

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

672 673 674
shrink_ret:
	if (vec != __vec)
		kfree(vec);
675
	splice_shrink_spd(&spd);
676 677 678
	return res;

err:
679
	for (i = 0; i < spd.nr_pages; i++)
680
		__free_page(spd.pages[i]);
681

682 683
	res = error;
	goto shrink_ret;
684 685 686
}
EXPORT_SYMBOL(default_file_splice_read);

687
/*
688
 * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
J
Jens Axboe 已提交
689
 * using sendpage(). Return the number of bytes sent.
690
 */
691
static int pipe_to_sendpage(struct pipe_inode_info *pipe,
692 693
			    struct pipe_buffer *buf, struct splice_desc *sd)
{
694
	struct file *file = sd->u.file;
695
	loff_t pos = sd->pos;
696
	int more;
697

698 699 700
	if (!likely(file->f_op && file->f_op->sendpage))
		return -EINVAL;

701
	more = (sd->flags & SPLICE_F_MORE) ? MSG_MORE : 0;
702 703

	if (sd->len < sd->total_len && pipe->nrbufs > 1)
704
		more |= MSG_SENDPAGE_NOTLAST;
705

706 707
	return file->f_op->sendpage(file, buf->page, buf->offset,
				    sd->len, &pos, more);
708 709 710 711 712 713 714 715 716 717 718 719 720 721 722
}

/*
 * This is a little more tricky than the file -> pipe splicing. There are
 * basically three cases:
 *
 *	- Destination page already exists in the address space and there
 *	  are users of it. For that case we have no other option that
 *	  copying the data. Tough luck.
 *	- Destination page already exists in the address space, but there
 *	  are no users of it. Make sure it's uptodate, then drop it. Fall
 *	  through to last case.
 *	- Destination page does not exist, we can add the pipe page to
 *	  the page cache and avoid the copy.
 *
723 724 725 726 727 728
 * If asked to move pages to the output file (SPLICE_F_MOVE is set in
 * sd->flags), we attempt to migrate pages from the pipe to the output
 * file address space page cache. This is possible if no one else has
 * the pipe page referenced outside of the pipe and page cache. If
 * SPLICE_F_MOVE isn't set, or we cannot move the page, we simply create
 * a new page in the output file page cache and fill/dirty that.
729
 */
730 731
int pipe_to_file(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
		 struct splice_desc *sd)
732
{
733
	struct file *file = sd->u.file;
734
	struct address_space *mapping = file->f_mapping;
J
Jens Axboe 已提交
735
	unsigned int offset, this_len;
736
	struct page *page;
737
	void *fsdata;
738
	int ret;
739 740 741

	offset = sd->pos & ~PAGE_CACHE_MASK;

J
Jens Axboe 已提交
742 743 744 745
	this_len = sd->len;
	if (this_len + offset > PAGE_CACHE_SIZE)
		this_len = PAGE_CACHE_SIZE - offset;

746 747 748 749
	ret = pagecache_write_begin(file, mapping, sd->pos, this_len,
				AOP_FLAG_UNINTERRUPTIBLE, &page, &fsdata);
	if (unlikely(ret))
		goto out;
750

751
	if (buf->page != page) {
752
		char *src = buf->ops->map(pipe, buf, 1);
753
		char *dst = kmap_atomic(page);
754

J
Jens Axboe 已提交
755
		memcpy(dst + offset, src + buf->offset, this_len);
756
		flush_dcache_page(page);
757
		kunmap_atomic(dst);
758
		buf->ops->unmap(pipe, buf, src);
759
	}
760 761
	ret = pagecache_write_end(file, mapping, sd->pos, this_len, this_len,
				page, fsdata);
762 763 764
out:
	return ret;
}
765
EXPORT_SYMBOL(pipe_to_file);
766

767 768 769 770 771 772 773 774
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);
}

775
/**
776
 * splice_from_pipe_feed - feed available data from a pipe to a file
777 778 779 780 781
 * @pipe:	pipe to splice from
 * @sd:		information to @actor
 * @actor:	handler that splices the data
 *
 * Description:
782 783 784 785 786 787 788
 *    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.
789
 *
790 791 792 793
 *    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.
794
 */
795 796
int splice_from_pipe_feed(struct pipe_inode_info *pipe, struct splice_desc *sd,
			  splice_actor *actor)
797
{
798
	int ret;
799

800 801 802
	while (pipe->nrbufs) {
		struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
		const struct pipe_buf_operations *ops = buf->ops;
803

804 805 806
		sd->len = buf->len;
		if (sd->len > sd->total_len)
			sd->len = sd->total_len;
807

808 809
		ret = buf->ops->confirm(pipe, buf);
		if (unlikely(ret)) {
810 811 812 813
			if (ret == -ENODATA)
				ret = 0;
			return ret;
		}
814 815 816 817 818

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

819 820 821 822 823 824 825 826 827 828 829
		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);
830
			pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1);
831
			pipe->nrbufs--;
A
Al Viro 已提交
832
			if (pipe->files)
833 834
				sd->need_wakeup = true;
		}
835

836 837 838
		if (!sd->total_len)
			return 0;
	}
839

840 841 842
	return 1;
}
EXPORT_SYMBOL(splice_from_pipe_feed);
843

844 845 846 847 848 849 850 851 852 853 854 855 856 857 858
/**
 * 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.
 */
int splice_from_pipe_next(struct pipe_inode_info *pipe, struct splice_desc *sd)
{
	while (!pipe->nrbufs) {
		if (!pipe->writers)
			return 0;
J
Jens Axboe 已提交
859

860 861
		if (!pipe->waiting_writers && sd->num_spliced)
			return 0;
I
Ingo Molnar 已提交
862

863 864
		if (sd->flags & SPLICE_F_NONBLOCK)
			return -EAGAIN;
865

866 867
		if (signal_pending(current))
			return -ERESTARTSYS;
868

869 870 871
		if (sd->need_wakeup) {
			wakeup_pipe_writers(pipe);
			sd->need_wakeup = false;
872 873
		}

874 875
		pipe_wait(pipe);
	}
876

877 878 879
	return 1;
}
EXPORT_SYMBOL(splice_from_pipe_next);
880

881 882
/**
 * splice_from_pipe_begin - start splicing from pipe
883
 * @sd:		information about the splice operation
884 885 886 887 888 889 890 891 892 893 894 895
 *
 * 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.
 */
void splice_from_pipe_begin(struct splice_desc *sd)
{
	sd->num_spliced = 0;
	sd->need_wakeup = false;
}
EXPORT_SYMBOL(splice_from_pipe_begin);
896

897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912
/**
 * 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().
 */
void splice_from_pipe_end(struct pipe_inode_info *pipe, struct splice_desc *sd)
{
	if (sd->need_wakeup)
		wakeup_pipe_writers(pipe);
}
EXPORT_SYMBOL(splice_from_pipe_end);
913

914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930
/**
 * __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;
931

932 933 934 935 936 937 938 939 940
	splice_from_pipe_begin(sd);
	do {
		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;
941
}
M
Mark Fasheh 已提交
942
EXPORT_SYMBOL(__splice_from_pipe);
943

944 945 946 947 948 949 950 951 952 953
/**
 * 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:
954
 *    See __splice_from_pipe. This function locks the pipe inode,
955 956 957
 *    otherwise it's identical to __splice_from_pipe().
 *
 */
958 959 960 961 962
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
963 964 965 966
	struct splice_desc sd = {
		.total_len = len,
		.flags = flags,
		.pos = *ppos,
967
		.u.file = out,
J
Jens Axboe 已提交
968
	};
969

970
	pipe_lock(pipe);
J
Jens Axboe 已提交
971
	ret = __splice_from_pipe(pipe, &sd, actor);
972
	pipe_unlock(pipe);
973 974 975 976

	return ret;
}

977 978
/**
 * generic_file_splice_write - splice data from a pipe to a file
979
 * @pipe:	pipe info
980
 * @out:	file to write to
981
 * @ppos:	position in @out
982 983 984
 * @len:	number of bytes to splice
 * @flags:	splice modifier flags
 *
985 986 987
 * Description:
 *    Will either move or copy pages (determined by @flags options) from
 *    the given pipe inode to the given file.
988 989
 *
 */
990 991
ssize_t
generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
992
			  loff_t *ppos, size_t len, unsigned int flags)
993
{
994
	struct address_space *mapping = out->f_mapping;
995
	struct inode *inode = mapping->host;
996 997 998 999 1000 1001
	struct splice_desc sd = {
		.total_len = len,
		.flags = flags,
		.pos = *ppos,
		.u.file = out,
	};
1002 1003
	ssize_t ret;

1004
	pipe_lock(pipe);
1005 1006 1007 1008 1009 1010 1011 1012 1013

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

		mutex_lock_nested(&inode->i_mutex, I_MUTEX_CHILD);
		ret = file_remove_suid(out);
1014
		if (!ret) {
1015 1016 1017 1018
			ret = file_update_time(out);
			if (!ret)
				ret = splice_from_pipe_feed(pipe, &sd,
							    pipe_to_file);
1019
		}
1020 1021 1022 1023
		mutex_unlock(&inode->i_mutex);
	} while (ret > 0);
	splice_from_pipe_end(pipe, &sd);

1024
	pipe_unlock(pipe);
1025 1026 1027 1028

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

J
Jens Axboe 已提交
1029
	if (ret > 0) {
1030
		int err;
1031

1032 1033 1034 1035 1036
		err = generic_write_sync(out, *ppos, ret);
		if (err)
			ret = err;
		else
			*ppos += ret;
1037
		balance_dirty_pages_ratelimited(mapping);
1038 1039 1040
	}

	return ret;
1041 1042
}

1043 1044
EXPORT_SYMBOL(generic_file_splice_write);

1045 1046
static int write_pipe_buf(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
			  struct splice_desc *sd)
1047
{
1048 1049
	int ret;
	void *data;
1050
	loff_t tmp = sd->pos;
1051 1052

	data = buf->ops->map(pipe, buf, 0);
1053
	ret = __kernel_write(sd->u.file, data + buf->offset, sd->len, &tmp);
1054 1055 1056
	buf->ops->unmap(pipe, buf, data);

	return ret;
1057 1058 1059 1060 1061 1062
}

static ssize_t default_file_splice_write(struct pipe_inode_info *pipe,
					 struct file *out, loff_t *ppos,
					 size_t len, unsigned int flags)
{
1063
	ssize_t ret;
1064

1065 1066 1067
	ret = splice_from_pipe(pipe, out, ppos, len, flags, write_pipe_buf);
	if (ret > 0)
		*ppos += ret;
1068

1069
	return ret;
1070 1071
}

1072 1073
/**
 * generic_splice_sendpage - splice data from a pipe to a socket
1074
 * @pipe:	pipe to splice from
1075
 * @out:	socket to write to
1076
 * @ppos:	position in @out
1077 1078 1079
 * @len:	number of bytes to splice
 * @flags:	splice modifier flags
 *
1080 1081 1082
 * Description:
 *    Will send @len bytes from the pipe to a network socket. No data copying
 *    is involved.
1083 1084
 *
 */
1085
ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
1086
				loff_t *ppos, size_t len, unsigned int flags)
1087
{
1088
	return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
1089 1090
}

1091
EXPORT_SYMBOL(generic_splice_sendpage);
J
Jeff Garzik 已提交
1092

1093 1094 1095
/*
 * Attempt to initiate a splice from pipe to file.
 */
1096
static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
1097
			   loff_t *ppos, size_t len, unsigned int flags)
1098
{
1099 1100
	ssize_t (*splice_write)(struct pipe_inode_info *, struct file *,
				loff_t *, size_t, unsigned int);
1101 1102
	int ret;

1103
	if (unlikely(!(out->f_mode & FMODE_WRITE)))
1104 1105
		return -EBADF;

1106 1107 1108
	if (unlikely(out->f_flags & O_APPEND))
		return -EINVAL;

1109
	ret = rw_verify_area(WRITE, out, ppos, len);
1110 1111 1112
	if (unlikely(ret < 0))
		return ret;

1113 1114 1115
	if (out->f_op && out->f_op->splice_write)
		splice_write = out->f_op->splice_write;
	else
1116 1117
		splice_write = default_file_splice_write;

1118 1119 1120 1121
	file_start_write(out);
	ret = splice_write(pipe, out, ppos, len, flags);
	file_end_write(out);
	return ret;
1122 1123
}

1124 1125 1126
/*
 * Attempt to initiate a splice from a file to a pipe.
 */
1127 1128 1129
static long do_splice_to(struct file *in, loff_t *ppos,
			 struct pipe_inode_info *pipe, size_t len,
			 unsigned int flags)
1130
{
1131 1132
	ssize_t (*splice_read)(struct file *, loff_t *,
			       struct pipe_inode_info *, size_t, unsigned int);
1133 1134
	int ret;

1135
	if (unlikely(!(in->f_mode & FMODE_READ)))
1136 1137
		return -EBADF;

1138
	ret = rw_verify_area(READ, in, ppos, len);
1139 1140 1141
	if (unlikely(ret < 0))
		return ret;

1142 1143 1144
	if (in->f_op && in->f_op->splice_read)
		splice_read = in->f_op->splice_read;
	else
1145 1146 1147
		splice_read = default_file_splice_read;

	return splice_read(in, ppos, pipe, len, flags);
1148 1149
}

1150 1151 1152 1153 1154 1155 1156 1157 1158
/**
 * 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
1159
 *    pipe is cached in the process, and reused during the lifetime of
1160 1161
 *    that process.
 *
J
Jens Axboe 已提交
1162 1163 1164
 */
ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
			       splice_direct_actor *actor)
1165 1166 1167 1168
{
	struct pipe_inode_info *pipe;
	long ret, bytes;
	umode_t i_mode;
J
Jens Axboe 已提交
1169 1170
	size_t len;
	int i, flags;
1171 1172 1173 1174 1175 1176

	/*
	 * 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
1177
	i_mode = file_inode(in)->i_mode;
1178 1179 1180 1181 1182 1183 1184 1185
	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;
1186
	if (unlikely(!pipe)) {
A
Al Viro 已提交
1187
		pipe = alloc_pipe_info();
1188 1189 1190 1191 1192
		if (!pipe)
			return -ENOMEM;

		/*
		 * We don't have an immediate reader, but we'll read the stuff
1193
		 * out of the pipe right after the splice_to_pipe(). So set
1194 1195 1196 1197 1198 1199 1200 1201
		 * PIPE_READERS appropriately.
		 */
		pipe->readers = 1;

		current->splice_pipe = pipe;
	}

	/*
I
Ingo Molnar 已提交
1202
	 * Do the splice.
1203 1204 1205
	 */
	ret = 0;
	bytes = 0;
J
Jens Axboe 已提交
1206 1207 1208 1209 1210 1211 1212
	len = sd->total_len;
	flags = sd->flags;

	/*
	 * Don't block on output, we have to drain the direct pipe.
	 */
	sd->flags &= ~SPLICE_F_NONBLOCK;
1213 1214

	while (len) {
1215
		size_t read_len;
1216
		loff_t pos = sd->pos, prev_pos = pos;
1217

1218
		ret = do_splice_to(in, &pos, pipe, len, flags);
1219
		if (unlikely(ret <= 0))
1220 1221 1222
			goto out_release;

		read_len = ret;
J
Jens Axboe 已提交
1223
		sd->total_len = read_len;
1224 1225 1226 1227 1228 1229

		/*
		 * 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
1230
		ret = actor(pipe, sd);
1231 1232
		if (unlikely(ret <= 0)) {
			sd->pos = prev_pos;
1233
			goto out_release;
1234
		}
1235 1236 1237

		bytes += ret;
		len -= ret;
1238
		sd->pos = pos;
1239

1240 1241
		if (ret < read_len) {
			sd->pos = prev_pos + ret;
1242
			goto out_release;
1243
		}
1244 1245
	}

1246
done:
1247
	pipe->nrbufs = pipe->curbuf = 0;
1248
	file_accessed(in);
1249 1250 1251 1252 1253 1254 1255
	return bytes;

out_release:
	/*
	 * If we did an incomplete transfer we must release
	 * the pipe buffers in question:
	 */
1256
	for (i = 0; i < pipe->buffers; i++) {
1257 1258 1259 1260 1261 1262 1263 1264
		struct pipe_buffer *buf = pipe->bufs + i;

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

1265 1266
	if (!bytes)
		bytes = ret;
J
Jens Axboe 已提交
1267

1268
	goto done;
J
Jens Axboe 已提交
1269 1270 1271 1272 1273 1274
}
EXPORT_SYMBOL(splice_direct_to_actor);

static int direct_splice_actor(struct pipe_inode_info *pipe,
			       struct splice_desc *sd)
{
1275
	struct file *file = sd->u.file;
J
Jens Axboe 已提交
1276

1277
	return do_splice_from(pipe, file, sd->opos, sd->total_len,
1278
			      sd->flags);
J
Jens Axboe 已提交
1279 1280
}

1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295
/**
 * do_splice_direct - splices data directly between two files
 * @in:		file to splice from
 * @ppos:	input file offset
 * @out:	file to splice to
 * @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
1296
long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
1297
		      loff_t *opos, size_t len, unsigned int flags)
J
Jens Axboe 已提交
1298 1299 1300 1301 1302 1303
{
	struct splice_desc sd = {
		.len		= len,
		.total_len	= len,
		.flags		= flags,
		.pos		= *ppos,
1304
		.u.file		= out,
1305
		.opos		= opos,
J
Jens Axboe 已提交
1306
	};
1307
	long ret;
J
Jens Axboe 已提交
1308 1309

	ret = splice_direct_to_actor(in, &sd, direct_splice_actor);
1310
	if (ret > 0)
1311
		*ppos = sd.pos;
1312

J
Jens Axboe 已提交
1313
	return ret;
1314 1315
}

1316 1317 1318
static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
			       struct pipe_inode_info *opipe,
			       size_t len, unsigned int flags);
1319

1320 1321 1322
/*
 * Determine where to splice to/from.
 */
1323 1324 1325
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)
1326
{
1327 1328
	struct pipe_inode_info *ipipe;
	struct pipe_inode_info *opipe;
1329
	loff_t offset;
J
Jens Axboe 已提交
1330
	long ret;
1331

1332 1333
	ipipe = get_pipe_info(in);
	opipe = get_pipe_info(out);
1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352

	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) {
1353 1354
		if (off_in)
			return -ESPIPE;
1355
		if (off_out) {
1356
			if (!(out->f_mode & FMODE_PWRITE))
1357
				return -EINVAL;
1358
			if (copy_from_user(&offset, off_out, sizeof(loff_t)))
1359
				return -EFAULT;
1360 1361 1362
		} else {
			offset = out->f_pos;
		}
1363

1364
		ret = do_splice_from(ipipe, out, &offset, len, flags);
J
Jens Axboe 已提交
1365

1366 1367 1368
		if (!off_out)
			out->f_pos = offset;
		else if (copy_to_user(off_out, &offset, sizeof(loff_t)))
J
Jens Axboe 已提交
1369 1370 1371
			ret = -EFAULT;

		return ret;
1372
	}
1373

1374
	if (opipe) {
1375 1376
		if (off_out)
			return -ESPIPE;
1377
		if (off_in) {
1378
			if (!(in->f_mode & FMODE_PREAD))
1379
				return -EINVAL;
1380
			if (copy_from_user(&offset, off_in, sizeof(loff_t)))
1381
				return -EFAULT;
1382 1383 1384
		} else {
			offset = in->f_pos;
		}
1385

1386
		ret = do_splice_to(in, &offset, opipe, len, flags);
J
Jens Axboe 已提交
1387

1388 1389 1390
		if (!off_in)
			in->f_pos = offset;
		else if (copy_to_user(off_in, &offset, sizeof(loff_t)))
J
Jens Axboe 已提交
1391 1392 1393
			ret = -EFAULT;

		return ret;
1394
	}
1395 1396 1397 1398

	return -EINVAL;
}

1399 1400 1401 1402 1403 1404 1405 1406 1407
/*
 * 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,
1408
				struct partial_page *partial, bool aligned,
1409
				unsigned int pipe_buffers)
1410 1411 1412 1413 1414
{
	int buffers = 0, error = 0;

	while (nr_vecs) {
		unsigned long off, npages;
1415
		struct iovec entry;
1416 1417 1418 1419
		void __user *base;
		size_t len;
		int i;

1420
		error = -EFAULT;
N
Nick Piggin 已提交
1421
		if (copy_from_user(&entry, iov, sizeof(entry)))
1422 1423
			break;

1424 1425 1426
		base = entry.iov_base;
		len = entry.iov_len;

1427 1428 1429
		/*
		 * Sanity check this iovec. 0 read succeeds.
		 */
1430
		error = 0;
1431 1432 1433
		if (unlikely(!len))
			break;
		error = -EFAULT;
1434
		if (!access_ok(VERIFY_READ, base, len))
1435 1436 1437 1438 1439 1440 1441
			break;

		/*
		 * Get this base offset and number of pages, then map
		 * in the user pages.
		 */
		off = (unsigned long) base & ~PAGE_MASK;
1442 1443 1444 1445 1446 1447 1448 1449 1450

		/*
		 * 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;

1451
		npages = (off + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1452 1453
		if (npages > pipe_buffers - buffers)
			npages = pipe_buffers - buffers;
1454

N
Nick Piggin 已提交
1455 1456
		error = get_user_pages_fast((unsigned long)base, npages,
					0, &pages[buffers]);
1457 1458 1459 1460 1461 1462 1463 1464

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

		/*
		 * Fill this contiguous range into the partial page map.
		 */
		for (i = 0; i < error; i++) {
1465
			const int plen = min_t(size_t, len, PAGE_SIZE - off);
1466 1467 1468 1469 1470 1471 1472 1473 1474 1475 1476 1477 1478 1479 1480 1481 1482 1483 1484 1485 1486 1487

			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.
		 */
1488
		if (error < npages || buffers == pipe_buffers)
1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500
			break;

		nr_vecs--;
		iov++;
	}

	if (buffers)
		return buffers;

	return error;
}

1501 1502 1503 1504 1505 1506 1507 1508 1509 1510 1511 1512 1513 1514 1515 1516 1517 1518 1519 1520 1521 1522 1523 1524 1525 1526 1527 1528 1529 1530
static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
			struct splice_desc *sd)
{
	char *src;
	int ret;

	/*
	 * See if we can use the atomic maps, by prefaulting in the
	 * pages and doing an atomic copy
	 */
	if (!fault_in_pages_writeable(sd->u.userptr, sd->len)) {
		src = buf->ops->map(pipe, buf, 1);
		ret = __copy_to_user_inatomic(sd->u.userptr, src + buf->offset,
							sd->len);
		buf->ops->unmap(pipe, buf, src);
		if (!ret) {
			ret = sd->len;
			goto out;
		}
	}

	/*
	 * No dice, use slow non-atomic map and copy
 	 */
	src = buf->ops->map(pipe, buf, 0);

	ret = sd->len;
	if (copy_to_user(sd->u.userptr, src + buf->offset, sd->len))
		ret = -EFAULT;

1531
	buf->ops->unmap(pipe, buf, src);
1532 1533 1534 1535 1536 1537 1538 1539 1540 1541 1542 1543 1544 1545 1546 1547 1548 1549 1550
out:
	if (ret > 0)
		sd->u.userptr += ret;
	return ret;
}

/*
 * For lack of a better implementation, implement vmsplice() to userspace
 * as a simple copy of the pipes pages to the user iov.
 */
static long vmsplice_to_user(struct file *file, const struct iovec __user *iov,
			     unsigned long nr_segs, unsigned int flags)
{
	struct pipe_inode_info *pipe;
	struct splice_desc sd;
	ssize_t size;
	int error;
	long ret;

1551
	pipe = get_pipe_info(file);
1552 1553 1554
	if (!pipe)
		return -EBADF;

1555
	pipe_lock(pipe);
1556 1557 1558 1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577 1578 1579 1580 1581

	error = ret = 0;
	while (nr_segs) {
		void __user *base;
		size_t len;

		/*
		 * Get user address base and length for this iovec.
		 */
		error = get_user(base, &iov->iov_base);
		if (unlikely(error))
			break;
		error = get_user(len, &iov->iov_len);
		if (unlikely(error))
			break;

		/*
		 * Sanity check this iovec. 0 read succeeds.
		 */
		if (unlikely(!len))
			break;
		if (unlikely(!base)) {
			error = -EFAULT;
			break;
		}

1582 1583 1584 1585 1586
		if (unlikely(!access_ok(VERIFY_WRITE, base, len))) {
			error = -EFAULT;
			break;
		}

1587 1588 1589 1590 1591 1592 1593 1594 1595 1596 1597 1598 1599 1600 1601 1602 1603 1604 1605 1606 1607 1608 1609
		sd.len = 0;
		sd.total_len = len;
		sd.flags = flags;
		sd.u.userptr = base;
		sd.pos = 0;

		size = __splice_from_pipe(pipe, &sd, pipe_to_user);
		if (size < 0) {
			if (!ret)
				ret = size;

			break;
		}

		ret += size;

		if (size < len)
			break;

		nr_segs--;
		iov++;
	}

1610
	pipe_unlock(pipe);
1611 1612 1613 1614 1615 1616 1617

	if (!ret)
		ret = error;

	return ret;
}

1618 1619 1620 1621 1622
/*
 * 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.
 */
1623 1624
static long vmsplice_to_pipe(struct file *file, const struct iovec __user *iov,
			     unsigned long nr_segs, unsigned int flags)
1625
{
1626
	struct pipe_inode_info *pipe;
1627 1628
	struct page *pages[PIPE_DEF_BUFFERS];
	struct partial_page partial[PIPE_DEF_BUFFERS];
1629 1630 1631
	struct splice_pipe_desc spd = {
		.pages = pages,
		.partial = partial,
1632
		.nr_pages_max = PIPE_DEF_BUFFERS,
1633 1634
		.flags = flags,
		.ops = &user_page_pipe_buf_ops,
1635
		.spd_release = spd_release_page,
1636
	};
1637
	long ret;
1638

1639
	pipe = get_pipe_info(file);
1640
	if (!pipe)
1641 1642
		return -EBADF;

1643 1644 1645 1646
	if (splice_grow_spd(pipe, &spd))
		return -ENOMEM;

	spd.nr_pages = get_iovec_page_array(iov, nr_segs, spd.pages,
1647
					    spd.partial, false,
1648
					    spd.nr_pages_max);
1649
	if (spd.nr_pages <= 0)
1650 1651 1652
		ret = spd.nr_pages;
	else
		ret = splice_to_pipe(pipe, &spd);
1653

1654
	splice_shrink_spd(&spd);
1655
	return ret;
1656 1657
}

1658 1659 1660 1661 1662 1663 1664 1665 1666 1667 1668 1669 1670 1671 1672 1673
/*
 * 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().
 *
 */
1674 1675
SYSCALL_DEFINE4(vmsplice, int, fd, const struct iovec __user *, iov,
		unsigned long, nr_segs, unsigned int, flags)
1676
{
1677
	struct fd f;
1678 1679
	long error;

1680 1681 1682 1683 1684
	if (unlikely(nr_segs > UIO_MAXIOV))
		return -EINVAL;
	else if (unlikely(!nr_segs))
		return 0;

1685
	error = -EBADF;
1686 1687 1688 1689 1690 1691 1692 1693
	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);
1694 1695 1696 1697 1698
	}

	return error;
}

1699 1700 1701 1702 1703 1704 1705 1706 1707 1708 1709 1710 1711 1712 1713 1714 1715 1716 1717 1718 1719
#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

1720 1721 1722
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)
1723
{
1724
	struct fd in, out;
1725 1726 1727 1728 1729 1730
	long error;

	if (unlikely(!len))
		return 0;

	error = -EBADF;
1731 1732 1733 1734 1735 1736 1737 1738
	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,
1739
							  len, flags);
1740
				fdput(out);
1741 1742
			}
		}
1743
		fdput(in);
1744 1745 1746
	}
	return error;
}
1747

1748 1749 1750 1751
/*
 * Make sure there's data to read. Wait for input if we can, otherwise
 * return an appropriate error.
 */
1752
static int ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1753 1754 1755 1756 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.
	 */
	if (pipe->nrbufs)
		return 0;

	ret = 0;
1764
	pipe_lock(pipe);
1765 1766 1767 1768 1769 1770 1771 1772 1773 1774 1775 1776 1777 1778 1779 1780 1781

	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);
	}

1782
	pipe_unlock(pipe);
1783 1784 1785 1786 1787 1788 1789
	return ret;
}

/*
 * Make sure there's writeable room. Wait for room if we can, otherwise
 * return an appropriate error.
 */
1790
static int opipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1791 1792 1793 1794 1795 1796 1797
{
	int ret;

	/*
	 * Check ->nrbufs without the inode lock first. This function
	 * is speculative anyways, so missing one is ok.
	 */
1798
	if (pipe->nrbufs < pipe->buffers)
1799 1800 1801
		return 0;

	ret = 0;
1802
	pipe_lock(pipe);
1803

1804
	while (pipe->nrbufs >= pipe->buffers) {
1805 1806 1807 1808 1809 1810 1811 1812 1813 1814 1815 1816 1817 1818 1819 1820 1821 1822
		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--;
	}

1823
	pipe_unlock(pipe);
1824 1825 1826
	return ret;
}

1827 1828 1829 1830 1831 1832 1833 1834 1835 1836 1837 1838 1839 1840 1841 1842 1843 1844 1845 1846 1847 1848 1849 1850 1851 1852 1853 1854 1855 1856 1857 1858 1859 1860 1861 1862 1863 1864 1865 1866 1867 1868 1869
/*
 * 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.
		 */
1870
		if (!ipipe->nrbufs || opipe->nrbufs >= opipe->buffers) {
1871 1872 1873 1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 1884 1885 1886 1887 1888 1889 1890
			/* 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;
1891
		nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1);
1892 1893 1894 1895 1896 1897 1898 1899 1900
		obuf = opipe->bufs + nbuf;

		if (len >= ibuf->len) {
			/*
			 * Simply move the whole buffer from ipipe to opipe
			 */
			*obuf = *ibuf;
			ibuf->ops = NULL;
			opipe->nrbufs++;
1901
			ipipe->curbuf = (ipipe->curbuf + 1) & (ipipe->buffers - 1);
1902 1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913 1914 1915 1916 1917 1918 1919 1920 1921 1922 1923 1924 1925 1926 1927 1928 1929 1930 1931 1932
			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
1933 1934 1935
	if (ret > 0)
		wakeup_pipe_readers(opipe);

1936 1937 1938 1939 1940 1941
	if (input_wakeup)
		wakeup_pipe_writers(ipipe);

	return ret;
}

1942 1943 1944 1945 1946 1947 1948 1949
/*
 * 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;
1950
	int ret = 0, i = 0, nbuf;
1951 1952 1953

	/*
	 * Potential ABBA deadlock, work around it by ordering lock
1954
	 * grabbing by pipe info address. Otherwise two different processes
1955 1956
	 * could deadlock (one doing tee from A -> B, the other from B -> A).
	 */
1957
	pipe_double_lock(ipipe, opipe);
1958

1959
	do {
1960 1961 1962 1963 1964 1965 1966
		if (!opipe->readers) {
			send_sig(SIGPIPE, current, 0);
			if (!ret)
				ret = -EPIPE;
			break;
		}

1967 1968 1969 1970
		/*
		 * If we have iterated all input buffers or ran out of
		 * output room, break.
		 */
1971
		if (i >= ipipe->nrbufs || opipe->nrbufs >= opipe->buffers)
1972
			break;
1973

1974 1975
		ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (ipipe->buffers-1));
		nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1);
1976 1977

		/*
1978 1979
		 * Get a reference to this pipe buffer,
		 * so we can copy the contents over.
1980
		 */
1981 1982 1983 1984 1985
		ibuf->ops->get(ipipe, ibuf);

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

1986
		/*
1987 1988
		 * Don't inherit the gift flag, we need to
		 * prevent multiple steals of this page.
1989
		 */
1990
		obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1991

1992 1993
		if (obuf->len > len)
			obuf->len = len;
1994

1995 1996 1997 1998 1999
		opipe->nrbufs++;
		ret += obuf->len;
		len -= obuf->len;
		i++;
	} while (len);
2000

2001 2002 2003 2004 2005 2006 2007
	/*
	 * 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;

2008 2009
	pipe_unlock(ipipe);
	pipe_unlock(opipe);
2010

2011 2012 2013
	/*
	 * If we put data in the output pipe, wakeup any potential readers.
	 */
N
Namhyung Kim 已提交
2014 2015
	if (ret > 0)
		wakeup_pipe_readers(opipe);
2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028

	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)
{
2029 2030
	struct pipe_inode_info *ipipe = get_pipe_info(in);
	struct pipe_inode_info *opipe = get_pipe_info(out);
2031
	int ret = -EINVAL;
2032 2033

	/*
2034 2035
	 * Duplicate the contents of ipipe to opipe without actually
	 * copying the data.
2036
	 */
2037 2038 2039 2040 2041
	if (ipipe && opipe && ipipe != opipe) {
		/*
		 * Keep going, unless we encounter an error. The ipipe/opipe
		 * ordering doesn't really matter.
		 */
2042
		ret = ipipe_prep(ipipe, flags);
2043
		if (!ret) {
2044
			ret = opipe_prep(opipe, flags);
2045
			if (!ret)
2046 2047 2048
				ret = link_pipe(ipipe, opipe, len, flags);
		}
	}
2049

2050
	return ret;
2051 2052
}

2053
SYSCALL_DEFINE4(tee, int, fdin, int, fdout, size_t, len, unsigned int, flags)
2054
{
2055 2056
	struct fd in;
	int error;
2057 2058 2059 2060 2061

	if (unlikely(!len))
		return 0;

	error = -EBADF;
2062 2063 2064 2065 2066 2067 2068 2069 2070
	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);
2071 2072
			}
		}
2073
 		fdput(in);
2074 2075 2076 2077
 	}

	return error;
}