nbd: trace sending nbd requests

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>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/MAINTAINERS b/MAINTAINERS
index 72dfb80e87216498fecfa30e60e21920f3ee388f..025c6d27789e57c3180472b6a68d956e1377609a 100644 (file)
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -10741,6 +10741,7 @@ 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 92b8aafb8bb4c693f80da233289a01387552222a..24cc10d1f0b443ac10f1914f07b36213482f5d41 100644 (file)
--- 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 (file)
index 0000000..5928255
--- /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>