[PATCH 11/12] fuse: Convert from readpages to readahead

[Matthew Wilcox <willy@infradead.org>]

From: "Matthew Wilcox (Oracle)" <willy@infradead.org>

Use the new readahead operation in fuse.  Switching away from the
read_cache_pages() helper gets rid of an implicit call to put_page(),
so we can get rid of the get_page() call in fuse_readpages_fill().
We can also get rid of the call to fuse_wait_on_page_writeback() as
this page is newly allocated and so cannot be under writeback.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 fs/fuse/file.c | 35 +++++++++++++++++------------------
 1 file changed, 17 insertions(+), 18 deletions(-)

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index ce715380143c..b6d0ed7d805b 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -911,16 +911,13 @@ struct fuse_fill_data {
 	unsigned int max_pages;
 };
 
-static int fuse_readpages_fill(void *_data, struct page *page)
+static int fuse_readpages_fill(struct fuse_fill_data *data, struct page *page)
 {
-	struct fuse_fill_data *data = _data;
 	struct fuse_io_args *ia = data->ia;
 	struct fuse_args_pages *ap = &ia->ap;
 	struct inode *inode = data->inode;
 	struct fuse_conn *fc = get_fuse_conn(inode);
 
-	fuse_wait_on_page_writeback(inode, page->index);
-
 	if (ap->num_pages &&
 	    (ap->num_pages == fc->max_pages ||
 	     (ap->num_pages + 1) * PAGE_SIZE > fc->max_read ||
@@ -942,7 +939,6 @@ static int fuse_readpages_fill(void *_data, struct page *page)
 		return -EIO;
 	}
 
-	get_page(page);
 	ap->pages[ap->num_pages] = page;
 	ap->descs[ap->num_pages].length = PAGE_SIZE;
 	ap->num_pages++;
@@ -950,15 +946,13 @@ static int fuse_readpages_fill(void *_data, struct page *page)
 	return 0;
 }
 
-static int fuse_readpages(struct file *file, struct address_space *mapping,
-			  struct list_head *pages, unsigned nr_pages)
+static unsigned fuse_readahead(struct file *file, struct address_space *mapping,
+			  pgoff_t start, unsigned nr_pages)
 {
 	struct inode *inode = mapping->host;
 	struct fuse_conn *fc = get_fuse_conn(inode);
 	struct fuse_fill_data data;
-	int err;
 
-	err = -EIO;
 	if (is_bad_inode(inode))
 		goto out;
 
@@ -968,19 +962,24 @@ static int fuse_readpages(struct file *file, struct address_space *mapping,
 	data.max_pages = min_t(unsigned int, nr_pages, fc->max_pages);
 ;
 	data.ia = fuse_io_alloc(NULL, data.max_pages);
-	err = -ENOMEM;
 	if (!data.ia)
 		goto out;
 
-	err = read_cache_pages(mapping, pages, fuse_readpages_fill, &data);
-	if (!err) {
-		if (data.ia->ap.num_pages)
-			fuse_send_readpages(data.ia, file);
-		else
-			fuse_io_free(data.ia);
+	while (nr_pages--) {
+		struct page *page = readahead_page(mapping, start++);
+		int err = fuse_readpages_fill(&data, page);
+
+		if (!err)
+			continue;
+		nr_pages++;
+		goto out;
 	}
+	if (data.ia->ap.num_pages)
+		fuse_send_readpages(data.ia, file);
+	else
+		fuse_io_free(data.ia);
 out:
-	return err;
+	return nr_pages;
 }
 
 static ssize_t fuse_cache_read_iter(struct kiocb *iocb, struct iov_iter *to)
@@ -3358,10 +3357,10 @@ static const struct file_operations fuse_file_operations = {
 
 static const struct address_space_operations fuse_file_aops  = {
 	.readpage	= fuse_readpage,
+	.readahead	= fuse_readahead,
 	.writepage	= fuse_writepage,
 	.writepages	= fuse_writepages,
 	.launder_page	= fuse_launder_page,
-	.readpages	= fuse_readpages,
 	.set_page_dirty	= __set_page_dirty_nobuffers,
 	.bmap		= fuse_bmap,
 	.direct_IO	= fuse_direct_IO,
-- 
2.24.1