From 82c156f853840645604acd7c2cebcb75ed1b6652 Mon Sep 17 00:00:00 2001
From: Al Viro <viro@zeniv.linux.org.uk>
Date: Thu, 22 Sep 2016 23:35:42 -0400
Subject: switch generic_file_splice_read() to use of ->read_iter()

... and kill the ->splice_read() instances that can be switched to it

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 mm/shmem.c | 115 +------------------------------------------------------------
 1 file changed, 1 insertion(+), 114 deletions(-)

(limited to 'mm/shmem.c')

diff --git a/mm/shmem.c b/mm/shmem.c
index 971fc83e6402..d86b5e455fef 100644
--- a/mm/shmem.c
+++ b/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
-- 
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