[tip:perf/core] perf mmap: Store mmap scope in struct perf_mmap()

[tip-bot for Kan Liang]

Commit-ID:  4fda3459e3c2e5ca35d304646aeeb811242537b2
Gitweb:     https://git.kernel.org/tip/4fda3459e3c2e5ca35d304646aeeb811242537b2
Author:     Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
AuthorDate: Tue, 6 Mar 2018 10:36:01 -0500
Committer:  Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
CommitDate: Thu, 8 Mar 2018 10:05:50 -0300

perf mmap: Store mmap scope in struct perf_mmap()

There is too much boilerplate in the perf_mmap__read*() interfaces.

The 'start' and 'end' variables should be stored in struct perf_mmap at
initialization. They will be used later.

The old 'startp' and 'endp' pointers are used by perf_mmap__read_event()
now.  They cannot be removed. So the old 'startp/endp' and new
'md->start/md->end' will exist simultaneously now.  The old one will be
removed later.

Signed-off-by: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
Suggested-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Acked-by: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Wang Nan <wangnan0@xxxxxxxxxx>
Link: http://lkml.kernel.org/r/1520350567-80082-2-git-send-email-kan.liang@xxxxxxxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
 tools/perf/util/mmap.c | 12 ++++++++----
 tools/perf/util/mmap.h |  2 ++
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/tools/perf/util/mmap.c b/tools/perf/util/mmap.c
index 4f27c464ce0b..09acaf7392bb 100644
--- a/tools/perf/util/mmap.c
+++ b/tools/perf/util/mmap.c
@@ -250,13 +250,15 @@ int perf_mmap__read_init(struct perf_mmap *md, bool overwrite,
 
 	*startp = overwrite ? head : old;
 	*endp = overwrite ? old : head;
+	md->start = md->overwrite ? head : old;
+	md->end = md->overwrite ? old : head;
 
-	if (*startp == *endp)
+	if (md->start == md->end)
 		return -EAGAIN;
 
-	size = *endp - *startp;
+	size = md->end - md->start;
 	if (size > (unsigned long)(md->mask) + 1) {
-		if (!overwrite) {
+		if (!md->overwrite) {
 			WARN_ONCE(1, "failed to keep up with mmap data. (warn only once)\n");
 
 			md->prev = head;
@@ -268,8 +270,10 @@ int perf_mmap__read_init(struct perf_mmap *md, bool overwrite,
 		 * Backward ring buffer is full. We still have a chance to read
 		 * most of data from it.
 		 */
-		if (overwrite_rb_find_range(data, md->mask, head, startp, endp))
+		if (overwrite_rb_find_range(data, md->mask, head, &md->start, &md->end))
 			return -EINVAL;
+		*startp = md->start;
+		*endp = md->end;
 	}
 
 	return 0;
diff --git a/tools/perf/util/mmap.h b/tools/perf/util/mmap.h
index 71137977af28..9359e934ab14 100644
--- a/tools/perf/util/mmap.h
+++ b/tools/perf/util/mmap.h
@@ -20,6 +20,8 @@ struct perf_mmap {
 	int		 fd;
 	refcount_t	 refcnt;
 	u64		 prev;
+	u64		 start;
+	u64		 end;
 	bool		 overwrite;
 	struct auxtrace_mmap auxtrace_mmap;
 	char		 event_copy[PERF_SAMPLE_MAX_SIZE] __aligned(8);