splice.c 39.5 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/mm_inline.h>
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#include <linux/swap.h>
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#include <linux/writeback.h>
#include <linux/buffer_head.h>
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#include <linux/module.h>
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#include <linux/syscalls.h>
30
#include <linux/uio.h>
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#include <linux/security.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;
43
	struct address_space *mapping;
44

45 46
	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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61
		if (PagePrivate(page))
62
			try_to_release_page(page, GFP_KERNEL);
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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.
	 */
	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.
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		 */
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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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static 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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/**
 * 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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	if (pipe->inode)
		mutex_lock(&pipe->inode->i_mutex);
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	for (;;) {
186
		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->inode)
				do_wakeup = 1;
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212
			if (!--spd->nr_pages)
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				break;
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			if (pipe->nrbufs < PIPE_BUFFERS)
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				continue;

			break;
		}

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		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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	}

245
	if (pipe->inode) {
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		mutex_unlock(&pipe->inode->i_mutex);
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		if (do_wakeup) {
			smp_mb();
			if (waitqueue_active(&pipe->wait))
				wake_up_interruptible(&pipe->wait);
			kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
		}
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	}

256
	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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static void spd_release_page(struct splice_pipe_desc *spd, unsigned int i)
{
	page_cache_release(spd->pages[i]);
}

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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_BUFFERS];
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	struct partial_page partial[PIPE_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,
		.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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	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;
	nr_pages = min(req_pages, (unsigned)PIPE_BUFFERS);
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	/*
	 * Lookup the (hopefully) full range of pages we need.
	 */
	spd.nr_pages = find_get_pages_contig(mapping, index, nr_pages, 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.
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	 */
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	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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307
	error = 0;
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	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.
312
		 */
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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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		}

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		pages[spd.nr_pages++] = page;
		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);
		page = pages[page_nr];

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		if (PageReadahead(page))
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			page_cache_async_readahead(mapping, &in->f_ra, in,
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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)) {
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			/*
			 * If in nonblock mode then dont block on waiting
			 * for an in-flight io page
			 */
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			if (flags & SPLICE_F_NONBLOCK) {
				if (TestSetPageLocked(page))
					break;
			} else
				lock_page(page);
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			/*
			 * page was truncated, stop here. if this isn't the
			 * first page, we'll just complete what we already
			 * added
			 */
			if (!page->mapping) {
				unlock_page(page);
				break;
			}
			/*
			 * 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);
399
			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.
				 */
406
				if (error == AOP_TRUNCATED_PAGE)
407 408
					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;
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			/*
429
			 * max good bytes in this page
430
			 */
431 432
			plen = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
			if (plen <= loff)
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				break;

			/*
436
			 * force quit after adding this page
437
			 */
438 439
			this_len = min(this_len, plen - loff);
			len = this_len;
440
		}
441

442 443
		partial[page_nr].offset = loff;
		partial[page_nr].len = this_len;
444
		len -= this_len;
445
		loff = 0;
446 447
		spd.nr_pages++;
		index++;
448 449
	}

450
	/*
451
	 * Release any pages at the end, if we quit early. 'page_nr' is how far
452 453 454 455
	 * we got, 'nr_pages' is how many pages are in the map.
	 */
	while (page_nr < nr_pages)
		page_cache_release(pages[page_nr++]);
456
	in->f_ra.prev_pos = (loff_t)index << PAGE_CACHE_SHIFT;
457

458
	if (spd.nr_pages)
459
		return splice_to_pipe(pipe, &spd);
460

461
	return error;
462 463
}

464 465 466
/**
 * generic_file_splice_read - splice data from file to a pipe
 * @in:		file to splice from
467
 * @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.
 *
477
 */
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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)
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{
	ssize_t spliced;
	int ret;
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	loff_t isize, left;

	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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	ret = 0;
	spliced = 0;
496
	while (len && !spliced) {
497
		ret = __generic_file_splice_read(in, ppos, pipe, len, flags);
498

499
		if (ret < 0)
500
			break;
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		else if (!ret) {
			if (spliced)
				break;
			if (flags & SPLICE_F_NONBLOCK) {
				ret = -EAGAIN;
				break;
			}
		}
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510
		*ppos += ret;
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		len -= ret;
		spliced += ret;
	}

	if (spliced)
		return spliced;

	return ret;
}

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EXPORT_SYMBOL(generic_file_splice_read);

523
/*
524
 * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
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 * using sendpage(). Return the number of bytes sent.
526
 */
527
static int pipe_to_sendpage(struct pipe_inode_info *pipe,
528 529
			    struct pipe_buffer *buf, struct splice_desc *sd)
{
530
	struct file *file = sd->u.file;
531
	loff_t pos = sd->pos;
532
	int ret, more;
533

534
	ret = buf->ops->confirm(pipe, buf);
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	if (!ret) {
		more = (sd->flags & SPLICE_F_MORE) || sd->len < sd->total_len;
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		ret = file->f_op->sendpage(file, buf->page, buf->offset,
					   sd->len, &pos, more);
	}
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	return ret;
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}

/*
 * 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.
 *
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 * 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.
564
 */
565
static int pipe_to_file(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
566 567
			struct splice_desc *sd)
{
568
	struct file *file = sd->u.file;
569
	struct address_space *mapping = file->f_mapping;
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570
	unsigned int offset, this_len;
571
	struct page *page;
572
	void *fsdata;
573
	int ret;
574 575

	/*
576
	 * make sure the data in this buffer is uptodate
577
	 */
578
	ret = buf->ops->confirm(pipe, buf);
579 580
	if (unlikely(ret))
		return ret;
581 582 583

	offset = sd->pos & ~PAGE_CACHE_MASK;

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	this_len = sd->len;
	if (this_len + offset > PAGE_CACHE_SIZE)
		this_len = PAGE_CACHE_SIZE - offset;

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	ret = pagecache_write_begin(file, mapping, sd->pos, this_len,
				AOP_FLAG_UNINTERRUPTIBLE, &page, &fsdata);
	if (unlikely(ret))
		goto out;
592

593
	if (buf->page != page) {
594 595 596
		/*
		 * Careful, ->map() uses KM_USER0!
		 */
597
		char *src = buf->ops->map(pipe, buf, 1);
598
		char *dst = kmap_atomic(page, KM_USER1);
599

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		memcpy(dst + offset, src + buf->offset, this_len);
601
		flush_dcache_page(page);
602
		kunmap_atomic(dst, KM_USER1);
603
		buf->ops->unmap(pipe, buf, src);
604
	}
605 606
	ret = pagecache_write_end(file, mapping, sd->pos, this_len, this_len,
				page, fsdata);
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out:
	return ret;
}

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/**
 * __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.
 *
623
 */
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ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd,
			   splice_actor *actor)
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{
	int ret, do_wakeup, err;

	ret = 0;
	do_wakeup = 0;

	for (;;) {
633 634
		if (pipe->nrbufs) {
			struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
635
			const struct pipe_buf_operations *ops = buf->ops;
636

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			sd->len = buf->len;
			if (sd->len > sd->total_len)
				sd->len = sd->total_len;
640

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			err = actor(pipe, buf, sd);
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			if (err <= 0) {
643 644 645 646 647 648
				if (!ret && err != -ENODATA)
					ret = err;

				break;
			}

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			ret += err;
			buf->offset += err;
			buf->len -= err;

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			sd->len -= err;
			sd->pos += err;
			sd->total_len -= err;
			if (sd->len)
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				continue;
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659 660
			if (!buf->len) {
				buf->ops = NULL;
661
				ops->release(pipe, buf);
662 663 664 665
				pipe->curbuf = (pipe->curbuf + 1) & (PIPE_BUFFERS - 1);
				pipe->nrbufs--;
				if (pipe->inode)
					do_wakeup = 1;
666 667
			}

J
Jens Axboe 已提交
668
			if (!sd->total_len)
669 670 671
				break;
		}

672
		if (pipe->nrbufs)
673
			continue;
674
		if (!pipe->writers)
675
			break;
676
		if (!pipe->waiting_writers) {
677 678 679 680
			if (ret)
				break;
		}

J
Jens Axboe 已提交
681
		if (sd->flags & SPLICE_F_NONBLOCK) {
682 683 684 685 686
			if (!ret)
				ret = -EAGAIN;
			break;
		}

687 688 689 690 691 692 693
		if (signal_pending(current)) {
			if (!ret)
				ret = -ERESTARTSYS;
			break;
		}

		if (do_wakeup) {
694
			smp_mb();
695 696 697
			if (waitqueue_active(&pipe->wait))
				wake_up_interruptible_sync(&pipe->wait);
			kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
698 699 700
			do_wakeup = 0;
		}

701
		pipe_wait(pipe);
702 703 704
	}

	if (do_wakeup) {
705
		smp_mb();
706 707 708
		if (waitqueue_active(&pipe->wait))
			wake_up_interruptible(&pipe->wait);
		kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
709 710 711 712
	}

	return ret;
}
M
Mark Fasheh 已提交
713
EXPORT_SYMBOL(__splice_from_pipe);
714

715 716 717 718 719 720 721 722 723 724 725 726 727 728
/**
 * 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:
 *    See __splice_from_pipe. This function locks the input and output inodes,
 *    otherwise it's identical to __splice_from_pipe().
 *
 */
729 730 731 732 733 734
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;
	struct inode *inode = out->f_mapping->host;
J
Jens Axboe 已提交
735 736 737 738
	struct splice_desc sd = {
		.total_len = len,
		.flags = flags,
		.pos = *ppos,
739
		.u.file = out,
J
Jens Axboe 已提交
740
	};
741 742 743 744 745 746 747 748

	/*
	 * The actor worker might be calling ->prepare_write and
	 * ->commit_write. Most of the time, these expect i_mutex to
	 * be held. Since this may result in an ABBA deadlock with
	 * pipe->inode, we have to order lock acquiry here.
	 */
	inode_double_lock(inode, pipe->inode);
J
Jens Axboe 已提交
749
	ret = __splice_from_pipe(pipe, &sd, actor);
750 751 752 753 754 755 756 757 758
	inode_double_unlock(inode, pipe->inode);

	return ret;
}

/**
 * generic_file_splice_write_nolock - generic_file_splice_write without mutexes
 * @pipe:	pipe info
 * @out:	file to write to
759
 * @ppos:	position in @out
760 761 762
 * @len:	number of bytes to splice
 * @flags:	splice modifier flags
 *
763 764 765 766
 * Description:
 *    Will either move or copy pages (determined by @flags options) from
 *    the given pipe inode to the given file. The caller is responsible
 *    for acquiring i_mutex on both inodes.
767 768 769 770 771 772 773 774
 *
 */
ssize_t
generic_file_splice_write_nolock(struct pipe_inode_info *pipe, struct file *out,
				 loff_t *ppos, size_t len, unsigned int flags)
{
	struct address_space *mapping = out->f_mapping;
	struct inode *inode = mapping->host;
J
Jens Axboe 已提交
775 776 777 778
	struct splice_desc sd = {
		.total_len = len,
		.flags = flags,
		.pos = *ppos,
779
		.u.file = out,
J
Jens Axboe 已提交
780
	};
781 782 783
	ssize_t ret;
	int err;

784
	err = remove_suid(out->f_path.dentry);
785 786 787
	if (unlikely(err))
		return err;

J
Jens Axboe 已提交
788
	ret = __splice_from_pipe(pipe, &sd, pipe_to_file);
789
	if (ret > 0) {
790 791
		unsigned long nr_pages;

792
		*ppos += ret;
793
		nr_pages = (ret + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
794 795 796 797 798 799 800 801 802 803 804 805

		/*
		 * If file or inode is SYNC and we actually wrote some data,
		 * sync it.
		 */
		if (unlikely((out->f_flags & O_SYNC) || IS_SYNC(inode))) {
			err = generic_osync_inode(inode, mapping,
						  OSYNC_METADATA|OSYNC_DATA);

			if (err)
				ret = err;
		}
806
		balance_dirty_pages_ratelimited_nr(mapping, nr_pages);
807 808 809 810 811 812 813
	}

	return ret;
}

EXPORT_SYMBOL(generic_file_splice_write_nolock);

814 815
/**
 * generic_file_splice_write - splice data from a pipe to a file
816
 * @pipe:	pipe info
817
 * @out:	file to write to
818
 * @ppos:	position in @out
819 820 821
 * @len:	number of bytes to splice
 * @flags:	splice modifier flags
 *
822 823 824
 * Description:
 *    Will either move or copy pages (determined by @flags options) from
 *    the given pipe inode to the given file.
825 826
 *
 */
827 828
ssize_t
generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
829
			  loff_t *ppos, size_t len, unsigned int flags)
830
{
831
	struct address_space *mapping = out->f_mapping;
832
	struct inode *inode = mapping->host;
833
	int killsuid, killpriv;
834
	ssize_t ret;
835
	int err = 0;
836

837 838 839
	killpriv = security_inode_need_killpriv(out->f_path.dentry);
	killsuid = should_remove_suid(out->f_path.dentry);
	if (unlikely(killsuid || killpriv)) {
840
		mutex_lock(&inode->i_mutex);
841 842 843 844
		if (killpriv)
			err = security_inode_killpriv(out->f_path.dentry);
		if (!err && killsuid)
			err = __remove_suid(out->f_path.dentry, killsuid);
845 846 847 848
		mutex_unlock(&inode->i_mutex);
		if (err)
			return err;
	}
849

850
	ret = splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_file);
J
Jens Axboe 已提交
851
	if (ret > 0) {
852 853
		unsigned long nr_pages;

J
Jens Axboe 已提交
854
		*ppos += ret;
855
		nr_pages = (ret + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
J
Jens Axboe 已提交
856 857 858 859 860 861 862 863 864 865

		/*
		 * If file or inode is SYNC and we actually wrote some data,
		 * sync it.
		 */
		if (unlikely((out->f_flags & O_SYNC) || IS_SYNC(inode))) {
			mutex_lock(&inode->i_mutex);
			err = generic_osync_inode(inode, mapping,
						  OSYNC_METADATA|OSYNC_DATA);
			mutex_unlock(&inode->i_mutex);
866

J
Jens Axboe 已提交
867 868 869
			if (err)
				ret = err;
		}
870
		balance_dirty_pages_ratelimited_nr(mapping, nr_pages);
871 872 873
	}

	return ret;
874 875
}

876 877
EXPORT_SYMBOL(generic_file_splice_write);

878 879
/**
 * generic_splice_sendpage - splice data from a pipe to a socket
880
 * @pipe:	pipe to splice from
881
 * @out:	socket to write to
882
 * @ppos:	position in @out
883 884 885
 * @len:	number of bytes to splice
 * @flags:	splice modifier flags
 *
886 887 888
 * Description:
 *    Will send @len bytes from the pipe to a network socket. No data copying
 *    is involved.
889 890
 *
 */
891
ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
892
				loff_t *ppos, size_t len, unsigned int flags)
893
{
894
	return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
895 896
}

897
EXPORT_SYMBOL(generic_splice_sendpage);
J
Jeff Garzik 已提交
898

899 900 901
/*
 * Attempt to initiate a splice from pipe to file.
 */
902
static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
903
			   loff_t *ppos, size_t len, unsigned int flags)
904 905 906
{
	int ret;

907
	if (unlikely(!out->f_op || !out->f_op->splice_write))
908 909
		return -EINVAL;

910
	if (unlikely(!(out->f_mode & FMODE_WRITE)))
911 912
		return -EBADF;

913
	ret = rw_verify_area(WRITE, out, ppos, len);
914 915 916
	if (unlikely(ret < 0))
		return ret;

917
	return out->f_op->splice_write(pipe, out, ppos, len, flags);
918 919
}

920 921 922
/*
 * Attempt to initiate a splice from a file to a pipe.
 */
923 924 925
static long do_splice_to(struct file *in, loff_t *ppos,
			 struct pipe_inode_info *pipe, size_t len,
			 unsigned int flags)
926 927 928
{
	int ret;

929
	if (unlikely(!in->f_op || !in->f_op->splice_read))
930 931
		return -EINVAL;

932
	if (unlikely(!(in->f_mode & FMODE_READ)))
933 934
		return -EBADF;

935
	ret = rw_verify_area(READ, in, ppos, len);
936 937 938
	if (unlikely(ret < 0))
		return ret;

939
	return in->f_op->splice_read(in, ppos, pipe, len, flags);
940 941
}

942 943 944 945 946 947 948 949 950
/**
 * 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
951
 *    pipe is cached in the process, and reused during the lifetime of
952 953
 *    that process.
 *
J
Jens Axboe 已提交
954 955 956
 */
ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
			       splice_direct_actor *actor)
957 958 959 960
{
	struct pipe_inode_info *pipe;
	long ret, bytes;
	umode_t i_mode;
J
Jens Axboe 已提交
961 962
	size_t len;
	int i, flags;
963 964 965 966 967 968

	/*
	 * 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!
	 */
969
	i_mode = in->f_path.dentry->d_inode->i_mode;
970 971 972 973 974 975 976 977
	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;
978
	if (unlikely(!pipe)) {
979 980 981 982 983 984
		pipe = alloc_pipe_info(NULL);
		if (!pipe)
			return -ENOMEM;

		/*
		 * We don't have an immediate reader, but we'll read the stuff
985
		 * out of the pipe right after the splice_to_pipe(). So set
986 987 988 989 990 991 992 993
		 * PIPE_READERS appropriately.
		 */
		pipe->readers = 1;

		current->splice_pipe = pipe;
	}

	/*
I
Ingo Molnar 已提交
994
	 * Do the splice.
995 996 997
	 */
	ret = 0;
	bytes = 0;
J
Jens Axboe 已提交
998 999 1000 1001 1002 1003 1004
	len = sd->total_len;
	flags = sd->flags;

	/*
	 * Don't block on output, we have to drain the direct pipe.
	 */
	sd->flags &= ~SPLICE_F_NONBLOCK;
1005 1006

	while (len) {
1007
		size_t read_len;
1008
		loff_t pos = sd->pos;
1009

1010
		ret = do_splice_to(in, &pos, pipe, len, flags);
1011
		if (unlikely(ret <= 0))
1012 1013 1014
			goto out_release;

		read_len = ret;
J
Jens Axboe 已提交
1015
		sd->total_len = read_len;
1016 1017 1018 1019 1020 1021

		/*
		 * 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
1022
		ret = actor(pipe, sd);
1023
		if (unlikely(ret <= 0))
1024 1025 1026 1027
			goto out_release;

		bytes += ret;
		len -= ret;
1028
		sd->pos = pos;
1029

1030 1031
		if (ret < read_len)
			goto out_release;
1032 1033
	}

1034
done:
1035
	pipe->nrbufs = pipe->curbuf = 0;
1036
	file_accessed(in);
1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052
	return bytes;

out_release:
	/*
	 * If we did an incomplete transfer we must release
	 * the pipe buffers in question:
	 */
	for (i = 0; i < PIPE_BUFFERS; i++) {
		struct pipe_buffer *buf = pipe->bufs + i;

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

1053 1054
	if (!bytes)
		bytes = ret;
J
Jens Axboe 已提交
1055

1056
	goto done;
J
Jens Axboe 已提交
1057 1058 1059 1060 1061 1062
}
EXPORT_SYMBOL(splice_direct_to_actor);

static int direct_splice_actor(struct pipe_inode_info *pipe,
			       struct splice_desc *sd)
{
1063
	struct file *file = sd->u.file;
J
Jens Axboe 已提交
1064 1065 1066 1067

	return do_splice_from(pipe, file, &sd->pos, sd->total_len, sd->flags);
}

1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082
/**
 * 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
1083 1084 1085 1086 1087 1088 1089 1090
long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
		      size_t len, unsigned int flags)
{
	struct splice_desc sd = {
		.len		= len,
		.total_len	= len,
		.flags		= flags,
		.pos		= *ppos,
1091
		.u.file		= out,
J
Jens Axboe 已提交
1092
	};
1093
	long ret;
J
Jens Axboe 已提交
1094 1095

	ret = splice_direct_to_actor(in, &sd, direct_splice_actor);
1096 1097 1098
	if (ret > 0)
		*ppos += ret;

J
Jens Axboe 已提交
1099
	return ret;
1100 1101
}

1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114
/*
 * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
 * location, so checking ->i_pipe is not enough to verify that this is a
 * pipe.
 */
static inline struct pipe_inode_info *pipe_info(struct inode *inode)
{
	if (S_ISFIFO(inode->i_mode))
		return inode->i_pipe;

	return NULL;
}

1115 1116 1117
/*
 * Determine where to splice to/from.
 */
1118 1119 1120
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)
1121
{
1122
	struct pipe_inode_info *pipe;
1123
	loff_t offset, *off;
J
Jens Axboe 已提交
1124
	long ret;
1125

1126
	pipe = pipe_info(in->f_path.dentry->d_inode);
1127 1128 1129
	if (pipe) {
		if (off_in)
			return -ESPIPE;
1130 1131 1132
		if (off_out) {
			if (out->f_op->llseek == no_llseek)
				return -EINVAL;
1133
			if (copy_from_user(&offset, off_out, sizeof(loff_t)))
1134
				return -EFAULT;
1135 1136 1137
			off = &offset;
		} else
			off = &out->f_pos;
1138

J
Jens Axboe 已提交
1139 1140 1141 1142 1143 1144
		ret = do_splice_from(pipe, out, off, len, flags);

		if (off_out && copy_to_user(off_out, off, sizeof(loff_t)))
			ret = -EFAULT;

		return ret;
1145
	}
1146

1147
	pipe = pipe_info(out->f_path.dentry->d_inode);
1148 1149 1150
	if (pipe) {
		if (off_out)
			return -ESPIPE;
1151 1152 1153
		if (off_in) {
			if (in->f_op->llseek == no_llseek)
				return -EINVAL;
1154
			if (copy_from_user(&offset, off_in, sizeof(loff_t)))
1155
				return -EFAULT;
1156 1157 1158
			off = &offset;
		} else
			off = &in->f_pos;
1159

J
Jens Axboe 已提交
1160 1161 1162 1163 1164 1165
		ret = do_splice_to(in, off, pipe, len, flags);

		if (off_in && copy_to_user(off_in, off, sizeof(loff_t)))
			ret = -EFAULT;

		return ret;
1166
	}
1167 1168 1169 1170

	return -EINVAL;
}

1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197
/*
 * Do a copy-from-user while holding the mmap_semaphore for reading, in a
 * manner safe from deadlocking with simultaneous mmap() (grabbing mmap_sem
 * for writing) and page faulting on the user memory pointed to by src.
 * This assumes that we will very rarely hit the partial != 0 path, or this
 * will not be a win.
 */
static int copy_from_user_mmap_sem(void *dst, const void __user *src, size_t n)
{
	int partial;

	pagefault_disable();
	partial = __copy_from_user_inatomic(dst, src, n);
	pagefault_enable();

	/*
	 * Didn't copy everything, drop the mmap_sem and do a faulting copy
	 */
	if (unlikely(partial)) {
		up_read(&current->mm->mmap_sem);
		partial = copy_from_user(dst, src, n);
		down_read(&current->mm->mmap_sem);
	}

	return partial;
}

1198 1199 1200 1201 1202 1203 1204 1205 1206
/*
 * 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,
1207
				struct partial_page *partial, int aligned)
1208 1209 1210 1211 1212 1213 1214
{
	int buffers = 0, error = 0;

	down_read(&current->mm->mmap_sem);

	while (nr_vecs) {
		unsigned long off, npages;
1215
		struct iovec entry;
1216 1217 1218 1219
		void __user *base;
		size_t len;
		int i;

1220 1221
		error = -EFAULT;
		if (copy_from_user_mmap_sem(&entry, iov, sizeof(entry)))
1222 1223
			break;

1224 1225 1226
		base = entry.iov_base;
		len = entry.iov_len;

1227 1228 1229
		/*
		 * Sanity check this iovec. 0 read succeeds.
		 */
1230
		error = 0;
1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241
		if (unlikely(!len))
			break;
		error = -EFAULT;
		if (unlikely(!base))
			break;

		/*
		 * Get this base offset and number of pages, then map
		 * in the user pages.
		 */
		off = (unsigned long) base & ~PAGE_MASK;
1242 1243 1244 1245 1246 1247 1248 1249 1250

		/*
		 * 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;

1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265
		npages = (off + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
		if (npages > PIPE_BUFFERS - buffers)
			npages = PIPE_BUFFERS - buffers;

		error = get_user_pages(current, current->mm,
				       (unsigned long) base, npages, 0, 0,
				       &pages[buffers], NULL);

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

		/*
		 * Fill this contiguous range into the partial page map.
		 */
		for (i = 0; i < error; i++) {
1266
			const int plen = min_t(size_t, len, PAGE_SIZE - off);
1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303

			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.
		 */
		if (error < npages || buffers == PIPE_BUFFERS)
			break;

		nr_vecs--;
		iov++;
	}

	up_read(&current->mm->mmap_sem);

	if (buffers)
		return buffers;

	return error;
}

1304 1305 1306 1307 1308 1309
static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
			struct splice_desc *sd)
{
	char *src;
	int ret;

1310
	ret = buf->ops->confirm(pipe, buf);
1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337
	if (unlikely(ret))
		return 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;

1338
	buf->ops->unmap(pipe, buf, src);
1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385 1386 1387 1388 1389 1390 1391 1392 1393 1394 1395 1396 1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420 1421
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;

	pipe = pipe_info(file->f_path.dentry->d_inode);
	if (!pipe)
		return -EBADF;

	if (pipe->inode)
		mutex_lock(&pipe->inode->i_mutex);

	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;
		}

		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++;
	}

	if (pipe->inode)
		mutex_unlock(&pipe->inode->i_mutex);

	if (!ret)
		ret = error;

	return ret;
}

1422 1423 1424 1425 1426
/*
 * 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.
 */
1427 1428
static long vmsplice_to_pipe(struct file *file, const struct iovec __user *iov,
			     unsigned long nr_segs, unsigned int flags)
1429
{
1430
	struct pipe_inode_info *pipe;
1431 1432 1433 1434 1435 1436 1437
	struct page *pages[PIPE_BUFFERS];
	struct partial_page partial[PIPE_BUFFERS];
	struct splice_pipe_desc spd = {
		.pages = pages,
		.partial = partial,
		.flags = flags,
		.ops = &user_page_pipe_buf_ops,
1438
		.spd_release = spd_release_page,
1439 1440
	};

1441
	pipe = pipe_info(file->f_path.dentry->d_inode);
1442
	if (!pipe)
1443 1444
		return -EBADF;

1445 1446
	spd.nr_pages = get_iovec_page_array(iov, nr_segs, pages, partial,
					    flags & SPLICE_F_GIFT);
1447 1448 1449
	if (spd.nr_pages <= 0)
		return spd.nr_pages;

1450
	return splice_to_pipe(pipe, &spd);
1451 1452
}

1453 1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467 1468
/*
 * 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().
 *
 */
1469 1470 1471 1472 1473 1474 1475
asmlinkage long sys_vmsplice(int fd, const struct iovec __user *iov,
			     unsigned long nr_segs, unsigned int flags)
{
	struct file *file;
	long error;
	int fput;

1476 1477 1478 1479 1480
	if (unlikely(nr_segs > UIO_MAXIOV))
		return -EINVAL;
	else if (unlikely(!nr_segs))
		return 0;

1481 1482 1483 1484
	error = -EBADF;
	file = fget_light(fd, &fput);
	if (file) {
		if (file->f_mode & FMODE_WRITE)
1485 1486 1487
			error = vmsplice_to_pipe(file, iov, nr_segs, flags);
		else if (file->f_mode & FMODE_READ)
			error = vmsplice_to_user(file, iov, nr_segs, flags);
1488 1489 1490 1491 1492 1493 1494

		fput_light(file, fput);
	}

	return error;
}

1495 1496 1497
asmlinkage long sys_splice(int fd_in, loff_t __user *off_in,
			   int fd_out, loff_t __user *off_out,
			   size_t len, unsigned int flags)
1498 1499 1500 1501 1502 1503 1504 1505 1506
{
	long error;
	struct file *in, *out;
	int fput_in, fput_out;

	if (unlikely(!len))
		return 0;

	error = -EBADF;
1507
	in = fget_light(fd_in, &fput_in);
1508 1509
	if (in) {
		if (in->f_mode & FMODE_READ) {
1510
			out = fget_light(fd_out, &fput_out);
1511 1512
			if (out) {
				if (out->f_mode & FMODE_WRITE)
1513 1514 1515
					error = do_splice(in, off_in,
							  out, off_out,
							  len, flags);
1516 1517 1518 1519 1520 1521 1522 1523 1524
				fput_light(out, fput_out);
			}
		}

		fput_light(in, fput_in);
	}

	return error;
}
1525

1526 1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 1538 1539 1540 1541 1542 1543 1544 1545 1546 1547 1548 1549 1550 1551 1552 1553 1554 1555 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 1582 1583 1584 1585 1586 1587 1588 1589 1590 1591 1592 1593 1594 1595 1596 1597 1598 1599 1600 1601 1602 1603 1604
/*
 * Make sure there's data to read. Wait for input if we can, otherwise
 * return an appropriate error.
 */
static int link_ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
{
	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;
	mutex_lock(&pipe->inode->i_mutex);

	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);
	}

	mutex_unlock(&pipe->inode->i_mutex);
	return ret;
}

/*
 * Make sure there's writeable room. Wait for room if we can, otherwise
 * return an appropriate error.
 */
static int link_opipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
{
	int ret;

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

	ret = 0;
	mutex_lock(&pipe->inode->i_mutex);

	while (pipe->nrbufs >= PIPE_BUFFERS) {
		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--;
	}

	mutex_unlock(&pipe->inode->i_mutex);
	return ret;
}

1605 1606 1607 1608 1609 1610 1611 1612
/*
 * 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;
1613
	int ret = 0, i = 0, nbuf;
1614 1615 1616 1617 1618 1619

	/*
	 * Potential ABBA deadlock, work around it by ordering lock
	 * grabbing by inode address. Otherwise two different processes
	 * could deadlock (one doing tee from A -> B, the other from B -> A).
	 */
1620
	inode_double_lock(ipipe->inode, opipe->inode);
1621

1622
	do {
1623 1624 1625 1626 1627 1628 1629
		if (!opipe->readers) {
			send_sig(SIGPIPE, current, 0);
			if (!ret)
				ret = -EPIPE;
			break;
		}

1630 1631 1632 1633 1634 1635
		/*
		 * If we have iterated all input buffers or ran out of
		 * output room, break.
		 */
		if (i >= ipipe->nrbufs || opipe->nrbufs >= PIPE_BUFFERS)
			break;
1636

1637 1638
		ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (PIPE_BUFFERS - 1));
		nbuf = (opipe->curbuf + opipe->nrbufs) & (PIPE_BUFFERS - 1);
1639 1640

		/*
1641 1642
		 * Get a reference to this pipe buffer,
		 * so we can copy the contents over.
1643
		 */
1644 1645 1646 1647 1648
		ibuf->ops->get(ipipe, ibuf);

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

1649
		/*
1650 1651
		 * Don't inherit the gift flag, we need to
		 * prevent multiple steals of this page.
1652
		 */
1653
		obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1654

1655 1656
		if (obuf->len > len)
			obuf->len = len;
1657

1658 1659 1660 1661 1662
		opipe->nrbufs++;
		ret += obuf->len;
		len -= obuf->len;
		i++;
	} while (len);
1663

1664
	inode_double_unlock(ipipe->inode, opipe->inode);
1665

1666 1667 1668 1669
	/*
	 * If we put data in the output pipe, wakeup any potential readers.
	 */
	if (ret > 0) {
1670 1671 1672 1673 1674 1675 1676 1677 1678 1679 1680 1681 1682 1683 1684 1685 1686 1687
		smp_mb();
		if (waitqueue_active(&opipe->wait))
			wake_up_interruptible(&opipe->wait);
		kill_fasync(&opipe->fasync_readers, SIGIO, POLL_IN);
	}

	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)
{
1688 1689
	struct pipe_inode_info *ipipe = pipe_info(in->f_path.dentry->d_inode);
	struct pipe_inode_info *opipe = pipe_info(out->f_path.dentry->d_inode);
1690
	int ret = -EINVAL;
1691 1692

	/*
1693 1694
	 * Duplicate the contents of ipipe to opipe without actually
	 * copying the data.
1695
	 */
1696 1697 1698 1699 1700 1701 1702 1703 1704 1705 1706 1707 1708 1709 1710
	if (ipipe && opipe && ipipe != opipe) {
		/*
		 * Keep going, unless we encounter an error. The ipipe/opipe
		 * ordering doesn't really matter.
		 */
		ret = link_ipipe_prep(ipipe, flags);
		if (!ret) {
			ret = link_opipe_prep(opipe, flags);
			if (!ret) {
				ret = link_pipe(ipipe, opipe, len, flags);
				if (!ret && (flags & SPLICE_F_NONBLOCK))
					ret = -EAGAIN;
			}
		}
	}
1711

1712
	return ret;
1713 1714 1715 1716 1717 1718 1719 1720 1721 1722 1723 1724 1725 1726 1727 1728 1729 1730 1731 1732 1733 1734 1735 1736 1737 1738 1739 1740
}

asmlinkage long sys_tee(int fdin, int fdout, size_t len, unsigned int flags)
{
	struct file *in;
	int error, fput_in;

	if (unlikely(!len))
		return 0;

	error = -EBADF;
	in = fget_light(fdin, &fput_in);
	if (in) {
		if (in->f_mode & FMODE_READ) {
			int fput_out;
			struct file *out = fget_light(fdout, &fput_out);

			if (out) {
				if (out->f_mode & FMODE_WRITE)
					error = do_tee(in, out, len, flags);
				fput_light(out, fput_out);
			}
		}
 		fput_light(in, fput_in);
 	}

	return error;
}