[PATCH 40/46] perf tools: Record fd into perf_mmap

[Wang Nan]

Add a fd field into perf_mmap so perf can backtrack the fd from mmap.
This feature will be used to toggle overwrite ring buffers.

Signed-off-by: Wang Nan <wangnan0@xxxxxxxxxx>
Signed-off-by: He Kuang <hekuang@xxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Zefan Li <lizefan@xxxxxxxxxx>
Cc: pi3orama@xxxxxxx
---
 tools/perf/util/evlist.c | 15 +++++++++++++--
 tools/perf/util/evlist.h |  1 +
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index 7877061..c72905d 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -868,6 +868,7 @@ static void __perf_evlist__munmap(struct perf_evlist *evlist, int idx)
 	if (evlist->mmap[idx].base != NULL) {
 		munmap(evlist->mmap[idx].base, evlist->mmap_len);
 		evlist->mmap[idx].base = NULL;
+		evlist->mmap[idx].fd = -1;
 		atomic_set(&evlist->mmap[idx].refcnt, 0);
 	}
 	auxtrace_mmap__munmap(&evlist->mmap[idx].auxtrace_mmap);
@@ -903,7 +904,7 @@ void perf_evlist__munmap(struct perf_evlist *evlist)
 
 static int perf_evlist__alloc_mmap(struct perf_evlist *evlist)
 {
-	int total_mmaps;
+	int total_mmaps, i;
 
 	evlist->nr_mmaps = cpu_map__nr(evlist->cpus);
 	if (cpu_map__empty(evlist->cpus))
@@ -914,7 +915,12 @@ static int perf_evlist__alloc_mmap(struct perf_evlist *evlist)
 		return -EINVAL;
 
 	evlist->mmap = zalloc(total_mmaps * sizeof(struct perf_mmap));
-	return evlist->mmap != NULL ? 0 : -ENOMEM;
+	if (!evlist->mmap)
+		return -ENOMEM;
+
+	for (i = 0; i < total_mmaps; i++)
+		evlist->mmap[i].fd = -1;
+	return 0;
 }
 
 struct mmap_params {
@@ -934,6 +940,10 @@ static int __perf_evlist__mmap(struct perf_evlist *evlist, int idx,
 	if (!perf_evlist__channel_check(evlist, channel, RDONLY))
 		prot |= PROT_WRITE;
 
+	if (evlist->mmap[idx].fd >= 0) {
+		pr_err("idx %d already mapped\n", idx);
+		return -1;
+	}
 	/*
 	 * The last one will be done at perf_evlist__mmap_consume(), so that we
 	 * make sure we don't prevent tools from consuming every last event in
@@ -958,6 +968,7 @@ static int __perf_evlist__mmap(struct perf_evlist *evlist, int idx,
 		evlist->mmap[idx].base = NULL;
 		return -1;
 	}
+	evlist->mmap[idx].fd = fd;
 
 	if (auxtrace_mmap__mmap(&evlist->mmap[idx].auxtrace_mmap,
 				&mp->auxtrace_mp, evlist->mmap[idx].base, fd))
diff --git a/tools/perf/util/evlist.h b/tools/perf/util/evlist.h
index 321224c..bc6d787 100644
--- a/tools/perf/util/evlist.h
+++ b/tools/perf/util/evlist.h
@@ -35,6 +35,7 @@ enum perf_evlist_mmap_flag {
 struct perf_mmap {
 	void		 *base;
 	int		 mask;
+	int		 fd;
 	atomic_t	 refcnt;
 	u64		 prev;
 	struct auxtrace_mmap auxtrace_mmap;
-- 
1.8.3.4