splice.c 40.1 KB
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/*
 * "splice": joining two ropes together by interweaving their strands.
 *
 * This is the "extended pipe" functionality, where a pipe is used as
 * an arbitrary in-memory buffer. Think of a pipe as a small kernel
 * buffer that you can use to transfer data from one end to the other.
 *
 * The traditional unix read/write is extended with a "splice()" operation
 * that transfers data buffers to or from a pipe buffer.
 *
 * Named by Larry McVoy, original implementation from Linus, extended by
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 * Jens to support splicing to files, network, direct splicing, etc and
 * fixing lots of bugs.
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 *
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 * Copyright (C) 2005-2006 Jens Axboe <axboe@kernel.dk>
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 * Copyright (C) 2005-2006 Linus Torvalds <torvalds@osdl.org>
 * Copyright (C) 2006 Ingo Molnar <mingo@elte.hu>
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 *
 */
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/pagemap.h>
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#include <linux/splice.h>
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#include <linux/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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/*
 * 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;
43

44 45
	lock_page(page);

46 47 48
	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);
59

60
		if (PagePrivate(page))
61
			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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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.
116
		 */
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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)
169
{
170
	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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177 178
	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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207
			if (!--spd->nr_pages)
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				break;
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			if (pipe->nrbufs < PIPE_BUFFERS)
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				continue;

			break;
		}

215
		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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	}

240
	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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	}

251
	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.
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	 */
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	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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	/*
	 * If find_get_pages_contig() returned fewer pages than we needed,
297
	 * allocate the rest and fill in the holes.
298
	 */
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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);
394
			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.
				 */
401
				if (error == AOP_TRUNCATED_PAGE)
402 403
					error = 0;

404 405
				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;
422 423

			/*
424
			 * max good bytes in this page
425
			 */
426 427
			plen = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
			if (plen <= loff)
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				break;

			/*
431
			 * force quit after adding this page
432
			 */
433 434
			this_len = min(this_len, plen - loff);
			len = this_len;
435
		}
436

437 438
		partial[page_nr].offset = loff;
		partial[page_nr].len = this_len;
439
		len -= this_len;
440
		loff = 0;
441 442
		spd.nr_pages++;
		index++;
443 444
	}

445
	/*
446
	 * Release any pages at the end, if we quit early. 'page_nr' is how far
447 448 449 450 451
	 * we got, 'nr_pages' is how many pages are in the map.
	 */
	while (page_nr < nr_pages)
		page_cache_release(pages[page_nr++]);

452
	if (spd.nr_pages)
453
		return splice_to_pipe(pipe, &spd);
454

455
	return error;
456 457
}

458 459 460
/**
 * generic_file_splice_read - splice data from file to a pipe
 * @in:		file to splice from
461
 * @ppos:	position in @in
462 463 464 465
 * @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.
 *
471
 */
472 473 474
ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
				 struct pipe_inode_info *pipe, size_t len,
				 unsigned int flags)
475 476 477
{
	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;
487 488 489 490

	ret = 0;
	spliced = 0;
	while (len) {
491
		ret = __generic_file_splice_read(in, ppos, pipe, len, flags);
492

493
		if (ret < 0)
494
			break;
495 496 497 498 499 500 501 502
		else if (!ret) {
			if (spliced)
				break;
			if (flags & SPLICE_F_NONBLOCK) {
				ret = -EAGAIN;
				break;
			}
		}
503

504
		*ppos += ret;
505 506 507 508 509 510 511 512 513 514
		len -= ret;
		spliced += ret;
	}

	if (spliced)
		return spliced;

	return ret;
}

515 516
EXPORT_SYMBOL(generic_file_splice_read);

517
/*
518
 * 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.
520
 */
521
static int pipe_to_sendpage(struct pipe_inode_info *pipe,
522 523
			    struct pipe_buffer *buf, struct splice_desc *sd)
{
524
	struct file *file = sd->u.file;
525
	loff_t pos = sd->pos;
526
	int ret, more;
527

528
	ret = buf->ops->confirm(pipe, buf);
529 530
	if (!ret) {
		more = (sd->flags & SPLICE_F_MORE) || sd->len < sd->total_len;
531

532 533 534
		ret = file->f_op->sendpage(file, buf->page, buf->offset,
					   sd->len, &pos, more);
	}
535

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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.
558
 */
559
static int pipe_to_file(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
560 561
			struct splice_desc *sd)
{
562
	struct file *file = sd->u.file;
563
	struct address_space *mapping = file->f_mapping;
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564
	unsigned int offset, this_len;
565 566
	struct page *page;
	pgoff_t index;
567
	int ret;
568 569

	/*
570
	 * make sure the data in this buffer is uptodate
571
	 */
572
	ret = buf->ops->confirm(pipe, buf);
573 574
	if (unlikely(ret))
		return ret;
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	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;

591
		/*
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592
		 * This will also lock the page
593
		 */
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		ret = add_to_page_cache_lru(page, mapping, index,
					    GFP_KERNEL);
		if (unlikely(ret))
			goto out;
	}
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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);

617
		goto out_ret;
618
	}
619

620
	if (buf->page != page) {
621 622 623
		/*
		 * Careful, ->map() uses KM_USER0!
		 */
624
		char *src = buf->ops->map(pipe, buf, 1);
625
		char *dst = kmap_atomic(page, KM_USER1);
626

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		memcpy(dst + offset, src + buf->offset, this_len);
628
		flush_dcache_page(page);
629
		kunmap_atomic(dst, KM_USER1);
630
		buf->ops->unmap(pipe, buf, src);
631
	}
632

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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;
641
		/*
642 643
		 * Partial write has happened, so 'ret' already initialized by
		 * number of bytes written, Where is nothing we have to do here.
644
		 */
645
	} else
646
		ret = this_len;
647 648 649 650 651
	/*
	 * Return the number of bytes written and mark page as
	 * accessed, we are now done!
	 */
	mark_page_accessed(page);
652
out:
653
	page_cache_release(page);
654
	unlock_page(page);
655
out_ret:
656 657 658
	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.
 *
671
 */
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ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd,
			   splice_actor *actor)
674 675 676 677 678 679 680
{
	int ret, do_wakeup, err;

	ret = 0;
	do_wakeup = 0;

	for (;;) {
681 682
		if (pipe->nrbufs) {
			struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
683
			const struct pipe_buf_operations *ops = buf->ops;
684

J
Jens Axboe 已提交
685 686 687
			sd->len = buf->len;
			if (sd->len > sd->total_len)
				sd->len = sd->total_len;
688

J
Jens Axboe 已提交
689
			err = actor(pipe, buf, sd);
J
Jens Axboe 已提交
690
			if (err <= 0) {
691 692 693 694 695 696
				if (!ret && err != -ENODATA)
					ret = err;

				break;
			}

J
Jens Axboe 已提交
697 698 699 700
			ret += err;
			buf->offset += err;
			buf->len -= err;

J
Jens Axboe 已提交
701 702 703 704
			sd->len -= err;
			sd->pos += err;
			sd->total_len -= err;
			if (sd->len)
J
Jens Axboe 已提交
705
				continue;
I
Ingo Molnar 已提交
706

707 708
			if (!buf->len) {
				buf->ops = NULL;
709
				ops->release(pipe, buf);
710 711 712 713
				pipe->curbuf = (pipe->curbuf + 1) & (PIPE_BUFFERS - 1);
				pipe->nrbufs--;
				if (pipe->inode)
					do_wakeup = 1;
714 715
			}

J
Jens Axboe 已提交
716
			if (!sd->total_len)
717 718 719
				break;
		}

720
		if (pipe->nrbufs)
721
			continue;
722
		if (!pipe->writers)
723
			break;
724
		if (!pipe->waiting_writers) {
725 726 727 728
			if (ret)
				break;
		}

J
Jens Axboe 已提交
729
		if (sd->flags & SPLICE_F_NONBLOCK) {
730 731 732 733 734
			if (!ret)
				ret = -EAGAIN;
			break;
		}

735 736 737 738 739 740 741
		if (signal_pending(current)) {
			if (!ret)
				ret = -ERESTARTSYS;
			break;
		}

		if (do_wakeup) {
742
			smp_mb();
743 744 745
			if (waitqueue_active(&pipe->wait))
				wake_up_interruptible_sync(&pipe->wait);
			kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
746 747 748
			do_wakeup = 0;
		}

749
		pipe_wait(pipe);
750 751 752
	}

	if (do_wakeup) {
753
		smp_mb();
754 755 756
		if (waitqueue_active(&pipe->wait))
			wake_up_interruptible(&pipe->wait);
		kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
757 758 759 760
	}

	return ret;
}
M
Mark Fasheh 已提交
761
EXPORT_SYMBOL(__splice_from_pipe);
762

763 764 765 766 767 768 769 770 771 772 773 774 775 776
/**
 * 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().
 *
 */
777 778 779 780 781 782
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
783 784 785 786
	struct splice_desc sd = {
		.total_len = len,
		.flags = flags,
		.pos = *ppos,
787
		.u.file = out,
J
Jens Axboe 已提交
788
	};
789 790 791 792 793 794 795 796

	/*
	 * 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
797
	ret = __splice_from_pipe(pipe, &sd, actor);
798 799 800 801 802 803 804 805 806
	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
807
 * @ppos:	position in @out
808 809 810
 * @len:	number of bytes to splice
 * @flags:	splice modifier flags
 *
811 812 813 814
 * 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.
815 816 817 818 819 820 821 822
 *
 */
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
823 824 825 826
	struct splice_desc sd = {
		.total_len = len,
		.flags = flags,
		.pos = *ppos,
827
		.u.file = out,
J
Jens Axboe 已提交
828
	};
829 830 831
	ssize_t ret;
	int err;

832
	err = remove_suid(out->f_path.dentry);
833 834 835
	if (unlikely(err))
		return err;

J
Jens Axboe 已提交
836
	ret = __splice_from_pipe(pipe, &sd, pipe_to_file);
837
	if (ret > 0) {
838 839
		unsigned long nr_pages;

840
		*ppos += ret;
841
		nr_pages = (ret + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
842 843 844 845 846 847 848 849 850 851 852 853

		/*
		 * 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;
		}
854
		balance_dirty_pages_ratelimited_nr(mapping, nr_pages);
855 856 857 858 859 860 861
	}

	return ret;
}

EXPORT_SYMBOL(generic_file_splice_write_nolock);

862 863
/**
 * generic_file_splice_write - splice data from a pipe to a file
864
 * @pipe:	pipe info
865
 * @out:	file to write to
866
 * @ppos:	position in @out
867 868 869
 * @len:	number of bytes to splice
 * @flags:	splice modifier flags
 *
870 871 872
 * Description:
 *    Will either move or copy pages (determined by @flags options) from
 *    the given pipe inode to the given file.
873 874
 *
 */
875 876
ssize_t
generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
877
			  loff_t *ppos, size_t len, unsigned int flags)
878
{
879
	struct address_space *mapping = out->f_mapping;
880
	struct inode *inode = mapping->host;
881
	ssize_t ret;
882 883
	int err;

884
	err = should_remove_suid(out->f_path.dentry);
885 886
	if (unlikely(err)) {
		mutex_lock(&inode->i_mutex);
887
		err = __remove_suid(out->f_path.dentry, err);
888 889 890 891
		mutex_unlock(&inode->i_mutex);
		if (err)
			return err;
	}
892

893
	ret = splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_file);
J
Jens Axboe 已提交
894
	if (ret > 0) {
895 896
		unsigned long nr_pages;

J
Jens Axboe 已提交
897
		*ppos += ret;
898
		nr_pages = (ret + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
J
Jens Axboe 已提交
899 900 901 902 903 904 905 906 907 908

		/*
		 * 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);
909

J
Jens Axboe 已提交
910 911 912
			if (err)
				ret = err;
		}
913
		balance_dirty_pages_ratelimited_nr(mapping, nr_pages);
914 915 916
	}

	return ret;
917 918
}

919 920
EXPORT_SYMBOL(generic_file_splice_write);

921 922
/**
 * generic_splice_sendpage - splice data from a pipe to a socket
923
 * @pipe:	pipe to splice from
924
 * @out:	socket to write to
925
 * @ppos:	position in @out
926 927 928
 * @len:	number of bytes to splice
 * @flags:	splice modifier flags
 *
929 930 931
 * Description:
 *    Will send @len bytes from the pipe to a network socket. No data copying
 *    is involved.
932 933
 *
 */
934
ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
935
				loff_t *ppos, size_t len, unsigned int flags)
936
{
937
	return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
938 939
}

940
EXPORT_SYMBOL(generic_splice_sendpage);
J
Jeff Garzik 已提交
941

942 943 944
/*
 * Attempt to initiate a splice from pipe to file.
 */
945
static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
946
			   loff_t *ppos, size_t len, unsigned int flags)
947 948 949
{
	int ret;

950
	if (unlikely(!out->f_op || !out->f_op->splice_write))
951 952
		return -EINVAL;

953
	if (unlikely(!(out->f_mode & FMODE_WRITE)))
954 955
		return -EBADF;

956
	ret = rw_verify_area(WRITE, out, ppos, len);
957 958 959
	if (unlikely(ret < 0))
		return ret;

960
	return out->f_op->splice_write(pipe, out, ppos, len, flags);
961 962
}

963 964 965
/*
 * Attempt to initiate a splice from a file to a pipe.
 */
966 967 968
static long do_splice_to(struct file *in, loff_t *ppos,
			 struct pipe_inode_info *pipe, size_t len,
			 unsigned int flags)
969 970 971
{
	int ret;

972
	if (unlikely(!in->f_op || !in->f_op->splice_read))
973 974
		return -EINVAL;

975
	if (unlikely(!(in->f_mode & FMODE_READ)))
976 977
		return -EBADF;

978
	ret = rw_verify_area(READ, in, ppos, len);
979 980 981
	if (unlikely(ret < 0))
		return ret;

982
	return in->f_op->splice_read(in, ppos, pipe, len, flags);
983 984
}

985 986 987 988 989 990 991 992 993 994 995 996
/**
 * 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
997 998 999
 */
ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
			       splice_direct_actor *actor)
1000 1001 1002 1003
{
	struct pipe_inode_info *pipe;
	long ret, bytes;
	umode_t i_mode;
J
Jens Axboe 已提交
1004 1005
	size_t len;
	int i, flags;
1006 1007 1008 1009 1010 1011

	/*
	 * 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!
	 */
1012
	i_mode = in->f_path.dentry->d_inode->i_mode;
1013 1014 1015 1016 1017 1018 1019 1020
	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;
1021
	if (unlikely(!pipe)) {
1022 1023 1024 1025 1026 1027
		pipe = alloc_pipe_info(NULL);
		if (!pipe)
			return -ENOMEM;

		/*
		 * We don't have an immediate reader, but we'll read the stuff
1028
		 * out of the pipe right after the splice_to_pipe(). So set
1029 1030 1031 1032 1033 1034 1035 1036
		 * PIPE_READERS appropriately.
		 */
		pipe->readers = 1;

		current->splice_pipe = pipe;
	}

	/*
I
Ingo Molnar 已提交
1037
	 * Do the splice.
1038 1039 1040
	 */
	ret = 0;
	bytes = 0;
J
Jens Axboe 已提交
1041 1042 1043 1044 1045 1046 1047
	len = sd->total_len;
	flags = sd->flags;

	/*
	 * Don't block on output, we have to drain the direct pipe.
	 */
	sd->flags &= ~SPLICE_F_NONBLOCK;
1048 1049 1050 1051 1052 1053 1054 1055 1056

	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
1057
		ret = do_splice_to(in, &sd->pos, pipe, max_read_len, flags);
1058 1059 1060 1061
		if (unlikely(ret < 0))
			goto out_release;

		read_len = ret;
J
Jens Axboe 已提交
1062
		sd->total_len = read_len;
1063 1064 1065 1066 1067 1068

		/*
		 * 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
1069
		ret = actor(pipe, sd);
1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 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
		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
1114 1115 1116 1117 1118 1119 1120

}
EXPORT_SYMBOL(splice_direct_to_actor);

static int direct_splice_actor(struct pipe_inode_info *pipe,
			       struct splice_desc *sd)
{
1121
	struct file *file = sd->u.file;
J
Jens Axboe 已提交
1122 1123 1124 1125

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

1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140
/**
 * 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
1141 1142 1143 1144 1145 1146 1147 1148
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,
1149
		.u.file		= out,
J
Jens Axboe 已提交
1150 1151 1152 1153 1154 1155
	};
	size_t ret;

	ret = splice_direct_to_actor(in, &sd, direct_splice_actor);
	*ppos = sd.pos;
	return ret;
1156 1157
}

1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170
/*
 * 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;
}

1171 1172 1173
/*
 * Determine where to splice to/from.
 */
1174 1175 1176
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)
1177
{
1178
	struct pipe_inode_info *pipe;
1179
	loff_t offset, *off;
J
Jens Axboe 已提交
1180
	long ret;
1181

1182
	pipe = pipe_info(in->f_path.dentry->d_inode);
1183 1184 1185
	if (pipe) {
		if (off_in)
			return -ESPIPE;
1186 1187 1188
		if (off_out) {
			if (out->f_op->llseek == no_llseek)
				return -EINVAL;
1189
			if (copy_from_user(&offset, off_out, sizeof(loff_t)))
1190
				return -EFAULT;
1191 1192 1193
			off = &offset;
		} else
			off = &out->f_pos;
1194

J
Jens Axboe 已提交
1195 1196 1197 1198 1199 1200
		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;
1201
	}
1202

1203
	pipe = pipe_info(out->f_path.dentry->d_inode);
1204 1205 1206
	if (pipe) {
		if (off_out)
			return -ESPIPE;
1207 1208 1209
		if (off_in) {
			if (in->f_op->llseek == no_llseek)
				return -EINVAL;
1210
			if (copy_from_user(&offset, off_in, sizeof(loff_t)))
1211
				return -EFAULT;
1212 1213 1214
			off = &offset;
		} else
			off = &in->f_pos;
1215

J
Jens Axboe 已提交
1216 1217 1218 1219 1220 1221
		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;
1222
	}
1223 1224 1225 1226

	return -EINVAL;
}

1227 1228 1229 1230 1231 1232 1233 1234 1235
/*
 * 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,
1236
				struct partial_page *partial, int aligned)
1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 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
{
	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;
1276 1277 1278 1279 1280 1281 1282 1283 1284

		/*
		 * 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;

1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299
		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++) {
1300
			const int plen = min_t(size_t, len, PAGE_SIZE - off);
1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 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

			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;
}

1338 1339 1340 1341 1342 1343
static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
			struct splice_desc *sd)
{
	char *src;
	int ret;

1344
	ret = buf->ops->confirm(pipe, buf);
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 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
	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;
}

1456 1457 1458 1459 1460
/*
 * 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.
 */
1461 1462
static long vmsplice_to_pipe(struct file *file, const struct iovec __user *iov,
			     unsigned long nr_segs, unsigned int flags)
1463
{
1464
	struct pipe_inode_info *pipe;
1465 1466 1467 1468 1469 1470 1471 1472 1473
	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,
	};

1474
	pipe = pipe_info(file->f_path.dentry->d_inode);
1475
	if (!pipe)
1476 1477
		return -EBADF;

1478 1479
	spd.nr_pages = get_iovec_page_array(iov, nr_segs, pages, partial,
					    flags & SPLICE_F_GIFT);
1480 1481 1482
	if (spd.nr_pages <= 0)
		return spd.nr_pages;

1483
	return splice_to_pipe(pipe, &spd);
1484 1485
}

1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500 1501
/*
 * 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().
 *
 */
1502 1503 1504 1505 1506 1507 1508
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;

1509 1510 1511 1512 1513
	if (unlikely(nr_segs > UIO_MAXIOV))
		return -EINVAL;
	else if (unlikely(!nr_segs))
		return 0;

1514 1515 1516 1517
	error = -EBADF;
	file = fget_light(fd, &fput);
	if (file) {
		if (file->f_mode & FMODE_WRITE)
1518 1519 1520
			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);
1521 1522 1523 1524 1525 1526 1527

		fput_light(file, fput);
	}

	return error;
}

1528 1529 1530
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)
1531 1532 1533 1534 1535 1536 1537 1538 1539
{
	long error;
	struct file *in, *out;
	int fput_in, fput_out;

	if (unlikely(!len))
		return 0;

	error = -EBADF;
1540
	in = fget_light(fd_in, &fput_in);
1541 1542
	if (in) {
		if (in->f_mode & FMODE_READ) {
1543
			out = fget_light(fd_out, &fput_out);
1544 1545
			if (out) {
				if (out->f_mode & FMODE_WRITE)
1546 1547 1548
					error = do_splice(in, off_in,
							  out, off_out,
							  len, flags);
1549 1550 1551 1552 1553 1554 1555 1556 1557
				fput_light(out, fput_out);
			}
		}

		fput_light(in, fput_in);
	}

	return error;
}
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 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
/*
 * 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;
}

1638 1639 1640 1641 1642 1643 1644 1645
/*
 * 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;
1646
	int ret = 0, i = 0, nbuf;
1647 1648 1649 1650 1651 1652

	/*
	 * 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).
	 */
1653
	inode_double_lock(ipipe->inode, opipe->inode);
1654

1655
	do {
1656 1657 1658 1659 1660 1661 1662
		if (!opipe->readers) {
			send_sig(SIGPIPE, current, 0);
			if (!ret)
				ret = -EPIPE;
			break;
		}

1663 1664 1665 1666 1667 1668
		/*
		 * If we have iterated all input buffers or ran out of
		 * output room, break.
		 */
		if (i >= ipipe->nrbufs || opipe->nrbufs >= PIPE_BUFFERS)
			break;
1669

1670 1671
		ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (PIPE_BUFFERS - 1));
		nbuf = (opipe->curbuf + opipe->nrbufs) & (PIPE_BUFFERS - 1);
1672 1673

		/*
1674 1675
		 * Get a reference to this pipe buffer,
		 * so we can copy the contents over.
1676
		 */
1677 1678 1679 1680 1681
		ibuf->ops->get(ipipe, ibuf);

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

1682
		/*
1683 1684
		 * Don't inherit the gift flag, we need to
		 * prevent multiple steals of this page.
1685
		 */
1686
		obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1687

1688 1689
		if (obuf->len > len)
			obuf->len = len;
1690

1691 1692 1693 1694 1695
		opipe->nrbufs++;
		ret += obuf->len;
		len -= obuf->len;
		i++;
	} while (len);
1696

1697
	inode_double_unlock(ipipe->inode, opipe->inode);
1698

1699 1700 1701 1702
	/*
	 * If we put data in the output pipe, wakeup any potential readers.
	 */
	if (ret > 0) {
1703 1704 1705 1706 1707 1708 1709 1710 1711 1712 1713 1714 1715 1716 1717 1718 1719 1720
		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)
{
1721 1722
	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);
1723
	int ret = -EINVAL;
1724 1725

	/*
1726 1727
	 * Duplicate the contents of ipipe to opipe without actually
	 * copying the data.
1728
	 */
1729 1730 1731 1732 1733 1734 1735 1736 1737 1738 1739 1740 1741 1742 1743
	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;
			}
		}
	}
1744

1745
	return ret;
1746 1747 1748 1749 1750 1751 1752 1753 1754 1755 1756 1757 1758 1759 1760 1761 1762 1763 1764 1765 1766 1767 1768 1769 1770 1771 1772 1773
}

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;
}