[Devel] [PATCH 2/3] Make sockets proper objhash objects and use checkpoint_obj() on them

Dan Smith danms at us.ibm.com
Mon Aug 24 10:11:57 PDT 2009


This changes the checkpoint/restart procedure for sockets a bit.  The
socket file header is now checkpointed separately from the socket itself,
which allows us to checkpoint a socket without arriving at it from a
file descriptor.  Thus, most sockets will be checkpointed as a result
of processing the file table, calling sock_file_checkpoint(fd), which
in turn calls checkpoint_obj(socket).

However, we may arrive at some sockets while checkpointing other objects,
such as the other end of an AF_UNIX socket with buffers in flight.  This
patch just opens that door, which is utilized by the next patch.

Signed-off-by: Dan Smith <danms at us.ibm.com>
---
 checkpoint/objhash.c           |    2 +
 include/linux/checkpoint_hdr.h |    4 +-
 include/net/sock.h             |    2 +
 net/checkpoint.c               |  116 ++++++++++++++++++++++++++++-----------
 net/unix/checkpoint.c          |    3 +-
 5 files changed, 91 insertions(+), 36 deletions(-)

diff --git a/checkpoint/objhash.c b/checkpoint/objhash.c
index 019077b..4f26e86 100644
--- a/checkpoint/objhash.c
+++ b/checkpoint/objhash.c
@@ -381,6 +381,8 @@ static struct ckpt_obj_ops ckpt_obj_ops[] = {
 		.obj_type = CKPT_OBJ_SOCK,
 		.ref_drop = obj_sock_drop,
 		.ref_grab = obj_sock_grab,
+		.checkpoint = checkpoint_sock,
+		.restore = restore_sock,
 	},
 };
 
diff --git a/include/linux/checkpoint_hdr.h b/include/linux/checkpoint_hdr.h
index 78f1f27..39b3cb4 100644
--- a/include/linux/checkpoint_hdr.h
+++ b/include/linux/checkpoint_hdr.h
@@ -68,6 +68,7 @@ enum {
 	CKPT_HDR_USER,
 	CKPT_HDR_GROUPINFO,
 	CKPT_HDR_TASK_CREDS,
+	CKPT_HDR_SOCKET,
 
 	/* 201-299: reserved for arch-dependent */
 
@@ -367,6 +368,7 @@ struct ckpt_hdr_file_pipe {
 
 /* socket */
 struct ckpt_hdr_socket {
+	struct ckpt_hdr h;
 	struct { /* struct socket */
 		__u64 flags;
 		__u8 state;
@@ -425,7 +427,7 @@ struct ckpt_hdr_socket_unix {
 
 struct ckpt_hdr_file_socket {
 	struct ckpt_hdr_file common;
-	struct ckpt_hdr_socket socket;
+	__s32 sock_objref;
 } __attribute__((aligned(8)));
 
 struct ckpt_hdr_utsns {
diff --git a/include/net/sock.h b/include/net/sock.h
index 8e3b050..0db1ca3 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1644,6 +1644,8 @@ extern __u32 sysctl_rmem_default;
 /* Checkpoint/Restart Functions */
 struct ckpt_ctx;
 struct ckpt_hdr_file;
+extern int checkpoint_sock(struct ckpt_ctx *ctx, void *ptr);
+extern void *restore_sock(struct ckpt_ctx *ctx);
 extern int sock_file_checkpoint(struct ckpt_ctx *ctx, struct file *file);
 extern struct file *sock_file_restore(struct ckpt_ctx *ctx,
 				      struct ckpt_hdr_file *h);
diff --git a/net/checkpoint.c b/net/checkpoint.c
index fdbf8e7..c84511e 100644
--- a/net/checkpoint.c
+++ b/net/checkpoint.c
@@ -411,31 +411,26 @@ static int sock_cptrst(struct ckpt_ctx *ctx, struct sock *sk,
 		return 0;
 }
 
-int sock_file_checkpoint(struct ckpt_ctx *ctx, struct file *file)
+static int do_sock_checkpoint(struct ckpt_ctx *ctx, struct sock *sk)
 {
-	struct ckpt_hdr_file_socket *h;
-	struct socket *sock = file->private_data;
-	struct sock *sk = sock->sk;
 	int ret;
+	struct socket *sock = sk->sk_socket;
+	struct ckpt_hdr_socket *h;
 
 	if (!sock->ops->checkpoint) {
 		ckpt_write_err(ctx, "socket (proto_ops: %pS)", sock->ops);
 		return -ENOSYS;
 	}
 
-	h = ckpt_hdr_get_type(ctx, sizeof(*h), CKPT_HDR_FILE);
+	h = ckpt_hdr_get_type(ctx, sizeof(*h), CKPT_HDR_SOCKET);
 	if (!h)
 		return -ENOMEM;
 
-	h->common.f_type = CKPT_FILE_SOCKET;
-
 	/* part I: common to all sockets */
-	ret = sock_cptrst(ctx, sk, &h->socket, CKPT_CPT);
-	if (ret < 0)
-		goto out;
-	ret = checkpoint_file_common(ctx, file, &h->common);
+	ret = sock_cptrst(ctx, sk, h, CKPT_CPT);
 	if (ret < 0)
 		goto out;
+
 	ret = ckpt_write_obj(ctx, (struct ckpt_hdr *) h);
 	if (ret < 0)
 		goto out;
@@ -452,6 +447,42 @@ int sock_file_checkpoint(struct ckpt_ctx *ctx, struct file *file)
 			goto out;
 		ret = sock_write_buffers(ctx, &sk->sk_write_queue);
 	}
+
+ out:
+	ckpt_hdr_put(ctx, h);
+
+	return ret;
+}
+
+int checkpoint_sock(struct ckpt_ctx *ctx, void *ptr)
+{
+	return do_sock_checkpoint(ctx, (struct sock *)ptr);
+}
+
+int sock_file_checkpoint(struct ckpt_ctx *ctx, struct file *file)
+{
+	struct ckpt_hdr_file_socket *h;
+	struct socket *sock = file->private_data;
+	struct sock *sk = sock->sk;
+	int ret;
+
+	h = ckpt_hdr_get_type(ctx, sizeof(*h), CKPT_HDR_FILE);
+	if (!h)
+		return -ENOMEM;
+
+	h->common.f_type = CKPT_FILE_SOCKET;
+
+	h->sock_objref = checkpoint_obj(ctx, sk, CKPT_OBJ_SOCK);
+	if (h->sock_objref < 0) {
+		ret = h->sock_objref;
+		goto out;
+	}
+
+	ret = checkpoint_file_common(ctx, file, &h->common);
+	if (ret < 0)
+		goto out;
+
+	ret = ckpt_write_obj(ctx, (struct ckpt_hdr *) h);
  out:
 	ckpt_hdr_put(ctx, h);
 	return ret;
@@ -511,35 +542,30 @@ static struct file *sock_alloc_attach_fd(struct socket *sock)
 	return file;
 }
 
-struct file *sock_file_restore(struct ckpt_ctx *ctx, struct ckpt_hdr_file *ptr)
+static struct sock *do_sock_restore(struct ckpt_ctx *ctx)
 {
-	struct ckpt_hdr_file_socket *hh = (struct ckpt_hdr_file_socket *) ptr;
-	struct ckpt_hdr_socket *h = &hh->socket;
+	struct ckpt_hdr_socket *h;
 	struct socket *sock;
-	struct file *file;
 	int ret;
 
-	if (ptr->h.type != CKPT_HDR_FILE  ||
-	    ptr->h.len != sizeof(*hh) || ptr->f_type != CKPT_FILE_SOCKET)
-		return ERR_PTR(-EINVAL);
+	h = ckpt_read_obj_type(ctx, sizeof(*h), CKPT_HDR_SOCKET);
+	if (IS_ERR(h))
+		return ERR_PTR(PTR_ERR(h));
 
 	/* silently clear flags, e.g. SOCK_NONBLOCK or SOCK_CLOEXEC */
 	h->sock.type &= SOCK_TYPE_MASK;
 
 	ret = sock_create(h->sock_common.family, h->sock.type, 0, &sock);
 	if (ret < 0)
-		return ERR_PTR(ret);
+		goto err;
 
+	/* part II and III: per-protocol restore */
 	if (!sock->ops->restore) {
 		ckpt_debug("proto_ops lacks checkpoint: %pS\n", sock->ops);
 		ret = -EINVAL;
 		goto err;
 	}
 
-	/*
-	 * part II: per socket type state
-	 * (also takes care of part III: socket buffer)
-	 */
 	ret = sock->ops->restore(ctx, sock, h);
 	if (ret < 0)
 		goto err;
@@ -549,21 +575,45 @@ struct file *sock_file_restore(struct ckpt_ctx *ctx, struct ckpt_hdr_file *ptr)
 	if (ret < 0)
 		goto err;
 
-	file = sock_alloc_attach_fd(sock);
-	if (IS_ERR(file)) {
-		ret = PTR_ERR(file);
-		goto err;
-	}
+	ckpt_hdr_put(ctx, h);
+
+	return sock->sk;
+ err:
+	ckpt_hdr_put(ctx, h);
+	sock_release(sock);
+
+	return ERR_PTR(ret);
+}
+
+void *restore_sock(struct ckpt_ctx *ctx)
+{
+	return do_sock_restore(ctx);
+}
+
+struct file *sock_file_restore(struct ckpt_ctx *ctx, struct ckpt_hdr_file *ptr)
+{
+	struct ckpt_hdr_file_socket *h = (struct ckpt_hdr_file_socket *)ptr;
+	struct sock *sk;
+	struct file *file;
+	int ret;
+
+	if (ptr->h.type != CKPT_HDR_FILE || ptr->f_type != CKPT_FILE_SOCKET)
+		return ERR_PTR(-EINVAL);
+
+	sk = ckpt_obj_fetch(ctx, h->sock_objref, CKPT_OBJ_SOCK);
+	if (IS_ERR(sk))
+		return ERR_PTR(PTR_ERR(sk));
+
+	file = sock_alloc_attach_fd(sk->sk_socket);
+	if (IS_ERR(file))
+		return file;
 
 	ret = restore_file_common(ctx, file, ptr);
 	if (ret < 0) {
 		fput(file);
-		file = ERR_PTR(ret);
+		return ERR_PTR(ret);
 	}
-	return file;
 
- err:
-	sock_release(sock);
-	return ERR_PTR(ret);
+	return file;
 }
 
diff --git a/net/unix/checkpoint.c b/net/unix/checkpoint.c
index 366bc80..cda8434 100644
--- a/net/unix/checkpoint.c
+++ b/net/unix/checkpoint.c
@@ -57,7 +57,6 @@ static int unix_write_cwd(struct ckpt_ctx *ctx,
 int unix_checkpoint(struct ckpt_ctx *ctx, struct socket *sock)
 {
 	struct unix_sock *sk = unix_sk(sock->sk);
-	struct unix_sock *pr = unix_sk(sk->peer);
 	struct ckpt_hdr_socket_unix *un;
 	int new;
 	int ret = -ENOMEM;
@@ -86,7 +85,7 @@ int unix_checkpoint(struct ckpt_ctx *ctx, struct socket *sock)
 		goto out;
 
 	if (sk->peer)
-		un->peer = ckpt_obj_lookup_add(ctx, pr, CKPT_OBJ_SOCK, &new);
+		un->peer = checkpoint_obj(ctx, sk->peer, CKPT_OBJ_SOCK);
 	else
 		un->peer = 0;
 
-- 
1.6.2.5

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