fat: device-level-flush-after-sync

    This patch forces a device-level flush after the generic Linux
    code for sync has run.

    The kernel depends upon filesystem-specific code to flush when
    the filesystem itself thinks it is necessary, and otherwise
    does nothing.  Someone expecting sync to behave as expected
    might be in for a rude surprise.

    The usual caveats apply:  Devices that do not implement flush
    or whose implementation is buggy will not behave well.  IO
    that occurs after the sync will not be flushed.

Signed-off-by: Ken Kofman <gianfranco.dutka@arista.com>

fs/fat/inode.c

@@ -823,6 +823,14 @@ static int fat_remount(struct super_block *sb, int *flags, char *data)
 	return 0;
 }
 
+static int fat_sync_fs(struct super_block *sb, int wait)
+{
+	if (wait)
+		return blkdev_issue_flush(sb->s_bdev, GFP_KERNEL, NULL);
+	else
+		return 0;
+}
+
 static int fat_statfs(struct dentry *dentry, struct kstatfs *buf)
 {
 	struct super_block *sb = dentry->d_sb;
@@ -937,6 +945,7 @@ static const struct super_operations fat_sops = {
 	.put_super	= fat_put_super,
 	.statfs		= fat_statfs,
 	.remount_fs	= fat_remount,
+	.sync_fs        = fat_sync_fs,
 
 	.show_options	= fat_show_options,
 };