cachefiles: Add some subrequest tracepoints

Add some tracepoints into the cachefiles write paths.

Signed-off-by: David Howells <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
cc: [e-mail]
Signed-off-by: Christian Brauner <[e-mail]>

fs/cachefiles/io.c

···
 #include <linux/falloc.h>
 #include <linux/sched/mm.h>
 #include <trace/events/fscache.h>
+#include <trace/events/netfs.h>
 #include "internal.h"
 
 struct cachefiles_kiocb {
···
 	if (!fscache_wait_for_operation(cres, FSCACHE_WANT_WRITE)) {
 		if (term_func)
 			term_func(term_func_priv, -ENOBUFS, false);
+		trace_netfs_sreq(term_func_priv, netfs_sreq_trace_cache_nowrite);
 		return -ENOBUFS;
 	}
 
···
 		iov_iter_truncate(&subreq->io_iter, len);
 	}
 
+	trace_netfs_sreq(subreq, netfs_sreq_trace_cache_prepare);
 	cachefiles_begin_secure(cache, &saved_cred);
 	ret = __cachefiles_prepare_write(object, cachefiles_cres_file(cres),
 					 &start, &len, len, true);
···
 		return;
 	}
 
+	trace_netfs_sreq(subreq, netfs_sreq_trace_cache_write);
 	cachefiles_write(&subreq->rreq->cache_resources,
 			 subreq->start, &subreq->io_iter,
 			 netfs_write_subrequest_terminated, subreq);

include/trace/events/netfs.h

···
 #define netfs_sreq_traces					\
 	EM(netfs_sreq_trace_add_donations,	"+DON ")	\
 	EM(netfs_sreq_trace_added,		"ADD  ")	\
+	EM(netfs_sreq_trace_cache_nowrite,	"CA-NW")	\
+	EM(netfs_sreq_trace_cache_prepare,	"CA-PR")	\
+	EM(netfs_sreq_trace_cache_write,	"CA-WR")	\
 	EM(netfs_sreq_trace_clear,		"CLEAR")	\
 	EM(netfs_sreq_trace_discard,		"DSCRD")	\
 	EM(netfs_sreq_trace_donate_to_prev,	"DON-P")	\