cls/rgw: adding an entry to reshard queue has O_CREAT option

Adds the ability to prevent overwriting a reshard queue (log) entry
for a given bucket with a newer entry. This adds a flag to the op, so
it will either CREATE or make no changes. If an entry already exists
when this flag is set, -EEXIST will be returned.

This is a preparatory step to adding shard reduction to dynamic
resharding.

Signed-off-by: J. Eric Ivancich <ivancich@redhat.com>

4 files changed, 38 insertions, 9 deletions

diff --git a/src/cls/rgw/cls_rgw.cc b/src/cls/rgw/cls_rgw.cc
index 83c3b824c18..9ad1320e38a 100644
--- a/src/cls/rgw/cls_rgw.cc
+++ b/src/cls/rgw/cls_rgw.cc
@@ -4422,15 +4422,31 @@ static int rgw_reshard_add(cls_method_context_t hctx, bufferlist *in, bufferlist
     return -EINVAL;
   }
 
-
-  string key;
+  std::string key;
   op.entry.get_key(&key);
 
+  int ret;
   bufferlist bl;
+
+  if (op.create_only) {
+    ret = cls_cxx_map_get_val(hctx, key, &bl);
+    if (ret == 0) {
+      // entry already exists; make no changes
+      return -EEXIST;
+    } else if (ret != -ENOENT) {
+      CLS_ERR("error accessing reshard queue for %s with key %s",
+	      op.entry.bucket_name.c_str(), key.c_str());
+      return ret;
+    }
+
+    // we got a -ENOENT and can just fall through...
+  }
+
   encode(op.entry, bl);
-  int ret = cls_cxx_map_set_val(hctx, key, &bl);
+  ret = cls_cxx_map_set_val(hctx, key, &bl);
   if (ret < 0) {
-    CLS_ERR("error adding reshard job for bucket %s with key %s",op.entry.bucket_name.c_str(), key.c_str());
+    CLS_ERR("error adding reshard job for bucket %s with key %s",
+	    op.entry.bucket_name.c_str(), key.c_str());
     return ret;
   }
 
diff --git a/src/cls/rgw/cls_rgw_client.cc b/src/cls/rgw/cls_rgw_client.cc
index 966823729b7..ac87c9a4a40 100644
--- a/src/cls/rgw/cls_rgw_client.cc
+++ b/src/cls/rgw/cls_rgw_client.cc
@@ -1083,11 +1083,14 @@ void cls_rgw_mp_upload_part_info_update(librados::ObjectWriteOperation& op,
   op.exec(RGW_CLASS, RGW_MP_UPLOAD_PART_INFO_UPDATE, in);
 }
 
-void cls_rgw_reshard_add(librados::ObjectWriteOperation& op, const cls_rgw_reshard_entry& entry)
+void cls_rgw_reshard_add(librados::ObjectWriteOperation& op,
+			 const cls_rgw_reshard_entry& entry,
+			 const bool create_only)
 {
   bufferlist in;
   cls_rgw_reshard_add_op call;
   call.entry = entry;
+  call.create_only = create_only;
   encode(call, in);
   op.exec(RGW_CLASS, RGW_RESHARD_ADD, in);
 }
diff --git a/src/cls/rgw/cls_rgw_client.h b/src/cls/rgw/cls_rgw_client.h
index 6f9084acdd3..ac062b987ae 100644
--- a/src/cls/rgw/cls_rgw_client.h
+++ b/src/cls/rgw/cls_rgw_client.h
@@ -626,7 +626,9 @@ int cls_rgw_lc_list(librados::IoCtx& io_ctx, const std::string& oid,
 void cls_rgw_mp_upload_part_info_update(librados::ObjectWriteOperation& op, const std::string& part_key, const RGWUploadPartInfo& info);
 
 /* resharding */
-void cls_rgw_reshard_add(librados::ObjectWriteOperation& op, const cls_rgw_reshard_entry& entry);
+void cls_rgw_reshard_add(librados::ObjectWriteOperation& op,
+			 const cls_rgw_reshard_entry& entry,
+			 const bool create_only);
 void cls_rgw_reshard_remove(librados::ObjectWriteOperation& op, const cls_rgw_reshard_entry& entry);
 // these overloads which call io_ctx.operate() should not be called in the rgw.
 // rgw_rados_operate() should be called after the overloads w/o calls to io_ctx.operate()
diff --git a/src/cls/rgw/cls_rgw_ops.h b/src/cls/rgw/cls_rgw_ops.h
index a4d76de108b..b824c73d3d0 100644
--- a/src/cls/rgw/cls_rgw_ops.h
+++ b/src/cls/rgw/cls_rgw_ops.h
@@ -1480,19 +1480,27 @@ struct cls_rgw_mp_upload_part_info_update_op {
 WRITE_CLASS_ENCODER(cls_rgw_mp_upload_part_info_update_op)
 
 struct cls_rgw_reshard_add_op {
- cls_rgw_reshard_entry entry;
+  cls_rgw_reshard_entry entry;
+
+  // true -> will not overwrite existing entry
+  bool create_only {false};
 
   cls_rgw_reshard_add_op() {}
 
   void encode(ceph::buffer::list& bl) const {
-    ENCODE_START(1, 1, bl);
+    ENCODE_START(2, 1, bl);
     encode(entry, bl);
+    encode(create_only, bl);
     ENCODE_FINISH(bl);
   }
 
   void decode(ceph::buffer::list::const_iterator& bl) {
-    DECODE_START(1, bl);
+    DECODE_START(2, bl);
     decode(entry, bl);
+    create_only = false;
+    if (struct_v >= 2) {
+      decode(create_only, bl);
+    }
     DECODE_FINISH(bl);
   }
   static void generate_test_instances(std::list<cls_rgw_reshard_add_op*>& o);