Create new refcount database atomically during account check.

Use a temporary refcount db for check instead of an in-memory vector. This
avoid the memory usage problems created by using the vector on large accounts,
but may require us to improve the efficiency of the refcount database itself
to avoid large numbers of small I/O operations. That is very doable now that
we're using a class for it.

Fix some inconsistencies and mistakes in handling reference counts and
info counters during account checks (more to come).

1 files changed, 126 insertions, 30 deletions

diff --git a/lib/backupstore/BackupStoreRefCountDatabase.cpp b/lib/backupstore/BackupStoreRefCountDatabase.cpp
index 26f9acca..86f75a55 100644
--- a/lib/backupstore/BackupStoreRefCountDatabase.cpp
+++ b/lib/backupstore/BackupStoreRefCountDatabase.cpp
@@ -9,6 +9,8 @@
 
 #include "Box.h"
 
+#include <stdio.h>
+
 #include <algorithm>
 
 #include "BackupStoreRefCountDatabase.h"
@@ -34,12 +36,82 @@
 //
 // --------------------------------------------------------------------------
 BackupStoreRefCountDatabase::BackupStoreRefCountDatabase(const
-	BackupStoreAccountDatabase::Entry& rAccount)
+	BackupStoreAccountDatabase::Entry& rAccount, bool ReadOnly,
+	bool Temporary, std::auto_ptr<FileStream> apDatabaseFile)
 : mAccount(rAccount),
-  mFilename(GetFilename(rAccount)),
-  mReadOnly(true),
-  mIsModified(false)
+  mFilename(GetFilename(rAccount, Temporary)),
+  mReadOnly(ReadOnly),
+  mIsModified(false),
+  mIsTemporaryFile(Temporary),
+  mapDatabaseFile(apDatabaseFile)
 {
+	ASSERT(!(ReadOnly && Temporary)); // being both doesn't make sense
+}
+
+void BackupStoreRefCountDatabase::Commit()
+{
+	if (!mIsTemporaryFile)
+	{
+		THROW_EXCEPTION_MESSAGE(CommonException, Internal,
+			"Cannot commit a permanent reference count database");
+	}
+
+	if (!mapDatabaseFile.get())
+	{
+		THROW_EXCEPTION_MESSAGE(CommonException, Internal,
+			"Reference count database is already closed");
+	}
+
+	mapDatabaseFile->Close();
+	mapDatabaseFile.reset();
+
+	std::string Final_Filename = GetFilename(mAccount, false);
+
+	#ifdef WIN32
+	if(FileExists(Final_Filename) && unlink(Final_Filename.c_str()) != 0)
+	{
+		THROW_SYS_FILE_ERROR("Failed to delete old permanent refcount "
+			"database file", mFilename, CommonException, OSFileError);
+	}
+	#endif
+
+	if(rename(mFilename.c_str(), Final_Filename.c_str()) != 0)
+	{
+		THROW_SYS_ERROR("Failed to rename temporary refcount database "
+			"file from " << mFilename << " to " <<
+			Final_Filename, CommonException, OSFileError);
+	}
+
+	mFilename = Final_Filename;
+	mIsModified = false;
+	mIsTemporaryFile = false;
+}
+
+void BackupStoreRefCountDatabase::Discard()
+{
+	if (!mIsTemporaryFile)
+	{
+		THROW_EXCEPTION_MESSAGE(CommonException, Internal,
+			"Cannot discard a permanent reference count database");
+	}
+
+	if (!mapDatabaseFile.get())
+	{
+		THROW_EXCEPTION_MESSAGE(CommonException, Internal,
+			"Reference count database is already closed");
+	}
+
+	mapDatabaseFile->Close();
+	mapDatabaseFile.reset();
+
+	if(unlink(mFilename.c_str()) != 0)
+	{
+		THROW_SYS_FILE_ERROR("Failed to delete temporary refcount database "
+			"file ", mFilename, CommonException, OSFileError);
+	}
+
+	mIsModified = false;
+	mIsTemporaryFile = false;
 }
 
 // --------------------------------------------------------------------------
@@ -52,16 +124,27 @@ BackupStoreRefCountDatabase::BackupStoreRefCountDatabase(const
 // --------------------------------------------------------------------------
 BackupStoreRefCountDatabase::~BackupStoreRefCountDatabase()
 {
+	if (mIsTemporaryFile)
+	{
+		THROW_EXCEPTION_MESSAGE(CommonException, Internal,
+			"BackupStoreRefCountDatabase destroyed without "
+			"explicit commit or discard");
+		Discard();
+	}
 }
 
 std::string BackupStoreRefCountDatabase::GetFilename(const
-	BackupStoreAccountDatabase::Entry& rAccount)
+	BackupStoreAccountDatabase::Entry& rAccount, bool Temporary)
 {
 	std::string RootDir = BackupStoreAccounts::GetAccountRoot(rAccount);
 	ASSERT(RootDir[RootDir.size() - 1] == '/' ||
 		RootDir[RootDir.size() - 1] == DIRECTORY_SEPARATOR_ASCHAR);
 
-	std::string fn(RootDir + REFCOUNT_FILENAME ".db");
+	std::string fn(RootDir + REFCOUNT_FILENAME ".rdb");
+	if(Temporary)
+	{
+		fn += "X";
+	}
 	RaidFileController &rcontroller(RaidFileController::GetController());
 	RaidFileDiscSet rdiscSet(rcontroller.GetDiscSet(rAccount.GetDiscSet()));
 	return RaidFileUtil::MakeWriteFileName(rdiscSet, fn);
@@ -77,35 +160,48 @@ std::string BackupStoreRefCountDatabase::GetFilename(const
 //		Created: 2003/08/28
 //
 // --------------------------------------------------------------------------
-void BackupStoreRefCountDatabase::Create(const
-	BackupStoreAccountDatabase::Entry& rAccount, bool AllowOverwrite)
+std::auto_ptr<BackupStoreRefCountDatabase>
+	BackupStoreRefCountDatabase::Create
+	(const BackupStoreAccountDatabase::Entry& rAccount)
 {
 	// Initial header
 	refcount_StreamFormat hdr;
 	hdr.mMagicValue = htonl(REFCOUNT_MAGIC_VALUE);
 	hdr.mAccountID = htonl(rAccount.GetID());
 	
-	// Generate the filename
-	std::string Filename = GetFilename(rAccount);
+	std::string Filename = GetFilename(rAccount, true); // temporary
 
 	// Open the file for writing
-	if (FileExists(Filename) && !AllowOverwrite)
-	{
-		THROW_FILE_ERROR("Failed to overwrite refcount database: "
-			"not allowed here", Filename, RaidFileException,
-			CannotOverwriteExistingFile);
-	}
-
-	int flags = O_CREAT | O_BINARY | O_RDWR;
-	if (!AllowOverwrite)
+	if (FileExists(Filename))
 	{
-		flags |= O_EXCL;
+		BOX_WARNING(BOX_FILE_MESSAGE(Filename, "Overwriting existing "
+			"temporary reference count database"));
+		if (unlink(Filename.c_str()) != 0)
+		{
+			THROW_SYS_FILE_ERROR("Failed to delete old temporary "
+				"reference count database file", Filename,
+				CommonException, OSFileError);
+		}
 	}
 
+	int flags = O_CREAT | O_BINARY | O_RDWR | O_EXCL;
 	std::auto_ptr<FileStream> DatabaseFile(new FileStream(Filename, flags));
 	
 	// Write header
 	DatabaseFile->Write(&hdr, sizeof(hdr));
+
+	// Make new object
+	std::auto_ptr<BackupStoreRefCountDatabase> refcount(
+		new BackupStoreRefCountDatabase(rAccount, false, true,
+			DatabaseFile));
+	
+	// The root directory must always have one reference for a database
+	// to be valid, so set that now on the new database. This will leave
+	// mIsModified set to true.
+	refcount->SetRefCount(BACKUPSTORE_ROOT_DIRECTORY_ID, 1);
+
+	// return it to caller
+	return refcount;
 }
 
 // --------------------------------------------------------------------------
@@ -122,12 +218,13 @@ void BackupStoreRefCountDatabase::Create(const
 std::auto_ptr<BackupStoreRefCountDatabase> BackupStoreRefCountDatabase::Load(
 	const BackupStoreAccountDatabase::Entry& rAccount, bool ReadOnly)
 {
-	// Generate the filename
-	std::string filename = GetFilename(rAccount);
+	// Generate the filename. Cannot open a temporary database, so it must
+	// be a permanent one.
+	std::string Filename = GetFilename(rAccount, false);
 	int flags = ReadOnly ? O_RDONLY : O_RDWR;
 
 	// Open the file for read/write
-	std::auto_ptr<FileStream> dbfile(new FileStream(filename,
+	std::auto_ptr<FileStream> dbfile(new FileStream(Filename,
 		flags | O_BINARY));
 	
 	// Read in a header
@@ -135,7 +232,7 @@ std::auto_ptr<BackupStoreRefCountDatabase> BackupStoreRefCountDatabase::Load(
 	if(!dbfile->ReadFullBuffer(&hdr, sizeof(hdr), 0 /* not interested in bytes read if this fails */))
 	{
 		THROW_FILE_ERROR("Failed to read refcount database: "
-			"short read", filename, BackupStoreException,
+			"short read", Filename, BackupStoreException,
 			CouldNotLoadStoreInfo);
 	}
 	
@@ -144,16 +241,14 @@ std::auto_ptr<BackupStoreRefCountDatabase> BackupStoreRefCountDatabase::Load(
 		(int32_t)ntohl(hdr.mAccountID) != rAccount.GetID())
 	{
 		THROW_FILE_ERROR("Failed to read refcount database: "
-			"bad magic number", filename, BackupStoreException,
+			"bad magic number", Filename, BackupStoreException,
 			BadStoreInfoOnLoad);
 	}
 	
 	// Make new object
-	std::auto_ptr<BackupStoreRefCountDatabase> refcount(new BackupStoreRefCountDatabase(rAccount));
-	
-	// Put in basic location info
-	refcount->mReadOnly = ReadOnly;
-	refcount->mapDatabaseFile = dbfile;
+	std::auto_ptr<BackupStoreRefCountDatabase> refcount(
+		new BackupStoreRefCountDatabase(rAccount, ReadOnly, false,
+			dbfile));
 	
 	// return it to caller
 	return refcount;
@@ -229,6 +324,7 @@ void BackupStoreRefCountDatabase::SetRefCount(int64_t ObjectID,
 	mapDatabaseFile->Seek(offset, SEEK_SET);
 	refcount_t RefCountNetOrder = htonl(NewRefCount);
 	mapDatabaseFile->Write(&RefCountNetOrder, sizeof(RefCountNetOrder));
+	mIsModified = true;
 }
 
 bool BackupStoreRefCountDatabase::RemoveReference(int64_t ObjectID)