fix a bug, c api, if enable inplace_update_support, and use create sn… (#9471)

Summary:
c api release snapshot will core dump when enable inplace_update_support and create snapshot

Pull Request resolved: https://github.com/facebook/rocksdb/pull/9471

Reviewed By: akankshamahajan15

Differential Revision: D34965103

Pulled By: riversand963

fbshipit-source-id: c3aeeb9ea7126c2eda1466102794fecf57b6ab77

db/c_test.c

@@ -7,12 +7,13 @@
 
 #ifndef ROCKSDB_LITE  // Lite does not support C API
 
-#include "rocksdb/c.h"
-
+#include <assert.h>
 #include <stddef.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/types.h>
+
+#include "rocksdb/c.h"
 #ifndef OS_WIN
 #include <unistd.h>
 #endif
@@ -89,10 +90,8 @@ static void CheckEqual(const char* expected, const char* v, size_t n) {
     // ok
     return;
   } else {
-    fprintf(stderr, "%s: expected '%s', got '%s'\n",
-            phase,
-            (expected ? expected : "(null)"),
-            (v ? v : "(null"));
+    fprintf(stderr, "%s: expected '%s', got '%s'\n", phase,
+            (expected ? expected : "(null)"), (v ? v : "(null)"));
     abort();
   }
 }
@@ -989,7 +988,36 @@ int main(int argc, char** argv) {
     CheckGet(db, roptions, "foo", NULL);
     rocksdb_release_snapshot(db, snap);
   }
-
+  StartPhase("snapshot_with_memtable_inplace_update");
+  {
+    rocksdb_close(db);
+    const rocksdb_snapshot_t* snap = NULL;
+    const char* s_key = "foo_snap";
+    const char* value1 = "hello_s1";
+    const char* value2 = "hello_s2";
+    rocksdb_options_set_allow_concurrent_memtable_write(options, 0);
+    rocksdb_options_set_inplace_update_support(options, 1);
+    rocksdb_options_set_error_if_exists(options, 0);
+    db = rocksdb_open(options, dbname, &err);
+    CheckNoError(err);
+    rocksdb_put(db, woptions, s_key, 8, value1, 8, &err);
+    snap = rocksdb_create_snapshot(db);
+    assert(snap != NULL);
+    rocksdb_put(db, woptions, s_key, 8, value2, 8, &err);
+    CheckNoError(err);
+    rocksdb_readoptions_set_snapshot(roptions, snap);
+    CheckGet(db, roptions, "foo", NULL);
+    // snapshot syntax is invalid, because of inplace update supported is set
+    CheckGet(db, roptions, s_key, value2);
+    // restore the data and options
+    rocksdb_delete(db, woptions, s_key, 8, &err);
+    CheckGet(db, roptions, s_key, NULL);
+    rocksdb_release_snapshot(db, snap);
+    rocksdb_readoptions_set_snapshot(roptions, NULL);
+    rocksdb_options_set_inplace_update_support(options, 0);
+    rocksdb_options_set_allow_concurrent_memtable_write(options, 1);
+    rocksdb_options_set_error_if_exists(options, 1);
+  }
   StartPhase("repair");
   {
     // If we do not compact here, then the lazy deletion of

db/db_impl/db_impl.cc

@@ -3205,6 +3205,12 @@ bool CfdListContains(const CfdList& list, ColumnFamilyData* cfd) {
 }  //  namespace
 
 void DBImpl::ReleaseSnapshot(const Snapshot* s) {
+  if (s == nullptr) {
+    // DBImpl::GetSnapshot() can return nullptr when snapshot
+    // not supported by specifying the condition:
+    // inplace_update_support enabled.
+    return;
+  }
   const SnapshotImpl* casted_s = reinterpret_cast<const SnapshotImpl*>(s);
   {
     InstrumentedMutexLock l(&mutex_);

db/db_inplace_update_test.cc

@@ -169,6 +169,36 @@ TEST_F(DBTestInPlaceUpdate, InPlaceUpdateCallbackNoAction) {
     ASSERT_EQ(Get(1, "key"), "NOT_FOUND");
   } while (ChangeCompactOptions());
 }
+
+TEST_F(DBTestInPlaceUpdate, InPlaceUpdateAndSnapshot) {
+  do {
+    Options options = CurrentOptions();
+    options.create_if_missing = true;
+    options.inplace_update_support = true;
+    options.env = env_;
+    options.write_buffer_size = 100000;
+    options.allow_concurrent_memtable_write = false;
+    Reopen(options);
+    CreateAndReopenWithCF({"pikachu"}, options);
+
+    // Update key with values of smaller size, and
+    // run GetSnapshot and ReleaseSnapshot
+    int numValues = 2;
+    for (int i = numValues; i > 0; i--) {
+      const Snapshot* s = db_->GetSnapshot();
+      ASSERT_EQ(nullptr, s);
+      std::string value = DummyString(i, 'a');
+      ASSERT_OK(Put(1, "key", value));
+      ASSERT_EQ(value, Get(1, "key"));
+      // release s (nullptr)
+      db_->ReleaseSnapshot(s);
+    }
+
+    // Only 1 instance for that key.
+    validateNumberOfEntries(1, 1);
+  } while (ChangeCompactOptions());
+}
+
 }  // namespace ROCKSDB_NAMESPACE
 
 int main(int argc, char** argv) {

include/rocksdb/db.h

@@ -793,7 +793,7 @@ class DB {
   // snapshot is no longer needed.
   //
   // nullptr will be returned if the DB fails to take a snapshot or does
-  // not support snapshot.
+  // not support snapshot (eg: inplace_update_support enabled).
   virtual const Snapshot* GetSnapshot() = 0;
 
   // Release a previously acquired snapshot.  The caller must not