block: add secure discard

Secure discard is the same as discard except that all copies of the
discarded sectors (perhaps created by garbage collection) must also be
erased.

Signed-off-by: Adrian Hunter <[email protected]>
Acked-by: Jens Axboe <[email protected]>
Cc: Kyungmin Park <[email protected]>
Cc: Madhusudhan Chikkature <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: Ben Gardiner <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
diff --git a/block/compat_ioctl.c b/block/compat_ioctl.c
index d530856..119f07b 100644
--- a/block/compat_ioctl.c
+++ b/block/compat_ioctl.c
@@ -703,6 +703,7 @@
 	case BLKFLSBUF:
 	case BLKROSET:
 	case BLKDISCARD:
+	case BLKSECDISCARD:
 	/*
 	 * the ones below are implemented in blkdev_locked_ioctl,
 	 * but we call blkdev_ioctl, which gets the lock for us