[Devel] [PATCH 1/2] Fix net buffer logic (v2)

[Dan Smith]

The previous change to the buffer save/restore logic caused us to
incorrectly attempt to restore buffers on a socket in a few instances
where flags may not be restored yet or we are in a temporarily altered
state.

So, keep the same logic, but save a flag to indicate whether buffers were
checkpointed to avoid the ambiguity at restore time.

Also, move the UNIX buffer restore point to the main function to avoid
potentially ignoring the flag on a socket we assume wouldn't have saved
buffers.

Changes in v2:
- Move ckpt_sock_need_buffers() back into net/checkpoint.c, since it
  is now the only user

Signed-off-by: Dan Smith <danms at us.ibm.com>
---
 include/linux/checkpoint.h     |    4 ----
 include/linux/checkpoint_hdr.h |    2 ++
 net/checkpoint.c               |    9 ++++++++-
 net/ipv4/checkpoint.c          |    2 +-
 net/unix/checkpoint.c          |    9 ++++++---
 5 files changed, 17 insertions(+), 9 deletions(-)

diff --git a/include/linux/checkpoint.h b/include/linux/checkpoint.h
index 0437de2..4e25042 100644
--- a/include/linux/checkpoint.h
+++ b/include/linux/checkpoint.h
@@ -126,10 +126,6 @@ extern int ckpt_sock_getnames(struct ckpt_ctx *ctx,
 			      struct sockaddr *rem, unsigned *rem_len);
 extern struct sk_buff *sock_restore_skb(struct ckpt_ctx *ctx, struct sock *sk);
 extern void sock_listening_list_free(struct list_head *head);
-static inline int ckpt_sock_need_buffers(struct sock *sk)
-{
-	return (sk->sk_state != TCP_LISTEN) && !sock_flag(sk, SOCK_DEAD);
-}
 
 #ifdef CONFIG_NETNS_CHECKPOINT
 extern int checkpoint_netns(struct ckpt_ctx *ctx, void *ptr);
diff --git a/include/linux/checkpoint_hdr.h b/include/linux/checkpoint_hdr.h
index 9e8d518..f4f9577 100644
--- a/include/linux/checkpoint_hdr.h
+++ b/include/linux/checkpoint_hdr.h
@@ -596,6 +596,8 @@ struct ckpt_hdr_file_eventfd {
 struct ckpt_hdr_socket {
 	struct ckpt_hdr h;
 
+	__u8 has_buffers;
+
 	struct { /* struct socket */
 		__u64 flags;
 		__u8 state;
diff --git a/net/checkpoint.c b/net/checkpoint.c
index 0d90af2..be2693c 100644
--- a/net/checkpoint.c
+++ b/net/checkpoint.c
@@ -31,6 +31,11 @@ struct dq_buffers {
 	struct sock *sk;
 };
 
+static int ckpt_sock_need_buffers(struct sock *sk)
+{
+	return (sk->sk_state != TCP_LISTEN) && !sock_flag(sk, SOCK_DEAD);
+}
+
 static int sock_copy_buffers(struct sk_buff_head *from,
 			     struct sk_buff_head *to,
 			     uint32_t *total_bytes)
@@ -761,6 +766,8 @@ static int __do_sock_checkpoint(struct ckpt_ctx *ctx, struct sock *sk)
 	if (!h)
 		return -ENOMEM;
 
+	h->has_buffers = ckpt_sock_need_buffers(sk);
+
 	/* part I: common to all sockets */
 	ret = sock_cptrst(ctx, sk, h, CKPT_CPT);
 	if (ret < 0)
@@ -776,7 +783,7 @@ static int __do_sock_checkpoint(struct ckpt_ctx *ctx, struct sock *sk)
 		goto out;
 
 	/* part III: socket buffers */
-	if (ckpt_sock_need_buffers(sk))
+	if (h->has_buffers)
 		ret = sock_defer_write_buffers(ctx, sk);
  out:
 	ckpt_hdr_put(ctx, h);
diff --git a/net/ipv4/checkpoint.c b/net/ipv4/checkpoint.c
index eb02175..ec42e57 100644
--- a/net/ipv4/checkpoint.c
+++ b/net/ipv4/checkpoint.c
@@ -539,7 +539,7 @@ int inet_restore(struct ckpt_ctx *ctx,
 		}
 	}
 
-	if (ckpt_sock_need_buffers(sock->sk))
+	if (h->has_buffers)
 		ret = inet_defer_restore_buffers(ctx, sock->sk);
  out:
 	ckpt_hdr_put(ctx, in);
diff --git a/net/unix/checkpoint.c b/net/unix/checkpoint.c
index 1fa3d7e..47d38e2 100644
--- a/net/unix/checkpoint.c
+++ b/net/unix/checkpoint.c
@@ -443,9 +443,6 @@ static int unix_restore_connected(struct ckpt_ctx *ctx,
 		ckpt_debug("unix_defer_join: %i\n", ret);
 	}
 
-	if (ckpt_sock_need_buffers(sock->sk) && !ret)
-		ret = unix_defer_restore_buffers(ctx, un->this);
-
 	return ret;
 }
 
@@ -639,6 +636,12 @@ int unix_restore(struct ckpt_ctx *ctx, struct socket *sock,
 	else
 		ckpt_err(ctx, ret, "bad af_unix state %i\n", h->sock.state);
 
+	if (ret < 0)
+		goto out;
+
+	if (h->has_buffers)
+		ret = unix_defer_restore_buffers(ctx, un->this);
+
  out:
 	ckpt_hdr_put(ctx, un);
 	kfree(cwd);
-- 
1.7.1.1

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