netfs: Trace refcounting on the netfs_io_subrequest struct

Add refcount tracing for the netfs_io_subrequest structure.

Changes
=======
ver #3)
 - Switch 'W=' to 'R=' in the traceline to match other request debug IDs.

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
cc: linux-cachefs@redhat.com

Link: https://lore.kernel.org/r/164622998584.3564931.5052255990645723639.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/164678202603.1200972.14726007419792315578.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/164692901860.2099075.4845820886851239935.stgit@warthog.procyon.org.uk/ # v3

2 files changed, 47 insertions, 1 deletions

diff --git a/include/linux/netfs.h b/include/linux/netfs.h
index 541aebe828f3..c702bd8ea8da 100644
--- a/include/linux/netfs.h
+++ b/include/linux/netfs.h
@@ -18,6 +18,8 @@
 #include <linux/fs.h>
 #include <linux/pagemap.h>
 
+enum netfs_sreq_ref_trace;
+
 /*
  * Overload PG_private_2 to give us PG_fscache - this is used to indicate that
  * a page is currently backed by a local disk cache
@@ -136,7 +138,7 @@ struct netfs_io_subrequest {
 	loff_t			start;		/* Where to start the I/O */
 	size_t			len;		/* Size of the I/O */
 	size_t			transferred;	/* Amount of data transferred */
-	refcount_t		usage;
+	refcount_t		ref;
 	short			error;		/* 0 or error that occurred */
 	unsigned short		debug_index;	/* Index in list (for debugging output) */
 	enum netfs_io_source	source;		/* Where to read from/write to */
@@ -268,6 +270,10 @@ extern int netfs_write_begin(struct file *, struct address_space *,
 			     void *);
 
 extern void netfs_subreq_terminated(struct netfs_io_subrequest *, ssize_t, bool);
+extern void netfs_get_subrequest(struct netfs_io_subrequest *subreq,
+				 enum netfs_sreq_ref_trace what);
+extern void netfs_put_subrequest(struct netfs_io_subrequest *subreq,
+				 bool was_async, enum netfs_sreq_ref_trace what);
 extern void netfs_stats_show(struct seq_file *);
 
 #endif /* _LINUX_NETFS_H */
diff --git a/include/trace/events/netfs.h b/include/trace/events/netfs.h
index e35a5ce52eb5..dcea5e888fd0 100644
--- a/include/trace/events/netfs.h
+++ b/include/trace/events/netfs.h
@@ -64,6 +64,17 @@
 	EM(netfs_rreq_trace_put_subreq,		"PUT SUBREQ ")	\
 	E_(netfs_rreq_trace_new,		"NEW        ")
 
+#define netfs_sreq_ref_traces					\
+	EM(netfs_sreq_trace_get_copy_to_cache,	"GET COPY2C ")	\
+	EM(netfs_sreq_trace_get_resubmit,	"GET RESUBMIT")	\
+	EM(netfs_sreq_trace_get_short_read,	"GET SHORTRD")	\
+	EM(netfs_sreq_trace_new,		"NEW        ")	\
+	EM(netfs_sreq_trace_put_clear,		"PUT CLEAR  ")	\
+	EM(netfs_sreq_trace_put_failed,		"PUT FAILED ")	\
+	EM(netfs_sreq_trace_put_merged,		"PUT MERGED ")	\
+	EM(netfs_sreq_trace_put_no_copy,	"PUT NO COPY")	\
+	E_(netfs_sreq_trace_put_terminated,	"PUT TERM   ")
+
 #ifndef __NETFS_DECLARE_TRACE_ENUMS_ONCE_ONLY
 #define __NETFS_DECLARE_TRACE_ENUMS_ONCE_ONLY
 
@@ -77,6 +88,7 @@ enum netfs_rreq_trace { netfs_rreq_traces } __mode(byte);
 enum netfs_sreq_trace { netfs_sreq_traces } __mode(byte);
 enum netfs_failure { netfs_failures } __mode(byte);
 enum netfs_rreq_ref_trace { netfs_rreq_ref_traces } __mode(byte);
+enum netfs_sreq_ref_trace { netfs_sreq_ref_traces } __mode(byte);
 
 #endif
 
@@ -94,6 +106,7 @@ netfs_sreq_sources;
 netfs_sreq_traces;
 netfs_failures;
 netfs_rreq_ref_traces;
+netfs_sreq_ref_traces;
 
 /*
  * Now redefine the EM() and E_() macros to map the enums to the strings that
@@ -264,6 +277,33 @@ TRACE_EVENT(netfs_rreq_ref,
 		      __entry->ref)
 	    );
 
+TRACE_EVENT(netfs_sreq_ref,
+	    TP_PROTO(unsigned int rreq_debug_id, unsigned int subreq_debug_index,
+		     int ref, enum netfs_sreq_ref_trace what),
+
+	    TP_ARGS(rreq_debug_id, subreq_debug_index, ref, what),
+
+	    TP_STRUCT__entry(
+		    __field(unsigned int,		rreq		)
+		    __field(unsigned int,		subreq		)
+		    __field(int,			ref		)
+		    __field(enum netfs_sreq_ref_trace,	what		)
+			     ),
+
+	    TP_fast_assign(
+		    __entry->rreq	= rreq_debug_id;
+		    __entry->subreq	= subreq_debug_index;
+		    __entry->ref	= ref;
+		    __entry->what	= what;
+			   ),
+
+	    TP_printk("R=%08x[%x] %s r=%u",
+		      __entry->rreq,
+		      __entry->subreq,
+		      __print_symbolic(__entry->what, netfs_sreq_ref_traces),
+		      __entry->ref)
+	    );
+
 #undef EM
 #undef E_
 #endif /* _TRACE_NETFS_H */