[PATCH 71/75] sunrpc: use SKB fragment destructors to delay completion until page is released by network stack.

Ian Campbell
2011-08-19T13:30:21Z

This prevents an issue where an ACK is delayed, a retransmit is queued (either
at the RPC or TCP level) and the ACK arrives before the retransmission hits the
wire. If this happens to an NFS WRITE RPC then the write() system call
completes and the userspace process can continue, potentially modifying data
referenced by the retransmission before the retransmission occurs.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Neil Brown <neilb@suse.de>
Cc: "J. Bruce Fields" <bfields@fieldses.org>
Cc: linux-nfs@vger.kernel.org
Cc: netdev@vger.kernel.org
[since v1:
Push down from NFS layer into RPM layer
]
---
include/linux/sunrpc/xdr.h | 2 ++
include/linux/sunrpc/xprt.h | 5 ++++-
net/sunrpc/clnt.c | 27 ++++++++++++++++++++++-----
net/sunrpc/svcsock.c | 3 ++-
net/sunrpc/xprt.c | 13 +++++++++++++
net/sunrpc/xprtsock.c | 3 ++-
6 files changed, 45 insertions(+), 8 deletions(-)

diff --git a/include/linux/sunrpc/xdr.h b/include/linux/sunrpc/xdr.h
index a20970e..172f81e 100644
--- a/include/linux/sunrpc/xdr.h
+++ b/include/linux/sunrpc/xdr.h
@@ -16,6 +16,7 @@
#include <asm/byteorder.h>
#include <asm/unaligned.h>
#include <linux/scatterlist.h>
+#include <linux/skbuff.h>

/*
* Buffer adjustment
@@ -57,6 +58,7 @@ struct xdr_buf {
tail[1]; /* Appended after page data */

struct page ** pages; /* Array of contiguous pages */
+ struct skb_frag_destructor *destructor;
unsigned int page_base, /* Start of page data */
page_len, /* Length of page data */
flags; /* Flags for data disposition */
diff --git a/include/linux/sunrpc/xprt.h b/include/linux/sunrpc/xprt.h
index 15518a1..75131eb 100644
--- a/include/linux/sunrpc/xprt.h
+++ b/include/linux/sunrpc/xprt.h
@@ -92,7 +92,10 @@ struct rpc_rqst {
/* A cookie used to track the
state of the transport
connection */
-
+ struct skb_frag_destructor destructor; /* SKB paged fragment
+ * destructor for
+ * transmitted pages*/
+
/*
* Partial send handling
*/
diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
index c5347d2..919538d 100644
--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -61,6 +61,7 @@ static void call_reserve(struct rpc_task *task);
static void call_reserveresult(struct rpc_task *task);
static void call_allocate(struct rpc_task *task);
static void call_decode(struct rpc_task *task);
+static void call_complete(struct rpc_task *task);
static void call_bind(struct rpc_task *task);
static void call_bind_status(struct rpc_task *task);
static void call_transmit(struct rpc_task *task);
@@ -1113,6 +1114,8 @@ rpc_xdr_encode(struct rpc_task *task)
(char *)req->rq_buffer + req->rq_callsize,
req->rq_rcvsize);

+ req->rq_snd_buf.destructor = &req->destructor;
+
p = rpc_encode_header(task);
if (p == NULL) {
printk(KERN_INFO "RPC: couldn't encode RPC header, exit EIO\n");
@@ -1276,6 +1279,7 @@ call_connect_status(struct rpc_task *task)
static void
call_transmit(struct rpc_task *task)
{
+ struct rpc_rqst *req = task->tk_rqstp;
dprint_status(task);

task->tk_action = call_status;
@@ -1309,8 +1313,8 @@ call_transmit(struct rpc_task *task)
call_transmit_status(task);
if (rpc_reply_expected(task))
return;
- task->tk_action = rpc_exit_task;
- rpc_wake_up_queued_task(&task->tk_xprt->pending, task);
+ task->tk_action = call_complete;
+ skb_frag_destructor_unref(&req->destructor);
}

/*
@@ -1383,7 +1387,8 @@ call_bc_transmit(struct rpc_task *task)
return;
}

- task->tk_action = rpc_exit_task;
+ task->tk_action = call_complete;
+ skb_frag_destructor_unref(&req->destructor);
if (task->tk_status < 0) {
printk(KERN_NOTICE "RPC: Could not send backchannel reply "
"error: %d\n", task->tk_status);
@@ -1423,7 +1428,6 @@ call_bc_transmit(struct rpc_task *task)
"error: %d\n", task->tk_status);
break;
}
- rpc_wake_up_queued_task(&req->rq_xprt->pending, task);
}
#endif /* CONFIG_SUNRPC_BACKCHANNEL */

@@ -1589,12 +1593,14 @@ call_decode(struct rpc_task *task)
return;
}

- task->tk_action = rpc_exit_task;
+ task->tk_action = call_complete;

if (decode) {
task->tk_status = rpcauth_unwrap_resp(task, decode, req, p,
task->tk_msg.rpc_resp);
}
+ rpc_sleep_on(&req->rq_xprt->pending, task, NULL);
+ skb_frag_destructor_unref(&req->destructor);
dprintk("RPC: %5u call_decode result %d\n", task->tk_pid,
task->tk_status);
return;
@@ -1609,6 +1615,17 @@ out_retry:
}
}

+/*
+ * 8. Wait for pages to be released by the network stack.
+ */
+static void
+call_complete(struct rpc_task *task)
+{
+ dprintk("RPC: %5u call_complete result %d\n",
+ task->tk_pid, task->tk_status);
+ task->tk_action = rpc_exit_task;
+}
+
static __be32 *
rpc_encode_header(struct rpc_task *task)
{
diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
index 852a258..3685cad 100644
--- a/net/sunrpc/svcsock.c
+++ b/net/sunrpc/svcsock.c
@@ -196,7 +196,8 @@ int svc_send_common(struct socket *sock, struct xdr_buf *xdr,
while (pglen > 0) {
if (slen == size)
flags = 0;
- result = kernel_sendpage(sock, *ppage, NULL, base, size, flags);
+ result = kernel_sendpage(sock, *ppage, xdr->destructor,
+ base, size, flags);
if (result > 0)
len += result;
if (result != size)
diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c
index f4385e4..925aa0c 100644
--- a/net/sunrpc/xprt.c
+++ b/net/sunrpc/xprt.c
@@ -1103,6 +1103,16 @@ static inline void xprt_init_xid(struct rpc_xprt *xprt)
xprt->xid = net_random();
}

+static int xprt_complete_skb_pages(void *calldata)
+{
+ struct rpc_task *task = calldata;
+ struct rpc_rqst *req = task->tk_rqstp;
+
+ dprintk("RPC: %5u completing skb pages\n", task->tk_pid);
+ rpc_wake_up_queued_task(&req->rq_xprt->pending, task);
+ return 0;
+}
+
static void xprt_request_init(struct rpc_task *task, struct rpc_xprt *xprt)
{
struct rpc_rqst *req = task->tk_rqstp;
@@ -1115,6 +1125,9 @@ static void xprt_request_init(struct rpc_task *task, struct rpc_xprt *xprt)
req->rq_xid = xprt_alloc_xid(xprt);
req->rq_release_snd_buf = NULL;
xprt_reset_majortimeo(req);
+ atomic_set(&req->destructor.ref, 1);
+ req->destructor.destroy = &xprt_complete_skb_pages;
+ req->destructor.data = task;
dprintk("RPC: %5u reserved req %p xid %08x\n", task->tk_pid,
req, ntohl(req->rq_xid));
}
diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
index f79e40e..af3a106 100644
--- a/net/sunrpc/xprtsock.c
+++ b/net/sunrpc/xprtsock.c
@@ -408,7 +408,8 @@ static int xs_send_pagedata(struct socket *sock, struct xdr_buf *xdr, unsigned i
remainder -= len;
if (remainder != 0 || more)
flags |= MSG_MORE;
- err = sock->ops->sendpage(sock, *ppage, NULL, base, len, flags);
+ err = sock->ops->sendpage(sock, *ppage, xdr->destructor,
+ base, len, flags);
if (remainder == 0 || err != len)
break;
sent += err;
--
1.7.2.5