Call fdatasync/fsync after writing out non-meta pages

This avoids a case where writes can be reordered so meta page is
written before a page it refers to, potentially causing a corrupt
database after a power loss or kernel crash.

3 files changed, 23 insertions, 0 deletions

diff --git a/sync_linux.go b/sync_linux.go
new file mode 100644
index 0000000..351b65a
--- /dev/null
+++ b/sync_linux.go
@@ -0,0 +1,10 @@
+package bolt
+
+import (
+	"os"
+	"syscall"
+)
+
+func fdatasync(f *os.File) error {
+	return syscall.Fdatasync(int(f.Fd()))
+}
diff --git a/sync_std.go b/sync_std.go
new file mode 100644
index 0000000..d858b23
--- /dev/null
+++ b/sync_std.go
@@ -0,0 +1,10 @@
+// +build !linux
+
+package bolt
+
+import "os"
+
+// Fall back to syncing metadata too.
+func fdatasync(f *os.File) error {
+	return f.Sync()
+}
diff --git a/tx.go b/tx.go
index 5b2b14d..181444e 100644
--- a/tx.go
+++ b/tx.go
@@ -329,6 +329,9 @@ func (t *Tx) write() error {
 			return err
 		}
 	}
+	if err := fdatasync(t.db.file); err != nil {
+		return err
+	}
 
 	// Clear out page cache.
 	t.pages = make(map[pgid]*page)