vfs: conditionally call inode_wb_list_del()

Some inodes (pipes, sockets, ...) are not in bdi writeback list.

evict() can avoid calling inode_wb_list_del() and its expensive spinlock
by checking inode i_wb_list being empty or not.

At this point, no other cpu/user can concurrently manipulate this inode
i_wb_list

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 3 insertions, 1 deletions

diff --git a/fs/inode.c b/fs/inode.c
index d0c72ff6b30e..9dab13ae6ef7 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -454,7 +454,9 @@ static void evict(struct inode *inode)
         BUG_ON(!(inode->i_state & I_FREEING));
         BUG_ON(!list_empty(&inode->i_lru));
 
-        inode_wb_list_del(inode);
+        if (!list_empty(&inode->i_wb_list))
+                inode_wb_list_del(inode);
+
         inode_sb_list_del(inode);
 
         if (op->evict_inode) {