Merge pull request #259 from davecgh/jrick_msync

Fix bolt on OpenBSD

bolt_linux.go

@@ -1,13 +1,12 @@
 package bolt
 
 import (
-	"os"
 	"syscall"
 )
 
 var odirect = syscall.O_DIRECT
 
 // fdatasync flushes written data to a file descriptor.
-func fdatasync(f *os.File) error {
+func fdatasync(db *DB) error {
-	return syscall.Fdatasync(int(f.Fd()))
+	return syscall.Fdatasync(int(db.file.Fd()))
 }

bolt_openbsd.go

@@ -0,0 +1,29 @@
+package bolt
+
+import (
+	"syscall"
+	"unsafe"
+)
+
+const (
+	msAsync      = 1 << iota // perform asynchronous writes
+	msSync                   // perform synchronous writes
+	msInvalidate             // invalidate cached data
+)
+
+var odirect int
+
+func msync(db *DB) error {
+	_, _, errno := syscall.Syscall(syscall.SYS_MSYNC, uintptr(unsafe.Pointer(db.data)), uintptr(db.datasz), msInvalidate)
+	if errno != 0 {
+		return errno
+	}
+	return nil
+}
+
+func fdatasync(db *DB) error {
+	if db.data != nil {
+		return msync(db)
+	}
+	return db.file.Sync()
+}

bolt_windows.go

@@ -11,8 +11,8 @@ import (
 var odirect int
 
 // fdatasync flushes written data to a file descriptor.
-func fdatasync(f *os.File) error {
+func fdatasync(db *DB) error {
-	return f.Sync()
+	return db.file.Sync()
 }
 
 // flock acquires an advisory lock on a file descriptor.

boltsync_unix.go

@@ -1,14 +1,10 @@
-// +build !windows,!plan9,!linux
+// +build !windows,!plan9,!linux,!openbsd
 
 package bolt
 
-import (
-	"os"
-)
-
 var odirect int
 
 // fdatasync flushes written data to a file descriptor.
-func fdatasync(f *os.File) error {
+func fdatasync(db *DB) error {
-	return f.Sync()
+	return db.file.Sync()
 }

db.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"hash/fnv"
 	"os"
+	"runtime"
 	"runtime/debug"
 	"strings"
 	"sync"
@@ -23,6 +24,12 @@ const version = 2
 // Represents a marker value to indicate that a file is a Bolt DB.
 const magic uint32 = 0xED0CDAED
 
+// IgnoreNoSync specifies whether the NoSync field of a DB is ignored when
+// syncing changes to a file.  This is required as some operating systems,
+// such as OpenBSD, do not have a unified buffer cache (UBC) and writes
+// must be synchronzied using the msync(2) syscall.
+const IgnoreNoSync = runtime.GOOS == "openbsd"
+
 // DB represents a collection of buckets persisted to a file on disk.
 // All data access is performed through transactions which can be obtained through the DB.
 // All the functions on DB will return a ErrDatabaseNotOpen if accessed before Open() is called.
@@ -39,6 +46,9 @@ type DB struct {
 	// a system failure or database corruption. Do not set this flag for
 	// normal use.
 	//
+	// If the package global IgnoreNoSync constant is true, this value is
+	// ignored.  See the comment on that constant for more details.
+	//
 	// THIS IS UNSAFE. PLEASE USE WITH CAUTION.
 	NoSync bool
 
@@ -263,7 +273,7 @@ func (db *DB) init() error {
 	if _, err := db.ops.writeAt(buf, 0); err != nil {
 		return err
 	}
-	if err := fdatasync(db.file); err != nil {
+	if err := fdatasync(db); err != nil {
 		return err
 	}
 

tx.go

@@ -425,8 +425,8 @@ func (tx *Tx) write() error {
 		// Update statistics.
 		tx.stats.Write++
 	}
-	if !tx.db.NoSync {
+	if !tx.db.NoSync || IgnoreNoSync {
-		if err := fdatasync(tx.db.file); err != nil {
+		if err := fdatasync(tx.db); err != nil {
 			return err
 		}
 	}
@@ -448,8 +448,8 @@ func (tx *Tx) writeMeta() error {
 	if _, err := tx.db.ops.writeAt(buf, int64(p.id)*int64(tx.db.pageSize)); err != nil {
 		return err
 	}
-	if !tx.db.NoSync {
+	if !tx.db.NoSync || IgnoreNoSync {
-		if err := fdatasync(tx.db.file); err != nil {
+		if err := fdatasync(tx.db); err != nil {
 			return err
 		}
 	}