vfs: avoid taking inode_hash_lock on pipes and sockets

Some inodes (pipes, sockets, ...) are not hashed, no need to take
contended inode_hash_lock at dismantle time.

nice speedup on SMP machines on socket intensive workloads.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/include/linux/fs.h b/include/linux/fs.h
index f23bcb7..786b3b1 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2317,11 +2317,18 @@
 extern int file_remove_suid(struct file *);
 
 extern void __insert_inode_hash(struct inode *, unsigned long hashval);
-extern void remove_inode_hash(struct inode *);
 static inline void insert_inode_hash(struct inode *inode)
 {
 	__insert_inode_hash(inode, inode->i_ino);
 }
+
+extern void __remove_inode_hash(struct inode *);
+static inline void remove_inode_hash(struct inode *inode)
+{
+	if (!inode_unhashed(inode))
+		__remove_inode_hash(inode);
+}
+
 extern void inode_sb_list_add(struct inode *inode);
 
 #ifdef CONFIG_BLOCK