f2fs: optimize get node page readahead part

We can remove the call to find_get_page to get a page from the cache
and check for up-to-date, instead we can make use of grab_cache_page
part itself to fetch the page from the cache.
So, removing the call and moving the PageUptodate at proper place, also
taken care of moving the lock_page condition in the page_hit part.
Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
Signed-off-by: Amit Sahrawat <a.sahrawat@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>

fs/f2fs/node.c

@@ -921,19 +921,17 @@ struct page *get_node_page_ra(struct page *parent, int start)
 	if (!nid)
 		return ERR_PTR(-ENOENT);
 
-	page = find_get_page(mapping, nid);
-	if (page && PageUptodate(page))
-		goto page_hit;
-	f2fs_put_page(page, 0);
-
 repeat:
 	page = grab_cache_page(mapping, nid);
 	if (!page)
 		return ERR_PTR(-ENOMEM);
+	else if (PageUptodate(page))
+		goto page_hit;
 
 	err = read_node_page(page, READ_SYNC);
+	unlock_page(page);
 	if (err) {
-		f2fs_put_page(page, 1);
+		f2fs_put_page(page, 0);
 		return ERR_PTR(err);
 	}
 
@@ -947,8 +945,9 @@ struct page *get_node_page_ra(struct page *parent, int start)
 		ra_node_page(sbi, nid);
 	}
 
-page_hit:
 	lock_page(page);
+
+page_hit:
 	if (PageError(page)) {
 		f2fs_put_page(page, 1);
 		return ERR_PTR(-EIO);