From: Jan Kara <jack@suse.cz>

Many inodes have no pagecache, so we can avoid lots of lock-takings.

Signed-off-by: Jan Kara <jack@suse.cz>
Cc: Fengguang Wu <wfg@mail.ustc.edu.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/drop_caches.c |    2 ++
 1 file changed, 2 insertions(+)

diff -puN fs/drop_caches.c~vfs-skip-inodes-without-pages-to-free-in-drop_pagecache_sb fs/drop_caches.c
--- a/fs/drop_caches.c~vfs-skip-inodes-without-pages-to-free-in-drop_pagecache_sb
+++ a/fs/drop_caches.c
@@ -20,6 +20,8 @@ static void drop_pagecache_sb(struct sup
 	list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
 		if (inode->i_state & (I_FREEING|I_WILL_FREE))
 			continue;
+		if (inode->i_mapping->nrpages == 0)
+			continue;
 		__iget(inode);
 		spin_unlock(&inode_lock);
 		__invalidate_mapping_pages(inode->i_mapping, 0, -1, true);
_