osd: check_full_status() remove bogus comment and use equivalent computation

We actually compute kb_used as the kb - kb_avail.  We don't have the
statfs() system call issue of non-privileged f_bavail vs f_bfree.  It
was assumed that used was really like (blocks - f_bfree).  It is not.

Signed-off-by: David Zafman <dzafman@redhat.com>

diff --git a/src/osd/OSD.cc b/src/osd/OSD.cc
index e39330e092379e574c75872df45f827aee6443de..c8031826f4e6f44eea8c62df3f5fababd73e7506 100644 (file)
--- a/src/osd/OSD.cc
+++ b/src/osd/OSD.cc
@@ -716,13 +716,7 @@ void OSDService::check_full_status(const osd_stat_t &osd_stat)
 {
   Mutex::Locker l(full_status_lock);
 
-  // We base ratio on kb_avail rather than kb_used because they can
-  // differ significantly e.g. on btrfs volumes with a large number of
-  // chunks reserved for metadata, and for our purposes (avoiding
-  // completely filling the disk) it's far more important to know how
-  // much space is available to use than how much we've already used.
-  float ratio = ((float)(osd_stat.kb - osd_stat.kb_avail)) /
-    ((float)osd_stat.kb);
+  float ratio = ((float)osd_stat.kb_used) / ((float)osd_stat.kb);
   cur_ratio = ratio;
 
   // The OSDMap ratios take precendence.  So if the failsafe is .95 and