journaler: fix waiting_for_zero clearing

Clear this flag only if we know no subsequent flushes could be waiting on
a prezero operation.

Fixes MDS journaling hang under heavy journal load.

Signed-off-by: Sage Weil <sage.weil@dreamhost.com>

diff --git a/src/osdc/Journaler.cc b/src/osdc/Journaler.cc
index 441d27300681cd0efd9f0021bc46dfebfe9264bf..bbae4e2450366cbdf6ec0cbfadc3f88bba2c25d0 100644 (file)
--- a/src/osdc/Journaler.cc
+++ b/src/osdc/Journaler.cc
@@ -667,7 +667,8 @@ void Journaler::_prezeroed(int r, uint64_t start, uint64_t len)
     }
 
     if (waiting_for_zero) {
-      waiting_for_zero = false;
+      if (prezero_pos > write_pos)
+       waiting_for_zero = false;
       _do_flush();
     }
   } else {