netfs: Add a tracepoint to log the lifespan of folio_queue structs

Add a tracepoint to log the lifespan of folio_queue structs.  For tracing
illustrative purposes, folio_queues are tagged with the debug ID of
whatever they're related to (typically a netfs_io_request) and a debug ID
of their own.

Signed-off-by: David Howells <dhowells@redhat.com>
Link: https://lore.kernel.org/r/20241216204124.3752367-5-dhowells@redhat.com
cc: Jeff Layton <jlayton@kernel.org>
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>

3 files changed, 52 insertions, 7 deletions

diff --git a/include/linux/folio_queue.h b/include/linux/folio_queue.h
index 3abe614ef5f0..4d3f8074c137 100644
--- a/include/linux/folio_queue.h
+++ b/include/linux/folio_queue.h
@@ -37,16 +37,20 @@ struct folio_queue {
 #if PAGEVEC_SIZE > BITS_PER_LONG
 #error marks is not big enough
 #endif
+	unsigned int		rreq_id;
+	unsigned int		debug_id;
 };
 
 /**
  * folioq_init - Initialise a folio queue segment
  * @folioq: The segment to initialise
+ * @rreq_id: The request identifier to use in tracelines.
  *
- * Initialise a folio queue segment.  Note that the folio pointers are
- * left uninitialised.
+ * Initialise a folio queue segment and set an identifier to be used in traces.
+ *
+ * Note that the folio pointers are left uninitialised.
  */
-static inline void folioq_init(struct folio_queue *folioq)
+static inline void folioq_init(struct folio_queue *folioq, unsigned int rreq_id)
 {
 	folio_batch_init(&folioq->vec);
 	folioq->next = NULL;
@@ -54,6 +58,8 @@ static inline void folioq_init(struct folio_queue *folioq)
 	folioq->marks = 0;
 	folioq->marks2 = 0;
 	folioq->marks3 = 0;
+	folioq->rreq_id = rreq_id;
+	folioq->debug_id = 0;
 }
 
 /**
diff --git a/include/linux/netfs.h b/include/linux/netfs.h
index c69e0f02c30f..5b2f427f8e3e 100644
--- a/include/linux/netfs.h
+++ b/include/linux/netfs.h
@@ -455,8 +455,10 @@ int netfs_start_io_direct(struct inode *inode);
 void netfs_end_io_direct(struct inode *inode);
 
 /* Miscellaneous APIs. */
-struct folio_queue *netfs_folioq_alloc(gfp_t gfp);
-void netfs_folioq_free(struct folio_queue *folioq);
+struct folio_queue *netfs_folioq_alloc(unsigned int rreq_id, gfp_t gfp,
+				       unsigned int trace /*enum netfs_folioq_trace*/);
+void netfs_folioq_free(struct folio_queue *folioq,
+		       unsigned int trace /*enum netfs_trace_folioq*/);
 
 /**
  * netfs_inode - Get the netfs inode context from the inode
diff --git a/include/trace/events/netfs.h b/include/trace/events/netfs.h
index c3c309f8fbe1..50aa6745df95 100644
--- a/include/trace/events/netfs.h
+++ b/include/trace/events/netfs.h
@@ -191,6 +191,16 @@
 	EM(netfs_trace_donate_to_next,		"to-next")	\
 	E_(netfs_trace_donate_to_deferred_next,	"defer-next")
 
+#define netfs_folioq_traces					\
+	EM(netfs_trace_folioq_alloc_append_folio, "alloc-apf")	\
+	EM(netfs_trace_folioq_alloc_read_prep,	"alloc-r-prep")	\
+	EM(netfs_trace_folioq_alloc_read_prime,	"alloc-r-prime") \
+	EM(netfs_trace_folioq_alloc_read_sing,	"alloc-r-sing")	\
+	EM(netfs_trace_folioq_clear,		"clear")	\
+	EM(netfs_trace_folioq_delete,		"delete")	\
+	EM(netfs_trace_folioq_prep_write,	"prep-wr")	\
+	E_(netfs_trace_folioq_read_progress,	"r-progress")
+
 #ifndef __NETFS_DECLARE_TRACE_ENUMS_ONCE_ONLY
 #define __NETFS_DECLARE_TRACE_ENUMS_ONCE_ONLY
 
@@ -209,6 +219,7 @@ enum netfs_sreq_ref_trace { netfs_sreq_ref_traces } __mode(byte);
 enum netfs_folio_trace { netfs_folio_traces } __mode(byte);
 enum netfs_collect_contig_trace { netfs_collect_contig_traces } __mode(byte);
 enum netfs_donate_trace { netfs_donate_traces } __mode(byte);
+enum netfs_folioq_trace { netfs_folioq_traces } __mode(byte);
 
 #endif
 
@@ -232,6 +243,7 @@ netfs_sreq_ref_traces;
 netfs_folio_traces;
 netfs_collect_contig_traces;
 netfs_donate_traces;
+netfs_folioq_traces;
 
 /*
  * Now redefine the EM() and E_() macros to map the enums to the strings that
@@ -317,6 +329,7 @@ TRACE_EVENT(netfs_sreq,
 		    __field(unsigned short,		flags)
 		    __field(enum netfs_io_source,	source)
 		    __field(enum netfs_sreq_trace,	what)
+		    __field(u8,				slot)
 		    __field(size_t,			len)
 		    __field(size_t,			transferred)
 		    __field(loff_t,			start)
@@ -332,15 +345,16 @@ TRACE_EVENT(netfs_sreq,
 		    __entry->len	= sreq->len;
 		    __entry->transferred = sreq->transferred;
 		    __entry->start	= sreq->start;
+		    __entry->slot	= sreq->curr_folioq_slot;
 			   ),
 
-	    TP_printk("R=%08x[%x] %s %s f=%02x s=%llx %zx/%zx e=%d",
+	    TP_printk("R=%08x[%x] %s %s f=%02x s=%llx %zx/%zx s=%u e=%d",
 		      __entry->rreq, __entry->index,
 		      __print_symbolic(__entry->source, netfs_sreq_sources),
 		      __print_symbolic(__entry->what, netfs_sreq_traces),
 		      __entry->flags,
 		      __entry->start, __entry->transferred, __entry->len,
-		      __entry->error)
+		      __entry->slot, __entry->error)
 	    );
 
 TRACE_EVENT(netfs_failure,
@@ -745,6 +759,29 @@ TRACE_EVENT(netfs_donate,
 		      __entry->amount)
 	    );
 
+TRACE_EVENT(netfs_folioq,
+	    TP_PROTO(const struct folio_queue *fq,
+		     enum netfs_folioq_trace trace),
+
+	    TP_ARGS(fq, trace),
+
+	    TP_STRUCT__entry(
+		    __field(unsigned int,		rreq)
+		    __field(unsigned int,		id)
+		    __field(enum netfs_folioq_trace,	trace)
+			     ),
+
+	    TP_fast_assign(
+		    __entry->rreq	= fq ? fq->rreq_id : 0;
+		    __entry->id		= fq ? fq->debug_id : 0;
+		    __entry->trace	= trace;
+			   ),
+
+	    TP_printk("R=%08x fq=%x %s",
+		      __entry->rreq, __entry->id,
+		      __print_symbolic(__entry->trace, netfs_folioq_traces))
+	    );
+
 #undef EM
 #undef E_
 #endif /* _TRACE_NETFS_H */