osd/scrub: clean-up scrub-store IDs generation

The Scrub Store IDs (used to identify OMAP entries used for storing
object-specific error data) are generated by attaching some prefix to
the text representation of virtual (invented) hobjects.

This commit cleans up the code by moving the name generation
process (creating temporary un-needed objects, then
extracting the to_str() representation of their identity)
into separate functions.

Signed-off-by: Ronen Friedman <[email protected]>

Author: ronen-fr

src/osd/scrubber/ScrubStore.cc

@@ -15,60 +15,65 @@ using std::vector;
 using ceph::bufferlist;
 
 namespace {
+
+/// the 'to_str()' representation of an hobject, if created with the specific
+/// parameters, prefixed with 'prefix'.
+std::string virtual_hobject_w_prefix(std::string_view prefix,
+                                     const std::string& key,
+                                     snapid_t snap,
+                                     uint32_t hash,
+                                     int64_t pool)
+{
+  return fmt::format("{}_{}", prefix,
+                     hobject_t(object_t(), key, snap, hash, pool, "").to_str());
+}
+
+/// the 'to_str()' representation of an hobject, if created with the specific
+/// parameters, prefixed with 'prefix'.
+std::string virtual_hobject_w_prefix(std::string_view prefix,
+                                     const librados::object_id_t& oid,
+                                     uint32_t hash,
+                                     int64_t pool) {
+  return fmt::format("{}_{}", prefix,
+                     hobject_t(object_t{oid.name}, oid.locator, oid.snap, hash,
+                               pool, oid.nspace)
+                         .to_str());
+}
+
 string first_object_key(int64_t pool)
 {
-  auto hoid = hobject_t(object_t(), "", CEPH_NOSNAP, 0x00000000, pool, "");
-  hoid.build_hash_cache();
-  return "SCRUB_OBJ_" + hoid.to_str();
+  return virtual_hobject_w_prefix("SCRUB_OBJ", "", CEPH_NOSNAP, 0x00000000,
+                                  pool);
 }
 
 // the object_key should be unique across pools
 string to_object_key(int64_t pool, const librados::object_id_t& oid)
 {
-  auto hoid = hobject_t(object_t(oid.name),
-			oid.locator, // key
-			oid.snap,
-			0,		// hash
-			pool,
-			oid.nspace);
-  hoid.build_hash_cache();
-  return "SCRUB_OBJ_" + hoid.to_str();
+  return virtual_hobject_w_prefix("SCRUB_OBJ", oid, 0x00000000, pool);
 }
 
 string last_object_key(int64_t pool)
 {
-  auto hoid = hobject_t(object_t(), "", CEPH_NOSNAP, 0xffffffff, pool, "");
-  hoid.build_hash_cache();
-  return "SCRUB_OBJ_" + hoid.to_str();
+  return virtual_hobject_w_prefix("SCRUB_OBJ", "", CEPH_NOSNAP, 0xffffffff,
+                                  pool);
 }
 
 string first_snap_key(int64_t pool)
 {
   // scrub object is per spg_t object, so we can misuse the hash (pg.seed) for
   // representing the minimal and maximum keys. and this relies on how
   // hobject_t::to_str() works: hex(pool).hex(revhash).
-  auto hoid = hobject_t(object_t(), "", 0, 0x00000000, pool, "");
-  hoid.build_hash_cache();
-  return "SCRUB_SS_" + hoid.to_str();
+  return virtual_hobject_w_prefix("SCRUB_SS", "", 0, 0x00000000, pool);
 }
 
 string to_snap_key(int64_t pool, const librados::object_id_t& oid)
 {
-  auto hoid = hobject_t(object_t(oid.name),
-			oid.locator, // key
-			oid.snap,
-			0x77777777, // hash
-			pool,
-			oid.nspace);
-  hoid.build_hash_cache();
-  return "SCRUB_SS_" + hoid.to_str();
+  return virtual_hobject_w_prefix("SCRUB_SS", oid, 0x77777777, pool);
 }
 
 string last_snap_key(int64_t pool)
 {
-  auto hoid = hobject_t(object_t(), "", 0, 0xffffffff, pool, "");
-  hoid.build_hash_cache();
-  return "SCRUB_SS_" + hoid.to_str();
+  return virtual_hobject_w_prefix("SCRUB_SS", "", 0, 0xffffffff, pool);
 }
 
 }  // namespace