vfs: skip inodes without pages to free in drop_pagecache_sb()

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>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/fs/drop_caches.c b/fs/drop_caches.c
index 50f9087635d8..3e5637fc3779 100644
--- a/fs/drop_caches.c
+++ b/fs/drop_caches.c
@@ -20,6 +20,8 @@ static void drop_pagecache_sb(struct super_block *sb)
         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);