ext4,f2fs: fix readahead of verity data

The recent change of page_cache_ra_unbounded() arguments was buggy in the
two callers, causing us to readahead the wrong pages.  Move the definition
of ractl down to after the index is set correctly.  This affected
performance on configurations that use fs-verity.

Link: https://lkml.kernel.org/r/20221012193419.1453558-1-willy@infradead.org
Fixes: 73bb49da ("mm/readahead: make page_cache_ra_unbounded take a readahead_control")
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reported-by: Jintao Yin <nicememory@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

fs/ext4/verity.c

@@ -365,13 +365,14 @@ static struct page *ext4_read_merkle_tree_page(struct inode *inode,
 					       pgoff_t index,
 					       unsigned long num_ra_pages)
 {
-	DEFINE_READAHEAD(ractl, NULL, NULL, inode->i_mapping, index);
 	struct page *page;
 
 	index += ext4_verity_metadata_pos(inode) >> PAGE_SHIFT;
 
 	page = find_get_page_flags(inode->i_mapping, index, FGP_ACCESSED);
 	if (!page || !PageUptodate(page)) {
+		DEFINE_READAHEAD(ractl, NULL, NULL, inode->i_mapping, index);
+
 		if (page)
 			put_page(page);
 		else if (num_ra_pages > 1)

fs/f2fs/verity.c

@@ -262,13 +262,14 @@ static struct page *f2fs_read_merkle_tree_page(struct inode *inode,
 					       pgoff_t index,
 					       unsigned long num_ra_pages)
 {
-	DEFINE_READAHEAD(ractl, NULL, NULL, inode->i_mapping, index);
 	struct page *page;
 
 	index += f2fs_verity_metadata_pos(inode) >> PAGE_SHIFT;
 
 	page = find_get_page_flags(inode->i_mapping, index, FGP_ACCESSED);
 	if (!page || !PageUptodate(page)) {
+		DEFINE_READAHEAD(ractl, NULL, NULL, inode->i_mapping, index);
+
 		if (page)
 			put_page(page);
 		else if (num_ra_pages > 1)