[PATCH V2 2/8] perf mmap: Store mmap scope in struct perf_mmap

[kan . liang]

From: Kan Liang <kan.li...@linux.intel.com>

There are too many boilerplates for the perf_mmap__read*() interfaces.

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

The old 'startp' and 'endp' 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.li...@linux.intel.com>
---

Changes since V1:
 - Using the 'overwrite' which set in previous patch
 - Add the reason of keeping old starp/end in the change log

 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 4f27c46..09acaf7 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 7113797..9359e93 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);
-- 
2.4.11