DM: Add write sync in fwrite

An immediate reset or power down will cause a loss of write content.
The cause is the data write to disk is at cache within a short
time window before it's synced to storage media.
An explicit fsync() forces to sync the data to storage to prevent
the data loss of such immediate reset.

Signed-off-by: Huang Yang <yang.huang@intel.com>
Signed-off-by: duminx <minx.du@intel.com>
Acked-by: Eddie Dong <eddie.dong@intel.com>

devicemodel/hw/platform/rpmb/rpmb_sim.c

@@ -29,6 +29,7 @@
 #include <stdio.h>
 #include <string.h>
 #include <inttypes.h>
+#include <unistd.h>
 #include <openssl/hmac.h>
 #include <openssl/opensslv.h>
 
@@ -168,10 +169,17 @@ static int file_write(FILE *fp, const void *buf, size_t size, off_t offset)
 		return -1;
 	}
 
+	/* The flow of file writing sync should be:
+	   C lib caches--->fflush--->disk caches--->fsync--->disk */
 	if (fflush(fp) < 0) {
 		return -1;
 	}
 
+	if (fsync(fileno(fp)) < 0) {
+		DPRINTF(("%s: fsync failed\n", __func__));
+		return -1;
+	}
+
 	return rc;
 }