From: Mark Nelson <mnelson@redhat.com>
Date: Mon, 7 Aug 2017 14:23:12 +0000 (-0500)
Subject: os/bluestore:  clearer comments, not slower code.
X-Git-Tag: v12.1.3~2
X-Git-Url: http://git-server-git.apps.pok.os.sepia.ceph.com/?a=commitdiff_plain;h=724aaff467f7228a2b0af8f8adda505d504d3610;p=ceph.git

os/bluestore:  clearer comments, not slower code.

Signed-off-by: Mark Nelson <mnelson@redhat.com>
(cherry picked from commit da92220d9d6936ef1aa19333038b7a1d982485a4)
---

diff --git a/src/os/bluestore/BitmapFreelistManager.cc b/src/os/bluestore/BitmapFreelistManager.cc
index d3fdbb71a8d..075d3eff6ef 100644
--- a/src/os/bluestore/BitmapFreelistManager.cc
+++ b/src/os/bluestore/BitmapFreelistManager.cc
@@ -191,10 +191,10 @@ int get_next_clear_bit(bufferlist& bl, int start)
   const char *p = bl.c_str();
   int bits = bl.length() << 3;
   while (start < bits) {
-    int which_byte = start / 8;
-    int which_bit = start % 8;
-    unsigned char byte_mask = 1 << which_bit;
-    if ((p[which_byte] & byte_mask) == 0) {
+    // byte = start / 8 (or start >> 3)
+    // bit = start % 8 (or start & 7)
+    unsigned char byte_mask = 1 << (start & 7);
+    if ((p[start >> 3] & byte_mask) == 0) {
       return start;
     }
     ++start;