[PATCH bpf-next v3 2/5] nbd: trace sending nbd requests

Matt Mullins
2019-04-19T21:06:01Z

This adds a tracepoint that can both observe the nbd request being sent
to the server, as well as modify that request , e.g., setting a flag in
the request that will cause the server to collect detailed tracing data.

The struct request * being handled is included to permit correlation
with the block tracepoints.

Signed-off-by: Matt Mullins <mmullins@fb.com>
---
MAINTAINERS | 1 +
drivers/block/nbd.c | 5 ++++
include/trace/events/nbd.h | 56 ++++++++++++++++++++++++++++++++++++++
3 files changed, 62 insertions(+)
create mode 100644 include/trace/events/nbd.h

diff --git a/MAINTAINERS b/MAINTAINERS
index e17ebf70b548..6db583d2b0ea 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -10737,6 +10737,7 @@ L: linux-block@vger.kernel.org
L: nbd@other.debian.org
F: Documentation/blockdev/nbd.txt
F: drivers/block/nbd.c
+F: include/trace/events/nbd.h
F: include/uapi/linux/nbd.h

NETWORK DROP MONITOR
diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 90ba9f4c03f3..7393d04d255c 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -44,6 +44,9 @@
#include <linux/nbd-netlink.h>
#include <net/genetlink.h>

+#define CREATE_TRACE_POINTS
+#include <trace/events/nbd.h>
+
static DEFINE_IDR(nbd_index_idr);
static DEFINE_MUTEX(nbd_index_mutex);
static int nbd_total_devices = 0;
@@ -526,6 +529,8 @@ static int nbd_send_cmd(struct nbd_device *nbd, struct nbd_cmd *cmd, int index)
handle = nbd_cmd_handle(cmd);
memcpy(request.handle, &handle, sizeof(handle));

+ trace_nbd_send_request(&request, nbd->index, blk_mq_rq_from_pdu(cmd));
+
dev_dbg(nbd_to_dev(nbd), "request %p: sending control (%s@%llu,%uB)\n",
req, nbdcmd_to_ascii(type),
(unsigned long long)blk_rq_pos(req) << 9, blk_rq_bytes(req));
diff --git a/include/trace/events/nbd.h b/include/trace/events/nbd.h
new file mode 100644
index 000000000000..5928255ed02e
--- /dev/null
+++ b/include/trace/events/nbd.h
@@ -0,0 +1,56 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM nbd
+
+#if !defined(_TRACE_NBD_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_NBD_H
+
+#include <linux/tracepoint.h>
+
+DECLARE_EVENT_CLASS(nbd_send_request,
+
+ TP_PROTO(struct nbd_request *nbd_request, int index,
+ struct request *rq),
+
+ TP_ARGS(nbd_request, index, rq),
+
+ TP_STRUCT__entry(
+ __field(struct nbd_request *, nbd_request)
+ __field(u64, dev_index)
+ __field(struct request *, request)
+ ),
+
+ TP_fast_assign(
+ __entry->nbd_request = 0;
+ __entry->dev_index = index;
+ __entry->request = rq;
+ ),
+
+ TP_printk("nbd%lld: request %p", __entry->dev_index, __entry->request)
+);
+
+#ifdef DEFINE_EVENT_WRITABLE
+#undef NBD_DEFINE_EVENT
+#define NBD_DEFINE_EVENT(template, call, proto, args, size) \
+ DEFINE_EVENT_WRITABLE(template, call, PARAMS(proto), \
+ PARAMS(args), size)
+#else
+#undef NBD_DEFINE_EVENT
+#define NBD_DEFINE_EVENT(template, call, proto, args, size) \
+ DEFINE_EVENT(template, call, PARAMS(proto), PARAMS(args))
+#endif
+
+NBD_DEFINE_EVENT(nbd_send_request, nbd_send_request,
+
+ TP_PROTO(struct nbd_request *nbd_request, int index,
+ struct request *rq),
+
+ TP_ARGS(nbd_request, index, rq),
+
+ sizeof(struct nbd_request)
+);
+
+#endif
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>
--
2.17.1