Merge branch 'work.splice_read' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

Pull VFS splice updates from Al Viro:
 "There's a bunch of branches this cycle, both mine and from other folks
  and I'd rather send pull requests separately.

  This one is the conversion of ->splice_read() to ITER_PIPE iov_iter
  (and introduction of such). Gets rid of a lot of code in fs/splice.c
  and elsewhere; there will be followups, but these are for the next
  cycle...  Some pipe/splice-related cleanups from Miklos in the same
  branch as well"

* 'work.splice_read' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  pipe: fix comment in pipe_buf_operations
  pipe: add pipe_buf_steal() helper
  pipe: add pipe_buf_confirm() helper
  pipe: add pipe_buf_release() helper
  pipe: add pipe_buf_get() helper
  relay: simplify relay_file_read()
  switch default_file_splice_read() to use of pipe-backed iov_iter
  switch generic_file_splice_read() to use of ->read_iter()
  new iov_iter flavour: pipe-backed
  fuse_dev_splice_read(): switch to add_to_pipe()
  skb_splice_bits(): get rid of callback
  new helper: add_to_pipe()
  splice: lift pipe_lock out of splice_to_pipe()
  splice: switch get_iovec_page_array() to iov_iter
  splice_to_pipe(): don't open-code wakeup_pipe_readers()
  consistent treatment of EFAULT on O_DIRECT read/write

mm/shmem.c

@@ -2311,119 +2311,6 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
 	return retval ? retval : error;
 }
 
-static ssize_t shmem_file_splice_read(struct file *in, loff_t *ppos,
-				struct pipe_inode_info *pipe, size_t len,
-				unsigned int flags)
-{
-	struct address_space *mapping = in->f_mapping;
-	struct inode *inode = mapping->host;
-	unsigned int loff, nr_pages, req_pages;
-	struct page *pages[PIPE_DEF_BUFFERS];
-	struct partial_page partial[PIPE_DEF_BUFFERS];
-	struct page *page;
-	pgoff_t index, end_index;
-	loff_t isize, left;
-	int error, page_nr;
-	struct splice_pipe_desc spd = {
-		.pages = pages,
-		.partial = partial,
-		.nr_pages_max = PIPE_DEF_BUFFERS,
-		.flags = flags,
-		.ops = &page_cache_pipe_buf_ops,
-		.spd_release = spd_release_page,
-	};
-
-	isize = i_size_read(inode);
-	if (unlikely(*ppos >= isize))
-		return 0;
-
-	left = isize - *ppos;
-	if (unlikely(left < len))
-		len = left;
-
-	if (splice_grow_spd(pipe, &spd))
-		return -ENOMEM;
-
-	index = *ppos >> PAGE_SHIFT;
-	loff = *ppos & ~PAGE_MASK;
-	req_pages = (len + loff + PAGE_SIZE - 1) >> PAGE_SHIFT;
-	nr_pages = min(req_pages, spd.nr_pages_max);
-
-	spd.nr_pages = find_get_pages_contig(mapping, index,
-						nr_pages, spd.pages);
-	index += spd.nr_pages;
-	error = 0;
-
-	while (spd.nr_pages < nr_pages) {
-		error = shmem_getpage(inode, index, &page, SGP_CACHE);
-		if (error)
-			break;
-		unlock_page(page);
-		spd.pages[spd.nr_pages++] = page;
-		index++;
-	}
-
-	index = *ppos >> PAGE_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 = min_t(unsigned long, len, PAGE_SIZE - loff);
-		page = spd.pages[page_nr];
-
-		if (!PageUptodate(page) || page->mapping != mapping) {
-			error = shmem_getpage(inode, index, &page, SGP_CACHE);
-			if (error)
-				break;
-			unlock_page(page);
-			put_page(spd.pages[page_nr]);
-			spd.pages[page_nr] = page;
-		}
-
-		isize = i_size_read(inode);
-		end_index = (isize - 1) >> PAGE_SHIFT;
-		if (unlikely(!isize || index > end_index))
-			break;
-
-		if (end_index == index) {
-			unsigned int plen;
-
-			plen = ((isize - 1) & ~PAGE_MASK) + 1;
-			if (plen <= loff)
-				break;
-
-			this_len = min(this_len, plen - loff);
-			len = this_len;
-		}
-
-		spd.partial[page_nr].offset = loff;
-		spd.partial[page_nr].len = this_len;
-		len -= this_len;
-		loff = 0;
-		spd.nr_pages++;
-		index++;
-	}
-
-	while (page_nr < nr_pages)
-		put_page(spd.pages[page_nr++]);
-
-	if (spd.nr_pages)
-		error = splice_to_pipe(pipe, &spd);
-
-	splice_shrink_spd(&spd);
-
-	if (error > 0) {
-		*ppos += error;
-		file_accessed(in);
-	}
-	return error;
-}
-
 /*
  * llseek SEEK_DATA or SEEK_HOLE through the radix_tree.
  */
@@ -3786,7 +3673,7 @@ static const struct file_operations shmem_file_operations = {
 	.read_iter	= shmem_file_read_iter,
 	.write_iter	= generic_file_write_iter,
 	.fsync		= noop_fsync,
-	.splice_read	= shmem_file_splice_read,
+	.splice_read	= generic_file_splice_read,
 	.splice_write	= iter_file_splice_write,
 	.fallocate	= shmem_fallocate,
 #endif