osd/PrimaryLogPG.cc: reassign size only when object size > truncate_size

Before setting size equal to op.extent.truncate_size, we need to check
if the size of the object is greater than the truncate_size. We do not
need to set size to op.extent.truncate_size, in the case where the size of
the object is less than op.extent.truncate_size.

Without this change, we were always setting size =
op.extent.truncate_size, when (seq < op.extent.truncate_seq) and
(op.extent.offset + op.extent.length > op.extent.truncate_size), were both
true. This ended up in:

1. overestimating the size of the object
2. not considering the correct size of the object, for
   the later checks, which calculate op.extent.length for the read ops
3. causing crashes when trying to read more data than what was present

Fixes: http://tracker.ceph.com/issues/21931
Fixes: http://tracker.ceph.com/issues/22330
Signed-off-by: Neha Ojha <nojha@redhat.com>
(cherry picked from commit 76c57810ee2346c392834206331aacb0faaa5b54)

diff --git a/src/osd/PrimaryLogPG.cc b/src/osd/PrimaryLogPG.cc
index 743d27bc21986b682dd3042fd38ed65c9ba66768..674efddbf0e4c7c78e72280a7678556d4eb9fe5e 100644 (file)
--- a/src/osd/PrimaryLogPG.cc
+++ b/src/osd/PrimaryLogPG.cc
@@ -4858,7 +4858,8 @@ int PrimaryLogPG::do_read(OpContext *ctx, OSDOp& osd_op) {
 
   // are we beyond truncate_size?
   if ( (seq < op.extent.truncate_seq) &&
-       (op.extent.offset + op.extent.length > op.extent.truncate_size) )
+       (op.extent.offset + op.extent.length > op.extent.truncate_size) &&
+       (size > op.extent.truncate_size) )
     size = op.extent.truncate_size;
 
   if (op.extent.length == 0) //length is zero mean read the whole object