librbd: migrate from boost::variant to std::variant

tchaikov · tchaikov · commit 184443c22fd2 · 2025-03-25T21:04:09.000+08:00
migrate from boost::variant to std::variant Complete migration started in commit 017f333, replacing boost::variant with std::variant throughout the librbd codebase. This change is part of our ongoing effort to reduce third-party dependencies by leveraging C++ standard library alternatives where possible. Benefits include: - Improved code readability and maintainability - Reduced external dependency surface - More consistent API usage with other components Signed-off-by: Kefu Chai <tchaikov@gmail.com>
diff --git a/src/librbd/Journal.cc b/src/librbd/Journal.cc
@@ -205,7 +205,7 @@ struct GetTagsRequest {
     }
 
     journal::ImageClientMeta *image_client_meta =
-      boost::get<journal::ImageClientMeta>(&client_data.client_meta);
+      std::get_if<journal::ImageClientMeta>(&client_data.client_meta);
     if (image_client_meta == nullptr) {
       lderr(cct) << this << " OpenJournalerRequest::" << __func__ << ": "
                  << "failed to get client meta" << dendl;
@@ -1768,7 +1768,7 @@ int Journal<I>::check_resync_requested(bool *do_resync) {
   }
 
   journal::ImageClientMeta *image_client_meta =
-    boost::get<journal::ImageClientMeta>(&client_data.client_meta);
+    std::get_if<journal::ImageClientMeta>(&client_data.client_meta);
   if (image_client_meta == nullptr) {
     lderr(cct) << this << " " << __func__ << ": "
                << "failed to access image client meta struct" << dendl;
diff --git a/src/librbd/journal/OpenRequest.cc b/src/librbd/journal/OpenRequest.cc
@@ -83,7 +83,7 @@ void OpenRequest<I>::handle_init(int r) {
   }
 
   journal::ImageClientMeta *image_client_meta =
-    boost::get<journal::ImageClientMeta>(&client_data.client_meta);
+    std::get_if<journal::ImageClientMeta>(&client_data.client_meta);
   if (image_client_meta == nullptr) {
     lderr(cct) << this << " " << __func__ << ": "
                << "failed to extract client meta data" << dendl;
diff --git a/src/librbd/journal/Replay.cc b/src/librbd/journal/Replay.cc
@@ -220,8 +220,8 @@ void Replay<I>::process(const EventEntry &event_entry,
     return;
   }
 
-  boost::apply_visitor(EventVisitor(this, on_ready, on_safe),
-                       event_entry.event);
+  std::visit(EventVisitor(this, on_ready, on_safe),
+             event_entry.event);
 }
 
 template <typename I>
diff --git a/src/librbd/journal/Types.cc b/src/librbd/journal/Types.cc
@@ -16,15 +16,15 @@ using ceph::decode;
 namespace {
 
 template <typename E>
-class GetTypeVisitor : public boost::static_visitor<E> {
+class GetTypeVisitor {
 public:
   template <typename T>
   inline E operator()(const T&) const {
     return T::TYPE;
   }
 };
 
-class EncodeVisitor : public boost::static_visitor<void> {
+class EncodeVisitor {
 public:
   explicit EncodeVisitor(bufferlist &bl) : m_bl(bl) {
   }
@@ -38,7 +38,7 @@ class EncodeVisitor : public boost::static_visitor<void> {
   bufferlist &m_bl;
 };
 
-class DecodeVisitor : public boost::static_visitor<void> {
+class DecodeVisitor {
 public:
   DecodeVisitor(__u8 version, bufferlist::const_iterator &iter)
     : m_version(version), m_iter(iter) {
@@ -53,7 +53,7 @@ class DecodeVisitor : public boost::static_visitor<void> {
   bufferlist::const_iterator &m_iter;
 };
 
-class DumpVisitor : public boost::static_visitor<void> {
+class DumpVisitor {
 public:
   explicit DumpVisitor(Formatter *formatter, const std::string &key)
     : m_formatter(formatter), m_key(key) {}
@@ -411,12 +411,12 @@ void UnknownEvent::dump(Formatter *f) const {
 }
 
 EventType EventEntry::get_event_type() const {
-  return boost::apply_visitor(GetTypeVisitor<EventType>(), event);
+  return std::visit(GetTypeVisitor<EventType>(), event);
 }
 
 void EventEntry::encode(bufferlist& bl) const {
   ENCODE_START(5, 1, bl);
-  boost::apply_visitor(EncodeVisitor(bl), event);
+  std::visit(EncodeVisitor(bl), event);
   ENCODE_FINISH(bl);
   encode_metadata(bl);
 }
@@ -494,15 +494,15 @@ void EventEntry::decode(bufferlist::const_iterator& it) {
     break;
   }
 
-  boost::apply_visitor(DecodeVisitor(struct_v, it), event);
+  std::visit(DecodeVisitor(struct_v, it), event);
   DECODE_FINISH(it);
   if (struct_v >= 4) {
     decode_metadata(it);
   }
 }
 
 void EventEntry::dump(Formatter *f) const {
-  boost::apply_visitor(DumpVisitor(f, "event_type"), event);
+  std::visit(DumpVisitor(f, "event_type"), event);
   f->dump_stream("timestamp") << timestamp;
 }
 
@@ -689,12 +689,12 @@ void UnknownClientMeta::dump(Formatter *f) const {
 }
 
 ClientMetaType ClientData::get_client_meta_type() const {
-  return boost::apply_visitor(GetTypeVisitor<ClientMetaType>(), client_meta);
+  return std::visit(GetTypeVisitor<ClientMetaType>(), client_meta);
 }
 
 void ClientData::encode(bufferlist& bl) const {
   ENCODE_START(2, 1, bl);
-  boost::apply_visitor(EncodeVisitor(bl), client_meta);
+  std::visit(EncodeVisitor(bl), client_meta);
   ENCODE_FINISH(bl);
 }
 
@@ -720,12 +720,12 @@ void ClientData::decode(bufferlist::const_iterator& it) {
     break;
   }
 
-  boost::apply_visitor(DecodeVisitor(struct_v, it), client_meta);
+  std::visit(DecodeVisitor(struct_v, it), client_meta);
   DECODE_FINISH(it);
 }
 
 void ClientData::dump(Formatter *f) const {
-  boost::apply_visitor(DumpVisitor(f, "client_meta_type"), client_meta);
+  std::visit(DumpVisitor(f, "client_meta_type"), client_meta);
 }
 
 void ClientData::generate_test_instances(std::list<ClientData *> &o) {
diff --git a/src/librbd/journal/Types.h b/src/librbd/journal/Types.h
@@ -13,9 +13,9 @@
 #include "librbd/Types.h"
 #include <iosfwd>
 #include <list>
+#include <variant>
 #include <boost/none.hpp>
 #include <boost/optional.hpp>
-#include <boost/variant.hpp>
 #include <boost/mpl/vector.hpp>
 
 namespace ceph {
@@ -410,7 +410,7 @@ struct UnknownEvent {
   void dump(Formatter *f) const;
 };
 
-typedef boost::mpl::vector<AioDiscardEvent,
+using Event = std::variant<AioDiscardEvent,
                            AioWriteEvent,
                            AioFlushEvent,
                            OpFinishEvent,
@@ -430,8 +430,7 @@ typedef boost::mpl::vector<AioDiscardEvent,
                            MetadataRemoveEvent,
                            AioWriteSameEvent,
                            AioCompareAndWriteEvent,
-                           UnknownEvent> EventVector;
-typedef boost::make_variant_over<EventVector>::type Event;
+                           UnknownEvent>;
 
 struct EventEntry {
   static uint32_t get_fixed_size() {
@@ -575,10 +574,10 @@ struct UnknownClientMeta {
   void dump(Formatter *f) const;
 };
 
-typedef boost::variant<ImageClientMeta,
-                       MirrorPeerClientMeta,
-                       CliClientMeta,
-                       UnknownClientMeta> ClientMeta;
+using ClientMeta = std::variant<ImageClientMeta,
+                                MirrorPeerClientMeta,
+                                CliClientMeta,
+                                UnknownClientMeta>;
 
 struct ClientData {
   ClientData() {
diff --git a/src/librbd/mirror/DisableRequest.cc b/src/librbd/mirror/DisableRequest.cc
@@ -258,7 +258,7 @@ Context *DisableRequest<I>::handle_get_clients(int *result) {
     m_ret[client.id] = 0;
 
     journal::MirrorPeerClientMeta client_meta =
-      boost::get<journal::MirrorPeerClientMeta>(client_data.client_meta);
+      std::get<journal::MirrorPeerClientMeta>(client_data.client_meta);
 
     for (const auto& sync : client_meta.sync_points) {
       send_remove_snap(client.id, sync.snap_namespace, sync.snap_name);
diff --git a/src/test/librbd/journal/test_Entries.cc b/src/test/librbd/journal/test_Entries.cc
@@ -13,7 +13,6 @@
 #include "journal/ReplayHandler.h"
 #include "journal/Settings.h"
 #include <list>
-#include <boost/variant.hpp>
 
 void register_test_journal_entries() {
 }
@@ -147,7 +146,7 @@ TEST_F(TestJournalEntries, AioWrite) {
             event_entry.get_event_type());
 
   librbd::journal::AioWriteEvent aio_write_event =
-    boost::get<librbd::journal::AioWriteEvent>(event_entry.event);
+    std::get<librbd::journal::AioWriteEvent>(event_entry.event);
   ASSERT_EQ(123U, aio_write_event.offset);
   ASSERT_EQ(buffer.size(), aio_write_event.length);
 
@@ -191,7 +190,7 @@ TEST_F(TestJournalEntries, AioDiscard) {
             event_entry.get_event_type());
 
   librbd::journal::AioDiscardEvent aio_discard_event =
-    boost::get<librbd::journal::AioDiscardEvent>(event_entry.event);
+    std::get<librbd::journal::AioDiscardEvent>(event_entry.event);
   ASSERT_EQ(123U, aio_discard_event.offset);
   ASSERT_EQ(234U, aio_discard_event.length);
 }
@@ -251,7 +250,7 @@ TEST_F(TestJournalEntries, AioDiscardWithPrune) {
               event_entry.get_event_type());
 
     librbd::journal::AioDiscardEvent aio_discard_event =
-      boost::get<librbd::journal::AioDiscardEvent>(event_entry.event);
+      std::get<librbd::journal::AioDiscardEvent>(event_entry.event);
     ASSERT_EQ(offset, aio_discard_event.offset);
     ASSERT_EQ(size, aio_discard_event.length);
 
diff --git a/src/test/rbd_mirror/image_replayer/journal/test_mock_EventPreprocessor.cc b/src/test/rbd_mirror/image_replayer/journal/test_mock_EventPreprocessor.cc
@@ -163,7 +163,7 @@ TEST_F(TestMockImageReplayerJournalEventPreprocessor, PreprocessSnapRename) {
   ASSERT_EQ(expected_snap_seqs, m_client_meta.snap_seqs);
 
   librbd::journal::SnapRenameEvent *event =
-    boost::get<librbd::journal::SnapRenameEvent>(&event_entry.event);
+    std::get_if<librbd::journal::SnapRenameEvent>(&event_entry.event);
   ASSERT_EQ(6U, event->snap_id);
 }
 
@@ -186,7 +186,7 @@ TEST_F(TestMockImageReplayerJournalEventPreprocessor, PreprocessSnapRenameMissin
   ASSERT_EQ(-ENOENT, ctx.wait());
 
   librbd::journal::SnapRenameEvent *event =
-    boost::get<librbd::journal::SnapRenameEvent>(&event_entry.event);
+    std::get_if<librbd::journal::SnapRenameEvent>(&event_entry.event);
   ASSERT_EQ(CEPH_NOSNAP, event->snap_id);
 }
 
@@ -215,7 +215,7 @@ TEST_F(TestMockImageReplayerJournalEventPreprocessor, PreprocessSnapRenameKnown)
   ASSERT_EQ(expected_snap_seqs, m_client_meta.snap_seqs);
 
   librbd::journal::SnapRenameEvent *event =
-    boost::get<librbd::journal::SnapRenameEvent>(&event_entry.event);
+    std::get_if<librbd::journal::SnapRenameEvent>(&event_entry.event);
   ASSERT_EQ(6U, event->snap_id);
 }
 
diff --git a/src/tools/rbd_mirror/image_replayer/Utils.cc b/src/tools/rbd_mirror/image_replayer/Utils.cc
@@ -42,7 +42,7 @@ bool decode_client_meta(const cls::journal::Client& client,
     return false;
   }
 
-  auto local_client_meta = boost::get<librbd::journal::MirrorPeerClientMeta>(
+  auto local_client_meta = std::get_if<librbd::journal::MirrorPeerClientMeta>(
     &client_data.client_meta);
   if (local_client_meta == nullptr) {
     derr << "unknown peer registration" << dendl;
diff --git a/src/tools/rbd_mirror/image_replayer/journal/EventPreprocessor.cc b/src/tools/rbd_mirror/image_replayer/journal/EventPreprocessor.cc
@@ -11,7 +11,6 @@
 #include "librbd/Utils.h"
 #include "librbd/asio/ContextWQ.h"
 #include "librbd/journal/Types.h"
-#include <boost/variant.hpp>
 
 #include <shared_mutex> // for std::shared_lock
 
@@ -95,8 +94,8 @@ void EventPreprocessor<I>::preprocess_event() {
   m_snap_seqs = m_client_meta->snap_seqs;
   m_snap_seqs_updated = prune_snap_map(&m_snap_seqs);
 
-  int r = boost::apply_visitor(PreprocessEventVisitor(this),
-                               m_event_entry->event);
+  int r = std::visit(PreprocessEventVisitor(this),
+                     m_event_entry->event);
   if (r < 0) {
     finish(r);
     return;
diff --git a/src/tools/rbd_mirror/image_replayer/journal/PrepareReplayRequest.cc b/src/tools/rbd_mirror/image_replayer/journal/PrepareReplayRequest.cc
@@ -162,7 +162,7 @@ void PrepareReplayRequest<I>::handle_get_remote_tag_class(int r) {
   }
 
   librbd::journal::ImageClientMeta *client_meta =
-    boost::get<librbd::journal::ImageClientMeta>(&client_data.client_meta);
+    std::get_if<librbd::journal::ImageClientMeta>(&client_data.client_meta);
   if (client_meta == nullptr) {
     derr << "unknown remote client registration" << dendl;
     finish(-EINVAL);

Original file line number	Diff line number	Diff line change
`@@ -83,7 +83,7 @@ void OpenRequest<I>::handle_init(int r) {`
`83`	`83`	`}`
`84`	`84`
`85`	`85`	`journal::ImageClientMeta *image_client_meta =`
`86`		`- boost::get<journal::ImageClientMeta>(&client_data.client_meta);`
	`86`	`+ std::get_if<journal::ImageClientMeta>(&client_data.client_meta);`
`87`	`87`	`if (image_client_meta == nullptr) {`
`88`	`88`	`lderr(cct) << this << " " << __func__ << ": "`
`89`	`89`	`<< "failed to extract client meta data" << dendl;`
Original file line number	Diff line number	Diff line change
`@@ -220,8 +220,8 @@ void Replay<I>::process(const EventEntry &event_entry,`
`220`	`220`	`return;`
`221`	`221`	`}`
`222`	`222`
`223`		`- boost::apply_visitor(EventVisitor(this, on_ready, on_safe),`
`224`		`- event_entry.event);`
	`223`	`+ std::visit(EventVisitor(this, on_ready, on_safe),`
	`224`	`+ event_entry.event);`
`225`	`225`	`}`
`226`	`226`
`227`	`227`	`template <typename I>`
Original file line number	Diff line number	Diff line change
`@@ -16,15 +16,15 @@ using ceph::decode;`
`16`	`16`	`namespace {`
`17`	`17`
`18`	`18`	`template <typename E>`
`19`		`-class GetTypeVisitor : public boost::static_visitor<E> {`
	`19`	`+class GetTypeVisitor {`
`20`	`20`	`public:`
`21`	`21`	`template <typename T>`
`22`	`22`	`inline E operator()(const T&) const {`
`23`	`23`	`return T::TYPE;`
`24`	`24`	`}`
`25`	`25`	`};`
`26`	`26`
`27`		`-class EncodeVisitor : public boost::static_visitor<void> {`
	`27`	`+class EncodeVisitor {`
`28`	`28`	`public:`
`29`	`29`	`explicit EncodeVisitor(bufferlist &bl) : m_bl(bl) {`
`30`	`30`	`}`
`@@ -38,7 +38,7 @@ class EncodeVisitor : public boost::static_visitor<void> {`
`38`	`38`	`bufferlist &m_bl;`
`39`	`39`	`};`
`40`	`40`
`41`		`-class DecodeVisitor : public boost::static_visitor<void> {`
	`41`	`+class DecodeVisitor {`
`42`	`42`	`public:`
`43`	`43`	`DecodeVisitor(__u8 version, bufferlist::const_iterator &iter)`
`44`	`44`	`: m_version(version), m_iter(iter) {`
`@@ -53,7 +53,7 @@ class DecodeVisitor : public boost::static_visitor<void> {`
`53`	`53`	`bufferlist::const_iterator &m_iter;`
`54`	`54`	`};`
`55`	`55`
`56`		`-class DumpVisitor : public boost::static_visitor<void> {`
	`56`	`+class DumpVisitor {`
`57`	`57`	`public:`
`58`	`58`	`explicit DumpVisitor(Formatter *formatter, const std::string &key)`
`59`	`59`	`: m_formatter(formatter), m_key(key) {}`
`@@ -411,12 +411,12 @@ void UnknownEvent::dump(Formatter *f) const {`
`411`	`411`	`}`
`412`	`412`
`413`	`413`	`EventType EventEntry::get_event_type() const {`
`414`		`- return boost::apply_visitor(GetTypeVisitor<EventType>(), event);`
	`414`	`+ return std::visit(GetTypeVisitor<EventType>(), event);`
`415`	`415`	`}`
`416`	`416`
`417`	`417`	`void EventEntry::encode(bufferlist& bl) const {`
`418`	`418`	`ENCODE_START(5, 1, bl);`
`419`		`- boost::apply_visitor(EncodeVisitor(bl), event);`
	`419`	`+ std::visit(EncodeVisitor(bl), event);`
`420`	`420`	`ENCODE_FINISH(bl);`
`421`	`421`	`encode_metadata(bl);`
`422`	`422`	`}`
`@@ -494,15 +494,15 @@ void EventEntry::decode(bufferlist::const_iterator& it) {`
`494`	`494`	`break;`
`495`	`495`	`}`
`496`	`496`
`497`		`- boost::apply_visitor(DecodeVisitor(struct_v, it), event);`
	`497`	`+ std::visit(DecodeVisitor(struct_v, it), event);`
`498`	`498`	`DECODE_FINISH(it);`
`499`	`499`	`if (struct_v >= 4) {`
`500`	`500`	`decode_metadata(it);`
`501`	`501`	`}`
`502`	`502`	`}`
`503`	`503`
`504`	`504`	`void EventEntry::dump(Formatter *f) const {`
`505`		`- boost::apply_visitor(DumpVisitor(f, "event_type"), event);`
	`505`	`+ std::visit(DumpVisitor(f, "event_type"), event);`
`506`	`506`	`f->dump_stream("timestamp") << timestamp;`
`507`	`507`	`}`
`508`	`508`
`@@ -689,12 +689,12 @@ void UnknownClientMeta::dump(Formatter *f) const {`
`689`	`689`	`}`
`690`	`690`
`691`	`691`	`ClientMetaType ClientData::get_client_meta_type() const {`
`692`		`- return boost::apply_visitor(GetTypeVisitor<ClientMetaType>(), client_meta);`
	`692`	`+ return std::visit(GetTypeVisitor<ClientMetaType>(), client_meta);`
`693`	`693`	`}`
`694`	`694`
`695`	`695`	`void ClientData::encode(bufferlist& bl) const {`
`696`	`696`	`ENCODE_START(2, 1, bl);`
`697`		`- boost::apply_visitor(EncodeVisitor(bl), client_meta);`
	`697`	`+ std::visit(EncodeVisitor(bl), client_meta);`
`698`	`698`	`ENCODE_FINISH(bl);`
`699`	`699`	`}`
`700`	`700`
`@@ -720,12 +720,12 @@ void ClientData::decode(bufferlist::const_iterator& it) {`
`720`	`720`	`break;`
`721`	`721`	`}`
`722`	`722`
`723`		`- boost::apply_visitor(DecodeVisitor(struct_v, it), client_meta);`
	`723`	`+ std::visit(DecodeVisitor(struct_v, it), client_meta);`
`724`	`724`	`DECODE_FINISH(it);`
`725`	`725`	`}`
`726`	`726`
`727`	`727`	`void ClientData::dump(Formatter *f) const {`
`728`		`- boost::apply_visitor(DumpVisitor(f, "client_meta_type"), client_meta);`
	`728`	`+ std::visit(DumpVisitor(f, "client_meta_type"), client_meta);`
`729`	`729`	`}`
`730`	`730`
`731`	`731`	`void ClientData::generate_test_instances(std::list<ClientData *> &o) {`
Original file line number	Diff line number	Diff line change
`@@ -163,7 +163,7 @@ TEST_F(TestMockImageReplayerJournalEventPreprocessor, PreprocessSnapRename) {`
`163`	`163`	`ASSERT_EQ(expected_snap_seqs, m_client_meta.snap_seqs);`
`164`	`164`
`165`	`165`	`librbd::journal::SnapRenameEvent *event =`
`166`		`- boost::get<librbd::journal::SnapRenameEvent>(&event_entry.event);`
	`166`	`+ std::get_if<librbd::journal::SnapRenameEvent>(&event_entry.event);`
`167`	`167`	`ASSERT_EQ(6U, event->snap_id);`
`168`	`168`	`}`
`169`	`169`
`@@ -186,7 +186,7 @@ TEST_F(TestMockImageReplayerJournalEventPreprocessor, PreprocessSnapRenameMissin`
`186`	`186`	`ASSERT_EQ(-ENOENT, ctx.wait());`
`187`	`187`
`188`	`188`	`librbd::journal::SnapRenameEvent *event =`
`189`		`- boost::get<librbd::journal::SnapRenameEvent>(&event_entry.event);`
	`189`	`+ std::get_if<librbd::journal::SnapRenameEvent>(&event_entry.event);`
`190`	`190`	`ASSERT_EQ(CEPH_NOSNAP, event->snap_id);`
`191`	`191`	`}`
`192`	`192`
`@@ -215,7 +215,7 @@ TEST_F(TestMockImageReplayerJournalEventPreprocessor, PreprocessSnapRenameKnown)`
`215`	`215`	`ASSERT_EQ(expected_snap_seqs, m_client_meta.snap_seqs);`
`216`	`216`
`217`	`217`	`librbd::journal::SnapRenameEvent *event =`
`218`		`- boost::get<librbd::journal::SnapRenameEvent>(&event_entry.event);`
	`218`	`+ std::get_if<librbd::journal::SnapRenameEvent>(&event_entry.event);`
`219`	`219`	`ASSERT_EQ(6U, event->snap_id);`
`220`	`220`	`}`
`221`	`221`
Original file line number	Diff line number	Diff line change
`@@ -42,7 +42,7 @@ bool decode_client_meta(const cls::journal::Client& client,`
`42`	`42`	`return false;`
`43`	`43`	`}`
`44`	`44`
`45`		`- auto local_client_meta = boost::get<librbd::journal::MirrorPeerClientMeta>(`
	`45`	`+ auto local_client_meta = std::get_if<librbd::journal::MirrorPeerClientMeta>(`
`46`	`46`	`&client_data.client_meta);`
`47`	`47`	`if (local_client_meta == nullptr) {`
`48`	`48`	`derr << "unknown peer registration" << dendl;`