shard_id_t: change NO_SHARD to sort before 0 (min instead of max)

The min ghobject has shard NO_SHARD, and is the default constructed value.
That initial value is assumed in uncounted ways across the code base when
users do

  ghobject_t foo;
  foo.this = that;

such that changing it is dangerous.  It is safer to change the shard_id_t
sort order such that NO_SHARD is signed instead of unsigned.  The value
doesn't actually change (still 0xff), but the sorting does.  Note that
only a single comparison triggers a signed/unsigned warning from this
change, and it assumes that the shard is not NO_SHARD (ec pool) and we
case it to preserve the old behavior anyway.

In PGBackend we change the minimum value for the objects_list_partial()
method to start with NO_SHARD.

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

1 files changed, 1 insertions, 1 deletions

diff --git a/src/osd/PGBackend.cc b/src/osd/PGBackend.cc
index 319110cd0dd..64423dee1f3 100644
--- a/src/osd/PGBackend.cc
+++ b/src/osd/PGBackend.cc
@@ -109,7 +109,7 @@ int PGBackend::objects_list_partial(
   // make sure the result list has the marker object (
   // it might have multiple generations though, which would
   // be filtered).
-  ghobject_t _next(begin, 0, shard_id_t(0));
+  ghobject_t _next(begin, 0, shard_id_t::NO_SHARD);
   ls->reserve(max);
   int r = 0;
   while (!_next.is_max() && ls->size() < (unsigned)min) {