[NET]: Make use of ->private_data in sockfd_lookup

Please consider the patch below which makes use of file->private_data to
store the pointer to the socket, which avoids touching several unused
cachelines in the dentry and inode in sockfd_lookup.

Signed-off-by: Benjamin LaHaise <bcrl@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/socket.c b/net/socket.c
index 6f2a178..5f76ab8 100644 (file)
--- a/net/socket.c
+++ b/net/socket.c
@@ -404,6 +404,7 @@ int sock_map_fd(struct socket *sock)
                file->f_mode = FMODE_READ | FMODE_WRITE;
                file->f_flags = O_RDWR;
                file->f_pos = 0;
+               file->private_data = sock;
                fd_install(fd, file);
        }
 
@@ -436,6 +437,9 @@ struct socket *sockfd_lookup(int fd, int *err)
                return NULL;
        }
 
+       if (file->f_op == &socket_file_ops)
+               return file->private_data;      /* set in sock_map_fd */
+
        inode = file->f_dentry->d_inode;
        if (!S_ISSOCK(inode->i_mode)) {
                *err = -ENOTSOCK;