From: Chuck Lever <chuck.lever@oracle.com>
Date: Fri, 27 Jul 2018 11:18:54 -0400
Subject: svcrdma: Avoid releasing a page in svc_xprt_release()
Patch-mainline: v4.19-rc1
Git-commit: a53d5cb0646a12586ae45c892c7a411d47ee1a1d
References: bsc#1103992 FATE#326009
svc_xprt_release() invokes svc_free_res_pages(), which releases
pages between rq_respages and rq_next_page.
Historically, the RPC/RDMA transport has set these two pointers to
be different by one, which means:
- one page gets released when svc_recv returns 0. This normally
happens whenever one or more RDMA Reads need to be dispatched to
complete construction of an RPC Call.
- one page gets released after every call to svc_send.
In both cases, this released page is immediately refilled by
svc_alloc_arg. There does not seem to be a reason for releasing this
page.
To avoid this unnecessary memory allocator traffic, set rq_next_page
more carefully.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
net/sunrpc/xprtrdma/svc_rdma_recvfrom.c | 9 ++++++---
net/sunrpc/xprtrdma/svc_rdma_sendto.c | 4 +++-
2 files changed, 9 insertions(+), 4 deletions(-)
--- a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
@@ -365,9 +365,6 @@ static void svc_rdma_build_arg_xdr(struc
arg->page_base = 0;
arg->buflen = ctxt->rc_byte_len;
arg->len = ctxt->rc_byte_len;
-
- rqstp->rq_respages = &rqstp->rq_pages[0];
- rqstp->rq_next_page = rqstp->rq_respages + 1;
}
/* This accommodates the largest possible Write chunk,
@@ -729,6 +726,12 @@ int svc_rdma_recvfrom(struct svc_rqst *r
svc_rdma_build_arg_xdr(rqstp, ctxt);
+ /* Prevent svc_xprt_release from releasing pages in rq_pages
+ * if we return 0 or an error.
+ */
+ rqstp->rq_respages = rqstp->rq_pages;
+ rqstp->rq_next_page = rqstp->rq_respages;
+
p = (__be32 *)rqstp->rq_arg.head[0].iov_base;
ret = svc_rdma_xdr_decode_req(&rqstp->rq_arg);
if (ret < 0)
--- a/net/sunrpc/xprtrdma/svc_rdma_sendto.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_sendto.c
@@ -656,7 +656,9 @@ static void svc_rdma_save_io_pages(struc
ctxt->sc_pages[i] = rqstp->rq_respages[i];
rqstp->rq_respages[i] = NULL;
}
- rqstp->rq_next_page = rqstp->rq_respages + 1;
+
+ /* Prevent svc_xprt_release from releasing pages in rq_pages */
+ rqstp->rq_next_page = rqstp->rq_respages;
}
/* Prepare the portion of the RPC Reply that will be transmitted