[PATCH 05/06] 9p fid refcount: add a 9p_fid_ref tracepoint

Dominique Martinet
2022-06-12T08:54:37Z

Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>
---

This is the first time I add a tracepoint, so if anyone has time to
check I didn't make something too stupid please have a look.
I've mostly copied from netfs'.

Also, a question if someone has time: I'd have liked to use the
tracepoint in static inline wrappers for getref/putref, but it's not
good to add the tracepoints to a .h, right?
Especially with the CREATE_TRACE_POINTS macro...
How do people usually go about that, just bite the bullet and make it
a real function?

include/trace/events/9p.h | 48 +++++++++++++++++++++++++++++++++++++++
net/9p/client.c | 9 +++++++-
2 files changed, 56 insertions(+), 1 deletion(-)

diff --git a/include/trace/events/9p.h b/include/trace/events/9p.h
index 78c5608a1648..4dfa6d7f83ba 100644
--- a/include/trace/events/9p.h
+++ b/include/trace/events/9p.h
@@ -77,6 +77,13 @@
EM( P9_TWSTAT, "P9_TWSTAT" ) \
EMe(P9_RWSTAT, "P9_RWSTAT" )

+
+#define P9_FID_REFTYPE \
+ EM( P9_FID_REF_CREATE, "create " ) \
+ EM( P9_FID_REF_GET, "get " ) \
+ EM( P9_FID_REF_PUT, "put " ) \
+ EMe(P9_FID_REF_DESTROY, "destroy" )
+
/* Define EM() to export the enums to userspace via TRACE_DEFINE_ENUM() */
#undef EM
#undef EMe
@@ -84,6 +91,21 @@
#define EMe(a, b) TRACE_DEFINE_ENUM(a);

P9_MSG_T
+P9_FID_REFTYPE
+
+/* And also use EM/EMe to define helper enums -- once */
+#ifndef __9P_DECLARE_TRACE_ENUMS_ONLY_ONCE
+#define __9P_DECLARE_TRACE_ENUMS_ONLY_ONCE
+#undef EM
+#undef EMe
+#define EM(a, b) a,
+#define EMe(a, b) a
+
+enum p9_fid_reftype {
+ P9_FID_REFTYPE
+} __mode(byte);
+
+#endif

/*
* Now redefine the EM() and EMe() macros to map the enums to the strings
@@ -96,6 +118,8 @@ P9_MSG_T

#define show_9p_op(type) \
__print_symbolic(type, P9_MSG_T)
+#define show_9p_fid_reftype(type) \
+ __print_symbolic(type, P9_FID_REFTYPE)

TRACE_EVENT(9p_client_req,
TP_PROTO(struct p9_client *clnt, int8_t type, int tag),
@@ -168,6 +192,30 @@ TRACE_EVENT(9p_protocol_dump,
__entry->tag, 0, __entry->line, 16, __entry->line + 16)
);

+
+TRACE_EVENT(9p_fid_ref,
+ TP_PROTO(struct p9_fid *fid, __u8 type),
+
+ TP_ARGS(fid, type),
+
+ TP_STRUCT__entry(
+ __field( int, fid )
+ __field( int, refcount )
+ __field( __u8, type )
+ ),
+
+ TP_fast_assign(
+ __entry->fid = fid->fid;
+ __entry->refcount = refcount_read(&fid->count);
+ __entry->type = type;
+ ),
+
+ TP_printk("%s fid %d, refcount %d",
+ show_9p_fid_reftype(__entry->type),
+ __entry->fid, __entry->refcount)
+);
+
+
#endif /* _TRACE_9P_H */

/* This part must be outside protection */
diff --git a/net/9p/client.c b/net/9p/client.c
index 5531b31e0fb2..fdeeda0a811d 100644
--- a/net/9p/client.c
+++ b/net/9p/client.c
@@ -907,8 +907,10 @@ static struct p9_fid *p9_fid_create(struct p9_client *clnt)
GFP_NOWAIT);
spin_unlock_irq(&clnt->lock);
idr_preload_end();
- if (!ret)
+ if (!ret) {
+ trace_9p_fid_ref(fid, P9_FID_REF_CREATE);
return fid;
+ }

kfree(fid);
return NULL;
@@ -920,6 +922,7 @@ static void p9_fid_destroy(struct p9_fid *fid)
unsigned long flags;

p9_debug(P9_DEBUG_FID, "fid %d\n", fid->fid);
+ trace_9p_fid_ref(fid, P9_FID_REF_DESTROY);
clnt = fid->clnt;
spin_lock_irqsave(&clnt->lock, flags);
idr_remove(&clnt->fids, fid->fid);
@@ -932,6 +935,8 @@ static void p9_fid_destroy(struct p9_fid *fid)
* because trace_* functions can't be used there easily
*/
struct p9_fid *p9_fid_get(struct p9_fid *fid) {
+ trace_9p_fid_ref(fid, P9_FID_REF_GET);
+
refcount_inc(&fid->count);

return fid;
@@ -941,6 +946,8 @@ int p9_fid_put(struct p9_fid *fid) {
if (!fid || IS_ERR(fid))
return 0;

+ trace_9p_fid_ref(fid, P9_FID_REF_PUT);
+
if (!refcount_dec_and_test(&fid->count))
return 0;

--
2.35.1