splice.c 40.4 KB
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/*
 * "splice": joining two ropes together by interweaving their strands.
 *
 * This is the "extended pipe" functionality, where a pipe is used as
 * an arbitrary in-memory buffer. Think of a pipe as a small kernel
 * buffer that you can use to transfer data from one end to the other.
 *
 * The traditional unix read/write is extended with a "splice()" operation
 * that transfers data buffers to or from a pipe buffer.
 *
 * Named by Larry McVoy, original implementation from Linus, extended by
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 * Jens to support splicing to files, network, direct splicing, etc and
 * fixing lots of bugs.
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 *
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 * Copyright (C) 2005-2006 Jens Axboe <axboe@kernel.dk>
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 * Copyright (C) 2005-2006 Linus Torvalds <torvalds@osdl.org>
 * Copyright (C) 2006 Ingo Molnar <mingo@elte.hu>
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 *
 */
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/pagemap.h>
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#include <linux/splice.h>
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#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>
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#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;
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	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:
 *    @spd contains a map of pages and len/offset tupples, a long with
 *    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 (;;) {
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		if (!pipe->readers) {
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			send_sig(SIGPIPE, current, 0);
			if (!ret)
				ret = -EPIPE;
			break;
		}

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

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

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			if (pipe->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;
		}

220
		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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	}

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	while (page_nr < spd_pages)
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		page_cache_release(spd->pages[page_nr++]);
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	return ret;
}

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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;
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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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	index = *ppos >> PAGE_CACHE_SHIFT;
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	loff = *ppos & ~PAGE_CACHE_MASK;
	nr_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
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	if (nr_pages > PIPE_BUFFERS)
		nr_pages = PIPE_BUFFERS;

	/*
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	 * Don't try to 2nd guess the read-ahead logic, call into
	 * page_cache_readahead() like the page cache reads would do.
292
	 */
293
	page_cache_readahead(mapping, &in->f_ra, in, index, nr_pages);
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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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300 301
	/*
	 * If find_get_pages_contig() returned fewer pages than we needed,
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	 * allocate the rest and fill in the holes.
303
	 */
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	error = 0;
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	index += spd.nr_pages;
	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.
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		 */
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		page = find_get_page(mapping, index);
		if (!page) {
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			/*
			 * Make sure the read-ahead engine is notified
			 * about this failure.
			 */
			handle_ra_miss(mapping, &in->f_ra, index);

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			/*
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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 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);
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			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;

409 410
				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;
427 428

			/*
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
452 453 454 455 456
	 * we got, 'nr_pages' is how many pages are in the map.
	 */
	while (page_nr < nr_pages)
		page_cache_release(pages[page_nr++]);

457
	if (spd.nr_pages)
458
		return splice_to_pipe(pipe, &spd);
459

460
	return error;
461 462
}

463 464 465
/**
 * generic_file_splice_read - splice data from file to a pipe
 * @in:		file to splice from
466
 * @ppos:	position in @in
467 468 469 470
 * @pipe:	pipe to splice to
 * @len:	number of bytes to splice
 * @flags:	splice modifier flags
 *
471 472 473 474 475
 * 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.
 *
476
 */
477 478 479
ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
				 struct pipe_inode_info *pipe, size_t len,
				 unsigned int flags)
480 481 482
{
	ssize_t spliced;
	int ret;
483 484 485 486 487 488 489 490 491
	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;
492 493 494 495

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

498
		if (ret < 0)
499
			break;
500 501 502 503 504 505 506 507
		else if (!ret) {
			if (spliced)
				break;
			if (flags & SPLICE_F_NONBLOCK) {
				ret = -EAGAIN;
				break;
			}
		}
508

509
		*ppos += ret;
510 511 512 513 514 515 516 517 518 519
		len -= ret;
		spliced += ret;
	}

	if (spliced)
		return spliced;

	return ret;
}

520 521
EXPORT_SYMBOL(generic_file_splice_read);

522
/*
523
 * 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.
525
 */
526
static int pipe_to_sendpage(struct pipe_inode_info *pipe,
527 528
			    struct pipe_buffer *buf, struct splice_desc *sd)
{
529
	struct file *file = sd->u.file;
530
	loff_t pos = sd->pos;
531
	int ret, more;
532

533
	ret = buf->ops->confirm(pipe, buf);
534 535
	if (!ret) {
		more = (sd->flags & SPLICE_F_MORE) || sd->len < sd->total_len;
536

537 538 539
		ret = file->f_op->sendpage(file, buf->page, buf->offset,
					   sd->len, &pos, more);
	}
540

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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.
563
 */
564
static int pipe_to_file(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
565 566
			struct splice_desc *sd)
{
567
	struct file *file = sd->u.file;
568
	struct address_space *mapping = file->f_mapping;
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569
	unsigned int offset, this_len;
570 571
	struct page *page;
	pgoff_t index;
572
	int ret;
573 574

	/*
575
	 * make sure the data in this buffer is uptodate
576
	 */
577
	ret = buf->ops->confirm(pipe, buf);
578 579
	if (unlikely(ret))
		return ret;
580 581 582 583

	index = sd->pos >> PAGE_CACHE_SHIFT;
	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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find_page:
	page = find_lock_page(mapping, index);
	if (!page) {
		ret = -ENOMEM;
		page = page_cache_alloc_cold(mapping);
		if (unlikely(!page))
			goto out_ret;

596
		/*
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597
		 * This will also lock the page
598
		 */
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		ret = add_to_page_cache_lru(page, mapping, index,
					    GFP_KERNEL);
		if (unlikely(ret))
			goto out;
	}
604

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	ret = mapping->a_ops->prepare_write(file, page, offset, offset+this_len);
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	if (unlikely(ret)) {
		loff_t isize = i_size_read(mapping->host);

		if (ret != AOP_TRUNCATED_PAGE)
			unlock_page(page);
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		page_cache_release(page);
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		if (ret == AOP_TRUNCATED_PAGE)
			goto find_page;

		/*
		 * prepare_write() may have instantiated a few blocks
		 * outside i_size.  Trim these off again.
		 */
		if (sd->pos + this_len > isize)
			vmtruncate(mapping->host, isize);

622
		goto out_ret;
623
	}
624

625
	if (buf->page != page) {
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		/*
		 * Careful, ->map() uses KM_USER0!
		 */
629
		char *src = buf->ops->map(pipe, buf, 1);
630
		char *dst = kmap_atomic(page, KM_USER1);
631

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		memcpy(dst + offset, src + buf->offset, this_len);
633
		flush_dcache_page(page);
634
		kunmap_atomic(dst, KM_USER1);
635
		buf->ops->unmap(pipe, buf, src);
636
	}
637

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	ret = mapping->a_ops->commit_write(file, page, offset, offset+this_len);
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	if (ret) {
		if (ret == AOP_TRUNCATED_PAGE) {
			page_cache_release(page);
			goto find_page;
		}
		if (ret < 0)
			goto out;
646
		/*
647 648
		 * Partial write has happened, so 'ret' already initialized by
		 * number of bytes written, Where is nothing we have to do here.
649
		 */
650
	} else
651
		ret = this_len;
652 653 654 655 656
	/*
	 * Return the number of bytes written and mark page as
	 * accessed, we are now done!
	 */
	mark_page_accessed(page);
657
out:
658
	page_cache_release(page);
659
	unlock_page(page);
660
out_ret:
661 662 663
	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.
 *
676
 */
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ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd,
			   splice_actor *actor)
679 680 681 682 683 684 685
{
	int ret, do_wakeup, err;

	ret = 0;
	do_wakeup = 0;

	for (;;) {
686 687
		if (pipe->nrbufs) {
			struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
688
			const struct pipe_buf_operations *ops = buf->ops;
689

J
Jens Axboe 已提交
690 691 692
			sd->len = buf->len;
			if (sd->len > sd->total_len)
				sd->len = sd->total_len;
693

J
Jens Axboe 已提交
694
			err = actor(pipe, buf, sd);
J
Jens Axboe 已提交
695
			if (err <= 0) {
696 697 698 699 700 701
				if (!ret && err != -ENODATA)
					ret = err;

				break;
			}

J
Jens Axboe 已提交
702 703 704 705
			ret += err;
			buf->offset += err;
			buf->len -= err;

J
Jens Axboe 已提交
706 707 708 709
			sd->len -= err;
			sd->pos += err;
			sd->total_len -= err;
			if (sd->len)
J
Jens Axboe 已提交
710
				continue;
I
Ingo Molnar 已提交
711

712 713
			if (!buf->len) {
				buf->ops = NULL;
714
				ops->release(pipe, buf);
715 716 717 718
				pipe->curbuf = (pipe->curbuf + 1) & (PIPE_BUFFERS - 1);
				pipe->nrbufs--;
				if (pipe->inode)
					do_wakeup = 1;
719 720
			}

J
Jens Axboe 已提交
721
			if (!sd->total_len)
722 723 724
				break;
		}

725
		if (pipe->nrbufs)
726
			continue;
727
		if (!pipe->writers)
728
			break;
729
		if (!pipe->waiting_writers) {
730 731 732 733
			if (ret)
				break;
		}

J
Jens Axboe 已提交
734
		if (sd->flags & SPLICE_F_NONBLOCK) {
735 736 737 738 739
			if (!ret)
				ret = -EAGAIN;
			break;
		}

740 741 742 743 744 745 746
		if (signal_pending(current)) {
			if (!ret)
				ret = -ERESTARTSYS;
			break;
		}

		if (do_wakeup) {
747
			smp_mb();
748 749 750
			if (waitqueue_active(&pipe->wait))
				wake_up_interruptible_sync(&pipe->wait);
			kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
751 752 753
			do_wakeup = 0;
		}

754
		pipe_wait(pipe);
755 756 757
	}

	if (do_wakeup) {
758
		smp_mb();
759 760 761
		if (waitqueue_active(&pipe->wait))
			wake_up_interruptible(&pipe->wait);
		kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
762 763 764 765
	}

	return ret;
}
M
Mark Fasheh 已提交
766
EXPORT_SYMBOL(__splice_from_pipe);
767

768 769 770 771 772 773 774 775 776 777 778 779 780 781
/**
 * 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().
 *
 */
782 783 784 785 786 787
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
788 789 790 791
	struct splice_desc sd = {
		.total_len = len,
		.flags = flags,
		.pos = *ppos,
792
		.u.file = out,
J
Jens Axboe 已提交
793
	};
794 795 796 797 798 799 800 801

	/*
	 * 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
802
	ret = __splice_from_pipe(pipe, &sd, actor);
803 804 805 806 807 808 809 810 811
	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
812
 * @ppos:	position in @out
813 814 815
 * @len:	number of bytes to splice
 * @flags:	splice modifier flags
 *
816 817 818 819
 * 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.
820 821 822 823 824 825 826 827
 *
 */
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
828 829 830 831
	struct splice_desc sd = {
		.total_len = len,
		.flags = flags,
		.pos = *ppos,
832
		.u.file = out,
J
Jens Axboe 已提交
833
	};
834 835 836
	ssize_t ret;
	int err;

837
	err = remove_suid(out->f_path.dentry);
838 839 840
	if (unlikely(err))
		return err;

J
Jens Axboe 已提交
841
	ret = __splice_from_pipe(pipe, &sd, pipe_to_file);
842
	if (ret > 0) {
843 844
		unsigned long nr_pages;

845
		*ppos += ret;
846
		nr_pages = (ret + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
847 848 849 850 851 852 853 854 855 856 857 858

		/*
		 * 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;
		}
859
		balance_dirty_pages_ratelimited_nr(mapping, nr_pages);
860 861 862 863 864 865 866
	}

	return ret;
}

EXPORT_SYMBOL(generic_file_splice_write_nolock);

867 868
/**
 * generic_file_splice_write - splice data from a pipe to a file
869
 * @pipe:	pipe info
870
 * @out:	file to write to
871
 * @ppos:	position in @out
872 873 874
 * @len:	number of bytes to splice
 * @flags:	splice modifier flags
 *
875 876 877
 * Description:
 *    Will either move or copy pages (determined by @flags options) from
 *    the given pipe inode to the given file.
878 879
 *
 */
880 881
ssize_t
generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
882
			  loff_t *ppos, size_t len, unsigned int flags)
883
{
884
	struct address_space *mapping = out->f_mapping;
885
	struct inode *inode = mapping->host;
886
	ssize_t ret;
887 888
	int err;

889
	err = should_remove_suid(out->f_path.dentry);
890 891
	if (unlikely(err)) {
		mutex_lock(&inode->i_mutex);
892
		err = __remove_suid(out->f_path.dentry, err);
893 894 895 896
		mutex_unlock(&inode->i_mutex);
		if (err)
			return err;
	}
897

898
	ret = splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_file);
J
Jens Axboe 已提交
899
	if (ret > 0) {
900 901
		unsigned long nr_pages;

J
Jens Axboe 已提交
902
		*ppos += ret;
903
		nr_pages = (ret + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
J
Jens Axboe 已提交
904 905 906 907 908 909 910 911 912 913

		/*
		 * 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);
914

J
Jens Axboe 已提交
915 916 917
			if (err)
				ret = err;
		}
918
		balance_dirty_pages_ratelimited_nr(mapping, nr_pages);
919 920 921
	}

	return ret;
922 923
}

924 925
EXPORT_SYMBOL(generic_file_splice_write);

926 927
/**
 * generic_splice_sendpage - splice data from a pipe to a socket
928
 * @pipe:	pipe to splice from
929
 * @out:	socket to write to
930
 * @ppos:	position in @out
931 932 933
 * @len:	number of bytes to splice
 * @flags:	splice modifier flags
 *
934 935 936
 * Description:
 *    Will send @len bytes from the pipe to a network socket. No data copying
 *    is involved.
937 938
 *
 */
939
ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
940
				loff_t *ppos, size_t len, unsigned int flags)
941
{
942
	return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
943 944
}

945
EXPORT_SYMBOL(generic_splice_sendpage);
J
Jeff Garzik 已提交
946

947 948 949
/*
 * Attempt to initiate a splice from pipe to file.
 */
950
static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
951
			   loff_t *ppos, size_t len, unsigned int flags)
952 953 954
{
	int ret;

955
	if (unlikely(!out->f_op || !out->f_op->splice_write))
956 957
		return -EINVAL;

958
	if (unlikely(!(out->f_mode & FMODE_WRITE)))
959 960
		return -EBADF;

961
	ret = rw_verify_area(WRITE, out, ppos, len);
962 963 964
	if (unlikely(ret < 0))
		return ret;

965 966 967 968
	ret = security_file_permission(out, MAY_WRITE);
	if (unlikely(ret < 0))
		return ret;

969
	return out->f_op->splice_write(pipe, out, ppos, len, flags);
970 971
}

972 973 974
/*
 * Attempt to initiate a splice from a file to a pipe.
 */
975 976 977
static long do_splice_to(struct file *in, loff_t *ppos,
			 struct pipe_inode_info *pipe, size_t len,
			 unsigned int flags)
978 979 980
{
	int ret;

981
	if (unlikely(!in->f_op || !in->f_op->splice_read))
982 983
		return -EINVAL;

984
	if (unlikely(!(in->f_mode & FMODE_READ)))
985 986
		return -EBADF;

987
	ret = rw_verify_area(READ, in, ppos, len);
988 989 990
	if (unlikely(ret < 0))
		return ret;

991 992 993 994
	ret = security_file_permission(in, MAY_READ);
	if (unlikely(ret < 0))
		return ret;

995
	return in->f_op->splice_read(in, ppos, pipe, len, flags);
996 997
}

998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009
/**
 * 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
 *    pipe is cached in the process, and reused during the life time of
 *    that process.
 *
J
Jens Axboe 已提交
1010 1011 1012
 */
ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
			       splice_direct_actor *actor)
1013 1014 1015 1016
{
	struct pipe_inode_info *pipe;
	long ret, bytes;
	umode_t i_mode;
J
Jens Axboe 已提交
1017 1018
	size_t len;
	int i, flags;
1019 1020 1021 1022 1023 1024

	/*
	 * 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!
	 */
1025
	i_mode = in->f_path.dentry->d_inode->i_mode;
1026 1027 1028 1029 1030 1031 1032 1033
	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;
1034
	if (unlikely(!pipe)) {
1035 1036 1037 1038 1039 1040
		pipe = alloc_pipe_info(NULL);
		if (!pipe)
			return -ENOMEM;

		/*
		 * We don't have an immediate reader, but we'll read the stuff
1041
		 * out of the pipe right after the splice_to_pipe(). So set
1042 1043 1044 1045 1046 1047 1048 1049
		 * PIPE_READERS appropriately.
		 */
		pipe->readers = 1;

		current->splice_pipe = pipe;
	}

	/*
I
Ingo Molnar 已提交
1050
	 * Do the splice.
1051 1052 1053
	 */
	ret = 0;
	bytes = 0;
J
Jens Axboe 已提交
1054 1055 1056 1057 1058 1059 1060
	len = sd->total_len;
	flags = sd->flags;

	/*
	 * Don't block on output, we have to drain the direct pipe.
	 */
	sd->flags &= ~SPLICE_F_NONBLOCK;
1061 1062 1063 1064 1065 1066 1067 1068 1069

	while (len) {
		size_t read_len, max_read_len;

		/*
		 * Do at most PIPE_BUFFERS pages worth of transfer:
		 */
		max_read_len = min(len, (size_t)(PIPE_BUFFERS*PAGE_SIZE));

J
Jens Axboe 已提交
1070
		ret = do_splice_to(in, &sd->pos, pipe, max_read_len, flags);
1071 1072 1073 1074
		if (unlikely(ret < 0))
			goto out_release;

		read_len = ret;
J
Jens Axboe 已提交
1075
		sd->total_len = read_len;
1076 1077 1078 1079 1080 1081

		/*
		 * 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
1082
		ret = actor(pipe, sd);
1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126
		if (unlikely(ret < 0))
			goto out_release;

		bytes += ret;
		len -= ret;

		/*
		 * In nonblocking mode, if we got back a short read then
		 * that was due to either an IO error or due to the
		 * pagecache entry not being there. In the IO error case
		 * the _next_ splice attempt will produce a clean IO error
		 * return value (not a short read), so in both cases it's
		 * correct to break out of the loop here:
		 */
		if ((flags & SPLICE_F_NONBLOCK) && (read_len < max_read_len))
			break;
	}

	pipe->nrbufs = pipe->curbuf = 0;

	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;
		}
	}
	pipe->nrbufs = pipe->curbuf = 0;

	/*
	 * If we transferred some data, return the number of bytes:
	 */
	if (bytes > 0)
		return bytes;

	return ret;
J
Jens Axboe 已提交
1127 1128 1129 1130 1131 1132 1133

}
EXPORT_SYMBOL(splice_direct_to_actor);

static int direct_splice_actor(struct pipe_inode_info *pipe,
			       struct splice_desc *sd)
{
1134
	struct file *file = sd->u.file;
J
Jens Axboe 已提交
1135 1136 1137 1138

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

1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153
/**
 * 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
1154 1155 1156 1157 1158 1159 1160 1161
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,
1162
		.u.file		= out,
J
Jens Axboe 已提交
1163 1164 1165 1166 1167 1168
	};
	size_t ret;

	ret = splice_direct_to_actor(in, &sd, direct_splice_actor);
	*ppos = sd.pos;
	return ret;
1169 1170
}

1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183
/*
 * 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;
}

1184 1185 1186
/*
 * Determine where to splice to/from.
 */
1187 1188 1189
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)
1190
{
1191
	struct pipe_inode_info *pipe;
1192
	loff_t offset, *off;
J
Jens Axboe 已提交
1193
	long ret;
1194

1195
	pipe = pipe_info(in->f_path.dentry->d_inode);
1196 1197 1198
	if (pipe) {
		if (off_in)
			return -ESPIPE;
1199 1200 1201
		if (off_out) {
			if (out->f_op->llseek == no_llseek)
				return -EINVAL;
1202
			if (copy_from_user(&offset, off_out, sizeof(loff_t)))
1203
				return -EFAULT;
1204 1205 1206
			off = &offset;
		} else
			off = &out->f_pos;
1207

J
Jens Axboe 已提交
1208 1209 1210 1211 1212 1213
		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;
1214
	}
1215

1216
	pipe = pipe_info(out->f_path.dentry->d_inode);
1217 1218 1219
	if (pipe) {
		if (off_out)
			return -ESPIPE;
1220 1221 1222
		if (off_in) {
			if (in->f_op->llseek == no_llseek)
				return -EINVAL;
1223
			if (copy_from_user(&offset, off_in, sizeof(loff_t)))
1224
				return -EFAULT;
1225 1226 1227
			off = &offset;
		} else
			off = &in->f_pos;
1228

J
Jens Axboe 已提交
1229 1230 1231 1232 1233 1234
		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;
1235
	}
1236 1237 1238 1239

	return -EINVAL;
}

1240 1241 1242 1243 1244 1245 1246 1247 1248
/*
 * 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,
1249
				struct partial_page *partial, int aligned)
1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288
{
	int buffers = 0, error = 0;

	/*
	 * It's ok to take the mmap_sem for reading, even
	 * across a "get_user()".
	 */
	down_read(&current->mm->mmap_sem);

	while (nr_vecs) {
		unsigned long off, npages;
		void __user *base;
		size_t len;
		int i;

		/*
		 * 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;
		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;
1289 1290 1291 1292 1293 1294 1295 1296 1297

		/*
		 * 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;

1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312
		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++) {
1313
			const int plen = min_t(size_t, len, PAGE_SIZE - off);
1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350

			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;
}

1351 1352 1353 1354 1355 1356
static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
			struct splice_desc *sd)
{
	char *src;
	int ret;

1357
	ret = buf->ops->confirm(pipe, buf);
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 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467 1468
	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;

out:
	if (ret > 0)
		sd->u.userptr += ret;
	buf->ops->unmap(pipe, buf, src);
	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;
}

1469 1470 1471 1472 1473
/*
 * 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.
 */
1474 1475
static long vmsplice_to_pipe(struct file *file, const struct iovec __user *iov,
			     unsigned long nr_segs, unsigned int flags)
1476
{
1477
	struct pipe_inode_info *pipe;
1478 1479 1480 1481 1482 1483 1484 1485 1486
	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,
	};

1487
	pipe = pipe_info(file->f_path.dentry->d_inode);
1488
	if (!pipe)
1489 1490
		return -EBADF;

1491 1492
	spd.nr_pages = get_iovec_page_array(iov, nr_segs, pages, partial,
					    flags & SPLICE_F_GIFT);
1493 1494 1495
	if (spd.nr_pages <= 0)
		return spd.nr_pages;

1496
	return splice_to_pipe(pipe, &spd);
1497 1498
}

1499 1500 1501 1502 1503 1504 1505 1506 1507 1508 1509 1510 1511 1512 1513 1514
/*
 * 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().
 *
 */
1515 1516 1517 1518 1519 1520 1521
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;

1522 1523 1524 1525 1526
	if (unlikely(nr_segs > UIO_MAXIOV))
		return -EINVAL;
	else if (unlikely(!nr_segs))
		return 0;

1527 1528 1529 1530
	error = -EBADF;
	file = fget_light(fd, &fput);
	if (file) {
		if (file->f_mode & FMODE_WRITE)
1531 1532 1533
			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);
1534 1535 1536 1537 1538 1539 1540

		fput_light(file, fput);
	}

	return error;
}

1541 1542 1543
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)
1544 1545 1546 1547 1548 1549 1550 1551 1552
{
	long error;
	struct file *in, *out;
	int fput_in, fput_out;

	if (unlikely(!len))
		return 0;

	error = -EBADF;
1553
	in = fget_light(fd_in, &fput_in);
1554 1555
	if (in) {
		if (in->f_mode & FMODE_READ) {
1556
			out = fget_light(fd_out, &fput_out);
1557 1558
			if (out) {
				if (out->f_mode & FMODE_WRITE)
1559 1560 1561
					error = do_splice(in, off_in,
							  out, off_out,
							  len, flags);
1562 1563 1564 1565 1566 1567 1568 1569 1570
				fput_light(out, fput_out);
			}
		}

		fput_light(in, fput_in);
	}

	return error;
}
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 1605 1606 1607 1608 1609 1610 1611 1612 1613 1614 1615 1616 1617 1618 1619 1620 1621 1622 1623 1624 1625 1626 1627 1628 1629 1630 1631 1632 1633 1634 1635 1636 1637 1638 1639 1640 1641 1642 1643 1644 1645 1646 1647 1648 1649 1650
/*
 * 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;
}

1651 1652 1653 1654 1655 1656 1657 1658
/*
 * 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;
1659
	int ret = 0, i = 0, nbuf;
1660 1661 1662 1663 1664 1665

	/*
	 * 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).
	 */
1666
	inode_double_lock(ipipe->inode, opipe->inode);
1667

1668
	do {
1669 1670 1671 1672 1673 1674 1675
		if (!opipe->readers) {
			send_sig(SIGPIPE, current, 0);
			if (!ret)
				ret = -EPIPE;
			break;
		}

1676 1677 1678 1679 1680 1681
		/*
		 * If we have iterated all input buffers or ran out of
		 * output room, break.
		 */
		if (i >= ipipe->nrbufs || opipe->nrbufs >= PIPE_BUFFERS)
			break;
1682

1683 1684
		ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (PIPE_BUFFERS - 1));
		nbuf = (opipe->curbuf + opipe->nrbufs) & (PIPE_BUFFERS - 1);
1685 1686

		/*
1687 1688
		 * Get a reference to this pipe buffer,
		 * so we can copy the contents over.
1689
		 */
1690 1691 1692 1693 1694
		ibuf->ops->get(ipipe, ibuf);

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

1695
		/*
1696 1697
		 * Don't inherit the gift flag, we need to
		 * prevent multiple steals of this page.
1698
		 */
1699
		obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1700

1701 1702
		if (obuf->len > len)
			obuf->len = len;
1703

1704 1705 1706 1707 1708
		opipe->nrbufs++;
		ret += obuf->len;
		len -= obuf->len;
		i++;
	} while (len);
1709

1710
	inode_double_unlock(ipipe->inode, opipe->inode);
1711

1712 1713 1714 1715
	/*
	 * If we put data in the output pipe, wakeup any potential readers.
	 */
	if (ret > 0) {
1716 1717 1718 1719 1720 1721 1722 1723 1724 1725 1726 1727 1728 1729 1730 1731 1732 1733
		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)
{
1734 1735
	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);
1736
	int ret = -EINVAL;
1737 1738

	/*
1739 1740
	 * Duplicate the contents of ipipe to opipe without actually
	 * copying the data.
1741
	 */
1742 1743 1744 1745 1746 1747 1748 1749 1750 1751 1752 1753 1754 1755 1756
	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;
			}
		}
	}
1757

1758
	return ret;
1759 1760 1761 1762 1763 1764 1765 1766 1767 1768 1769 1770 1771 1772 1773 1774 1775 1776 1777 1778 1779 1780 1781 1782 1783 1784 1785 1786
}

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;
}