This is a note to let you know that I've just added the patch titled
SUNRPC: Fix a slow server-side memory leak with RPC-over-TCP
to the 6.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
sunrpc-fix-a-slow-server-side-memory-leak-with-rpc-o.patch
and it can be found in the queue-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit dfe879bfb9542154b6d758925c8c513eb46a6d67
Author: Chuck Lever <chuck.lever@xxxxxxxxxx>
Date: Wed Apr 3 10:36:25 2024 -0400
SUNRPC: Fix a slow server-side memory leak with RPC-over-TCP
[ Upstream commit 05258a0a69b3c5d2c003f818702c0a52b6fea861 ]
Jan Schunk reports that his small NFS servers suffer from memory
exhaustion after just a few days. A bisect shows that commit
e18e157bb5c8 ("SUNRPC: Send RPC message on TCP with a single
sock_sendmsg() call") is the first bad commit.
That commit assumed that sock_sendmsg() releases all the pages in
the underlying bio_vec array, but the reality is that it doesn't.
svc_xprt_release() releases the rqst's response pages, but the
record marker page fragment isn't one of those, so it is never
released.
This is a narrow fix that can be applied to stable kernels. A
more extensive fix is in the works.
Reported-by: Jan Schunk <scpcom@xxxxxx>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218671
Fixes: e18e157bb5c8 ("SUNRPC: Send RPC message on TCP with a single sock_sendmsg() call")
Cc: Alexander Duyck <alexander.duyck@xxxxxxxxx>
Cc: Jakub Kacinski <kuba@xxxxxxxxxx>
Cc: David Howells <dhowells@xxxxxxxxxx>
Reviewed-by: David Howells <dhowells@xxxxxxxxxx>
Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
index e0ce4276274be..933e12e3a55c7 100644
--- a/net/sunrpc/svcsock.c
+++ b/net/sunrpc/svcsock.c
@@ -1216,15 +1216,6 @@ static int svc_tcp_recvfrom(struct svc_rqst *rqstp)
* MSG_SPLICE_PAGES is used exclusively to reduce the number of
* copy operations in this path. Therefore the caller must ensure
* that the pages backing @xdr are unchanging.
- *
- * Note that the send is non-blocking. The caller has incremented
- * the reference count on each page backing the RPC message, and
- * the network layer will "put" these pages when transmission is
- * complete.
- *
- * This is safe for our RPC services because the memory backing
- * the head and tail components is never kmalloc'd. These always
- * come from pages in the svc_rqst::rq_pages array.
*/
static int svc_tcp_sendmsg(struct svc_sock *svsk, struct svc_rqst *rqstp,
rpc_fraghdr marker, unsigned int *sentp)
@@ -1254,6 +1245,7 @@ static int svc_tcp_sendmsg(struct svc_sock *svsk, struct svc_rqst *rqstp,
iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, rqstp->rq_bvec,
1 + count, sizeof(marker) + rqstp->rq_res.len);
ret = sock_sendmsg(svsk->sk_sock, &msg);
+ page_frag_free(buf);
if (ret < 0)
return ret;
*sentp += ret;
