On 04/19/2018 04:15 PM, Eric Dumazet wrote:
> I am not sure we can keep mmap() API, since we probably need to first lock
> the socket,
> then grab vm semaphore.
>
We can keep mmap() nice interface, granted we can add one hook like in
following patch.
David, do you think such patch would be acceptable by lkml and mm/fs
maintainers ?
Alternative would be implementing an ioctl() or getsockopt() operation,
but it seems less natural...
Thanks !
diff --git a/include/linux/fs.h b/include/linux/fs.h
index
92efaf1f89775f7b017477617dd983c10e0dc4d2..016c711ac33e226b4285ee5bd688e14661dc0879
100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1714,6 +1714,7 @@ struct file_operations {
long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long);
long (*compat_ioctl) (struct file *, unsigned int, unsigned long);
int (*mmap) (struct file *, struct vm_area_struct *);
+ void (*mmap_hook) (struct file *, bool);
unsigned long mmap_supported_flags;
int (*open) (struct inode *, struct file *);
int (*flush) (struct file *, fl_owner_t id);
diff --git a/mm/util.c b/mm/util.c
index
1fc4fa7576f762bbbf341f056ca6d0be803a423f..b546c59a6169c4dfa9011c61e86da4d03496aa4d
100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -350,11 +350,20 @@ unsigned long vm_mmap_pgoff(struct file *file, unsigned
long addr,
ret = security_mmap_file(file, prot, flag);
if (!ret) {
- if (down_write_killable(&mm->mmap_sem))
+ void (*mmap_hook)(struct file *, bool) = file ?
file->f_op->mmap_hook : NULL;
+
+ if (mmap_hook)
+ mmap_hook(file, true);
+ if (down_write_killable(&mm->mmap_sem)) {
+ if (mmap_hook)
+ mmap_hook(file, false);
return -EINTR;
+ }
ret = do_mmap_pgoff(file, addr, len, prot, flag, pgoff,
&populate, &uf);
up_write(&mm->mmap_sem);
+ if (mmap_hook)
+ mmap_hook(file, false);
userfaultfd_unmap_complete(mm, &uf);
if (populate)
mm_populate(ret, populate);
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index
4022073b0aeea9d07af0fa825b640a00512908a3..79b05d6d41643e8c309dfb8bd9597dc8b00fb0e1
100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1756,8 +1756,6 @@ int tcp_mmap(struct file *file, struct socket *sock,
/* TODO: Maybe the following is not needed if pages are COW */
vma->vm_flags &= ~VM_MAYWRITE;
- lock_sock(sk);
-
ret = -ENOTCONN;
if (sk->sk_state == TCP_LISTEN)
goto out;
@@ -1833,7 +1831,6 @@ int tcp_mmap(struct file *file, struct socket *sock,
ret = 0;
out:
- release_sock(sk);
kvfree(pages_array);
return ret;
}
diff --git a/net/socket.c b/net/socket.c
index
f10f1d947c78c193b49379b0ec641d81367fb4cf..bcabae3c37d765e5c0548a14fc93c19258972b48
100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -131,6 +131,16 @@ static ssize_t sock_splice_read(struct file *file, loff_t
*ppos,
struct pipe_inode_info *pipe, size_t len,
unsigned int flags);
+static void sock_mmap_hook(struct file *file, bool enter)
+{
+ struct socket *sock = file->private_data;
+ struct sock *sk = sock->sk;
+
+ if (enter)
+ lock_sock(sk);
+ else
+ release_sock(sk);
+}
/*
* Socket files have a set of 'special' operations as well as the generic
file ones. These don't appear
* in the operation structures but are done directly via the socketcall()
multiplexor.
@@ -147,6 +157,7 @@ static const struct file_operations socket_file_ops = {
.compat_ioctl = compat_sock_ioctl,
#endif
.mmap = sock_mmap,
+ .mmap_hook = sock_mmap_hook,
.release = sock_close,
.fasync = sock_fasync,
.sendpage = sock_sendpage,
